Research On Modeling And Control Of Hydrogen Supply System For Vehicle Fuel Cell

Proton Exchange Membrane Fuel Cell(PEMFC)is very suitable for vehicles due to its high efficiency,high power density and zero emissions,and the supply of hydrogen is essential for the normal operation of the system.A reasonable hydrogen supply system should not only meet the pressure and flow required during the operation of the fuel cell system,but also the structure of the system should not be too complicated and the cost should be as low as possible.The ejector has the advantages of low cost and high reliability.This article mainly studies the modeling and control of the vehicle fuel cell hydrogen supply system based on the ejector,and also focuses on the modeling and optimal design of the vehicle fuel cell ejector.This article first introduces the classification of fuel cells and compares the basic characteristics of several common fuel cells,and explains the reasons why PEMFC is often used in automobiles and how it works.The advantages and disadvantages of the three common fuel cell hydrogen supply system modes for vehicles and the technical difficulties that need to be overcome are summarized.For the fuel cell hydrogen supply system model based on the ejector,the application of the ejector in the vehicle fuel cell system needs to be solved first.In this paper,by fitting the experimental data of 40 kw PEMFC anode pressure drop,the relationship between anode pressure drop and current is obtained.The numerical model of the threedimensional ejector of the anode hydrogen circulation system was established by computational fluid dynamics(CFD)method,and the model was verified with experimental data.Finally,the anode pressure drop expression obtained by the fitting is applied to the simulation optimization of the model,and the performance of the ejector under the conditions of medium and low load and high load is measured,and the optimal values of the nozzle throat diameter,mixing chamber diameter,mixing chamber length,and the distance between the nozzle outlet and the mixing chamber inlet are determined.Then,a hydrogen supply system model based on ejector was established,including three manifolds(ejector manifold,supply manifold,and return manifold),ejector,flow control valve,purge valve,and fuel cell anode model.The fuel cell anode model reflects the dynamic changes of hydrogen pressure and water activity in the gas flow channel,gas diffusion layer,and catalyst layer.In MATLAB/Simulink,a fuel cell anode hydrogen supply system model based on ejector was built according to the flow relationship of each component of the system.Finally,the established system model is analyzed and linearized.The observer-based state feedback controller is designed and compared with the proportional integral controller and the static feedforward controller.The simulation results show that the observer-based state feedback controller has the best dynamic response and smaller overshoot.In addition,the designed purge control method enables the liquid water accumulated in the return manifold to be quickly discharged.