不平衡状态下MMC双回路环流抑制策略  

Double-Loop Circulating Current Suppressing Strategy for Modular Multilevel Converter under Unbalanced Conditions

作　　者：张臣 叶华[1] 韦凌霄[2] 王春义 Zhang Chen;Ye Hua;Wei Lingxiao;Wang Chunyi(Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of EducationShandong University Ji’nan 250061 China;State Grid Beijing Electric Power Company Beijing 100031 China;State Grid Shandong Electric Power Company Ji’nan 250001 China)

机构地区：[1]电网智能化调度与控制教育部重点实验室(山东大学),济南250061 [2]国网北京市电力公司,北京100031 [3]国网山东省电力公司,济南250001

出　　处：《电工技术学报》2019年第9期1924-1933,共10页Transactions of China Electrotechnical Society

基　　金：国家重点研发计划资助项目(2016YFB0900502)

摘　　要：模块化多电平换流器(MMC)的内部环流将会增加换流器的功率损耗,降低桥臂容量利用率;同时加剧桥臂电流畸变,影响开关器件的安全运行。因此,需要采取有效的控制手段抑制环流。该文通过详细的相单元瞬时能量理论推导,得到MMC内部环流和环流抑制控制器输出电压间的交互作用会造成环流四倍频分量增加的结论。在基于准比例谐振调节器的环流抑制策略基础上,添加环流辅助控制回路,提出了一种环流抑制能力增强型的双回路环流抑制策略。通过合理整定调节器参数可以改善环流抑制控制器的闭环零极点分布,增强控制系统的稳定性,同时提高环流抑制控制器在谐振频率附近处的环流抑制能力。在PSCAD/EMTDC中搭建三相MMC详细仿真模型,验证了双回路环流抑制策略的正确性和有效性。The inner circulating current of modular multilevel converter (MMC) will increase the power loss and reduce the capacities utilization of the bridge inevitably. Even worse, the bridge current distortion will be intensified, which will endanger the safe operation. Therefore, it is necessary to suppress the inner circulating current. Via the more detailed phase-unit instantaneous energy analysis, this paper reveals that the quadruple-line frequency components of the inner circulating current will be increased due to the interaction between the circulating current at double line-frequency and the output voltage of the circulating current suppressing controller. Then, a suppression-enhanced double-loop circulating current suppressing strategy is proposed. Moreover, by reasonably tuning the controller parameters, the distribution of closed-loop poles can be improved, the system stability as well as the suppression ability can be enhanced significantly. A detailed three-phase MMC model is established in PSCAD/EMTDC environment, the correctness and effectiveness of the proposed strategy get verified.

关 键 词：模块化多电平换流器 内部环流 双回路环流抑制策略 参数整定 

分 类 号：TM721.1[电气工程—电力系统及自动化]