Experimental Verification of a Double-Input Soft-Switched DC–DC Converter for Fuel Cell Electric Vehicle With Hybrid Energy Storage System

In the drivetrain of a fuel cell (FC)-powered electric vehicle, double-input converter plays a critical role by transferring the power from battery and FC to an ultracapacitor (UC) during acceleration and from UC to the battery during braking. As the battery and FC have unregulated low voltage, the converter should provide a high-voltage gain as well as an efficient power conversion. In this article, a double-input three-level converter composed of buck-boost-half-bridge modules is proposed for automotive applications. The proposed converter can supply the load in the absence of FC or battery. The converter takes advantage of active clamp configuration in terms of reducing the voltage stress across switches and providing soft-switching performance. Consequently, the converter's overall performance in terms of switching losses and cost can be considerably improved. The switching scheme doubles the effective switching frequency, which, in turn, reduces the size of the boost inductors to enhance power density. The operational characteristics of the converter and comparison with state-of-the-art converters are given in this article. Finally, a 4-kW, 100-kHz prototype using gallium nitride switches is implemented to validate the proposed concept.