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Journal of Electrical Engineering    2022, 17 (1): 1-1.   DOI: 10.11985/2022.01.001 Abstract （207）   HTML （48）    PDF （113KB）（141）       Knowledge map    Reference | Related Articles | Metrics

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Research Status and Prospect of Microgrid Stability under Pulsed Power Loads MENG Zhiyuan, XU Hailiang, LIU Chunzhen Journal of Electrical Engineering    2022, 17 (1): 2-14.   DOI: 10.11985/2022.01.002 Abstract （731）   HTML （56）    PDF （432KB）（1656）       Knowledge map    In recent years, the development of microgrid and power electronics technology provides a new application environment and platform for pulsed power load, and the application of pulsed power load in on-board microgrid and ship power system is becoming more and more common. However, these pulse loads pose great challenges to the stable and safe operation of microgrid due to their unique operating characteristics. Based on this, the influence of pulse power load on the stability of microgrid is focused, the research content at home and abroad are summarized, including electronic radar, electromagnetic emission and recycling equipment, pulse weapons, such as pulse power load type, periodic disturbance, strong nonlinearity, the bus voltage and frequency instability mechanism, such as the influence of the stability analysis, the energy storage system, such as virtual synchronization technology strategy. Finally, the future research direction of microgrid stability under pulse power load is analyzed, and the future research is prospected based on the existing problems. Table and Figures | Reference | Related Articles | Metrics

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High Quality Cooperative Control of DC Microgrids Using Dynamic Consensus Algorithm ZHANG Hao, LI Yu, YIN Yafei, LI Zhen, ZHANG Zhenbin Journal of Electrical Engineering    2022, 17 (1): 15-21.   DOI: 10.11985/2022.01.003 Abstract （554）   HTML （17）    PDF （318KB）（930）       Knowledge map    Aiming at islanded DC microgrids, a cooperative control strategy based on consensus algorithm is proposed. In this strategy, the controllers for each distributed generation can achieve precise voltage control and power sharing, which only requires communication with neighboring units. However, the classic cooperative control schemes simultaneously require the knowledge of voltage and current information of their neighboring units, hence still have high communication burden. A unified distributed control strategy is proposed. This strategy integrates the voltage control and power sharing processes into one step, and eliminates the current information from neighboring units, greatly reducing the need of communication bandwidth. Finally, the effectiveness of the proposed method is verified by simulation. Table and Figures | Reference | Related Articles | Metrics

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Study on Power Optimization Method and Coordinated Control Strategy of Optical Storage Microgrid LIU Yandong, HU Yiwen, CHEN Nan, WANG Jingyue, SHAO Xinming, PEI Zhongchen, LIU Chuang Journal of Electrical Engineering    2022, 17 (1): 22-30.   DOI: 10.11985/2022.01.004 Abstract （626）   HTML （20）    PDF （583KB）（1315）       Knowledge map    As a friendly power generation mode, optical storage microgrid has the advantages of stabilizing grid side power fluctuation, stabilizing photovoltaic (PV) power generation capacity and schedulability. It is the preferred scheme to realize the stable operation of ‘source-network-load-storage’ system and the full absorption of new energy. Based on the power optimization and flexible operation of optical storage microgrid, a component level configuration scheme and coordinated control strategy are proposed to further release the potential of PV power generation and promote the efficient operation of energy storage unit. Firstly, aiming at the barrel effect caused by PV module mismatch and low efficiency of energy storage converter, PV module power optimizer and energy storage partial power converter are configured respectively to maximize the utilization of solar energy and electric energy. Secondly, the multi-mode switching of PV array and energy storage unit under on/off grid conditions is discussed. Considering the power dynamic balance among the units of microgrid, a coordinated control strategy of optical storage microgrid is proposed to realize the smooth switching and power automatic distribution of each unit between different control modes. Finally, a 30 kW optical storage microgrid simulation platform is built by using Matlab/Simulink to verify the feasibility and effectiveness of the proposed coordinated control strategy. Table and Figures | Reference | Related Articles | Metrics

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Circulating Current Suppression and Power Control of Paralleled Bidirectional Interlinking Converters in Hybrid AC/DC Microgrid GUO Qiang, XIANG Wenkai, LI Shan Journal of Electrical Engineering    2022, 17 (1): 31-40.   DOI: 10.11985/2022.01.005 Abstract （489）   HTML （13）    PDF （896KB）（994）       Knowledge map    Aiming at the power flow, distribution and circulation problems when multiple bidirectional interlinking converters (BICs) are operating in parallel in AC-DC hybrid microgrids, a distributed power management control strategy for multi-parallel BICs is proposed. Each BIC is designed with an independent local distributed controller, which calculates its own power reference value, and can be allocated proportionally according to different power ratings to realize the power flow between the two sub-networks and the power distribution between different BICs. In addition, based on the null vector feedforward control strategy, a virtual BIC concept is proposed to realize the multi-parallel BIC circulating current suppression. The simulation and hardware-in-the-loop experimental results show that the strategy can effectively control the power flow between the two sub-networks and suppress the circulating current between multiple modules. Table and Figures | Reference | Related Articles | Metrics

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Research on Influencing Factors of Distribution Network Reliability Based on Combination Empowerment and Improved Grey Correlation Analysis WANG Mengfan, ZHENG Jianyong, MEI Fei Journal of Electrical Engineering    2022, 17 (1): 41-48.   DOI: 10.11985/2022.01.006 Abstract （906）   HTML （12）    PDF （264KB）（844）       Knowledge map    In order to accurately and quickly evaluate the reliability of distribution network and provide a basis for reasonable selection of improvement measures, a reliability evaluation and influencing factor analysis model based on empowerment and improved grey correlation analysis is constructed. Firstly, the G1-CRITIC method (Order relation analysis method-criteria importance though intercrieria correlation) and the least squares-based empowerment model are used to determine the comprehensive reliability evaluation index. Secondly, the key factors are selected to construct the reliability influencing factor index system. Then, the dynamic resolution coefficient is introduced to enhance the data difference to make up for the shortcomings of the traditional grey correlation analysis. Combined with the idea of TOPSIS (Technique for order preference by similarity to an ideal solution), the comprehensive gray correlation degree of each influence factor relative to the reliability comprehensive evaluation index is calculated and ranked as the reference basis for reliability improvement measures. Finally, the effectiveness of the proposed method is verified by a practical example. Table and Figures | Reference | Related Articles | Metrics

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Research on Improved Coordination Control Strategy for Soft Open Point ZHOU Feiyang, WANG Chuyang, ZHANG Li, LIN Jinjiao, KONG Xiangping, ZHENG Junchao Journal of Electrical Engineering    2022, 17 (1): 49-55.   DOI: 10.11985/2022.01.007 Abstract （827）   HTML （13）    PDF （323KB）（834）       Knowledge map    Under the rapid development of distributed new energy technology, the coordinated control of each port of soft open point (SOP) is crucial to the stable operation of the distribution network. When the SOP adopts master-slave control, only the converter controlled by the fixed DC voltage participates in the regulation. However, when there is a large power fluctuation in the system, the problems of overshoot of the power of the main converter and over-limit of the DC side voltage appear. In order to prevent the stable operation of the system from being affected by only a single converter station performing power regulation, an improved coordinated control strategy is proposed. Using the DC voltage fluctuation and the imbalance of power in the system are relevance, was introduced to the rated power loop controller dc voltage follower change, make the inverter also participate in power regulation when the power imbalance in the system. This strategy enables multiple converters to participate in power regulation at the same time, and the SOP can be smoothly switched in different control modes. Finally, the PLECS simulation model of three-terminal SOP is built to verify the correctness and effectiveness of the improved coordination control strategy. Table and Figures | Reference | Related Articles | Metrics

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Multiport Integrated Onboard Converter Based on V2G Technique LI Chunjie, CHEN Xinyu, HUANG Wenxin, ZHAO Mingwei, ZHANG Hongtao Journal of Electrical Engineering    2022, 17 (1): 56-62.   DOI: 10.11985/2022.01.008 Abstract （466）   HTML （12）    PDF （902KB）（1159）       Knowledge map    Bidirectional power converter is the key device to realize vehicle to grid(V2G) technique. Introducing integration technique, a new integrated onboard power converter is proposed by sharing the driving motor and the driving power electronic conversion device. It can feed the battery storage energy into the grid and charge the battery. The integrated converter has singe-phase charging and three-phase charging interface, realizes one charger with many ports, and enhances the compactness of the onboard system. The integrated converters under different charging modes are analyzed, and the control strategies under different charging and discharging modes are given. Finally, the simulation and experimental results are given to verify the feasibility of the multi-port integrated converter. Table and Figures | Reference | Related Articles | Metrics

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Research on Passivity-based Control Strategy of Multi-converter System WANG Zhenye, WANG Jiuhe, ZHANG Menghao Journal of Electrical Engineering    2022, 17 (1): 63-70.   DOI: 10.11985/2022.01.009 Abstract （439）   HTML （11）    PDF （453KB）（569）       Knowledge map    In the multi-converter system, the interaction between power electronic converters and the constant power load characteristics of the power electronic converters under closed-loop control at the input will affect the stability of the system. At the same time, as the complexity of the multi-converter system increases, system stability analysis and control strategies based on system model are facing challenges. In view of the above problems, passivity-based control (PBC) theory is used to study the control of the multi-converter system from the energy perspective. By ensuring the passivity of the subsystems, the passivity of the entire system is ensured, thereby ensuring the stability of the entire system. In order to achieve a better control effect, the controller is designed with active disturbance rejection control technology. Compared with PI combined with PBC, it has better dynamic and steady-state performance under plug-and-play conditions. Using Matlab/Simulink to build a simulation model of the multi-converter system, the simulation results show the feasibility and superiority of proposed control strategy. Table and Figures | Reference | Related Articles | Metrics

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Startup Inrush Current Suppression Method for Star-connected CHB STATCOM WU Tianhong, WEI Miaoyu, LU Daorong, HU Haibing Journal of Electrical Engineering    2022, 17 (1): 71-77.   DOI: 10.11985/2022.01.010 Abstract （479）   HTML （13）    PDF （522KB）（733）       Knowledge map    Soft startup is essential to the operation of the star-connected cascaded H-bridge (CHB) STATCOM. Conventional CHB STATCOM startup strategy suppresses inrush current by connecting current limiting resistors in series during uncontrolled rectification. However, due to the low DC-side capacitor voltage after the start-up phase, the CHB STATCOM will still generate a large inrush current when it enters the normal operating state. To eliminate this inrush current, a novel startup control is proposed to further charge the DC voltages after the uncontrolled rectifier process. After the uncontrolled rectification stage, the controllable boost stage is introduced, and the current limiting resistors continues to be connected in series, thereby further increasing the DC capacitor voltage. In the controllable boost stage, the relationship between modulation voltages and DC voltages is established, based on which a closed-loop control is proposed. The effectiveness of the proposed control is verified by the experimental results on a 400 V/5 kVar CHB STATCOM. Table and Figures | Reference | Related Articles | Metrics

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VSG Parameter Identification Based on Multi Innovation Stochastic Gradient Method in Time Domain ZHU Jun, QU Yubo, LIU Penghui, GUO Xiangwei, DU Shaotong, YANG Ming Journal of Electrical Engineering    2022, 17 (1): 78-85.   DOI: 10.11985/2022.01.011 Abstract （417）   HTML （13）    PDF （487KB）（847）       Knowledge map    Aiming at the new energy grid-connected inverter controlled by virtual synchronous generator technology (VSG), a uniform model of VSG actual output inertia and damping is proposed to quantitatively evaluate the inertia and damping provided by VSG to the large power grid. Firstly, different VSG connection modeling methods are analyzed, and a unified VSG control model structure is established. Then, an identification method of VSG key parameters based on multi innovation stochastic gradient method suitable for time domain is proposed. The system power dynamic information is excited by command power step and according to the relationship between the parameters of VSG control model, the system output inertia and equivalent damping parameters are dynamically identified, and then the error of the identification model is analyzed. Finally, the effectiveness of the proposed method is proved by simulation and comparison. Table and Figures | Reference | Related Articles | Metrics

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State of Charge Estimation with Adaptive Cataclysm Genetic Algorithm-recurrent Neural Network for Li-ion Batteries CHEN Cheng, PI Zhiyong, ZHAO Yinglong, LIAO Xuan, ZHANG Mingmin, LI Yong Journal of Electrical Engineering    2022, 17 (1): 86-94.   DOI: 10.11985/2022.01.012 Abstract （589）   HTML （38）    PDF （714KB）（1151）       Knowledge map    Accurate estimation of the state of charge (SOC) of lithium batteries is the basis for safe and stable operation of lithium batteries. The traditional back propagation (BP) neural network has low accuracy in estimating SOC, and the recurrent neural network (RNN) is easy to fall into local optimization. To work out these problems, a recurrent neural network (ACGA-RNN) combined algorithm based on an adaptive catastrophe genetic algorithm is proposed. The adaptive catastrophe genetic algorithm (ACGA) is utilized to optimize the initial weight and threshold of RNN and improve the global search ability of the optimal value, which effectively improves the estimation preciseness of the state of charge of lithium battery. Based on the experimental data from the charge and discharge test, the proposed ACGA-RNN combined algorithm, RNN algorithm, and GA-RNN algorithm are applied for SOC estimation of the lithium-ion battery respectively. The experimental results show that the estimation mean absolute error of ACGA-RNN combined algorithm obtains the best accuracy of SOC estimation compared with the traditional RNN and GA-RNN algorithms. The mean absolute error under the DST condition is 1.74%, which is lower than the estimation accuracy of traditional RNN (3.68%) and GA-RNN (2.49%). In addition, at 45 ℃ and 0 ℃, the mean absolute error of the ACGA-RNN combined algorithm is 1.75% and 2.05%, respectively, which meets the requirements of national standards. Therefore, the proposed ACGA-RNN combined algorithm has a good application value in SOC estimation of lithium batteries. Table and Figures | Reference | Related Articles | Metrics

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Research on Fault Diagnosis Method of Power Transformer Based on KPCA and IHHO-LSSVM SONG Liye, FAN Yiling, WANG Yizeng Journal of Electrical Engineering    2022, 17 (1): 95-103.   DOI: 10.11985/2022.01.013 Abstract （605）   HTML （20）    PDF （888KB）（1092）       Knowledge map    In order to improve the accuracy of power transformer fault identification, a power transformer fault diagnosis method based on kernel principal component analysis(KPCA) and improved Harris hawk algorithm(IHHO) optimized least square support vector machine(LSSVM) is proposed. First, use nuclear principal component analysis to preprocess the original fault data of the transformer to remove redundant data. Secondly, combine the Sigmoid deformation function and the point symmetry strategy to improve the traditional Harris hawk optimization(HHO), and combine with HHO and genetic algorithm(GA). The performance comparison proves that the accuracy of the solution and the speed of network convergence have been improved. Finally, IHHO is used to optimize the related hyperparameters of LSSVM to obtain a transformer fault diagnosis model combining KPCA and IHHO-LSSVM. The results show that the diagnosis accuracy of the proposed model is 95.6%, which is 8.9% and 16.7% higher than other fault diagnosis models, respectively, which proves that the proposed method can effectively improve the performance of transformer fault diagnosis. Table and Figures | Reference | Related Articles | Metrics