Modular multilevel converter robust fault detection method based on sliding mode observer

The invention relates to a modular multilevel converter robust fault detection method based on a sliding mode observer. The modular multi-level converter comprises three same single-phase MMC equivalent circuit phase units; each single-phase MMC equivalent circuit phase unit comprises an upper bridge arm and a lower bridge arm; each bridge arm is formed by connecting N sub-modules with the same structure, a bridge arm inductor L and a bridge arm equivalent resistor R in series; and each sub-module comprises a half-bridge structure composed of two IGBTs with antiparallel diodes and a capacitorC. According to the method, the sliding mode observer is adopted, and based on a state space model, equivalent output error injection and other technologies, multi-level converter fault information reconstruction is realized; when a fault occurs, the system can still keep sliding mode motion, detection and isolation of the fault of the multilevel converter are achieved, and the problems that a traditional diagnosis method