THE STATE OF CHARGE ESTIMATION FOR LITHIUM BATTERY AT DYNAMIC TEMPERATURE

• Main Authors: Jia-Xuan Li, 李珈瑄
• Other Authors: Chung-Chun Kung
• Format: Others
• Language: en_US
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/45451026436219048159

碩士 === 大同大學 === 電機工程學系(所) === 104 === In thesis, we will consider the relationship between state of charge (SOC) and temperature effect of lithium battery. The batteries are tested at 10℃~ 45℃. A first-order RC model is adopted as the equivalent circuit model (ECM) for the lithium battery. We will apply direct current internal resistance (DCIR) test to obtain the relationship between the parameters of the ECM and the SOC at 10℃~ 45℃ for the lithium battery. Besides, we will apply open circuit voltage (OCV) test to obtain the relationship of OCV with SOC. Polynomial function will be adopted to build the models of the parameters and the model of OCV for the ECM at different operation temperatures. Then, we will apply the least-squares method to find the optimum polynomial models for the above mentioned relationships. According to experimental results, it is seen that the SOC only has little influence on the internal resistance (R_s) value of the ECM. In other words, the internal resistance remains a constant value for different values of SOC. In thesis, we will adopt the internal resistance as a reference factor. By the terminal voltage and the input/output current, we can obtain the internal resistance value. Then we can determine the surface temperatures of the battery by the internal resistance. And hence, we can choose the models of the parameters and the model of OCV of the ECM corresponding to the surface temperature. Finally, based on the model of the lithium battery, an adaptive extended Kalman filter (AEKF) will be employed to estimate the SOC. From the simulation results, it is seen that the proposed method can estimate the SOC with high accuracy.