Research On The Control Strategy Of Electric Vehicle Battery Pack Equilibrium

Due to factors such as production,use,and storage environment,the power battery pack of electric vehicles will cause inconsistency between the battery power of the monomers.The impact is manifested in that during charging and discharging,some batteries are significantly different from other battery cells.The condition of stopping operation makes the battery pack stop charging and discharging,so that the capacity utilization rate is reduced.The battery balancing module monitors the battery pack power state changes in real time,and distributes the energy in the battery again through the battery balancing control system to reduce the power of the monomer with more power,and the battery with less power supplements the power to make the battery The amount of electricity between the bodies tends to be consistent,and the capacity utilization rate is improved.This paper starts from the analysis of the inconsistency of the power battery pack,selects the balance circuit of the battery capacity,proposes a balanced control strategy,and builds a simulation model to verify the control strategy.The specific research contents are as follows:First,it analyzes the causes of power inconsistency in power lithium battery packs,and summarizes the measures to improve battery inconsistencies according to the causes.It explains the effects of power inconsistency on battery pack operating voltage,open circuit voltage,SOC and other parameters.Control variables of the battery pack charge equalization phase and the parking charge phase.Secondly,the design requirements of the balanced circuit structure are put forward from four aspects: the balanced efficiency,the flexibility,the complexity and the economy of the balanced circuit.The existing balanced control circuit structure is compared and analyzed,and the flyback transformer structure is selected as the battery power balance circuit,and the working process of the power balance circuit is determined.Then the parameters of the circuit are calculated,and the control model of the equalization system is built in Matlab / Simulink environment.Finally,a control strategy based on particle swarm optimization algorithm is proposed,and the effectiveness of the equilibrium strategy is verified by simulation using the established equilibrium model.Combined with the actual working conditions,two control strategies of battery pack charge equalization and parking balance were formulated.At the same time,the voltage range and the battery charge and discharge cut-off voltage were set as the basis for judging whether the battery pack equalization control system works.By collecting the status information of the battery pack and battery cells,the amount of power to be balanced is calculated,and the balanced path is optimized.After each equalization is completed,the battery cell voltage range and SOC variance are calculated separately,and the inconsistency changes of the cells in the equalization are compared.The effectiveness of the proposed equilibrium strategy is proved.