A Comprehensive Analysis to Achieve All Switches ZVS for Dual Active Bridge Converter Under Numerous Light-Load Conditions

The dual-active-bridge (DAB) converter is a highly suitable topology for transportation systems due to its electrical isolation, bidirectional power transfer, and simple structure. However, poor soft-switching performance will result in low efficiency performance at light-load conditions. To address this, a novel variable duty modulation (VDM) is proposed. This approach accounts for nonlinear elements like charge $Q_{\text {oss }}$ and dead time td, analyzes their effects on zero voltage switching (ZVS) range. The ZVS region for all switches under VDM is demonstrated. To ensure ZVS for all eight switches, the method for adjusting the magnitude and direction of the inductor current at various switching moments is also clearly explained. Finally, experimental results confirm the proposed method's validity and practicality.