Research On Modeling And Control Strategy Of Hydrogen Fuel Cell System

With the rapid and continuous development of various industries in today's society,the problem of environmental pollution arises at the same time as energy consumption.Improving energy efficiency and solving environmental pollution problems are imminent.Proton Exchange Membrane Fuel Cell(PEMFC)is an outstanding representative in the field of hydrogen energy.With its advantages of high efficiency,high energy density,low operating temperature,low noise and low emissions,it has been favored by all countries in the world.Based on its unique advantages,proton exchange membrane fuel cells are suitable for hybrid electric vehicles and portable mobile power sources.Hydrogen fuel cells currently have some disadvantages.Such as being susceptible to changes in the external environment and operating conditions,unstable voltage output,large hysteresis,and fuel safety issues.These problems have seriously hindered the commercial application of fuel cells.Therefore,in this paper,the following research is carried out for the modeling and control of hydrogen fuel cells.(1)Build a hydrogen fuel cell test platform.According to the relevant data of the proton exchange membrane fuel cell stack provided by the manufacturer,the corresponding operating parameters of each subsystem of the fuel cell are calculated.Completed the design,selection and construction of each subsystem of the test platform for the low-temperature water-cooled hydrogen fuel cell.Among them,the overall design plan of the hydrogen fuel cell includes the design plan of the hydrogen supply subsystem,the design plan of the air supply subsystem,the design plan of the cooling and humidification subsystem,and the design plan of the data acquisition system.(2)A hydrogen fuel cell system model was established based on MATLAB /SIMULINK.According to the actual situation of the stack,a semi-empirical model of output voltage and output power is established.According to the working principle of fuel cell system,the mechanism model of fuel cell air supply system and hydrogen supply system is established.A partial pressure model of hydrogen,oxygen and water vapor in a hydrogen fuel cell is obtained.And verify the correctness of the model based on the test data.(3)Simulation analysis of hydrogen fuel cell system model based on MATLAB /SIMULINK.According to the built hydrogen fuel cell system model,the key parameterssuch as the operating pressure of the stack operation,the temperature of the stack,the working pressure difference between the anode and cathode,and the excess oxygen ratio are simulated and analyzed.Obtain the relationship between output voltage and output power with load current under different working conditions.The simulation results show that the increase of the working pressure,temperature and pressure difference of the stack has a positive effect on the output performance of the stack.The proper increase of the oxygen excess ratio can improve the output performance of the stack.When the oxygen excess ratio is too large,it will reduce the net power of the hydrogen fuel cell system.This provides a reference for the simulation study of the control strategy in the subsequent chapters.(4)Simulation study on control strategy of hydrogen fuel cell system based on MATLAB / SIMULINK.The excess oxygen ratio plays an important role in the operation of the fuel cell.In order to ensure the safe and efficient operation of the fuel cell,it is necessary to ensure that the phenomenon of oxygen deprivation does not occur during the operation of the fuel cell.The oxygen excess ratio needs to be maintained at an appropriate value to ensure the maximum net power of the system.According to the relationship between current density,oxygen excess ratio and net power in the simulation study,the optimal oxygen excess ratio of the system under different working conditions was determined.Through incremental PID and fuzzy control to adjust the size of the air intake flow.The simulation results show that the control effect of the incremental PID control is better than the fuzzy control under static conditions,and the control effect under dynamic conditions is not as good as the fuzzy control.At the same time,in order to ensure the safe and efficient operation of the fuel cell to the greatest extent,the PID control is used to adjust the size of the hydrogen gas inlet flow,and the working pressure difference between the anode and cathode sides works at the target set value.The simulation results show that PID control can accomplish the control goal ideally.