An improved small-signal model of the dynamic behavior of PEM fuel cells

The dynamic behavior of a fuel cell is integral to the overall stability and performance of the power system formed by the fuel supply, fuel cell stack, power conditioner, and electrical load. Present-day fuel cells have transient (dynamic) responses that are much slower than the responses of the typical power conditioner and load to which they are attached. This disparity has significant implications on the overall power system design. In particular, some form of energy storage with adequate quick charge/discharge capability is usually needed to provide firm power backup during electrical load increases. This paper describes an effort to improve the small-signal modeling of a proton exchange membrane fuel cell´s dynamic behavior as an initial step toward prescribing internal design modifications and/or external controller designs to improve its transient behavior. Such improvements will allow for reduced energy storage while increasing the number of suitable storage technology options. Simulation results obtained from the proposed model are presented along with corresponding test results, which show generally good agreement with each other and indicate that this model is to be preferred to another one.