Characterization of a 5 kW Solid Oxide Fuel Cell Stack Using Power Electronic Excitation

Fuel cells have attracted great interest as a means of clean, efficient conversion of chemical to electrical energy. This paper demonstrates the identification of both non-parametric and lumped circuit models of our stack in response to a test signal introduced by control of a power electronic circuit. This technique could be implemented on-line for continuous condition assessment of the stack, as it delivers power. The results show typical data from the stack, comparison of model and measured data, and whole-stack impedance spectroscopy results using a power electronic system to provide excitation. Run-time excitation currents for the spectroscopy measurement are generated by a hybrid power system controlling the flow of power from the fuel cell and a secondary power source to a fixed resistive load. The hybrid power system generates small-signal currents at the fuel cell terminals while the load current itself is largely unaffected by the impedance spectroscopy measurement.