Control Strategy for Balancing Capacitor Voltage of Modular Multilevel Converter

The Modular Multilevel Converter (MMC), based on cascaded multi-module structure, is suitable for high-voltage/power applications. However, among hundreds of modules, their voltage-balancing is a key problem which is attracting scholars' much attention. Therefore, in this paper, a control strategy based on PI controller is proposed for balancing capacitor voltages of Modular Multilevel Converter (MMC). The proposed control strategy includes the voltage-balancing and circulating current-limiting links. The effectiveness of the strategy is conformed using Matlab/Simulink platform. The simulation results show that the fluctuation of capacitor voltages as well as the circulating current can be confined into acceptable range. In addition, the MMC's switching frequency and system loss can be reduced significantly, since the equivalent switching frequency is promoted to a great extent.