This article describes the design and testing of a 400 V - 8 kW - 100 kHz isolated dual active bridge (DAB) dc-dc converter using four 1200 V/40 A SiC MOSFET modules. The converter is operated under hard-switching conditions by using single phase shift (SPS), extended phase shift (EPS) and dual phase shift (DPS) controls. The phase-shift angles between two DABs are optimized in order to achieve the minimized circulating current by the transformer. By varying the phase-shift angles of secondary side switching devices, the overall performance of dual active bridge dc-dc converter is analyzed. The conversion efficiencies are measured between dc input and output terminals of DAB for conventional and phase-shift PWM controls. The different operating modes and design system parameters are illustrated. The efficiency of the converter is validated by experimental results on 8 kW laboratory prototype.

Keywords: Dual active bridge (DAB) converter, Isolated dc-dc converter, SiC MOSFET, Phase-shift control, Zero voltage switching (ZVS)