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 (T
²
-DAB) converter possesses high input voltage and large output current capacity, which can be adopted to constitute a high-power-density dc transformer. However, when employing conventional phase-shifted (PS) control strategy, zero-voltage switching (ZVS) turn-on is easily lost under light-load and voltage-mismatching situations. Hence, this article presents an optimized asymmetrical duty-cycle modulation strategy for T
²
-DAB converter, ensuring ZVS for switches and reducing the current stress over wide power and voltage ranges. The detailed model is established with a time-domain analysis method, and ZVS constraints are given with the particular consideration of dead time and parasitic capacitances of switches. Then, the MATLAB optimization toolbox is adopted to calculate the optimum duty cycle and PS angle, and the specific control scheme is introduced. Finally, a 2-kW prototype is built to verify the theoretical analysis, whose input voltage ranges from 480 to 720 V and output voltage is 200 V. 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.