An Online Battery Impedance Measurement Method With a Module‐Integrated Partial‐Power Converter

ABSTRACT

Electrochemical impedance spectrum (EIS) is a powerful tool to extract the internal information of batteries. Online impedance measurement is essential for EIS‐based battery state estimation and fault diagnosis. Existing measurement methods either interfere with the normal operation of the system or only apply to limited conditions. This paper proposes a novel impedance measurement method using a partial‐power converter, where the excitation is injected in a complementary manner. The method does not interfere with the system output and applies to light‐load or even no‐load conditions. Therefore, both online and offline real‐time impedance measurement can be realized with the proposed method, making it promising for continuous in situ battery state estimation. Moreover, the batteries can be balanced with the proposed partial‐power converter, eliminating the need for a conventional equalizer. A battery module with four commercial 18650 lithium‐ion batteries is built up to verify the proposed method. Compared with measurements from an electrochemical workstation, the magnitude and phase errors of the measured impedance are less than 1 mΩ and 1°, respectively.