| With the rapid development of the new energy industry,a large number of automotive lithium batteries will be retired,and the retired batteries can continue to be used in the next link.The cascade utilization of retired lithium batteries has become a key issue in current research.Active equalization technology is the key technology to solve the problem of battery pack,which is of great help to the use efficiency and safety performance of lithium battery pack.As there are many theoretical studies on active equalization of lithium battery pack,the foundation is relatively solid,but there are still many problems in the implementation of practical engineering application.In view of the lack of research on its control and strategy in practical application,the main research contents and conclusions are as follows.First,the current main active equilibrium topological circuit and the equilibrium control strategy are studied,several more research circuit and control strategy are analyzed,this paper analyzes the advantages and disadvantages of the current topology and application of balancing method,combed the this article main research content and structure,and then to retire the special difference of lithium batteries.Analyzed each monomer battery internal reasons and external reasons for the difference value,and studied the battery difference value of several characterization,using the method of literature and GB battery performance test was carried out on the pilot echelon-used lithium batteries detailed performance test experiment,verified the inconsistencies,and this problem is given to solve the main ways and methods.Secondly,studied the basic structure and working principle of the flyback type circuit,emphatically analyzes the flyback type circuit few increase the absorption of circuit in actual application,choose appropriate RC absorbing circuit and raises the bi-directional flyback type equalization circuit topology,the topological circuit are analyzed under CCM/DCM in the energy flow,determine the design parameters of each component concrete.Followed by the analysis of all kinds of balanced variable strategy characteristics,combined with the feature of battery OCV-SOC curve changes,according to battery periodically to distinguish the problem,I design a grouping type balance control strategy based on SVM,select voltage and SOC double variables as balanced,respectively formulate equilibrium index,introduce the SVM algorithm to accurate grouping of pilot using battery.Based on different variables,the equalization within and between groups was carried out,and time interval was added to optimize the voltage fluctuation during equalization.Simulation model of equalization control system was built to verify the effectiveness of the proposed equalization strategy.Thirdly,the step battery active equalization control system based on MC9S12XEP100 is designed,the main hardware circuit of the equalization system is introduced,the software communication between MCU and LTC3300 is analyzed,the software design process of the equalization control algorithm is described,and the PCB design of the equalization control board is completed.Finally,set up six section 18650 pilot echelon-used lithium batteries pack equilibrium system experimental platform.Equalization tests were carried out under the conditions of static,1A constant current charging and 1A constant current discharging.The testing system of communication signal integrity,the acquisition precision of voltage,current,and the balance board MOSFET driving waveforms and balanced current collection and the accuracy of the waveform.The test data of the equalization experiment obtained by using the battery testing and monitoring system show that the equalization efficiency of the proposed equalization strategy is more than 83%. |
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