This study presents a IEEE standard Very High Speed Integrated Circuit Hardware Description Language-Analog and Mixed-Signal Extension (VHDL-AMS) modelling of a complex multi-domain energy conversion system: a fuel cell stack. A comparative study between the different modelling approaches (bond graphs, electrical equivalent circuits) is given to show the great advantages of the VHDL-AMS language in the design process of fuel cell systems. The modelling approach allows the design team to split the work into several parts (concurrent engineering) and validate each part independently. The fuel cell stack model fits the experimental results. It is able to predict the voltage and the power of the fuel cell with a good accuracy taking into account the water content of the membrane. This last point is really important to design the air supply system (compressor and humidifier) and its associated control. (C) 2007 Elsevier B.V. All rights reserved.