ABOUT THE SYSTEM DESIGN OF A FUEL-CELL/SUPERCAP HYBRID POWERTRAIN

This contribution is based on previous work of the authors and emphasizes the dynamical behavior and design of a fuel-cell driven hybrid powertrain for small vehicles. From a given load profile, a brief discussion will be presented on how to size the fuel-cells and SuperCaps in stationary consideration. The dynamics of the load profile, however put requirements on the system components and affect strongly their life time, in particular the fuel-cells. Especially, the load profile used here which is bused on a measured profile from an industrial fork-lift, is very dynamic with large and fast power peaks. Using a Hardware-in-the-Loop test rig of the whole system, two different topologies are used to investigate which one is best suited for a defined industrial application. Further on, conventional led-batteries and SuperCaps with equivalent weight and volume are compared as the energy storage of the system. Finally, a power management to avoid fast transients from the fuel-cells in order to mitigate a fast deterioration is implemented It will be shown that SuperCaps with the so called Range Extender topology are best suited and an adaptive controller for the output voltage of the DC/DC-converter is used to prevent fast dynamics in order to increase their lifetime.