Power for Aircraft Emergencies: A Hybrid Proton-Exchange Membrane H2\/O2 Fuel Cell and Ultracapacitor System

In the context of aviation, this article looks at replacing a ram air turbine (RAT) with a hybrid proton-exchange membrane (PEM) hydrogen/oxygen (H₂/O₂) fuel cell and ultracapacitor system, starting from a theoretical perspective. The structure we propose has two static power converters: one associated with fuel cells and the other with ultracapacitors. The energy management principle presented (frequency sharing) enables two types of control. First, the converter associated with the fuel cell manages the voltage of the dc bus, and then the converter associated with the ultracapacitors controls the high-frequency currents. Second, the voltage of the dc bus is oppositely controlled by the ultracapacitor converter.