Modeling, design, and control of a fuel cell/battery/ultra-capacitor electric vehicle energy storage system

Within three types of energy storage, fuel cell is chosen as main energy source and battery and ultra-capacitor as power source. The slow dynamics of fuel cell will be compensated with a combination of battery and ultra-capacitor. Use of ultra-capacitor has several benefits. First longer life span of ultra-capacitor will reduce the maintenance or replacement cost of battery pack. Secondly, higher charging rate of ultra-capacitor makes regenerative braking efficient and simpler. With proper control of fuel cell boost converter, battery is directly connected to DC bus, which can improve overall efficiency. Hybrid topology will be discussed and method for charging and discharging battery and ultra-capacitor will be studied in this paper.