Abstract：Aiming at the direct current (DC) faults of the full-bridge modular multi-level converter-high voltage direct current (MMC-HVDC) transmission system, the detailed mathematical model is established. In addition, the mechanism and progress of the over-voltage or over-current stress of MMC-HVDC system are analyzed in depth. The results show that, during the DC pole-to-pole and unipolar earth fault, the positive- and negative-pole DC bus voltages of MMC-HVDC system mismatch the DC components of the MMC upper and lower arm voltages, which leads to rapid discharge of the arm capacitance. Consequently, the system will suffer serious over current. Therefore, an improved control strategy is proposed by separately controlling the upper and lower arms of the MMC during the DC fault. With the proposed method, the DC components of the upper and lower arm voltages will follow the change of the positive- and negative-pole DC bus voltages, which ensures the safe and stable operation of the MMC-HVDC system. The proposed control strategy realizes the effective simplification and unification of fault ride-through control under three typical DC faults. In addition, in order to further improve the economic operation capability of the MMC-HVDC system under the DC unipolar earth and disconnection faults, an optimized power allocation strategy is proposed. Finally, the simulation results in PSCAD/EMTDC verify the correctness and feasibility of the proposed improved control strategy and optimized power allocation strategy for the MMC-HVDC system under DC faults.
姚骏, 谭义, 裴金鑫, 熊小伏, 欧阳金鑫. 模块化多电平变流器高压直流输电系统直流故障改进控制策略[J]. 电工技术学报, 2018, 33(14): 3306-3318.
Yao Jun, Tan Yi, Pei Jinxin, Xiong Xiaofu, Ouyang Jinxin. Improved Control Strategy for DC Fault in Modular Multi-Level Converter-HVDC System. Transactions of China Electrotechnical Society, 2018, 33(14): 3306-3318.
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