Wide Input Voltage Range Step-Up/Step-Down DC-DC Converter With Multiple Operating Modes for Fuel Cell Vehicles

In commercial fuel cell vehicles (FCVs) under certain operating conditions, the output voltage of the fuel cell (FC) can be higher than the dc bus voltage of the vehicle. To match the output voltage of the FC with the dc bus voltage, a dc-dc converter with high-gain step-up mode (HGSM) and step-up/ step-down mode (SUDM) is presented in this article, and has the advantages of continuous input current, wide voltage conversion range, and common ground structure. Meanwhile, the two modes of the proposed converter can meet the different voltage levels required by FCVs and also address the voltage drop caused by the exclusion of faulty FC stacks. In addition, this article proposes a hybrid switching-frequency control method based on the HGSM of the converter. The flexible frequency selection benefits the inductor design and reduces switching losses. An experimental platform containing a 400-W prototype is built, the experimental results show that the prototype can stabilize the output voltage to 400 V under two operating modes when the input voltage varies from 40 to 500 V, realizing up to ten times of voltage conversion, and the prototype maximum efficiency is to 96.2%.