Impedance modelling and analysis of the fuel cell-supercapacitor hybrid power supply system for electrical propulsion-based aircraft

Power electric source composed of fuel cell (FC) and supercapacitor (SC) is regarded as an appealing onboard hybrid power supply system (HPSS) for electrical propulsion-based aircraft. However, with the ever-growing electrification of the aircraft, the type and number of the electrified sources and loads increase significantly, where a large number of onboard loads are constant power loads (CPL). As a consequence, the interconnected system tends to suffer from instability problem. This paper first establishes the impedance model of FC and SC, and corresponding simulation models were built to verify the accuracy of the impedance model. To clearly reveal the effective of the key parameters, sensitivity analysis is adopted to guide the optimization of the parameters, thus, a better distribution of power between FC and SC unit is achieved. Moreover, when connected to CPL, the influence of control parameters and the number of parallel FC-SC units on system stability is investigated. All the analyses are verified via simulation results eventually. The conclusions of this paper can serve as the basis for the stability analysis and parameters design of more complex aircraft power systems.