Dynamic EIS of fuel cells under transient operating conditions for fault detection

This study investigates the impedance behavior of fuel cells under varying current conditions, with the aim of developing and evaluating a dynamic EIS-based fault detection methodology. Stationary Electrochemical Impedance Spectroscopy measurements were first carried out under controlled conditions to characterize the dependence of impedance on current. Based on Equivalent Circuit Models and polynomial approximations, an experimental current-dependent impedance model was established to assess the validity of impedance measurements under dynamic operating conditions. To compute impedance in this non-stationary regime, a dedicated signal processing algorithm was developed. The algorithm compensates for drift effects induced by non-stationarity and enables impedance estimation over short time windows, without requiring the control system to be held at a stationary operating point. Finally, representative driving cycles were applied to identify impedance spectra under dynamic conditions using the proposed model. The results are promising and confirm the relevance of the developed approach.