Hybrid SOC Balancing Control Strategy in MMC-UPQC System with Distributed Energy Storage

The modular multi-level converter based unified power quality controller (MMC-UPQC) with distributed energy storage can be directly connected to the medium and high voltage power grid for power quality regulation. The stable operation of the MMC-UPQC system needs to maintain the voltage of the DC ports in MMC. Based on the analysis of the topological structure of the MMC-UPQC system, this paper proposes a SOC balancing control strategy for sub-module battery, which combines the additional voltage control and sorting method. Simulation results verify the feasibility of the proposed control method.