A Modified Dual Active Bridge Bidirectional Converter With Full-Load-Range Soft Switching

Due to the environment deterioration and fossil energy depletion, i t has attracted more and more attention on applications of clean energy. Micro-grids and electric vehicles which are typical applications of clean energy have been widely concerned. Bidirectional DC-DC converter(BDC) is an important part of Micro-grids or electric vehicles. And as a typical BDC, the dual active bridge(DAB) attracts more and more attention..By inserting a small inductor between the transformer center tap and the midpoint of two split output capacitors in the dual active bridge topology, this paper proposes a modified DAB converter and a hybrid phase-shift(HPS) control scheme. The proposed hybrid phase shift(HPS) control scheme allows all power switches to achieve practical zero-voltage switching(ZVS) over the full-load-range in twice gain range, thereby significantly minimizing the switching losses and alleviatin g electromagnetic interference(EMI).The modified DAB converter and the derivation process of the topology are first presented. Based on the extended phase shift(EPS) and triple phase shift(TPS) modulation, The operating modes can be identified and its operating principles are also shown. In addition, the characteristics of the modified DAB converter such as soft-switching, power transfer and RMS current are investigated, and then the HPS control strategy, which combined with EPS and TPS is proposed. Th e guidelines for parameter design, the estimate of power losses and an effective control strategy are given as well. Finally, a 1.2-k W experimental prototype is built to verify the effectiveness of all proposals. When compared with the conventional DAB con verter, the advantages of the modified DAB converter, such as the full-load-range soft-switching and higher efficiency are also shown in this paper.