Multiconverter System Design for Fuel Cell Buffering and Diagnostics Under UAV Load Profiles

This paper presents a multisource, multiconverter power system for electrically propelled unmanned aerial vehicles (UAVs) with a focus on promoting fuel cell health. Linearized multiconverter system analysis and the two extra element theorem (2EET) inform a system design for fuel cell current buffering and integral diagnostics. Integral diagnostics is in situ impedance spectroscopy achieved by controlling the power system to superpose a frequency-swept excitation current at the fuel cell terminals. An experimental system demonstrates hybridization of a solid-oxide fuel cell (SOFC) with a lead-acid battery having suitable current buffering and integral diagnostics performance under UAV load profiles. Experimental behavior is demonstrated with an electrically emulated SOFC stack or “reference simulator.” Impedance spectroscopy data measured during run-time clearly indicate both degradation and recovery phenomena in the SOFC.