模块化多电平换流器HVDC直流侧故障控制保护策略

摘要

模块化多电平换流器（MMC）是电压源换流器（VSC）的一种新型拓扑。由于MMC与VSC拓扑结构的差异,二者的直流系统故障机制也有所区别,有必要对其故障特性进行深入分析以进行保护设计。文中介绍了MMC的拓扑结构及工作原理,通过比较基于MMC与VSC直流输电系统的故障特征差异,分析了MMC-HVDC不同类型直流线路故障对系统的影响,并进一步根据交直流系统电气参数变化情况和子模块电容的放电机制,提出了控制保护设计的基本要求及相应的控制保护策略。在电磁暂态仿真软件PSCAD/EMTDC下进行了直流侧单极接地、断线和极间短路故障的仿真研究,仿真结果验证了故障机制分析的正确性及控制保护策略的有效性。%Modular multilevel converter（MMC） is a novel topology of voltage source converter（VSC）.Because of the topological differences between MMC and VSC,the fault mechanisms of the two DC systems have many discrepancies;as such it is necessary to have detailed study of the faults characteristics in order to design the corresponding protection schemes.The MMC topology and working principles are introduced.Comparing the fault characteristics of DC transmission system based on MMC with VSC,the impact of different DC faults of MMC-HVDC is analyzed.Furthermore,based on the variations of the electrical parameters in the AC-DC system and the discharge mechanism of submodules,the basic design requirements for protection with the corresponding control and protection strategies are proposed.The simulation platform of DC faults of MMC-HVDC is built in the electromagnetic transient simulation software PSCAD/EMTDC.Simulations including single-line to ground fault,line break fault and line-to-line fault are carried out to validate the analysis on the fault mechanisms and the effectiveness of the proposed control and protection strategies.