Impedance spectra classification for determining the state of charge ona lithium iron phosphate cell using a support vector machine

[摘要] An alternative method for determining the state of charge (SOC) on lithiumiron phosphate cells by impedance spectra classification is given. Methodsbased on the electric equivalent circuit diagram (ECD), such as the KalmanFilter, the extended Kalman Filter and the state space observer, forinstance, have reached their limits for this cell chemistry. The new methodresigns on the open circuit voltage curve and the parameters for the electricECD. Impedance spectra classification is implemented by a Support VectorMachine (SVM). The classes for the SVM-algorithm are represented by all theimpedance spectra that correspond to the SOC (the SOC classes) for definedtemperature and aging states. A divide and conquer based search algorithm ona binary search tree makes it possible to grade measured impedances using theSVM method. Statistical analysis is used to verify the concept by gradingevery single impedance from each impedance spectrum corresponding to the SOCby class with different magnitudes of charged error.

[学科分类] 电子、光学、磁材料