A Quasi-Single-Stage AC-DC Converter Based on Resonant Semi-Dual-Active-Bridge With Decoupled Control and Fixed Switching Frequency

In this article, a resonant semi-dual-active-bridge (semi-DAB) quasi-single-stage ac-dc converter is proposed. Its multimode control strategy with smooth transition is presented. Four decoupled resonant inductor current modulation modes with fixed switching frequency control strategy are given. The resonant tank is designed in an optimized way for better performance and higher conversion efficiency. The primary side switches can achieve zero voltage switching within entire ac line cycle including the zero crossing point of ac input voltage with the proposed fixed switching frequency control. In addition, the root mean square value of the resonant inductor current, the maximum current stress of switches and the turn-off current are compared with other modulation strategies under different operating conditions. The power transfer ability, mode transition mechanism and control strategy are also analyzed. A prototype of 220 V(ac), 270-400 V(dc), P_rated = 1000 W was built to verify the effectiveness of the proposed modulation and control strategy.