Modeling And Control Of Vehicle Fuel Cell Air Supply System Based On Voltage Regulation

Energy is an important material foundation for improving people’s quality of life and promoting social and economic progress and development.With the current rapid development of the world economy and increasing energy consumption,the surplus of fossil energy has become less and less,and the rising trend of energy prices has rapidly risen to a record high.While the economy is developing rapidly,the level of human pursuit of quality of life continues to rise,but the greenhouse effect and environmental pollution caused by the use of traditional energy sources are becoming more and more serious,which restricts the healthy development of society and economy.Proton exchange membrane(PEM)fuel cell can directly convert the chemical energy of the fuel into the required electrical energy.It has the advantages of high efficiency,cleanliness,renewable and safety,and is considered to be the future development direction of human energy strategy.The complete vehicle PEM fuel cell system is composed of 4 subsystems,namely an air supply system,a hydrogen supply subsystem,a temperature/humidity management system,and a power regulation system.Among them,the stable and rapid control of the air supply system is very important for system performance.Considering that the fuel cell output voltage is lower than the load demand voltage and is easily affected by the load current,it is necessary to use a step-up DC/DC converter for voltage regulation.In this paper,the vehicle-mounted PEM fuel cell air supply system and boost DC/DC converter are the research objects.Aiming at the problems existing in the actual operation of the vehicle-mounted PEM fuel cell air supply system,the following research work is carried out:Firstly,the research background and significance of the vehicle-mounted PEM fuel cell system are introduced,and the domestic and foreign research status of the vehicle-mounted PEM fuel cell air supply system modeling and control algorithm is analyzed and summarized.Secondly,analyze the working mechanism of each component of the on-board PEM fuel cell air supply system.Under assumptions,a control-oriented multi-input and multi-output nonlinear model of the on-board PEM fuel cell air supply system is established,and the system-level Pukrushpan ninth-order model is established.Make a comparison to verify the model.There are uncertainties in the parameters of the air supply system during long-term operation.Based on the established fourth-order model,a differential observer is designed to observe the stack cathode pressure,and it is verified that the observer can resist the system uncertainty and effectively observe the stack cathode pressure.Then,considering that the control-oriented air supply system has the characteristics of strong nonlinearity,strong coupling,parameter uncertainty,etc.,a nonlinear robust controller composed of a feedback linearization controller and a robust compensator is designed.The nonlinear coupling model is converted into two decoupled linear models,and the control voltage and throttle opening of the air compressor are controlled by the robust controller method of the nonlinear system to stably and quickly follow the desired oxygen excess ratio and Cathode stack pressure.Through MATLAB/Simulink,the on board PEM fuel cell air supply system over-oxygen ratio and fuel cell stack cathode pressure are simulated and tracked,which verifies the effectiveness of the robust control of the nonlinear system.Finally,in view of the softer output voltage characteristics of the on board PEM fuel cell system,a feedforward and feedback control algorithm is used for the boost DC/DC converter system to adjust the fuel cell system voltage to the load voltage demand value,which will also affect the fuel cell power,the stack current affects the performance of the air supply system.Integrate the DC/DC converter subsystem and the on board PEM fuel cell air supply subsystem,and adopt a distributed control structure.The simulation experiment shows that the fuel cell independently provides good control performance of the load demand power.