High Frequency Online Battery Impedance Measurement Method Using Voltage and Current Ripples Generated by DC-DC Converter

摘要

This paper presents an online battery complex impedance measurement method at high frequency values by utilizing the battery voltage and current switching ripple information generated by the DC-DC power converter. First, perturbation based online battery impedance measurement methods from the literature are reviewed and discussed. The previously presented perturbation based methods are only suitable for impedance measurement within a frequency range much lower than the switching frequency of converter and they affect the normal operation of the system. The presented high frequency complex impedance measurement method in this paper utilizes the inherent switching characteristics of DC-DC converter for impedance measurement without having the need to add small perturbation signal to the system, which eliminates the aforementioned frequency range limitation and perturbation drawback. The battery voltage and current ripple components are extracted by using FFT analysis and then used to calculate the battery complex impedance values at the switching frequency. By sweeping the switching frequency values of the DC-DC converter, the battery impedance values at different high frequency values can be obtained. The method is evaluated using results obtained from a laboratory proof-of-concept (POC) prototype.