基于EIS的锂电池阻抗模型研究
发布时间：2018-10-12 20:04
【摘要】：目前,虽然二次电池的检测技术与设备在精度上较以往有了很大提高,但受设备成本高、检测算法复杂等因素的限制,在一般的实际工程中往往还是沿用着比较落后的电池检测方法。针对这种情况,本文以磷酸铁锂电池的电化学阻抗谱(EIS)为基础,重点研究了电池阻抗模型在低频区简化与建立的问题,并对模型的正确性与应用性进行了仿真验证与探讨,为实际工程中电池性能的检测提供了一种比较简便并具有一定可行性的理论方法。在模型建立方面,本文基于磷酸铁锂电池的EIS,通过多次拟合对比与修正,建立了三阶RC电路作为电池在低频区的简化阻抗模型。分析发现,在电池正极界面上存在固体电解质膜(SEI),其阻抗响应在EIS全频带内没有表现出来,而在低频区模型简化后得以体现。深入研究了SEI形成机理与阻抗特性后,将其对应等效元件加入模型进行修正。修正后的模型经过拟合验证,在低频区与全频带的阻抗响应都能与EIS谱图很好的吻合,说明所建模型在阻抗响应方面的正确性。根据所建立的等效模型进行了电池放电特性的仿真验证工作。根据三阶RC电路理论,对电路模型中各参数进行了辨识,建立了各元件参数与电池SOC之间的函数关系。在此基础上,利用Simulink仿真平台搭建了锂离子电池的仿真模型,并进行了恒流放电和周期脉冲放电两种工况下的仿真验证。结果发现两种情况下的误差都主要集中放电开始与结束阶段,从误差数值来看,所建立的简化模型是能在直流或者低频下较好的模拟电池的充放电特性。在模型的应用性方面,结合扩展卡尔曼滤波(EKF)进行了对电池SOC估算的工作。根据所建模型参数辨识关系建立了系统的状态方程、观测方程以及估算递推过程,然后用Ah法下电流计算出的SOC值作为理论真实值,在Matlab中进行了周期脉冲放电情况下对SOC估计的仿真验证。结果表明,对SOC值的估计误差主要集中在放电结束阶段。从总体来看,所建模型对SOC的估计精度能够满足一般的工程应用要求。以上研究和验证工作表明,在EIS低频区简化后的电池阻抗模型能够较好的模拟电池的动态特性,并且具有一定的应用性。这种方法由于对设备要求不高,处理过程比较简单易行,因此将其应用于实际的工程中具有一定可行性。
[Abstract]:At present, although the accuracy of the detection technology and equipment of secondary battery is much higher than before, it is limited by such factors as high equipment cost and complex detection algorithm. In general, the actual engineering is often followed by relatively backward battery detection methods. In this paper, based on the electrochemical impedance spectrum (EIS) of lithium iron phosphate battery, the simplification and establishment of the impedance model in the low frequency region are studied, and the correctness and application of the model are verified and discussed. It provides a simple and feasible theoretical method for battery performance detection in practical engineering. In the aspect of model establishment, EIS, based on lithium iron phosphate battery is used as the simplified impedance model of the battery in low frequency region by several fitting comparison and correction, and the third order RC circuit is used as the simplified impedance model of the battery in the low frequency region. It is found that the impedance response of solid electrolyte membrane (SEI), on the cathode interface of the battery does not show in the whole frequency band of EIS, but is reflected in the simplified model in the low frequency region. The formation mechanism and impedance characteristics of SEI were studied, and the corresponding equivalent elements were added to the model to modify the model. The modified model is verified by fitting, and the impedance response in the low frequency region and the whole frequency band is in good agreement with the EIS spectrum, which shows the correctness of the model in impedance response. Based on the established equivalent model, the simulation of the discharge characteristics of the battery is carried out. According to the third-order RC circuit theory, the parameters in the circuit model are identified and the functional relationship between the component parameters and the battery SOC is established. On this basis, the simulation model of lithium ion battery is built by using the Simulink simulation platform, and the simulation results of constant current discharge and periodic pulse discharge are carried out. The results show that the errors in both cases are mainly concentrated at the beginning and the end of discharge. From the error value, the simplified model can simulate the charge-discharge characteristics of the battery at DC or low frequency. In the application of the model, the extended Kalman filter (EKF) is used to estimate the SOC of the battery. According to the model parameter identification relation, the state equation, the observation equation and the estimation process of the system are established. Then the SOC value calculated by the Ah method is used as the theoretical real value. The simulation of SOC estimation in the case of periodic pulse discharge is carried out in Matlab. The results show that the estimation error of SOC is mainly at the end of discharge. In general, the SOC estimation accuracy of the model can meet the general engineering application requirements. The results show that the simplified impedance model in the low frequency region of EIS can simulate the dynamic characteristics of the battery well and has certain application. It is feasible to apply this method to practical engineering because of its low requirement for equipment and simple and easy to deal with.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912
本文编号：2267429
[Abstract]:At present, although the accuracy of the detection technology and equipment of secondary battery is much higher than before, it is limited by such factors as high equipment cost and complex detection algorithm. In general, the actual engineering is often followed by relatively backward battery detection methods. In this paper, based on the electrochemical impedance spectrum (EIS) of lithium iron phosphate battery, the simplification and establishment of the impedance model in the low frequency region are studied, and the correctness and application of the model are verified and discussed. It provides a simple and feasible theoretical method for battery performance detection in practical engineering. In the aspect of model establishment, EIS, based on lithium iron phosphate battery is used as the simplified impedance model of the battery in low frequency region by several fitting comparison and correction, and the third order RC circuit is used as the simplified impedance model of the battery in the low frequency region. It is found that the impedance response of solid electrolyte membrane (SEI), on the cathode interface of the battery does not show in the whole frequency band of EIS, but is reflected in the simplified model in the low frequency region. The formation mechanism and impedance characteristics of SEI were studied, and the corresponding equivalent elements were added to the model to modify the model. The modified model is verified by fitting, and the impedance response in the low frequency region and the whole frequency band is in good agreement with the EIS spectrum, which shows the correctness of the model in impedance response. Based on the established equivalent model, the simulation of the discharge characteristics of the battery is carried out. According to the third-order RC circuit theory, the parameters in the circuit model are identified and the functional relationship between the component parameters and the battery SOC is established. On this basis, the simulation model of lithium ion battery is built by using the Simulink simulation platform, and the simulation results of constant current discharge and periodic pulse discharge are carried out. The results show that the errors in both cases are mainly concentrated at the beginning and the end of discharge. From the error value, the simplified model can simulate the charge-discharge characteristics of the battery at DC or low frequency. In the application of the model, the extended Kalman filter (EKF) is used to estimate the SOC of the battery. According to the model parameter identification relation, the state equation, the observation equation and the estimation process of the system are established. Then the SOC value calculated by the Ah method is used as the theoretical real value. The simulation of SOC estimation in the case of periodic pulse discharge is carried out in Matlab. The results show that the estimation error of SOC is mainly at the end of discharge. In general, the SOC estimation accuracy of the model can meet the general engineering application requirements. The results show that the simplified impedance model in the low frequency region of EIS can simulate the dynamic characteristics of the battery well and has certain application. It is feasible to apply this method to practical engineering because of its low requirement for equipment and simple and easy to deal with.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912
【参考文献】
相关硕士学位论文 前1条
1 胡杰;锂离子电池正极材料LiFePO_4的合成和电化学性能研究[D];重庆大学;2005年
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