Abstract
Air flow control is one of the most important control methods for maintaining the stability and reliability of a fuel cell system, which can avoid oxygen starvation or oxygen saturation. The oxygen excess ratio (OER) is often used to indicate the air flow condition. Based on a fuel cell system model for vehicles, OER performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature. In order to ensure the system working in optimal OER, a control scheme that includes an optimal OER regulator and a fuzzy control was proposed. According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and then the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor. Simulation results show that the control method has good dynamic and static characteristics.
Highlights
A fuel cell, which converts chemical energy of a fuel directly to electricity continuously with a electrochemical reaction is considered as a clean and efficient power source
Based on a fuel cell system model for vehicles, oxygen excess ratio (OER) performance was analyzed for different stack currents and temperatures in this paper, and the results show that the optimal OER was affected weakly by the stack temperature
According to the stack current, a reference value of air flow rate was obtained with the optimal OER regulator and the air compressor motor voltage was controlled with the fuzzy controller to adjust the air flow rate provided by the air compressor
Summary
A fuel cell, which converts chemical energy of a fuel directly to electricity continuously with a electrochemical reaction is considered as a clean and efficient power source. A higher OER will lower the concentration difference in cathode flow field and improve the fuel cell performance, while greater air flow results in higher power consumption for the air compressor and lower system efficiency, which is called ‘‘oxygen saturation.’’ In addition, the air pressure in cathode flow field of the fuel cell stack and the pressure difference between both sides of proton exchange membrane must be maintained in a certain range during operation. Based on Pukrushpan’s model, Chang et al [7] analyzed the variation of a fuel cell system’s net power with different stack temperatures and membrane water contents, and discovered that the optimal value of OER changes with different system parameters.
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