Research On Modeling And Control Strategy For Air Supply System Of Vehicle Proton Exchange Membrane Fuel Cell

Recently,due to the increasing energy shortage and environmental pollution,the new energy vehicle industry has developed rapidly,in which Proton Exchange Membrane Fuel Cell（PEMFC）vehicles have become an important development direction for new energy vehicles by virtue of their longer driving range,shorter refueling time and better low-temperature performance.Under complex urban road conditions,various uncertain environmental factors and frequent acceleration and deceleration require the fuel cell system to meet the power demand stably and quickly,so control strategies need to be developedto control the PEMFC subsystem.As one of the most important subsystems of PEMFC,the air supply system is responsible for providing sufficient and appropriate amout of oxygen to the fuel cell stack,and its control performance directly determines the output performance and dynamic characteristics of the fuel cell system.Improper control of the air supply system will lead to oxygen starvation or excessive parasitic power,which can degrade the system performance and affect the fuel cell life in severe cases.Therefore,it’s important to study the operating characteristics of the air supply system and formulate suitable control strategies to provide the air flow and pressure of cathode required by the stack accurately and rapidly which is essential to ensure the stability,safety and reliability of the fuel cell system and improve the dynamic and output characteristics of the system.In this paper,relying on "Development of Key Technology for Fuel Cell Engine Integration and Control",a major scientific and technological project for intelligent manufacturing of Jilin Science and technology development plan,the model of vehicle proton exchange membrane fuel cell system is established and the working characteristics of the system are studied.Based on this,a flow Fuzzy-PID control strategy for air supply system is developed,and a genetic auto disturbance rejection control strategy is designed for decoupling the air flow and pressure of cathode cooperatively.The research results show that the control strategies designed in this paper have good control effect.Under the strategy,the fuel cell system can maintain high robustness and reliability on the basis of meeting the load condition demand.The specific research contents of this paper are as follows:1.Establishment and verification of fuel cell system model.According to the basic structure and working principle of PEMFC system,a mathematical model of fuel cell stack and air supply system is established in MATLAB/Simulink by semi-empirical method combining physical mechanism and empirical formula.2.Analysis of the factors influencing the output characteristics and dynamic response characteristics of fuel cell system.MAP of Compressor Flow-Rotational Speed-Pressure Ratio and throttle outlet flow formula are plotted by fitting the air compressor test data and throttle simulation data respectively;On this basis,the influence of compressor voltage and back pressure valve on the output performance of fuel cell is obtained through the dynamic analysis of both.And the effect of different Oxygen Excess Ratio and cathode pressure on the dynamic response characteristics of PEMFC stack is studied.3.Design of flow control strategy for PEMFC air supply system.In order to improve the dynamic performance and output performance of the system,the air flow PID control strategy is designed based on the simplified control-oriented model,with the best peroxide ratio that maximizes the net power as the control objective,and the influence of different control parameters on the control effect is analyzed;In order to obtain better control effect,the fuzzy controller is used to optimize the PID parameters in real time.The comparison control results before and after optimization show that under the control of fuzzy PID,the air supply system has faster response speed,smaller overshoot and better steady-state characteristics,can supply oxygen to the stack quickly and stably,and improve the service life of fuel cell engine.4.Development of flow and pressure collaborative control strategy for air supply system.The coupling between cathode air flow and pressure of fuel cell is studied,and the features of different decoupling controllers are analyzed;A TITO decoupling controller based on Active Disturbance Rejection Control strategy（ADRC）is designed for PEMFC air supply system,which can estimate the internal coupling and external disturbance of the system in real time and eliminate them by using the design of feedback control law.The simulation results show that ADRC controller has good decoupling effect and tracking effect;Aiming at the problem of many parameters unsetted of the controller,Genetic Algorithm is used to optimize the parameters.The comparative analysis of the input and output results of the controlled system before and after optimization shows that the GA-ADRC has better decoupling effect,antiinterference performance and output performance.