1. School of Electrical Engineering Beijing Jiaotong University Beijing 100044 China; 2. Beijing Engineering Research Center of Electric Rail Transportation Beijing 100044 China; 3. State Grid Shanxi Xinzhou Electric Power Company Xinzhou 034001 China; 4. Sate Grid Energy Research Institute Co. Ltd Beijing 102209 China
Abstract Microgrids are an effective form of organizing and utilizing distributed power sources, and are also an important component of new power systems. The AC-DC microgrid combines the characteristics and advantages of both AC and DC microgrids. However, under the dynamic interaction between different types of power electronic converters and the power grid, AC-DC microgrids are prone to trigger broadband oscillation problems, seriously threatening the safe and stable operation of the system. The analysis of microgrid oscillation problems in existing studies is mainly based on impedance analysis and feature analysis, but both methods have certain limitations. Therefore, this article conducts research on modeling and analysis methods for oscillation problems in AC-DC microgrids based on frequency domain impedance network models. Firstly, based on the state space method, impedance models of various devices in the AC-DC microgrid system are established. Then, the various devices in the system are connected according to the topological relationship of the system, and an equivalent impedance network model of the AC-DC microgrid system in the frequency domain is established. Based on the principles of electrical networks, the node frequency domain admittance matrix and loop impedance frequency domain matrix of the system are calculated. Secondly, based on the frequency domain mode analysis method, indicators for the degree of node/loop oscillation participation and sensitivity indicators for equipment and control parameters of the AC-DC microgrid are established. The analysis method for the AC-DC propagation characteristics of oscillation is provided, which facilitates the clarification of the system oscillation mechanism and key influencing factors. Finally, the effectiveness of the above frequency domain impedance network modeling and oscillation stability analysis methods is verified through Matlab/ Simulink time-domain simulation and example analysis.
Wu Xiangyu,Zhang Xiaohong,Shang Zixuan等. Research on the Oscillation Problem of AC-DC Microgrids Based on Frequency Domain Impedance Network Modeling and Analysis[J]. Transactions of China Electrotechnical Society, 2024, 39(8): 2294-2310.
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2024, Vol. 39 
