Auxiliary Strategy for DC Fault Clearing of Low Capacitance
Fan Qiang1, Yu Yongjie2, Xia Jiahang1, Zhao Chengyong1, Xu Jianzhong1
1. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing 102206 China; 2. State Grid Zhejiang Hangzhou Qiantang New District Power Supply Company Hangzhou 310000 China
Abstract：The current injection method can reduce the capacitance value of bridge arm sub modules (SMs), thereby reducing the volume and weight of MMC, and realizing the lightweight of MMC. Based on the theoretical analysis of the characteristics of low capacitance MMC in DC fault conditions, it is pointed out that the discharge speed of SM sunder low capacitance is fast when other parameters remain unchanged, which may lead to low voltage blocking of SMs during the DC fault clearing process. From the perspective of equivalent charge, a DC fault clearing strategy based on low capacitance half bridge MMC is proposed. By adjusting the total number of SMs in each phase according to the capacitance reduction ratio in MMC during the fault clearing process, the discharge capacity of the SM capacitors can be effectively reduced and the system recovery can be accelerated. A simulation program is built in PSCAD/EMTDC simulation environment, and the effectiveness of auxiliary strategy for DC fault clearing in low capacitance MMC is verified.
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2022, Vol. 37 
