【摘要】 模块化多电平换流器(MMC)在中、高压能量交换系统中应用越来越广泛。当MMC用于中低压配电网领域,电网电压的不平衡会产生负序电流,引起MMC桥臂环流增加和功率、直流电压的波动,严重时可能会影响换流器的运行特性。为确保换流器的安全运行及提高电能传输质量,研究MMC在电网电压不平衡状态下的控制策略尤其关键。首先对比分析电网电压不平衡时对MMC和传统二电平VSC内外特性所造成的影响;然后提出一种基于MMC桥臂电流的统一电流控制器,将MMC的交流侧电流和内部不平衡环流同时控制,不需分离电流分量,减少环流抑制器,整体控制系统得以简化,响应速度快;最后,在PSCAD/EMTDC中搭建5电平MMC仿真模型,验证所提控制策略的可靠性和有效性。更多还原

【Abstract】 The modular multilevel converter( MMC) are more and more important in medium/high-voltage energy conversion systems. When MMC is used in low voltage distribution networks,it gives rise to the existence of negative-sequence current,increasing the circulating currents and the ripples in power and dc voltage under the unbalanced grid voltages,which may affect the operational performance of MMC seriously. In order to ensure the safety of the converters and enhance the quality of power transmission,an unbalance control strategies is crucial for MMC. Firstly,the impact on the internal and external characteristics between MMC and the traditional twolevel VSC under imbalance grid voltage were compared; Then a unified current controller based on the current of MMC bridge arm was proposed. The AC side current and the internal unbalanced current of MMC controlled together with the current component is not separated. The overall control system was simplified and the response speed is fast; finally,simulation platform of MMC with 5 levels was built in PSCAD/EMTDC,and the simulation results verify the correctness and the effectiveness of the proposed method.更多还原