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

Abstract

This paper presents dynamic analysis and control of an isolated dual-active-bridge (DAB) dc-dc converter. Conventional control methods for 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 converter to produce a square-wave voltage with a 50% duty ratio. In contrast, the proposed method independently controls the diagonal switches to modify the duty ratios in transient states. The theoretical analysis derives the requirements of the switching angles for eliminating dc offsets in both inductor and magnetizing currents with a settling time as short as half a switching period. The results of experiments using a 5-kW, 20-kHz experimental system verify the validity of the proposed control method.