Research On Hydrogen Fuel Cell System Modeling And Gas Supply System Control Method

Proton Exchange Membrane Fuel Cell（PEMFC）has the advantages of low noise,fast response,high efficiency and no pollution,and has been widely studied at home and abroad recently.Proton exchange membrane fuel cell is a complicated timevarying system with poor linearity,strong hysteria and strong coupling.Its output characteristics involve the knowledge of fluid mechanics,electrochemistry,thermodynamics and other fields.To improve the efficiency and prolong the working life of proton exchange membrane fuel cell,it is very important to understand its output characteristics and control its working parameters accurately.Based on theoretical analysis,this paper establishes a control-oriented fuel cell system model,studies the influence of working conditions on its output performance,and discusses the control method of gas supply system.The main research contents are as follows:（1）The fuel cell system model was established by using Matlab/ Simulink platform.The working principle of PEMFC was discussed.Based on the law of conservation of mass,conservation of energy,ideal gas equation,reaction mechanism and empirical formula in the working process of fuel cell,the models of the cathode cavity,anode cavity and membrane hydration were established.The calculation formulas of three kinds of polarized overpotential of fuel cell are described and the output voltage model of reactor is established.The structure and working principle of air supply system,hydrogen supply system and thermal management system in fuel cell system are introduced,and a semi-mechanism and semi-empirical simulation model is established.（2）The structure of Hardware in the Loop（Hi L）simulation platform and the function of FCU are briefly introduced,and the Hardware part of the controller is designed.Based on Veristand software combined with fuel cell control system to achieve the control of fuel cell working process.The fuel cell system control strategy automatically generates the code,and the generated code is downloaded to the controller.The output characteristics of fuel cell were simulated by Hi L simulation platform.The effects of reactor temperature,hydrogen inlet pressure,air inlet pressure,air inlet humidity,air excess coefficient and air inlet temperature on the output performance of fuel cell were analyzed by HIL simulation experiment.（3）The PID controller of the air supply system is designed.The input is the deviation between the target speed of the air compressor and the actual speed of the air compressor,and the output is the working voltage of the air compressor.The different mechanical and electrical pressure of air compressor represents the different speed of air compressor,that is,the different air intake flow.The optimal oxygen ratio can be controlled by adjusting the control coefficient of PID controller.The fuzzy PID controller is improved by fuzzification.The results show that the fuzzy PID controller has better control effect,faster response time and less overshoot.The control methods of air inlet pressure,hydrogen inlet flow rate and hydrogen inlet pressure are briefly introduced.（4）Build a 70 k W fuel cell test bench,apply the designed gas supply system control method to the control system,verify and evaluate the control method.The experimental results show that the gas supply system control method can accurately and timely control the hydrogen inlet flow rate and inlet pressure,air inlet flow rate and inlet pressure.In addition to the verification and evaluation of the control method,the working characteristics of the fuel cell system were analyzed according to the test results.The overall change rule of the reactor output voltage,power and single chip voltage was observed during the whole test process.The overall changes of air inlet flow rate,oxygen ratio,air inlet pressure and hydrogen air side pressure difference were analyzed under test conditions.The reasons for the changes of air inlet pressure,air inlet flow rate,hydrogen inlet pressure and hydrogen air side pressure difference under transient conditions are analyzed.