| In order to reduce the energy consumption and carry out the green transportation,the research in new energy vehicles has been gradually attracted the attention at home and abroad.Among of them,power battery is the main energy of new energy vehicles,considering the safety and installation of rationality,and it is more often adopting the form of series and parallel to constitute the new energy vehicles systems.With the purpose of the modular designed more convenient,improving the compatibility of the use of new energy vehicle power battery pack,while taking into account the safety of the system,it is usually using series before the parallel way to enhance the power and allow the adoption of current demand.In this process,it may be due to the parallel voltage difference between the modules that a powerful current suddenly emerges,which affecting the system performance or even producing the safety issues.To solve the impact of parallel process current so as to achieve the safety of the battery in parallel,the essay carried out the following aspects of the study:(1)The characteristics of voltage and resistance change during the charging and discharging process were analyzed for the single cell,and the influence of the hysteresis voltage on the system was discussed.At the same time,the characteristics of the resistance of the battery during the charge and discharge are discussed,while the variation law of the resistance of the power battery is summarized.On the basis of the commonly used battery equivalent circuit model,the battery simplified circuit model considering the external factors is put forward.(2)By analyzing the parallel characteristics of the power battery and the design and operation steps of the safety circuit in the parallel process of the power battery pack,the parallel test of the 32650 lithium iron phosphate battery at different voltage levels and different voltage differences is carried out to the relationship between the voltage oscillation amplitude and the voltage level and the voltage difference.At the same time,the multi-group battery in different voltage and pressure under the parallel experiment get the power battery safety parallel order.(3)The voltage shock of the battery pack is analyzed,and the voltage oscillation of the parallel battery pack is modeled.The validity of the model is verified by experiments.Aiming at the voltage oscillation in parallel process,the basic idea of parallel control system of power battery pack is put forward,and the corresponding control system is designed.Through the above theoretical derivation and experimental test,it is found that the power battery pack will produce a large-scale high-voltage oscillation at different voltage levels and different differential pressure levels.According to them,it proposes the voltage oscillation amplitude and voltage level and the relationship between the hysteresis curve of the voltage difference,voltage variations polynomial and the parallel process of the proposed control strategy,which provide a theoretical and practical means of operation with a reference value set for the new energy vehicle power battery pack combination of safety and control.It will prove to have a certain engineering application significance. |
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