Hybrid Pseudorandom Sequence for Broadband Impedance Measurements of Lithium-Ion Batteries

Broadband battery impedance spectroscopy brings valuable information that facilitates states estimation and fault diagnosis, which are of extensive research interests at present. Pseudorandom sequence (PRS) provides a promising tool for realizing online battery impedance measurements, yet it suffers from an insufficient signal-to-noise ratio (SNR). Motivated by this, this article proposes a novel hybrid pseudorandom sequence (HPRS) to boost the signal power in the low-frequency region, where the measurement data are exceptionally robust against noise corruption. The disturbances are further suppressed by applying a specially designed adaptive bilateral impedance filter (ABIF), which considers signal power content and impedance measurements' distribution enabling a nearly unbiased result. The feasibility of the proposed HPRS signal is verified experimentally by comparing it with the typical PRS signal and step signal. The results suggest superior broadband impedance measurements' accuracy and robustness under different ambient temperatures and state of charges (SOCs), and the maximum normalized root-mean-square error (NRMSE) is limited to 0.77%.