Pre-charging control strategy of modular multilevel inverter

According to operation characteristics of mine hoist, a back-to-back modular multilevel converter composed of modular multilevel rectifier and modular multilevel inverter was used for control of mine hoist. In view of current research on pre-charging control for modular multi-level inverter through DC side was less, a pre-charging control strategy of modular multilevel inverter was proposed. Charging state of sub-module is controlled by controlling charging current, so that capacitor of the sub-module can be charged to meet voltage requirement of the modular multilevel converter in stable operation. Meanwhile, charging current and overvoltage generated in charging process are limited to safe range and charging time is the shortest. The simulation results verify effectiveness of the control strategy.