中文摘要：

通过分析模块化多电平换流器（MMC）拓扑结构,提出一种MMC桥臂电流直接控制方案,该方案对MMC上/下桥臂电流实施独立控制。建立了MMC系统小信号传递函数模型,对桥臂电流反馈控制策略进行了分析与设计。以MMC并网逆变器为例,结合多层次电容电压平衡控制策略,得到了基于桥臂电流内环控制的MMC综合控制方案,以实现网侧电流控制及电容电压平衡控制。仿真结果表明,所提出的MMC桥臂电流直接控制方案具有优良的动静态特性,并能有效抑制三相内部环流,验证了该方案的可行性和有效性。

英文摘要：

By analyzing the topology of modular multilevel converters（MMCs）,an arm current direct control scheme for MMCs is presented to independently control the current through the upper or lower arm of an MMC.The small signal transfer function model of an MMC is built to analyze and design the feedback control scheme of arm current.Taking the grid-connected MMC inverter as an example and combined with the capacitor voltage balance control strategy,a comprehensive control scheme based on the arm current inner loop control is proposed to perform the grid current control as well as capacitor voltage balancing of an MMC.Simulation results show that the proposed arm current direct control scheme of MMC has excellent stead-state and dynamic characteristics;and it can effectively eliminate the three-phase inner circulating currents.The results clearly verified the feasibility and effectiveness of the proposed scheme.