Enhanced ZVS capable Dual Active Bridge Converter for Electric Vehicle Charging Application

Abstract

A dual active bridge poses as a prominent solution for bidirectional DC-DC power conversion in high gain high power region. However, it loses its full ZVS capability when the voltage gain shifts from unity and at low power operation. This drawback can be mitigated with the use of advanced modulation strategies with multiple degrees of freedom. The advanced modulation strategies involve computational complexity and circuit parameter dependency. Furthermore, maintaining unity voltage gain using a tap changer transformer is not enough for achieving ZVS operation under light load condition due to a minimum current required for charging the parasitic capacitance and/or snubber capacitance across the switches. Circuit modifications over conventional DAB are implemented in this paper to improve the ZVS range of the converter with the simplest modulation technique for battery charging application. This converter utilizes two auxiliary inductors providing multiple ZVS regions depending on the connection. The inductors are connected to the bridges using four-quadrant switches, which facilitates on-line transition from one configuration to another, avoiding any voltage spike. The two step mode transition process introduced in the paper enables soft transition between modes of operation. Simulation is conducted on the MATLAB/Simulink environment, supporting the working principle of the converter.