不平衡网压下MMC子模块电压波动抑制策略

Voltage Fluctuation Suppression Strategy of MMC Submodule Under Unbalanced Network Voltage

针对不平衡网压下模块化多电平换流器(MMC)子模块电容电压波动问题,提出一种注入共模电压与环流的MMC子模块电压波动抑制策略。首先通过注入共模电压使系统工作在较高调制比状态,然后根据半桥子模块MMC的数学模型推导出注入共模电压后的桥臂功率解析式,从而减小桥臂功率波动,实现注入共模电压与环流的MMC子模块电压波动抑制。最后通过搭建的17电平MMC实验平台对所提策略进行有效验证,实验结果显示该策略可有效减少子模块电容电压波动幅值。

Aiming at the capacitor voltage fluctuation of modular multilevel converter(MMC) submodule under unbalanced network voltage,a voltage fluctuation suppression strategy of MMC submodule injected with common mode voltage and circulating current is proposed.Firstly,the system works in a high modulation ratio state by injecting common mode voltage.Then,according to the mathematical model of half bridge submodule MMC,the analytical formula of bridge arm power after injecting common mode voltage is deduced.From the perspective of reducing bridge arm power fluctuation,the voltage fluctuation of MMC submodule injected common mode voltage and circulation is suppressed.Finally,the proposed strategy is verified by the 17 level MMC experimental platform.The experimental results show that the strategy can effectively reduce the voltage fluctuation amplitude of submodule capacitance.