The dynamic impedance modeling and simulation analysis of lithium battery cell in micro power grid

The lithium battery cell model plays a key role in research of high precision micro grid energy storage system. Taking lithium battery cell as the research object, combined with the equivalent circuit method, second-order RC equivalent circuit model which is based on dynamic impedance is established. According to the electric relationship model, SOC is viewed as state variables, OCV-SOC curve is obtained by the HPPC experiment, battery model parameters is identified by using exponential curve fitting based least squares, then get the function relation between parameter values and SOC. Finally, MATLAB/Simulink simulation of the model is used to verify the accuracy of model. Results show that second-order RC equivalent circuit model is of high precision, dynamic impedance can track the change of SOC and accurately reflect the external characteristic of the lithium battery energy storage system, these results are of great significance in micro power grid simulation and research.