Online Broadband Battery Impedance Spectroscopy Using Current-Mode Boost Converter
Hossein Haji Abbasali, Shahin Jafarabadi Ashtiani
Abstract
In this paper an online method of broadband battery impedance spectroscopy is proposed in which the excitation signal is injected through the inner feedback loop of a DC/DC boost converter with average current-mode control (ACMC). By deriving the average state-space model of the conventional boost converter, it is shown that an open-loop converter exhibits a resonant frequency response in regards to the injected signal, whereas the compensated current loop in ACMC produces a controllable, flat-gain closed-loop transfer function that allows broadband current excitation signals to be injected into the battery without the distortion that is seen in the open-loop configuration. In the presented method, the converter is set to discharge the battery at a constant C-rate during impedance measurement while a broadband signal is superimposed onto the loop reference current. A low-dropout regulator is then used to filter out disturbances caused in the converter output. The proposed approach is experimentally implemented and a discrete-interval binary sequence signal is utilized to measure the impedance of two 18650 lithium-ion batteries in several arbitrary frequencies at once in the 0.1Hz-1kHz range. The measured spectra are validated by a commercial impedance analyzer.