Multi-Frequency Signal Synthesis for Accurate Fuel Cell Impedance Estimation

Electrochemical Impedance Spectroscopy (EIS) has gained popularity in its application to the diagnostics the fuel cells. However, traditional EIS takes a significant amount of time rendering it unsuitable for real-time diagnostics. Multi-frequency perturbation signals have been proposed to address this challenge. This however introduces new concerns surrounding the accuracy of the resulting impedance measurement. This work addresses some of the challenges with fuel cell multi-frequency impedance spectroscopy such as measurement accuracy, by first detailing some of the related problems and defining an optimised signal synthesis formulation. The proposed approach is validated in simulation and compared to the popular exponential frequency distribution approach using the appropriately defined error metric. It is shown that the proposed perturbation signal synthesis is more robust to nonlinearities and noise and as a result, offers improved impedance measurement.