Control Strategy of Three-level Resonant Converter with Wide Output Voltage Range

CLLC resonant converters have a wide range of applications in electric vehicle charging piles and DC transmission systems due to their excellent soft-switching characteristics, in these fields, the converters need to withstand high input voltages, but the increase of the converter input voltage is limited by the voltage withstand capability of the switching devices, and the cost of the high-voltage withstand switching devices is generally high, so the industry usually adopts a multilevel structure to reduce the voltage stress of a single switching device. In this paper, neutral point clamped and flying capacitor(NPC/FC) three-level CLLC resonant converter is used, four modulation strategies and a multimodal control strategy are proposed to realize a wider voltage output range of the CLLC resonant converter. Finally, based on Matlab/Simulink, the feasibility of the modulation strategies and the closed-loop control strategy is verified.