| With the further requirements of the state on carbon emissions,the development of new energy has become an effective way to reduce carbon emissions,and electric vehicles have become representatives of new energy vehicles with their zero-emission advantages.As the power source of electric vehicles,the performance parameters of lithium power batteries are directly related to the safety performance and power performance of the whole vehicle.Since the power system is generally composed of a large number of single batteries,each monomer has differences in characteristics under the influence of charging and discharging current,battery capacity and temperature,which will greatly shorten the service life of the battery pack.Therefore,it is particularly important to carry out active balanced management of power battery packs.Based on the Buck-Boost multilayer equalization circuit,this paper introduces top-layer three-winding flyback transformer equalization.The primary side winding can realize the time-sharing multiplexing between the two sub-battery packs and the entire battery pack,and the two secondary windings are connected to the two sub-battery packs on the top layer to realize the energy transfer between the two sub-batteries and the entire battery pack.The introduced three-winding flyback transformer equalization circuit can realize the energy transfer between the sub-battery pack and the battery pack,and between the sub-battery and the sub-battery pack.With the goal of equalization time,energy loss,and equalization efficiency,a balanced control strategy is formulated and simulated experiments are conducted.The hybrid multilayer equalization circuit topology is divided into top-level equalization and low-level equalization.The bottom level equalization adopts the Buck-Boost bi-directional equalization topology,and the top level equalization adopts the three-winding flyback transformer equalization topology.The comparison experiment is performed on the two equalization circuits of Buck-Boost multilayer equalization circuit and flyback transformer multilayer equalization circuit.In the equilibrium strategy,the underlying equilibrium takes the difference between the two batteries or battery pack SOC as the equilibrium opening condition,and when the absolute value of the difference is higher than the threshold,the equilibrium is turned on;The top-level equalization takes the difference between the means of each group of the two battery packs as the equilibrium opening condition,and the equilibrium mode is judged by the size of the difference.Top-level equalization mode 1: When the mean difference between the two battery packs is greater than the upper threshold value,the high-power battery pack transfers the power to the entire battery pack to achieve rapid discharge of the high-power battery pack.When the gap between the two battery packs decreases with the equilibrium to the upper threshold after,the equilibrium shifts to mode 2.Top-level equalization mode 2: When the mean difference between the two battery packs is between the upper and lower thresholds,the higher battery transfer the power to another battery pack to achieve the balance between the two battery packs.Hybrid multilayer active equalization circuit and two sets of control simulation experiments Buck-Boost equalization circuit and flyback transformer equalization circuit were built on the MATLAB/Simulink simulation platform.And design the corresponding equalization control strategy in the chart module under stateflow.Taking the 8-cell lithium iron phosphate battery as an example,the battery SOC is used as the equalization variable to compare the simulation data under three conditions: discharge equalization,static equalization,and charge equalization.The experiment shows that the balancing time of the hybrid multi-layer balancing circuit is reduced by 72% and41% respectively compared with the Buck-Boost balancing circuit and the flyback transformer balancing circuit,and the balancing speed is obviously improved.Compared with the flyback converter equalization circuit,the energy consumption is reduced by 67%,and the equalization loss is significantly reduced;Compared with the initial value of the battery pack,the post-equalization error is reduced by 94%,the variance is reduced by 99.7%,and the consistency of the battery pack is significantly improved.Synthesizing various types of data verifies the effectiveness of the hybrid multilayer active equalization circuit.Figure [45] Table [14] Reference [66]... |
