Research On Modeling And Control Of Microgrid With Fuel Cell

With the aggravation of energy crisis,the enhancement of environmental consciousness,microgrid is being developed fast for greater use of clean energy.Proton exchange membrane fuel cell(PEMFC)power generation technology becomes more and more popular recognized worldwide because of its many advantages,such as its product is water using hydrogen as fuel,zero emission,no pollution,high power density and efficiency,and reliable operation.In this dissertation,the modeling and control strategy of microgrid based on PEMFC is chosen as study object.The thesis researches on modeling and simulation of PEMFC system,parameter identification for PEMFC model,PEMFC control strategy based on the former DC/DC converter,and modeling and power smoothing control strategy for microgrid containing wind power system and PEMFC.Research works and frameworks of the paper are as follows.First of all,according to the working principle of PEMFC and the associated literatures,the thesis displays electrochemical model and dynamic model of PEMFC mathematical formulas of single cell and the derivation process of mathematical formulas.The corresponding simulation models are created in MATLAB/simulink software,and then the change process of output voltage,power and efficiency in different current density of two models are simulated and comparatively analyzed.The simulation results show,on one hand,the simulation models are accurate,on the other hand,dynamic model of PEMFC has better dynamic reponse ability and can describe the actual working course better.Secondly,aiming at the model parameters uncertainty problem,particle swarm optimization(PSO)algorithms with five different inertia weights are present to identify parameters of PEMFC model.Based on the proposed model and combined with the actual operating datas of PEMFC,a series of tests of polarization characteristics are carried out.Also,the parameters which can ensure curve fit of simulation results with actual datas are selected.Thirdly,aiming at the problems of PEMFC,such as large output voltage range,slow dynamic response,and low output power,by a passive control method and the passivity of DC/DC converter,a passive control strategy for the system incluing PEMFC and former DC/DC converter,is present.The simulation result indicates that,with the PI control comparison,the system which adopts the passivity-based control strategy has better resistivity against load disturbances and more excellent dynamic reponse ability.Finally,a microgrid model containing wind power system and PEMFC is built.According to the different function and operational characteristics,the corresponding control strategies are proposed.To solve the problems of wind fluctuation and fault ride-through,a microgrid model containing wind power system and PEMFC,which integrates an energy circulatory system,is built.The circulatory system is composed of an electrolyzer,a hydrogen tank and a PEMFC.Based on the analysis of the different function and the operation characteristic of every unit,the coordinated control strategy of system is designed.MATLAB simulation results show that the system can effectively suppress the fluctuation of output power caused by random variation of wind and capture maximum wind energy,but also has a satisfactory performance during more serious grid voltage sags occurring.