Fast capacitor voltage balancing strategy based on system history operation information for MMC

Abstract

The conventional capacitor voltage balancing strategy of the modular multi-level converter (MMC) requires real-time sorting in each control cycle, which brings huge computational load to the controller. Therefore, a fast capacitor voltage balancing method for MMC is proposed. Based on the conventional strategy, this method combines the operating rules of the sub-module (SM), considering the voltages of SMs and historical information on charging and discharging of the capacitor. It selects the appropriate insert object and insertion process according to the relationship between the number of the switched-on and switched-off SMs in the last control cycle, and quickly forms the ordered sequence of SMs in the control cycle. The simulation results show that the proposed strategy can achieve voltage balancing with low computational complexity, significantly improve the system simulation speed, and effectively reduce the controller resources occupied by the balancing strategy.