Study On Model And Control Strategy In Air Supply System Of PEMFC In Vehicles

Proton exchange membrane fuel cell (PEMFC) is a main powr source of electric vehicles in fuel cells. And air supply system is one of the mainly constitute of PEMFC, its air flow and air pressure affected fuel cells' stack not only electrochemistry reactivity rate and proton exchange membrane's performance, but also generate electricity efficiency and load ability. It's very difficult to modeling and control for air supply system as its stronger nonlinear and coupling. In order to improve air supply rate to insure fuel cells running in best state, the paper studied on modeling and control strategy of air supply system in fuel cells. The main studying content and production was as follows.It put forward prediction model between target value of air flow and air pressure with fuel cells'output power basing on Elman dynamic ANN, according its self-adapting distinguish for non-linear model. Simulation approved that its prediction model was validity. It advanced dynamic responding speed of air supply system of PEMFC in electric vehicle, and had better control result.It designed decoupling matrix of air flow and air pressure aim at its non-linear and strong coupling. It adopted recursion identification arithmetic to real time identify model parameters of air flow, air pressure control channel, and its control variable coupling channel. By adjusting parameters of decoupling matrix, it made air flow, and air pressure control be independent, the one didn't affect by the other.Air flow of PEMFC in electric vehicles changed following output power of fuel cells. For advancing its responding speed, it brought forward Fuzzy-PID compound control strategy of air flow basing on its mechanism-model. By setting control limit value, and adjusting control parameters, Fuzzy-PID compound control improved contol performance of air flow for it had speediness of fuzzy control and accuracy of PID. Simulation result showed that air flow responding time adopting Fuzzy-PID compound control could shorten half than adopting traditional PID.Air pressure of PEMFC in electric vehicles changed not only following with fuel cells'output power, but also coupling with air flow, so it's difficult to control. It advanced neural-PID control strategy of air pressure so as to identify model of air pressure control loop online using ANN identifying non-linear system. And it adopted neural-PID control to adjust control parameters kp, ki and kd, through self-studying of ANN and self-regulating of authority coefficient, so that stable states of air pressure control loop were better corresponding to PID control parameters. Simulation result showed that air pressure adopting neural-PID control have adaptability for fuel cells' output power and air flow.On all accounts, the paper founded model of given value prediction of air flow and air pressure in PEMFC air supply system of electric vehicles. And it designed decoupling matrix of air flow and air pressure using method of on the cross matrix. It set up different control model basing on mechanism mode and experiment model according characteristics of air flow and air pressure control loops. It adopted different control strategies according different model to make air flow quickly responding output power changes, and make air pressure having stronger adaptability for output power and air flow changes. Simulation result showed that the control strategies were validity. The air supply control system could satisfy practice need of PEMFC in electric vehicles.