Power Distribution Control between Cells with Imbalanced Load for Modular Multilevel Multiport Converter

This paper proposes a balancing control method for load imbalance in one arm of a multiport converter based on a modular multilevel converter (MMC) topology. In the multiport converter with load imbalance, a balanced three-phase current is achieved thanks to power distribution control. However, the multiport converter has a limitation on the amount of load imbalance that can be compensated. This paper derives the theoretical limitation of the compensation capabilities using the proposed balance control for the load imbalance. The proposed control method is demonstrated by simulation, showing that balanced three-phase grid current is obtained in spite of the load imbalance and that the DC link voltage error is limited to 1.4%. In addition, simulation and experimental results clarify that the proposed controller has larger compensation capability for the load imbalance compared to the conventional control strategy.