Modeling And Model Predictive Control Of Proton Exchange Membrane Fuel Cell

Environmental issues and energy crises have prompted major car companies to invest in the research and development of various new vehicle hybrid power sources.The proton exchange membrane fuel cell(PEMFC)has the possibility of becoming the main power source in vehicular applications due to its high power density and zero emission.In this paper,the corresponding modeling,efficiency optimization control,simulation and experimental verification research are carried out for the PEMFC and its hybrid power system.The main work is as follows:Taking a certain 75 kW fuel cell as a prototype,by fully analyzing the working characteristics and principles of the PEMFC system,the focus is on building a PEMFC nonlinear simulation model consisting of an air supply subsystem and a stack.Among them,the air supply subsystem mainly considers the supply manifold and air compressor;while the stack mainly considers the cathode and the system output power model.The simulation results show that the linear model can better accurately reproduce the steady-state accuracy and dynamic characteristics of the system.Considering the optimal tracking issue of the net output power for the proton exchange membrane fuel cell(PEMFC),a model predictive control(MPC)based robust offset-free optimal control strategy is proposed,which aims at achieving the steady state offset-free tracking of desired net output power,in terms of system’s operating constraints,model mismatching and external disturbances,and is for the purpose of optimizing the system efficiency,by regulating the PEMFC’s operating points at around the optimal(sub-optimal)operating curve.The control strategy is composed of state observer,target calculator and MPC controller.The state observer estimates the state variables,model mismatch and external disturbances;The target calculator tracks the optimal net output power and constrains the operating boundary of the air compressor.The MPC controller relaxes the working boundary constraints of the air compressor to obtain a feasible explicit solution.Finally,a standard vehicular fuel cell stack test cycle and the external disturbance from the daily temperature and relative humidity,the comparison with the LQG control strategy show that the offset-free MPC control strategy proposed in this paper can not only ensure the accurate tracking of the net output power,but also obviously improve the output efficiency of the system.Based on the above research,we built the first fuel cell hybrid power system based on electric motorcycle platform based on Zongshen Group,and further carried out the corresponding hybrid power modeling and control method experimental research.Based on the linear model,a MPC control strategy is designed to achieve power distribution of the stack/battery,and a explicit model predictive control(EMPC)control strategy is designed to improve the real-time performance of the control strategy.Finally,a hybird control unit(HCU)based on the Freescale MC9S12XEP100 micro controller unit was developed,and a corresponding hardware-in-the-loop(HiL)simulation platform was built to verify the performance of the HCU.Experimental results show that both MPC and EMPC can achieve power distribution,but EMPC transforms the Quadratic Programming(QP)problem solved online into the Polyhedron Piece Wise Affine(PPWA)equation obtained offline,while ensuring the control performance,the real-time performance of the HCU is significantly improved.It will lay the foundation for Zongshen’s motorcycle engineering application in the next step.