Modelling, simulation and optimisation of a 2,5 kW PEM fuel cell system

Abstract

This paper presents the results of the experimental and theoretical investigations, the modelling and the simulation of a 2,5 kW PEMFC. The relationship of the three subsystems stacks, humidity and temperature control circuit is pointed out. The developed simulation models for the stack and the humidity control are described in detail. It is found, that the FSC can only operate stably and provide a high power quality, if the membrane humidity can be kept at a constant level. The original humidity controller was found to be not suited for a stable control across the whole range of operating points. Especially for partial load, the dehydration of the membrane and the fluctuating stack voltage were intolerable. These problems were addressed and solved by means of simulations and the introduction of a new control concept, a closed-loop Pl-controller combined with an open-loop model-reference control. The new control concept was implemented and tested. The FSC immediately showed the desired stabilisation and improvement of power quality. The simulation models were found to be valuable tools in the process of the controller redesign and optimization