A Three-Level Dual-Active-Bridge Converter with Blocking Capacitors for Bidirectional Electric Vehicle Charger

In order to solve the considerable issues of air pollution, climate warming and fossil energy shortage, many governments around the world have formulated policies to encourage the development of electric vehicles over the past decade. This paper proposes a three-level dual-active-bridge (DAB) converter with blocking capacitors for bidirectional electric vehicle charger. In the proposed three-level DAB converter, two blocking capacitors are placed in series with the two windings of the transformer, respectively. Both of the two three-level bridges can operate in four modes, and generate square waves with four kinds of amplitude. Therefore, the proposed three-level DAB converter can adapt to the wide voltage range of electric vehicle. A working mode selection algorithm is developed to minimize the transformer RMS current of the three-level DAB converter. The optimal working mode can be selected in real time according to the voltage ratio and the active power. Finally, experimental results are presented to verify the feasibility and the advantage of the proposed three-level DAB converter.