Dynamic modeling of a hybrid energy source combined of PEM fuel cell and ultracapacitor

Fuel cell power plants are electrochemical devices that convert the chemical energy of a reaction directly into the electrical energy. Among the various nextgeneration power plants, FCs, especially the proton exchange membrane fuel cells (PEMFCs), are considered to be one of the promising energy sources due to high efficiency and are environment friendly [١]. However, for stationary and vehicular applications, a FC power plant may not be sufficient to satisfy the load demands, especially during peak demand periods or transient events. By operating the FC and in parallel, both steady state and peak power demands can be satisfied. Without the ultracapacitor (UC) bank, the FC power plant would have to supply all power demand, thus increasing the size and cost of the FC power plant. The UC bank is used to provide the difference between the load demand and the output power generated by the FC power plant.