Research On Modeling And Control Strategy Of PEMFC Hydrogen Supply System Based On Ejection Circulation Structure

Hydrogen energy is an important part of the new energy system,and is considered an important way to achieve deep clean decarbonization in multiple fields because of its clean,environmentally friendly and renewable utilization characteristics.Among them,proton exchange membrane hydrogen fuel cells are widely used in transportation,power generation,aerospace and other fields because of their short start-up time and high energy conversion efficiency,but the lifetime of the stack and system stability are still remain the major barriers to the development of this technology.The anode hydrogen supply system,which affects the hydrogen transfer and impurity emission,is crucial to the stable operation and lifetime improvement of fuel cells.Therefore,the research work on the precise control problem of hydrogen supply system is important to guarantee the system stability and improve the lifetime of the stack.This thesis studies the structure and characteristics of a hydrogen supplier,an anode hydrogen recirculation system with an ejector.The hydrogen supply requirements from a high-power fuel cell engine is carefully examined as well.The contents of this thesis are as follows.1.The research on the working characteristics of the core components of the hydrogen supply system and the analysis of the influencing factors are carried out from the experiments.In this work,based on the fuel cell power system test platform,the ejector and hydrogen circulation pump test platform have been built.Through experiments,the variation of the circulation ratio with operating conditions and these condition’s on the ejector’s performance were investigated.In addition,the ejector performance under different operational modes was analyzed.In addition,the effects of different operating conditions on the output characteristics of the hydrogen circulation pump are investigated experimentally to provide data support for the system modeling analysis.2.Modeling and analysis are carried out for the core components and component coupling relationship of the hydrogen supply system.Based on the principles of thermodynamics and fluid dynamics,the mathematical models of stack,pipes and valves are established.The model of hydrogen circulation pump is established by using radial basis neural network modeling method.In addition,a combined mechanistic plus semiempirical approach is used to model the ejector.The component models are validated in Matlab/Simulink environment,and the results showed that the established models can accurately describe the dynamic and static characteristics of the components and the RMSE is 0.0948,which is a good fit.3.A hydrogen pressure controller is designed by combining control theory and optimization algorithm.First,the influence of disturbance factors on hydrogen pressure is analyzed.Then,a fuzzy PI controller was designed based on fuzzy theory,and a whale optimization algorithm is used to optimize the fuzzy quantization factor selection and add a feedforward link to suppress the disturbances.Finally,the controller performance is verified by simulation.The results show that the fuzzy PI controller optimized by the whale algorithm improves the dynamic response of the system,and the overshoot is only0.4kpa,which is about 1 times less than the fuzzy PI controller and better robustness when encountering disturbances such as exhaust gas.4.A circulating pump control strategy is designed by analyzing the circulating pump working state.Firstly,according to the different loads,the circulating pump working state is divided into two kinds: only hydrogen pump working and working together with the ejector.Then,the corresponding circulation pump control strategy is designed according to the different working states.Finally,the effectiveness of the control strategy is verified by simulation.The results show that the proposed control strategy can smoothly regulate the hydrogen circulation pump speed and make the hydrogen excess ratio always meet the system operation needs,and the computer programming is easy to implement,which has certain application value.