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Available online:May 25, 2020 DOI: 10.7500/AEPS20200101002
Abstract:In view of the lack of secondary devices anti-misoperation in intelligent power grid "control integration" operation mode, the anti-misoperation technology for secondary devices based on master and substation cooperation is proposed and implemented. By extending the anti-misoperation information of secondary devices application service data unit(ASDU) in IEC104 communication protocol, the integration of regulation and anti-misoperation graph model is established, and the maintenance of anti-misoperation information source and the mutual check of logic consistency of the main substation are realized. The anti-misoperation rules of secondary devices are systematically put forward. The anti-misoperation logic between primary devices and secondary devices, secondary devices and secondary devices, station and station is established, and the algorithm of secondary devices anti-misoperation based on expert knowledge base is designed，which realizing anti-misoperation locking function of primary and secondary devices remote operation. The reality practice shows that the anti-misoperation technology for secondary devices improves the devices state perception ability and remote operation anti-misoperation risk control ability. It also ensures the safety of remote operation of power grid. This work is supported by science and technology project of the headquarters of state grid company (No. 521304170028).
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ZHU Dapeng, SU Jianhui, WANG Haining, ZHANG Jian
Available online:May 25, 2020 DOI: 10.7500/AEPS20191225006
Abstract:The power generation unit of megawatt-level photovoltaic power plant is usually composed of two 500 kW grid-connected inverters and one 1 MVA three-phase radial double-split boost transformer. There is a large distributed capacitance between the low-voltage windings of radial boost transformer. It is often difficult for two grid-connected photovoltaic inverters to operate together. Regarding the issue above, this paper establishes the equivalent model of photovoltaic power generation unit with radial boost transformer, and analyzes the influence mechanism of distributed capacitance between low-voltage windings of transformers on the common operation of dual inverters. The analysis result shows that: there is a leakage current loop between the two inverters connected in parallel on the two low-voltage sides of the transformer; increased DC bus voltage of delayed grid-connected inverters in photovoltaic power generation units makes it difficult for dual inverters to operate together. Simulation verifies the correctness of mechanism analysis. Finally, solutions are proposed and verified by simulation and experiment.
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HU Xiao, SHANG Ce, CHENG Haozhong, WANG Li, CHEN Dongwen, LI Yong
Available online:May 25, 2020 DOI: 10.7500/AEPS20191113001
Abstract:Energy flow calculation is the foundation of the analysis and optimization of integrated energy systems, which faces many challenges due to its extensive involvement of couplings of multiple energy forms, such as electricity, gas, heating, and cooling. In this paper, the existing researches are systematically summarized from two aspects: certain energy flow and uncertain energy flow, whose basic theory, mathematical model and solution methods are comprehensively reviewed, as well as advantages and disadvantages are compared. Among them, the certain energy flow calculation is to obtain the operating state of the system under a certain working condition, further divided into two categories, steady-state flow and dynamic flow; the uncertain energy flow calculation is to obtain the operating state distribution of the system under the influence of uncertainties, further divided into three categories, probabilistic energy flow, interval energy flow and fuzzy energy flow. Finally, the research direction of energy flow calculation is prospected according to the requirements upon the development of integrated energy systems.
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Available online:May 25, 2020 DOI: 10.7500/AEPS20190916001
Abstract:Aiming at the assumption that the traditional correlation matrix method needs to obey the normal distribution when generating correlation wind speed, this paper introduces a mixed half-cloud model of wind speed to improve the sampling process of wind speed. Monte Carlo sampling is used to generate correlated wind speed samples, and the comparison between historical wind speed and model results shows that the correlation coefficient between the wind speeds generated by the proposed improved correlation matrix method is closer to the real data. Different correlation coefficients are selected to analyze the wind farm output and grid connection reliability. The results show that the correlation coefficient has a great impact on the wind farm output and reliability. In order to obtain more accurate analysis results on output and reliability evaluation, it is necessary to consider wind speed correlation.
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ZHU Lan, JI Xingyu, TANG Longjun, YANG Qiulin, NIU Peiyuan
Available online:May 25, 2020 DOI: 10.7500/AEPS20190926003
Abstract:Uncertainty of interruptible users" response can cause power companies to face risks such as uncertain scheduling costs and insufficient load reduction, and different users" default risks are diverse. In view of the different probability that the user responds to the scheduling instruction, an insurance contract is introduced on the basis of the basic interruptible contract, and the user is guided to select the policy credit level closest to the true reliability level. Based on the creditworthiness of user policy, the fault probability parameters are defined, the N-x uncertainty set based on user credibility is constructed, and the unit and interruptible load joint scheduling model based on user uncertainty is established. The theory proposed is validated by simulation.The results of the example analysis show that the proposed N-x uncertainty set fully considers the impact of the user"s credibility, and only considers the fault condition with the probability of occurrence higher than the set value. The running result is more realistic.
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CHEN Zhong, YAN Jun, ZHU Zhengguang, TAN Linlin, LU Chen
Available online:May 25, 2020 DOI: 10.7500/AEPS20190725008
Abstract:Multi-infeed AC/DC hybrid system has the characteristics of strong non1inear and strong coupling, and the rapidity of DC adjustment puts forward higher requirements on the determination time of control strategy. For a weak receiving-end system, the transmission capabi1ity of DC subsystem is weak, and the power adjustment range is smal1, when the fast power modulation is implemented ,the system is easily out of bounds. Therefore, the more refined control strategies are needed. In order to control the security characteristic from a macroscopic perspective and realize the fast power fine modulation, the concept of decoup1ing security region is proposed. As for the weak receiving-end system and multi-infeed AC/DC hybrid system with static var compensator (STATCOM), based on the decoupling security region, the power modulation problem is transformed into a 1inear programming prob1em, and the safety control strategy is quickly obtained, so that the purpose of the fast power modulation of the DC system is realized. Finally, the feasibi1ity of the proposed method is verified by case studies.
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LIU Qi, WANG Shouxiang, Ji Xingquan
Available online:May 22, 2020 DOI: 10.7500/AEPS20190509002
Abstract:Due to high penetration of distributed generations, energy storage systems, and responsible loads in active distribution network (ADN), nodal power injections could vary frequently and significantly. Thus, it becomes crucial to assess the influence of power injection variations on key operation characters of ADN, such as nodal voltages, line losses, and branch power flows, accurately and quickly. The traditional sensitivity models can not satisfy the accuracy requirement of ADN analysis when the nodal power injections change greatly. In this paper, branch equation of distribution system is analyzed to derive the complete power flow sensitivity models with wide adaptability, which contain a quadratic sensitivity model of nodal power injections to line losses, a linear sensitivity model of nodal power injections to nodal voltages, a quadratic and a simplified linear sensitivity model of nodal power injections to branch powers. Simulation results of the IEEE33 distribution system and 123-bus distribution system illustrate the accuracy and efficiency of the proposed sensitivity models.
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LENG HUA, QIAN Yulin, ZHU Jiran, TANG Haiguo, ZHANG Weiwei, ZHANG Haiwen
Available online:May 22, 2020 DOI: 10.7500/AEPS20190529007
Abstract:The construction of distribution network automation in various regions is still in a large-scale pilot stage. The method of sensing and locating fault information in many areas is limited, and the outage information comes from multiple systems. Therefore, the need to achieve accurate analysis of outage events under limited conditions is particularly urgent. The actual outage management process of the power utilities is considered and integrated in this paper. An outage information pool is created. Multi-layer data of substations, feeders, distribution transformer areas and customers scattered in transmission lines and distribution lines are analyzed comprehensively. Information credibility profiles are established based on hierarchical analysis. Dempster/Shafer evidence theory algorithm is used to analyze outage events flexibly from multiple dimensions. The method in this paper effectively increases the fault tolerance of fault location, and also enables information sharing and releasing by establishing a reliable structured outage information pool under different conditions.
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YANG Yan, CHENG Xin, JIN Chu, XU Wei, LIN Yong, GAO Chao
Available online:May 22, 2020 DOI: 10.7500/AEPS20190718010
Abstract:Proper system partition is the fundamental measure to deal with the blackouts caused by short circuit exceeding limits, complex failures and AC-DC interaction in multiple DC infeed receiving power system like Guangdong. The existing research focuses on the selection of AC line outage, but system partition often needs to strengthen the grid in the area to meet the electrical support constraints. For this purpose, an optimization method of partition and interconnection is proposed which is able to carry out coordinated optimization for the interconnection schemes within and among sections. With this model, reasonable topology and electrical strength are determined to meet the needs of power flow transmission and DC operation support. Firstly, the objective function is defined as minimizing the probability of blackouts at specified scales, and a mathematic model of network structure optimization is put forward considering system security constraints. Secondly, mathematical expression of network structure is developed based on the definition of the minimum unit of the system, with the interconnection schemes among the minimum units as optimization variables. Finally, harmony search algorithm is used to solve the mathematical model. The effectiveness of the proposed method is verified in the application in Guangdong power system
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Xu Guangda, Zhang Li, Liang Jun, Sun Donglei, Zhao Long, Han Xueshan
Available online:May 22, 2020 DOI: 10.7500/AEPS20191118003
Abstract:Energy Internet construction can realize the state recognition of residential appliances, and provide new data support for the estimation of price elasticity for demand. On this premise, an estimation method of price elasticity for residential electricity demand is proposed based on the electricity consumption features of appliances. Firstly, the correlation between the features and self-elasticity as well as cross-elasticity of residential appliances is analyzed according to the definition of price elasticity for demand. The objective constraint on behaviors of residential price response subjected to adjustability of appliances is revealed. Secondly, considering that the adjustment of appliances is uncertain due to the large number of residents and subjective differentiation of their response willingness, an analysis model based on fuzzy reasoning of electricity consumption adjustment of appliances is constructed?to simulate the price response behavior?of?residents, which takes advantages of the classification sorted by the adjustable features of appliances. Finally, the response results are used to calculate the price elasticity matrix of demand, and the residential price elasticity of electricity demand is estimated. Simulation results show the rationality and effectiveness of the proposed method.
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Lijianlin, Liyaxin, Lyu Chao, Zhaowei, Zhoujinghua
Available online:May 22, 2020 DOI: 10.7500/AEPS20191125006
Abstract:With the advent of the first retirement peak period of electric vehicle power battery, the subsequent treatment of used power battery is posing a serious challenge to the environment and social resources. The energy storage power station is an effective way of echelon use of decommissioned power battery. It is of great practical significance to study the key technology and development status of decommissioned power battery echelon use. In view of the main problems and technical difficulties faced by the echelon use of battery, this question first introduces some echelon energy storage demonstration projects at home and abroad, and summarizes and combs the relevant policies and standards in the current industry. On this basis, the key technologies of battery classification, screening, reorganization, characteristics of the thermal runaway, equalization control and electrode material recovery in the process of echelon use are studied, and the advantages and disadvantages of different methods and control strategies are emphatically analyzed. Finally, combining with the development trend of electric vehicles in China, the commercial application mode of echelon use battery is discussed and prospected.
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ZOU Tonghua, GAO Yunpeng, YI Huijuan, XIA Rui, WU Cong, XU Changbao
Available online:May 22, 2020 DOI: 10.7500/AEPS20191231003
Abstract:An abnormal data processing algorithm based on Thompson tau-quartile method and multi-point interpolation is proposed to solve the problems of long cleaning time and complex model in the processing of wind speed-active power abnormal operation data of traditional wind turbine. Firstly, the abnormal power data points between the cut-in wind speed and the cut-out wind speed that are equal to or less than zero are eliminated. By dividing the wind speed interval, the Thompson tau-quartile method is used to segment and refine the abnormal operation data to reduce the complexity of the model for identifying abnormal points. Then, the cleaned abnormal data are reconstructed by four-point interpolation subdivision algorithm to obtain the complete effective wind speed-active power data. Finally, the actual wind speed-active power data of the wind turbine are used as an example for the comparative analysis. The results show that the proposed method is simpler and the cleaning efficiency is higher. In the case of data missing, abnormal and unavailable in the adjacent wind farm, the proposed reconstruction method can effectively improve the quality of reconstructed data and get better reconstruction results. This work is supported by National Natural Science Foundation of China (No. 51777061) and Guizhou Power Grid Co. Ltd.(No. GZKJXM20171048).
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WAN Wei, YUAN Hui, WANG Guanzhong, XU Luyao, MENG Zhiquan, XIN Huanhai
Available online:May 22, 2020 DOI: 10.7500/AEPS20200109008
Abstract:The converter grid-connected system in a weak grid faces the potential risk of sub-super-synchronous oscillation. The stability criterion based on the generalized impedance considers the coupling effect between grid and the converter in sub-super-synchronous band, and can transform the system stability analysis into a single-input-single-output system. Injecting disturbances in secondary side can not only measure the generalized impedance of the converter, but also has the advantages of low cost and easy operation compared with the measurement by injecting disturbances in primary side. To this end, a method for measuring the generalized impedance of converter in secondary side in super-synchronous band at an arbitrary power factor is proposed. Firstly, we derive the system"s generalized impedance and primary-dual complex circuit considering the perturbation at secondary system. Then, the principle of measurement is explained from the point of view of circuit. Finally, we propose the measuring method of converters" generalized impedance at all power factor in sub-super synchronous band. The proposed method is a generalization of the existing generalized impedance measurement method. Simulation results verify the proposed method.
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YUE Han, SHAO Guanghui, XIA Deming, SUN Mingze, LIU Yang, WANG Kefei
Available online:May 22, 2020 DOI: 10.7500/AEPS20200304004
Abstract:Currently, the overvoltage of UHVDC transmission sending system caused by disturbances such as blocking has become the main constraint to the UHVDC transfer capacity and new energy consumption. Based on the ±800kV Lugu UHVDC weak transmission sending system in combination with the condenser project of Zarut station and the system protection construction of northeast power grid, this thesis puts forward the overvoltage suppressing strategy through coordinating converter station filter (capacitor), condenser, and the synchronous unit near the converter station. On the one hand, during the steady-state of power grid, the condenser and the synchronous unit are fully utilized to compensate the reactive power consumed by the valve group, and reduce the input of filters (capacitors), thus reducing the transient overvoltage caused by the lagging removal of filters (capacitors).On the other hand, the increase of the reactive power of the condenser and the synchronous unit provides sufficient fall-back reactive power reserve for suppressing steady-state overvoltage caused by large-scale power retreat. Finally, the effectiveness of the strategy is verified based on the Lugu UHVDC transmission sending system.
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LAO Huanjing, ZHANG Li, ZHAO Tong, ZOU Liang
Available online:May 21, 2020 DOI: 10.7500/AEPS20200312006
Abstract:This paper proposes a frequency regulation strategy of wind power based on grouping control and staggered recovery for power system with high wind power penetration. Firstly, basing on the response characteristics of proposed scheme with different parameter settings, wind turbines are divided into two groups, laying foundation for the subsequent staggered rotor recovery to mitigate secondary frequency impact. When frequency event occurs, both of the groups raise power to the torque limit to arrest frequency decline. Considering that frequency regulation schemes based on rotor speed or releasable kinetic energy are decoupled from frequency, the proposed scheme regulates wind power with a coefficient designed for suppressing frequency overshoot. The simulation results indicate that by executing rotor speed recovery staggeringly and proceeding the course of regaining MPPT operation by adjusting wind power in a “First repress then raise” way, the proposed scheme smooths the process of frequency regulation effectively without making it to be excessively time-consuming. Meanwhile, the coefficient proposed for suppressing frequency overshoot enhances the adaptability of regulation schemes that are decoupled from frequency after being triggered, towards disturbances of different severities.
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Available online:May 21, 2020 DOI: 10.7500/AEPS20200201003
Abstract:To meet requirements for safe, stable and economic operation of power system under the increasingly complex and changing condition, an on-line identification method of power limit interval of thermal stability section is proposed in this paper. An optimization model for the Conservative Transfer Capability (CTC) and Total Transfer Capability (TTC) of the thermal stability transmission section is established. Based on screening of key thermal stability mode, the Benders decomposition method is used to reduce and decouple the original problem. The cluster computing platform is adopted to improve calculation speed. The proposed method pro-vides technical means for dispatch operators to accurately grasp the system"s security and stability boundaries and dynamically release power transmission capabilities. The analysis of an actual system example verifies the practicability and effectiveness of the proposed method. #$NLKeywords: thermal stability limit; key thermal stability mode; interval of transfer capability; Benders decomposition; nonlinear optimization
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YAN Gangui, LIU Ying, DUAN Shuangming, LI Hongbo, MU Gang, LI Junhui
Available online:May 21, 2020 DOI: 10.7500/AEPS20200116008
Abstract:The large-scale battery energy storage power station is faced with the problem of secondary frequency modulation power distribution among the battery energy storage unit group when it responds to the small power demand of frequent power system secondary frequency modulation, and improper distribution would degrade the operating efficiency of energy storage power stations. This paper analyzes the influence of charge and discharge power of battery energy storage unit on its energy conversion efficiency, constructs the efficiency-charge and discharge power model of battery energy storage unit, and proposes the power distribution strategy of battery energy storage unit group to maximize the overall energy conversion efficiency of energy storage station. This strategy can improve the operating efficiency of the battery energy storage system, reduce power loss, decrease the response quantity of the battery energy storage unit under the scenario of small frequency modulation power demand, and prolong the life of the energy storage station. Compared with the proportional power distribution strategy and the maximum charge/discharge power distribution strategy, the results show that the proposed power distribution strategy has advantages in improving the operating efficiency of battery energy storage system and slowing down the battery life decay.
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Available online:May 21, 2020 DOI: 10.7500/AEPS20200115010
Abstract:Flexible DC distribution network is an important area of the development of power distribution system, which can be built by overhead lines or cables. Considering the fault occurred on overhead lines is mostly temporary, it is necessary for DC distribution networks based on overhead lines to adopt effective reclosing scheme to improve power reliability. In order to realize this purpose, this paper utilizes the different phase characteristics between line terminal voltage and current, and further purposes an adaptive reclosing scheme based on cascaded full-bridge DC circuit breaker, Firstly, generate fault detection voltage at a given frequency by control of the transmission branch of DCCB. Then, distinguish temporary or permanent fault according to the different phase characteristics of DCCB line terminal voltage and current at this frequency. Besides, the influence of some factors like transitional resistance is analyzed. Finally, a model of DC distribution network is built up on PSCAD/EMTDC to verify the feasibility and effectiveness of this adaptive reclosing scheme.
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CHEN Shaoyu, HUANG Wentao, TAI Nengling, YU Fang, ZHU Zhenhong, LI Canbing
Available online:May 21, 2020 DOI: 10.7500/AEPS20200105002
Abstract:DC line protection is the key to ensure the safe and stable operation of the multi-terminal flexible DC distribution system. The main technical difficulty is the accurate identification and rapid isolation of fault section. The distribution characteristics of the transient high-frequency components in DC distribution network after fault are analyzed, and a pilot protection method based on the transient high-frequency power for DC lines is proposed. According to the amplitude change of the high-frequency power before and after the fault, the protection fast start criterion is proposed. According to the difference of linear relationship and correlation coefficient of high-frequency power on both sides of the line under different fault conditions, fault identification and pole selection criterion based on correlation coefficient of high-frequency power on both sides of the line is proposed. In MATLAB/SIMULINK, a multi-terminal flexible DC distribution network model is established. The simulation results show that the proposed protection method can quickly and accurately identify the fault line and fault pole with high sensitivity and reliability. Protection threshold is easy to design and not required for protection coordination of adjacent lines. Moreover, it has low requirements for data synchronization, and has good insusceptibility to fault resistance. Protection method is not affected by system operation mode and network topology.
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ZHANG Qi, SUN Liang, SHEN Jiakai, LI Ping, LI Weidong
Available online:May 21, 2020 DOI: 10.7500/AEPS20191219006
Abstract:With the continuous increase of the proportion of new energy, the strong uncertainty of output power of new energy has brought a lot of problems to the existing formulation method of monthly energy-trade scheduling which uses a decoupled serial method. This paper proposes a time-sequence simulation method for monthly energy-trade scheduling. In this method, the coupled and coordinated optimization method including new energy units and conventional units can fully consider the impact of the power uncertainty of new energy to ensure the accurate implementation of the scheduling. With the full consideration of characteristics of the problem, the four-stage modeling idea (“modeling by stages, the model of former stage is relatively accurate, and the model of later stage is relatively rough”) can ensure the convergence of the calculation and increase the calculation speed, while facilitate the introduction of safe operation constraints. Thus, the four-stage modeling idea lays a good foundation for the formulation of scheduling. The introduction of the Gini coefficient constraint for the rate of power schedule progress on the annual time scale can ensure the balance of the rate of power schedule progress of each power generation entity, to better ensure fairness. The results of the examples verify the feasibility and effectiveness of the proposed method.
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WANG Zhenzhen, SUN Dan, WEN Shufeng
Available online:May 21, 2020 DOI: 10.7500/AEPS20191128005
Abstract:Firstly, the definition and implementation of IEC 61850 control model are studied in conjunction with the standard. The practical application and the definition of the standard are compared and the necessity of testing is explained. Secondly, the control model contents in the second edition of IEC 61850-7-2 and IEC 61850-8-1 are compared with those in the first edition. Then this paper focuses on the analysis of test cases in the second edition of IEC 61850-10, which are quite different from those in the first edition and analyzes the new key points of the test cases. Finally, through the exploration of engineering application, aiming at typical problems, the relevant test requirements and solutions are discussed.
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ZHANG Lizi, CONG Ye, TAO Wenbin, ZHENG Xiayang, YANG Meng
Available online:May 21, 2020 DOI: 10.7500/AEPS20191119003
Abstract:Aiming at the problem that the pricing energy of inter-provincial dedicated transmission projects cannot be calcu-lated by present method, and the present inter-provincial dedicated transmission pricing method may affect the competition efficiency, putting forward the optimization model of inter-regional dedicated transmission two-part price adapting power spot market. Analyzing the problems faced with the price of China’s inter-regional/provincial dedicated transmission projects, elaborating the negative influence by using traditional postage stamp method in the risk allocation of cost recovery, and promoting the efficient competition in electricity spot market. By using power market simulation tools, analyzing the influence of inter-regional transmission price structure and form in the transaction in power spot market. Establishing optimization model of dedicated transmission two-part price based on One-dimensional search and joint economic dispatching model of energy and power reserve, determining the critical point of the two-part transmission price. Combined with the case analysis, proving the effectiveness of the model, ,and analyzing the key factors affect the form and structure of the price.
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XIAO Jucheng, HE Guangyu, XIE Bangpeng, ZHAO Wenkai, ZHANG Siyuan, LIU Feng
Available online:May 21, 2020 DOI: 10.7500/AEPS20191027003
Abstract:With the increasing penetration of renewable energy, the system reserve is seriously of shortage and the security and economy are facing enormous challenges. To solve this problem, the realization method of decentralized transfer of contingency reserve (DTCR) is proposed in this paper, to support the transfer of contingency reserve from supply side to demand side. Firstly, the system design and key technologies of DTCR are given. Then, the millisecond-level appliance-level frequency control method is proposed to support DTCR. The core is the three-stage response strategy, including instantaneous conservative response (ICR), reliable latency response and optimal dynamic control. To balance instantaneity and accuracy of ICR, the local-side zero-communication active response is presented, considering the load priority and power difference. Moreover, to enhance the trial-and-error ability of ICR, the setting formula of conservative response capacity is proposed to avoid frequency from the dangerous threshold and meanwhile minimize the impact caused by mis-shedding. Finally, the effectiveness of the proposed method is verified by the simulation of a modified IEEE 39-bus system. The DTCR scheme is helpful to alleviate the reserve burden and improve the system security.
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ZHOU Peng, ZHANG Xinyan, DI Qiang, YUE Jiahui, XING CHEN
Available online:May 19, 2020 DOI: 10.7500/AEPS20191224010
Abstract:The doubly-fed induction generator（DFIG）wind turbine with virtual synchronous control can improve the inertia and frequency support capacity of the power grid and become one of the effective ways to achieve the friendly grid-connection of renewable energy. When DFIG wind turbine based on virtual synchronous control is directly involved in grid connection, the voltage amplitude and initial phase of DFIG stator may be out of alignment with the grid due to the lack of pre-synchronous phase-locked control. In order to solve the above problems, a virtual synchronous control strategy for DFIG wind turbine without phase-locked loop is proposed. By adding frequency-phase controller and amplitude pre-synchronization controller to the virtual synchronous outer loop control, the stator frequency, phase and voltage amplitude of DFIG wind turbine can be controlled to be the same as that of the power grid, the virtual impedance is introduced into the reactive power-voltage loop to realize the fast and effective smooth grid-connection of DFIG wind turbine. Theoretical analysis and simulation results verify the effectiveness of the without phase-locked loop pre-synchronization control scheme for virtual synchronous DFIG wind turbine.
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HE Chenke, WEI Gang, YUAN Ding, ZHU Lan, LI Yang
Available online:May 19, 2020 DOI: 10.7500/AEPS20190920001
Abstract:This paper establishes an interval load model of electric vehicles, an emergency load support interval model of a charging-swapping-discharging-storage integrated station (CSDSIS), and an interval load emergency support strategy, and an isolated island division strategy for power supply range of interval load for a CSDSIS. Based on the analysis of interval theory, a multi-layer optimization interval model of fault recovery of active distribution network (ADN) is established by taking the isolated island load, switching action times and power loss as the optimization objectives, respectively. Chaotic simulated annealing imperial competition algorithm is proposed to optimize the fault recovery interval model, and an interval Dist-Flow method based on affine number is proposed for power flow calculation. Cases demonstrate that the proposed fault recovery method of ADN taking CSDSIS into account is fast and effective.
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DU Wenlong, YANG Honggeng, MA Xiaoyang
Available online:May 19, 2020 DOI: 10.7500/AEPS20190812007
Abstract:With the condition of asynchronous sampling, if the harmonics and interharmonics in the power grid sampling signal are adjacent ,serious frequency spectrum interference problems will occur. The actual frequency components cannot be identified in the signals. Aiming at the problems, a spectrum separation and measurement algorithm based on fast independent component analysis (FastICA) is proposed to measure harmonic and interharmonic parameters. Firstly, the model of multi-frequency components is built. Spectral lines in the frequency spectrum are represented as a superposition of multiple frequency components. Secondly， frequency component parameters are obtained by using FastICA and least squares method. Finally, the measurement of adjacent multi-frequency components is realized. The simulation result shows that the algorithm can accurately identify the frequency components with a small number of required spectral lines, and has good measurement accuracy and anti-noise ability.
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SHI Rongliang, ZHANG Lieping, WANG Wencheng, ZHANG Xing
Available online:May 14, 2020 DOI: 10.7500/AEPS20191130001
Abstract:The renewable energy sources accessed to the power grid by fast-response power converters has received widespread attention, but they often cause frequency stability problems due to the reduction of power system equivalent inertia. This paper analyzes the effectiveness of two existing solutions: the direct differential operation method using phase-locked loop (PLL) frequency has a slow dynamic response and cause noise amplifications; the frequency differential control method using the second-order generalized integrator based frequency-locked loop (SOGI-FLL) can avoid the frequency differential operation. Nevertheless, the SOGI-FLL has a limited ability in rejecting the grid voltage disturbances. To deal with this problem, this paper proposes a virtual inertia control strategy with the cascaded SOGI-FLL to accurately evaluate the frequency signal. The frequency self-adaptive filter based on SOGI is added to the SOGI-FLL control loop, to enhance the disturbance suppression capabilities. Finally, both simulation and experimental platforms of the microgrid with diesel and energy storage system are established, and the simulation and experimental results verify the effectiveness of the proposed strategy.
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CHEN Xia, XIN Yanli, TANG Wenhu, ZHENG Ming
Available online:May 14, 2020 DOI: 10.7500/AEPS20191024002
Abstract:The construction of offshore wind farms in China has been accelerated with the promotion of wind power parity policy. In the future, large-scale offshore wind farms will become an important power supply for local power grids in coastal areas. When power outages occur in coastal local power grids, if offshore wind farms can act as black-start power sources, the restoration process of power grids will be significantly enhanced. In order to start coastal thermal power units without the black-start capability, a black-start scheme is proposed, which uses small-capacity auxiliary diesel generators equipped in offshore wind farms as supporting power to start offshore wind turbines, and then supplies power to onshore thermal power plants via main transformers and high-voltage submarine cables. In order to improve the frequency regulation ability of the black-start system and maintain the system voltage stability when the high-voltage submarine cable is put into operation, a coordinated frequency modulation control method of wind turbine and diesel generator and a dynamic reactive power compensation control method considering the power limit of diesel generator are proposed, respectively. The latter uses grid-side converters of wind turbine working as the sources of static reactive power. Finally, a black-start model of offshore wind farm is built on PSCAD/EMTDC to verify the feasibility and effectiveness of the proposed operation scheme and control strategy.
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HE Shuaijia, RUAN Hebin, GAO Hongjun, LIU Junyong
Available online:May 14, 2020 DOI: 10.7500/AEPS20191022002
Abstract:The uncertainty factors such as clean energy and electricity price have important influence on the planning and operation of power system. Distributionally robust optimization (DRO) method has been paid more attention since it combines the advantages of stochastic optimization and robust optimization in dealing with uncertainties. Therefore, this paper reviews the application of DRO method in power system. Firstly, the characteristics of DRO method are described and compared with other methods in coping with uncertainties. Secondly, the application status of different types of DRO methods in power system is introduced. Besides, advantages and disadvantages of various DRO methods are analyzed including two classes of probability density, moment information and distributed robust chance constrained method based on these two classes. Finally, the research direction of DRO method in the field of power system is summarized and prospected.
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WEI Mingjie, SHI Fang, ZHANG Hengxu, XU Bingyin, WANG Peng
Available online:May 14, 2020 DOI: 10.7500/AEPS20190801009
Abstract:High impedance grounding fault (HIF) in the distribution network can hardly be detected and cleared by the traditional protection relays due to its weak fault current. The persistent existences of HIF add great risks to the fire hazards and human securities. Aiming at the problems of hard-determined setting threshold and insufficient detection reliability caused by the differences of fault features and noise interference when the existing methods are facing different grounding dielectrics and fault scenarios, a fault detection method is proposed based on interval slope curves of zero sequence current according to the curve analysis of high impedance fault tested in a 10 kV power system site, which uses least squares linear fitting to describe the nonlinear distortion of curves. Meanwhile, Grubbs method is proposed to suppress the interference with interval slopes curves from the irregular waveform distortions and further to guarantee the proper extraction of the fault features. The proposed method possesses great immunity against noise and the reliability is verified by numerical simulation and measured fault data at site.
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ZHANG Jianmin, XIA Yan, NI Linna, HU Yingjun, YANG Sijie, QIU Chengfeng
Available online:May 14, 2020 DOI: 10.7500/AEPS20190627003
Abstract:Situation awareness visualization is a core technology for monitoring and management of low-voltage distribution network (LVDN), therefore, a new concept of transformer centralized low-voltage distribution network (TCDN) is suggested as an object and target to guide corresponding research and engineering application. Auto-generation of a clear and beautiful phase-separated connection diagram becomes a pre-condition for situation awareness visualization. Wiring asymmetry and load asymmetry are core characteristics of LVDN, two types of situation-oriented connection diagrams are designed. A auto-generation principle is proposed for phase-separated connection diagram of TCDN, so that not only the connection symmetry of three-phase four-wire main branches as well as the connected three-phase customers have been promised, but also the connection asymmetry caused by single-phase two-wire customers can be clearly perceptible. For the defined whole phases virtual connection diagram, based on the provided parameters of layout in pan-shape and the arrangement order of each wiring harnesses, the initial layout and routing algorithm for each wiring harness and assembling all of them by in-out zooming and rotating algorithm have been proposed to yield an initial diagram, followed by further beautifying algorithm to generate a nice connection diagram. The generated virtual whole phases connection diagram will be finally disassembled into the phase-separated connection diagrams according to the proposed auto-generation principle. The case study proves the efficiency and affectivity of proposed algorithm, moreover, the time sequence pictures of voltage profile based on the generated phase-separate connection diagram show a very good perceptible understanding of dynamic operation characteristics of TCDN dynamically caused by power outputs from single-phase household photovoltaics and power assumptions from single-phase and three-phase load changes.
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SUN Lixia, BAI Jingtao, ZHOU Zhaoyu, ZHAO Chenyun
Available online:May 13, 2020 DOI: 10.7500/AEPS20191225003
Abstract:In order to further improve the accuracy of transient stability assessment (TSA), a TSA model based on the bi-directional long-short-term memory (Bi-LSTM) network is established according to the sequential characteristics of data in the power system transient process. This method uses the Bi-LSTM network to establish a non-linear mapping relationship between the underlying measurement data and the transient stability category of power system. The performance of Bi-LSTM network model is evaluated by accuracy, F1-measure (F1) index and false positive rate (FPR). On this basis, the t-distribution stochastic neighbor embedding (t-SNE) dimension-reduction method and k-nearest neighbor (KNN) classifier are used to further improve the accuracy of TSA. The example based on the New England 10-generator 39-bus system show that the proposed method has better performance than conventional machine learning models and some deep learning models. The assessment model is analyzed by visualization methods and network prediction scores. The result shows that the Bi-LSTM network has a strong ability to extract the characteristics of power system transient process, which is suitable for the TSA of power system. Further, the influence of the normalization mode and method of the underlying input data on the TSA model is studies. The result show that z-score normalization method is better than min-max normalization method, and the assessment performance of the model using the total dimension normalization mode is better.
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CHEN Wei, YE Yunming, ZHOU Baorong, YANG Jian, WANG Juanjuan, FU Chuang
Available online:May 13, 2020 DOI: 10.7500/AEPS20191025007
Abstract:The constant voltage control and the predictive constant extinction angle control are two conventional control methods for high voltage direct current (HVDC) inverter station. The small-signal stability of AC/DC system can be improved by setting the controller parameters reasonably. Firstly, the small-signal dynamic model of LCC-HVDC based on the switching function method is established, and the correctness of the dynamic model is verified by the comparison of dynamic response between the small-signal model and the electromagnetic transient model. Secondly, based on the eigenvalue and its sensitivity analysis method, the oscillation modes and damping characteristics of LCC-HVDC system are analyzed. When the inverter side adopts constant voltage control and predictive constant extinction angle control, the similarities and differences of the influence of the controller parameters of converter station and short circuit ratio of AC system on the system stability are compared and analyzed. Finally, the stability region of control parameters which can maintain the stable operation of system is calculated, and the correctness of the stability region is verified by PSCAD/EMTDC simulation.
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JIN Weichao, HAN Chang, YANG Li, LIN Zhenzhi, GAO Qiang, YING Guode
Available online:May 13, 2020 DOI: 10.7500/AEPS20191015009
Abstract:Constructing anti-disaster backbone power grids and differentially strengthening them can guarantee the power grid security and power supply for important loads in extreme disaster. This paper proposes a multi-objective optimization model of backbone power grid considering multi-stage disaster resistance. In this model, the topology and operation importance of nodes and lines in the power grid are evaluated quantitatively, and a comprehensive evaluation method based on kernel principal component analysis (KPCA) is proposed. Then, the anti-disaster backbone power grid is optimized for maximizing the survivability, invulnerability and restorability of the power grids with investment constraints satisfied. The graph repair strategy and the files learning strategy are embedded in the improved comprehensive learning particle swarm optimization (ICLPSO) algorithm for solving the optimization model, which expands the feasible solution space. Finally, the effectiveness of the proposed model is verified by the simulation results of a regional power grid.
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LONG Xuemei, YANG Jun, WU Fuzhang, ZHAN Xiangpeng, LIN Yangjia, XU Jian
Available online:May 13, 2020 DOI: 10.7500/AEPS20191011008
Abstract:In this paper, a framework of EV (electric vehicle) charging load forecasting is proposed, which considers user psychology and information interaction of road network and power network. Firstly, the destination of electric vehicle is obtained by travel chain and OD matrix. Secondly, considering driving time, queuing time and charging price, a model of choosing charging station based on Regret Theory is proposed. Thirdly, based on the car following model, the micro traffic analysis of vehicle driving process in the road network is carried out. And the framework of charging load forecasting considering the interaction of road network and power network driven by charging price is established. Finally, the Monte Carlo method was used to simulate the travel and charging of EVs, so as to predict the time-space distribution of charging load of EVs. Through the simulation on Beijing Third Ring Road Network and the corresponding power grid, the effectiveness of the proposed EV charging load prediction framework is verified. The results also showed that the road network and power grid through charging price make the charging load distribution of electric private cars and taxis significantly different in time and space.
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XUE Yusheng, HUANG Jie, WANG Fang, ZHANG Cuiyun, QIAN Feng
Available online:May 13, 2020 DOI: 10.7500/AEPS20191008004
Abstract:To achieve zero net emissions as soon as possible and actively mitigate climate change, it is necessary to make more revolutionary breakthroughs in both carbon emission reduction and carbon sink expansion. Climate change mitigation requires a variety of emission reduction measures, but those different measures may have large differences in both cost and effectiveness. Existing carbon markets have provided different commodities and incentives for different emission reduction behaviors. However, unified analysis frameworks and decision support methods are too scarce to answer questions like ‘how to achieve differentiated incentives’, ‘how to coordinate the trading between different commodities’. This paper re-examines carbon market regulatory mechanism design from the perspective of Cyber-Physical-Social Systems in Energy. Based on a detailed analysis of the multiple attributes and interaction mechanisms of carbon emission reduction behaviors, the interaction logics between different commodities in the carbon market are re-designed: Each commodity market is regulated according to its respective market rules. Different commodity markets are coordinated by multiple equivalents. Special attention are paid to the multiple benefits of carbon emission reduction and carbon offset behavior, enabling regulators to put differentiated preferences on different behaviors, and avoiding market shocks and disturbance caused by rigid market links, discrete regulation and multi-end regulation. Sandbox derivation based on hybrid simulation can be utilized to provide decision support for market design regulation.
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PENG Yuanquan, MAI Zhiyuan, AI Wei, LI Mingqi, YAN Hanting, DONG Jie
Available online:May 13, 2020 DOI: 10.7500/AEPS20190807002
Abstract:The multi-terminal flexible distribution switch (FDS) is used as a device for dynamic power regulation, which is beneficial to the operation optimization of the active distribution network (ADN). Based on the topology of distribution network with FDS access and the mathematical model of three-terminal FDS, a dynamic optimization model for active and reactive power coordination of distribution network with FDS is established: constructing a multi-time scale active and reactive scheduling architecture to optimize the objective function of network loss and voltage, and consider the operating constraints that take system security and cross-section action constraints into account. In order to improve the solution efficiency and relaxation precision of multi-section tidal model, an optimization method for second-order cone programming and nonlinear programming is proposed, and the test results are obtained by using SCIP and other algorithm packages. Finally, based on the actual engineering data, the simulation test is carried out in the distribution network system with three-terminal FDS. The results showed the positive effects of FDS on power quality improvement, operation strategy optimization and intelligent distribution of power flow in ADN, and verified the stability and computational efficiency of the proposed method.
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OUYANG Jin-Xin, zhangzhen, xiaochao
Available online:May 13, 2020 DOI: 10.7500/AEPS20190613007
Abstract:Line commutated converter based high voltage direct current (LCC-HVDC) is prone to commutation failure under AC grid fault, which has a great impact on the safe and stable operation of power system. Commutation Failure Prevention Control (CFPREV) based on AC voltage drop rapid detection is the main means to avoid the first commutation failure. Due to commutation failure is related to voltage sag, fault initial time, DC current and advanced angle, it is easy to cause misjudgement of CFPREV based on fixed control parameters, which further deteriorates the recovery process of power grid. In this paper, the critical commutation voltage of first commutation failure resulted by the AC grid fault is deduced considering the influence of fault initial time, dynamic change of DC current and response of extinction angle controller. Then, the selection method of advanced angle is established by quantifying the commutation margin demand of commutation valve under different fault severity. An improved strategy of CFPREV for HVDC transmission system is proposed, which can enhance the immune ability of HVDC against first commutation failure to the greatest extent and reduce the probability of HVDC commutation failure.
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YANG Jinggang, LIU Yang, LIU Ruihuang, YUAN Yubo, MA Dajun, CHEN Wu
Available online:May 11, 2020 DOI: 10.7500/AEPS20191108001
Abstract:The medium voltage direct current (MVDC) port is essential to power electronic transformer (PET) applied for DC distribution. The available PET topologies based on modular multilevel converter (MMC) can simultaneously provide medium voltage alternating current (MVAC), MVDC, low voltage direct current (LVDC) and low voltage alternating current (LVAC) ports. However, the PET topologies have four power conversion stages, which lead to the complex circuit structure, large volume and weight of PETs. A multi-port PET topology based on MMC with resonant circuit is proposed in this paper. With a mixed-frequency modulation strategy, a set of LC resonant branches, medium-frequency transformers and full-bridge circuits are connected in parallel in the MMC bridge arm branch to realize the power decoupling output of the MVDC and LVDC ports. The proposed PET topology can provide the essential multi-port characteristics only with three power conversion stages with the advantages of the simplified circuit structure, smaller size and weight. Moreover, the equivalent circuit analysis, control strategies and parameter design process of the proposed PET are presented in this paper. Finally, the simulation and experimental results verify that the proposed PET is feasible.
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ZHAO Jinquan, TANG Jianjun, WU Di, TANG Wei, YANG Cheng, HU Xiaofei
Available online:May 11, 2020 DOI: 10.7500/AEPS20191019002
Abstract:In order to deal with the transient voltage and transient frequency stability problems of the multi-infeed high-voltage direct current (HVDC) receiving-end power grid when HVDC lines are blocked, an emergency coordination control strategy considering HVDC power emergency lifting, synchronous condenser emergency control and load shedding is proposed. Firstly, the transient voltage and frequency stability margin index based on multiple two-element notations is adopted. The impact of HVDC power emergency lifting and synchronous condenser emergency control on transient voltage stability of the receiving-end power grid is analyzed, and an emergency coordination control scheme with multiple control means is proposed. Secondly, based on the proposed scheme, an optimization model is established for the emergency coordination control of receiving-end power grid with multiple control means, which considers both transient voltage and transient frequency stability constraints and aims at minimizing the control cost. Then, the sensitivity is used to linearize the model, where the negative impact of HVDC power emergency lifting on transient voltage stability is considered. Moreover, the model is solved by the successive linear programming method. Finally, results of a real example in East China power grid show that the proposed control strategy is effective.
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Song Junying, CuiYiwei, LiXinran, ZhongWei, ZhouXin, Li Peiqiang
Available online:May 11, 2020 DOI: 10.7500/AEPS20191016008
Abstract:In order to improve the accuracy of similarity measurement and the clustering quality of clustering algorithms in load modeling, this paper proposed a daily load curve clustering algorithm based on Euclidean distance and dynamic time warping (DTW) by k-means and entropy weight. Firstly, Euclidean distance and dynamic time warping distance are adopted to measure the overall distribution characteristics, local dynamic characteristics and overall dynamic characteristics of the daily load curves; secondly, entropy weight method is introduced to configure the weight coefficients of these three characteristics adaptively; finally, k-means clustering algorithm is used to cluster the daily load curves based on the similarity measurement method proposed in this paper. This paper analyzed the daily load curves of typical consumers in a province. The results of simulation show that the similarity measurement method adopted in the algorithm proposed in this paper is reasonable, and the algorithm has some advantages in clustering quality and robustness, which can truly reflect the power consumption characteristics of consumers in this area and meet the application requirements of online load modeling.
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Available online:May 11, 2020 DOI: 10.7500/AEPS20191014006
Abstract:An optimal control strategy of grid-connected electric vehicles (EVs) considering demand difference is proposed, which considers the different demands of EV users. Firstly, the grid-connected EVs are divided into three subsets, including rigid set, reducible set and flexible set according to the demand differences, and the charging-discharging control model is established, respectively. Then, the behavior model of EV users is constructed to describe the distribution characteristics of the user behavior, and then the planned power demand is formulated. Finally, the rolling horizon optimization strategy for grid-connected EVs is proposed with the objective of minimized deviation between actual power and planned power and power fluctuation. The power increments of EVs in reducible set and flexible set are took as the optimal control variables and solved under the constraints of the charging-discharging control model. Experimental analysis shows that the proposed optimization strategy ensures that the actual power matches the planned power while taking into account the different demands of users. Moreover, it is robust to random dynamic factors in the optimization progress.
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QIN Jinlei, SUN Wenqiang, LI Zheng, ZHU Youchan
Available online:May 08, 2020 DOI: 10.7500/AEPS20191218003
Abstract:Compared with the traditional electricity market, the low barriers to entry of microgrid, strong profit-seeking of individual users and unstable production capacity of distributed power equipment may make the microgrid transactions fall into a crisis of trust. Therefore, a credit consensus mechanism suitable for the microgrid power trading blockchain is proposed. First, common consensus mechanisms and their defects in microgrid application scenarios are analyzed. Meanwhile, the node attributes of the microgrid energy trading blockchain account are designed, and the microgrid energy trading process based on the blockchain is improved. Then, the credit value evaluation mechanism is established for the microgrid node, and the open and fair evaluation of node credit value is completed. Finally, the consensus mechanism based on proof of credit and stake (PoCS) is proposed, which implements that credit value affects the consensus process and economy factor encourages user nodes to maintain their credit values. The simulation results show that the proposed credit consensus mechanism suitable for microgrid power trading blockchain and the smart contract for microgrid power trading can stimulate high-credit nodes with economic benefits and restrain the dishonesty phenomenon of nodes in microgrid.
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HUANG Liping, WANG Yifei, GUO Juntao, XU Genli, DI Fangtao
Available online:May 08, 2020 DOI: 10.7500/AEPS20190923003
Abstract:The increasing occurring frequency of extreme metrological disasters is posing a great threat to the safe and stable operation of power grid. The traditional power system economic dispatch method aims at pursuing the economics of the generation costs, while ignoring the load distribution condition of power grid. The outage of heavy or full loading lines will lead to the cascading failure and blackout of power system. To solve this problem, a blackout-prevention economic dispatch method considering load rate homogeneity of power grid and N-1 security constraints is proposed for severer whether conditions. Based on the traditional economic dispatching model, and considering comprehensively the load rate distribution of the whole power grid and the transmission lines affected by extreme weather, the load rate distribution balance is improved by reducing the average absolute deviation of the load rate of the entire power grid and the load rate of transmission lines in severer weather areas, the operation security of power system is consequently enhanced. To ensure the robustness and high solving efficiency of the model in severer weather, a novel method for dynamically checking and adding N-1 security constraints of transmission lines is proposed based on a check-feed-back-check idea and the outage distribution factor (LODF) of transmission lines. Finally, a reliability evaluation method for power system dispatching strategies in typhoon disaster is proposed based on the existing cascading failure simulation model considering hidden failures. Simulation results of IEEE RTS-79 test system show that compared with the traditional economic dispatch method, the proposed dispatching method can effectively increase the load rate homogeneity of power grid, and improve the blackout distribution of the power system under severer whether condition, thus improving the system operation safety and reliability
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LIU Yang, YAN Faqi, WANG Yang, XIA Tian, DONG Xiangming, CHEN Wenzhe, ZHANG Mujie
Available online:May 08, 2020 DOI: 10.7500/AEPS20190921006
Abstract:To solve the problem that off-line section and limit can"t well match the system running state, a set of algorithms are proposed for searching and limit setting of transmission section components. Flow transferring amounts of three types of faults, i.e., branch breaking, active component tripping and bus tripping are calculated by DC method, and a method of transforming bus tripping into breaking several virtual short lines is proposed to make the power flow transferring relationship explicit. General linear expressions for three power flow transferring types are concluded, which lays a foundation for setting section limits. The thermal stability section searching method based on "risk branch line+threatening component" constitutional law is demonstrated. By using the general expressions of power flow transferring, a risk-weighted monitoring index construction method and a limit setting method for sections are proposed. The merging method is given for the similar sections consisting of parallel branches, and the simplification method of monitoring index is given for the sections composed of parallel branches. To ensure the solving speed and accuracy, the calculation strategy by combining DC searching method with AC correction method is adopted. Based on an actual example, the searched sections by the proposed algorithm cover all the thermal stability risks of the off-line sections, furthermore, the consistency of section limits between the proposed algorithm and the off-line calculation is proved, and thus the validity of the proposed algorithm is testified. A round of calculation consumes about 3.6 minutes, which meets the requirements of on-line application.
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YAN Xiangwu, CUI Sen, SONG Zijun, SUN Xuewei, SUN Ying
Available online:April 30, 2020 DOI: 10.7500/AEPS20200120001
Abstract:Under the maximum power point tracking control of the doubly-fed induction generator (DFIG), the output power of DFIG is difficult to respond to grid frequency fluctuations. While, conventional overspeed load shedding control can retain active power reserve to participate in system frequency adjustment, which has the problems such as reduced power generation efficiency, small speed adjustment range and frequent start of pitch angle control. To this end, combined with the control characteristics of the grid-side converter of DFIG, this paper proposes a strategy of DFIG inertia and primary frequency regulation based on supercapacitor energy storage control. Both the virtual inertia adjustment and the primary frequency adjustment are realized by supercapacitor control and there is no need to change or increase the additional control of the wind turbines, which improves the disturbance resistance and self-stabilizing of the single wind turbine. According to the actual cost of the supercapacitor module and charging/discharging efficiency, the capacity of the energy storage unit is optimized. By comparing and evaluating the economics of the primary frequency modulation scheme of active power reserve, the proposed scheme has strong economic advantages. Finally, the simulation experiments show that its inertia support, primary frequency adjustment capability and power generation efficiency are significantly improved compared to conventional primary frequency control.
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YANG Li, SUN Yuanzhang, XU Jian, LIAO Siyang, PENG Liuyang
Available online:April 30, 2020 DOI: 10.7500/AEPS20190706006
Abstract:Large scale of wind power connected to the gird brings new uncertainties which affects the frequency response characteristics of the system, from the perspective of data driving, an online reinforcement learning method based on adaptive dynamic model for load frequency control is proposed. A low rank autoencoder feature extraction network is established to discover hidden features from the measured low-dimensional data. Based on the feature network, a nonlinear dynamic system sparse identification learning model is established to sense the potential physical state of the dynamic model of the system and improve the data efficiency of online learning. By combining model predictive control, real-time decision control is implemented, which solves the problem of traditional MPC’s dependence on the accuracy of the system global model, enhance the controller’s adaptability to the system dynamic model and effectively track the random fluctuation of wind power. Finally, the validity of the proposed control method is illustrated by load frequency control model integrated type VI wind turbine.
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YU Kun, ZOU Hao, ZENG Xiangjun, LIU Yuling, LIU Feng, CHEN Xiaoping
Available online:April 30, 2020 DOI: 10.7500/AEPS20190523001
Abstract:In order to solve the measurement error problem of measuring insulation parameters to ground for resonance grounding distribution network caused by the leakage impedance of voltage transformer and damping resistance of branch for neutral point to ground, a novel dual-terminal resonance measurement method of insulation parameters to ground for resonance grounding distribution network is proposed. This method utilizes dual voltage transformer. A characteristic constant current signal with variable frequency is injected into distribution network through the internal voltage transformer of the arc-suppression coil or zero-sequence voltage transformer while the returned characteristic-frequency voltage signal is measured by another. After the equivalent transformation of zero-sequence resonant circuit with damping resistance, the system capacitance to ground and leakage conductance can be accurately calculated by correctly searching the resonant frequency of the system. Both the current injection and the voltage measuring unit of the proposed method directly act on the branch of insulation parameters to ground which eliminates the effect of the leakage impedance of voltage transformer and damping resistance and greatly improve the measurement accuracy of insulation parameters to ground. The proposed real-time measurement technology of insulation parameters to ground is simulated, analyzed and verified by field test in PSCAD/EMTDC simulation environment and 10 kV substation. The analysis results show that the proposed method has high measurement accuracy, whose parameters measuring process is safe, fast and easy to operate, and with no impact on the normal power supply of distribution network.
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WANG Beibei, XU Peng, ZHAO Shengnan, CONG Xiaohan, CHEN Hao, GAO Bo, LI Xuesong, JIANG Yu
Available online:April 27, 2020 DOI: 10.7500/AEPS20191016001
Abstract:With the deep construction of smart grid and the rapid development of new technology of the Internet, the future grid will come to the era of ‘Internet plus’, individuals in the system will realize the wide interconnection. The development barriers of integrated services for smart energy under this background will be break, whose service connotation and service forms will be continuously extended. Firstly, the existing unsolved problems of integrated services for smart energy is anlayzed due to technology and data and so on in this paper, the possible service forms of future integrated services for smart energy is discussed based on the widely used terminal equipment and technical features of ‘cloud, huge, things, move, smart’, 5G communication, edge computing with ‘Internet plus’. The typical future application scenarios with three aspects such as integrated service for smart energy in the user side, the distribution side and the energy finance is put forward, and the prospects and thinking of urgent problems which need to be solved during the application is provided.
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Available online:April 27, 2020 DOI: 10.7500/AEPS20190912001
Abstract:The dynamic interaction of the synchronous generators (SGs) and doubly-fed induction generators (DFIGs) changes the oscillation damping capability of the systems. The system state matrix is decided by the parameters of the SGs and the DFIGs, adding the difficulty of deriving the sensitivity of the oscillation modes to the control parameters. For the power systems with the DFIGs, to quantify the control effect of reactive power adjustment to damp the oscillation, the analytical expression of the sensitivity of the damping ratio to the reactive output of the SGs is proposed. By introducing the constraint of the minimum damping ratio, the oscillatory stability constrained optimal power flow (OSC-OPF) model based on reactive power optimization is proposed. According to the Lagrange multiplier of the OSC-OPF, the sensitivity of the system loss to the reactive capacity of the SGs under the stability constraint is proposed. The simulation results show that the proposed model helps reduce the power loss and improve the damping capability of the wind power systems.
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LIU Jinyuan, LV Lin, GAO Hongjun, LIU Junyong, SHI Wenchao, WU Yong
Available online:April 27, 2020 DOI: 10.7500/AEPS20190826001
Abstract:With the development of clean energy, high penetration of distributed generation (DG) and electric vehicle (EV) which have brought lots of impacts on the planning and operation of distribution network, such as a large number of abandoned power, aggravating load peak-valley difference, etc. A bi-level model of planning and operation is established. It takes the DG output correlation and EV demand response into account, to reduce load fluctuation. Firstly, based on the DG probability models, the correlation matrix method is used to produce DG correlation sample. Secondly, it is established a bi-level model of multi-objective planning and operation, and the upper layer considered the collaborative planning of DG and charging pile(CP), while the lower layer considered the operating costs such as load fluctuation, DG power abandonment, etc. The proposed EV charge-discharge price which fluctuated with the load, DG related samples and so on were expressed in a constraint way. Then Voronoi diagram method is used to divide the service scope of charging station. The upper limit of EV response is determined and the two-layer model is transformed. Finally, the CPLEX tool kit is adopted to solve the second order cone model which proposed in this paper, through a "Transportation network-distribution network" associated system to verify the effectiveness of the proposed model and method.
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TU Jingzhe, YI Jun, WANG Chao, PAN Yan, LU Xiaodong, ZHANG Jian
Available online:April 27, 2020 DOI: 10.7500/AEPS20190809002
Abstract:Under the background of centralized access of large-capacity DC systems and high-penetration renewable energy, this paper studies the problem of power angle and voltage interaction instability resulted by the large power disturbance of DC system considering the impact of dynamic characteristics of photovoltaic generator. Firstly, the motion equations of generator rotor and motor load of the two-machine equivalent system are derived in theory. Then, the physical mechanisms of the system instability caused by power angle and voltage interaction after large-power disturbance of DC system are analyzed. Finally, the impacts of different active/reactive power characteristics of photovoltaic generator during low voltage ride-through (LVRT) process on the system stability are studied. The results are verified through the simulation of Changji-Guquan HVDC system. The study results show that the system instability is eventually resulted by the vicious circle between the relative power angle increase of generator and the load-bus voltage drop (i.e. the decrease of motor resistance). And the impact of different active/reactive power characteristics of photovoltaic generator during LVRT process on the system stability should be comprehensively analyzed by theory combined with simulation.
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LENG Yajun, WU Zongyu, ZHAO Wenhui, LI Zhongxue
Available online:April 24, 2020 DOI: 10.7500/AEPS20191005003
Abstract:Bset selection and assessment of black-start schemes plays an important role in fast restoration after a large-area blackout in power system. The entropy method is one of the most popular methods for determining the weights in black-start assessment. The entropy method suffers from a range of problems, such as large deviation of weight distribution, being unable to reflect small changes of the decision matrix, etc. Based on this, a novel weight determination method based on affinity propagation (AP) clustering is proposed, which is applied to evaluate black-start schemes. Firstly, the AP algorithm is used to cluster the black-start schemes with all indices, and the clustering results based on all indices are obtained. Then, each of the indices is deleted one by one, the AP algorithm is used to cluster the black-start schemes, and the clustering results based on the remaining indexes are obtained. Moreover, according to the structure similarity thinking, the similarities between the clustering results based on all indexes and the clustering results based on remaining indexes are calculated, and the weights of indices are determined. The linear weighting method is used to sort all black-start schemes. Finally,Based on the data of Guangdong power system of China, experiments are carried out to investigate the effectiveness of the proposed method in the paper. The results show that the proposed method has high accuracy.
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LIU Jian, ZHANG Zhihua, LI Yunge, RUI Jun
Available online:April 24, 2020 DOI: 10.7500/AEPS20190730008
Abstract:To solve the problem of single-phase grounding fault processing for neutral point non-effectively grounding in distribution network, an automatic processing scheme for single-phase ground faults in distribution network based on fault phase grounding approach is proposed. The automation system consists of a fault-phase grounding arc-extinguishing line selection device in the substation and some fault-phase grounding start-up protection devices arranged in the feeder switches. By adopting the fault-phase grounding method to achieve the reliable arc-extinguishing of single-phase grounding faults, the characteristics of zero-sequence voltage and zero-sequence current changes before and after the fault-phase grounding disconnection are used to achieve the line selection, location and isolation of permanent single-phase grounding fault and power restoration of sound district. By analyzing the change of zero-sequence voltage and zero-sequence current of the system before and after the fault phase grounding disconnection, a single-phase grounding line selection and location criterion based on the fundamental zero-sequence current ratio before and after the fault phase grounding disconnection is constructed. The key technical problems, such as the start-up criterion for single-phase grounding fault processing, the sensing of the fault phase grounding disconnection moment, and the necessity of injecting a resistance to the neutral point before the fault phase grounding disconnection are discussed in detail. Combined with an example, the proposed processing process for single-phase grounding fault is explained and experimental verification is carried out. The results show the feasibility and effectiveness of the proposed method
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Available online:April 24, 2020 DOI: 10.7500/AEPS20190729014
Abstract:Characteristic analysis on short-circuit current for asymmetric bipolar modular multilevel converter based multi-terminal direct current (MMC-MTDC) grid with dedicated metallic return (DMR) is the foundation of its fault type discrimination and fault isolation. The characteristics of short-circuit currents with different faults are similar, which makes them difficult to be distinguished. This paper analyzes the short-circuit current characteristics of asymmetric bipolar MTDC grids. First, the equivalent circuit of the MTDC grid is established, where the converter and overhead line are simplified to RLC series circuit and RL series circuit, respectively. Then, based on this, the short-circuit current characteristics of a single-terminal converter station are analyzed. Finally, the short-circuit current characteristics of the asymmetric bipolar MMC-MTDC grid following various faults are studied by analyzing the discharge circuit of MMCs based on the above short-circuit current characteristics of a single-terminal converter station. Test results on the Zhangbei bipolar MMC-MTDC grid validate the correctness of the characteristic analysis on short-circuit current for MMC-MTDC grids.
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YAO Zilin, ZHANG Liang, ZOU Bin, GU Shenshen
Available online:April 24, 2020 DOI: 10.7500/AEPS20190614002
Abstract:In the deregulated electricity market, the accurate forecasting of electricity price is helpful for all parties to participate in the market operation and management. The increase of clean energy penetration rate brings new challenges to the accuracy of electricity price prediction. By choosing different input characteristic variables and combined with the characteristics of long-short term memory (LSTM) network, the electricity price prediction model for the electricity market with high proportion of wind power is built to predict the electricity price of the electricity market with wind power. The results show that the ratio of wind power to load is the key input parameter of the electricity price prediction in the electricity market with high proportion of wind power. LSTM has the characteristic of time delay memory, so it has better ability to predict the electricity market price in time series. Based on the actual data of DK1 electricity market in the Nordic market, three models are used for the comparative analysis. The results show that the LSTM model with the ratio of wind power to load and considering multi-time information input can greatly improve the prediction accuracy of electricity price duing slack time.
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WANG Jianxun, ZHANG Yi, ZHANG Yan, SHAO Zhenguo, HUANG Yibiao, YANG Chaoyun
Available online:April 24, 2020 DOI: 10.7500/AEPS20191210002
Abstract:The modern industrial park has the characteristics of large power consumption, mach sensitive equipment and high voltage level. In order to mitigate the huge financial losses due to voltage sags, and overcome the shortcomings of single measures, high cost and poor implementation of existing management schemes, a comprehensive prevention and control scheme for voltage sag is proposed to coordinate the application of management measures on the grid and user sides, and optimize the configuration of switching-type and compensation-type management equipment. Firstly, the performance and cost of the same and different types of management equipment on the user side are analyzed, and the cost model of each management equipment is established. Secondly, the reconstruction cost of transmission and distribution lines are modeled separately, and then the annual voltage sag frequency of the park after reconstruction is modeled. Finally, the objective function of the maximum net present value of comprehensive prevention and control scheme is established, and the particle swarm optimization algorithm is used to solve the optimal configuration scheme of management equipment in the park. Through an example analysis of a modern industrial park, it is proved that the scheme can apply various management means comprehensively to improve the net present value of voltage sag management in the park, and has a good feasibility.
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LIAO Kan, DING Zhaohao, SHU Jun, CHEN Jie, ZHAO Jin
Available online:April 22, 2020 DOI: 10.7500/AEPS20191117002
Abstract:With the continuous advancement of the construction of Chinese electricity spot market, the market trading system and the kinds of trading have been becoming increasingly complex. In the future, various types of transactions will be associated, and this will make the market manipulation behaviors of the electricity market increasingly complex and hidden. All types of manipulation behaviors may distort the results of market transactions, affect the market"s effective guidance for the optimal allocation of resources, and then, affect the effectiveness and sustainability of electricity market reforms. These are issues that need to be paid attention to and be supervised tightly during the development of the electricity market. To this goal, the paper specifically analyzes the manipulation behaviors existing in the European and American power markets. By introducing the definition, classification, and principles of manipulation behaviors, The paper summarizes the general laws of manipulation methods and the corresponding market supervision principles in combination with cases. Based on this, combined with the current development situation of Chinese electricity market, this paper puts forward some inspirations and suggestions for the supervision system of Chinese electricity market.
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WANG Jie, XU Chang, HAN Xingxing, XIN Ziyang, XUE Feifei, LI Linmin
Available online:April 22, 2020 DOI: 10.7500/AEPS20191024006
Abstract:For micro-siting optimization of wind farms in the flat terrain, the meta-heuristic algorithms with random quantities are frequently used. These algorithms are hard to achieve a global optimization, and are relatively inefficient. Grids and constraints are usually needed to make a stable solution. To address these problems, this paper proposes an efficient and stable meta-heuristic algorithm for the micro-siting of wind farms in the flat terrain, i.e., wind-turbine wake repellency optimization algorithm. According to the principle of van der Waals force, the concept of wind-turbine wake repulsive force is proposed, which is used to describe the mutual influence between wind turbines with wake effects. The greater the wake effect between two wind turbines, the greater the wind-turbine repulsive force. During the process of optimization, the wind turbine will continuously move in the direction to reduce the wake under the action of the wind-turbine wake repulsive force until the optimal solution is obtained. Simulation results show that the wind-turbine wake repellency optimization algorithm does not need grid constraints, has a high optimization efficiency, and can obtain a certain result moreover, while the optimization results meet the actual engineering requirements.
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WANG Zonghui, CHEN Yu, XU BingYin, SUN Lingyan
Available online:April 22, 2020 DOI: 10.7500/AEPS20190718006
Abstract:Distributed feeder automation （FA） requires real-time topology information of feeder to realize fault location, isolation, and power restoration in non-faulty sections. This paper analyzes the requirements of feeder real-time topology for the application of distributed FA. Based on the modeling method for IEC 61850，new unit topology logic nodes and topology slice nodes are created to express the feeder topology. The topology information configured of the STU and the status information of the current switch device are applied. The real-time topology identification of feeder based on depth-first search is realized to meet the application requirements of distributed FA. The validity of the proposed method is verified through case study.
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LI Lili, WANG Zhicheng, WANG Gang, ZHOU Wenjun, YANG Leyong
Available online:April 22, 2020 DOI: 10.7500/AEPS20190313005
Abstract:A two-stage optimization method for medium- and long-term electricity security check based on security-constrained unit commitment （SCUC） is proposed to quantify and evaluate the security risks that the medium- and long-term electricity plan and trading contract may bring to the operation of power grid, and to solve the problems of locating and adjustment of the restrictive factors in the implementation of the electric quantity contract. In the first stage, the electricity quantity constraints of the power plant are strictly analyzed. In order to minimize the interface power flow over-limit, the optimization model of electricity security check is established to obtain the optimal unit commitment result. In the second stage, the power grid operation constraints are considered and the optimization model of power calibration is established to eliminate the interface over-limit by adjusting the unit commitment schemes. Through coordinating the two-stage optimal dispatching of power balance and power grid security, it is available to acquire the executable conclusion of electricity contract as well as the orientation of causes and adjustment schemes when it is not feasible. The effectiveness and practicability of the method are verified by the analysis of practical system examples.
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WANG Wenjie, YANG Yiping, HANG Lijun, YANG Chenglin, WANG Shitao, CHEN Shenglun
Available online:April 20, 2020 DOI: 10.7500/AEPS20190908004
Abstract:Modular multilevel matrix converter (M3C) as a new topology has many advantages, but it has many control variables and complicated control structure. First, the working principle of M3C system is analyzed, and its mathematical model is established. On this basis, the control strategy for voltage and current output, bridge arm current, bridge arm energy balance, and the voltage balance of bridge arm sub-module capacitor are analyzed and investigated. At the same time, the overall control scheme of voltage and current both at the input and output of AC side of M3C system are given to achieve the stable operation with good dynamic and static characteristics. Finally, M3C system structure simulation model and experimental platform are established, and the control method is simulated and experimentally verified, which prove the reliability and stability of M3C system control strategy.
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CHEN Lu, YANG Yongbiao, XU Qingshan
Available online:April 20, 2020 DOI: 10.7500/AEPS20190829004
Abstract:Coordinated control of load for aggregated air-conditioners (ACs) has been included in the normal operation of power system due to its better characteristics of spatial thermal storage. However, many problems will be brought out such as aggregated power oscillation, unstable response potential and excessive rebound load, when the diversity of load groups is destroyed for the control strategy. To solve this problem, the influence of temperature control on the power and response potential of single and aggregated ACs is analyzed, the time-varying power characteristic model and polymerization method of aggregated ACs are established based on the temperature control. Then, the two-stage coordinated control model of aggregated ACs with time-varying complementary characteristics is proposed based on the framework of time-phase coordinated control to improve the aggregated quality of air-conditioning groups, with the corresponding response and recovery strategies. Finally, Simulations based on 15 000 ACs show the influence of external temperature, temperature strategy and other factors on the aggregated power, meanwhile, the coordinated control strategy of time-phase air-conditioning groups is applied in demand response events. The results verify the efficiency of the proposed method.
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Available online:April 20, 2020 DOI: 10.7500/AEPS20190812005
Abstract:Synthesis load model of power system is one of the most basic and key issues in the field of load modeling. In power system simulation calculations, the load model is directly connected to the high-voltage bus of substation. However, the loads are actually connected to power gird through the high-voltage distribution network, and the existing synthesis load models are not able to reflect these load situations. In this paper, a method of modeling high-voltage distribution network available to load modeling is proposed. By integrating the equivalent model of high-voltage distribution network into the load model, an synthesis load model considering the distribution network structure is developed. The simulation analysis shows that the proposed synthesis load model has a significant improvement in model description ability, adaptation ranges of voltage and other aspects compared with the existing synthesis load models. The two structural forms are similar in the comprehensive performances,but have several slight differences in the parameter stability and the maintenance of load bus voltage.
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SHI Yong, XU Dong, YU Hongru, SU Jianhui
Available online:April 20, 2020 DOI: 10.7500/AEPS20190712002
Abstract:Parameters optimization of secondary voltage and frequency regulation controllers plays a key role in improving voltage and frequency quality in microgrid, especially for a microgrid system which consists of inverters controlled by droop or virtual synchronous generator (VSG) control. In order to complete the process of parameters optimization, the first step is to construct the voltage and frequency response model of microgrid. However, due to the complex structure of the microgrid system, multiple kinds of micro sources, loads and widely-used commercial power supply, the source model is hard to be obtained, which brings about lots of difficulties in microgrid mechanism modeling. To solve the above problem, a model structure of voltage and frequency at point of common coupling (PCC) for microgrid system is established. The transfer function in the model is identified by operation data sampled in the microgrid and system identification algorithm, and the parameters of second voltage and frequency controller in microgrid system is optimized by identified model. The proposed method can model the microgrid without knowing the inter structure of microgrid and source model, and the order of built model is low which is convenient for parameter planning of regulator. Finally, the effectiveness of proposed method is verified by experiments in test platform for microgrid.
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WANG Tengfei, WANG Hui, LENG Yajun, CHEN Bobo, WANG Junjie, ZHAO Wenhui
Available online:April 20, 2020 DOI: 10.7500/AEPS20190426003
Abstract:In order to transfer the benefit risk caused by the uncertainty of renewable energy (RE) contribution, the output power insurance is introduced, and the requirement of renewable energy quota system (RPS) is considered to discuss the optimal trading decision of the electricity market subjects. Aiming at the electricity trading of bundled RE, the optimal benefit model of RE generators and power retailers are established with the conditional value at risk (CVaR), and the optimal trading decision with and without power insurance is solved by backward induction. In addition, according to the RPS requirements and user benefits, trading strategy of non-bundled electricity of RE is designed. The results of the cases show that the introduction of output power insurance can effectively promote the enthusiasm of RE generators to put into production, save the cost of power retailers, reduce the impact of green certificates price fluctuations on the power retailers, and play a strong role in promoting the completion of RPS requirements for power retailers.
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XIAO Jucheng, HE Guangyu, ZHANG Siyuan, WANG Zhihua, CHANG Naichao, LU Qiang
Available online:April 16, 2020 DOI: 10.7500/AEPS20191027004
Abstract:With renewable energy penetration and large capacity DC operation, there is a serious shortage of contingency reserve, which leads to the reduction of unit operation economy. For this reason, the concept of decentralized transfer of contingency reserve (DTCR) is proposed in this paper. DTCR refers to the transfer of partial centralized contingency reserve from the supply side to the demand side for optimal decentralized distribution of contingency reserves in the overall system. Then, aiming at the unit economy in normal operation, the benefit assessment method of DTCR is proposed, as well as reference indicators. The diminishing marginal benefit (DMB) is found as a reference to select a reasonable decentralized reserve capacity. The economic load rate threshold (ELRT) can be used to assess the degree of DTCR benefit, as a reference for starting DTCR scheme. Finally, combined with 5 IEEE standard systems of 14 buses to 300 buses, the benefit size, benefit mechanism, impacting factors and applicable scenarios of DTCR are analyzed, considering wind power generators and demand response. Results indicate that the DTCR system can continuously generate economic benefits in daily dispatching, optimize power flow distribution and reduce network loss. The benefit rate at a single moment can reach 0.34%~12%, and the total benefit in a typical day can reach 2.5% of total generation cost.
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Available online:April 16, 2020 DOI: 10.7500/AEPS20190927009
Abstract:Grid-connected photovoltaic (PV) inverter is a key component in photovoltaic power generation systems. This paper analyzes the one-sidedness and inaccuracy of three evaluation methods (which using European efficiency, CEC efficiency and Chinese efficiency as evaluation indicators ) for the efficiency of grid-connected PV inverters operating in the typical type-Ⅰ irradiation area of China. Then an evaluation model for the efficiency of grid-connected PV inverters is developed. Based on the meteorological data from 2016 to 2017 in Ningxia of China, the key factors affecting the performance of grid-connected PV inverter in the actual operation condition are considered in the model, including the types of PV components, ambient temperature, wind speed, optimal irradiance inclination angle, and sampling interval of two minutes. The evaluation method is suitable for typical type-Ⅰ irradiation area of China, which provides a more reasonable evaluation index for the selection and design of inverters in the construction of photovoltaic power plants in the area in the future. And it also offers a reference to accurately reflect the power output of grid-connected PV inverter in the actual operation condition and evaluate its power generation performance.
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YING You, SUN Yong, YANG Jing, HONG Min
Available online:April 16, 2020 DOI: 10.7500/AEPS20190911006
Abstract:For DFIG wind turbines, the sudden change of the electromagnetic torque during the grid fault ride-through process will cause a large load on the key components, while the related research is insufficient. Firstly, based on the spring-damping-quality modeling method, this paper establishes the Dual-mass model of drive train and nacelle side-side first-order model, and obtains the analytical expressions of the system"s natural resonance frequency and damping coefficient. The theoretical analysis results show that, the grid faults ride-through process may cause torsional vibration of the drive train and the vibration of tower side-side direction. Secondly, this paper establishes a co-simulation model of GH Bladed and Matlab. Based on this model, the effects of symmetrical and asymmetrical grid faults ride-through process on the wind turbines’ load characteristics are studied. The simulation results verify the correctness of the above theoretical analysis. Finally, the load response characteristics of the wind turbine after grid fault elimination are analyzed under different active power recovery control strategies. The research results show that the over fast active power recovery rate will significantly increase the ultimate load and fatigue load of the drive train and the tower. Therefore, the principle of grid fault ride-through control for "mechanically friendly" wind turbines is furtherly obtained.
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Available online:April 16, 2020 DOI: 10.7500/AEPS20190909011
Abstract:The configuration optimization of virtual power plant (VPP) is an important prerequisite for its participation in the optimal dispatching of power grid. Aiming at the difficulty of dynamic aggregation and quantitative evaluation of resources with different characteristics, this paper proposes a multi-level optimal configuration system including flexible adjustable resources, aggregation adjustment characteristics and optimization target modeling. At the level of flexible adjustable resources, the flexible regulation characteristics of different distributed power sources, controllable loads and energy storage are studied. At the level of aggregation adjustment characteristics, the flexibility of various resources is integrated to obtain the external adjustable flexibility of VPP. On the other hand, the randomness model of VPP is obtained by convolving the probability density function of the randomness of various resources. In the optimization target modeling, based on the portfolio theory, this paper establishes a net present value model including construction, operation and maintenance costs of VPP, and the profits of VPP participating in the electric energy and auxiliary service markets . Based on the static optimization configuration, the dynamic effects of key elements are analyzed. By taking an actual power grid in a certain region of China as an example, the correctness and effectiveness of the proposed method are verified.
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SUN Fengzhou, LIU Haitao, CHEN Qing, YU Miao, WEI Wei
Available online:April 16, 2020 DOI: 10.7500/AEPS20190903004
Abstract:In order to deal with the uncertainty of the output power of renewable energy sources (RESs), this paper proposes a robust optimization method for voltage source converter (VSC) droop slopes in AC-DC distribution networks considering fluctuation interval of RESs. The proposed method aims to minimize the network loss under expect scenarios while ensuring the system robust security. The optimization model is solved by the column-and-constraint generation (CCG) algorithm. Besides,
-P and -Q control are proposed in the droop control schemes to guarantee the linear feedback characteristic， therefore the sub-problem could be transformed into a mixed integer second-order cone programming (MI-SOCP) problem. Furthermore, to increase the accuracy of second-order cone relaxation in the sub-problem, a branch loss limit strategy is designed. By solving the maximum branch loss optimal power flow problem, the maximum possible branch loss is pre-identified, and a series of branch current limit constraints are added to the sub-problem to restrain the feasible range of the branch current. Numerical simulations suggest that the proposed optimization method can improve the system security with little extra economic cost, and the proposed branch loss limit strategy can improve the searching ability of the sub-problem for the extreme scenarios. Therefore, the reliability of the optimization results can be enhanced. - 1
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HE Hongjie, ZHANG Ning, DU Ershun, GE Yi, KANG Chongqing
Available online:April 16, 2020 DOI: 10.7500/AEPS20190820005
Abstract:Electrochemical energy storage plays an important role in the power system. Recently, research on large-scale electrochemical energy storage in power grid side participating power system dispatching operation and control has emerged one after another. The energy efficiency and lifespan decay characteristics of electrochemical energy storage are nonlinearly affected by the charge and discharge rate, depth of discharge and operating temperature. These effects are not comprehensively considered in the existing researches. This study introduced the principles and characteristics of three electrochemical energy storage systems for lithium-ion batteries, supercapacitors and all-vanadium flow batteries. This study focused on the classification and analysis of the modeling methods for operating efficiency and lifespan decay of these three electrochemical energy storage systems. Finally, this study proposed the key issues and potential research topics of operating efficiency and lifespan decay modeling methods for the large-scale electrochemical energy storage systems on power grid side.
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LIN Shunfu, YAN Xinyu, DAI Yemin, LI Dongdong, FU Yang
Available online:April 16, 2020 DOI: 10.7500/AEPS20190716004
Abstract:The accurate estimation of the system harmonic impedance is critical to realize the quantitative determination of harmonic responsibility. The customer side harmonic impedance is no longer much greater than that of the system side in the situation of new energy resources connecting to the grid, which results in that the existing estimation methods have low accuracy or become ineffective. This paper proposes an estimation method of system harmonic impedance based on the sub-space decomposition and the dynamic coefficient regression. The observed signals of the harmonic voltage and current at the point of common connection (PCC) are decomposed into several sub-spaces by the wavelet packet decomposition. The sub-space with the weakest correlation between the explanatory variables is selected out according to the mutual information value, which reduces the influence of the correlation between explanatory variables on the regression analysis. Considering that the system side harmonic fluctuation will interfere with the correlation between the harmonic voltage and harmonic current at PCC, the system side harmonic voltage is regarded as a dynamic coefficient. The system harmonic impedance is calculated by the dynamic coefficient regression method, to reduce the influence of harmonic voltage fluctuation on the estimation results. The simulation results show that the proposed method has better estimation accuracy and robustness compared with the existing methods.
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XUE Hua, REN Chunlei, WANG Yufei, QIN Jianan, ZHANG Yuhua
Available online:April 15, 2020 DOI: 10.7500/AEPS20190710005
Abstract:In order to realize voltage smoothing control of the DC microgrid with high proportion of renewable energy, this paper proposes a coordinated control method of multiple DC electric springs (DCESs) based on differential flatness theory. Considering the nonlinear characteristics and multiple working modes of multiple DCESs in the DC microgrid, the differential flatness control method is designed for the upper layer to directly compensate nonlinear components, which ensures stable DC bus voltage under the condition of renewable energy output fluctuation and system parameter perturbation. The stability and robustness of the system are improved, and the reference trajectories of inductor currents are provided for the lower layer. The model predictive control (MPC) method based on the working modes of DCESs is designed for the lower layer. By simplifying the optimization calculation, the rapid dynamic response of the system can be ensured, and the tracking of reference trajectory of inductor current and the voltage fluctuations of various DC bus segments can be achieved without communication. The simulation results based on MATLAB/Simulink and the experimental results based on dSPACE show the correctness and feasibility of the proposed method.
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JIA Ke, ZHU Zhengxuan, ZHAO Qijuan, YANG Zhe, BI Tianshu
Available online:April 13, 2020 DOI: 10.7500/AEPS20191118006
Abstract:The faults of DC distribution network develop rapidly and the frequency components are not fixed, thus the accurate analysis on fault characteristics has important research significance. From the perspective of impedance characteristic analysis in DC fault conditions, the frequency-impedance responses of various DC converters are studied. Based on the analysis of the harmonic path of DC/DC converter and modular multilevel converter (MMC), reasonable equivalence and simplification are carried out according to the component parameter characteristics, and the high-frequency impedance models of the converters are established. The proposed model will not be affected by the inverter control strategy, and can accurately reflect the high-frequency impedance characteristics of various types of converters.
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HU Zesheng, LU Jun, HUANG Rui, LIU Mouhai, XU Zhiqiang, WANG Yun
Available online:April 13, 2020 DOI: 10.7500/AEPS20190712014
Abstract:Longitudinal transition between energy and lateral shift of energy use time have occurred in intelligent energy communities. Aiming at the problem of synergy optimization between them, this paper proposes an energy optimization method considering thermoelectric coupling system of demand response. Based on the analysis of the system structure framework, the energy hub(EH) equation is established between energy supply side and energy load side by load classification and energy response process, which realizes the quantitative description of energy conversion between energy load response and supply. Then, the demand response degree of the load is expressed as the participation ratio of the transformable load and the shiftable load, and the energy optimization model is established with the lowest system operating cost. A model solution method is proposed that it can be figured out by flexible scale multiple demand response participation. The results of the experiment show that the peak of load in supply side and the total system cost can be reduced at the same time with high shiftable load participation ratio and low transformable load participation ratio, achieving the optimal operation of the thermoelectric coupling system.
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WANG Dan, HUANG Deyu, HU Qing’e, JIA Hongjie, ZHANG Niepeng, YANG Zhihong
Available online:April 11, 2020 DOI: 10.7500/AEPS20191220007
Abstract:With the development of integrated energy systems and multi-energy markets, traditional demand response has gradually shifted towards integrated demand response (IDR). In IDR, users can participate in the programs by either changing their energy consumption habits or converting energy sources, thereby realizing the coordination and optimization of supply and demand resources. This paper takes users" demand for electricity and heat in winter as the scenario. First, based on the mechanism model of retail energy market participants, the electricity-heat joint double auction retail energy market framework is constructed. Then, the bidding strategies for electric and heat loads in the joint market are proposed, furtherly the electricity-heat joint market clearing model with the aim of maximizing the surplus of energy producers and consumers is established. Considering the control mode and operating mechanism of different types of loads, the control strategies of electric and heat loads are proposed in response to market clearing signals. Finally, the numerical example is utilized to verify the effects of the proposed method on realizing the coordination and optimization of resources on both sides of supply and demand, promoting the consumption of renewable energy, as well as saving energy for users.
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DU Wei, LUO Xianjue, WANG Xiuli, ZHANG Qiwen, LI Xue
Available online:April 01, 2020 DOI: 10.7500/AEPS20190528010
Abstract:The research shows that the reliability of power system of offshore oilfield group has a significant impact on the oil production. Considering that this kind of power grid is an independent power grid including generation, transmission and distribution systems at the same time, and load shedding measures are different from those of onshore power grid when fault occurs, the traditional reliability evaluation model and algorithm cannot be used directly. A reliability evaluation method is proposed for offshore oilfield power system based on the system-wide reliability evaluation theory and an index system is set up for the system-wide reliability. During the state sampling, the whole power system sampling can be divided into generation and transmission system sampling and distribution system sampling according to the system-wide reliability evaluation theory, and the comprehensive evaluation method can be established. In the state evaluation of generation and transmission system, the load curtailment model based on priority trip is constructed considering the characteristics of offshore power grid and its load equipment. In the state evaluation of distribution system, the effects of cascading failure are taken into consideration. Finally, experiments are conducted on a practical example of a certain offshore oilfield power system. The system-wide indices are obtained and the influences of the four kinds of failure are analyzed to prove the correctness and effectiveness of the proposed method.
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Construction Method of Economic Operation Region in Automatic Cruise for Bulk Power Grid Dispatching
ZHANG Yikang, ZHAO Jinquan, LIU Ziwen, WU Haiwei, WANG Zhicheng
Available online:March 20, 2020 DOI: 10.7500/AEPS20191018003
Abstract:The construction of economic operation region (EOR) is the first step to realize automatic cruise function for bulk power grid dispatching. EOR is defined as the set of all optimal security-constrained day-ahead generation and transmission scheduling with various preferences for scheduling objectives. Then, this paper develops a centralized multi-objective model of day-ahead generation and transmission scheduling for inter-regional interconnected bulk power grid via HVDC tie-line, to minimize power generation cost, carbon emission and pollutant emission. The multi-objective optimization problem is transformed into a series of single-objective optimization problems by using the normal boundary intersection (NBI) method. And a decomposition-coordination model for sending and receiving power grids based on synchronous alternating direction method of multipliers (SADMM) is constructed for each single-objective optimization problem to realize distributed solution. Finally, a uniformly distributed Pareto frontier is obtained, which is the EOR. A two-area interconnected test system via HVDC tie-line modified from IEEE 39-bus system is utilized to verify the effectiveness of this method.
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WANG Hao, YANG Dongsheng, ZHOU Bowen, GAO Xiaoting, PANG Yongheng
Available online:March 18, 2020 DOI: 10.7500/AEPS20191124003
Abstract:In view of the fault characteristics of multi-terminal HVDC (MTDC) transmission lines, such as rapid rising speed， large peak value of fault current and difficulty in fault location, a fault diagnosis method for MTDC system with both rapidity and accuracy is proposed. Firstly, the amplitude and frequency characteristics of fault signal waveforms of MTDC transmission line faults are analyzed. The extraction methods for fault amplitude and frequency features of MTDC transmission line faults are studied separatedly based on amplitude variation characteristics of signal waveforms and wavelet packet analysis.Then, the fault diagnosis method of MTDC transmission system based on amplitude-frequency characteristics is formed. Secondly, the parallel convolutional neural network (P-CNN) with fault classification and fault location branch is constructed, and the training method of P-CNN based on transfer learning is proposed. Finally, the simulation verifies that the fault diagnosis method of MTDC system based on P-CNN meet the fast requirements, and the parallel structure is more accurate and expandable than other artificial intelligence fault diagnosis methods.
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LIU Hao, BI Tianshu, XU Quan, CUI Shijie, SHI Bonian, XUE Ancheng
Available online:March 12, 2020 DOI: 10.7500/AEPS20190814002
Abstract:With the increasing penetration of distributed renewable energies, more and more electronic devices are brought into smart distribution networks. However, the observation problem of distribution network is becoming more severe. Therefore, synchrophasor measurement unit for distribution network (D-PMU) is of great significance. Based on investigating the current status of research at home and abroad, five aspects of synchrophasor measurement of distribution network are introduced including the sychophasor measurement method with high accuracy under high noises and step changes, the synchronization technology with weak commutation, the information security technology, the development, and the testing technology and platform of D-PMU. The research ideas and framework of high-precision synchrophasor measurement technology for distribution network are proposed. Meanwhile, the framework of D-PMU, phasor measurement methods for D-PMU and its calibration are proposed.
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TANG Wei, LI Tianrui, ZHANG Lu, CAI Yongxiang, ZHANG Bo, WANG Zhaoqi
Available online:March 12, 2020 DOI: 10.7500/AEPS20190609004
Abstract:The unbalanced connection of large-scale residential photovoltaic (PV) power integrated into low-voltage distribution network (LVDN) will bring problems such as voltage violations, power losses and three-phase imbalance. In order to solve the problem that the accommodation control technology is not suitable to the three-phase four-wire low-voltage distribution system, a coordinated control method considering PV and energy storage system (ESS) is proposed based on three-phase four-wire optimal power flow (OPF). The network topology of LVDN is established by using three-phase four-wire node admittance, where the amplitudes and phase angles of voltage and current are considered. Multi-period coordinated control model of three-phase four-wire lines for active power of energy storage elements and reactive power of PV inverters is developed by overall considering the minimum of both power loss and three-phase imbalance. The difficulty of solving three-phase four-wire model is reduced through complex variable decomposition and model convexity, and the global optimal solution can be got by CPLEX method package. Simulation results show that the proposed OPF based control method can effectively mitigate the voltage violation in conditions of large-scale PV and load unbalanced connection, meanwhile the network power loss is reduced and the degree of three-phase imbalance is also optimized.
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XU Jian, LIAO Siyang, WEI Congying, YUAN Jiaxin, YANG Jun, JIA Yuqiao, FU Haobo, XIE Boyu, YUAN Zhiyong
Available online:February 26, 2020 DOI: 10.7500/AEPS20190829003
Abstract:With the large-scale access of distributed generators and other power electronic equipment to the distribution network, new requirements are brought to both control flexibility and control time scale. The configuration of distributed phasor measurement unit (D-PMU) opens a new situation for online monitoring and real-time control of the distribution network. Aiming at the new control framework and new control methods formed after the integration of D-PMU data and the distribution network measurement system, research on source-grid-load coordinated control in the distribution network based on wide-area measurement information is summarized. The research mainly includes the power prediction of distributed generators and flexible load modeling under the background of multi-source data fusion, the rapid source-grid-load coordinated control to solve the power fluctuation of new energy and the voltage security problem, and the usage of fast synchronization characteristics of D-PMU data to realize island smoothing switch and stability control, etc. According to the above content, the corresponding technical route is conceived, and the key technical difficulties are prospected. The application of some technologies in the demonstration project is introduced.
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YANG Yulian, QI Linhai, WANG Hong, SU Linping, XU Yonghai
Available online:February 16, 2020 DOI: 10.7500/AEPS20190605007
Abstract:Traditional data missing reconstruction technology mostly relies on mathematical statistics method and prior knowledge combined with mechanism analysis to construct mathematical models. However, measurement data in distribution network has high dimensional, time-varying, non-linear characteristics, high complexity, difficult characterization, and it is difficult to ensure high-precision reconstruction. In this paper, an unsupervised generation antagonism training method is proposed to extract data features independently and reconstruct missing data with dual semantic perception constraints. Among them, the reconstructed model based on two-dimensional convolution and the two-dimensional gray image training of measurement data enhance the generalization ability and stability of the model. This method does not need prior knowledge distribution hypothesis and explicit physical modeling, and can effectively improve the accuracy of reconstructed data while guaranteeing maximum feature extraction. Finally, the validity of this method in reconstructing missing data is verified by the measured data. National Natural Science Foundation of China (No. 51277069) and State Grid Corporation of China (No. 52094018001C).
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CHENG Xin, XU Liang, ZHOU Shucan, LIU Zhengchao, LIN Yong, GONG Xianfu
Available online:February 16, 2020 DOI: 10.7500/AEPS20190717008
Abstract:The integration of large-scale new energy to the power grid makes the uncertainty caused by power supply higher than the uncertainty of load demand. The probabilistic power flow of power system makes the management of operation department even more difficult. To solve this problem, this paper proposes an energy storage configuration method based on trajectory sensitivity analysis based on guaranteed rate of new energy output. Firstly, an over-limit equation of probabilistic power flow for tested components is set up according to the uncertainty of new energy output. Secondly, an analysis model of trajectory sensitivity for probabilistic power flow is built by setting the guaranteed rate of new energy output as a parameter. Thirdly, a configuration strategy of energy storage is proposed to make the probabilistic power flow not exceed limit. In the meanwhile, power and energy requirements of energy storage are calculated for component-related nodes which have low trajectory sensitivities. Finally, the proposed method is simulated and verified on a practical power system in a area of South China.
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Available online:February 07, 2020 DOI: 10.7500/AEPS20190521003
Abstract:A two-level model of station-network cooperative optimization of integrated energy system for park is established. The upper-level model is an improved p-median model, and the decision variables are the location and capacity of energy stations and network layout. Considering the demand response characteristics of electric and heat loads, the lower model coordinates the interruptible load with the energy station supported by the power-heat-gas multi-energy flow. The greedy-variable neighborhood-cobweb (GVNC) algorithm is used to solve the model, which can improve the computational efficiency and obtain the global optimal solution. Second-order cone relaxation (SOCR) is used to transform the non-linear programming problem into a second-order cone programming (SOCP) problem which is easy to solve. Convex-concave procedure （CCP） is used to solve the problem of accuracy recovery after relaxation. The example shows that considering the influence of source-load interaction, the operation cost of the system can be effectively reduced, and the planned capacity of the energy station can be more economical and reasonable.
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Online First
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LIU Dunnan, LIU Mingguang, WANG Wen, PENG Xiaofeng, XU Chang, WANG Jun
2020,44(10):1-9, DOI: 10.7500/AEPS20190813005
Abstract:Charging network is one of the typical scenarios of Energy Internet. The in-depth study of charging network operation mode and key technologies can effectively alleviate the impact of electric vehicle charging load on the power system. Meanwhile, the research can also provide support for promoting large-scale renewable energy consumption. Considering the policy background of renewable energy quota system, the definition and operation framework of charging load aggregator is proposed. On this basis, the driving force of charging load aggregators to participate in the green certificate trading market is analyzed, and then the two-level green certificate trading mode inside and outside the charging load aggregators is constructed. Then, in view of the coupling mechanism of green certificate trading, carbon emission trading and electricity market trading, a multi-market coordination mechanism is established. Finally, according to the green certificate trading mode, through the four dimensions of perception layer, network layer, platform layer and application layer, the concept of green certificate trading system and key technologies for charging load aggregator are put forward. The research results will support the development and construction of charging load aggregating system. This study can also provide a reference for the design and development path construction of Energy Internet business model in China.
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YANG Jingwei, ZHANG Ning, KANG Chongqing
2020,44(10):10-21, DOI: 10.7500/AEPS20200209002
Abstract:The multi-energy networks represented by power, gas and heat networks are one of the most complex physical networks in the world, which are also the key components connecting energy production and consumption, as well as the important way of the coupling of multi-energy systems. Based on the generalized electric circuit model of the branch layer in multi-energy systems, this paper proposes the generalized electric circuit analysis theory for the network layer. Firstly, according to the difficulty of representing the high-dimensional dynamic characteristics of multi-energy networks, a generalized modeling method for multi-energy networks in Laplace domain is proposed based on the generalized electric circuit model at branch layer, and the corresponding compact matrix model is also proposed. Secondly, external-port equivalent method of multi-energy networks is proposed, which can transform the complex internal information into equivalent boundary conditions to simplify the coordinated analysis of multi-energy networks and protect the data privacy of each energy system. Finally, combined with the practical characteristics of the heat network and the gas network, the generalized electric circuit model and the boundary equivalent method are proposed for the whole network with heat network and gas network.
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ZHAO Jinli, CHEN Hao, SONG Guanyu, FAN Xinming, LI Peng, WU Jianzhong
2020,44(10):22-31, DOI: 10.7500/AEPS20190715008
Abstract:Soft open points (SOPs), which have powerful capability of power flow control, can make positive contribution under normal operation and fault conditions of distribution network. The benefits both from the improvement of power supply reliability and operation economy should be taken into account at the planning stage. Planning model of SOPs is proposed in this paper considering the effect of connecting SOP on supply reliability and operation economy in distribution network. The fast-search and the method of finding density peaks clustering are used to aggregate the annual load data, and the typical operation scenarios in distribution network are generated to calculate the improvement cost of operation economy. The calculation method of branch failure rate based on related constraints is adopted, considering the influences of load rate of line current, node voltage and length of line on branch failure rate, the dynamic prediction failure set is generated to calculate the benefits of power supply reliability. A hybrid optimization algorithm, which combines the simulated annealing method with the second-order cone programming, is used to solve the planning model mentioned above. Finally, the effectiveness of the proposed planning model is verified by the modified PG&E 69-node test system. The results show that the SOP planning method facing reliability and economy in distribution network can effectively reduce the comprehensive cost of distribution network and maximize the investment benefits.
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CHEN Boda, LIN Kaidong, SU Jieying, ZHANG Yongjun, YANG Yin
2020,44(10):32-40, DOI: 10.7500/AEPS20190820001
Abstract:Considering the uncertainty of renewable energy and electricity, gas and heat load, this paper discusses the island partition of integrated energy microgrid system and establishes a robust island partition model based on continuous operation of island. This model uses energy conversion and storage equipment of integrated energy microgrid as scheduling resources, and targets to optimize islanding partition scheme after fault occurrence. In this model, the shortest notification time constraint against the blackout is taken as the target penalty term and a certain response time is reserved for the load to some extent. Meanwhile, it avoids repeated access and removal of island load caused by source power and load fluctuation. The robust discrete optimization theory transforms uncertain constraints into certain constraints, and a mixed integer linear programming model is constructed. Global robust tuning coefficient is used to improve the conservativeness of robust optimization. The economy and operability of the islanding scheme are well balanced to meet different decision-making needs. Finally, the case verifies the effectiveness of the proposed model and solutions.
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LIU Wenxia, LI Zhengzhou, YANG Yue, YI Fang, WANG Yao
2020,44(10):41-49, DOI: 10.7500/AEPS20190731013
Abstract:This paper proposes a method of equipment optimal configuration for an integrated energy system (IES) considering the uncertainties of integrated demand response (IDR). Firstly, in order to improve the efficiency of energy use, the basic structure of IES considering IDR is constructed based on a combined cooling, heating and power system. Then, the aleatory and epistemic uncertainty of IDR are analyzed by the evidence theory, and the load curve under a certain price scheme is optimized by using a credible level constraint. On this basis, a bi-level collaborative planning model considering the optimal configuration and operation strategy of the equipment in IES is established. In the upper level, the equipment selection and capacity allocation are conducted with the goal of minimizing the total planning cost. And in the lower level, the equipment output is optimized with the lowest operation cost as the objective. By comparing the total costs of all tariff schemes, the optimal tariff and equipment allocation scheme is obtained. Finally, the proposed approach is illustrated on an example and the results demonstrate that the optimal allocation results considering the uncertainties of IDR are more resistant to risks. Meanwhile, evidence theory can be used to achieve the unification of probability theory and interval theory.
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CHEN Zhe, WANG Luyu, GUO Chuangxin, MA Guang, ZHANG Jinjiang
2020,44(10):50-58, DOI: 10.7500/AEPS20190813001
Abstract:To alleviate the system operation and reserve scheduling pressures caused by multiple levels of uncertainty, a two-stage robust optimization model of multiple reserve resources is proposed, which considers the reserve capacity of wind power and demand response. On one hand, to make full use of the wind farm and demand reserve capacity and improve the flexibility of system operation, the reserve capacity provided by wind farm and demand side is modeled， respectively. On the other hand, based on the robust optimization model, multiple reserve resources are co-optimized to ensure the safe and reliable operation of power grid in the worst operation conditions, thus improving the robustness of power system. The two-stage robust optimization problem is solved by the column and constraint generation (C&CG) algorithm. Simulation results on the modified IEEE RTS-79 test system verify the effectiveness of the proposed model and algorithm. The results show that the co-optimization of multiple reserve resources can improve the operation flexibility of power system and promote wind power consumption. At the same time, by adjusting the uncertainty set of the robust model, the balance between the robustness and economic efficiency of the system can be achieved.
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LIN Guoying, LU Shixiang, GUO Kunjian, GAO Ciwei, FENG Xiaofeng
2020,44(10):59-67, DOI: 10.7500/AEPS20190613004
Abstract:A Stackelberg game model between a power grid corporation and multiple users is constructed for demand response. The power grid corporation selects the appropriate time period to formulate the subsidy strategy of demand response based on the predicted load duration curve of next year. The construction costs of power transmission and distribution are decreased by reducing the peak load, thereby the overall revenue of power transmission and distribution is improved. Users choose the response in electricity consumption based on the subsidy price of demand response during the time period set by the power grid corporation to obtain additional profits. Moreover, the existence of the Stackelberg game model and the idea for solving the model are analyzed, and the process of solving the game equilibrium solution is presented. Case study shows that the power grid corporation can declares subsidized price during peak load period based on the developed model. Both the power grid corporation and users can benefit from demand response. In addition, the impact of the unit cost change of avoidable power transmission and distribution capacity on profits of demand response for the power grid corporation is analyzed.
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WANG Junjie, JIA Yulong, MI Zengqiang, CHEN Hairui, FAN Hui
2020,44(10):68-76, DOI: 10.7500/AEPS20190826007
Abstract:To improve the reserve service capability of electric vehicle (EV), this paper proposes a charging/discharging day-ahead scheduling strategy of EV based on the double-incentive mechanism. Firstly, a user-oriented double-incentive mechanism and market interaction mode considering the discharging mode of EV are designed. Then, a semi-managed user response mode is proposed. In this mode, the uncertainty of user response state is modeled and analyzed. A charging/discharging dispatching model of EV for responding the double-incentive is constructed by stochastic programming method. Based on the above models, the case study compares the reserve service capacities of EV with and without discharging incentive. Furthermore, the impact of some factors, such as charging and discharging incentive prices and dispatching time scale, on the reserve capacity of EV is analyzed through the sensitivity analysis of dispatching parameters.
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PANG Lei, HAN Bei, WANG Keyou, LI Guojie, WANG Chunning
2020,44(10):77-84, DOI: 10.7500/AEPS20190909004
Abstract:Droop coefficients of inverters for distributed generators in AC/DC hybrid microgrid can have great influences on feasibility region of power flow in island operation mode. While traditional droop coefficients are determined by capacity and frequency of inverters and voltage regulation range, which can not give full consideration of the above influence. To fill the gap, a calculation model for power flow of AC/DC hybrid microgrid considering control modes of inverter is firstly established. Then a fast calculation method of feasibility region of power flow in parameter space is proposed, the impact of droop coefficients on feasibility region of power flow is further considered. The optimal values of droop coefficients are suggested by overall considering both load stability margin and small-signal stability factors. Finally, an improved 12-node AC/DC hybrid microgrid is simulated to verify the effectiveness and applicability of the proposed method. Results show that the voltage stability margin is significantly increased compared with traditional methods.
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WANG Zhen, YIN Xianggen, CHEN Yu, LAI Jinmu, SUN Guanqun
2020,44(10):85-91, DOI: 10.7500/AEPS20190811002
Abstract:The arm current control method for modular multilevel converter (MMC) can simultaneously accomplish AC-side current control and circulating current suppression control. Continuous control set-model predictive control (CCS-MPC) is an optimal control method based on system model in time domain. It has fast dynamic response and can accurately track multi-band compound signals. In this paper, an arm current control strategy based on CCS-MPC is presented. The designed model predictive control （MPC） controller can simultaneously realize the accurate tracking of DC component and fundamental-frequency AC component of bridge arm current, and suppress multiple-frequency circulating currents. The interaction problem between different bandwidth controllers during transient state of conventional arm current control is eliminated. Besides, there is no need to design a separate controller for each frequency signal, therefore the control structure is simplified. On this basis, a comprehensive control strategy of MMC is proposed, which includes reference value calculation of arm current, MPC based arm current control and balancing control of sub-module capacitor voltage. Finally, a three-phase MMC simulation model is built in MATLAB/Simulink to verify the feasibility and effectiveness of the proposed control strategy.
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SHI Shuai, AN Peng, FU Yang, LIU Dong, MI Yang, YANG Xingwu
2020,44(10):92-102, DOI: 10.7500/AEPS20190329001
Abstract:Multi-terminal flexible DC transmission system with integration of wind farms is prone to instability, it is necessary to establish an accurate small-signal model to analyze the stability of small disturbances in the system. However, most of the existing research papers do not consider wind farm models when a small-signal model of DC system with source is established. According to the fundamental theory mentioned above, in time domain, a small-signal model of the DC system integrated with wind farm is established based on the average value model. In order to reflect the power losses of converter, the impedance of equivalent bridge arm on DC side is considered and proposed to simplify the DC-side model derivation of the converter by using parts of the DC line capacitance. At the same time, for the purpose of reflecting impacts of the wind farm integration, point of common coupling (PCC) filter capacitors is also considered. In view of wind farm modeling, a small-signal model of the full-powered wind farm is established, which can constitute a single state space with the converter on wind farm side. In the case, the small-signal model of the three-terminal flexible DC transmission system with integration of wind farms is built. Step response and stability margin of the model is compared with the PSCAD model. The results indicate that the proposed small-signal model can accurately simulate the dynamic response of small disturbance, and the superior performance of the model in system stability analysis is shown.
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2020,44(10):103-110, DOI: 10.7500/AEPS20190527005
Abstract:Transient energy flow method is a new method for locating oscillation sources. Firstly, according to the calculation formula of transient energy flow, combined with the shafting model, the grid-side converter model of doubly-fed wind turbine and the third-order simplified model of doubly-fed induction motor, the transient energy flow for doubly-fed wind turbine is deduced and the energy flow power is defined as an index of the energy flow direction. Secondly, the frequency characteristics of the doubly-fed wind turbine are analyzed after the forced sources are added. Finally, based on the PSCAD/EMTDC electromagnetic transient simulation platform, a single-machine infinite system with forced oscillation sources and a grid connection system of several wind turbines via series compensated line are built for time-domain simulation. Transient energy flow and energy flow power are calculated using the collected data. The validity of the transient energy flow method for locating the forced oscillation sources of doubly-fed wind turbines is verified.
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CHEN Quan, DONG Xiaoming, YANG Ming, LI Haifeng, JIN Tao, WANG Mengxia
2020,44(10):111-118, DOI: 10.7500/AEPS20190727004
Abstract:The increasing ratio of DC power supply in the eastern coastal region puts forward the higher requirements for the safe and stable operation of the receiving-end power grid. Thus, it makes the problem of determining the minimum generator number using the voltage stability as the objective is becoming the research hot topic in the new situation. Firstly, this paper proposes the optimization target for determining the minimum generator number, which can be treated as complex nonlinear and integer optimization problem. Secondly, based on the classical non-cooperative game theory, game power flow distribution model is established. At the same time, the established model is improved by considering the power capacity reserve, weak line, critical loads, and special injection power. Converting minimum generator number optimization model into calculating game balance problems, the determination method of minimum generator number is proposed. Finally, the minimum generator number is determined in the test of IEEE 162-node system and Shandong power grid of China, and the rationality of the game power flow distribution model is verified by sensitivity analysis and the comparison between the calculation results from proposed method and Newton method.
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LIU Liang, SU Sheng, CAO Yijia, KUANG Wenkai, CAI Ye, ZHANG Heng
2020,44(10):119-126, DOI: 10.7500/AEPS20190704004
Abstract:Cyber-attack by the global navigation satellite system has become a real threat with the intensification of attack in cyber space. The slow sustained satellite time synchronization attack can bypass the anomaly detection mechanism of existing satellite clock, trick the timed device to output an incorrect clock signal, and cause serious damage via operation mechanism of the power system. A Kalman filtering based protection method of sustained satellite time synchronization attack is proposed. Firstly, a Kalman filtering based satellite timing model considering sustained malicious interference is developed. Then, clock bias of time synchronism device in malicious attack is optimized by energy functional regularization. Finally, the clock bias is compensated according to the constructed compensation model to achieve precise time synchronization in attack. Simulation results show that this method can effectively prevent the impact of slow sustained satellite time synchronization attacks on the time synchronism system.
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HOU Hui, YU Shiwen, XIAO Xiang, HUANG Yong, GENG Hao, YU Jufang
2020,44(10):127-134, DOI: 10.7500/AEPS20191113002
Abstract:Risk assessment and visualization of power system under typhoon disasters has scientific significance and engineering application value for disaster prevention and mitigation of power systems. In order to predict high-risk areas and optimize the emergency material allocation and risk-based dispatch of power flow, the data layer, knowledge extraction layer and visualization layer are used to construct the risk assessment system for power transmission towers under typhoon disasters. Firstly, based on equipment operation information, meteorological information and geographic information, a spatial multi-source heterogeneous information database is built. Then, based on parameter optimization, six machine learning algorithms are used to establish intelligent models for tower damage risk prediction, and a relative optimal model is selected through index comparison. At the same time, a combined model based on goodness of fit method with unequal weight is proposed. The tower damage risk in a Chinese coastal city under the typhoon “Mujigae” is assessed and visualized with dimension of 1 km×1 km. The relative optimal model is compared with the combined model in detail. The results show that both relative optimal model and combined model can identify the most severely damaged area, but the combined model has better prediction with the same risk threshold, which verifies the feasibility and rationality of the proposed method. Finally, the model universality and the influence of sample magnitude on prediction effect are analyzed.
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SUN Jun, JIANG Tianlong, WANG Yangming, SUN Dan, YE Shankun, DUAN Hui
2020,44(10):135-144, DOI: 10.7500/AEPS20190708005
Abstract:When the grid voltage is unbalanced, since the control bandwidth of the virtual synchronous generator (VSG) is limited, it has almost no effective control over the double-frequency fluctuation component of the power caused by the negative sequence voltage of the power grid. Therefore, the long-term voltage imbalance will cause problems such as stator and rotor current distortion, power and torque oscillation in doubly-fed induction generator (DFIG), which seriously affect the output power quality and operation performance in the system. In order to solve these problems, this paper proposes a method to quantitatively control the electromagnetic torque and the double-frequency pulsation of reactive power for DFIG by using the second-order generalized integrator (SOGI). This method enables the VSG control system of DFIG to achieve three control objectives under unbalanced power grid conditions, namely balanced and sinusoidal stator current, sinusoidal stator current and constant active power, sinusoidal stator current and constant reactive power and electromagnetic torque. At the same time, each control target can be flexibly switched according to the real-time requirements of the power grid, which improves the control performance of VSG control system for DFIG. Finally, the effectiveness of the proposed strategy is verified by simulation results.
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LI Zhihua, ZENG Jiang, HUANG Junchi, FENG Jianlei, XIONG Taojun
2020,44(10):145-154, DOI: 10.7500/AEPS20190824003
Abstract:Microgrid is a nonlinear and strong coupling system with multiple constraints and large load disturbance. The conventional proportional-integral (PI) dual-loop control has been unable to meet requirements. The active disturbance rejection control (ADRC) technology can significantly improve the performance of microgrid inverter control system by compensating the disturbances. This paper proposes a time-frequency voltage control strategy of microgrid inverter based on linear active disturbance rejection control (LADRC). In order to improve anti-disturbance and dynamic performances of microgrid inverter, the decoupling of dq axis, the dimension-reduced extend state observer (ESO) with capacitive current and the linear state error feedback control law are designed and analyzed in the time domain. In order to improve the tracking accuracy and anti-disturbance performance of microgrid inverter at various harmonic frequencies, the frequency response characteristics of time-domain LADRC system are analyzed. Based on it, the real and imaginary decoupling links and the time-frequency domain LADRC strategy are designed and analyzed. Finally, the proposed strategy is verified by experiments for the microgrid inverter operating in the island mode. Experimental results show that the time-frequency voltage control strategy of microgrid inverter based on LADRC has better decoupling, anti-disturbance and dynamic performance when it is compared with PI double-loop control. Moreover, it can accurately control harmonic voltage to achieve harmonic suppression.
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YU Hongru, SU Jianhui, WANG Yiding, WANG Haining, SHI Yong
2020,44(10):155-165, DOI: 10.7500/AEPS20191029006
Abstract:The small-signal model of grid-connected inverter is an important tool for judging system stability and parameter design. The complete state equation of the grid-connected inverter will be accompanied by more redundant information. It is convenient to tune and debug system parameters by adopting appropriate reduced-order model. However, some of the existing typical reduced-order models have narrow applicability, low accuracy under specific conditions or loss of generality with the change of parameters. Firstly, this paper develops a general power-loop model based on the concepts of equivalent inertia constant and equivalent damping coefficient. Through single-side Fourier analysis, it is pointed out that the traditional third-order model is only suitable for the analysis of the systems with large inertia and high damping. Through the analysis of output impedance of grid-connected inverter, it is pointed out that the accuracy of the electromagnetic fifth-order model is sensitive to the control parameters. In order to solve the accuracy problem of reduced-order model, a model order-reduction method based on time constant is proposed by using the characteristics of natural separation of the time scale of inverters. The proposed method is simple and effective. And a simple reduced-order model of the inverter is derived. The obtained model has high accuracy and wide application. Finally, the correctness of the theoretical analysis and the effectiveness of the order-reduction method and the reduced-order model are verified by comparative experiments.
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JIA Yongyong, GAO Shang, SI Xinyao, SHI Yong, ZHAN Xin, WANG Jianhua
2020,44(10):166-173, DOI: 10.7500/AEPS20190430031
Abstract:To solve the difficult problem of monopolar grounding fault detection in flexible medium-voltage DC power distribution network, this paper proposes a new grounding mode with high resistor and arrester in parallel and a protection strategy including adaptive amplification factor. Firstly, advantages and disadvantages of the existing grounding modes in flexible DC distribution network are discussed. A new grounding mode with high resistor and arrester in parallel via the neutral point of the coupling transformer is proposed. Secondly, the overvoltage mechanism and fault characteristics of the new grounding mode are analyzed by theoretical derivation with AC/DC grounding faults. According to voltage and current characteristics in different fault conditions, the DC line protection strategy is developed. It realizes the accurate and rapid fault identification of differential protection with faults in DC network. Finally, the effectiveness of the new grounding mode and the reliability of the proposed protection method are verified by simulation example.
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ZHENG Zuowei, ZHENG Yuping, PAN Shuyan, LIU Longhao, JIE Ping, HAO Houtang
2020,44(10):174-179, DOI: 10.7500/AEPS20190803003
Abstract:The new generation of condenser is gradually used in the ultra-high-voltage direct current (UHVDC) station. Because the excitation voltage criterion of loss of excitation protection of the condensers in operation uses the average value of excitation voltage as its protection action value, it is difficult to distinguish the deeply leading phase operation and complete loss of excitation of the condenser reliably, and cannot distinguish most of the partial loss of excitation with pulse missing. The root mean square (RMS) criterion of excitation voltage is proposed to solve the problem of distinguishing deeply leading phase operation and complete loss of excitation of the condenser with the coordination of the average value criterion. The pulse RMS criterion is proposed to solve the problem of distinguishing partial loss of excitation with pulse missing. The method to calculate the settings of the RMS criterion, average value criterion and pulse RMS criterion is expounded. Results of the dynamic simulation test and on-site test verify the feasibility and validity of the criterion and the method of setting calculating.
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SUN Lingyan, CHEN Yu, XU Bingyin, WANG Zonghui
2020,44(10):180-185, DOI: 10.7500/AEPS20190704006
Abstract:In order to realize the interoperability between the smart terminal units (STUs) for distributed feeder automation (FA) and ensure the communication safety between them, this paper proposes an IEC 61850 communication mapping scheme using built-in secure extensible messaging and presence protocol （XMPP） and generic object oriented substation event (GOOSE) based on user datagram protocol (UDP). The security protection scheme based on Hash obtain random subset （HORS） one-time signature is used to ensure the communication safety of GOOSE messages. The agent-based distributed FA test system is developed with the STUs.The test results show that the scheme can meet the requirements of the quick distributed FA.
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LIU Hao, REN Xiaowei, TIAN Jiannan, LI Jiaxian, BI Tianshu, LAO Yongzhao
2020,44(10):186-192, DOI: 10.7500/AEPS20190517004
Abstract:With the increasing penetration of electronic devices in power systems，electrical quantities are increasingly exhibiting wide-frequency characteristics, and thus new stability issues of power grid have arisen. New requirements for monitoring frequency range and response speed of power system signals are put forward. In this paper, a fast wide-frequency measurement method is proposed to realize the fast and high-precision measurement of the wide-frequency signals. The super-resolution characteristics of spatial spectrum estimation are used to achieve the wide-frequency measurement in a short time window. In order to improve the algorithm stability in low signal noise ratio （SNR） conditions, a kurtosis based method for estimating the number of signal frequency components is proposed， which guarantees the measurement accuracy. Finally, the proposed method is implemented on hardware. The results of simulation, hardware and field tests verify the validity of the proposed method.
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QI Ning, CHENG Lin, TIAN Liting, GUO Jianbo, HUANG Renle, WANG Cunping
2020,44(10):193-207, DOI: 10.7500/AEPS20191030003
Abstract:First of all, this paper analyzes the demand of current distribution network planning, and describes the importance of inclusion of the flexible load resources into planning. Furthermore, the classification methods and results of flexible load are proposed from three aspects, i.e. energy interaction mode, scheduling response mode, user and equipment type. Then, aiming at the influence of flexible load access on the distribution network planning, the adaptability and shortcomings of the existing planning methods are analyzed from four aspects, including load forecasting, power balance, planning optimization and planning evaluation, and corresponding improvement ideas and suggestions are put forward. Finally, the new key technologies such as flexible load modeling, big data mining and application are summarized, and the future development of distribution network construction is summarized and prospected.
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Volume 44,2020 Issue 10
>Views
>Basic Research
>Application Research
>Survey
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XIN Yaozhong, SHI Junjie, ZHOU Jingyang, GAO Zonghe, TAO Hongzhu, SHANG Xuewei, ZHAI Mingyu, GUO Jiancheng, YANG Shengchun, NAN Guilin, LIU Jinbo
2015,39(1):2-8, DOI: 10.7500/AEPS20141008024
Abstract:Firstly, the development history of power grid dispatching automation systems in China is reviewed. The architecture of smart grid dispatching and control systems is described. Then the main technical breakthroughs of smart grid dispatching and control systems are summarized, including improvement of the observability and controllability of ultra large power grids, the coordinated ability of control centers, the early warning ability of on-line dynamic security of ultra large power grids, the economic operation efficiency of ultra large power grids, the ability for power grids to accommodate new energy generation, and the ability of the control centers of power grids to withstand major natural calamities and group cyber-attacks. Finally, further research areas of smart grid dispatching and control systems are outlined.
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WANG Xifan, WANG Biyang, WANG Xiuli, SHAO Chengcheng
2014,38(17):4-13, DOI: 10.7500/AEPS20140324013
Abstract:Offshore wind energy is a promising solution to the environment and energy crisis thanks to its excellent performance of production.It would be further developed with the support from low-carbon economy.This paper summarizes the configuration of offshore wind power systems and surveys their optimal planning methods.Methods of offshore wind farm siting，common topologies of collecting systems and different transmission schemes are reviewed，while reliability evaluation is discussed in detail.Based on this，modeling approaches and algorithms for optimal planning of offshore wind power systems are briefly treated.Finally，some suggestions for potential research directions of optimal planning of offshore wind power systems are made.
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2016,40(1):1-8, DOI: 10.7500/AEPS20151208005
Abstract:The macro energy thinking which regards electricity as a hub between energy production and consumption, can promote “clean energy substitution” of the upstream primary energy and “electricity substitution” of the downstream end-use energy, in order to support the sustainable development of energy. Meanwhile the big data thinking regards various data resources as fundamental elements of production rather than simple process objects. The integration of these thinking will make the big data on power become the foundation of an extensively interconnected, openly interactive and highly intelligent macro energy system. Key elements of this integration include the acquirement, transmission and storage of wide-area power data with different timescales, the data from related domains, as well as the fast and in-depth knowledge extraction from the multi-source heterogeneous data and its applications. As the first part of a series of paper, this paper summarizes unique features of big data based on the deduction of the basic concept, data structures and essential characteristics of big data. For the comprehensive energy network, a knowledge extraction platform is constructed by integrating the causal data (based on mathematical models), the statistic data (with non-causal relationship) and the gambling data (of human participants). More case studies will be proposed in the subsequent paper, which will show the contributions of big data thinking to enhance the economy and reliability of macro energy systems. This work is supported by National Natural Science Foundation of China (No. 61533010), NSFC-EPSRC Collaborative Project (No. 513111025-2013), China-Thailand Cooperation Fund Project (No. 5151101161), and State Grid Corporation of China.
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WEI Zhinong, YU Shuang, SUN Guoqiang, SUN Yonghui, WANG Dan
2013,37(21):196-202, DOI: 10.7500/AEPS20130513006
Abstract:The virtual power plant（VPP），which has received much attention of the developed countries in Europe，is an effective management form of grid connection of distributed energy resources as well as an important component part of the smart grid.In the past ten or more years，the European Union/European countries have carried out many research and pilot projects on VPP.These projects not only have different emphases，but also constitute an integral system.Focusing on VFCPP，Power Matcher VPP，FENIX，EDISON and WEB2ENERGY projects，a description is made of European VPP-related research projects prior to their summation.The major problems of VPP which still need to be addressed are proposed.
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2013,37(1):3-8, DOI: 10.7500/AEPS201209150
Abstract:An analysis is made of the role energy storage technology will play in the development and reform of power systems.A comprehensive survey is made of such aspects as the basic principles，technical performance，development status，main problems，and key bottlenecks needing solution.Evaluation indices for large-scale application of energy storage technology are presented.On this basis，the development and application prospects of multiple energy storage technologies are analyzed and a roadmap is provided.
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2015,39(2):1-5, DOI: 10.7500/AEPS20141204007
Abstract:Barrier exists in every stage of developing a smart grid，from fundamental science and engineering technology research to development，demonstration and operation.Figuring out the critical barrier will be helpful to clarifying how to maximize smart grid's potential，thus providing comprehensive social and economic benefits to the nation.This paper identifies eleven key challenging issues of the smart grid and emphasizes that metrology and standardization are the priority important areas，interdisciplinary cooperative research is the inevitable choice for developing the smart grid，while legal framework and supervision，market design and management reform are the basic guarantees of successfully implementing the smart grid and obtaining the deserved benefits.
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Review of Reactive Power and Voltage Control Method in the Background of Active Distribution Network
CHEN Xu, ZHANG Yongjun, HUANG Xiangmin
2016,40(1):143-151, DOI: 10.7500/AEPS20150330005
Abstract:In order to adapt to the access of high penetration and large-scale distributed generators (DGs), the active distribution network (ADN) has become the research trend of current and future smart grids. The influences of DG access, demand-side management and topology changes on the voltage distribution and voltage stability of distribution network in the AND background are reviewed. The reactive power and voltage control method of ADN are summarized from the perspective of centralized and decentralized control. According to an analysis of the current research status, some of the problems and shortcomings of research on reactive power and voltage control method of AND influenced by various factors are briefly treated. Some problems in research on the AND reactive power and voltage control method are pointed out. This work is supported by National Natural Science Foundation of China (No. 51377060).
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ZHAO Junhua, DONG Zhaoyang, WEN Fushuan, XUE Yusheng
2017,41(4):1-11, DOI: 10.7500/AEPS20160813002
Abstract:The comprehensive energy system, which can coordinate multiple types of energy and be characterized by a deep integration of “cyber-physical-social” systems, is emerging. There is therefore an urgent need to conduct in-depth study on data science and big data mining for energy systems. This paper presents an initial discussion on data science and its applications in comprehensive energy systems. The fundamentals of data science, in particular the importance of the statistical learning theory and data quality, are discussed first. The new progresses in big data mining, such as deep learning, transfer learning and cross domain data fusion, are introduced then. Finally, a brief review is given on the applications of data mining techniques in energy systems; some research problems in energy system data mining, which require further attentions in future, are also discussed. This work is supported by National Basic Research Program of China(973 Program)(No. 2013CB228202), National Natural Science Foundation of China(No. 51477151)and Specialized Research Fund for the Doctoral Program of Higher Education of China(No. 20120101110112).
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QIN Wenping, WANG Peng, HAN Xiaoqing, LIU Zhijuan
2014,38(1):28-33, DOI: 10.7500/AEPS20130529009
Abstract:Reactive power plays an important role in power system reliability as it is closely related to system voltage stability and voltage collapse.However，the reactive power related reliability issues are seldom emphasized in conventional power reliability evaluation.This paper studies the power system reliability from the perspective of active and reactive power，respectively.Active and reactive power inadequacy and the associated voltage perturbation due to system failure are considered in reliability evaluation of power systems.A three-stage load shedding technique for past contingencies are implemented to determine the influence of active and reactive power on system reliability and to find an optimal way to relieve network violation.
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JU Ping, LIU Yongfei, XUE Yusheng, LI Hongyu, SUN Lixia, ZHOU Haiqiang
2017,41(1):1-8, DOI: 10.7500/AEPS20160530011
Abstract:Randomness exists extensively in nature, engineering and social systems, the power system not excepted. Randomness has gradually taken into consideration in power system analysis since the 1970s, with emphasis on analysis of steady-state random problems while research on power system dynamics is still based on the deterministic theory. In recent years, with increasing integration of typical sets of stochastic sources into power systems, such as the large-scale renewable power generation and electric vehicles, the influence of randomness on power system dynamics can no longer be neglected. For this reason, a research framework is proposed for stochastic dynamics of power system focusing on dynamic problems under the action of randomness, including stochastic dynamic modelling, stochastic dynamic responses, stochastic stability, stochastic dynamic security and stochastic optimum control of power system. Some suggestions are given for the research.
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2017,41(13):22-29, DOI: 10.7500/AEPS20161123004
Abstract:The establishment of distribution market needs to rely on the friendly interaction between various resources and power grid in the distribution network. Hence their demand for guidance by a scientific incentive mechanism. To this end, a mode is proposed for encouraging distribution side users interacting with the grid. According to the principle of incentive compatibility, a reasonable and effective price mechanism is suggested to clarify the contribution of flexible users to capacity saving. Relying on the transmission day-ahead market, the participation of users in distribution day-ahead interaction is designed including architecture, process and settlement. Based on the idea of decentralized decision-making, the interactive model of users' self-response and multi-round game of distribution network is simulated. The numerical example shows that, with the proposed mechanism, the costs and benefits arising from interaction can be fairly shared to deeply inspire user interaction with the distribution system, promote effective assets utilization of the grid, and achieve cooperation and mutual benefit as a win-win situation between distribution network and microgrids.
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DONG Zhaoyang, ZHAO Junhua, WEN Fushuan, XUE Yusheng
2014,38(15):1-11, DOI: 10.7500/AEPS20140613007
Abstract:The traditional way of economic and social development，characterized by centralized utilization of fossil fuel energy，is gradually changing.On the other hand，the third industrial revolution is now rising.As the core technology of the third industrial revolution，the Energy Internet aims at facilitating large-scale utilization and sharing of renewable energy by integrating renewable energy and internet technologies.It will enhance the merging of electricity，transportation and natural gas networks，change the way of energy utilization，and finally achieve the goal of promoting sustainable economic and social development.Given this background，an overview of the Energy Internet is first provided，and a basic research framework developed.A definition of the Energy Internet is then suggested，followed by its basic architecture and main components.Several main research challenges to the Energy Internet，such as the wide-area coordination and control of distributed devices，the integration of the power system with the transportation system and natural gas network，as well as the cyber physical modeling and security，are next discussed in more details.
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2017,41(2):1-1, DOI: 10.7500/AEPS20161227013
Abstract:
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LU Zhigang1 ， XIE Xiaowei2 ， LI Xueping1
Abstract:In order to determine the optimal break point sets（OBPSs） for protection coordination in multi-loop network， four indices are introduced as the judgment criterion of OBPSs， the math model looking for OBPSs is developed. Then， based on the principle of bacterial colony chemotaxis algorithm， a new method of determining OBPSs is presented. Comparing with the existing method， the proposed method can find the optimal minimum break point set. An example analysis proves that this method is valid and applicable.
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WANG Yelei, ZHAO Junhua, WEN Fushuan, XUE Yusheng
2015,39(21):1-10, DOI: 10.7500/AEPS20150623001
Abstract:The emergence and development of the power-to-gas (P2G) technique have made the bidirectional energy flow between power and natural gas systems possible. P2G represents a key technique in the emerging energy internet, and promotes the integration of multi-energy systems. By transforming electricity to gas, existing gas storage facilities can be used to mitigate the volatility of renewable energy generation. The modeling of future complex multi-energy systems with P2G functions is presented based on the “energy hub” framework, and a coordinated optimization model presented. A game-theory-based method is next proposed to attain market equilibrium in a multi-energy system. A 4-bus sample multi-energy system and a simplified Victoria gas-electricity combined network system in Australia are adopted for demonstrating the effectiveness of the presented optimization model and solving algorithm. This work is supported by National Basic Research Program of China (973 Program) (No. 2013CB228202) and National Natural Science Foundation of China (No. 51361130153, No. 51361130152).
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GAO Hui，LI Huailiang，ZHAI Changguo，CHEN Liangliang
2013,37(1):186-190, DOI: 10.7500/AEPS201207057
Abstract:In order to improve the energy efficiency of electric vehicle（EV）power battery and increase the start-up power of EV，a maglev flywheel battery energy storage system with the active suspension controlled at five degrees of freedom is designed for EV.The system suspension control principle is expounded，and the radial single freedom transfer function of the maglev flywheel is established by referring to a digital proportion-integral-differential（PID）control algorithm.The frequency spectrum characteristic of the transfer function and the flywheel rotor trajectory curve are simulated，and the30000r/min rotation experiment on the maglev flywheel battery prototype is realized.The experiment results show that the maglev flywheel rotor is capable of high speed steady spin，and with good energy storing ability.The maglev flywheel battery energy storage system will assist the EV power battery work，improve the battery charge and discharge properties and prolong the service life of the motive power battery.
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YANG Ting, ZHAO Liyuan, WANG Chengshan
2019,43(1):2-14, DOI: 10.7500/AEPS20180706005
Abstract:In order to promote the energy production and consumption revolution and build a clean, low-carbon, secure and efficient energy system, it is necessary to develop a new generation of power system and integrated energy system which are more intelligent. Artificial intelligence is one of the most disruptive technologies in the world, which has strong processing ability in computational intelligence, perceptual intelligence and cognitive intelligence. The application of artificial intelligence in power system and integrated energy system will change the traditional utilization mode of energy and promote the further intellectualization of the system. The contents of this review are as follows: the summary of artificial intelligence, the demand for artificial intelligence in power system and integrated energy system, and the various applications of artificial intelligence in the energy field. Finally, the paper presents the future challenges and opportunities faced by the energy field in the era of artificial intelligence.
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2017,41(8):1-1, DOI: 10.7500/AEPS20170305006
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XU Hongqiang, YAO Jianguo, NAN Guilin, YU Yijun, YANG Shengchun, ZHAI Mingyu
2018,42(1):1-7, DOI: 10.7500/AEPS20170518001
Abstract:With the construction of ultra-high voltage(UHV)AC/DC interconnected power grid, the advancement of new energy and the deepening of electricity market reform, significant changes have taken place in the operation of power grid in China, which makes higher requirements on the dispatching and control functions. Based on the integrated distribution and concentration deployment scheme of application functions, this paper gives an overview of the new features of the application function, i. e. , global, rapid and accurate, analyzes the technological support to realize such application functions, and points out the urgency of promotion basic work such as power grid model, operation data and management rules.
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LI Peng, HUANG He, WU Xiaochen, HUANG Mei, YANG Yinguo, LI Ling
2014,38(1):127-133, DOI: 10.7500/AEPS20130712005
Abstract:Security and stability standards of power grids are the basic norm of power system planning and operation."Security and stability guide of power systems" is China's reliability standard which has been in use since 1980s.The guide defines several levels of contingency according to the severity，and requires different defense plans.It has played an important role in security and stability during the period of rapid development of power grids.In 2011，the Central Government of China promulgated"Regulations on accident investigation and handling of electricity safety emergency"，which makes new requirements on grids and power companies from the perspective of load loss.Electricity utilities in China should review their security and reliability standards at present.The paper describes the security and stability standards carried out by the major Western developed countries，compares them with Chinese standards，and makes some useful suggestions for the next version of China's reliability standards.
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Associate editor:Zhang BoMing
Luo An, Wen FuShuan, Wang Qing
