Asymmetrical Modulation of DAB Converters for Voltage Gains Higher than Unity

In this paper, the authors extend the continuous closed-form asymmetrical modulation for the Dual Active Bridge (DAB), previously proposed by them, to accommodate voltage gains greater than unity. This extension enables the converter to operate within an extended voltage range. Modulation schemes for voltage gains greater than unity are proposed, and closed-form equations are derived. Similar to the case of voltage gains lower than unity, an extended Zero Voltage Switching (ZVS) range is achieved for voltage gains higher than unity, resulting in higher efficiency compared to existing literature. The improvement in efficiency is experimentally verified using a DAB converter with a rated power of 5000W. Additionally, seamless transitions between the proposed modulation schemes are illustrated.