Virtual Admittance Based Switch Fault Detection for Hybrid UAVs

Unmanned aerial vehicles (UAVs) are widely used for various applications, such as military surveillance and reconnaissance; delivery of packages; monitoring of plants and buildings; and search and rescue. Besides basic battery-electric propulsion, in order to improve range and endurance, hybrid electric propulsion systems based on combinations of batteries, fuel cells, solar cells, and ultracapacitors are increasingly being applied to these UAVs. For small- and medium-scale UAVs, the solar and fuel cell converters have non-isolated DC-DC converters that include a high-frequency switching device. In this paper, a novel switch fault detection technique based on virtual admittance is proposed for DC-DC converters. A fault index function is formulated based on the virtual admittance to minimize potential influence by highly dynamic load change while reducing computation complexity to implement the technique in cost-effective UAVs. The proposed technique has been verified by simulations and experiments to validate the feasibility of the approach.