Closed-loop voltage control of a GaN-based modular multilevel clamped capacitor converter

The Modular Multilevel Clamped Capacitor Converter (MMC3) is an attractive switched-capacitor converter topology with desired features including high voltage conversion ratio, high power density and modularity. However, its application is hindered because of the lack of output voltage regulation. This paper proposes a closed-loop voltage control strategy for the MMC3 based on a detailed time-domain model of the converter. The proposed strategy relies on the impact of Pulse Dropping Technique (PDT) on the MMC3 conversion ratio to regulate the output voltage. A compact MMC3 prototype is designed and built with GaN FETs and tested up to 40 W. The developed model and proposed control strategy are validated by simulation and experimental studies.