Simulation of second-order RC equivalent circuit model of lithium battery based on variable resistance and capacitance
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Simulation of second-order RC equivalent circuit model of lithium battery based on variable resistance and capacitance JI Yan-ju(嵇艳鞠), QIU Shi-lin(邱仕林), LI Gang(李刚) College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130061, China © Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract: With the rise of the electric vehicle industry, as the power source of electric vehicles, lithium battery has become a research hotspot. The state of charge (SOC) estimation and modelling of lithium battery are studied in this paper. The ampere-hour (Ah) integration method based on external characteristics is analyzed, and the open-circuit voltage (OCV) method is studied. The two methods are combined to estimate SOC. Considering the accuracy and complexity of the model, the second-order RC equivalent circuit model of lithium battery is selected. Pulse discharge and exponential fitting of lithium battery are used to obtain corresponding parameters. The simulation is carried out by using fixed resistance capacitance and variable resistance capacitor respectively. The accuracy of variable resistance and capacitance model is 2.9%, which verifies the validity of the proposed model. Key words: lithium battery; equivalent circuit model; parameter identification; SOC estimation Cite this article as: JI Yan-ju, QIU Shi-lin, LI Gang. Simulation of second-order RC equivalent circuit model of lithium battery based on variable resistance and capacitance [J]. Journal of Central South University, 2020, 27(9): 2606−2613. DOI: https://doi.org/10.1007/s11771-020-4485-9.
1 Introduction In recent years, with the increasing shortage of energy, energy conservation and environmental protection are promoted actively. The electric vehicle industry has achieved unprecedented development [1]. Lithium batteries have become the main energy source for electric vehicles by virtue of their superior performance [2]. The state of charge (SOC) of the battery is an important parameter for the residual energy of the reaction battery. Due to the charge and discharge characteristics of the battery, the SOC estimation during charging is much more difficult than the discharge period. Accurate and effective SOC estimation is an effective basis for battery charging and discharging strategies, and it is also the basis
for evaluating battery reliability. The battery model can reflect the state as a real battery [3], which is generally simplified by physical or mathematical methods based on the characteristics of the battery. Many classic models have been produced, such as thermal coupling model [4, 5], performance model [6, 7], and electrochemical model [8, 9]. The battery performance model is based on the external characteristics of the battery and the model is built according to the voltage and current of the battery. Because of simple modeling process, the performance model is widely used. The network of resistors and capacitors (RC) in series and parallel can describe the external characteristi
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