Phase-shift-perturbation discrete SPS control strategy for DAB DC-DC converter-based embedded Li-ion batteries EIS measurement system

A phase-shift-perturbation discrete single-phase-shift (PSP-DSPS) control strategy is proposed for the power interface dc-dc converter of Li-ion battery to achieve accurate and real-time electrochemical impedance spectroscopy (EIS) measurement. This control is an embedded solution, utilizing the original sampling circuits and digital controller of the power interface dc-dc converter. It calculates the EIS by injecting an ac perturbation signal into battery’s constant current (CC) charging current, and measuring the charging current and the response of terminal voltage. The proposed PSP-DSPS control achieve CC charging by discretizing a preset dc phase-shift duty ratio D
dc
, and achieve real-time EIS measurement by introducing a perturbation phase-shift duty ratio d
ac
. Therefore, without PI regulator and corresponding compensation circuits, the proposed method overcome the signal attenuation caused by bandwidth limitations in traditional PI control. Experimental results show that the proposed approach can accurately measure the EIS in the range of 1Hz~1kHz within 8.48s, and the root mean square error of both magnitude and phase is limited to 0.71mΩ and 0.55deg, respectively.