Parameter estimation and control of a fuel cell air supply system based on an improved extended state observer

Tracking control of the oxygen excess ratio (OER) and keeping the cathode air pressure relatively stable are essential for the operation of polymer electrolyte membrane fuel cell (PEMFC). In automotive fuel cell air supply systems, the cathode air pressure and OER are usually unmeasurable parameters, which makes the air supply system control and fault analysis very difficult. To solve this problem, this paper proposes an extended state observer based on the hyperbolic tangent function (HTF-ESO) to estimate the cathode air pressure of the fuel cell gas supply system, and indirectly obtains the OER according to the estimated cathode pressure, and designs the sliding mode control (SMC) and a first-order active disturbance rejection control (ADRC) for the tracking control of the OER. The simulation results show that the improved HTF-ESO effectively mitigates the initial differential peak phenomenon and reduces the initial estimation error of the cathode air pressure, and the RMSE of the cathode pressure and supply manifold pressure observation errors are reduced by 68% and 20%, respectively, compared with the present unimproved ESO. Compared with the PI, the RSME of the control error after convergence of the designed SMC and ADRC is reduced by 4.3%, and the OER can be restored to the reference value within 1 second, with good dynamic response.