Fuel cell powered UPS systems: design considerations

In this paper a 1 kVA fuel cell powered line-interactive UPS system employing modular (fuel cell and power converter) blocks is introduced. Two commercially available PEMFC (25-39 V, 500 W) modules along with suitable DC/DC and DC/AC power electronic converter modules are employed. A supercapacitor module is also employed to compensate for the instantaneous power fluctuations and overcome the slow dynamics of the fuel processor such as reformers. Further energy stored in the supercapacitor is also utilized to handle a momentary overload such as 200% for a short duration. Due to the absence of batteries, the system satisfies the demand for an environmentally friendly clean source of energy. A complete design example illustrating the amount of hydrogen storage required for 1 hr power outage, and sizing of supercapacitors for transient load demand is presented for a 1 kVA UPS. Simulation and experimental results show the validity and feasibility of the 1 kVA fuel cell power plant.