High-Efficient Operation for Modular Multilevel Resonant DC–DC Converters in Medium Voltage Applications With Wide Input Range and Wide Load Condition

The modular multilevel resonant dc–dc converters (MMRDCs) are becoming one of the most attractive candidates in medium voltage applications, but they would usually face technical challenges in high-efficient operation with wide input range and wide load condition. First, this article provides an elaborate review of the voltage control dimensions in MMRDC, and their corresponding operation principles, regulation capabilities, and efficiency influences for MMRDC are also analyzed respectively. Then for the wide input range, a tailored voltage regulation method combining both phase shift angle control and inserted submodule number control is proposed, and the optimal regulation principles of these two control dimensions are further investigated to realize high-efficient operation for MMRDC with wide load condition. Finally, the effectiveness of the proposed strategy is demonstrated through a simulation model and a full-scale MMRDC prototype with 9–18 kV input and 60 kW power rating.