Optimal Trajectory-Based Thermal Balance Control Strategy of Wide Input Voltage Dual Resonant Cavity LLC Converter for Vehicle Power Supply

DC-DC converters in electric vehicles require a wide input voltage range to address voltage fluctuations in power batteries. Thus, this paper proposes a dual resonant cavity converter to achieve a wide input voltage range. Firstly, three different modes are proposed by reconfiguring modulation schemes. The fundamental wave analysis method is used to derive different voltage gain models under three modes. Under this effect, wide input voltage characteristics are achieved by switching between these modes. Meanwhile, the sliding mode control is used to determine the switching frequency. Compared with the traditional control, the dynamic response speed is significantly improved. Moreover, the optimal trajectory-based thermal balance control strategy is proposed to achieve balanced heat production. Therein, optimal trajectory control is used to determine the switching of resonant cavity and topology modes. Therefore, the safety of the converter can be improved due to thermal balance. At the same time, both the resonant current and output voltage fluctuations during mode switching are significantly reduced. Finally, the correctness and feasibility of the proposed topology and strategy are verified through simulation and experimental results.