Hybrid-electric aircraft propulsion system control system and method

A hybrid-electric propulsion (HEP) system, comprising:

• a propulsor;
• a compressor;
• a gas turbine engine, the gas turbine engine having a free turbine configuration including a first shaft connecting a high-pressure turbine to the compressor, and a second shaft connecting a power turbine to the propulsor, wherein the first shaft and the second shaft are different from each other and not mechanically connected to each other, and wherein each of the first shaft and the second shaft is aligned with and configured to rotate about an axial centerline of the gas turbine engine;
• an electrical power motive system having a first electric motor, a second electric motor, a first inverter, and a second inverter;
• and
• a system controller;
• wherein the gas turbine engine is configured to provide motive force to the propulsor;
• wherein the first electric motor is configurable in a drive mode to provide motive force to the propulsor or in generator mode to produce electrical energy;
• wherein the second electric motor is in communication with the compressor and the second shaft;
• and
• wherein the system controller is in communication with the gas turbine engine, the first inverter, the second inverter, and a non-transitory memory storing instructions, which instructions when executed cause the system controller to control the second inverter to operate the second electric motor to provide a motive force to the compressor of the gas turbine engine during a low power setting of the gas turbine engine.