Abstract Modular Multilevel Converters(MMC) will have the positive, negative and zero sequence second harmonic circulating current in the flexible HVDC system under asymmetric AC voltages. Zero-sequence can not cancel each other in the three-phase leg, and will flow into the high-voltage DC side, which will affect the other converter station in flexible HVDC system. On this basis, a control strategy to suppress the zero sequence second harmonic circulating current was presented. For the Submodule(SM) capacitor voltage fluctuation will increase under unbalanced grid fault, SM capacitor voltage control method which injects the negative sequence second harmonic circulating current was presented. Simulation model of MMC-HVDC is built in Matlab/Simulink and verify the correctness of the algorithm.
Wu Liao,Shoudao Huang,Sheng Huang等. Unbalanced Grid Fault Ride-through Control Method of HVDC Power Transmission Based on Modular Multilevel Converters[J]. Transactions of China Electrotechnical Society, 2015, 30(12): 197-203.
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