Dynamic Modeling And Performance Simulation Analysis Of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell is one of key components of hydrogen fuel cell vehicles,and its cost and lifetime are two main factors that restrict the large-scale commercialization of hydrogen fuel cell vehicles.Then both the start & stop cycling and load change cycling are two important conditions affecting its lifetime.Therefore,it is of great significance to study the dynamic response and performance of the fuel cell under two conditions.In this paper,the dynamic performance of fuel cell is analyzed by simulation based on the established mode.Firstly,based on the equivalent circuit model,and considering both the dynamic gas pressure model and the dynamic heat transfer model,a lumped parameter model is developed.The start and stop process of the fuel cell is simulated in SIMULINK software.The undershoot and overshoot of the voltage are observed from the simulation results,the response time of the voltage is basically the same as that of the fuel cell temperature,which indicates that the temperature has great influence on the dynamic performance of the fuel cell.From the perspective of the temperature,the dynamic response of the thermodynamic potential,the activation overvoltage,the ohm overvoltage and the concentration overvoltage of the fuel cell is analyzed.It is found that the overshoot of the activation overvoltage and the ohm overvoltage causes the voltage undershoot,and the voltage overshoot is caused by the undershoot of the activation overvoltage.When the temperature is input in the form of a step signal,the output voltage response of the fuel cell is fast and undershoot and overshoot do not occurs.So it indicates that it can improve the dynamic performance of the fuel cell with the increasing of temperature response speed.Secondly,a distributed-parameter model was developed,based on the basic conservation equations,the electrochemical reaction equation and the water transport model in the proton exchange membrane,the load change process of the fuel cell is simulated by changing the current density with the transient solver in Fluent,the dynamic response of the voltage is analyzed especially.Different from the start and stop process,the model assumes that the temperature remains constant during the load change process.The influence of operating parameters,such as gas stoichiometry,gas pressure and gas humidity,and loading parameters,such as loading amplitude,loading speed(implemented by UDF programming)and loading initial current density on the dynamicperformance of proton exchange membrane fuel cell in the load change process was studied.The simulation results show that the larger gas stoichiometry,the higher gas pressure and the higher gas humidity have a positive influence on improving the dynamic performance of the fuel cell,the degree of gas humidity is greatest;When anode saturated humidification,cathode semi-saturated humidification,it is obvious that small loading amplitude and the loading speed can improve the dynamic performance of the fuel cell.When the loading amplitude is the same,the bigger loading initial current density corresponds to the better dynamic performance of the fuel cell,based on this phenomenon,a loading method of variable loading speed is proposed,the dynamic performance under the loading method is better than that of the fixed loading speed.In this article,the lumped parameter and the distributed parameter model are used to study the dynamic response of fuel cell,the simulation results have some guiding effect on improving the dynamic performance of proton exchange membrane fuel cell under start & stop and load change conditions.