A partial-variable-frequency modulation scheme for DAB converter for the all-ZVS operation in the full power range

With the wide application of dual active bridge (DAB) DC-DC converters in high-frequency scenarios, the realization of zero voltage switching (ZVS) becomes more important for efficiency improvement. However, the existing control strategy is difficult to realize all-ZVS in medium load, which results in lower efficiency. In this paper, a partial-variable-frequency modulation scheme based on medium load frequency regulation is proposed, which could realize the all-ZVS operation. Herein, a mathematical model is proposed to regulate switching frequency and a smooth transition is achieved in the medium load, by which the all-ZVS operation can be maintained. Finally, a DAB prototype has been built to verify the validity of the theoretical analysis and the all-ZVS operation is successfully achieved in the full power range.