Fault grading diagnosis positioning method and system for MMC sub-module

The invention relates to a fault grading diagnosis positioning method and system for MMC sub-modules, and belongs to the technical field of modular multilevel converters. Diagnosis positioning is divided into three stages, namely fault phase positioning, fault bridge arm positioning and fault sub-module positioning, the three stages of positioning are progressive in sequence, positioning of the next stage is started after positioning of the upper stage is completed, the fault sub-module can be rapidly and accurately positioned without continuously monitoring and analyzing the voltage of all the sub-modules of each phase, so that the operation burden of the MMC controller is greatly reduced, and the fault sub-module can be rapidly and accurately positioned through sequential cooperation of three-stage positioning. 本发明涉及一种MMC子模块的故障分级诊断定位方法及系统，属于模块化多电平换流器技术领域，诊断定位分为三级，分别是：故障相、故障桥臂和故障子模块级定位，三级定位依次递进，当上一级定位完成后再启动对下一级的定位，而不需要对各相的所有子模块电压进行不断监测与分析，大大减轻了MMC控制器的运算负担，并且三级定位依次配合，能够快速精确地定位故障子模块。