Optimized distribution method for power device conduction loss in hybrid modular multilevel converter

To promote the reliability of the hybrid modular multilevel converter consisting of half-bridge sub-modules (HBSMs) and full-bridge sub-modules (FBSMs), optimized power loss distribution on devices in HBSMs and FBSMs is investigated. At first, the different charging and discharging characteristics of HBSMs and FBSMs for hybrid MMC with the traditional control method are analyzed, and, the conduction loss distribution on power devices in hybrid MMC is calculated. To reduce the conduction loss of the lower IGBTs in the HBSMs, a new control method based on the flexible regulation of the average switching function of HBSMs and FBSMs is proposed. The interaction mechanism of HBSMs' average switching function on the conduction loss distribution is analyzed, and an optimal assignment method is derived to reduce the conduction loss of the lower IGBTs in the HBSMs. Finally, simulation results using PLCES and MATLAB/Simulink are presented to verify the analysis and proposed method.