Active voltage control for hybrid electric aircraft

An aircraft comprising:

• an AC power source;
• an AC bus;
• first switching means arranged to switchably couple AC power from the AC power source to the AC bus;
• an HVDC power source;
• an active voltage controller configured to generate a control signal representing a magnitude of a HVDC bus reference voltage based on a current of the HVDC power source;
• an active rectifier unit comprising an active rectifier configured to convert AC power to HVDC power and a controller configured to control the active rectifier to adjust an HVDC bus voltage in dependence on the control signal received from the active voltage controller;
• second switching means arranged to switchably couple AC power from the AC bus to the active rectifier unit;
• an HVDC bus coupled to receive DC power from one or both of the HVDC power source and active rectifier unit in dependence on the HVDC bus voltage from the active rectifier unit;
• an electric propulsion motor coupled to receive HVDC power from the HVDC bus;
• and
• a propeller operatively coupled to the electric propulsion motor.