Abstract: A power distribution system includes at least a ground power unit, an aerial vehicle, and a power station. The ground power unit is configured to convert an input AC power into DC power output, wherein the ground power unit includes at least a first bus, second bus, and a third bus, wherein the first bus is configured to operate at a first voltage level referenced to the third bus, and wherein the second bus is configured to operate at a second voltage level referenced to the third bus that is different from the first voltage level. The aerial vehicle may include a plurality of motor-generators coupled to a respective plurality of turbines, wherein the plurality of motor-generators may be configured to be energized by power received from a tether.

Abstract: Apparatus are disclosed that are configured to passively rotate a propeller blade from a first pitch angle to a second pitch angle. An example apparatus involves: (a) a rotor hub, (b) at least one dual-pitch support coupled to the rotor hub, wherein the dual-pitch support has a first surface, a second surface and a cavity defined there between, and (c) at least one propeller blade rotatably coupled to the rotor hub such that a blade root is disposed within the dual-pitch support's cavity, where the blade root's front face is positioned against the dual-pitch support's first surface in a first position and the blade root's back face is positioned against the dual-pitch support's second surface in a second position, and the propeller blade is oriented at a first pitch angle in the first position and is oriented at a second pitch angle in the second position.

Abstract: In an example embodiment, a system includes a plurality of drive units coupled to a plurality of propellers. Each drive unit includes a single motor/generator and a single motor controller, and the plurality of drive units includes a first drive-unit pair and a second drive-unit pair. The system also includes a high-voltage bus connecting the motor controllers in the first drive-unit pair to a tether, a low-voltage bus connecting the motor controllers in the second drive-unit pair to the tether, and an intermediate-voltage bus connecting the motor controllers of the first drive-unit pair in series with the motor controllers of the second drive-unit pair. The motor controllers in the first drive-unit pair are connected in parallel via the high-voltage bus and the intermediate-voltage bus, and the motor controllers in the second drive-unit pair are connected in parallel via the intermediate-voltage bus and the low-voltage bus.

Abstract: A power distribution system includes a bidirectional power converter, a battery, and a controller. The bidirectional power converter is operable to (i) convert AC power received at AC terminals to DC power at DC terminals and (ii) convert DC power received at the DC terminals to AC power at the AC terminals. The bidirectional power converter is disposed within a converter stack formed by a plurality of power converters having DC terminals that are coupled to each other in series. The battery is arranged to be selectively couplable to the DC terminals of the bidirectional power converter. The controller is configured to (i) determine that the DC voltage across the DC terminals of the bidirectional power converter is below a threshold voltage and (ii) couple the battery to the DC terminals of the bidirectional power converter based on the determination that the DC voltage is below the threshold voltage.

Abstract: Embodiments described herein may relate to power-line communication (PLC) systems that are suitable for high-voltage and electrically noisy applications. In one example system, PLC technology is used to carry data on at least one pair of conductors of a high-voltage (e.g., kilovolt) transmission line that is simultaneously used for power transmission. Further, in some instances, the transmission line may be part of a tether that connects an aerial vehicle to a ground station.

Abstract: Apparatus are disclosed that are configured to passively rotate a propeller blade from a first pitch angle to a second pitch angle. An example apparatus involves: (a) a rotor hub, (b) at least one dual-pitch support coupled to the rotor hub, wherein the dual-pitch support has a first surface, a second surface and a cavity defined there between, and (c) at least one propeller blade rotatably coupled to the rotor hub such that a blade root is disposed within the dual-pitch support's cavity, where the blade root's front face is positioned against the dual-pitch support's first surface in a first position and the blade root's back face is positioned against the dual-pitch support's second surface in a second position, and the propeller blade is oriented at a first pitch angle in the first position and is oriented at a second pitch angle in the second position.

Abstract: A motor control topology relevant to airborne wind turbines and a control process for such a motor control topology is disclosed herein.

Abstract: A motor control topology relevant to airborne wind turbines and a control process for such a motor control topology is disclosed herein. A system may include an aerial vehicle that may include a plurality of propellers, a plurality of drive units coupled to the plurality of propellers, and a tether. Each drive unit may include a motor/generator and a motor controller. The plurality of drive units may include at least two pairs of drive units that include a first drive-unit pair and a second drive-unit pair. The drive units in each drive pair may be connected in parallel, and the at least two pairs of drive units may be connected in series. The drive units may be configured to operate in a first mode and operate in a second mode.

Abstract: Apparatus are disclosed that are configured to passively rotate a propeller blade from a first pitch angle to a second pitch angle. An example apparatus involves: (a) a rotor hub, (b) at least one dual-pitch support coupled to the rotor hub, wherein the dual-pitch support has a first surface, a second surface and a cavity defined there between, and (c) at least one propeller blade rotatably coupled to the rotor hub such that a blade root is disposed within the dual-pitch support's cavity, where the blade root's front face is positioned against the dual-pitch support's first surface in a first position and the blade root's back face is positioned against the dual-pitch support's second surface in a second position, and the propeller blade is oriented at a first pitch angle in the first position and is oriented at a second pitch angle in the second position.