Towards Full Range Zero-Voltage Switching of DAB Converters: An Improved Multi-Mode Modulation at Light Loads Under Close-to-Unity Voltage Ratio

The soft switching characteristics of zero-voltage-switching (ZVS) are of great significance for reducing the switching loss and improving the efficiency of the converter. However, affected by non-ideal factors, the dual active bridge (DAB) converter using the three-phase-shift modulation method has an inherent non-ZVS region. This letter proposes a novel operating mode to fill the non-ZVS area with ZVS operation where the input and output voltage are close to match with. What's more, combined with the existing mixed-mode modulation method and dynamic-process modulation method, the ZVS operation of DAB in full voltage gain range and full power range under all working conditions can be realized.