Hybrid Predictive Control of Capacitor Voltage Balance Based on Modular Multi-level Converter

A hybrid control method for balance control of the sub-module capacitor voltage based on multi-level converter module (MMC) is proposed. According to state of the sub module and current of the converter bridge, the predictive value of the sub-modules capacitor voltage in the next action cycle is obtained. Taking the predictive absolute error limit of the capacitor voltage as the voltage deviation criterion, the sub-modules switching on/off scheme for the next action cycle is obtained. Proposed method can guarantee the balance of sub-modules capacitor voltage as well as the low switching frequency. In the end, 11-level MMC system is built in the PSCAD / EMTDC, and the simulation results verify the effectiveness of the proposed method.