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

Abstract

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 ϕ 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 1.6 kW 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.