Improved Control Strategy of Triple-Voltage Three-Phase DAB (T2-DAB) Converter for Current Stress and Zero-Voltage-Switching Optimization

Three-phase triple-voltage dual-active-bridge (T2-DAB) converter possesses high input voltage and large output current capacity, which can be adopted to constitute high-power -density DC transformer. However, when employing conventional phase-shifted control strategy, ZVS turn-on is easily lost under light-load and voltage-mismatching situation. Hence, this paper presents an optimized asymmetrical duty cycle modulation strategy for T2-DAB converter, to ensure ZVS for switches and reducing the current stress over wide power and voltage ranges. The detailed model is established with time-domain-analysis method, and ZVS constraints are given with the particular consideration of dead time and parasitic capacitances of switches. Then, Matlab optimization toolbox is adopted to calculate the optimum duty cycle and phase-shifted angle, and the specific control scheme is introduced. Finally, a 2kW prototype is built to verify the theoretical analysis, whose input voltage ranges from 480V to 720V and output voltage is 200V. The experimental results show that the proposed optimized control scheme can realize ZVS turn-on for all switches over wide voltage and power ranges, and the efficiency is improved especially under light-load and voltage-mismatching situation.