PEM Fuel Cell Modeling And Humidity Optimizing Control

In recent years,with the proposal of the "Shuang Tan" goal,hydrogen energy and fuel cells have received more and more attention.Proton exchange membrane fuel cell(PEMFC)is considered to be one of the most promising new energy sources because of its clean,efficient and renewable advantages,and has been gradually applied in power generation,automobiles and other fields,and has certain industrialization prospects;However,the limited performance and lifetime of PEMFC seriously restrict its application and development.Humidity in actual PEMFC operation is a key variable affecting stack performance and lifetime.Load fluctuations during PEMFC operation will cause fluctuations in cathodic humidity,and high and too low cathodic humidity will make its humidity control difficult.At the same time,PEMFC in different operating stages,humidity changes have the characteristics of nonlinearity,interference and strong coupling,etc.,it is difficult to ensure that on the basis of meeting the output performance of PEMFC,the humidity of PEMFC is controlled in a suitable range to avoid the phenomenon of "flooding" and "membrane drying".Therefore,aiming at the problems of humidity interference suppression and operation optimization of fuel cells,PEMFC modeling and humidity optimization control methods under different working conditions are studied.The main research contents are as follows:(1)The structure and operation principle of PEMFC system and its humidity subcontrol system are introduced,the influence and influencing factors of cathodic humidity on the output voltage of PEMFC are analyzed,and the characteristics of different operating conditions of PEMFC and the problems of humidity control are given.(2)Based on the theoretical basis of thermodynamics,electrochemistry and the physical fuel cell,the key components such as the cathode intake system and fuel cell stack of the fuel cell and the dynamic characteristics such as cathode flow and output voltage are modeled and analyzed,and the constructed model can better reflect the output voltage and flooded film drying characteristics of the fuel cell.(3)Aiming at the problem of humidity rapid disturbance suppression under large current load fluctuation,a PEMFC humidity control method based on the combination of fuzzy feedforward and self-disturbance rejection was studied.Firstly,the dynamic characteristics and model parameters of cathode humidity are analyzed.On this basis,the structure and principle of PEMFC humidity control based on fuzzy feedforward + selfdisturbance rejection are given.In order to enhance the speed of the controller,a fuzzy feedforward controller is designed,and a reference tracking differentiator based on the characteristics of humidity change is designed according to the law of humidity change.Aiming at the problem of humidity state estimation,an observer of humidity and its interference expansion state was designed.Using the actual humidity and state error,a state feedback controller based on the change of humidity error is designed.Through the40 KW PEMFC humidity control experiment,it is shown that the proposed method can better suppress the fluctuation of the relative humidity of the cathode under the condition of large load current fluctuation,and effectively avoid the occurrence of flooded film drying.(4)Aiming at the problem of humidity stabilization and operation optimization under high output power of PEMFC,this paper studies a net output power/humidity optimization control method based on particle swarm optimization(PSO)to optimize PID parameters.Firstly,the principle and structure of the control method are given.The optimization targets of humidity and power output are analyzed,and the comprehensive optimization function is established.According to PEMFC humidity and power input and output characteristics,PID control algorithm,The PSO algorithm is used to optimize the design of the controller parameters.Through the 40 KW PEMFC humidity control experiment,it is shown that the proposed method can ensure the effective control of humidity under the condition of high output power performance.