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LI Ming,ZHANG Xing,ZHANG Hang,ZHANG Haizheng,GUAN Weiqi,ZHAO Wei.Modeling and Analysis of VSG Output Impedance and Small-signal Based on Virtual Steady-state Synchronous Impedance[J].JOURNAL OF POWER SUPPLY,2018,16(6):11-17
Modeling and Analysis of VSG Output Impedance and Small-signal Based on Virtual Steady-state Synchronous Impedance
Received:July 31, 2018  Revised:November 22, 2018
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DOI:10.13234/j.issn.2095-2805.2018.6.11
Keywords:grid-connected inverter  virtual steady-state synchronous impedance  output impedance  virtual synchronous generator  small-signal model
Fund Project:National Key R&D Plan (2016YFB0900300); The Natural Science Foundation of China (51677049)
                 
AuthorInstitutionEmail
LI Ming School of Electrical Engineering and Automation, Hefei University of Technology, Hefei , China
ZHANG Xing School of Electrical Engineering and Automation, Hefei University of Technology, Hefei , China honglf@ustc.edu.cn
ZHANG Hang School of Electrical Engineering and Automation, Hefei University of Technology, Hefei , China
ZHANG Haizheng School of Electrical Engineering and Automation, Hefei University of Technology, Hefei , China
GUAN Weiqi School of Electrical Engineering and Automation, Hefei University of Technology, Hefei , China
ZHAO Wei Sungrow Power Supply Co., Ltd, Hefei , China
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Abstract:
      The virtual synchronous generator(VSG) is attracting increasing attention owing to its capability to simu-late the operation characteristics of a synchronous generator. In general, since the VSG automatically adjusts the frequency and voltage independently by the droop control, there exist some problems, e.g., the active and reactive powers are susceptible to coupling oscillations. Note that the virtual steady-state synchronous impedance scheme is capable of adjusting the output impedance characteristics of an inverter, thus it is an effective solution for suppressing the power coupling oscillations. In this paper, the basic principle of VSG control strategy based on the virtual steady-state synchronous impedance was introduced at first, and the VSG output impedance characteristics under this scheme were analyzed. It was found that the output impedance under this scheme can be determined by the preset virtual steady-state synchronous impedance, and it was independent of parameters such as the inverter's filter and closed-loop controller. Then, by establishing a small-signal model of the inverter, it was concluded that the virtual steady-state synchronous impedance can increase the characteristic root-damping ratio of the VSG system in the low-frequency domain and effectively suppress the power coupling oscillations. Finally, with the combination of simulations using Matlab/Simulink and an experiment, the correctness of the theoretical analysis of VSG control strategy based on virtual steady-state synchronous impedance was verified further.
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