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QU Zhaoyang, DONG Yunchang, LIU Shuai, SHEN Zhixin, YU Jianyou, LI Yufa
2020,44(2):1-12, DOI: 10.7500/AEPS20190708004
Abstract:Due to the unpredictable factors in the integration of society in the ubiquitous power Internet of Things, the interconnection environment is complex and diverse, the types and number of terminal devices are exploding, and security risks such as network attacks and non-secure data intrusions are always faced. Therefore, the existing security detection and protection technology is no longer fully applicable to current ubiquitous power Internet of Things. The security technology for ubiquitous power Internet of Things is discussed from a new perspective of biological immunology. Firstly, the immune process of the immune system compared to that one the pathogen invades the organism is described. The relationship between bioimmunology and security protection of ubiquitous power Internet of things is expounded. Secondly, the security challenges faced by the perception layer, network layer, platform layer and application layer are analyzed. Based on immunology, the key technologies of antigen recognition, immune response and immune memory are summarized. Finally, the safe immune system for the intelligent linkage of ubiquitous power Internet of Things is devised, and the research areas are prospected.
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YANG Ting, LI Yang, HE Zhouze, HAN Xutao, PEN Haibo, LU Yan
2020,44(2):13-21, DOI: 10.7500/AEPS20190814007
Abstract:Automatic optimization and operation of power grid rely on the ubiquitous sensing and complete data support, which are the most basic requirements that must be satisfied in the sensible layer of the ubiquitous power Internet of Things. In the application of power Internet of Things, complete and correct measurement data acquisition is the basis for power quality control. However, in the whole process of data acquisition and transmission, data missing occurs inevitably. Aiming at the above situation, a new method based on low rank matrix completion theory for missing power quality data completion is proposed. This paper first proves that the power quality data have the characteristics of approximate low rank. Based on that, the multi-norm optimization model is designed. The alternating direction method of multipliers is applied to decompose the model into several sub-problems and solve them separately. At the same time, to accelerate the model solution, an optimal selection strategy of adaptive iterative step size is proposed. Effectiveness of the method is verified by high-frequency fault scenarios such as voltage swell, voltage interruption, pulse oscillation and voltage sag. Experimental results show that the method is suitable for power quality data recovery in multiple scenarios, and in the absence of 50% data, the data matrix recovery error is within 3%.
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YING Jun, CAI Yueming, LIU Mingxiang, DU Hongwei, ZHAO Jingtao, YUAN Dong
2020,44(2):22-27, DOI: 10.7500/AEPS20190827004
Abstract:Distribution Internet of Things (D-IoT) is an important part of ubiquitous power Internet of Things. It is an important measure to improve the efficiency of distribution network operation, optimize the business performance and share development results by creating D-IoT ecosystem. In the future， the D-IoT will face the increasing workload of installation, commissioning, operation and maintenance due to the access of massive low-voltage intelligent terminals. This paper proposes a model system for D-IoT based on the Internet of Things model, IEC 61850 and IEC 61968 standards. Also, the communication protocols of the Internet of Things represented by message queuing telemetry transport （MQTT） protocol and constrained application protocol （CoAP） are applied to standardize the communication between devices and realize efficient transmission of terminal data model. Then, the adaptive access process is discussed from three aspects： the first access of the low-voltage intelligent terminals, the function upgrading and the reason for the withdrawal. Finally, the effectiveness of the proposed method is verified by the experiments and engineering applications.
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LI Jianlin, NIU Meng, WANG Shangxing, ZHOU Jinghua, YUAN Xiaodong
2020,44(2):28-35, DOI: 10.7500/AEPS20190711001
Abstract:Battery energy storage system has many advantages such as short construction period, fast response speed and various application modes. In recent years, it has been continuously expanded in scale and has been more and more widely used with the encouragement of national and local governments. Since Zhenjiang 100 MW energy storage station of China was put into operation in July 2018, it has participated in peak load regulation, frequency modulation, emergency response and other auxiliary services. Based on the structural characteristics of the Zhenjiang 100 MW battery storage station, the operation control strategies of different application modes of the station are studied and analyzed, and the response indices and current operation conditions of the station are tested and analyzed to explore the application value of large-scale energy storage power station on the grid side.
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ZHOU Huan, HUANG Longqiong, WU Renjian, HE Xianyu, YUAN Qitao, HE Guangyu
2020,44(2):36-42, DOI: 10.7500/AEPS20190130005
Abstract:Industrial and commercial enterprises are the main groups of energy consumption. The objective and accurate evaluation of the value of integrated energy system to industrial and commercial enterprises is the foundation of optimized operation and energy audit. Traditional methods have certain sufficiency in promoting multi-energy complementarity and renewable energy consumption. Thus, a value evaluation method of integrated energy system based on renewable exergy economy is proposed. Taking the management standard for enterprise energy balance as the basis to do the objective and quantitative calculation, considering three indices of product unit consumption, comprehensive energy efficiency and renewable energy utilization, and by using the fuzzy comprehensive evaluation method, the membership function and dynamic weight coefficients of three indices are designed to calculate the comprehensive value score, which is taken as a basis for choosing the optimal operation scheme. The simulation results show that the evaluation method can select a reasonable operation mode according to the energy consumption law of enterprises and effectively promote energy cascade utilization and local consumption of renewable energy, which verifies the effectiveness and rationality of the method.
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SU Jieying, LIN Kaidong, ZHANG Yongjun, CHEN Zexing, CHEN Boda
2020,44(2):43-52, DOI: 10.7500/AEPS20190516002
Abstract:With the development of gas turbine and power to gas, the coupling degree of power grid and natural gas network is being deepen, and the mutual influence between them has recieved much attention. In this paper, the shortcomings of current researches on the mutual influence between power grid and natural gas network are overcomed from two aspects: power flow algorithm and sensitivity analysis. Firstly, the unified power flow model of integrated electricity and natural gas system is established. The model simplifies the equation dimension by means of reducing variables, and the model considers the slow time-scale characteristics of natural gas transmission based on the line-pack model. At the same time, in order to avoid the sensitivity of traditional Newton method to the choice of initial state value in the power flow solution of natural gas network, the Newton descent method is proposed to solve the unified power flow model. Furthermore, based on the sensitivity analysis method, with the sensitivity of gas pressure-injected power of electricity-gas coupling node as the key characterisitic quantity, a comprehensive sensitivity index for the analysis of the coupling mechanism of integrated electricity and natural gas system is proposed in order to provide decision-making assistance for the joint operation of the two networks. The analysis of examples verifies the effectiveness of the proposed algorithm. By comprehensively comparing and exploring the interaction characteristics of integrated electricity and natural gas system with the coupling of gas turbine and power to gas, the positive role of line-pack characteristics of the natural gas network in response to system disturbances is verified.
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XU Zhou, SUN Yonghui, XIE Dongliang, WANG Jianxi, ZHONG Yongjie
2020,44(2):53-59, DOI: 10.7500/AEPS20190620005
Abstract:Flexible load scheduling is an important means to optimize load curve, reduce equipment capacity, and promote renewable energy accommodation. Taking transmission delay of heating network and ambiguity about temperature perception into account, a thermal flexible load model is established. Considering three types of electric flexible load including shiftable, transferable and curtailable loads, with the minimum total cost including investment, operation and compensation cost as the objective function, an optimal configuration model of power/thermal energy storage for regional integrated energy system (RIES) is established. Moreover, a simulation program using a commercial software called LINGO is developed to obtain the optimal output of each device and optimal capacity of energy storage. Compared with the scenario where the power/thermal flexible load is not considered， simulation results indicate that the participation of the power/thermal flexible load can optimize the power/thermal load curve, reduce the capacity of the energy storage device, enhance the flexible adjustment capability of RIES, reduce the energy consumption and investment cost of energy storage, and achieve the optimal economic operation of the system.
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LI Bin, CHEN Jingsheng, WANG Yan, XI Peifeng, QI Bing, SUN Yi
2020,44(2):60-67, DOI: 10.7500/AEPS20190228002
Abstract:In order to cope with the increasing quality of service （QoS) requirements for demand response services, this paper firstly analyses the characteristics of demand response services and establishes refined traffic models of demand response services. Secondly, by decomposing the communication delay of demand response, the main reasons for the congestion of the demand response communication networks are analyzed. Then, in order to satisfy the quality of service requirements of demand response services, a dynamic scheduling strategy of improved weighted fair queuing based on fuzzy logic is proposed, which considers the dynamic characteristics of load conditions and service burst degree of communication network for demand response services. The simulation results show that the proposed dynamic queue scheduling strategy of demand response can balance the quality of service requirements of different demand response services, reduce the transmission delay of low priority demand response services and improve the jitter performance of transmission delay.
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SUN Weiqing, XIANG Wei, PEI Liang, LI Hongzhong, XI Peifeng
2020,44(2):68-75, DOI: 10.7500/AEPS20190522003
Abstract:Load aggregators (LAs) can provide high-quality ancillary service for power system and receive benefits by aggregating distributed user-side resources. However, the uncertainty of user-side response will exert negative effects on both ancillary service quality and economic benefits of LAs. To overcome such a problem, the controllable load resources are considered as virtual energy storage (VES), and combined with narrow sense energy storage (NSES). Then an uncertain response model of generalized energy storage (GES) is established. Furthermore, two control strategies of LAs, namely NSES priority response and VES priority response, are proposed, and the characteristics of both strategies are discussed. Finally, a revenue model of LAs participating in the ancillary service market using the two control strategies is presented, which is verified for the effectiveness using the operation data of PJM electricity market of America. Case studies show that the LAs can get considerable economic benefits by configuring relatively small amount of NSES equipment and adopting the control strategy of VES priority response.
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CHEN Zhong, LIU Yi, CHEN Xuan, ZHOU Tao, XING Qiang
2020,44(2):76-84, DOI: 10.7500/AEPS20190114010
Abstract:Electric vehicle (EV) has the ability to participate in interaction with power grid as a kind of new distributed energy storage and its most distinct characteristic is its mobility. This paper investigates the characteristics of mobile energy storage and develops the mobile storage model of EV based on the theory of parking generation rate. The mobile behavior of EV is described by taking gridded region as a unit. A synergy vehicle-to-grid (V2G) strategy for mobile energy storage of EV and renewable energy is proposed with the minimum load fluctuation of power gird as its optimization objective, which considers the constraints of power flow, battery performance, owner demands and EV mobility. Finally, case study is conducted in two different scenarios including different mobile characteristics and the scales of EVs. The simulation results show the influence of characteristics of mobility energy storage on the proposed strategy and validates the feasibility of the proposed model and strategy.
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ZHANG Bo, TANG Wei, CAI Yongxiang, WANG Zhaoqi, LI Tianrui, ZHANG Han
2020,44(2):85-93, DOI: 10.7500/AEPS20190305005
Abstract:Integration of high-proportion residential photovoltaics (PVs) causes serious voltage problems such as voltage violations. Reactive power control of PV inverter and active power control of energy storage system (ESS) are the effective voltage control methods for low-voltage distribution network (LVDN). Aiming at the limited communication conditions of LVDN and the insufficient research on coordination of reactive power of inverter and active power of ESS, a two-stage distributed control strategy based on consensus algorithm for PV inverter and ESS is proposed in this paper. Firstly, through the control effect-cost coefficient to analyze the effect and economy of adjustment for the equipment, a voltage control architecture is proposed in which the reactive power of inverter is first adjusted and then the active power of ESS is adjusted. Then, at the inverter control stage, the utilization ratio of reactive power is used as the consensus variable to ensure that the voltage regulation task is shared according to the inverter capacity. In the ESS control stage, the state of charge (SOC) of ESS is taken as the consensus variable, which not only considers the ESS capacity but also realizes the simultaneous control of ESS power and SOC. The simulation results demonstrate that voltage violations can be effectively mitigated, and voltage control cost can also be reduced. At the same time, the selection range of the control strategy parameters is given.
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HU Di, DING Ming, BI Rui, GAO Pingping, ZHANG Yu, ZHANG Jingjing
2020,44(2):94-103, DOI: 10.7500/AEPS20190618006
Abstract:To solve the problem of grid-resource-storage planning of distribution networks with high penetration of distributed generator(DG) clusters and promote the reliability indices of load points, this paper proposes a two-step planning method. The first step is to conduct the multi-objective grid-resource planning of DG clusters considering isolated operation probabilities of clusters. Based on the isolated operation probabilities of clusters obtained in the first step, the energy storage planning in the second step is conducted to guarantee that DG integrated with the clusters could satisfy the isolated operation of clusters. Considering the isolated operation of clusters and the uncertainties of the grid connection during the planning process, the up-stream delivery and the down-stream combination of the reliability index calculation method in the grid-resource planning model are improved. Since the grid-resource collaborative planning model in the first step is a multi-objective problem, augmented ε-constraint method（AUGMECON） is introduced to solve the multi-objective planning model. AUGMECON could provide decision makers with the richer alternatives. Taking the actual distribution network with high penetration of DG in China as an example, it is verified that the proposed grid-resource-storage planning method based on cluster partition can improve the reliability of the system and decrease the power losses and voltage fluctuations.
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JIA Zhaohao, ZHANG Feng, DING Lei
2020,44(2):104-112, DOI: 10.7500/AEPS20190411009
Abstract:Distributed generators with high permeability cause voltage quality problems such as voltage deviation and fluctuation, and increase network loss as well. Aiming at this problem and taking configuration of energy storage as a solution, the optimal allocation strategy of energy storage location and capacity of distribution network is put forward combined with the power four-quadrant output control strategy of the battery energy storage system, which aims at improving the economic benefit and voltage quality of the distribution network. Specifically, an economic operation model for distribution network with the goal of minimizing the sum of purchase cost, network loss cost and investment cost is constructed. The time scale is set as 15 min for rolling calculation, and the lowest total cost in a typical day is used to choose the siting and sizing of storage. Meanwhile, the migration and fluctuation range of each node voltage is constrained, and the mixed integer second-order cone mathematical programming is used to optimize the solution. The simulation results of IEEE 33-bus distribution network demonstrate the feasibility and efficiency of the proposed optimal configuration method.
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MENG Yutian, YAN Zheng, XU Xiaoyuan, FANG Chen
2020,44(2):113-121, DOI: 10.7500/AEPS20190127001
Abstract:In distribution network state estimation, measurement devices are limited and network observability is not achieved unless pseudo measurements are used. Considering the measurement errors and the deviations between the pseudo measurements and the actual values, the (pseudo-) measurements have uncertainties in distribution network state estimation, which will affect the performance of state estimation. The global sensitivity analysis method of the distribution network state estimation is proposed, to identify the critical (pseudo-) measurement uncertainties and their locations, which have an impact on the accuracy of state estimation. Based on the sparse polynomial chaos expansion, the global sensitivity indices are calculated to improve the computational efficiency of the global sensitivity analysis. And the metering placement method based on the importance ranking of uncertain parameters is provided. The proposed approach is tested on the IEEE 33-bus distribution system. Compared with the common methods, the accuracy and efficiency of the proposed method are verified. This method overcomes the shortcomings of the traditional state estimation sensitivity analysis. It evaluates the influence of the correlation of (pseudo-) measurement uncertainties on state estimation. The metering placement method based on the global sensitivity analysis is able to significantly improve the accuracy of distribution network state estimation.
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XU Yin, WANG Ying, HE Jinghan, LI Chen
2020,44(2):122-130, DOI: 10.7500/AEPS20190106005
Abstract:When an extreme disaster causes a blackout, multiple power sources could be coordinated with energy storage to restore critical loads, which is able to enhance the resilience of distribution network. Firstly, the role of multiple coordinated sources for service restoration in enhancing the resilience of distribution network is introduced. Secondly, the multi-period load restoration problem is formulated and relaxed as a mixed integer second-order cone program, with the goal of maximizing the weighted power supply time of the load and minimizing the total power loss. The load state, output power and commissioning state of power lines in each period are taken as optimized variables, and finite energy constraints, operational constraints and topological constraints are considered. The proposed model could be efficiently solved by commercial solvers and then the optimal recovery strategy is obtained. Finally,based on standard cases of the modified IEEE 13-bus and IEEE 123-bus test distribution systems, the simulation results show that the proposed method is effective and superior.
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LI Peng, MA Xian, LI Yuwei, CHEN Bo, FANG Qing
2020,44(2):131-137, DOI: 10.7500/AEPS20190129004
Abstract:The output power of high-penetration wind power and photovoltaic generation in microgrid is random and fluctuating. Meanwhile, the load power in microgrid is stochastic and varying,which easily causes frequency fluctuations in the microgrid. Moreover, the operation mode change of the microgrid will cause in variations in both network equivalent parameters and operation parameters. Consequently, aiming at frequency fluctuations and parameter perturbation of controlled objects in AC/DC hybrid microgrid, this paper proposes a frequency control method for the AC/DC hybrid microgrid based on H ∞ mixed sensitivity, which can control and stabilize the AC-region frequency. Firstly, the
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LYU Zhe, WANG Zengping, XU Wanyu, LIANG Jiadi
2020,44(2):138-145, DOI: 10.7500/AEPS20190410002
Abstract:With the gradual application of unified power flow controller (UPFC) as new generation components of flexible AC transmission systems in transmission lines, it is necessary to study the protection principle of the line with UPFC in deep. By analyzing the transient influence of UPFC on fault line, it is concluded that the series side of UPFC has a serious attenuation effect on the high frequency components, and the reliability of single-end transient protection is reduced. The analysis of the fault transient characteristics of busbar-connected outgoing lines shows that there is a significant difference in the current spectrum distribution between the fault side line and the non-fault side lines for the same busbar. By using the wavelet energy entropy to extract the transient information of each outgoing line of the busbar, a directional pilot protection scheme for the line with UPFC is proposed. The simulation results show that the scheme can accurately identify the internal faults, external faults and bus faults. The scheme also has good sensitivity and reliability under fault conditions such as different transition resistances and fault inception angles.
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HAN Chang, YAO Yan, REN Jiaorong, XU Jiayu, LIN Zhenzhi, YANG Li
2020,44(2):146-154, DOI: 10.7500/AEPS20190201004
Abstract:In order to improve the enthusiasm of the power pipelines entering into urban underground utility tunnels, it is of great significance to formulate a fair and reasonable cost sharing method. The cost sharing model for the power pipelines entering into utility tunnels is established by using the deviation minimization method considering interest balancing of plural subjects. The entrance expense and daily maintenance expense are allocated to pipeline companies by the proposed model. The occupied space, the direct buried cost, the direct buried operation and maintenance cost of each pipeline are taken as the proportion factors. The satisfaction degree to the cost sharing results of all pipeline companies is taken as the group satisfaction factor in the cost sharing model. The interest of power companies and the other pipeline companies is balanced with the cost sharing willingness of each pipeline company and the evaluation results of the independent third party. Finally, the effectiveness and practicability of the proposed method are verified by the case study results of the utility tunnels in a city.
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XU Shihong, ZHANG Hongzhi, LIN Xiangning, LI Zhengtian, ZHUO Yixin, WANG Zhixun, SUI Quan
2020,44(2):155-162, DOI: 10.7500/AEPS20190123002
Abstract:To solve the problem that traditional point-to-point prediction method is not applicable to the load with large fluctuation and uncertainty, this paper implements a prediction interval method based on improved evaluation index to improve existing forecasting evaluation index from two aspects of interval width and cumulative error, which enhances the reasonableness of prediction results. On this basis, weighing the characteristics and importance of each evaluation index for the influence on prediction results, the comprehensive evaluation index for interval prediction is established, and the interval prediction model is constructed by using neural network. Aiming at the optimization of the comprehensive evaluation index, the particle swarm optimization algorithm is used to train and optimize the structure parameters, so as to achieve ideal effect of interval prediction for fluctuating load. The historical load data with strong uncertainty is used to validate the proposed method. Comparing with the traditional point-to-point and interval forecasting methods, the results and analysis of the improved interval prediction verifies the effectiveness and superiority of the method.
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ZHANG Yan, LYU Quan, LI Yang, ZHANG Na, WANG Haixia, SUN Hui
2020,44(2):163-171, DOI: 10.7500/AEPS20190509006
Abstract:This paper shows that power-heat decoupling transformation of combined heat and power (CHP) plant is the essence of configuring short-term heat sources for CHP units. From the view of configuring compensation heat sources, applicable scenarios, feasible operation region, heating cost and heating capacity of four compensation strategies are analyzed, including heating storage, electric boiler, bypass compensation and low-pressure cylinder cut-off . The operation flexibility evaluation model of transformed CHP plant is established. Examples are given to analyze the flexibility improvement effects of the four strategies in different scenarios when they are used alone or in combination.
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PENG Chenyu, CHEN Ning, GAO Bingtuan
2020,44(2):172-179, DOI: 10.7500/AEPS20190105003
Abstract:An ultra-short-term wind power forecasting method combining multiple clustering algorithm and hierarchical clustering algorithm is proposed. To deal with the dynamic condition of training samples and identify the samples that are similar to the characteristics of the period to be predicted, the historical power series and historical meteorological series are clustered separately. The clustering index of the power series consists of Euclidean distance and covariance, and the layer-by-layer method is used for meteorological series clustering. Two clustering results are combined into multiple sample subsets. Multiple neural network forecasting models based on particle swarm optimization and back propagation (PSO-BP) are established by using the method of classification modeling and feature matching. And the model with the most similar characteristics to the predicted period are used. The proposed forecasting approach has been applied in actual wind generation data tracking in Qinghai province of China. The simulation results show that it can improve the forecasting accuracy of ultra-short-term wind power.
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SHENG Siqing, LI Pengwang, GU Qing
2020,44(2):180-187, DOI: 10.7500/AEPS20190125006
Abstract:The high-penetration integration of volatile wind power degrades the damping characteristic and the primary frequency regulation performance of the power system, which restricts the further improvement of the wind power penetration. This study improves the frequency regulation capability of the high-penetration wind power system while maintaining the dynamic stability level of the system, which is of great importance to increase the wind power penetration limit. Firstly, the paper puts forward a solution to the wind power penetration limit with constraints of damping ratio and frequency deviation. Then, based on the opposite effects of inertial parameters of thermal power units on the damping characteristic and the primary frequency regulation performance of the system, a coordinated optimization method for the inertial parameters of thermal power units is proposed, which considers the damping ratio and dynamic frequency response capability of the system. The simulation results prove that the calculation results of the proposed solution to the wind power penetration limit are of high reference value. After the introduction of the coordinated optimization strategy, the dynamic stability characteristic and the primary frequency regulation characteristic of the system are improved effectively. The optimization effect has a strong applicability and the wind power penetration of the power system has also been improved.
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ZHANG Yi, WANG Youran, LIU Hang, SHAO Zhenguo, LIN Fang, CHEN Yuxin
2020,44(2):188-196, DOI: 10.7500/AEPS20190220002
Abstract:Conventional harmonic responsibility determination methods have shortages such as the inability to achieve long-time scale dynamic responsibility determination, the need for special measurement, the inability to utilize the data of existing monitoring systems, and the inability to determine the harmonic responsibilities of users on the same feeder. Thus, this paper proposes a determination method of user harmonic responsibility based on correlation analysis of monitoring data. Firstly, the monitoring data are collected, including the harmonic voltage data from the power quality monitoring system and the average active power data of each user from the power information collection system. By the canonical correlation coefficients based on these data, the harmonic responsibility at the point of common coupling (PCC) is divided into the background harmonic responsibility and the harmonic responsibility of concerned users. Secondly, the dynamic distortion correlation coefficients of harmonic voltage and active power of each user are calculated, which are used to reflect the relationship between user power consumption behavior and harmonic voltage distortion at PCC. Finally, the long-time scale index for harmonic responsibility determination is developed with consideration of the relationship and user power consumption capacity. The validity and practicability of the proposed method are verified by the data in the actual monitoring system, and the long-time scale dynamic harmonic responsibility determination of each user on the feeder can be realized based on the existing monitoring data.
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Analysis and Evaluation of Voltage Sag Severity Based on Data Mining and Improved Grey Target Theory
PU Yuting, YANG Honggeng, MA Xiaoyang
2020,44(2):197-205, DOI: 10.7500/AEPS20190326014
Abstract:Aiming at the problem of voltage sag severity evaluation, a data mining and analysis method based on mutual information and improved grey target theory is proposed. The index of sag distance and cross influence domain is proposed, and the framework of severity evaluation is established considering various characteristic attributes of voltage sag. A mutual information network model is constructed for data mining of voltage sag, and a voltage sag knowledge base is built by using connection weight to extract rules to preliminarily analyze the severity level of voltage sag in the whole grid, which avoids the problem of conflict rules caused by traditional support and confidence based data mining methods. An improved method for calculating the target centricity is proposed. Combining with the sag severity level of the whole grid obtained from data mining, a conditional search model of voltage sag severity is established to evaluate the sag severity of substation, which solves the problem of multiple matching results and improves the accuracy of voltage sag evaluation. The feasibility of the proposed method is verified by an example analysis.
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2020,44(2):206-213, DOI: 10.7500/AEPS20190110005
Abstract:The traditional active power filter (APF) using inverter technology needs to use electrolytic capacitor bank for energy storage, which has the disadvantages of large size, high price and low reliability. To solve this problem, this paper focuses on the single-phase AC/AC-type APF without DC energy storage unit. The principle of reactive power and harmonic comprehensive compensation based on even-order harmonic modulation (EHM) technology is introduced. The Fourier series method and data fitting method are used to obtain the relationship of frequency and quantity between each even-order modulation term in the duty cycle and odd-order components in the compensation current. A decoupling modulation strategy is proposed for the coupling control of even-order modulation wave, which improves the compensation accuracy and stability of the system. A single-phase comprehensive compensation scheme is designed, and the simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategy.
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QIU Zhiyong, ZHOU Yuede, LIU Zhongping
2020,44(2):214-220, DOI: 10.7500/AEPS20190525002
Abstract:With the continuous expansion of power grid, it is of great practical value to rapidly form the node impedance matrix of large-scale power grid. In order to accelerate the generation of impedance matrix, a graphic processing unit （GPU）-based parallel branch addition method is designed based on collaborative central processing unit （CPU） and GPU computation architecture. In addition, by analyzing the relationship between the topology structure of power grid and the chain branch, an optimized algorithm of node numbering is designed based on the minimum loop of the graph theory. The minimum loop of the substation level is extracted from the connections of plants/substations, and the topological sort is used to determine the order of group additions. The order of substation additions is determined based on the group, and then node numbering order is optimized. The experimental results show that, comparing with the serial computing method, the proposed method has a significant improvement in computation efficiency. In the calculation of large power grid, the speedup ratio could get tens of times, and the speedup ratio of additional chain branches could reach hundreds of times.
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XIONG Wei, YAN Faqi, WANG Yang, LUO Shenzeng, CHEN Wenzhe, CHEN Lei
2020,44(2):221-226, DOI: 10.7500/AEPS20190823006
Abstract:The probability distribution and the corresponding causes of frequency in different years， in interconnected mode and isolated mode, are analyzed based on massive measurements in an actual regional power grid. In the interconnected mode, the probability distribution changes from band distribution with shape edges to bimodal distribution. The reason is that the standard deviation of the system power imbalance is increasing, resulting in a large frequency fluctuation, and the primary frequency regulation frequently acts to form the bimodal distribution. In the isolated mode, the probability distribution exhibits an obvious bimodal distribution. The reason is that the decrease of grid scale leads to severer frequency fluctuation and frequent action of primary frequency regulation. The key work for improving frequency regulation of power grid is to strengthen ultra-short-term prediction and intraday planning balance and reduce system power imbalance.
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CHEN Le, SHE Zhenqiu, WANG Junsheng, WANG Yangzheng, XU Bin, LU Dongbin
2020,44(2):227-233, DOI: 10.7500/AEPS20190618010
Abstract:In the ultra-high voltage direct current (UHVDC) projects which is based on the structure of dual 12-pulses valve groups in series, the following actions may lead to the metallic-bypass branch operation: the manual and auto sequence control of switching equipment in DC yard, the protective blocking of one pole, the online protective quitting of valve groups. This paper describes the forming process of the metallic-bypass branch operation and proposes the corresponding countermeasures. The prevention should be taken as the major principle in dealing with metallic bypass branch operation, and the isolation methods should be taken as the supplementary measures，such as the pole isolation and the failure protection of neutral bus switch. The countermeasures described in this paper have been applied in the ±800 kV UHVDC project from northwest Yunnan to Guangdong in China Southern Grid. The on-site test and simulation test show the problem of metallic-bypass branch operation in dual 12-pulses valve groups in series has been effectively solved.
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2020,44(2):234-246, DOI: 10.7500/AEPS20190520001
Abstract:In power system off-line and real-time electromagnetic transient simulation, the ideal switch model is often used for typical controllable power electronics devices represented by insulated gate bipolar transistor (IGBT). With the increasing applications of IGBTs in AC/DC converters and DC circuit breakers, the operation status of IGBT can affect the dynamics of system transients which can increase the voltage current pressure of devices in serious cases. This may cause damage to the device and consequently threat the safe and reliable operation of the converter and the complete system. Electromagnetic transient simulation based on ideal switch model cannot accurately simulate the characteristics of the device and the pressure， which it is subjected to in the transient process. The study of the inter-dynamics among the system circuit, individual devices, and the corresponding control system requires IGBT modeling schemes with higher accuracy for electromagnetic transient simulation. In recent years, detailed modeling schemes of multiple IGBT and decoupling methods are proposed and applied in off-line and real-time simulation. Due to the rapid development of high-performance computing platform, relatively detailed models can be applied to the simulations of AC/DC power system with a large amount of IGBT devices. The modeling schemes are classified and the function, the modeling complexity, and the accuracy of various IGBT models are analyzed. The system solution schemes, parallel computing schemes and the simulation platforms in detail are also described. Moreover, typical applications of IGBT detailed modeling schemes are introduced. The difficulties and limitations in areas of IGBT modeling schemes, system solution methods, parallel computing schemes and applications are analyzed, and the corresponding research suggestions are proposed as well.
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Volume 44,2020 Issue 2
>Basic Research
>Special Report
>Cyber Energy Systems
>Basic Research
>Application Research
>Egineering Application
>Survey
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LOU Xiansi, MA Guang, GUO Chuangxin, WANG Luyu
Available online:January 17, 2020 DOI: 10.7500/AEPS20190429011
Abstract:In view of the multiple uncertain risk factors faced by the operation of power grid, this paper analyzes the necessity of risk coordination control from the perspective of risk development and dispatching mode. Based on the view point of risk coordination control, a system of risk coordination control for the whole process of power grid operation including four stages of medium and short-term, day-ahead, real-time and post-contingency is proposed. The risk optimization models, control measures and coordination strategies in each stage are elaborated in detail. A solution based on five-tier software framework is proposed and key technologies for supporting system application are discussed. Finally, the preliminary implementation of the whole process risk coordination control system in the Zhejiang Power Grid is introduced. The results of theoretical analysis and engineering practice show that the proposed system and framework in this paper can adapt to the “open, fair and just” power dispatching, coordinate the risk control decisions in each stage and realize the step-by-step tracking and rolling control for the operation risk of power grids.
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LI Zhen, SHENG Wanxing, DU Songhuai, LI Penghua, WANG Jianhua
Available online:January 16, 2020 DOI: 10.7500/AEPS20190812008
Abstract:Supplying power for loads and realizing the connection of distributed generators (DGs) are the essential functions of the flexible distribution equipment (FDE). Consequently, the control of AC port in FDE is intensely crucial. Aiming at the voltage control of AC port in FDE, the three-phase voltage is controlled independently based on the virtual synchronous generator (VSG) control, and its dynamic performance is improved by cascaded quasi proportional-resonant (PR) voltage outer-loop and current inner-loop. Furthermore, the influence of output current of AC port in FDE on the voltage is analyzed in detail by taking single-phase voltage as an example. And the current feedforward control strategy is proposed to ensure the voltage stability of AC port while loads and DGs are varied. The output impedance of AC port is obtained by the impedance modeling method, and the stability of AC port in FDE is analyzed by generalized Nyquist stability criterion when FDE supplies power for loads and realizes the DGs’ connection. Finally, the correctness and effectiveness of the proposed control strategy are verified by simulation and experiment.
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WEI Nengqiao, ZHOU Niancheng, LUO Yongjie, WANG Qianggang
Available online:January 15, 2020 DOI: 10.7500/AEPS20190626004
Abstract:DC circuit breakers (DC circuit breaker，DCCB) need high operate speed and current break ability because fault current of flexible dc grid rising fast and conventional half-bridge Modular Multilevel Converters are short of over current resistant ability. Fault current limiter (fault current limiter，FCL) can retrain fault current when short-circuit fault is identified, and reduce the requirement of DCCB. This paper calculate the fault current and voltage stress of FCL with different type of fault limiting impedance, and the change with parameters are analyzed; a parameters optimization method of fault limiting impedance which optimization objectives are breaking current of DCCB and cost of FCL is established. The method proposed in this paper can adjust to different flexible dc system and type of current limiting impedance, and optimize parameters with constraints. Works in this paper are verified through PSCAD/EMTDC simulation.
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HU Changbin, WANG Haipeng, LUO shanna, ZHOU Jinghua, SHI Yuntao, MA Rui
Available online:January 15, 2020 DOI: 10.7500/AEPS20190805002
Abstract:Abstract: Aiming at the problem of bus voltage control in DC microgrid, a dynamic compensation control strategy based on robust disturbance observer is designed to complete voltage compensation of DC-DC converter. Firstly, based on the DC microgrid system architecture, the theoretical analysis of the bus voltage fluctuation is carried out. Secondly, the state space mathematical model of the DC-DC converter of the DC microgrid system is established, and the input and output relationship of the control system is obtained. According to the robust dual-mass decomposition and Youla"s parameterized stability controller theory, the proposed robust disturbance observer control architecture is proved. The model matching theory is applied to compensate the output value generated by the current disturbance. The voltage loop compensation controller Q(s) is solved by a linear matrix inequality (LMI) method, and the current loop compensation controller H(s) is designed according to the dynamic structure diagram of the DC-DC converter. The results of semi-physical experiments show that the architecture can improve the dynamic performance of DC-DC converter without changing the structural parameters of the original system, and suppress DC bus voltage fluctuation caused by load switching, power fluctuation and AC side load imbalance, and enhances the robustness of the system.
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ZHENG Tao, WU Qiong, LYU Wenxuan, LI Rui, XU Lie
Available online:January 15, 2020 DOI: 10.7500/AEPS20191114003
Abstract:DC faults in the flexible DC distribution network could easily lead to overcurrent, which seriously threaten the safe operation of the network. FBSM-MMC blocking is mostly used to cut off the fault current in the distribution network which based on the FBSM-MMC. But the blocking will cause power outage of the whole network for a moment, which is not conducive to the reliability of the power network. Aiming at the problem, a protection scheme combined by the control of MMC and the protection of DC network is proposed, which consists of three stages. After a short-circuit fault occurs, the output DC current of the inverter will be limited to 1.2pu by the control of MMC(Stage 1). The faulty line is identified according to the synchronous zero-crossing characteristic at both ends of each line(Stage 2). A fault isolation scheme which contains the cooperation of DC circuit breakers and high speed switches is proposed(Stage 3). The switch in the faulty line can be turned off quickly with the associated DC breaker disconnected and the associated MMC’s output current reduced to 0. Finally, the feasibility of the proposed protection scheme and the isolation scheme is verified by a large number of simulations in PSCAD/EMTDC.
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SHEN Jun, LIU Wei, LI Hucheng, LI Na, WEN Zhen, YIN Minghui
Available online:January 15, 2020 DOI: 10.7500/AEPS20190521007
Abstract:Aiming at the problem of frequency and voltage static deviation caused by primary control of distributed generation in microgrid, a distributed secondary optimal control based on reinforcement learning local feedback method is proposed, which addresses the need of frequency recovery and voltage adjustment by just using local information. Firstly, according to the demand of microgrid economy, frequency and voltage control and the comprehensive performance of distributed generation (environmental benefit, economic benefit and technical benefit), a local reward is defined to coordinate the frequency recovery and voltage regulation of multi-microgrid. Secondly, in view of the actual operation of the power grid, while satisfying the balance between supply and demand, the multi-agent reinforcement learning algorithm is used to optimize and modify the global reward feedback, so that the frequency deviation can be eliminated asymptotically and the stable operation of the microgrid can be guaranteed. Finally, the effectiveness and adaptability of the proposed control are verified by the analysis of case study.
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ZHAO Chengyong, SONG Bingqian, XU Jianzhong
Available online:January 14, 2020 DOI: 10.7500/AEPS20190626003
Abstract:The flexible DC grid power electronic equipment is highly controllable but fragile. There are strong coupling relationships between various power electronic equipment during the fault process. The coordinated control of the fault process is difficult, and proactive control of the fault current still faces great challenges. Based on the fault current development mechanism of flexible DC grid, the paper compares and summarizes the fault characteristics of AC and DC grids. The basic principles of active current control scheme for flexible DC grid faults are determined. The domestic and international research results are summarized. The principle and suppression principle are classified. Several typical schemes are taken as examples to analyze the characteristics of different types of active control schemes, and simulation verification is carried out in PSCAD.
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LI Yalou, SUN Qianhao, MENG Jingwei, MU Qing, ZHANG Xing
Available online:January 14, 2020 DOI: 10.7500/AEPS20190715001
Abstract:The electromagnetic transient (EMT) simulation of hybrid modular multilevel converter (MMC) is an important basis for the related researches about hybrid MMC. However, because there are various kinds of sub-module (SM) circuits can be employed in hybrid MMC, and a lot of power electronic switches are included in each SM circuit, the detailed EMT model of hybrid MMC will reduce the simulation efficiency seriously. In view of this background, the unified dynamic averaging equivalent model of the series structure of the various SM circuits is proposed in this paper based on the switching function and the dynamic characteristic of capacitor. Besides, a unified terminal high efficiency EMT model of hybrid MMC based on the proposed dynamic model of the series structure is also presented and analyzed. The proposed unified model in this paper not only is convenient but also has the great simulation accuracy and efficiency, which is especially important for a research tool. The simulation accuracy and efficiency of the proposed model are validated by the comparison with the detailed model in ADPSS.
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ZHANG Fuxuan, GUO Xianshan, WANG Nannan, TIAN Jie, LU Yu, DONG Yunlong
Available online:January 14, 2020 DOI: 10.7500/AEPS20190225001
Abstract:Large-capacity renewable energy is transmitted through bipolar voltage source converter based high voltage direct current (VSC-HVDC) system in the island mode, which has broad application prospects. This paper analyzes the power surplus characteristics under the non-fault-pole overload and DC overvoltage conditions. Then the scheme of grouped AC energy dissipation resistor is proposed. The power surplus control strategies are designed in the cases of converter fault in sending end and DC overvoltage. By accurately switching the grouped AC energy dissipation resistor, the outage of bipolar VSC-HVDC system caused by power surplus is avoided. The proposed two power surplus control strategies are verified in real-time digital simulator (RTDS) and EMTDC simulation system of four-terminal VSC-HVDC power grid. Simulation results show that the proposed strategies can realize fault ride-through under the condition of power surplus, and the expansion of fault coverage can be avoided.
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LI Yan, HuangYu, GONG Yanfeng, PanXudong
Available online:January 14, 2020 DOI: 10.7500/AEPS20190425008
Abstract:For MMC-based flexible DC grid with symmetric monopolar topology, this paper studies the evolution law of fault currents of single pole to ground fault and bipolar fault, and thus reveals that non-faulted line charging and fault waves are respectively the main reasons for the overvoltage of single pole to ground fault and bipolar fault. Then, a three-terminal flexible DC grid is used for simulation and verification, and the influences of different factors on overvoltage are analyzed. The results show that the fault resistance has a great effect on the peak value of the overvoltage, while the converter blocking, grounding scheme and line protection have little effect. Finally, the overvoltage of single pole to ground fault and bipolar fault are summarized and compared.
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XUE Shimin, LIU Cunjia, LI Zheng, LU Junchi, ZHU Xiaoshuai
Available online:January 14, 2020 DOI: 10.7500/AEPS20190529006
Abstract:At present, the protection schemes of DC microgrid mostly depend on the fast breaking ability of DC circuit breakers at both ends of the line and the reliability of communication equipment. However, at this stage, the cost of DC circuit breakers is high, and the communication between the two ends of the line will greatly increase the construction and operation cost of DC microgrid. Based on the above background, this paper proposes a single-ended ranging protection technology based on control and protection cooperation for the four-terminal ring DC microgrid system. This method can be divided into two stages: fault control and protection implementation. In the phase of fault control, the fault current of DC line is controlled to be zero by changing the active control strategy of voltage source converter (VSC) itself and the external controllable elements. In the phase of protection implementation, based on the periodicity (20 ms) of the output voltage on the DC side of VSC after active control and the controllability of power electronic components, the unique loop between VSC and fault point is constructed. Then the single-ended fault location without error can be realized based on the traditional R-L algorithm. Differential fault location will lead to continuous zero-crossing of line current. On this basis, fault isolation can be achieved by fast disconnector. Based on the idea of control and protection cooperation, this method eliminates the interference of terminal current in single-end fault location of ring network system, and there is no need to configure DC circuit breakers at both ends of the line. Fault isolation can be achieved only by using fast disconnector and fault control strategy to cooperate logically in time sequence. Finally, a four-terminal ring DC microgrid system model is built on the PSCAD/EMTDC simulation platform, which verifies the effectiveness of the control and protection scheme.
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HUANG Xinyu, ZHANG Jiakui, XU Qianming, CHU Xu, WANG Yichao
Available online:January 14, 2020 DOI: 10.7500/AEPS20190730005
Abstract:To solve the problem of lack of freedom of power flow control in multi-terminal DC transmission system, a modular DC power flow controller (DCPFC) is proposed, which adopts modular structure to facilitate the expansion of multiple lines and has the ability of DC fault current limiting. Firstly, the topology of DCPFC is introduced, and its equivalent circuit model is established, while the principles of power flow control and fault current limiting are described. Then the power transfer characteristics of bridge arm of DCPFC in the power flow control mode are analyzed, and the power balance mechanism of bridge arm based on AC circulation is studied. On this basis, the power distribution control and power balance control methods of DCPFC are proposed, and their control strategies in the fault current limiting mode are illustrated. Finally, a three-terminal DC transmission system is built in PLECS simulation software to verify the effectiveness of DCPFC in the conditions of power flow distribution, power flow reversal, power step and fault current limiting.
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HAO Liangliang, LI Weijie, WANG Zhuoya, GU Yaqi, WANG Guang
Available online:January 13, 2020 DOI: 10.7500/AEPS20190729015
Abstract:As an effective means to support the adoption of high proportion of renewable energy, MMC-HVDC has become an important direction of power grid development. The pole-to-pole fault is the most serious fault in transmission lines. At present, state equations of DC system are usually written in the s domain, and then fault currents are solved based on the Inverse Laplace Transformation,while a practical engineering calculation method for fault current is needed urgently. In this paper, Zhangbei MMC-HVDC grid is taken as the research object, the fault characteristics and coupling mechanism of DC polo-to-pole fault are analyzed firstly. On this basis, the two ends of the fault lines near the valve side are regarded as two-ports respectively, the relationship between the fault currents and the voltages of the two-ports are analyzed. Secondly, based on the idea that the voltage of the two ports of the positive and negative lines does not change much, the annular MMC-HVDC grid is simplified to a two-terminal system or an open system. The practical calculation method of fault line current is obtained to calculate fault current directly, while it is no longer necessary to solve the high order Inverse Laplace Transformation. Finally, the feasibility and efficiency of the practical calculation method are verified by comparing with the electromagnetic transient simulation results.
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Song zhao, SHU Dewu, yan zheng, Luo Xiao
Available online:January 13, 2020 DOI: 10.7500/AEPS20190805005
Abstract:In order to accurately simulate dynamics of large-scale AC/DC grids and interactions between individual components, a simulation method with high precision and efficiency is highly required. To revolve these issues, a multi-domain simulation method combining phasor- and time-domain models is proposed. In this method, the DC grids are partitioned into the phasor subsystem, which are presented by their phasor models. This method can adopt large time-step to improve the efficiency while the accuracy is guaranteed. Further, a multi-domain interface model between different subsystems is proposed. The interface model can reflect both instantaneous and wide-band phasor waveforms simultaneously. Finally, a practical AC/DC system integrating four terminal VSCs in China has validated the effectiveness of the proposed method.
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LI Binbin, ZHANG Yujie, ZHANG Shuxin, ZHAO Xiaodong, XU Dianguo
Available online:January 13, 2020 DOI: 10.7500/AEPS20190730002
Abstract:As the key equipment for the future DC power grid, the high-voltage and high-capacity DC/DC converter has become the hot research topic in recent years. This paper proposes a hybrid DC/DC converter topology combing thyristors with half-bridge sub-modules. The hybrid DC/DC converter can block the short-circuit faults on the high-voltage and low-voltage sides by latching sub-modules and thyristors, and has the advantages of low cost and high efficiency. The working principle, fault protection mechanism, control strategy, parameter design and economy of the topology are analyzed and demonstrated. Finally, the feasibility of the proposed topology and control strategy are verified by simulation results based on MATLAB/Simulink.
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Cui Liangjie, SUN Yi, LIU Yaoxian, WEN Yafeng
Available online:January 13, 2020 DOI: 10.7500/AEPS20190225006
Abstract:Load monitoring is an important part of intelligent electricity consumption. A non-intrusive load decomposition method considering time-phase behavior is proposed considering the problem that existing low frequency non-intrusive load decomposition methods require more priori information and have lower accuracy for load with similar or low power. Firstly, power data of the load device is clustered to construct a load state template.An intelligent optimization method for the typical behavior time period that does not require a specified number of time periods is proposed. Load state behavior law is extracted by time-phase to construct a load behavior template. On the basis of the traditional power characteristics, considering the two dimensions of probability and time, the time-phased state probability factor (TSPF) is introduced into the objective function as a new load characteristic, and the load decomposition is realized by multi-feature genetic optimization iteration. Finally, the validity and accuracy of the method are verified on the public data set.
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LI Guoqing, BIAN Jing, WANG He, SUN Yunhe, WANG Zhenhao
Available online:January 13, 2020 DOI: 10.7500/AEPS20190607003
Abstract:Fault current limitation in DC power grid has become one of the important problems that must be faced and urgently solved in related fields. Most of the existing fault limitation methods adopt single component. In order to fully limit the rising rate and peak value of fault current, this paper proposes a fault limitation and optimal configuration method combining the characteristics of DC reactor and capacitive current limiter. Firstly, based on the fault equivalent circuit of modular multilevel converter, the necessity of installing fault current limiter is analyzed from two aspects of limitation principle and action sequence. Secondly, the limitation characteristics of inductance and capacitance to fault current are calculated and analyzed, and the equivalent circuit and solution method are extended to DC ring grid. The optimal configuration model is constructed with the objective of fault current and DC reactor. Finally, the optimization results are applied to PSCAD/EMTDC simulation model. Compared with the scheme using DC reactor only, the configuration results can further reduce 40% of the fault current without prolonging the fault clearance time. It is verified that the combination of DC reactor and capacitive current limiter can significantly reduce the fault current and the breaking capacity of DC circuit breaker.
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LI Zhendong, AN Haiqing, FAN Xiaowei, YANG Dawei, YANG Minxiang, ZHANG Jianpo
Available online:January 13, 2020 DOI: 10.7500/AEPS20190715003
Abstract:Abstract: The symmetrical and bipolar flexible high voltage direct current(HVDC) transmission system has higher transmission capacity and higher reliability than the monopole system. Therefore, it is gradually being applied to practical engineering. In view of AC/DC outlet ground faults of modular multilevel converter in bipolar systems, the transient characteristics of voltage and current after converter fault blocking were studied, and the mathematical analytical formula of the fault component was derived. The research results show that a single phase-to-ground fault in the AC outlet lead to the up-arm of blocked converter on the non-fault phase over-voltage and the lower-arm over-current on the non-fault phase. And the DC bias on the AC-side current causes the fault phase short-circuit current to have no zero-crossing. When the DC outlet occurs a pole-to-ground fault, the short-circuit current of the bridge arm of the blocked converter is mainly composed of the steady-state current injected by the AC system and the circulating current between the upper and lower arm. A phase-selective trip protection strategy is proposed for this special fault characteristic of single-phase ground fault at AC outlet. The problem that the AC circuit breaker cannot be normally opened when the zero-crossing point of the fault current does not exist is solved.A simulation model of the zhangbei flexible DC grid was built. The simulation results show that the analysis of the fault characteristics in the converter outlet is accurate and the proposed strategy is effective and feasible.
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19、Current Calculation Method of Short-circuit Fault at DC Side for MMC Based Two-terminal TWBS-HVDC
LI Guoqing, LIU Xianchao, ZHANG Song, JIANG Tao, CHEN Houhe, LI Xue
Available online:January 13, 2020 DOI: 10.7500/AEPS20190601001
Abstract:The three wires bipole structure based high voltage direct current (TWBS-HVDC) system can greatly enhance the transmission capacity of the DC lines, which has become an effective method for converting AC line into DC line and lines capacity improvement. Aiming at the difference between TWBS-HVDC and bipole direct current system in connection ways, a DC side short-circuit fault current calculation method for TWBS-HVDC system was proposed. Firstly, the transient equivalent model of TWBS-HVDC system was established based on MMC transient equivalent circuit. The number of independent circuits and the order of dynamic components in the transient equivalent circuit were taken as the standard, all DC faults were classified into three categories, and the state equations of each kind of fault was analyzed and deduced. The analytical expression of fault current was obtained by solving the eigenvalue and eigenvector of coefficient matrix in the state equation. Finally, a two-terminal TWBS-HVDC system simulation model was established in the MATLAB/Simulink digital simulation platform, and the simulation results validated the effectiveness and accuracy of the short-circuit fault state equation solution method on the DC side of the TWBS-HVDC system proposed in this paper, which can provide a scientific basis for the selection of system main circuit parameter and the setting of relay protection action time.
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LIU Shuo, SU Jianhui, LAI Jidong, ZHANG Jian, WANG Haining
Available online:January 10, 2020 DOI: 10.7500/AEPS20190408002
Abstract:The calculation of voltage gain-frequency characteristic is vital in the design of LLC resonant converter. The LLC converter have various operation modes due to the existence of nonlinearity in the rectifier part of the converter. And the voltage gain-frequency characteristic is closely related to operation modes. The PO mode is a discontinuous conduction mode (DCM), which is beneficial to reduce switching losses of the converter. However, the voltage gain-frequency characteristic of converter in the PO mode is hard to be worked out because it involves complex computations. On the basis of subinterval analysis method, this paper analyzes the operation characteristics in the PO mode of LLC resonant converter, and deduces a simplified and high-accuracy calculation formula of voltage gain. In addition, the parsing and concise expressions of power boundary conditions both in DCM mode and PO mode are provided in accordance with nonlinear characteristic in rectifier part of the converter. A simulation model and an experimental prototype of LLC converter are developed, and the simulation and experiment results verify the validity of the deduced voltage gain formula and power boundary condition.
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WANG Yongzhen, ZHANG Ning, Guan Yonggang, ZHAO Wei, ZHANG Jing, GAO Feng, KANG Chongqing
Available online:January 06, 2020 DOI: 10.7500/AEPS20190710007
Abstract:Energy Internet (EI) is an emerging field that integrates cooling, heating, power and gas among physical flow, information flow and value flow. The projects supported by National Natural Science Foundation of China can reflect the trend of research focus on EI in China. In this paper, the NSFC funds in EI are comprehensively analyzed from the view of research directions, annual approved quantities, universities and the fund type. The results show that EI extends the research from Smart Grid (which centers on electricity) to multiple energy system integration cooling, heating, power and gas. Predominant universities that in the lead position in electrical science and engineering and engineering thermo-physics and energy utilization have shown their advantages in the research of EI; The funds of EI show strong multi-disciplinary among the electrical engineering, electronics and information systems, computer science, automation, management science and engineering, mathematics, building environment and structure, macro management and policy of multi-disciplinary.
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LIU Ding, ZHAO Defu, BAI Muren, WANG Qiqing, LI Cunbin
Available online:January 06, 2020 DOI: 10.7500/AEPS20190117001
Abstract:Real-time electricity trading in electricity spot market can give full play to market regulation and promote the accommodation of renewable energy. Data empirical research on the impact of renewable energy generation on real-time electricity price has an essential reference value for understanding the operating rules of the spot market and evaluating market maturity. In this paper, German electricity spot market is selected to conduct data empirical research on the impact analysis of renewable energy power generation on real-time electricity price. Data of power generation, load, prediction error, price and other factors are collected to implement the time series feature representation method. Firstly, the time domain models of time series are transformed into feature vectors using the feature representation method. Next, the greedy forward feature selection algorithm is used to extract key features to maximize the differences between factors. Then, the correlation among multiple factors is discussed based on the overall features and key features respectively, and the network of influence mechanism is constructed. The empirical results show that the real-time electricity price in the German electricity spot market is mainly affected by the wind power generation prediction error, and the correlation between factors mainly comes from features such as Fourier transform, wavelet transform and discrete symbolization. Finally, through the simple comparison between China and Germany, it is pointed out that the real-time electricity price in Guangdong electricity market is more affected by the randomness of renewable energy generation than by the prediction error.
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XU Fangwei, WANG Chuan, YANG Honggeng, XU Lin, ZHAO Jinshuai, WANG Yang
Available online:December 27, 2019 DOI: 10.7500/AEPS20190824004
Abstract:All the existing quantification methods of harmonic responsibility of distributed multiple harmonic sources use the external port current (hereinafter referred to as the port current of harmonic source) of the harmonic source equivalent circuit (Norton equivalent model in common use) to calculate the harmonic contribution of the harmonic source to the concerned bus. Since the harmonic source port current is constrained by the Kirchhoff’s law, as long as the harmonic source port current changes in the power grid, the harmonic contributions of all harmonic sources to the concerned bus will change accordingly. However, the harmonic source port current is usually the result of the coupling of harmonic source and background harmonic, so the harmonic contributions calculated by this current cannot truly reflect the harmonic emission level of the harmonic source. Therefore, this paper quantifies the harmonic responsibility of each harmonic source to the concerned bus by harmonic source current itself rather than harmonic source port current. The proposed method directly solves the complex harmonic voltage contribution of each harmonic source to the concerned bus, and it does not need to solve the harmonic transfer impedance of the harmonic source to the concerned bus, which reduces the effect of cumulative errors, can more fairly and reasonably reflect the harmonic responsibility of each harmonic source. The effectiveness and accuracy of the proposed method are verified by simulation and experimental example.
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LI Bin, WANG Chenyang, HE Jiawei, YE Shilei
Available online:December 24, 2019 DOI: 10.7500/AEPS20190418012
Abstract:In order to eliminate the adverse effects of conventional current-limiting reactance on the operation stability of DC system and the breaking speed of DC circuit breaker, the bridge current-limiting solid-state circuit breaker has achieved excellent performance of both adaptive fault current limiting and breaking. However, the DC bias power supply in the bridge circuit has the shortcomings of no overcurrent protection and relatively high power capacity and investment cost. For the bridge-type current-limiting solid-state circuit breaker, this paper designs a DC bias power supply based on three-phase half-wave rectifier circuit. The method of selecting the parameters of bias power supply and setting the voltage is put forward, which effectively reduces the number of power electronic devices, realizes the over-current protection circuit of bias power supply, and reduces the designed capacity and cost of bias power supply. The prototype experiment and simulation examples verify the advantages of the proposed bias power supply of self-adaptive current-limiting solid-state circuit breaker.
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ZHANG Yachao, HUANG Zhanghao, ZHENG Feng, LE jian, SHU Shengwen, XIA Pei
Available online:December 24, 2019 DOI: 10.7500/AEPS20190411006
Abstract:With the continuous expansion of renewable energy installation capacity and the persistent advancement of integrated energy system research, the gas-fired units deepen the integration of power system and natural gas system as the coupled components and provide a new way for renewable energy accommodation. Since the stochastic programming method, interval optimization and robust optimization algorithms have their own shortcomings in dealing with wind power uncertainty, a distributionally robust optimization approach based on the ambiguity set of wind power prediction error is proposed to solve the collaborative dispatch problem for power and natural gas coupled system. First, the principal component analysis is adopted to extract the temporal-spatial scale correlation characteristics of high-dimensional prediction error vector, and a series of moment functions are introduced to describe the distribution information of prediction errors to construct the corresponding ambiguity set. Then, a two-stage distributionally robust optimization dispatch model is established. The first stage is used to make the unit commitment decision, power output and reserve configuration by units, and the second stage is used to identify the worst-case distribution of wind power to ensure the effectiveness of the scheduling strategy determined in the first stage. Combining the linear decision rule and dual theory, the above semi-infinite optimization problem can be transformed into a finite-dimensional optimization problem. Finally, the simulation results verify the validity of the proposed model and solution method.
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LIU Wenxuan, ZHAO Junhua, HUANG Jie, WEN Fushuan, LU Zhe, XUE Yusheng
Available online:December 24, 2019 DOI: 10.7500/AEPS20190116002
Abstract:The cyber-physical-social system (CPSS) is applied to describe the characteristics and interactions of cyber space, physical systems and social agents in complex networked systems, and is designed to provide systematic modelling, inference and decision making. Human behavior modeling has always been a complex problem in CPSS. Based on the historical and simulated data, this paper employed the generated adversarial network (GAN) for social behavior modelling under uncertainty. Additionally, the hybrid simulation is applied to derive the practical problem in the Guangdong electricity spot market, namely the potential impact of gas unit subsidies on the market.
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ZHU Tiechao, NIE Yixiong, LI Zhe, LIN Xiuyue
Available online:December 24, 2019 DOI: 10.7500/AEPS20190430012
Abstract:Stray capacitance is an indeterminate factor affecting the harmonic measurement of capacitive voltage transformer (CVT). By analyzing the internal structure of CVT and the calculation formula of stray capacitance, it is found that the stray capacitance is a random interval-type parameter. In order to improve the fitting precision of harmonic transfer characteristic curve of CVT, this paper proposes a method based on improved particle swarm optimization algorithm for parameter estimation of stray capacitance of CVT. The method takes the confidence interval of the input parameters as the condition, and takes the minimum error of calculation result as the goal. The parameter combination of the stray capacitance is determined under the condition that the requirements of amplitude and the minimum error of phase shift are satisfied and the confidence interval are as much as possible. Through the establishment of a comprehensive power quality test platform, the harmonic voltage value of the secondary side of a 35 kV resistive capacitive divider voltage transformer (RCVT) is used as a reference to analyze the error of the actual harmonic voltage value of the TYD35/√3-0.02HF CVT and the harmonic voltage value corrected by the amplitude-frequency curve relative to the reference value. The validity and feasibility of the proposed method are verified.
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WANG Yi, SUN Yonghui, NAN Dongliang, WANG Kaike, HOU Dongchen
Available online:December 24, 2019 DOI: 10.7500/AEPS20190325004
Abstract:The uncertainties of noise statistics and model parameters will seriously affect the accuracy of dynamic state estimation. To deal with this issue, in this paper, a new dynamic state estimation approach is developed based on H infinity cubature Kalman filter. Firstly, the dynamic state estimation model of generator is established. Secondly, a rule for model uncertainties is developed by utilizing the H infinity filtering theory, based on which, the estimation error covariance matrix in the cubature Kalman filter can be updated, to suppress the adverse effects on the precision of state estimation caused by parameter uncertainties. Finally, the performance of the proposed method is compared with the CKF and an improved interpolation extended Kalman filter in IEEE 10-machine 39-bus system and a large practical power system. Simulations results demonstrate that HCKF performs better than CKF and IEKF methods in estimation precision and robustness against model uncertainties, which can restrain the influences of model uncertainties on the dynamic state estimation for generators.
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Available online:December 24, 2019 DOI: 10.7500/AEPS20190612009
Abstract:Non-intrusive load monitoring (NILM) is an effective way to realize demand side measurement and energy efficiency optimization. This paper explores an online NILM method in high-frequency acquisition mode, which ensures the entire process automated and real-time. Firstly, a load-decomposition model is established based on the load current additivity to obtain the independent load waveform. Then, the load type is judged by Bayesian classification according to the operational signatures of the load, and the dynamic load signature databases are adaptively constructed for independent users without recording the prior data. Finally, load identification is realized by fast optimization for current waveforms in the dynamic signature database, so as to acquire the electricity consumption of load in real time. The data measured in actual scenario is used to verify the effectiveness of the method. According to the experiment, the method can adaptively construct the dynamic signature database for different users, which improves the weak universality caused by establishing the database in advance. The fast optimization based on the signature database ensures the efficient and accurate identification.
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TAN Xiao, WANG Zhuding, LI Qiang, PANG Xianglu
Available online:December 24, 2019 DOI: 10.7500/AEPS20190610004
Abstract:The large number of distributed generations brings risks to the power quality of the network which they are connected to. Thus it is instructive for DGs planning to evaluate the maximum hosting capacity of DGs access to a distribution network. An optimization model for evaluating the hosting capacity is established. In the model, the goal is to maximize the grid-connected capacity of distributed generation, and the constraints involve the technical standards of voltage deviation, voltage fluctuation, short-circuit current and relay protection. Based on the sensitivity of a constraint index to DG capacity, a single-constraint segmentation algorithm and a multi-constraint coordination segmentation algorithm are proposed for the model. Based on the different initial values of DG capacities, the segmentation algorithms can be carried out respectively in backward and forward ways. In the end, the maximum hosting capacity of a radial distribution network under multiple constraints, multiple sources and multiple DG types is computed and analyzed, which shows the superiority of the proposed algorithms in calculation accuracy and efficiency.
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NIAN Heng, ZHU Maowei, XU Yunyang, CHEN Liang, ZOU Changyue, XU Shukai
Available online:December 24, 2019 DOI: 10.7500/AEPS20190328002
Abstract:The wind power integration via the modular multilevel converter (MMC) based high voltage DC (HVDC) transmission system is a promising scheme for power transmission, which also faces prominent stability problems. The small-signal impedance analysis method is an effective way to study the stability of interconnected systems. However, it is difficult to accurately build the impedance model of MMC due to its internal dynamic characteristics. By using the multi-harmonic linearization method, this paper develops a small-signal impedance model of the sending-terminal MMC with double closed-loop AC voltage control. Then the influence of current control loop on impedance characteristics is analyzed accurately. For the system in which the wind farms consisting of permanent magnet synchronous generator (PMSG) are connected with MMC-HVDC system, the impedance analysis method is applied to analyze the oscillation of the interconnected system with different bandwidth of current control loop of MMC, which provides a basis for optimal parameter design of current control loop. The simulation results based on MATLAB/Simulink validate the correctness of the impedance model and stability analysis.
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SUN Wei, YU Hao, YANG Jianping, GAO Bo, WANG Yu, QIN Shaorui
Available online:December 18, 2019 DOI: 10.7500/AEPS20190124005
Abstract:In some Wireless Sensor Network (WSN) applications of the smart grid, increasing transmission power (signal strength) will improve the reliability of communication, however, in the meanwhile, it will lead to an incensement of energy consumption and electromagnetic interferences between nodes. To this end, this paper studies the optimization of transmitting power of WSN based on the adaptive model predictive control. Firstly, based on the discretized model of wireless communication path loss, the main factors affecting the received signal strength of WSN are analyzed, and the system state space model is constructed. Then, based on the incremental model that is transformed by the system state space model, the prediction equation of the system is derived. Finally, the proposed algorithm with ATPC and PFC algorithm for comparison and analysis are carried out by simulation and hardware testbed. The results show that the proposed adaptive model predictive control algorithm can guarantee the reliability requirement of hardware platform under the different conditions. Besides, a better node energy consumption and a higher received signal strength are achieved.
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CHEN Zhengping, MEI Zheng, LIN Jinghuai, MI Weimin, LI Xitai, YU Sihang
Available online:November 30, 2019 DOI: 10.7500/AEPS20190408005
Abstract:As the integration characteristics of power grid operation become prominent, the application business links between various levels of regulatory agencies are becoming increasingly close, and the demand for information sharing and data interaction is becoming more and more urgent. In order to achieve integrated and coordinated operation, the power grid dispatching control system needs to interact with a large number of real-time data and non-real-time data between different dispatching agencies and business applications. However, the current technical scheme is mainly aimed at the data interaction between real-time services, and there is no universal data interaction mechanism in quasi-real-time/non-real-time business scenarios. According to the above problem, this paper puts forward the regulation of business oriented, quasi real-time/non real-time data across institutions and across the safe zone, cross-platform integrated exchange of architecture, the establishment of a canonical data interaction processes and operating mechanism based on task, to realize unified management of data interaction process. At present, the research results have been applied in engineering, which support the integration of provincial, regional and station.
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FENG Zhuocheng, WAN Kaiyao, JIANG Tong
Available online:November 30, 2019 DOI: 10.7500/AEPS20190301001
Abstract:In order to calculate the steady voltage stability margin rapidly and precisely, an algorithm based on asymptotic numerical method is proposed. By analyzing the equations formulated by the voltage collapse point, the general formula of the high-order partial derivatives of the voltage stability boundary are obtained. Based on the asymptotic numerical method, the relationship between the fitting error and the boundary area is analyzed. The method avoids the multiple traditional flow calculation with higher accuracy and lower time cost.On the other hand, the factor table of the existing coefficient matrices can be reused when calculating the high-order partial derivatives, which decreases the calculation burden. The related applications based on the method are presented. Testing examples based on IEEE 118 node system are established to verify the effectiveness of this method at length.
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WANG Yibo, CAI Guowei, LIU Chuang, GUO Dongbo, WANG Peng, ZHU Bingda
Available online:November 19, 2019 DOI: 10.7500/AEPS20190409006
Abstract:Dynamic voltage restorer (DVR) is a power electronic device connected in series with source and load, which is used to rapidly compensate voltage fluctuation in the power system. However, due to the energy storage equipment, the conventional DVR based on voltage source inverters (VSIs) has some shortcomings. And DVR based on direct AC/AC conversion with pulse width modulation (PWM) has the shortages of commutation problem and voltage balance of flying capacitor. Therefore, this paper proposes a single-phase DVR based on bipolar direct AC/AC conversion. The AC/AC converter topology with PWM used in the proposed DVR has the characteristics of common grounding between the input and output ports. In addition, the proposed DVR can achieve bipolar voltage regulation under a simple control strategy and solve the commutation problem during operation effectively. In order to verify the engineering value of the proposed DVR, a 1 kW experimental platform has been built to verify its rationality and effectiveness on the basis of theoretical analysis.
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ZU Guoqiang, XIAO Jun, MU Yunfei, ZHU Xiaohui, YAO Ying, JI Dalong
Available online:November 19, 2019 DOI: 10.7500/AEPS20190617001
Abstract:The China urban power grid is evolving to smart distribution grid, of which the operating circumstance will be more complicated. Security region is a new method for the distribution system operating. This paper studies the smart distribution system security region (DSSR) from the view of user load, taking two main elements into account, which are distributed generation (DG) and demand response (DR). Firstly, it analyzes and formulates the characteristics of security operating for distribution systems with DG and DR then the DSSR with DG and DR is modeled. It observes the DSSR 2D sections on case grids and studies the mechanism of DG and DR on DSSR, based on which the guidance for the distribution system planning and operating is proposed. The DSSR in this paper is consistent with the usual practice of dispatchers and could be a useful tool of the security monitoring and analysis for urban power grids, in which the user load service is more important than the service of DG and DR.
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Available online:November 13, 2019 DOI: 10.7500/AEPS20190326002
Abstract:In recent years, the omnidirectional wireless power transfer technology has been widely concerned by domestic and foreign research institutions and research institutes due to its unique advantages such as good location robustness, high safety and reliability, and strong environmental affinity. Firstly, the application field of omnidirectional wireless power transfer technology and the development at home and abroad are described. Then, the key fundamental problems of the electromagnetic coupling system are analyzed in detail, including the design and optimization of the electromagnetic coupling structure, magnetic field direction control strategy and electromagnetic compatibility. Finally, the key problems and technical difficulties to be solved in engineering, productization and commercialization of the technology are discussed, and its application prospect is further prospected.
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WANG Jinning, WANG Lei, HAN Xiaoqing, MENG Runquan, GUO Haixia
Available online:November 13, 2019 DOI: 10.7500/AEPS20190409002
Abstract:A model of the AC/DC converter based on the harmonic state space (HSS) theory is developed, and the AC/DC harmonic coupling characteristics of the converter have been analyzed in depth. Firstly, through the mathematical derivation, the three-phase AC/DC converter is modeled based on the HSS theory. The HSS model includes each harmonic on the AC and DC sides, which reflects the relationship between the harmonic variables of each frequency. Secondly, the harmonic transfer function of the converter is deduced by the model, and the diagram of harmonic coupling impedance is established to analyze the AC/DC harmonic coupling characteristics. The model is built according to the voltage source three-phase AC/DC converter which is commonly used in microgrids. The full range of coupling characteristics between AC and DC side is illustrated, and can be used to explore the harmonic characteristics at all frequency, and can also be applied in harmonic analysis of converter with parallel and cascaded structures. Finally, the simulation of the voltage source three-phase AC/DC converter is performed in PLECS, and it is compared with the HSS calculation results to verify the proposed model and the study of harmonic coupling characteristics. Furthermore, the proposed model and the conclusion of harmonic coupling characteristics are verified by experiments.
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LIANG Deliang, LIU Yibin, KOU Peng, CAI Shengliang, ZHOU Kun, ZHANG Mingkang
Available online:November 04, 2019 DOI: 10.7500/AEPS20190507007
Abstract:The intelligent distribution transformer is a key device to construct the future intelligent distribution network, and its importance is highlighted by the fast development of the smart grid. This paper introduces the main functions of the intelligent distribution transformer in the presence of distributed renewable power generation and AC/DC hybrid distribution power system, and states that the key issue of the intelligent distribution transformer is the high controllability, which can be achieved by utillizing the power electronic devices. Considering this fact, two alternative circuit schemes for the intelligent distribution transformer based on the power electronic transformer (PET) and hybrid distribution transformer (HDT) are dicussed. The basic working principle of PET and HDT are introduced, and the several typical topologies of the intelligent distribution transformer based on PET, HDT and the extended HDT are presented and analysed. Based on a specific application scenario in the distribution network, the working principle, reliability, economy, controllability of the intelligent distribution transformer based on PET and HDT are compared, and the variation trend of each performance is presented when the ratio of the conversion power is increasing. Finally, the future developing trend of the intelligent distribution transformer are analysed.
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LONG Kaihua, LI Xiaoqian, LI Ziming, XIE Xiaorong, CAI Wei, HUANG Jinkui
Available online:November 01, 2019 DOI: 10.7500/AEPS20190408013
Abstract:In order to prevent the trip of modular multilevel converter (MMC) due to block, the rising speed of DC short-circuit current should be limited. The active current-limiting control of MMC is a new current-limiting method, which can limit the DC short-circuit current by reducing the discharging time of capacitor without extra cost. The existing calculation method of DC short-circuit current cannot reflect the change of circuit structures and parameters caused by active current-limiting control. This paper proposes a calculation method of DC short-circuit current considering active current-limiting control of MMC. A duty circle index for discharging state of capacitor is introduced to represent the effect of active current-limiting control on DC short-circuit current. The state equation of DC short-circuit current is built based on state space averaging method, and the time-domain analytical expression of DC short-circuit current is given. The effectiveness of the proposed calculation method is validated by the simulation results based on PSCAD/EMTDC.
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XIE Jiping, ZHANG Wen, YANG Hao
Available online:October 31, 2019 DOI: 10.7500/AEPS20190403005
Abstract:Compared with the conventional single-layer connection mode of ultra-high voltage direct current (UHVDC) system, the hierarchical connection mode improves the ability of AC system in acceptance and providing voltage support for multi-infeed UHVDC systems from the aspect of grid structure, and it makes power flow distribution and control more flexible and reasonable. In order to make full use of the fast power adjustment capability of UHVDC systems in the hierarchical connection mode, and avoid or reduce the economic loss caused by the load shedding during the medium-term and long-term voltage instability process, this paper proposes a coordinated control method for AC/DC power systems with hierarchical connection of UHVDC systems. Firstly, based on the quasi-steady model of UHVDC system in the hierarchical connection mode, this paper deduces the analytical expressions of sensitivities of the converter bus voltages with different control mode of UHVDC systems to the inverter transmission powers of UHVDC systems in hierarchical connection mode. Secondly, the voltage trajectory prediction model of AC/DC system is established based on the derived sensitivities. Finally, considering modulations of the DC current and the extinguishing angle of high and low ends of the inverter, a receding horizon optimization model of coordinated voltage control is constructed based on the predicted trajectory. The hierarchical DC injection powers and the voltage control means of AC system are coordinately controlled. The simulation analysis of the planning system of Shandong power grid shows that the proposed method can effectively coordinate the distribution of DC transmission power in AC grid, which enhances the system voltage stability and reduces the load shedding loss.
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JIANG Chongxi, SHI Peng, HUANG Wei, ZHOU Jinghao, GAN Deqiang
Available online:October 30, 2019 DOI: 10.7500/AEPS20190117007
Abstract:Installing Power System Stabilizer (PSS) is an effective means to enhance power system stability under small disturbances. Compared with the traditional single-band power system stabilizer, the multi-band power system stabilizer (PSS4B) has more frequency band branches and higher control degrees of freedom, which can better suppress the oscillation mode with lower frequency, but its tuning process and method have not been widely reported. In this paper, a PSS4B parameter tuning method based on the frequency domain margin index of multi-input-multi-output system is proposed. The method considers several weakly damped oscillation modes in the performance index, adjusts the amplitude-frequency and phase-frequency characteristics of multiple PSS4Bs, guarantees the designed PSS4B maximize the system stability margin while providing suitable compensation phase, and ensures the stability of the excitation mode. Case studies of Yunnan Grid validate the proposed design method.
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ZHANG Yanke, LIU Yuan, JI Changming, ZHANG Jiaxin
Available online:October 30, 2019 DOI: 10.7500/AEPS20190411007
Abstract:In the operation optimization of cascade hydropower reservoirs, it is a usually simplified way that neglecting time-lags of flow routing and regarding the upstream reservoir outflow as the downstream reservoir inflow, which have an impact on accuracy of operation scheme when time-lag is big enough. In order to reduce the effect of time-lags of flow routing, firstly, the relationship between upstream reservoir outflow, local inflow, downstream reservoir water level and downstream reservoir inflow is quantized based on the principle of linear space. Secondly, the artificial neural network, Kmeans and Relief methods in date mining are comprehensively applied to solve and determine the mapping relationship. And then, a short-term generation optimization model of cascade hydropower reservoirs considering time-lags of flow routing is established. Finally, to verify the feasibility and effectiveness of the model, it is applied to solve the operation optimization of cascade hydropower reservoirs in Yalong River, and the results show that the established model can considerably improve the accuracy of short-term optimal operation plan. So it can give full play to the utilization efficiency of water resources, and provide reference for actual operation.
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QU Zhaoyang, ZHAO Tengyue, ZHANG Yu, QU Nan, LIU Yuqing, SUN Jiani
Available online:October 29, 2019 DOI: 10.7500/AEPS20190227002
Abstract:Due to the inhomogeneity of power CPS network and the dynamics of risk propagation process, it is difficult to determine the critical point of risk outbreak. From the perspective of dependent network, this paper proposes a method for determining the risk propagation threshold of power CPS network based on seepage theory. Firstly, according to topological Association and coupling logic, the power CPS network is abstracted as a dual layer complex network with directed unauthorized graph, and asymmetric balls-into-bins distribution method is used to establish "one to many" and "partial coupling" CPS characterization models for non-uniform electric power. Then, consider the directionality between the information layer and physical layer links, Introducing the seepage probability to establish the propagation dynamics equation for each layer"s internal coupling relationship. Finally, the risk propagation threshold is solved by defining the survival function of the nodes in the power CPS network, and the effectiveness of the proposed method is verified by an example of IEEE30 node system and 150 node Barabsi-Albert model.
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GE Xiaolin, HAO Guangdong, XIA Shu, FU Yang
Available online:October 29, 2019 DOI: 10.7500/AEPS20190227003
Abstract:The randomness of large-scale electric vehicles connected to the grid and wind power output increases the difficulty of safe and economic operation of the power system. In view of the unpredictable characteristics of wind power output, and taking into account the operational benefits of power grid side and electric vehicle aggregator side, a robust two-layer stochastic optimal scheduling model of wind power, thermal power and electric vehicles is established. In the model, in order to improve the solution efficiency, the interaction between electric vehicles and the power grid is constructed based on the approximate Benders algorithm. In addition, in order to solve the problem that it is difficult to coordinate and optimize between large-scale electric vehicles, the coupling relationship between individuals of electric vehicles is coupled by using the principle of auxiliary problem, and the joint optimization of electric vehicle groups is transformed into the parallel computing of single electric vehicle scheduling, which realizes the individual scheduling of electric vehicle. Finally, the simulation analysis of the improved IEEE39 node is carried out to verify the effectiveness of the proposed model and algorithm in solving the large-scale electric vehicle and wind power scheduling problem.
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WANG Shouxiang, GUO Luyang, CHEN Haiwen, DENG Xinyu
Available online:October 21, 2019 DOI: 10.7500/AEPS20190625010
Abstract:Aiming at the limitation of using single equipment features for load identification, we proposed a non-invasive load identification algorithm based on feature fusion and deep learning. Firstly, The V-I trajectory image features and power numerical features are extracted by analyzing the high frequency sampling data of the equipment. Then the fusion of V-I track image features and power numerical features is realized by using the advanced feature extraction ability of ANN. Finally, the BP neural network is trained to identify equipment by using fusion feature as the new feature of the equipment. We used PLAID data set to verify the identification performance of the algorithm, and compared the performance of different classification algorithms for feature fusion and load identification ability. The results show that the proposed algorithm makes use of the complementarity of different features, overcomes the disadvantage that V-I track features cannot reflect the power of the equipment, and improves the load identification ability of V-I track features. In embedded devices, the computing speed of proposed algorithms can reach the millisecond level.
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ZHAO Yitong, WANG Huifang, HE Benteng, XU Weina
Available online:October 21, 2019 DOI: 10.7500/AEPS20190507001
Abstract:In order to improve the economy of the investment and operation of user-side battery energy storage and reduce the cost of user power consumption, a rolling optimization method of user-side battery energy storage configuration and operation scheduling is proposed. Firstly, the benefit of users after installing energy storage and the constraints of energy storage operation are analyzed. Then the energy storage configuration optimization model, the energy storage optimization model before month and the rolling optimization model for intra-day operation are constructed and solved by CPLEX solver. Energy storage performance constraints are added to the model, which can effectively reduce the number of transitions between charging and discharging states and prolong the life of energy storage. In the pre-month optimization, a predicted monthly demand defense value is determined. In the intra-day rolling optimization, a subsection optimization model for daily operation of energy storage and a renewal model for monthly demand defense value are constructed. The daily load data and monthly demand defense value are updated in real time, and the rolling optimization is carried out to continuously correct the impact of load forecasting error. Finally, a large industrial user is simulated to verify the validity of the model.
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WANG Xuhong, HU Jierui, FAN Shaosheng, YIN Lin
Available online:October 21, 2019 DOI: 10.7500/AEPS20190126006
Abstract:Aiming at the problems such as easy saturation of magnetic circuit and low acquired power of the widely used on-line power acquiring device of current transformer, this paper proposes an on-line power acquiring method combining dual magnetic circuit topology with resonant power control. In the dual magnetic circuit structure, a two-semicircle magnetic core is installed on the transmission line, and the excitation inductance in the magnetic circuit is resonant in parallel with the capacitance through the secondary-side connection capacitance, which increases the impedance value of the magnetic circuit. Thus, the current on the line is controlled to flow more into the other magnetic circuit coil of the dual magnetic circuit, through which the internal impedance is matched with the value of the external load, and the maximum power is obtained. Based on this method, an anti-saturation strategy of magnetic core controlled by excitation inductor and resonant capacitor is put forward, which make the device keep high power while work normally. The correctness of the method and the applicability for the circuit harmonic are verified by the joint simulation of Maxwell and Simplorer. The preliminary test shows that the power acquired by the dual magnetic circuit can meet the requirement of monitoring equipment of high voltage transmission line.
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SUN Yuwei, WU Chengjie, FU Chao, ZHANG Shuai, GAO Zhen
Available online:October 18, 2019 DOI: 10.7500/AEPS20190513001
Abstract:Power electronic transformers (PETs) are the key equipment in AC/DC hybrid distribution network. In order to improve the operation efficiency of cascaded PET under the condition of light-load, this paper proposes an efficiency optimization strategy based on active unbalanced power control, which utilizes the unbalanced characteristics of hybrid pulse width modulation (HPWM) technology. By analyzing the power losses of both cascaded H-bridge converter with HPWM and isolated bidirectional DC/DC converter, the operation efficiency model of cascaded PET is established. Based on the efficiency model, the feasibility for improving the overall efficiency of PET through unbalanced power distribution of each module is analyzed. The power stable operation range for each unit with HPWM is derived, and the active unbalanced power control strategy suitable for system efficiency optimization under the condition of light-load is proposed. Finally, the validation of the proposed strategy in comparison with the traditional power balanced control is confirmed by experiments, and the results show that the proposed unbalanced power control can reduce the power loss under the condition of light-load and improve the overall efficiency of PET.
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YIN Shuangrui, AI Qian, WANG Dapeng, DING Yongqing, WU Junhong, XIE Yinzhe
Available online:October 15, 2019 DOI: 10.7500/AEPS20190115002
Abstract:Under the rapid development of distributed renewable energy, the prosumers will become new important stakeholders to participate in the grid operation. Considering that the air-conditioning load of the prosumers has good regulation potential, the virtual energy storage (VES) model of air-conditioning load is first established, and the difference between VES and conventional energy storage is analyzed. Considering the characteristics of VES that can participate in intraday regulation and the uncertainty of renewable energy output, a day-ahead robust bidding strategy for prosumers is proposed. Furthermore, an optimal bidding and scheduling strategy combining day-ahead decision-making with real-time adjustment of VES is proposed. The improved column-and-constraint generation (C&CG) algorithm is used to solve the problem. Finally, the specific examples are compared, the results prove the advantages of optimal strategy in the flexible and economic operation of the prosumer. The impact of the uncertainty of renewable energy output, penalty price selection and out-door temperature on actual results is further analyzed.
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TANG Aihong, SHI Chengcheng, ZHENG Xu, XU Qiushi, HUANG Yong, ZHAO Hongsheng
Available online:September 24, 2019 DOI: 10.7500/AEPS20190430004
Abstract:Distributed power flow controller(DPFC) can flexibly improve the transmission capacity of existing lines and thus reduce operating cost of power system, however, the introduction of DPFC increases difficulties and non-convexity of traditional optimal power flow(OPF) problem. A simplified steady-state power model of DPFC is proposed based on its structure and working principle. The feasible region power of flow for line with DPFC in actual power grid is given considering the capacity of series unit of device in operation. On this basis, the semi-definite programming(SDP) method which is insensitive to the initial value is extended to establish the optimal model of system with DPFC, then the primal dual interior point method is used to solve the OPF problem. The test results show that the proposed method can solve the OPF problem with DPFC.
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GE Shaoyun, LIU Jingyi, LIU Hong, WANG Yiran, ZHAO Chenxiao, SUN Wei
Available online:September 24, 2019 DOI: 10.7500/AEPS20190303005
Abstract:A dispatch method with synergy and interaction between integrated energy hub and users was put forward aimed at the problems of failure to consider the thermal storage characteristics of building envelopes and demand response subsidy mechanisms for users during the operation and dispatch of integrated energy hub. First of all, a building virtual storage model was established with the indoor air and building envelope as the main part of heat transfer through comprehensive consideration of influences of indoor and outdoor disturbances on thermal process; secondly, a typical equipment composition structure of integrated energy hub with supply of cooling, heating and power systems and a multi-agent interactive transaction relationship among external power companies, integrated energy hub and users were established, and a stimulating demand response mechanism based on user subsidy was put forward; thirdly, an optimized economic dispatch model of integrated energy hub was established with the maximum earnings of power station as the target, containing external power purchase expenses, incomes through selling power to users, subsidies and start-up/shut-down costs and with the flexible comfort level of users as constraints, and the CPLEX solver was adopted to solve the problems; finally, the practicability and effectiveness of the expressed model and method was verified through examples.
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53、Analysis of Three-phase Voltage Sag Isolation Capability of Cascaded Power Electronic Transformer
XU Shaobo, CHEN Jiamin, XU Yonghai, ZHANG Xueyin, LONG Yunbo, DENG Zhanfeng
Available online:September 17, 2019 DOI: 10.7500/AEPS20190126005
Abstract:Cascaded power electronic transformer (PET) have the characteristics of modularization, scalability and easy redundancy design, which has broad application prospects in medium and low voltage distribution networks. In-depth study of voltage sag isolation capability of cascaded PET is of great value for parameter selection of cascaded PET device, energy storage capacity configuration and reduction of voltage sag treatment devices. Through theoretical deduction, the limiting factors of voltage sag isolation capability of cascaded PET are studied. For the input stage, the effects of modulation ratio, DC link capacitor voltage fluctuation and RMS limit of switching device current on its voltage sag isolation capability are deeply studied. For the isolation stage, the effects of the phase-shift ratio, RMS and peak limit of the switching device on the voltage sag isolation capability of DC link are analyzed in detail. The main limiting factors of the voltage sage isolation capability of the input and isolation stages with different design parameters are clarified. And the effective isolation area of cascaded PET is established. Finally, the correctness of the research results is verified by simulation.
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ZHANG Xueyin, XU Yonghai, XU Shaobo, XIAO Xiangning
Available online:September 04, 2019 DOI: 10.7500/AEPS20190328001
Abstract:Medium-voltage multilevel converters usually adopt a modular structure. They can be used in AC/DC distribution networks. As a result of the relatively low voltage in distribution networks, the number of converter sub-modules is small. Therefore, carrier phase shift pulse width modulation (CPS-PWM) is widely used to increase the equivalent switching frequency. The modeling of CPS-PWM is one of the fundamentals of converter system modeling. The modulation stage is nonlinear, and thus, only the fundamental frequency component is usually considered. The existing fundamental approximation model of CPS-PWM is based on equivalent switching frequency, hence the low time delay and large errors when asymmetric regular sampling is adopted. In this work, the following three forms of fundamental approximation models of CPS-PWM are established: zero order holder (ZOH) delay approximation, ZOH no approximation, and delay Padé approximation. These models are developed by combining the outputs of sub-models on the basis of a sub-module. The proposed models more accurately reflect the frequency characteristics of CPS-PWM than the traditional one. A simulation study verifies the correctness of the theoretical analysis.
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Available online:September 03, 2019 DOI: 10.7500/AEPS20190312007
Abstract:With the increasing proportion of nuclear power and intermittent power supply, nuclear power plant (NPP) is facing higher peak-shaving pressure. Since the present mathematical models of NPP participating in peak load regulation are imperfect, a peak-shaving safety output model for NPP is proposed, which effectively unifies the NPP’s specific safety requirements and flexible regulation patterns. By means of compacting the constraints and making the peak regulating depth continuous, the shortcomings of the existing models in general applicability, economy and flexibility could be solved. To guarantee accurate NPP safety output under various operating conditions, the feasible region of NPP output is shrunk by introducing decoupled auxiliary variables of power up/down and fully considering the coupling characteristics and mutex relationship of power changes. In addition, make regulating depth continuous in order to obtain the optimal regulating depth and time, which increase the flexibility of NPP peak regulating operation mode. The model could be easy to solve because the non-linear term is equivalently transformed into linear by using the math transformation technique. The simulation results, which verify the validity of the model, show that the proposed model can accurately, flexibly and economically arrange the peak-shaving safety output of nuclear power plants and reduce about 5% peak regulating depth and 18% peak regulating cost.
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MI Yang, SONG Genxin, SONG Yuanyuan, YUAN Minghan, FU Yang, WANG Chengshan
Available online:September 03, 2019 DOI: 10.7500/AEPS20190108003
Abstract:The AC/DC hybrid multi-microgrids consists of multiple AC and DC sub-microgrid, and its stable operation depends on reasonable power management. How to play the autonomous feature of sub-microgrid and realize the power interaction between sub-microgrids is one of the key issues for the power management of AC/DC hybrid multi-microgrids. A multi-level power management strategy is proposed for the islanded AC/DC hybrid multi-microgrids. This management strategy consists of two parts: multi-level power allocation control and multi-level power interaction management. Reasonable allocation of power is achieved through power autonomous level, power interaction level, and power balance level. Considering the normal communication and communication failure, the multi-level power interaction management strategy is designed to ensure the power quality of the islanded AC/DC hybrid multi-microgrids and to reduce the unnecessary power interaction loss. The multi-level power interaction management strategy only exchanges data at the event triggering time, which reduces the amount of system information exchange and reduces the system requirements for the communication network. And the results of MATLAB/SIMULINK proved that the proposed control strategy is correct and feasible.
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YANG Jingxu, YI Yingqi, ZHANG Yongjun, MO Yifu, HUANG Tingcheng, XIE Xiaoyu
Available online:August 30, 2019 DOI: 10.7500/AEPS20190303007
Abstract:Aiming at the analysis of operation risk of the distribution network caused by electric vehicle to grid, the indicator of loss severity with amplification factor is proposed, and the distribution entropy is used to measure the risk caused by the uncertainty of the distribution of the state variables of the distribution network. Weighting the distribution entropy using loss severity, the weighted distribution entropy (WDE) is established, based on which the voltage risk index and the load-flow risk index are established. The weighted sum of WDE is calculated according to the component importance, so as to evaluate the voltage risk and the load-flow risk of the network. Taking into account both types of risks, a comprehensive set of indexes is constructed to evaluate the operation risk of distribution networks. Finally, simulation studies are conducted on an improved IEEE 33-node distribution system with wind power and photovoltaic accessed, and the superiority of WDE over traditional risk indicators and the rationality of the comprehensive index are analyzed by dynamic probabilistic power flow simulation. In addition, the variation of the operational risk with the access location and capacity of electric vehicle load are studied. By the simulation studies, the effectiveness of the indicators and models proposed in this paper is verified.
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LI Yu, LU Feng, FAN Qiang, ZHAO Chengyong, XU Jianzhong, QU Haitao
Available online:August 29, 2019 DOI: 10.7500/AEPS20190304003
Abstract:The existence of the negative-sequence voltage on the AC side will aggravate the voltage fluctuation of the MMC sub-module under the unbalanced grid voltage. Reducing the amplitude of the capacitor voltage ripple of the sub-module in the Multilevel Modular Converter (MMC) is expected to reduce the capacitance, volume and cost of the sub-module capacitor under the unbalanced grid voltage. Most of the previous researches are based on the analysis under the balanced grid voltage, which can not effectively reduce the sub-module capacitor voltage fluctuations under the unbalanced conditions. Firstly, the fluctuation of capacitor voltage of MMC sub-module under unbalanced network voltage and the influence of third harmonic injection on sub-module voltage fluctua-tion are analyzed;The amplitude and the phase angle of third harmonic injection under unbalanced network voltage are calculated.The modulation voltage peak can be minimized by injecting the designed third harmonic voltage; The fluctuation suppression strategy is designed; Finally, the validity of the proposed strategy is verified by simulating the double-ended hybrid MMC in PSCAD/EMTDC.
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ZHU Yongqiang, ZHANG Quan, LIU Kang, WANG Zhi, WANG Fuyuan
Available online:August 27, 2019 DOI: 10.7500/AEPS20190227008
Abstract:In order to solve the power fluctuation caused by the change of micro-sources output, loads and power of energy storage devices in hybrid AC/DC microgrid, a segmented coordination control strategy for hybrid microgrid is proposed in this paper. Aiming at the hybrid microgrid in islanded state, the typical topology of the hybrid microgrid and the power relations under different operation modes are analyzed. The characteristic quantity which can represents the whole operation state of hybrid microgrid are obtained by standardization method. According to the variation of the characteristic quantity, the control strategy is divided into segments. Then the working principle of each section control is analyzed in detail and the coordinated control of the converters in different control segments are studied. Aiming at the possible power oscillation and frequent switching of ILC operation modes, the action criterion is compensated. Finally, a simulation model is established in PSCAD/EMTDC. The simulation results show that all converters can respond quickly under different operating conditions to ensure the stable operation of the system.
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YUAN Hongtao, WEI Gang, ZHANG He, LUO Zhigang, HU Jue
Available online:August 27, 2019 DOI: 10.7500/AEPS20190509008
Abstract:This paper proposes an optimal scheduling model capable of considering comprehensively electric vehicle charging-swapping-storage integrated station and active distribution network. According to fast-charging users’ behavior characteristics and speed-flow practical model of city roads, battery fast charging station model and battery swapping station model are established respectively, which combined the cascade energy storage system as the integrated station model. In the active distribution network integrated with wind turbines, photovoltaics, micro-turbines and the integrated station, the optimal scheduling model is established, and the model is proposed to solve the problem via being transformed into a mixed integer second-order cone model. The multi-time scale optimization scheduling strategy based on model predictive control is used to realize day-ahead scheduling, intra-day rolling scheduling and real-time feedback correction, which reduces the impact of distributed generation and load prediction errors on distribution network operation. Taking the actual road conditions of a city"s bus lines as example, it is verified that the optimal scheduling strategy proposed in this paper has advantages of meeting the charging load demand of electric vehicles, suppressing power fluctuation and reducing ADN daily total operation cost.
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GAO Jianrui, LI Guojie, WANG Keyou, WU Pan, YU Zhongmin
Available online:August 23, 2019 DOI: 10.7500/AEPS20190515010
Abstract:During the normal operation, the output power of the photovoltaic-battery virtual synchronous machine (PV-Battery VSM) tracks its power command, and the PV panel operates at the maximum power point. The deviation between the PV power and the power command is eliminated by the battery power, which suppresses the power fluctuation of the inverter. However, the PV power is fluctuant and uncertain. When the PV power fluctuation exceeds the battery power limit, it will lead to a large DC bus voltage offset and affect the stable operation of the VSM. Control methods for the grid-connected PV-Battery VSM considering the battery charging/discharging power limit are proposed to solve the problems above. The inverter, the PV and the battery are controlled coordinately based on the state of charge (SOC) of the battery. The DC bus voltage offset is suppressed and eliminated when the charging/discharging power of the battery reaches the upper limit. The battery is fully utilized for the VSM output power to track the power command, and over-charging/over-discharging of the battery is avoided. The PV-Battery VSM system can operate safely and stably. The proposed control methods are verified by simulations based on PSCAD/EMTDC and semi-physical simulations.
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LI Guang, XUE Yongduan, YANG Fan, XU Bingyin
Available online:August 20, 2019 DOI: 10.7500/AEPS20190127009
Abstract:The physical simulation of the distribution network is receiving more and more attention. The transmission line often adopts the Π-shaped equivalent circuit chain network simulation. How to construct the transmission line model economically and effectively is very important. This paper has given the input impedance expressions of the lossless Π-shaped circuit chain network at different cascade numbers and clarified the difference in phase-frequency characteristics between the chain network and the lossless uniform transmission line. The amplitude-frequency error of the characteristic impedance between the Π-shaped circuit chain network and the lossless uniform transmission line is analyzed. It is found that when the operating frequency approaches or exceeds the upper limit frequency, with which the Π-shaped circuit chain network simulate the lossless uniform transmission line, the two are essentially different. Besides, the ratio between any frequency and the upper limit frequency is only related to the characteristic impedance error. The ratio of any frequency to the upper limit frequency is only related to the characteristic impedance error. In the chain network, each Π-shaped circuit is premised on working within its first resonant frequency, so that the reasonable error range of the characteristic impedance can be determined. Furthermore, the reasonable number of cascades suitable for Π-shaped circuit chain network of the distribution network can also be obtained. Through the calculation and simulation of typical transmission line parameters, the method is verified to be reasonable and effective.
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ZHAO Chengyong, LI Shuai, ZHANG Jiyuan, LI Jialong, XU Jianzhong
Available online:July 31, 2019 DOI: 10.7500/AEPS20190128005
Abstract:With the development of HVDC transmission technology, the isolation of DC faults is becoming increasingly important. As the most effective solution, hybrid HVDC circuit breaker is not mature enough, which restricted its engineering application. Accordingly, this paper proposes a low-cost DC fault isolation scheme suitable for HVDC grid. In this scheme, the traditional half-bridge MMC is partially innovated to have the ability of auxiliary breaking operation. With the effect of the MMC auxiliary breaking operation at both ends of the fault line, the DC fault current can be easily interrupted and isolated by low-cost circuit breaker unit installed in the DC transmission line. The equivalent circuit under the fault isolation process is analyzed, and the fault isolation sequences are designed. Furthermore, the devices usage comparative analysis among three schemes is performed. Finally, a four-terminal bipolar HVDC grid test model is built in PSCAD/EMTDC, in addition, an MMC prototype with proposed scheme is also developed. The simulation and experimental results validate the effectiveness of the proposed scheme.
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LI Danqi, MEI Fei, ZHANG Chenyu, SHA Haoyuan, ZHENG Jianyong, LI Taoran
Available online:July 16, 2019 DOI: 10.7500/AEPS20190306004
Abstract:In this paper, a method of voltage sag feature extraction and sag source identification based on DBN is proposed. The feature extraction ability of DBN is used to extract the feature data from the measured waveform data, which solves the problem that the artificial extraction features relie on expert experience and do not have generality are solved. The multi-hidden layer structure network learning feature is used to realize the identification of the sag source. The model set feature extractor and classifier are integrated to optimize the model structure and improve the efficiency of sag source identification. he optimal parameters of the model are selected, and the DBN model suitable for the data type of voltage sag is established. The feature extraction and sag source identification of the measured sag data of the power grid are carried out. The superiority of DBN method in feature extraction and sag source identification has been verified by comparison, and it is suitable for practical engineering.
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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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2017,41(8):1-1, DOI: 10.7500/AEPS20170305006
Abstract:
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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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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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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.
