模块化多电平换流器新型桥臂环流抑制策略研究

为抑制模块化多电平换流器(Modular Multilevel Converter,MMC)的内部环流,介绍了一种新型的桥臂环流抑制策略,包括其MMC改进拓扑、环流抑制方法及电压校正模块(Voltage Correcting Module,VCM)的稳压控制方法。为便于工程应用,提出了该策略的VCM冗余控制方法,并对VCM进行了参数设计,包括子模块电压设计和支撑电容容值设计。仿真结果说明了所提VCM参数设计合理,验证了该冗余控制方案可在维持VCM电压稳定的基础上有效抑制换流器的桥臂环流。该方案适用于所有MMC系统,在使用IGBT串联MMC的高压大容量场合优势明显。

A novel bridge arm circulating current restraint strategy for modular multilevel converter

For restraining inner circulating current in modular multilevel converter (MMC), this paper presents a novel restraint strategy for bridge arm circulating current, including improved topology of MMC, circulating current restraint method, constant voltage control of voltage correcting module (VCM). Second, for engineering applications, this paper proposes a redundancy control method of VCM, and the parameters of VCM are designed, including modular voltage and support module capacitance value. Simulation results show the reasonableness of the design of the proposed VCM parameters and verify the redundancy control scheme can maintain VCM voltage stability as well as effectively restrain bridge arm circulating current of converter. The proposed scheme applies to all MMC system and has obvious advantages in case of high voltage and large capacity like IGBT connecting MMC in series.