METHOD FOR CHARGING MODULAR MULTILEVEL CONVERTER

摘要

A method for charging a modular multilevel converter comprises: firstly, electrifying a direct current side of a converter; after voltages of submodules are stabilized, unlocking the converter, and conducting all the submodules, and then reducing the number of the conducted submodules in a phase unit; when over-current occurs on a bridge arm, temporarily increasing the number of the conducted submodules in the phase unit, so as to suppress the over-current; and after the voltages of the submodules are stabilized, continuously reducing the number of the conducted submodules until the number of the conducted submodules in the phase unit is finally equal to the number of working submodules of the bridge arm, so as to smoothly transit to a normal operation state. According to the method, the direct current side is charged, so that the voltages of the submodules reach a working voltage before the converter normally operates, and an impacting current is avoided in the process of the charging by using a proper control strategy.