Research On Active Equalization Technology Of Power Battery Pack Based On Energy Transfer Path

Power battery pack,as the core energy source of electric vehicle,affects the overall performance of the vehicle.Due to the differences in manufacturing processes and operating conditions,the power battery pack will produce inconsistencies,which can lead to battery aging and performance decline at least,or thermal runaway and safety problems at worst.Balancing technology can effectively improve the battery inconsistency,improve the performance and safety characteristics of the battery group,and improve the service life of the power battery pack.Aiming at the inconsistency problem of power battery pack,based on the current research on main equalization technology,the thesis proposes the design method of active equalization circuit guided by energy transfer path evaluation and the equalization control strategy of fuzzy neural network based on optimization criterion of process selection.The specific research contents are as follows:1.The structure,advantages and disadvantages of the existing equalization circuit are studied and analyzed.An evaluation method based on the principle of energy transfer path is proposed.The design method of equalization circuit is considered from three aspects of energy transfer form,energy transfer path and energy transfer efficiency.Combining Loop Equalization Circuit based on Inductance(LECI)and Dual Inductance Equalization Circuit(DIEC),a novel active Equalization Circuit——Double Loop Equalization Circuit based on Inductance(DLECI)is proposed.By employing the energy transfer path evaluation method,the index of this circuit and the traditional circuit are calculated and compared.2.A fuzzy neural network equalization control strategy based on process selection optimization criterion is proposed.On the basis of analyzing the advantages and disadvantages of different equalization criteria,the State of Charge(SOC)is selected as the process criterion parameter of the equalization strategy.Several indexes of battery pack inconsistency are summarized and described.According to the structure of equalization circuit in this paper,the maximum difference value is selected as the starting criterion index of equalization strategy.An equalization control algorithm based on fuzzy neural network is designed to control the equalization circuit.Based on the characteristics of the battery,the algorithm uses the fuzzy neural network controller to adjust and control the equalization current to improve the equalization performance.3.The differential algorithm is used to control the equalization circuit under the condition of different battery pack charges.The DLECI is compared with the classical multi-inductance equalization circuit,LECI and DIEC,and the simulation experiments are carried out to further verify the energy transfer path evaluation method.The results show that the energy transfer path evaluation method can effectively distinguish and evaluate the effects of different equalization circuits under the four initial conditions,and the designed DLECI has the best equalization performance.The simulation experiment was carried out by using fuzzy neural network algorithm to control DLECI under three states of battery pack charging,idling and discharging.The results show that the equalization control strategy proposed in this paper can effectively improve the battery pack charge inconsistency.