Online Measurement of Battery Impedance Based on Second-Order Generalized Integrator and Equivalent Reactive Current Injection Technology

The electrochemical impedance is a powerful tool to characterize battery state, and online measurement of battery impedance has significant importance. In this letter, an online battery impedance measurement method based on second-order generalized integrator (SOGI) and equivalent reactive current injection technology is proposed. An equivalent reactive current is injected to battery, which does not consume energy theoretically, thus amplitude of the excitation current can be set with a large value, then the signal-to-noise ratio is high and no additional power supply is required for the current injection. The SOGI is used to extract the battery impedance, which can be digitized implementation by microcontroller unit. Thanks to the bandpass characteristics of SOGI-based filters, the voltage and current signals with the injected frequency are only extracted and this will result in high accuracy. By using SOGI-based filters replaces the classic low-pass filters, the measurement time is reduced and the filtering effect is improved. The proposed method is analyzed in detail, and the experiment results with different loads and different batteries and excitation signal frequencies are presented. The experimental results indicate that the proposed method is correct and effective.