Reserach On Control Strategy Of Synergic Power Supply System For A Certain Type Electric Van

With the rapid development of the domestic Internet economy and the outbreak of the e-commercial industry,the demand for electric vans is also growing.At present,electric vans only have battery packs to provide output power,but there are still some deficiencies in vehicle power,economy and renewable energy utilization.Therefore,this paper adds ultracapacitors to a synergic power supply system on the basis of a electric van and makes a strategic study.The main research work of this paper is as follows:(1)For the main components of a electric van with synergic power supply,a set of perfect parameter matching methods are formulated: selecting the appropriate motor according to the maximum speed,maximum climbing gradient and the power requirement of 100 km acceleration;completing the parameter matching of lithium-ion battery pack through the requirement of endurance mileage according to the advantage of high energy density of lithium-ion battery;and according to the power density of supercapacitor.By analyzing the power-energy relationship of the logistics vehicle under cyclic and accelerated starting conditions,a comprehensive CPE function is obtained to match the energy of the supercapacitor.The results of parameter matching provide a basis for parameter input of the vehicle model in the following chapters.(2)Firstly,the topological form of the power system with synergic power supply is introduced.By analyzing the advantages and disadvantages of different topological forms,the appropriate topological form is selected for the logistics vehicle.Then an experimental platform for the analysis of charge-discharge characteristics of lithium-ion batteries and ultracapacitors is built.Then the advantages and disadvantages of lithium-ion batteries and ultracapacitors are more clearly and intuitively understood through constant current charging and discharging experiments.The equivalent circuit model is established by referring to the charging and discharging characteristics of lithium-ion batteries,and the model parameters are identified by using the experimental data.Finally,the accuracy of the model and parameters is verified.(3)Five basic working modes of the topological form chosen by the power system of synergic power supply are introduced firstly,and the academic research process of logic threshold and fuzzy logic is briefly introduced.Then the logic threshold control rules and logic threshold control flow are designed for the logistics vehicle,and the appropriate threshold is selected according to its cycle conditions by integral averaging method.Finally,aiming at the deficiency of logic threshold control strategy,a fuzzy logic control strategy is proposed.The fuzzy logic controller takes demand power,battery SOC and supercapacitor SOC as input,and takes the ratio of battery output power to demand power as output.The membership function of input and output variables and the fuzzy control rules are determined by analysis.(4)Firstly,according to the results of parameter matching and parameter identification,the whole vehicle dynamics simulation model of the logistics vehicle is established in Cruise,and the calculation task is set according to the dynamic requirements.Then,brake energy recovery module,logic threshold control module and fuzzy logic control module are established in Simulink,and two different control strategies are generated.DLL file and the whole vehicle model established in Ruise are simulated jointly.Finally,the simulation results show that the fuzzy logic control strategy is more effective than the logic threshold control strategy in reducing the high current discharge of lithium ion batteries and improving the energy utilization of the synergic power supply.