Research On Stratified Equilibrium Control Strategy For Electric Vehicle Power Lithium Battery

With the energy crisis and environmental degradation,electric vehicles have quickly appeared in people's lives with their superior performance.As the main source of power for electric vehicles,lithium batteries play a decisive role in the development of electric vehicles.However,the inconsistency of the lithium battery pack causes an imbalance in the use of the battery pack,which limits the application of electric vehicles.Therefore,the equalization control technology is a difficult and important issue for electric vehicles.In this paper,the research and analysis of the battery pack equalization control strategy are carried out.This article analyzes the causes of battery inconsistencies and studies the equilibrium variables at this stage.The current research status of equalization technology is compared and analyzed.A hierarchical equalization control strategy is proposed,and the battery is divided into a bottom module and a top module.The topology structure of the equalization circuit of the bottom module is based on the improved structure of the Buck-Boost circuit,which reduces the number of switches and saves costs.An equalization control strategy based on battery SOC is proposed based on the underlying equalization circuit.According to the energy status of the individual cells in the module,the equalization strategy takes the average value of the battery's SOC as a reference to control the opening and closing of the switches in the equalization circuit and the direction of energy transfer.The duty cycle algorithm of the switch is used in the strategy.Control the process of energy transfer.The top-level balanced topology is based on the structure of a flyback transformer.Thecharacteristic of this equalization circuit is that the energy of the single cell and the battery pack can be double-transferred,that is,the battery energy can be transferred to the battery pack or the battery pack energy can be transferred to a single unit.Body battery.A top-level equalization strategy based on model predictive control(MPC)is proposed based on the top-level circuit to improve the control speed and accuracy of the top-level equalization.After researching the equalization strategy,MATLAB software was used to simulate and verify the bottom equilibrium control strategy and the top equilibrium control strategy.In the design of the simulation experiment,a comparative simulation experiment of the traditional equalization control strategy is added.The simulation experiment proves that the equalization strategy in this paper has higher equalization speed and shorter equalization time than the traditional equalization strategy.Finally,an experimental platform is built on the basis of simulation to further verify the effectiveness of the equilibrium control strategy in this paper.The experiments show that the equilibrium control strategy designed in this paper has a good effect on the balance of the entire battery pack,and can ultimately improve the inconsistency of the battery pack.Performance,make the batteries tend to be consistent,improve the performance of the battery pack and extend the battery life.