This paper proposes a balancing control method for imbalanced load in multi-port converter based on a modular multilevel converter (MMC) topology. In the multi-port converter with imbalanced loads, the three-phase current is balanced by dividing voltage among the cells. However, the multi-port converter has a limitation of the compensation capability for the imbalanced load. This paper clarifies the theoretical limitation with the proposed divided voltage method of the compensation capability of the imbalanced load. The proposed method is demonstrated by a 200-V, 17-kW laboratory system in order to show the validity of the proposed method. In spite of the load imbalance, balanced three-phase input current is achieved and DC link voltage error becomes 0.11%.