35 kW isolated fuel-cell DC–DC converter design based on PWM resonant converter with hybrid switch structure

This paper presents the design of a 35 kW isolated fuel-cell DC–DC converter (FDC) with a hybrid switch structure. By utilizing a circuit structure and pulse-width modulation (PWM) method that enables the use of insulated-gate bipolar transistors (IGBTs), the price is reduced without a significant efficiency degradation even at frequencies of tens of kHz when compared to using all silicon carbide metal–oxide–semiconductor field-effect transistors (SiC-MOSFETs). The proposed converter is based on a PWM resonant converter, which has good switching characteristics and low-voltage stresses on the switching devices. However, it suffers from high cost owing to heavy current stresses. This problem can be solved using a hybrid switch structure that adopts IGBTs in the leading-leg switches. Considering the wide variations in the input and output voltages, the design of the main parameters, the selection of power semiconductors considering the switching characteristics, and the frequency selection method are presented. The feasibility of the proposed FDC design is verified using a prototype implemented with an output power of 35 kW (input voltage = 330–610 V and output voltage = 450–850 V) and a switching frequency of 40 kHz.