Research On Real Time Energy Management Strategy Of CVT Hybrid Electric Vehicle Based On SOC Accurate Estimation

The birth of the car has improved the way of human transportation,and at the same time,the energy and environmental problems can not be ignored.In the future,the automobile industry will develop towards new energy vehicles with low energy consumption,clean and environmental protection.CVT Hybrid Electric Vehicle(HEV)combines the advantages of pure electric vehicle and traditional fuel vehicle,which can achieve higher fuel economy and lower pollution emission,and the best matching between transmission system and engine working condition,so it has been paid more and more attention.Hybrid electric vehicle can play its maximum potential only through effective energy management strategy(EMS).It is expected to find the optimal torque distribution between engine and motor on the basis of meeting the basic requirements of vehicle power performance.Therefore,it is necessary to study the energy management strategy.In the process of formulating energy management strategy,accurate estimation of state of charge(SOC)of power battery pack is an important step.In this paper,the real-time energy management strategy of CVT Hybrid Electric Vehicle and SOC estimation method of power battery pack are studied(1)The parameters matching and modeling of related components of CVT Hybrid Electric vehicle are carried out,and the forward vehicle model is built.(2)Aiming at the problem of poor fuel economy of rule-based EMS,an equivalent consumption minimization strategy(ECMS)was established with battery SOC as state variables,CVT target speed ratio and motor torque distribution coefficient as control variables.The solution method of the optimal equivalent factor is introduced,and the influence of initial SOC and operating mileage on the equivalent factor is studied.Since the optimality of ECMS depends on the optimality of equivalent factor,which is related to the initial SOC,an adaptive equivalent consumption minimization strategy(AECMS)based on the state of charge of the battery is proposed to compare the power maintenance performance of the two strategies under single and continuous operating conditions.(3)In view of the battery SOC is an important basis for vehicle EMS formulation,different SOC estimation algorithm models are established and studied.The influence of ampere hour(Ah)method and unscented Kalman filter(UKF)method on SOC estimation is studied when the initial SOC is accurate or inaccurate.(4)Based on the HEV forward vehicle model,energy management strategy model and UKF algorithm model,the dynamic and economic performance are simulated to verify the correctness of key component parameter matching.The fuel economy and power maintenance of AECMS and ECMS are compared under continuous UDDS conditions to verify the effectiveness of vehicle EMS.