An Auxiliary Converter for Fuel Cell Stack EIS using a Switched-Capacitor Converter Interfaced Supercapacitor as a Bidirectional Energy Buffer

摘要

Electrochemical impedance spectroscopy (EIS) is a promising tool for characterizing fuel cells. It was traditionally only applied to single cell or short stacks at low-power levels but was recently brought to high-power stacks due to a growing interest in performing in situ EIS without dismantling the stack. Converter-based EIS provides attractive solutions for this purpose. In this paper, an auxiliary EIS converter solution using a bidirectional energy buffer module composed of a switched-capacitor converter (SCC) and a supercapacitor is proposed. The module is designed towards having a more compact auxiliary converter unit. The design of the proposed module is investigated in detail and a comprehensive guideline is provided considering the probable limitations imposed by high EIS frequencies on this solution. The proposed system helps with the compactness and miniaturization of the entire auxiliary EIS converter and eliminating the potential problems of electrolytic capacitors such as bulkiness and limited lifetime due to impact of ripples. The effectiveness of the developed system is verified by simulation results.