A 300 kHz, 63 kW/L ZVT DC-DC Converter for 800-V Fuel Cell Electric Vehicles

In this article, one of the very first 800-V fuel cell DC-DC converter (FDC) is developed for the next-generation fuel cell electric vehicles. The higher boost gain ratio and switching loss associated with increasing dc-link voltage, along with gradually increasing power density and efficiency demanded in the next-generation EV power converters, make the conventional boost converter not suitable for 800-V FDC. This article proposes a new design approach in which a zero voltage transition (ZVT) high step-up dual floating output boost converter (DFOBC) is introduced. Due to higher voltage gain, the operating duty cycle of DFOBC is reduced and lies in the vicinity of D = 0.5, which reduces filter size. The ZVT cells greatly reduce switching losses at 300 kHz, which enables using only a single discrete SiC mosfet for the main switch of 25-kW module, contributing to volume and cost reduction. Moreover, the proposed converter successfully demonstrates the possibility of using planar core and printed circuit board (PCB) windings at 100-kW power level, which is rarely seen in previous works. Finally, a 25-kW prototype of the proposed ZVT DFOBC is built and test. The power density of 63 kW/L excluding heatsink is achieved. The peak and full-load efficiency are measured to be 99.0% and 97.7%, respectively.