Bidirectional Buck–Boost Current-Fed Isolated DC–DC Converter and Its Modulation

In this article, a bidirectional buck-boost current-fed isolated dc-dc converter is proposed to realize the bidirectional and buck/boost voltage conversion and accordingly extend the operating range. The basic modulation is proposed and the operation principle is analyzed in detail. Furthermore, the voltage conversion ratio as the functions of the duty cycle ratio of the buck unit and shoot through ratio of the H-bridge converter is derived. The control rule of the two controllable variables is determined based on minimizing the average inductor current. In addition, the optimal starting moment of active period of the buck unit in the switching cycle is determined based on minimizing the inductor current ripple. The detailed experimental results verify the correctness and feasibility of the proposed topology and modulation.