基于比例和改进准谐振控制的MMC环流抑制策略

MMC Circulating Current Suppression Strategy Based on Proportional and Improved Quasi-Resonant Control

模块化多电平换流器(MMC)由于电容电压的波动会产生环流在相间流动,环流会增加能量损耗并对子模块中的绝缘栅双极晶体管(IGBTs)产生不良的影响。为抑制环流,基于环流的动态数学模型设计了一种能产生反向二倍频分量的比例控制器。针对环流中的高次谐波对传统的准谐振控制器进行了改进。对所提策略进行了仿真验证,仿真结果表明比例控制策略仅经过0.2 s后快速达到稳态抑制环流,改进后的准谐振控制策略相比于改进前THD值优化了3.56%,进一步降低了高频谐波分量,验证了所提策略的可靠性。

Modular multilevel converter(MMC)generates circulating currents flowing between phases due to fluctuations in capacitor voltage,which increases energy loss and adversely affects the insulated gate bipolar transistors(IGBTs)in the sub-modules.In order to suppress the circulating current,a proportional controller capable of generating inverse doubling components is designed based on the dynamic mathematical model of the circulating current.The conventional quasi-resonant controller is improved for the high harmonics in the circulating current.And the proposed strategy is verified by simulation,the simulation results show that the proportional control strategy quickly reaches the steady-state suppression of the circulating current after only 0.2 s.The improved quasi-resonant control strategy optimizes the THD value by 3.56%compared with the pre-improvement one,which further reduces the high-frequency harmonic components and verifies the feasibility of the proposed strategy.