DC-DC boost converter design for Kettering Universitys GEM fuel cell vehicle

This paper presents the design and performance of a low cost, fully integrated DC-DC power conversion and control system for a modified global electric motors (GEM) fuel cell hybrid vehicle. The system incorporates a custom designed DC-DC boost converter which steps up the nominal 26 V DC fuel cell stack voltage to interface with the 72 V DC vehicle battery bus at an input power level of 1.2 kW. Additionally, several embedded control functions are implemented to integrate a Ballard Nexa" fuel cell power module into the GEM vehicle. The converter and control system features a microchip PIC micro-controller programmed using embedded C code. The power converter section is designed around a custom wound toroidal inductor. Several low loss considerations were incorporated into the design to attain high efficiency conversion. Design equations supported by performance data indicates that the DC-DC power converter achieves a conversion efficiency approaching 98% for a single fuel cell power module operating at full output power (1.2 kW). Design enhancements are discussed that facilitate the operation of the converter with two parallel connected fuel cell modules (2.4 kW) at high efficiencies. The control system incorporates algorithms to perform battery charging and power ramp rate, as well as fuel cell voltage and current limiting. The control system exhibits stable performance characteristics throughout the entire vehicle load range and battery state of charge range, while tracking vehicle transient conditions