Fault Current and Voltage Estimation Method in Symmetrical Monopolar MMC-based DC Grids  

作　　者：Jingqiu Yu Zheren Zhang Zheng Xu 

机构地区：[1]IEEE [2]Department of Electrical Engineering,Zhejiang University,Hangzhou,China

出　　处：《Journal of Modern Power Systems and Clean Energy》2022年第5期1401-1412,共12页现代电力系统与清洁能源学报（英文）

摘　　要：Symmetrical monopolar configuration is the prevailing scheme configuration for modular multilevel converter based high-voltage direct current(MMC-HVDC) links, in which severe DC overvoltage or overcurrent can be caused by the DC faults. To deal with the possible asymmetry in the DC faults and the coupling effects of the DC lines, this paper analyzes the DC fault characteristics based on the phase-mode transformation. First, the DC grid is decomposed into the common-mode and the differential-mode networks. The equivalent models of the MMCs and DC lines in the two networks are derived, respectively. Then, based on the state matrices, a unified numerical calculation method for the fault voltages and currents at the DC side is proposed. Compared with the time-domain simulations performed on PSCAD/EMTDC, the accuracy of the proposed method is validated. Last, the system parameter analysis shows that the grounding parameters play an important role in reducing the severity of the pole-to-ground faults, whereas the coupling effects of the DC lines should be considered when calculating the DC fault currents associated with the pole-to-pole faults.

关 键 词：Symmetrical monopolar DC grids modular multilevel converter(MMC) pole-to-ground fault pole-to-pole faults phase-mode transformation fault current and voltage estimation 

分 类 号：TM721.1[电气工程—电力系统及自动化]