电池管理系统SOC估算及均衡技术研究

发布时间：2018-06-26 21:41

本文选题：电池管理系统 + SOC估算　；参考：《中国矿业大学》2017年硕士论文

【摘要】：近年来,随着能源结构改变,国家大力发展电动汽车,动力电池作为电动汽车能量核心,现已成为制约电动汽车快速发展的瓶颈。优秀电池管理系统(Battery Management System,BMS)能够有效提高电池使用寿命、增加续航里程,给予使用者准确电池运行状态,包括电池荷电状态(State of Charge,SOC),电池均衡状态及基本电压电流参数。本文以三元锂电池作为研究对象,重点研究电池SOC估算优化设计及基于SOC实现电池均衡。本文对常规二阶RC等效电路进行优化设计,增加RC环节建立电池三阶RC等效电路模型,根据电池混合脉冲功率特性(Hybrid Pulse Power Characterization,HPPC)循环测试数据,结合电池SOC-OCV曲线,进行等效电路模型参数辨识。在MATLAB中分别搭建两种等效电路模型,基于HPPC测试数据,对两种等效电路模拟电池外特性进行仿真对比分析,仿真结果表明,三阶RC等效电路能够更加精确模拟电池外特性。基于所建立的等效电路模型,分析扩展卡尔曼滤波算法(Extended Kalman Filter,EKF)估算SOC原理。针对算法中反馈电压误差较大的缺点,引入模型修正因子优化EKF算法,从而降低SOC估算误差,最后采用HPPC测试数据对优化前后SOC估算结果进行仿真对比分析,仿真结果表明,优化后算法能够有效提高SOC估算准确度。针对常规均衡电路均衡效率差、控制复杂等问题,本文给出级联型均衡电路方案,该方案通过控制MOSFET开关状态改变电池充放电时间,实现不同电量电池的电量均衡,同时具有切除故障电池的功能。根据电路均衡原理给出该电路的均衡控制策略,在MATLAB仿真环境中,搭建锂电池均衡电路,以SOC一致性为控制目标,对电池组均衡及故障冗余进行仿真测试。仿真结果表明,该均衡电路及其控制策略能够有效实现电池SOC均衡控制,且电池出现故障时电池组仍可正常运行。为验证所提出理论的正确性和可行性,设计并搭建BMS硬件实验平台进行实验分析。实验平台采用飞思卡尔公司MC9S12XET256单片机做为主控芯片,TI公司BQ76PL536、LEM公司LA55-P电流传感器分别用于电池电压、电流采样。为保证电池安全可靠运行,分别设计MOSFET驱动保护电路及互锁保护电路。基于LabVIEW编写上位机软件,实现电池运行状态实时监控,并记录、存储电池组参数信息,便于后续处理分析。基于所搭建的硬件实验平台分别进行SOC估算实验和电池均衡实验。首先对电池分别进行DST和FUDS工况测试,同时估算电池SOC,对比电池容量仪测量结果和SOC估算曲线,验证所采用的优化EKF算法的有效性和准确性。以SOC一致性为控制目标,分别在放电、充电及故障状态进行电池均衡控制实验,对比分析各电池均衡曲线可知,该均衡电路和均衡控制策略能够有效实现电池SOC均衡及故障冗余功能。
[Abstract]:In recent years, with the change of energy structure, the country has made great efforts to develop electric vehicles. As the energy core of electric vehicles, power battery has become the bottleneck restricting the rapid development of electric vehicles. The Battery Management system (BMS) can effectively improve the battery life, increase the mileage of the battery, and give the user accurate battery running state, including the State of charge SOC (SOC), the battery equilibrium state and the basic voltage and current parameters. In this paper, ternary lithium battery is taken as the research object, and the optimization design of SOC estimation and the realization of battery equalization based on SOC are emphasized. In this paper, the conventional second-order RC equivalent circuit is optimized, and the third-order RC equivalent circuit model of battery is established by adding RC link. According to the cycle test data of Hybrid Pulse Power Characterization HPPC, the SOC-OCV curve is combined with the battery SOC-OCV curve. Parameter identification of equivalent circuit model is carried out. Two kinds of equivalent circuit models are built in MATLAB. Based on the HPPC test data, the simulation results show that the third-order RC equivalent circuit can simulate the external characteristics of the cell more accurately. Based on the established equivalent circuit model, the SOC estimation principle of extended Kalman filter (EKF) is analyzed. Aiming at the disadvantage of large feedback voltage error in the algorithm, the model correction factor is introduced to optimize the EKF algorithm to reduce the SOC estimation error. Finally, the SOC estimation results before and after optimization are compared and analyzed by HPPC test data. The optimized algorithm can effectively improve the accuracy of SOC estimation. Aiming at the problems of low equalization efficiency and complex control in conventional equalization circuit, a cascade equalization circuit scheme is presented in this paper. By controlling the switching state of MOSFET, the battery charge and discharge time can be changed to realize the battery power equalization with different quantities of electricity. At the same time, it has the function of removing faulty battery. According to the principle of circuit equalization, the equalization control strategy of the circuit is given. In MATLAB simulation environment, the equalization circuit of lithium battery is built, and the battery pack equalization and fault redundancy are simulated and tested with SOC consistency as the control target. The simulation results show that the equalization circuit and its control strategy can effectively realize the SOC equalization control of the battery, and the battery can still operate normally when the cell fails. In order to verify the correctness and feasibility of the proposed theory, a BMS hardware experimental platform is designed and built for experimental analysis. The experiment platform uses MC9S12XET256 single chip microcomputer of Freescale Company as the main control chip BQ76PL536LEM company LA55-P current sensor for battery voltage and current sampling respectively. In order to ensure the safe and reliable operation of the battery, the MOSFET drive protection circuit and the interlock protection circuit are designed respectively. Based on LabVIEW, the upper computer software is written to realize the real-time monitoring of the battery running state, and to record and store the parameter information of the battery pack, so as to facilitate the subsequent processing and analysis. Based on the hardware experiment platform, SOC estimation experiment and battery equalization experiment are carried out respectively. First, the battery was tested under DST and FUDS conditions, and the SOC of the battery was estimated at the same time. The validity and accuracy of the optimized EKF algorithm were verified by comparing the measured results of the battery capacity meter and the SOC estimation curve. Taking SOC consistency as the control target, the battery equalization control experiments are carried out in the discharge, charging and fault state respectively, and the comparison and analysis of each battery equalization curve can be seen. The equalization circuit and the equalization control strategy can effectively realize the battery SOC equalization and fault redundancy.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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