State-Space Modeling and Control of the 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. The proposed strategy relies on the impact of Pulse Dropping Technique (PDT) on the MMC3 conversion ratio to regulate the output voltage. State-space small signal models and transfer functions are derived for both the open-loop MMC3 and the MMC3 with the proposed control strategy. The developed model and proposed control strategy are validated by simulation and experimental studies.