基于EIS的鋰電池阻抗模型研究
發(fā)布時間：2018-10-12 20:04
【摘要】：目前,雖然二次電池的檢測技術與設備在精度上較以往有了很大提高,但受設備成本高、檢測算法復雜等因素的限制,在一般的實際工程中往往還是沿用著比較落后的電池檢測方法。針對這種情況,本文以磷酸鐵鋰電池的電化學阻抗譜(EIS)為基礎,重點研究了電池阻抗模型在低頻區(qū)簡化與建立的問題,并對模型的正確性與應用性進行了仿真驗證與探討,為實際工程中電池性能的檢測提供了一種比較簡便并具有一定可行性的理論方法。在模型建立方面,本文基于磷酸鐵鋰電池的EIS,通過多次擬合對比與修正,建立了三階RC電路作為電池在低頻區(qū)的簡化阻抗模型。分析發(fā)現(xiàn),在電池正極界面上存在固體電解質(zhì)膜(SEI),其阻抗響應在EIS全頻帶內(nèi)沒有表現(xiàn)出來,而在低頻區(qū)模型簡化后得以體現(xiàn)。深入研究了SEI形成機理與阻抗特性后,將其對應等效元件加入模型進行修正。修正后的模型經(jīng)過擬合驗證,在低頻區(qū)與全頻帶的阻抗響應都能與EIS譜圖很好的吻合,說明所建模型在阻抗響應方面的正確性。根據(jù)所建立的等效模型進行了電池放電特性的仿真驗證工作。根據(jù)三階RC電路理論,對電路模型中各參數(shù)進行了辨識,建立了各元件參數(shù)與電池SOC之間的函數(shù)關系。在此基礎上,利用Simulink仿真平臺搭建了鋰離子電池的仿真模型,并進行了恒流放電和周期脈沖放電兩種工況下的仿真驗證。結果發(fā)現(xiàn)兩種情況下的誤差都主要集中放電開始與結束階段,從誤差數(shù)值來看,所建立的簡化模型是能在直流或者低頻下較好的模擬電池的充放電特性。在模型的應用性方面,結合擴展卡爾曼濾波(EKF)進行了對電池SOC估算的工作。根據(jù)所建模型參數(shù)辨識關系建立了系統(tǒng)的狀態(tài)方程、觀測方程以及估算遞推過程,然后用Ah法下電流計算出的SOC值作為理論真實值,在Matlab中進行了周期脈沖放電情況下對SOC估計的仿真驗證。結果表明,對SOC值的估計誤差主要集中在放電結束階段。從總體來看,所建模型對SOC的估計精度能夠滿足一般的工程應用要求。以上研究和驗證工作表明,在EIS低頻區(qū)簡化后的電池阻抗模型能夠較好的模擬電池的動態(tài)特性,并且具有一定的應用性。這種方法由于對設備要求不高,處理過程比較簡單易行,因此將其應用于實際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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM912
本文編號：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.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM912
【參考文獻】
相關碩士學位論文 前1條
1 胡杰;鋰離子電池正極材料LiFePO_4的合成和電化學性能研究[D];重慶大學;2005年
，本文編號：2267429
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