Research On Active Equilibrium System Of Electric Vehicle Power Battery Pack

At present,as the power battery electric vehicle power sources system has been one of main technical bottlenecks restricting electric cars,with the constant improvement of the voltage and power performance of vehicle,had to series to use a combination of a large number of monomer battery,due to the constant with the increase of number of circulation work in each monomer battery capacity,voltage and internal resistance,if appear this kind of phenomenon will make the battery capacity utilization.This paper takes ternary lithium battery as the research object and designs the balanced management system of power battery pack,including the following work contents:(1)Analysis compared the several common battery model,chose to accurately simulate the second-order Thevenin equivalent model of battery external characteristic,on the basis of the internal resistance of the ternary lithium batteries,the terminal voltage,open circuit voltage external characteristic experiment analysis,and to establish the equivalent model of the off-line parameter analysis,is verified by charge and discharge conditions of the accuracy of the Matlab/Simulink model(2)Based on the fact that the current in the equalization circuit has direction,the common lithium battery equalization scheme is analyzed by using directed graph,and a multi-layer non-energy equalization topology is proposed by combining buck-boost converter and flyback DC/DC,and the working modes in the equalization circuit are analyzed in detail.By comparing the advantages and disadvantages of different equilibrium variables,the battery SOC is selected as the equilibrium variable,and the equilibrium strategy of mean-difference value is adopted.The energy efficiency is optimized by using the designed fuzzy controller to dynamically adjust the balance current.The Matlab/Simulink model was built and compared with the traditional buck-boost equalization structure.The final results show that the proposed equalization scheme can effectively improve the equalization speed and energy utilization efficiency.(3)The hardware and software of the proposed battery equalization scheme are designed.MC9SXDP512 is used as the main control chip,AD7280 A is used as the voltage and temperature acquisition chip,and ACS712 is used as the current acquisition chip.The distributed structure is used to design the hardware of eachfunctional module of the equalization system.Code Warrior development environment is adopted,and software program design is carried out for each module.Real-time monitoring of battery pack is realized through Lab VIEW upper computer based on development.(4)The balance main control module PCB was designed,and the test and experimental platform was built.Six single batteries were used as the experimental battery pack.The balance experiment was carried out under the charge and discharge condition of 0.2c.