Capacitor Voltage Ripple Suppression of the Switched Capacitor Modular Multilevel Converter

Abstract

The modular multilevel converter (MMC) is the most promising topology for the medium/high-voltage applications. Recently, a novel type of switched-capacitor MMC (SCMMC) has been proposed, which has inherent capacitor voltage balancing function and higher power density. However, like the conventional MMC, the emerging SCMMC suffers from sub-module (SM) capacitor voltage ripple. Since the SCMMC does not have bulky and heavy arm inductors, the internal dynamics of the SCMMC is significantly different from that in the conventional MMC. Therefore, the existing SM capacitor voltage ripple suppression methods cannot be applied on the SCMMC. To solve the issues, a capacitor voltage ripple suppression method is proposed for the SCMMC, which is compatible with the characteristics of switched capacitor. The proposed method works for the emerging SCMMC with middle SM as well. Simulation results are presented to verify the effectiveness of the proposed method.