THE CONTROL SYSTEM AND METHOD OF MMC SYSTEM FOR DECREASING SWITCHING FREQUENCY

摘要

The present invention relates to a system for controlling a multi-level converter including one or more sub-modules including a semiconductor switch and a capacitor to form an output voltage. The system comprises: a voltage setting unit which sets a maximum output voltage of the multi-level converter; a determination unit which determines the number of sub-modules for satisfying the maximum output voltage set in the voltage setting unit; a sorting unit which measures capacitor voltage values of the sub-modules and sorts the sub-modules in ascending order or descending order in accordance with the measured voltage values; and a control unit which switches the sub-modules sorted in the sorting unit as many as the number determined in the determination unit. According to the present invention, the module-type multi-level converter is operated at a low switching frequency and the pulsating voltage is controlled. And thus operation efficiency of the converter is improved.