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.