Design Method for Reducing the Capacitor Volume of Modular Multilevel Converter Submodules

The Modular Multilevel Converter (MMC) is widely used in medium and high voltage applications. To filter out lowfrequency ripple power, the capacitor of the submodules is often chosen to be quite large, resulting in an increased size of the submodules and a reduced power density of the MMC. This paper introduces the working principle of the split capacitor topology to suppress voltage ripple, selecting circuit parameters that meet the operational requirements of the system. Based on these parameters, thermal design, magnetic design, and other hardware designs are performed. Without increasing the voltage ripple of the submodule capacitor, the split capacitor submodule reduces the volume of the submodule capacitor by approximately 20%, and its feasibility is verified through experiments.