Design and control of isolated current-fed DC–DC converters for fuel cell stacks EIS incorporating wide-frequency-range of perturbations

Abstract

Electrochemical impedance spectroscopy (EIS) performed by power converters makes in situ diagnostics possible for fuel cell stacks (FCS) in end applications without displacing and dismantling the stack. Previously published solutions, however, fall short of adequately generating a wide frequency range of perturbations covering all internal information of an FCS. The practical challenges and limitations of achieving converter generated perturbations at various frequencies are revealed in this paper. The high-end frequencies are constrained by the converter control bandwidth, whereas the low-end ones may cause significant ripples on the converter output. To address these issues, this paper proposes the use of isolated current-fed DC–DC converters for the design of an FCS power converter considering the output characteristics of the FCS operating at desired conditions and incorporating wide-frequency-range of EIS perturbations. Moreover, the oscillations resulting from EIS operations are tackled by properly guiding them from the load side to a primary side energy storage. A fuel-cell-dedicated power conditioning converter capable of presenting a wide-range frequencies of EIS perturbations is thus achieved. A design case is presented, and its simulation and experimental results verify the effectiveness of the proposed solution.