基于阴极再循环的燃料电池系统建模与动态性能分析

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

摘要:

阴极再循环通过调节电堆进气中的氧分压和水蒸气分压特别适合解决车用燃料电池系统在低怠速工况下的缺水和高电势问题。建立了一个带阴极再循环功能的燃料电池非线性系统控制模型，使用阴极再循环泵将阴极出口的气体引回到空压机出口实现了进气加湿和氧分压调节。该模型可捕捉由阴极再循环带来的一系列动态响应。结果表明，阴极再循环可以极大地改善小电流密度下的进气湿度，随着阴极再循环比的增加，加湿动态响应加快；氧分压调节的动态响应较慢，但通过合理的阴极再循环策略仍能将小电流密度下的高电势限制在0.8 V以下。通过抑制小电流密度下的电压，实现了50%的怠速功率降幅。

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.