A dynamic electrochemical impedance spectroscopy extraction method for PEM water electrolyzers considering time resolution

Electrochemical impedance spectroscopy (EIS) is an efficient in-operando characterization tool for analyzing the internal processes of proton exchange membrane water electrolyzers (PEMWE). However, conventional EIS requires the system to operate under steady-state conditions, which limits its applicability in real-world systems. Dynamic EIS (DEIS) provides a potential approach to capture the variation of internal physical states caused by changes in operating conditions over time. However, existing impedance calculation methods, such as fast Fourier transform and wavelet transform-based approaches, are limited in their ability to analyse nonstationary signals across the entire frequency range. To address these limitations, this paper proposes a hybrid method that combines the advantages of several existing time–frequency and instantaneous feature extraction techniques to accurately obtain DEIS under dynamic conditions. This study segments the perturbation signals based on operating variations and applies adaptive processing to ensure accurate impedance extraction. Simulation and experimental verification under different input power profiles to a PEMWE are conducted in this work. The results demonstrate that the proposed hybrid method achieves a DEIS accuracy exceeding 96%, verifying its effectiveness for PEMWE applications and potential for other electrochemical devices.