In this paper, a polymer-electrolyte-membrane fuel-cell (FC) model that is useful for simulation and control purposes is presented. The model uses both electrical-circuit components and functional blocks to reproduce both static and dynamic FC behaviors. Its main feature is in the reproduction of the oxygen-excess-ratio behavior, but it is also able to interact with any electrical device connected at the FC terminals, e.g., a load or a switching converter. Consequently, the proposed model can be used to develop new control strategies aimed at avoiding the oxygen-starvation effect and/or minimizing the fuel consumption. The model has been customized for a Ballard Nexa 1.2-kW power system, and this has allowed an experimental validation by means of measurements performed on a real FC device.