Abstract
The performance and efficiency of the fuel cell stack is impacted by the management of air subsystem, which also prevents it from degrading due to oxygen starvation and pressure fluctuations. For complex onboard conditions, a cooperative control strategy for air mass flow and pressure of the air subsystem based on bypass valve is proposed in this paper. Firstly, a 120 -kW vehicular fuel cell air subsystems bench was constructed and its mathematical model is established based on experimental data. Secondly, a novel control strategy for correcting the target air flow rate based on oxygen excess ratio feedback is proposed, where to meet the air flow requirements for actual vehicle environment of the stack. Furthermore, the transfer function model of the air subsystem is fitted according to the experimental data. Inverted decoupling combined with active disturbance rejection control is adopted to independently manage the air mass flow and pressure, where the external disturbance and model uncertainty are evaluated and recompensed. Then, a fuzzy control strategy based on the bypass valve is proposed to suppress the pressure fluctuations and overshoot during load variation. Simulation and experimental studies show that the proposed cascade decoupling control framework can quickly track the target value of the oxygen excess ratio within 1.2 s, optimize the stack net power, and increase it by up to 3%. The effectiveness and robustness of the decoupling control for air mass flow and pressure has been confirmed. The proposed fuzzy control strategies that utilize bypass valves can suppress pressure fluctuations and reduce the coupling effects for the air supply systems. It contributes to optimizing the dynamic performance of fuel cell systems and extending its service life.
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