Combined Pulse-Width Modulation of Dual Active Bridge DC-DC Converter to Increase the Efficiency of Bidirectional Power Transfer

A dual active bridge (DAB) dc-dc converter is suitable for bidirectional high-power transfer. However, it has a limited soft-switching range and a high peak current during low power transfer with traditional phase-shift modulation (PSM) when there is a variation in the input/output voltage. To overcome solve this difficulty, this paper proposes a new modulation strategy, combined pulse-width modulation (CPWM) which combines single pulse-width modulation (SPWM) and dual pulse-width modulation (DPWM), with a unified fundamental phase phi(f) for a wide power transfer range. Unlike previous modulation strategies, CPWM is applicable for bidirectional power transfer. In order to combine SPWM and DPWM, this study comprehensively analyzes the soft-switching range and the peak current of PSM, SPWM, and DPWM. The CPWM strategy is experimentally tested using a 1.6kW prototype to verify the improvement in efficiency and its bidirectional power transfer capability. The experimental results show efficiencies of both positive and negative power transfers were improved by using CPWM.