A numerical model is developed from a stationary proton exchange membrane fuel cell (PEMFC) system comprising a PEMFC, a DC-DC buck converter, an auxiliary power supply (a lithium battery and supercapacitor), and a DC-AC inverter. The transient and steady-state performance of the PEMFC system is investigated by means of Matlab/Simulink simulations. It is shown that a good agreement exists between the simulated polarization curve of the PEMFC and the experimental results presented in the literature. In addition, it is shown that the DC-DC buck converter provides an effective means of stabilizing the output voltage of the PEMFC. Finally, the results confirm the effectiveness of the auxiliary power source in enabling the PEMFC to satisfy the peak load demand. Copyright (c) 2012 John Wiley & Sons, Ltd.