Dynamic Control and Performance of an Isolated Dual-Active-Bridge DC-DC Converter

This paper presents dynamic analysis and control of an isolated dual-active-bridge (DAB) dc-dc converter. Conventional control methods of the DAB converter may cause dc offsets in both inductor current and transformer magnetizing current in transient states. The dc offset in the inductor current introduces an excessive peak current through the switching devices. The dc offset in the magnetizing current cannot be neglected and may induce magnetic flux saturation. Conventional phase-shift control methods simultaneously turn on and off the diagonal switches in each H-bridge to produce a square-wave voltage. On the other hand, the proposed method independently controls diagonal switches to generate short zero-voltage periods in a transient state. The theoretical analysis derives the requirements of the switching angles, which enable both inductor and magnetizing currents to be settled within a half switching period without any dc offset. A 5-kW experimental system verifies the validity of the proposed control method.