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以MMC的动态模型为出发点,分析了子模块电压波动与MMC交流侧频率、交流侧输出电流幅值关系,提出了一种低频工况下MMC电容电压波动抑制控制策略.该控制策略通过在MMC交流侧注入方波共模电压分量和正弦环流分量对电容电压波动进行抑制,注入的环流分量由共模频率分量和共模三次谐波分量组成.仿真表明,该控制策略不仅能有效抑制子模块电容电压的波动,改善MMC输出电压的波形,而且能够使系统稳定运行.“,”To deal with the significant voltage fluctuation under low frequency conditions, analysis is made based on the power in the upper and lower arms, the relationship between the capacitor voltage fluctuation and the amplitude of the circular current, the frequency of ac-side. A control strategy based on injection of a square-wave common-mode voltage at the ac-side and a circulating current within the phase-legs to attenuate the low-frequency components of the SM capacitor voltage is proposed. The frequency spectrum consists of components in the vicinity of the common-mode frequency and third harmonic of the common-mode frequency. The simulation results show that this method can effectively suppress the ripple of the capacitor voltage and enhance the quality of the output voltage.