闭锁状态下MMC子模块电容充电升压机理及对策  

Boosting Mechanism and Countermeasures of MMC Sub-Module Capacitor Charging in Blocking State

作　　者：潘荣贞 廖其艳 王健 PAN Rongzhen;LIAO Qiyan;WANG Jian(Rongxin Huike Electrical Technology Co.,Ltd.,Anshan,Liaoning 114051,China)

机构地区：[1]荣信汇科电气技术有限责任公司,辽宁鞍山114051

出　　处：《南方电网技术》2018年第1期7-13,共7页Southern Power System Technology

摘　　要：针对模块化多电平换流器(modular multilevel converter,MMC)在闭锁状态下子模块电容充电升压的现象,对子模块过电压旁路保护策略提出改进意见。首先详细分析了柔直对称单极系统中,MMC阀侧发生接地故障且被闭锁后,健全相电压幅值被抬高等现象。由于直流线路存在分布电容的原因,健全相桥臂电容充电升压,本文总结了引起该充电过程的条件和因素,提出了闭锁状态下防止子模块过电压误旁路的新的保护策略,最后在一个三端柔性直流系统PSCAD模型上的仿真分析全面验证了闭锁状态下子模块充电升压的机理,所提出的子模块过电压旁路保护改进策略可以避免子模块误旁路,从而降低MMC的检修工作量。Aiming at proposing improvement to the protection strategy of submodule overvoltage bypass according to the condition that submodule capacitors are charged in modular multilevel converter(MMC)blocking state,the phenomena that the voltage magnitude of sound phase is raised are analyzed when a grounding fault occurs at valve side and MMC is blocked in an MMC-HVDC symmetrical monopolar bipolar system.Because there are distributed capacitances in DC lines,the voltage of sound phase arm capacitance is raised by charging.The conditions and factors to cause and influence the charging process are presented.Then a new protection strategy to prevent mistake bypass of submodule because of overvoltage in blocking state is proposed.Finally,simulation analysis is performed on a PSCAD model of a threeterminal MMC-HVDC system and the boosting mechanism of submodule charging in blocking state is fully verified.The proposed new protection strategy can prevent mistaken bypass of submodule in blocking state and reduce maintenance workload of MMC.

关 键 词：模块化多电平换流器 半桥子模块 电容电压 闭锁状 

分 类 号：TM743[电气工程—电力系统及自动化]