The Accurate Calculation and Analysis of Overcurrent under Modular Multilevel Converter DC Fault
Cai Yang1,2,3, Guo Wenyong1,2, Zhao Chuang1,2,3, Sang Wenjun1,2,3
1. Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China; 2. Key Laboratory of Applied Superconductivity Chinese Academy of Sciences Beijing 100190 China; 3. University of Chinese Academy of Sciences Beijing 100049 China
Abstract：The modular multilevel converter (MMC) is vulnerable to DC fault. Significant overcurrent will occur on the converter after the fault, which has a serious impact on the reliability of MMC. The accurate calculation of fault transient current is crucial to evaluate the overcurrent. This paper presents an precise method to calculate MMC fault overcurrent. The proposed calculation method considers both the influence of grid voltage and DC capacitor discharging. The equivalent model of MMC is established and analyzed, it can be concluded that the differential of arm voltage to time should be composed of capacitance term and submodule switch function term. Based on the method, the numerical solution of the fault current under the DC fault was calculated. Maximum and minimum possible overcurrent was derived. The precision of calculation method was verified by the electromagnetic transient (EMT) simulation results. Finally, the proposed approach was further compared with the two conventional calculation methods. It is verified that the proposed approach has significantly higher accuracy than the conventional methods. The proposed approaches provide a numerical evaluation tool for the design of MMC and DC fault protection.
蔡洋, 郭文勇, 赵闯, 桑文举. 模块化多电平换流器直流故障过电流精确计算与分析[J]. 电工技术学报, 2021, 36(7): 1526-1536.
Cai Yang, Guo Wenyong, Zhao Chuang, Sang Wenjun. The Accurate Calculation and Analysis of Overcurrent under Modular Multilevel Converter DC Fault. Transactions of China Electrotechnical Society, 2021, 36(7): 1526-1536.
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2021, Vol. 36 
