Research On Modeling And Control Of Electric Vehicle Fuel Cell System

As energy shortages and environmental pollution problems become more and more prominent,the research of developing and promoting renewable energy has increasingly become the focus of social attention.Proton exchange membrane fuel cell(PEMFC)is a device that generate electric energy through the reaction of hydrogen and oxygen,which has the advantages of high energy density,stable energy output,no pollution,low operating temperature,etc.It has become the development direction of a new generation of automobiles.The fuel cell system consists of several subsystems,such as air supply subsystem,hydrogen supply subsystem,and thermal management subsystem.In order to improve the reliability and safety of the fuel cell,it is important to model and control each subsystem.The existing research mainly considers the influence of a single subsystem such as gas supply subsystem or thermal management subsystem on the output performance of the stack,and neglects the combined effects of different subsystems on the output performance of the stack.In order to achieve efficient and safe operation of the fuel cell system,and improve the efficiency of the fuel cell system,the following aspects of research related to the fuel cell system is done in this paper:(1)Research status and significance: The research status of modeling and control of PEMFC is briefly described,and the significance of gas supply system and thermal management system control is explained.Finally,the significance of this paper is further explained;(2)System modeling: A fuel cell integrated system model,including gas supply system model(air compressor model,supply pipe model,cooler model,humidifier model,cathode flow model,membrane hydration model,return pipe model,hydrogen cycle system model,anode flow model)and thermal management system model(cathode gas temperature model,anode gas temperature model,stack temperature model)is built in this paper.A method for estimating stack temperature using the mean values of cathode outlet gas temperature,anode outlet gas temperature and coolant outlet temperature is proposed for the first time,and the stack model,the gas supply system model and the thermal management system model are simulated and analyzed respectively;(3)Design and implementation of control strategy:1)According to the mechanism model of the fuel cell system,the state space equation of the fuel cell system is established.The load current is used as the external disturbance,and the model predictive controller(MPC)and the sliding mode controller(SMC)are designed based on the model.The two controllers are designed and simulated by MATLAB/Simulink.The simulation results show that: both two controllers can achieve steady-state tracking,but the sliding mode controller has better control performance,stronger robustness and faster convergence;2)Different from the existing literature that the load current is considered as the external disturbance.In the fifth chapter of this paper,the change rate of current is defined as a new control variable.Under the action of the sliding mode controller,the system power tracking of the stack is realized by adjusting the change rate of current.