Abstract: In order to deal with the problem of instability in the air mass flow control at high load, the air system of a low-pressure fuel cell system is studied in details. Based on the analysis of the system architecture, the dynamic model of the air system is developed, in which a semi-empirical model of blower is built and the impact of parasitic power of the blower on the net power of the fuel cell system is taken into consideration. The accuracy of the model is verified by comparing the simulation results with the experimental data. Then the reason for instability is studied by using both model simulation and theoretical analysis which employs the automatic control theory based on the linearized system model. The analysis result shows that the feedback loop of the blower current is the cause of instability. Furthermore, a new control algorithm is designed. The new control algorithm opens the current loop and adapts to the optimized control parameters. The test results show that the air mass flow rate is stable and the improved system has a good performance.

Key words: Air system, Control, Fuel cell system, Modeling, Vibration