Research On SOC Estimation And Energy Management Of The Hybrid Energy Storage System In Vehicle

Energy crisis,environmental pollution and other issues make it imperative to develop new energy vehicles.In order to ensure the driving range and power performance of pure electric vehicle(PEV),the power supply of PEV which is one of the most promising models must have the characteristics of high specific energy and high specific power.As energy storage device of vehicle,a single power battery has the disadvantages of low power density,which is difficult to meet the dynamic performance requirements of the vehicle.Therefore,it is necessary to consider the combination of ultracapacitor with high power density and battery with high energy density to form a Hybrid Energy Storage System(HESS)which can complement the insufficient of single battery energy storage system,thereby achieving the dual goal of driving range and dynamic performance requirements of electric vehicle.This paper selects the lithium-ion battery and ultracapacitor as energy storage power of PEV.On the basis of characteristic analysis and parameter matching of HESS,the emphasis is put on the study of the state of charge(SOC)estimation and energy management control strategy of HESS,specific research contents are as follows:1.In order to realize accurate and fast online prediction for the battery SOC,ensure that the energy management system(EMS)of HESS can obtain real-time and precise SOC information,an improved online kernel extreme learning machine(IO-KELM)algorithm was proposed to establish prediction model.Compared with kernel extreme learning machine(KELM)and Direct Online-KELM(DO-KELM)algorithm,simulation results indicate that the IO-KELM has higher prediction accuracy,stronger robustness and faster calculation speed.2.In order to reasonably distribute the charge and discharge power of battery and supercapacitor,according to the qualitative relationship between the ultracapacitor SOC and vehicle speed,a fuzzy control strategy based on vehicle speed was presented to design controller.Compared with the traditional fuzzy control of HESS,simulation results show that the fuzzy control of HESS based on the speed can fully exert the high power compensation performance of the supercapacitor.The charging and discharging characteristics of the battery can be better optimized.Battery life is further extended.3.In order to further verify the feasibility and superiority of HESS and its energy management control strategy,the experiment platform of the small power HESS was built,and the hardware circuit and software were designed in detail.Based on the above,the experiment study of energy management system was carried out.The experimental results show that,compared with the single battery and passive HESS,the performance of semi-active HESS is better,compared with the traditional fuzzy control,the fuzzy control of HESS based on vehicle speed is better in the maintenance of supercapacitor SOC and the optimization of battery current.