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  • Volume 47,Issue 24,2023 Table of Contents
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    • >Invited Paper
    • Fault Ride-through Strategy for Doubly-fed Wind Farms Considering Coordination of Protection Operation Time

      2023, 47(24):1-10. DOI: 10.7500/AEPS20230322004

      Abstract (344) HTML (266) PDF 2.56 M (587) Comment (0) Favorites

      Abstract:The transient overvoltage in the grid-connected system of wind farms after fault clearing causes frequent wind turbine off-grid accidents. The main reason for this is the response delay of doubly-fed induction generator (DFIG) and reactive power compensation device during the withdrawal process of reactive power compensation after fault clearing. Therefore, based on the analysis on the rotor-side converter and grid-side converter of DFIG and the reactive power compensation limit of reactive power compensation device, this paper determines the reactive power compensation allocation strategy among different devices mentioned above. Furthermore, the dynamic response speed of different devices during reactive power compensation is analyzed, and based on this, an optimal design method for reactive power reference curve considering the operation time of main and backup protection is proposed. Compared with the existing reactive power compensation strategies, this method can significantly reduce the transient overvoltage problem at the point of common coupling during fault recovery while ensuring the fault ride-through capability. Finally, a simulation model is built based on a real-time digital simulation system, and the feasibility and superiority of the proposed method are fully verified through a large number of simulation cases

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    • Optimal Day-ahead Scheduling Method for Electricity-Water-Heat Integrated Energy System Considering Virtual Energy Storage

      2023, 47(24):11-21. DOI: 10.7500/AEPS20230322003

      Abstract (337) HTML (405) PDF 1.69 M (568) Comment (0) Favorites

      Abstract:A day-ahead economic scheduling method considering virtual energy storage (VES) is proposed for the electricity-water-heat integrated energy system (EWH-IES) including the high proportion of volatile renewable energy sources such as photovoltaic and photothermal. First,in order to effectively utilize the flexibility of water storage characteristics in the water supply subsystem and hot water storage characteristics in the hot water supply subsystem, two types of VES models between electricity-water and electricity-heat of EWH-IES are established. Three virtual energy storage parameters including virtual charging and discharging power, virtual electric capacity, and virtual state of charge are defined to explore the capacity of water and hot water storage to participate in the optimal operation of EWH-IES. Then, an extended energy hub model that integrates VES models and the coupling electricity-water, electricity-heat energy and material flows is established to describe the mathematical relationship of energy and material flow conversion in EWH-IES. On this basis, an optimal day-ahead economic scheduling method considering the virtual charging and discharging capabilities of the two types of VES is proposed to support the optimal operation of EWH-IES through the flexibility utilization of the two types of VES. Finally, a case is given to verify the effectiveness of the proposed method in improving EWH-IES operation economy and renewable energy accommodation.

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    • Line Parameter Identification Method for Multi-ring Medium-voltage Distribution Network Based on Phaseless Measurement

      2023, 47(24):22-30. DOI: 10.7500/AEPS20230525005

      Abstract (195) HTML (190) PDF 1.66 M (550) Comment (0) Favorites

      Abstract:Accurate line parameter identification is an important foundation for refined regulation and protection setting of distribution networks. Due to the complex topology and variable power flow directions, ring distribution networks are difficult to apply the line parameter identification methods for traditional radial network. This paper proposes a line parameter identification method for multi-ring medium-voltage distribution network that does not require phase measurement data. To address the issue of unclear power flow direction in multi-ring distribution networks, a ring opening method based on power direction judgment and decomposition is proposed and extended to any ring distribution network. Based on the ring opening network, the linear correlation problem between equations at different time is analyzed, and a high-dimensional non-convex optimization model for solving line parameters is constructed. Subsequently, the genetic algorithm is used to identify line impedance and admittance. Finally, a honeycomb distribution network model is built in MATLAB for validation, and the results show that the proposed algorithm has higher accuracy and robustness compared with traditional least squares algorithm, particle swarm algorithm, and simulated annealing algorithm.

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    • Collaborative Optimization of Building Aggregation and Integrated Community Energy System Considering Difference in Insulation Performance

      2023, 47(24):31-38. DOI: 10.7500/AEPS20230310004

      Abstract (208) HTML (150) PDF 1.46 M (1312) Comment (0) Favorites

      Abstract:In the collaborative operation of building aggregation and integrated community energy system (ICES), buildings with different insulation performances have differential thermal demand response capabilities. In order to fully mobilize their differential demand response potentials, this paper constructs a collaborative optimization framework of building aggregation and ICES considering the difference in insulation performances. First, based on the thermal storage characteristics of the buildings with heating, a resistor-capacitor network is used to model the thermal dynamic process of heat in the building envelope. Secondly, based on the thermal dynamic model of the building, a model of differential heat demand response is constructed for building users containing adjustable radiators. Then, a collaborative optimization framework based on two-layer optimization of building aggregation and ICES is proposed, and a refined heat supply price scheme that realistically responds to the heat consumption of building users is further adopted in the collaborative optimization framework. Finally, the effectiveness of the proposed method is verified by a case

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    • Modeling of Components in Smart Distribution Systems for Real-time Security Analysis

      2023, 47(24):39-51. DOI: 10.7500/AEPS20230615007

      Abstract (193) HTML (135) PDF 1.75 M (562) Comment (0) Favorites

      Abstract:Smart distribution system contains new components such as distributed generation, energy storage system, demand response, microgrid and soft open point. The component models for security analysis are established, and a new security analysis method is also proposed. Firstly, the concept of security service capability (SSC) for distribution system is proposed, which reflects real-time power adjustment capability of the new components on the distribution network side. Secondly, the SSC-based security analysis method is proposed. Thirdly, based on the analysis of component security roles, security service forms and limits, the medium-voltage-side node models with different combinations of various components are constructed. Finally, the component modeling process is demonstrated through a case study, and the correctness of the proposed models and method is verified by the SSC-based security analysis. The proposed models lay a foundation for the security analysis of smart distribution systems, and the SSC provides new key data for the security analysis by system operators.

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    • Multi-energy Coupled Flow Hub Modeling for Generalized Energy Quality Analysis

      2023, 47(24):52-62. DOI: 10.7500/AEPS20230705002

      Abstract (164) HTML (129) PDF 2.10 M (507) Comment (0) Favorites

      Abstract:The development of the integrated energy system (IES) helps improve the overall energy efficiency of the system and promote the utilization of renewable energy. The key generalized energy quality issues such as the effective energy level, energy use uncertainty, and carbon emission intensity of multiple types of heterogeneous energy are gradually becoming prominent, which promotes the development of energy system “flow” modeling theories based on energy flow, exergy flow, entropy increase flow and carbon emission flow. The multi-energy coupled link determines the multi-energy conversion and distribution process of IES, and is one of the key factors which affect the generalized energy quality of IES. In this paper, the definition of “flow” general components in the multi-energy coupled link is given under the unified level of refinement and abstraction. And the flow hub model and its calculation method suitable for various energy quality analysis elements are proposed based on the standardized matrix framework, the discussion is made on how to rationally modify the constraint conditions for the multi-energy coupled link and ensure that the flow hub model has a unique operation state according to the solvability of the model relationship matrix. Finally, the validity of the flow hub model is verified through case studies.

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    • Review on Grid-forming Control and Start-up Method of Diode-rectifier-unit Based HVDC Transmission System for Remote Offshore Wind Farm

      2023, 47(24):63-79. DOI: 10.7500/AEPS20230118001

      Abstract (271) HTML (279) PDF 3.05 M (685) Comment (0) Favorites

      Abstract:With the continuous large-scale and remote offshore development of offshore wind power, DC transmission technology of offshore wind power has become a research hotspot. Aiming at the low-cost diode-rectifier-unit (DRU) based high-voltage DC (HVDC) transmission, the main technical characteristics of distributed DRUs in voltage equalization and partial exit operation are emphasized, and the differences between this technology and flexible DC transmission and traditional DC transmission are discussed. Due to the uncontrollability of DRU, the construction of offshore power grid must be realized by the wind turbines through their own control. Therefore, the existing researches on centralized and decentralized grid-forming control of wind turbines are reviewed in detail, and P-V and Q-f power control mechanisms are adopted to explain the fully-grid-forming control from the wind farm-DRU level and wind turbine level. In view of the start-up problems caused by DRU unidirectional power flow, the start-up methods including auxiliary medium-voltage AC umbilical cable, auxiliary modular multilevel converter, energy storage configuration for offshore wind turbines and auxiliary low-voltage DC cable are summarized. It is pointed out that adopting the auxiliary medium-voltage AC umbilical cable is a relatively mature scheme, and the use of energy storage for offshore wind turbines and fully-grid-forming control has high flexibility. However, under the existing technology, there are still problems such as insufficient installation space inside the wind turbine tower barrel and energy storage safety risk. Finally, the future research directions of offshore wind power transmission system via DRU-HVDC are prospected.

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    • Distributionally Robust Optimization Method for Substation Planning Considering Incentive-based Response Uncertainty

      2023, 47(24):80-89. DOI: 10.7500/AEPS20230627006

      Abstract (202) HTML (157) PDF 1.49 M (594) Comment (0) Favorites

      Abstract:A distributionally robust optimization method for substation planning is proposed to address the problem that the existing substation planning has not fully considered the lack of fine-grained solutions due to the uncertainty of incentive-based demand response. Firstly, comprehensively considering the contracting cost, response cost and penalty benefit of the demand response, a mixed-integer linear programming (MILP) model for the substation location and capacity determination is developed by taking into account the source-load matching and incentive-based demand response. Secondly, an uncertain fuzzy set based on 1-norm and ∞-norm demand response and distributed generator output is constructed, and a two-stage three-level distributionally robust optimization model based on multiple discrete scenarios is established according to the improvement of MILP model. Then, a master problem and sub-problem iterative algorithm based on column-and-constraint generation (C&CG) is used to achieve the solution using a commercial solver. Finally, the effectiveness and practicality of the proposed method are verified by a practical arithmetic case in a region.

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    • Distributed Adaptive Rolling Predictive Scheduling Based on Coordination of Electric Vehicles and DC Distribution Networks

      2023, 47(24):90-99. DOI: 10.7500/AEPS20230425002

      Abstract (247) HTML (185) PDF 1.81 M (605) Comment (0) Favorites

      Abstract:In order to fully tap the flexible scheduling potential of electric vehicles (EVs), a distributed adaptive rolling predictive scheduling method based on the coordination of EVs and DC distribution networks is proposed. Firstly, the mathematical models of voltage source converter, energy storage and power flow of DC distribution networks are established. Then, the mathematical models of non-schedulable, charge-only and charge-discharge EV charging preferences are constructed, and the adaptive rolling predictive scheduling model of DC distribution networks is established with the goal of minimizing the weighted sum of daily energy loss and photovoltaic curtailment. The scheduling window is dynamically updated through the pick-up time of real-time EV clusters to meet the expected power demand of each EV. Finally, the distributed rolling predictive scheduling model of DC distribution networks is established, and the alternating direction method of multipliers is used to achieve distributed solution, so as to solve the problem of large communication traffic of centralized scheduling. The simulation results show that the cooperative scheduling of EV and DC distribution network flexibility resources can significantly reduce power loss and improve the acceptance capability of distributed power supply. At the same time, the distributed algorithm adopted has good convergence performance and computing speed.

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    • Stochastic Robust Operation Optimization for Park-level Integrated Energy System in Multi-stakeholder Market

      2023, 47(24):100-109. DOI: 10.7500/AEPS20230515002

      Abstract (241) HTML (175) PDF 1.85 M (669) Comment (0) Favorites

      Abstract:Park-level integrated energy system (PIES) is one of the significant schemes to improve the energy efficiency level of the consumption side. Meanwhile, its operation is affected by the uncertainty of the market price, which needs to be taken into account during the operation optimization. However, it is extremely difficult to accurately describe the characteristics of market operation and price fluctuation on account of the massive participants and the diverse mechanisms of price formation in the distribution market. In this paper, considering the basic principle of fair transaction in multi-agent distribution market, a stochastic robust operation optimization method based on risk-neutral pricing of distribution networks is proposed for the PIES. Firstly, the selling electricity pricing model of the distributed energy system and distribution network operators is established by analogy with the asset price process under risk-neutral measures, which is applied with the reasonable electricity price of distribution networks in the market environment. Secondly, a PIES two-stage stochastic robust operation optimization model is established by employing the box-type uncertainty set and other methods to depict the uncertainty of electricity price and source-load based on the reasonable price, which is solved using the column constraint generation algorithm and the strong duality theory. Finally, the numerical experimental results verify that the reasonable price model for electricity sales is effective and necessary in distribution networks, as well as the advantage of the stochastic robust operation optimization method compared with the traditional stochastic operation method and robust method, and the influence of the uncertainty electricity price on operation methods.

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    • >Views
    • Technical Architecture and Future Prospect for New Generation of Online Security Analysis

      2023, 47(24):110-120. DOI: 10.7500/AEPS20230920004

      Abstract (393) HTML (437) PDF 1.68 M (3228) Comment (0) Favorites

      Abstract:To adapt to the challenges faced in the construction process of new power systems, according to the concept of “inheritance, integration and innovation”, the overall architecture for the new generation of online security analysis is proposed. In the areas of model data, functional systems, business scenarios, and human-computer interaction, through the orderly cooperation of basic platform, real-time measurement, electrical network analysis and simulation computation, the connection and interaction between multi-source data and online analysis applications are realized, such as equipment model parameters, real-time measurement information, stability control model, stability limits. For the emerging new characteristics of power system operation, new functions are developed such as online electromechanical-electromagnetic hybrid simulation and online evaluation of rotational inertia and renewable energy multi-feed short-circuit ratio, which make the new generation of online security analysis architecture more scientific, analysis faster, simulation more accurate, ecology more open, and human-computer more friendly. The relevant achievements have been deployed on the dispatching and control cloud platform and served for dispatching agencies at or above the provincial level of the power system. Finally, the future development trends are proposed from four aspects of equipment modeling, computing efficiency, simulation analysis, and result application.

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    • >Basic Research
    • Operation Strategy for Internet Data Centers Considering Collaboration of Multi-type Markets

      2023, 47(24):121-131. DOI: 10.7500/AEPS20230518007

      Abstract (233) HTML (203) PDF 2.29 M (578) Comment (0) Favorites

      Abstract:With the development of cloud computing and the advancement of new infrastructure construction, the electricity consumption of Internet data centers (IDCs) is growing rapidly to meet the storage and processing needs of massive data. In the context of the construction of the new power system and the national unified electricity market, IDCs with adjustable loads can participate as the main body in electricity energy and auxiliary service markets. In addition, the operation of IDC generates a large amount of waste heat, which has the potential to provide regional heating services. On this basis, this paper first analyzes the value formation process of the Internet service provider (ISP) with multi-regional IDCs in a multi-type market coupling environment and establishes the corresponding market behavior model. Then, a bi-level decision-making framework and model for IDCs to participate in multi-type electricity markets and heating service are constructed. The upper-level model is an ISP decision-making model that takes workload as the direct decision variable, market bidding electricity and heat as indirect decision variables, and aims to minimize energy costs. The lower-level model is a market clearing model with the objective of maximizing social welfare. Finally, simulation is conducted using a case to verify the effectiveness of the proposed multi-market coupling decision-making mechanism in improving the benefit of IDCs and reducing energy costs.

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    • Virtual Microgrid Partitioning Planning Based on Modularity of Power Flow Tracking

      2023, 47(24):132-142. DOI: 10.7500/AEPS20230721002

      Abstract (192) HTML (118) PDF 1.60 M (556) Comment (0) Favorites

      Abstract:Virtual microgrid (VM) is a new method for upgrading conventional distribution networks towards intelligence. Most of the existing research on the VM partitioning focuses on its own topology. At the same time, the partitioning process is relatively independent and lacks the consideration for the security of VM. A more reasonable VM partitioning method has great significance for improving system stability. Firstly, a double-layer partitioning planning framework for the VM is proposed, which coordinates the reducible load and controllable distributed generator (CDG) under failure conditions while simultaneously implementing partitioning planning and CDG configuration. Subsequently, the modularity index based on the power flow tracking is established, which can serve as the main objective function of the upper-level model and evaluate the energy utilization rate of each partition to a certain extent. Then, on the basis of meeting various constraints, upper and lower mathematical models corresponding to the double-layer framework are established. Finally, eight partitioning schemes are optimized and screened layer by layer in the IEEE 33-bus model, resulting in two schemes with the best objective function in the upper- and lower-layer models. The two schemes have their own advantages and disadvantages in terms of energy utilization rate within the region and users’ load reduction experience, which verify the correctness and effectiveness of the proposed method.

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    • Adaptive Coordination Scheme of Single-end Backup Protection Based on Transient Characteristic Distribution

      2023, 47(24):143-155. DOI: 10.7500/AEPS20230227002

      Abstract (175) HTML (148) PDF 2.68 M (504) Comment (0) Favorites

      Abstract:Single-end backup protection plays an important role in ensuring the safe operation of the distribution network. However, its setting task is heavy and it is difficult to adapt to the scenario of the random access of inverter-interfaced distributed generation (IIDG). Therefore, it is urgent to study an adaptive coordination scheme for backup protection that does not require step-by-step setting. A relay-type inverse-time backup protection scheme with “transient fault identification+steady-state operation discrimination” is proposed to address the issue of mal-operation/miss-operation in traditional stage coordination protection due to the limited short-circuit current during the steady-state stage of faults after the high proportion of renewable energy is connected. Firstly, the qualitative analysis is conducted and impedance characteristics are used to verify the transient characteristic distribution of the instantaneous real power of the fault component when the topology changes. Time-domain information within the minimum applicable frequency band with natural differences is extracted, and the transient energy of the unregulated phase of the converter is calculated. Secondly, the parameter selection principle for the unified inverse-time characteristic equation of the entire network is given to achieve the adaptive coordination between adjacent protections. Then, an action criterion based on steady-state voltage is constructed, and a single-end backup protection coordination scheme is obtained using the electrical quantities throughout the fault process. Finally, the simulation verifies the effectiveness of the proposed method with different topologies, distributed power capacity, and changes in accessing modes.

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    • >Egineering Application
    • Fault Ride-through Performance Optimization of Variable-speed Pumped Storage Units for Enhancing Power Angle Stability of Power Systems

      2023, 47(24):156-164. DOI: 10.7500/AEPS20230403006

      Abstract (236) HTML (182) PDF 2.02 M (618) Comment (0) Favorites

      Abstract:In the scenario of large-capacity pumped storage power plant (PSPP) with fixed-speed pumped storage units (FSPSUs) and variable-speed pumped storage units (VSPSUs) transmitting through weak AC lines, there is a risk of power angle instability for the FSPSUs. Therefore, a method for improving system power angle stability is proposed by optimizing the fault ride-through (FRT) performance of VSPSUs. First, the dynamic model of the power transmission system of the PSPP is established, the sensitivity of the output power of VSPSUs to the system deceleration area is derived, and the impact of the FRT performance of VSPSUs on the system power angle stability is clarified. Then, on the premise of ensuring that there is no risk of rotor overspeed of the VSPSUs during the fault period, a setting method for the FRT current limit and voltage threshold of the VSPSUs is proposed to reduce the recovery speed of active and reactive power of the VSPSUs during the fault period, and improve the system power angle stability. Finally, a simulation case based on the Fengning PSPP in Hebei Province, China, is used to verify the effectiveness of the proposed method.

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    • Analysis on Dead-zone Angle and Dead-zone Voltage for Tap Adjustment of HVDC Transmission Converter Transformer

      2023, 47(24):165-174. DOI: 10.7500/AEPS20230331002

      Abstract (197) HTML (135) PDF 1.78 M (550) Comment (0) Favorites

      Abstract:The high-voltage direct current (HVDC) transmission system realizes the power regulation through rapid control of the triggering angle of converters. In addition, in order to expand the power regulation range and maintain the system in a good operation condition, the tap adjustment of converter transformer is also supplemented. The relationship between tap adjustment and angle change or AC voltage fluctuations from the rectifier side and the relationship between tap adjustment and DC voltage or AC voltage fluctuations from the inverter side are analyzed, respectively. The dead-zone setting principle for tap adjustment is proposed, which is to select an appropriate dead-zone angle or dead-zone voltage of the converter transformer tap based on the AC voltage fluctuation range of the actual AC system connected to the HVDC transmission system, in order to prevent reduced lifespan or even damage of the tap changer caused by tap reciprocating adjustment, and to avoid large fluctuations in reactive power and DC voltage.

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