| Pure electric vehicle(EV) has become the mainstream of the development of car today because of its characteristics of environmental protection and energy saving.But for that there still exist some difficulties in technique at present, EV cannot be large-scale popularized. Among the difficulties, the lack of battery life is one of the most urgent problems of EV at present. In order to improve the battery life of EV, power battery carrying at the present stage is gradually transited into the lithium ion batteries of higher power density. However, the fact that the lithium ion battery produces a lot of heat on high rate discharge for its internal resistance and will make the discharge efficiency lower,which affects the battery life of EV directly.In order to solve the above problems, the charge and discharge process of lithium ion battery was further researched and the battery power management control strategy of increasing the battery life of EV under the premise that it does not affect the normal exercise of the vehicle was put forward. The accuracy and feasibility of this strategy was verified by experiment. The main research work is as follows:1. According to the main technical parameters of a certain type of MPV and the related technical standards of EV, we put forward the performance index that it should achieve after electrification reform, and had the parameters matching and selection of electric drive system and battery module.2. According to the QC/T 743-2006(lithium-ion battery for electric cars) standard requirements, we formulated the lithium battery charge and discharge performance test plan, established test platform and completed the test of battery sample. And we also had analysis and processing of measured data.3. Based on the analysis and processing of test data, lithium battery charged state of(SOC) dynamic prediction Map model was set up under the condition of high rate discharge. The accuracy of the Map model was verified by simulation.4. Lithium battery SOC dynamic prediction model and the drive motor torque control model were obtained by using drive motor optimum efficiency curve and discharge efficiency curve. Taking the highest efficiency of lithium battery discharge process as thegoal, energy management control strategy based on the highest battery discharge efficiency was developed by adjusting the target control model parameters of battery and drive motor.On the above basis, we established threshold control and energy control strategy based on rules and explained the design principle and realization method of the strategy. Finally the evaluation method of energy management control strategy was put forward.5. EV model was built on the joint simulation platform of Matlab/Simulink and Matlab/Advisor and the energy management strategy being used in the vehicle model was simulated, which can get drive motor limit point that having both better battery life and better dynamic performance.6. The correctness and feasibility of proposed energy management control strategy were verified through the simulation of a certain type of blade electric MPV’s lithium battery discharge process under cyclic conditions with battery testing system and through comparing the battery life before and after the making energy control strategy of this topic.Finally the research contents of this paper were summarized and the research direction in the future was prospected. |
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