Simulation And Control Of Proton Exchange Membrane Fuel Cell System

Proton exchange membrane fuel cell system is the energy source of fuel cell vehicle,the performance and life of PEMFC system are important factors influencing the development of fuel cell vehicles.Modeling and simulation of PEMFC system is an important means to study it,and scientific and effective control is an important method to improve its life and performance.In this paper,the PEMFC system is modeled,simulated and controlled.Firstly,the cathode gas supply system,anode gas supply system,thermal management system and fuel cell reactor were analyzed and modeled.Then the model is simulated with corresponding working characteristics,and finally the control methods of air supply system and thermal management system are determined according to the simulation results and verified to be scientific and effective.The main research work is as follows:(1)The models of PEMFC cathode gas supply system,anode gas supply system and thermal management system were analyzed and established.According to the theoretical formula,a PEMFC voltage model was established to simulate the effects of temperature and pressure on its output voltage,activation voltage loss,ohmic voltage loss and concentration voltage loss.The cathode channel and anode channel models,the proton exchange membrane humidity model and the reactor temperature change model were established to lay a foundation for the simulation.(2)The influence of air compressor speed on cathode inlet flow and inlet pressure and the influence of intercooler coolant flow on air cooling effect were simulated.The constant pressure control of the pressure reducing valve of the anode gas supply system,the influence of the opening of the pressure reducing valve on the hydrogen flow,and the changes of the inlet and outlet gas flow of the anode and hydrogen consumption flow under the change of the current were simulated.The influence of cathode inlet pressure on output voltage,output power and net output power of the reactor under constant current and variable current conditions is simulated.The cooling effect of different flow rate cooling liquid under the current change of thermal management system,the cooling liquid flow following the current change cooling effect,the temperature change of proton exchange membrane humidity change,the reactor output voltage change were simulated.(3)According to the simulation results,the high temperature of the reactor will cause water loss of the proton exchange membrane,while the low temperature is not co nducive to the performance of the reactor.Therefore,it is necessary to control the reactortemperature within a reasonable range.The fuzzy PID controller is designed to control the coolant flow by taking the difference between the reactor temperature and the target temper-ature and the change rate of the difference as the input and the pump voltage as the output to keep the reactor temperature between 66? and 70?.Through simulation,when the current changes to 15 A,the fluctuation of the reactor temperature at the target temperature of 68? is less than 1.6?,which can be maintained in the ideal range.(4)According to the simulation results,it is found that there is air supply capacity of air compressor in a certain current to make the net output power of the electric reactor the best,and the air supply capacity of air compressor with the best net output power is different under different current.The control target is the over-oxygen ratio under the optimal net output power generated by the air compressor under different electric currents.The predictive control method is adopted to control the optimal over-oxygen ratio of the air compressor under different electric currents.Through simulation,the air supply of the air compressor can follow the optimal oxygen ratio change under the current change,which can ensure the air supply and reduce the power consumption of the air compressor at the same time,which is beneficial to improve the net power output of the system.