Topology-Level Power Decoupling Three-Port Isolated Current-Fed Resonant DC-DC Converter

In order to solve the problems of existing three-port isolated dc-dc converter such as power decoupling and the non-zero instantaneous power of the standby port, a three-port isolated bidirectional current-fed series-resonant dc-dc converter is proposed in this paper. The operational principle and general transfer power expressions of various ports are analyzed with the duty-cycle plus phase-shift control. Then, the power decoupling at the topology level is realized by setting the switching frequency equal to the resonant frequency of the resonant tank on the high-voltage side, thus the transferred power of the two ports on the low-voltage sides can be controlled independently. Moreover, it is proved that the proposed converter realizes the zero instantaneous power of the standby port. On this basis, an optimized modulation strategy by taking the minimum root mean square value of the resonant current as the objective function is presented. The exact relationship between the desired transfer power and various phase shift is accordingly obtained. The detailed experimental results verify the correctness of the proposed converter and corresponding modulation strategy.