Analysis of the Flying-Capacitor Modular Multilevel Converter Based on SiC MOSFET

Reducing the capacitor voltage ripple amplitude of the modular multilevel converter (MMC) submodule is expected to reduce the capacitance of the module capacitors, which is very important for the increase of the power density. In the method of reducing capacitor voltage fluctuations of MMC submodule, flying-capacitor modular multilevel converter (FC-MMC) has gained extensive attentions because of its good performance. It is characterized by the connection of upper and lower arm middle taps through a flying capacitor in per phase arm. However, the reduction of the capacitance of flying capacitor requires an increase in switching frequency, which means high switching loss for the converter. Therefore, SiC MOSFET has a good application prospect in FC-MMC due to its low switching loss. This paper mainly compares the capacitor voltage fluctuation between FC-MMC and MMC, and the advantages of SiC MOSFET in FC-MMC applications.