Current Stress Optimization in Buck-Boost Mode Based on New Extended Phase-Shift Dual Active Full-Bridge Converter

To reduce the current stress of dual active full-bridge converters in the buck-boost mode, a current stress optimization control strategy based on new extended-phase-shift modulation is proposed. First, the phase shift between the output high-level voltages at both ends of the transformer is defined as the external phase shift angle. Then, the working characteristics of the converter are compared and analyzed when the internal phase shift angle is on different sides of the transformer in the voltage buck-boost mode. According to the relationship between the phase shift angles, working modes are divided into three types, and the current stress expression and power model are obtained. Moreover, the improved working mode is obtained by comparative analysis, and the optimal phase shift combination of current stress is obtained by using Lagrange multipler method algorithm. Finally, an experimental platform is established to verify the converter in the buck-boost mode. The experimental results show that the current stress optimization control strategy significantly reduces the current stress of the converter in the buck-boost mode.