| With the surge in the number of new energy vehicles,the way out of decommissioned batteries on new energy vehicles has become the focus of attention from all walks of life.The power battery still has 70% of the capacity after it is decommissioned from the new energy vehicle.Using it in other mild areas to realize the cascade utilization of the power battery will not only alleviate the pressure of the power battery entering the recycling stage,but also give full play to the residual value of the power battery,improve its service life,reduce the cost,and help to promote the development and popularization of the electric vehicle industry.The most extensive application prospect of step-by-step utilization of decommissioned batteries is the field of energy storage.The key technologies and applications of step utilization of decommissioned batteries are studied in this paper.Based on the study of the internal structure and working principle of decommissioned battery,the charge and discharge characteristics of NCR18650 B battery under different conditions were studied and the influencing factors of the decommissioned battery were analyzed.On this basis,an experimental platform is established to analyze the basic performance of the decommissioned battery,and the specific parameters such as open-circuit voltage,residual capacity and total internal resistance of the decommissioned battery are obtained.it accords with the echelon reuse standard and briefly describes the analysis method of the health state of the decommissioned battery.The technology of screening and recombination of decommissioned batteries was studied in order to improve the reliability of screening and recombination of echelon utilization.In this study,the appearance of the decommissioned battery was initially screened,and then the polarization parameters were calculated with the help of the second-order RC equivalent circuit model in the 70%SOC state.The comprehensive evaluation index system was established by the combination of entropy weight method and grey correlation analysis method,and the comprehensive evaluation value was calculated to complete the sorting and reorganization between retired batteries.Then,aiming at the inconsistency of decommissioned battery,this paper introduces two-way active equalization based on Buck-Boost,takes SOC value as equalization index,analyzes its equalization circuit and algorithm,adopts the topology strategy of first intra-group equalization and then inter-group equalization,and builds the corresponding simulation model in Matlab 2019b/Simulink.Based on the analysis of the equilibrium results,it is concluded that the equalization strategy is effective,which can effectively reduce the SOC value by about 15% in the intra-group equalization process and 16.5% in the inter-group equalization process,which can effectively stabilize the difference of decommissioned batteries.Finally,a set of small retired battery energy storage system is designed with the selected decommissioned battery.First of all,through the overall structure design of the whole system,and then use the modular method to select the chip and design the circuit of each functional module,and integrate each module.Then,on the basis of hardware design,software programming is carried out to complete the whole system design.Finally,the experimental platform is set up under the existing conditions of the laboratory,and the system voltage is tested to ensure that the system can carry out the basic work,and then the battery state detection and passive equalization are tested.The experimental results show that the relative error of voltage acquisition accuracy is about 1%,and it can effectively charge about 70% of the energy and release 50% of the energy.And through passive equalization,the voltage difference in the charging process reduces the 57.61 m V,and the discharge process reduces the 210.53 m V,which proves that the design of the system is feasible and realizes the energy storage and passive equalization of the decommissioned battery. |
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