Development of a Dynamic Model and Control of a PEM Fuel Cell

摘要

This paper presents a finite difference dynamic model of a single unit PEM stack. The model applies a detailed electrochemical and thermal analysis of the fuel cell yielding internal cell profiles for any relevant thermodynamic and electrochemical cell variable. Dynamic simulations are carried out starting from a steady state condition with average current density of 5000 A/m2 with a fuel utilization of 75%, applying a ramp current change to the system. Results of the simulation show that a ±20% load current change determines significant variation of the cell key variables such as the fuel utilization and the maximum MEA temperature. Given the importance of these parameters on both cell performance and cell durability, a simple control strategy based on two PIDs is added to the system: the PID1 acts on the fuel valve opening to the maintain a constant fuel utilization factor, while the PID2 acts on the air fan rotational speed thus regulating the cathode air inlet to control the cell maximum temperature. It is shown that with an appropriate tuning of the PID parameters it is possible to maintain an effective cell operation under different load variations.