| Abstract | Fast impedance measurement via complex Morlet wavelet transform (CMWT) offers a valuable way for real-time diagnosis and in-situ monitoring on electrochemical energy devices. However, it normally suffers from a dilemma: how to set CMWT parameters such as sampling duration Tp, sampling frequency fs, scale factor range A, central frequency fc, and band factor fb? Especially for a fast measurement of Warburg-like impedance spectra. Thus, optimal theories are needed in order to acquire Warburg-like impedance spectra rapidly under a required precision and a given frequency range. In this paper, the optimal rules for a fast impedance measurement are developed based on the uncertainty principle: 1) 2.5/fL ≤ Tp ≤ 3.0/fL; 2) fs ≥ 20fU; 3) 1.0/fc≤≤1.4/fc where fL and fU are the lower-limit and upper-limit frequencies of the impedance spectra, respectively. Subsequently, measurement errors are quantitatively evaluated for the reconstructed impedance spectra via CMWT algorithm. Through the derived optimal rules, a fast measurement with Tp = 28.0 s and fs = 20.0 kHz is implemented for Warburg-like impedance spectra from 0.1 Hz to 1.0 kHz and with the average errors of 0.7% and 2.6% for magnitude and phase, respectively. The developed method creates a higher possibility for real-time diagnosis and in-situ monitoring of electrochemical energy devices in electric vehicles (EVs). |
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