适用于大规模MMC的分布式控制系统及两级均压策略

在高压大功率应用场合,模块化多电平换流器(MMC)每个桥臂子模块数量较多,造成其控制系统硬件构成复杂、协调控制困难。文中提出一种适用于大规模MMC的模块化结构的分布式控制系统:该控制系统由一个主控制单元和若干个桥臂控制单元构成,每个桥臂控制单元又由若干个阀组控制单元组成,每个阀组控制单元只控制较少数量的子模块。该结构有效降低了主控制单元和桥臂控制单元的控制压力,易于实现与扩展。针对该控制系统,提出一种包含阀组间均压和阀组内均压的新型均压策略。在三相41电平MMC实验样机上对所提出的控制系统及均压策略进行了验证,实验结果证明了所述控制系统的可行性及均压策略的有效性。

Distributed Control System and Two-layer Voltage Balancing Method for Large-scale Modular Multilevel Converters

In high-voltage and large-power applications, the number of sub-modules in large-scale modular multilevel converters (MMCs) is huge, which makes the control system difficult in hardware design and coordination control. In order to solve this problem, a control system which consists of one central control unit and several arm control units is proposed. Each arm control unit consists of several valve-group control units, each of which controls few sub-modules. This distributed control system is easily extended, reducing tasks of the central control unit and arm control units. According to the proposed distributed control system with multiple control units, a new voltage-balancing method can be divided into two parts: the internal voltage balance and the external voltage balance. Finally, a three-phase-41-level MMC prototype is designed to verify the proposed control system and the voltage-balancing method. The experiments show that the proposed control system is feasible and the proposed voltage-balancing method is valid.