Online estimation of the electrochemical impedance of polymer electrolyte membrane fuel cells using broad-band current excitation

• Published in: Journal of power sources 2018-11, Vol.405, p.150-161
• Main Authors: Ritzberger, D., Striednig, M., Simon, C., Hametner, C., Jakubek, S.
• Format: Article
• Language: English
• Subjects: Electrochemical impedance spectroscopy; Fault detection; Generalized total least squares; Online estimation; Polymer electrolyte fuel cell
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2018.08.082

In this work, an online algorithm to estimate the electrochemical impedance spectrum of polymer electrolyte membrane fuel cells (PEMFCs) is presented. The electrochemical impedance, constituting the linear dynamic relation between current and voltage, is described by a discrete time filter model. The unknown model parameters are estimated from streaming time domain data using a recursive algorithm based on the generalized total least squares (GTLS) technique. This allows for flexible noise assumptions, leading to unbiased parameter estimates in the presence of noisy current and voltage measurements. Therefore, the robustness of the proposed method is significantly increased. Broad-band current excitation signals are utilized as to sufficiently stimulate the fuel cell for the online parameter estimation. The model order is selected using Akaike's information criterion (AIC), leading to a parsimonious model. Equivalent circuits are automatically generated using Foster's method of analog circuit synthesis. The applicability and benefits of the proposed algorithm regarding fuel cell diagnostics are demonstrated using measurement data of a small scale single cell (5 cm2 active area) subjected to a broad-band excitation. •Electrochemical impedance spectrum is described by a discrete time domain model.•An online estimation algorithm is derived based on generalized total least squares.•Equivalent circuits are synthesized from the discrete time domain model.•Validation is done using experimental measurements from a 5 cm2 single cell.•Time resolved impedance information during transient operations are obtained.