Hierarchical Voltage Balancing Method for MMC Based on DCSM

This paper presents a hierarchical voltage balance control method for a hybrid modular multi-level converter based on half-bridge submodule and dual-capacitor submodule. This voltage balancing method reduces the control complexity of the existing voltage balancing method of the central controller but does not significantly increase the control complexity of the submodule controller. In dual-capacitor submodule, only some logic operations are added. Furthermore, the proposed method reduces the hardware requirements and communication data between the submodule and central controllers. The reduced hardware requirements refer to the hardware circuits used to implement communication functions. The proposed method is also applicable to multi-level converter, which only includes half-bridge submodules, but requires two adjacent half-bridge submodules to use the same submodule controller. Simulation and experimental results validate the feasibility and effectiveness of the proposed hierarchical voltage balance control.