A Dynamic ZVS-Guaranteed and Seamless-Mode-Transition Modulation Scheme for the DAB Converter That Maximizes the ZVS Range and Lowers the Inductor RMS Current

The dual active bridge (DAB) converter operating with a relatively high switching frequency is well suited for deriving a high-power density electric vehicle (EV) charger. In this case, safeguarding the realization of zero voltage switching (ZVS) for a wide operating range becomes crucial to ensure a good performance in terms of efficiency and control reliability. Unfortunately, most modulation schemes available today in the literature require a detrimental compromise in the achievable ZVS range, particularly the ones working mainly toward the minimization of the current stress. Due to the fact a public EV charger will work with multiple vehicles having quite different charging profiles, i.e., with wide operational voltage and currents ratings, the ZVS operation may be prone to fail to undermine the whole cycle charging efficiency. To relieve the issues, this article proposes a new modulation scheme for the DAB converter featuring a maximized ZVS range and a quasi-optimal inductor rms current. Herein, the concept of dynamic settings of the required modulator's ZVS-current is utilized and a straightforward implementation with seamless circuit mode transition is achieved. With the above characteristics, the dynamic and static losses of the component circuits can be reduced together. By adopting the dynamic ZVS-current settings strategy, the turning-
on
currents of the DAB switches are adjusted in real-time guaranteeing the ZVS operation under various operating conditions. With the seamless transition, the inductor current can be smoothly regulated to ensure system stability. The proposed modulation scheme is introduced, analyzed, validated, and benchmarked in a 4.5 kW/100 kHz SiC-based DAB prototype, whose peak efficiency can reach 96.3% when operated at partial load.