Selection Design of Low Frequency Voltage Ripple Suppression for MMC Sub-Module based on Split Capacitor

Modular multilevel converter (MMC) has been widely used in medium and high voltage fields. However, the low-frequency ripple power (fundamental and secondary) in the MMC submodule (SM) requires large capacity and volume capacitors to smooth the SM voltage, which limits its further application and the improvement of power density. In this paper, a split-capacitor decoupling SM topology is introduced, its working principle is explained and a set of selection flowchart is designed, so that the minimum device selection that meets the operation requirements can be obtained under given operating conditions, which effectively improves the converter power density. And the effectiveness of the selection is verified in the simulation.