模块化多电平换流器无锁相环的环流抑制控制策略

Circulation Current Suppressing Control Strategy of Modular Multilevel Converter without Phase Lock Loop

模块化多电平换流器(MMC)由于自身结构的特点使得三相桥臂存在相间环流,环流的存在使得三相桥臂电流产生谐波,从而导致系统成本增加,损耗增大。通过分析MMC的基本原理和对MMC控制系统数学模型的推导,设计了一种无锁相环结构的MMC控制系统,该系统既满足了MMC主控制电路设计需求,也能够运用于MMC环流抑制控制器的设计。这种无锁相环结构控制系统的设计,有效地减少了系统的参数选取,同时实现系统有功、无功的独立解耦控制。通过仿真分析,证明了设计的环流抑制控制器的有效性,为MMC系统的稳定运行提供了一种新的思路。

The circulation current is aroused in the three-phase bridge arm due to the structure of modular multilevel converter, which may cause the harmonic wave of three-phase bridge arm current, thus increasing the cost of the system and power loss. Through the analysis of the basic principle of MMC and the mathematical model of MMC control system, this paper designs a kind of MMC control system without phase-locked loop structure, which not only satisfies the MMC main control circuit design, but also may be applied to MMC circulation inhibition of controller design. The control system without phase-locked loop can reduce the system parameter selection effectively, and realize the independent decoupling control of active and reactive power.Simulation analysis verifies the effectiveness of the proposed control strategy and provides a new approach for the stable operation of the MMC system.