Variable-Frequency Explicit Model Predictive Control of Wide Band Gap DC/DC Converter with Critical Soft Switching

This research proposes a control scheme that ensures critical soft switching to improve the efficiency and power density of the DC/DC power converter. First, we analyze the boundary constraints of critical soft switching that are derived with the key parameters of the interlock time and threshold current for typical SiC and GaN devices. Then, a variable-frequency model predictive control strategy is proposed for synchronous DC/DC converters. The duty cycle and frequency are controlled by MPC to satisfy the critical soft switching constraints in every operating point. The explicit model predictive control method can be applied to increase the speed of optimization. The combination of Explicit Model Predictive Control (EMPC) and critical soft switching technique largely improves the efficiency and tracking accuracy of the system. Also due to the fast response of the MPC, the losses during the transient period can be further reduced without oscillation compared to the traditional PI controller. Finally, the theoretical analysis is validated by dedicated tests.