An Adaptive Submodule Voltage Balancing Method for Modular Multilevel Converter in HVDC Transmission System

Modular Multilevel Converter (MMC) is considered a promising circuit topology for high voltage and high power applications. There is a trade-off between submodule (SM) capacitor voltage balancing and switching frequency. In this paper, an adaptive SM capacitor voltage balancing method is proposed based on that different arm currents have different charging or discharging capabilities. The algorithm can reduce switching frequency without affecting capacitor voltage balancing. The threshold current selection and average switching frequency calculation of power device are presented which provide theoretical basis to system design. Finally, the simulation results validate the effectiveness of the proposed method.