Energy Management Strategy Research Of Lithium Battery/Super Capacitor Hybrid Energy Storage System For Electric Vehicles

As the energy source of electric vehicle,the energy density and power performance of energy storage system(ESS)is very important.The combination of lithium battery(with high energy density)and super capacitor(with high power density)to form a hybrid energy storage system(HESS)is an effective way for electric vehicles which require long driving distance as well as better dynamic performance.But at the same time,it is necessary to solve the problems like parameters matching and energy management strategy formulating of HESS.This paper mainly studies lithium battery/supercapacitor HESS,including matching HESS parameters,and formulating the corresponding energy management strategy,completing energy management strategy software simulation and rapid prototype experimental verification.The main contents are as follows:(1)Analyze characteristics of lithium battery,supercapacitor and bi-directional DC/DC.Based on related data,establish the lithium battery equivalent internal resistance model,the supercapacitor classical equivalent model and the efficiency model of bi-directional DC/DC.(2)Select the system structure and match parameters of HESS.Select HESS structure from comparison results.According to vehicle longitudinal dynamic and experimental data,establish the power consumption calculation model.The continuous power-energy(CPE)function is used to match the HESS parameters according to vehicle's power consumption characteristics in CATC,the design objective and vehicle's layout condition are considered at the same time.(3)Propose an energy management strategy of HESS based on logic rules and complete its software simulation.Based on the analysis of the HESS main working states,make the rules of energy management strategy and select corresponding logical threshold parameters,build energy management strategy model.By integrating all models,establish the energy management strategy software simulation environment of HESS,complete software simulation of the energy management strategy.The software simulation results show that the supercapacitor's power characteristic is used effectively,the “peak-cutting and valleyfilling” of lithium battery output power is realized,it is of positive significance to the life protection of lithium batteries,and it has a certain adaptability to different driving condition.(4)Design and build a HESS energy management strategy rapid prototype verification platform,based on this platform,the energy management strategy proposed in this paper is verified by experiments.The experimental platform uses dSPACE Microlabbox as the controller hardware,the energy management strategy is deployed on a small HESS,and electric load simulation equipment is used to simulate vehicle power demand.The experimental results confirm that the supercapacitor's power characteristic is used effectively,the “peak-cutting and valley-filling” of lithium battery output power is realized,it is of positive significance to the life protection of lithium batteries,and it has a certain adaptability to different driving condition.