Research On Modeling And Control Of Hydrogen Fuel Cell Engine Intake System

Proton exchange membrane fuel cell(PEMFC)can convert the chemical energy between oxygen and hydrogen molecules into electric energy through chemical reaction.With the advantages of green and high efficiency,PEMFC is becoming one of the main development directions of new energy vehicles.Hydrogen fuel cell system is a complex system affected by multi-variables and multi-parameters.In order to make the subsystems work together,it is necessary to carry out in-depth research on each subsystem.The increase of hydrogen and air supply can improve the output characteristics of PEMFC,but too much supply will damage the balance between anode and cathode,even excessive pressure difference will lead to membrane rupture,seriously affect the normal operation of the PEMFC.And in the actual operation process of PEMFC,under the condition of changing load,need not only guarantee the stability of pile of internal pressure,moreover,the rapid response of feed pressure and flow rate should be satisfied in the process.Therefore,it is of great significance to research the control strategy of PEMFC intake system.First of all,based on the design parameters of the stack,a simulation model of the output characteristics of the PEMFC was established in MATLAB/Simulink.,through analyzing the influence of the partial pressure,temperature and current on the voltage activation loss,ohmic loss and concentration loss,the characteristic curve of the output voltage of the stack is obtained.The results show that increasing the partial pressure and temperature of the gas will increase the output voltage and power of the stack,but too much pressure will increase the parasitic power of the system,and too much temperature will decrease the performance of the stack,so it is necessary to improve the performance of the system by increasing the gas pressure and temperature within a reasonable range.Secondly,based on the basic structure of the fuel cell intake system,the air supply system model and the hydrogen supply system model are established in Simulink by using the theories of fluid mechanics,mechanical mechanics and electrochemistry.Among them,the air supply system model includes the air compressor model based on MAP,the gas supply pipeline model,the cathode flow field model and the back pressure valve model;Hydrogen supply system models include regulating valve model,gas supply pipeline model,anode flow field model and hydrogen circulating pump model.The results of dynamic characteristics analysis of the intake system show that the change of the speed of the air compressor and the opening of the back pressure valve will affect the intake flow and pressure,which indicates that there is a coupling effect between the intake pressure and flow.Finally,the double closed-loop PID control,feed-forward PID decoupling control and fuzzy neural network decoupling control algorithm are analyzed and compared for the air supply system.Relative to the air supply,the hydrogen is provided by high-pressure hydrogen tank,and the rate of chemical reaction at the anode is many times faster than at the cathode,so the anode pressure just satisfy with the change of air pressure,through the PID control and fuzzy self-adjusting PID algorithm to control the hydrogen supply system.The results show that the system with double closed-loop PID control has fast response speed,but the coupling relationship between pressure and flow cannot be relieved,while the feed-forward PID decoupling can achieve complete decoupling effect,the feed-forward PID decoupling based on the invariance principle will make the pressure and flow not interfere with each other,but it depends on the precise mathematical model of the controlled object.While the fuzzy neural network can achieve decoupling effect without requiring accurate mathematical model,it can continuously adjust the network parameters and weight value through online learning,so that the system can obtain better performance.