Research On Energy Management Strategy Of Parallel Hybrid Electric Vehicle With Consideration Of Battery Aging

The establishment of a resource-conserving and environment-friendly society is an important task in today's world.For this reason,the automotive industry is gradually moving towards the direction of electrification.Due to its advantages of high efficiency,low energy consumption and low emissions,hybrid electric vehicles(HEV)have become a potential trend in the industry.However,a new power source,motor,is introduced into the HEV,which brings about the problem of how to split the power between the engine and the motor,that is,the energy management strategy.In addition,the battery will be accompanied by a series of side reactions during the charge and discharge process,which will be bound to bring about the aging problem of the battery(performance degradation).It will not only affect the efficiency of the vehicle but also increase the battery replacement cost.The emergence of these problems raises new challenges in terms of energy optimization,control,and battery aging.In addition,considering the application of the controller in the real vehicle system,we also have high requirement for the rapidity of the method.In view of the above problems,this paper takes the CVT(continuously variable transmission)parallel HEV as its research object,considering the two goals of fuel economy and battery aging comprehensively.Reducing fuel consumption and battery aging by optimizing engine and motor torque distribution and CVT ratios.In order to solve the multi-objective constrained nonlinear control problem and improve the computational efficiency,this paper adopts the framework of model predictive control(MPC),combining with the principle of Pontryagin's minimum principle(PMP)and bisection method to obtain the optimal control quantity explicit solution.The effectiveness of the energy management strategy and the real-time performance of the controller are verified by off-line simulation experiments and hardware-in-the-loop experiments.The main work is summarized as follows:Firstly,the vehicle structure and modeling method of each component are analyzed.The vehicle simulation model of the CVT parallel HEV(PHEV)for energy management strategy development is built in AMESim and the model parameters are matched.In order to verify the rationality and functionality of the vehicle model,a rule-based energy management controller was built in the Simulink environment,which lays the foundation for the design of the optimized energy management strategy.Secondly,in order to solve the problem of energy distribution in HEV and the characteristics of the battery will be gradually degraded during the working process,the mathematical model of engine,motor,battery(including internal resistance model and battery aging evaluation model)oriented to controller design have been established for the purpose of simultaneously realizing vehicle economy and reducing battery aging.And then,the energy optimization problem is organized into a multi-objective constrained nonlinear optimization control problem.Thirdly,an energy management strategy optimization controller is built in Matlab.The main scheme is: Under the framework of MPC,combining the PMP and bisection method to find the explicit solution of the optimal control problem,the optimal engine torque,motor torque,and CVT ratio will be obtained in the prediction horizon.By using AMESim and Matlab offline co-simulation experiments,when the battery aging is not considered,comparison experiments are conducted based on the rule-based method and the optimization-based method,and the economic advantages of the optimized energy management strategy are verified.Then,when considering the battery aging,the energy management strategy is verified under different standard cycle conditions,and compared with the case of not considering the battery aging.It proves the effectiveness and necessity of the energy management strategy with consideration of battery aging that proposed in this paper.Finally,based on dSPACE and DSP real-time simulation platform,the hardware in the loop experiment is carried out for the controller,which verifies the effectiveness and real-time performance of the energy management strategy.The specific scheme is: The whole vehicle simulation model is based on the dSPACE real-time simulation platform,downloading the vehicle simulation model to dSPACE as the simulation vehicle system;The controller part is through the DSP and FPGA hardware platform,the controller generated C code ported to the DSP,through the AD / DA to establish the communication between DSP and dSPACE.