Modeling Of Output Characteristics And Operating Conditions Analysis Of Proton Exchange Membrane Fuel Cell System Based On Low Hydrogen Pressure

Proton exchange membrane fuel cell(PEMFC)is a device based on the electrochemical reaction of hydrogen and oxygen to generate electricity,it is a complex system composed of a variety of different components,including anode,cathode,proton exchange membrane,electrolyte,catalyst layer,and manifold plate.The characteristics of a PEMFC may be influenced by many factors such as material properties,geometric design,operating conditions and control strategies.The interactions between components and subsystems affect the performance,durability and lifetime of the PEMFC system.In order to design a PEMFC with high performance,long life and high durability,it is necessary to have a comprehensive understanding of the coupling effects of different factors on the overall performance and durability of the PEMFC.In this paper,we built a fuel cell system model based on the low hydrogen pressure output characteristics model,and verified the accuracy and reliability of the model by deriving the optimal operating conditions through simulation analysis.(1)The performance of fuel cell under low hydrogen pressure is the target we need to explore.In this paper,we deeply studied the mechanism of PEMFC electrochemical reaction and the change mechanism of polarization loss.First,the output characteristics model of conventional hydrogen pressure PEMFC was established.On this basis,we used Simulink/Thermolib software to build the PEMFC output characteristics model that can simulate the low hydrogen pressure at the inlet of the reactor,and comprehensively analyzed the change of output voltage,power and efficiency with the load current.The simulation results show that the performance of low hydrogen pressure fuel cell is maintained at a great level at low current density,but the output voltage decays rapidly with the increase of electric density,indicating that there is still a gap in performance compared with conventional hydrogen pressure,which need to be improved and optimized.The effect of temperature and hydrogen pressure on the output performance was also studied.The model can effectively simulate the actual operation of fuel cell under steady-state,dynamic and variable operating conditions.(2)In order to improve the efficiency and lifetime of fuel cells,the design of thermal management systems is also crucial.After modeling and simulating of the fuel cell thermal management system,a temperature control strategy based on PID control of cooling fan speed was designed.The experimental results show that the control strategy can effectively control the temperature difference between inlet and outlet of the cooling water within 4°C while maintaining the optimal operating temperature range of the reactor.In addition,the strategy can avoid frequent step changes,thus reducing the damage to life of the fan and pump.Therefore,the strategy has the feasibility and superiority of practical application.(3)On this basis,the simulation model of the proton exchange membrane fuel cell system was carried out.Through the analysis of the influence of the key components on the gas supply,and the sensitivity analysis of the parameters such as air measurement ratio,air pressure,hydrogen pressure and reactor operating temperature,comparing the simulation results,the optimal operating conditions of the whole system were finally obtained,that is,the maximum output power of the system is 31.3k W,and the maximum efficiency is 41.1%.