Research On Shutdown Optimization Strategy Of Fuel Cell Power System

Proton exchange membrane fuel cell(PEMFC)is widely used in the field of transportation because of its low noise,environmental friendliness and high conversion efficiency.However,problems of reliability and durability are still important barriers hindering the development of this technology.The fuel cell has a variety of operation modes in the actual working process,and the degradation caused by the shutdown operation mode is the most significant.The optimization of membrane water content and hydrogen-air interface during the shutdown process is crucial to improve its operation reliability and durability.This thesis takes the typical fuel cell power system as the research object,divides the shutdown process into gas purging link and voltage relief link based on the system shutdown demand,and integrates the stack mechanism and component mechanism optimization to model.The gas purging strategy and voltage relief strategy during shutdown are designed to optimize the water removal effect,reduce energy consumption and durability degradation.The main research contents are as follows:Firstly,modeling the gas purging link during shutdown process of fuel cell power system.The basic principle of gas purging during shutdown process is analyzed from the perspective of mechanism,and a three-stage gas purge model is built based on the transmission characteristics of liquid water during shutdown process.Also,the shutdown gas purging experiment is designed to identify the parameters and verify the accuracy of the model,and a model that can accurately describe the gas purging in the shutdown process is obtained.Based on the model,the influence of different operating conditions on the gas purging in the shutdown process is analyzed.Secondly,studying on the strategy of gas purging during the shutdown process of fuel cell power system.The objective function derived from economy and the penalty function based on the evaluation of purging effect are designed.The particle swarm optimization algorithm and genetic algorithm are comprehensively used to optimize the operating conditions of the gas purging in the shutdown process,and the model simulation is carried out.The simulation results show that the energy efficiency of gas purging link is optimized by 15.9%,which improves the energy efficiency of the system during shutdown process while ensuring the reliability of the fuel cell.Finally,studying on voltage relief strategy during shutdown process of fuel cell power system.By analyzing the influencing factors of voltage relief during shutdown,two voltage relief strategies based on hydrogen purging and air purging are designed.The model of oxygen diffusion rate and pressure difference between anode and cathode in the voltage relief link is built,and the model simulation of the two strategies is carried out.The simulation results show that the voltage relief strategy based on hydrogen purging can reduce the decay of the proton exchange membrane and improve the durability of the fuel cell.