Modeling and Dynamic Performance Analysis of Vehicle Fuel Cell System with Cathode Recirculation

Abstract:

Cathode recirculation is particularly suitable for solving the problems of water shortage and high potential of vehicle fuel cell systems under low load or idle conditions by adjusting the oxygen partial pressure and relative humidity of the stack intake. In this paper， a control-oriented nonlinear model of fuel cell system with cathode recirculation function is established. The exhaust gas circulation pump is used to introduce the cathode exhaust gas back to the outlet of the air compressor to realize intake air humidification and oxygen partial pressure regulation. The model can capture a series of dynamic responses brought about by cathode recirculation. The results show that the cathode recirculation can greatly improve the intake air humidity at a low current density. With the increase of the exhaust gas circulation ratio， the humidification dynamic response is faster. The dynamic response of the oxygen partial pressure regulation is slow， but the high potential at small electric densities can still be limited to less than 0.8 V by a reasonable cathode recirculation strategy. A 50 % idle power reduction is achieved by suppressing the voltage at small densities.

Key words:vehicle fuel cell system;cathode recirculation;control-oriented modeling;dynamic performance