| It is inevitable to use the new energy vehicle because of the energy crisis and environmental problems. As the core component of new energy vehicles, Power battery is also the biggest bottleneck in the technology and costs of new energy automotive. At the present stage, the lithium-ion battery gradually becomes the first choice for the power supply of the electric vehicle for its high energy volume ratio,low self discharge rate, no memory effect and high safety performance, etc.The battery pack used on the new energy vehicle is composed of a plurality of cell monomers connected in a series to meet the requirements of voltage, power and driving range. However, there is a big difference between the battery pack and the cell battery. In the battery pack, the production and manufacturing of the battery are bound to be different, after a number of charge and discharge, this difference will be accumulated and expanded. As a result, the performance of the battery pack will be greatly reduced. For example, if one of one hundred batteries can be charged to 80%to the utmost extent, the same group of other batteries can only be charged to 80%,which leads to the power of the entire battery capacity can only reach 80% of the original state. Continuing charging will inevitably lead to over charge and the shortage of the battery life. In addition, due to the large capacity of the battery pack,the efficiency of traditional charging mode is low, and the charging time is long,which seriously hinders the promotion of the electric vehicle.Therefore, it is important and valuable for researching on charging method and equalizing charge.An equal charging scheme is proposed in this article.During the charging proces, the balance circuit is used to reduce the inequality of batteries,making sure that all batteries are fully charged. The main research contents include the following aspects:(1) Refer to the electric vehicle industry standards; analyze charging mode;understand the principle of coordinated charging. Study the battery charging process,charging curve and point out the causes of the polarization, the unbalanced phenomenon of battery and its influence on charging. Then summarizes the battery requirements and puts forward the charging indicator.(2) Two RC equivalent circuit model is chosen as the battery model, this paper puts forward a simple and effective method to acquire the corresponding relationship between the OCV and the SOC. Model parameters are obtained by HPPC experiments.Then establish the dynamic model of the battery and carries out the emulational verification.(3) Make a comparison and analysis of the advantages and disadvantages of various charging modes. Based on the theory of the best charging curve, the five-stage constant current charging method is selected to charge the battery. The charging current value of each phase is optimized by using the orthogonal experiment.(4) Study the existing energy consumption and non energy consumption balance topology. In order to meet the requirements of rapid equilibrium, this paper designs a parallel balanced topology, then evaluate the parameters of battery consistency.Choose the battery voltage as control variable; introduce the concept of average value and range to judge whether to open the equilibrium system; and design the balanced fuzzy controller.(5) Built the charging experiment platform,taking TTC200 as the hardware controller,write charge balance control strategy in Matlab/Simulink. Finally,verify the feasibility and effectivenes of the scheme. |
