A ZVS Range Enhancement Strategy for the DAB Converter by Using Blocking Capacitors

The dual-active-bridge (DAB) converter is widely used in many applications. When the port voltages are not matched, the switches of the converter are hard to realize zero-voltage switching (ZVS). By introducing different dc voltage offsets across the blocking capacitors, this article proposes a hybrid modulation technique, which makes the converter switch between different working modes to enlarge the ZVS region according to specific operating conditions. In this article, the soft switching regions of different working modes are derived mathematically, and the switching boundary of the hybrid modulation is determined graphically. Finally, the experimental results verify the validity of the proposed strategy.