Electric Power ›› 2022, Vol. 55 ›› Issue (5): 84-93.DOI: 10.11930/j.issn.1004-9649.202107017

• Power System • Previous Articles     Next Articles

Medium-High Frequency Impedance Modeling of MMC and System Stability Analysis Considering Voltage Measurement Characteristics

LI Qinan1,2, XIA Yongjun3, ZHANG Xiaolin1,2, SUN Baokui1,2, SUN Huadong4, ZHANG Fan1,2, LI Lanfang1,5, YANG Yuefeng1,2, HAN Qingtao6   

  1. 1. NARI Group Corporation (State Grid Electric Power Research Institute) Co., Ltd., Nanjing 211006, China;
    2. Beijing DC Transmission and Distribution Engineering Technology Research Center (China-EPRI Electrical Engineering Co., Ltd.), Beijing 102200, China;
    3. Electric Power Research Institute of State Grid Hubei Electric Power Co., Ltd., Wuhan 430061, China;
    4. China Electric Power Research Institute, Beijing 100192, China;
    5. China EPRI Science & Technology Co., Ltd., Beijing 102200, China;
    6. State Grid Hubei DC Inspection Company, Yichang 443001, China
  • Received:2021-07-06 Revised:2021-10-27 Online:2022-05-28 Published:2022-05-18
  • Supported by:
    This work is supported by Science and Technology Project of SGCC (Research on Dynamic Power Coordination Control of VSC/LCC HVDC Parallel System and Near Area Power Grid, No.5100-202022011A-0-0-00)

Abstract: In MMC impedance modelling, the existing research does not take into account the influence of the capacitive voltage transformer (CVT) measurement characteristics on the mid and high frequency bands of the MMC impedance, which may reduce the accuracy of the stability analysis of the flexible HVDC transmission system. By taking the south channel unit of the Yu’E flexible HVDC project as the research object, and based on an analysis of the influence of stray capacitance on the measurement characteristics of a 500kV fast saturated CVT, a MMC impedance modelling method is proposed using the multi-harmonic linearization method. The impedance analysis method is used to analyze the influence of the CVT broadband measurement characteristics on the stability of the HVDC system when the MMC station is connected to different AC systems and operates at different steady-state operating points. The results show that the CVT broadband measurement characteristics will cause the oscillation frequency of the system to change under certain working conditions. Through PSCAD/EMTTDC simulation, it is verified that the proposed MMC impedance model, which takes into account the CVT broadband measurement characteristics, can improve the accuracy of the stability analysis of the flexible HVDC system.

Key words: modular multilevel converter (MMC), multi-harmonic linearization, impedance, CVT, broadband measurement characteristics