Research On Acceleration Process Optimization Control Strategy For Electric Vehicle Based On Energy Consumption And Battery Life

The research on the relationship between the electric vehicle power system energy saving control method and its power battery life has become one of the hot research topics in the field of new energy vehicles at home and abroad.In this paper,it aims at the current commonly used electric vehicle acceleration energy saving control strategy,which not only fails to fully analyze the nonlinear acceleration method(such as acceleration and its change rate)during the acceleration process and the target velocity on the interaction of electric vehicle energy consumption,but also does not consider the required power battery discharge current and the impact of its change rate on battery life,resulting in unstable electric vehicle energy saving effects,low battery discharge efficiency and short battery life,and even the electric vehicle energy consumption increasing.Aiming at the above problems,the acceleration process optimization control strategy for electric vehicle based on energy consumption and battery life has been studied.The research is funded by the Key-Area Research and Development Program of Guangdong Province(No.2019B090911002)and the Science and Technology Plan Project of Guangdong Province(No.2014B010106004).Based on the basic principles of the electric vehicle energy saving control and power battery capacity attenuation mechanism,and taking the power system of pure electric vehicles and Plug-in hybrid electric vehicles(collectively referred to as electric vehicles)as the research object,the thesis carries out the research work on acceleration process optimization control strategies for electric vehicle based on energy consumption and battery life from three aspects which are the principle of electric vehicle energy consumption during the acceleration process,the interaction mechanism between the electric energy consumption during the acceleration process and the power battery life and the acceleration control strategy based on energy consumption and battery life respectively.The main research work includes:1.In view of the present electric vehicle energy saving acceleration control method failes to fully consider the nonlinear acceleration way(such as the acceleration and its change rate)during the acceleration process and the target velocity on the interaction of electric vehicle energy consumption,which leads to energy saving effect of the electric vehicle is not stable,even electric vehicle energy consumption increases,an acceleration curve optimization method for electric vehicle based on minimum energy consumption per kilometer is proposed.The relationship between vehicle velocity,acceleration and energy consumption of electric vehicle is analyzed through the power system energy consumption experiment in the acceleration process of electric vehicle;the energy consumption per kilometer model of electric vehicle is established,and the influence of acceleration and its change rate and target velocity on the energy consumption of electric vehicle are discussed from two aspects of linear single acceleration and nonlinear multiple accelerations;and the energy consumption per kilometer E_b-j corresponding to single acceleration straight line,monotonous continuous upward convex and downward concave multiple accelerations curves is deduced,and mathematical induction is used to prove that when the vehicle velocity during the acceleration process is lower than the target speed,the order of energy consumption per kilometer of each acceleration curve from high to low is:concave multiple accelerations curve,single acceleration straight line and convex multiple accelerations curve.In addition,the relationship between different acceleration curves,power performance and occupant comfort is discussed,and the electric vehicle multiple accelerations curve with minimum energy consumption per kilometer(MEPK)is optimized by genetic algorithm,which takes into account the energy consumption characteristics,power performance and occupant comfort of electric vehicles.2.Aiming at the pure electric vehicle energy saving acceleration control methods failes to consider the required power battery discharge current and the impact of its change rate on battery life,which will accelerate battery capacity degradation rate and cause short driving range.To solve these problems,an acceleration curve optimization method for pure electric vehicle based on energy consumption and battery life has been proposed.It studies the relationship between the electric vehicle MEPK multiple accelerations curve and its power battery discharge current and its change rate,establishes the battery capacity attenuation model of pure electric vehicle during driving,discusses the power battery discharge current and its change on the capacity utilization and its attenuation,the percentage of capacity loss per kilometer q_loss is used to measure the power battery capacity loss under different acceleration driving conditions.The interaction relationship between the electric vehicle MEPK multiple accelerations curve,E_b-j and q_loss is studied.In addition,the interaction between first acceleration and acceleration time on E_b-j and q_loss is also discussed.The non dominated sorting genetic algorithm(NSGA-II)with elite strategy is used to optimize the multiple accelerations curve of pure electric vehicle,which takes into account the energy consumption characteristics and the power battery capacity attenuation characteristics.3.Research on acceleration control strategy for pure electric vehicle based on energy consumption and battery life has been carried out.From the aspect of motor energy consumption,the interaction between the optimal multiple accelerations curve of pure electric vehicle and the permanent magnet synchronous motor maximum torque per ampere(PMSM-MTPA)control method and the flux weakening control method based on voltage closed-loop is studied.Aiming at the optimal multiple accelerations curve of pure electric vehicles,the relationship between the velocity and acceleration of pure electric vehicles and the optimal dq axial current controlled by PMSM-MTPA is established.With the speed as the control target,the PMSM-MTPA control method based on the optimal multiple accelerations curve of pure electric vehicle is proposed under typical urban acceleration conditions,and in the typical suburban acceleration conditions,the flux weakening control based on voltage closed-loop is used to achieve the high motor speed operation area corresponding to the suburban conditions.The effectiveness of the strategy in reducingE_b-jand q_loss and improving motor efficiency is verified through the simulation and quantitative comparison analysis of pure electric vehicle energy consumption,power battery capacity loss rate and motor efficiency under different acceleration control strategies.4.Experimental research on different acceleration control strategies has been carried out.The power system and vehicle tests of pure electric vehicles with different acceleration curves are carried out,and the effectiveness and feasibility of the pure electric vehicle acceleration control strategy based on energy consumption and battery life in reducing E_b-j and q_loss is verified and analyzed experimentally.