Research On Composite Energy Storage System In Electric Vehicle

The use of fuel cars has led to oil shortages and worsening environment.Therefore,many countries are promoting electric vehicles.Electric vehicle is driven by electric energy,which has high energy utilization and environmental friendliness.A key link in vehicle performance is energy storage system.As a traditional vehicle mounted energy storage device,battery has a serious impact on the application of pure electric vehicle because of its low power,slow charge and discharge,and limited storage capacity.To solve this problem,a composite energy storage system is proposed in which parallel connection of lithium battery and super capacitor.Based on the principle of compound energy storage system,the control strategy of lithium battery,ultracapacitor,DC/DC converter and energy storage system is studied in this paper.The main work is(1)to study the principle of the electronic control system,the energy request of the vehicle under three operating conditions,analyze the disadvantages of the battery as the vehicle power supply,and propose a composite energy storage system.The power allocation is established by the control strategy of the energy storage system and the DC/DC converter(2)to study the capacity characteristics of the lithium battery.The optimal charge discharge current interval of the lithium battery in the composite energy storage system,the stability of the two topology structures of the supercapacitor,the improved voltage sharing strategy,the analysis of the DC/DC converter,and the design of the interlaced parallel structure of the multiphase circuit.(3)the traditional PID control algorithm can not achieve the desired effect for the control of nonlinear systems,so it is able to approach nonlinear systems in a variety of complex situations and effectively control nonlinear systems or even uncertain systems in a variety of complex situations.(4)in the Matlab/Simulink simulation environment,the model of lithium ion battery,super capacitor bank and composite energy storage system is set up.In a certain cycle,the charge state of the energy storage device,the simulation of the mileage of the vehicle and the result of the analysis are analyzed.From the contrast curve of the charge state(SOC)and the mileage contrast curve of the lithium battery,it is known that for the composite energy storage system,the lithium battery SOC is slow down,the vehicle power is stronger,and the driving mileage is longer.It shows that the adaptive PID algorithm has good dynamic stability,high control efficiency for nonlinear system,and effective power allocation between power sources of energy storage system.