Operation of hybrid-electric aircraft propulsion systems

Abstract

A method and system for operating a hybrid electric aircraft propulsion system. The method includes: providing alternating current (AC) electrical power to a first electric motor to drive a first rotary propeller; providing the first electric motor with AC electrical power from at least one electric motor inverter, the at least one electric motor inverter being operably coupled to a direct current (DC) power source; detecting a fault in a path to the first electric motor; and selectively relocating a first switching device between a generator, the at least one electric motor inverter, and the first electric motor.

Description

Technical Field

[0001] The present disclosure generally relates to aircraft propulsion systems that use power from both internal combustion engines and electric motors. Background Art

[0002] Hybrid electric aircraft propulsion systems combine internal combustion and electric propulsion technologies. In electric propulsion systems, electrical energy is converted into rotational energy by an electric motor to drive a propulsion fan or propeller.

[0003] There are environmental and cost benefits to having at least a portion of the power for an aircraft propulsion system come from electric motors.Therefore, there is a need to improve upon existing architectures. Summary of the invention

[0004] According to a broad aspect, a method for operating a hybrid electric aircraft propulsion system is provided. The method includes: providing alternating current (AC) electrical power to a first electric motor to drive a first rotary propeller; providing the first electric motor with AC electrical power from at least one electric motor inverter, the at least one electric motor inverter being operably coupled to a direct current (DC) power source; detecting a fault in a path to the first electric motor; and selectively relocating a first switching device between a generator, the at least one electric motor inverter, and the first electric motor.

[0005] According to another broad aspect, a hybrid electric aircraft propulsion system is provided, comprising: a heat engine configured to output rotational mechanical power; a generator configured to generate a first alternating current (AC) electric power source from the rotational mechanical power; at least one motor inverter configured to convert DC electric power received from a DC power source into AC electric power to provide a second AC electric power source; a first electric thruster, the first electric thruster being operably connected to the generator to receive AC electric power therefrom and operably connected to the at least one motor inverter to receive AC electric power therefrom; and a controller configured to detect a fault in a path to the first motor and selectively rearrange a switching device between the generator, the at least one motor inverter and the first motor to compensate for the fault in the path to the first motor.

[0006]

[00136] Features of the systems, devices, and methods described herein may be used in various combinations in accordance with the embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Reference is now made to the accompanying drawings, in which:

[0008] Figure 1 is a schematic cross-sectional view of a gas turbine engine according to an illustrative embodiment;

[0009] Figure 2 is a block diagram of a hybrid-electric aircraft propulsion system according to an illustrative embodiment;

[0010] Figure 3 is a block diagram of a hybrid electric aircraft propulsion system having two electric motors according to an illustrative embodiment;

[0011] Figure 4 is a block diagram of a hybrid electric aircraft propulsion system having a dual stator generator according to an illustrative embodiment;

[0012] Figure 5 is a block diagram of a hybrid electric aircraft propulsion system having a dual stator electric motor according to an illustrative embodiment;

[0013] Figure 6 is a block diagram of a hybrid-electric aircraft propulsion system having selective connections according to an illustrative embodiment;

[0014] Figure 7 is a block diagram of a hybrid-electric aircraft propulsion system with additional propulsion power in accordance with an illustrative embodiment;

[0015] Figure 8 is an example of a motor inverter according to an illustrative embodiment;

[0016] Fig. 9 is a block diagram of an exemplary controller in accordance with an illustrative embodiment.

[0017] It should be noted that throughout the drawings, like features are identified with like reference numerals. DETAILED DESCRIPTION

[0018] A hybrid electric aircraft propulsion system and method is described herein. The aircraft propulsion system uses power generated by a heat engine and power generated by an electrical generator. Figure 1 An exemplary heat engine of the type preferably provided for use in subsonic flight, namely a gas turbine engine 10, is shown. The gas turbine engine 10 generally includes, in series flow communication, a fan 12 through which ambient air is propelled, a compressor section 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular flow of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases. A high pressure rotor 20 of the turbine section 18 is drivingly coupled to a high pressure rotor 22 of the compressor section 14 via a high pressure shaft 24. A low pressure rotor 26 of the turbine section 18 is drivingly coupled to the fan rotor 12 and to other low pressure rotors (not shown) of the compressor section 14 via a low pressure shaft 28 that extends within the high pressure shaft 24 and rotates independently of the high pressure shaft.

[0019] Although shown as a turbofan engine, the gas turbine engine 10 may alternatively be another type of engine, such as a turboshaft engine, also typically including a compressor section, a combustor, and a turbine section in a serial flow communication manner. A turboprop engine may also be applied. In some embodiments, the heat engine may be a type other than a combustion engine, such as a piston engine or a rotary engine. In addition, although the engine 10 is described herein for flight applications, it should be understood that other uses, such as industry, etc., may also be applied. It should be noted that a constant volume combustion heat engine other than a piston or rotary engine may also be used.

[0020] Reference now Figure 2 , an exemplary embodiment of a hybrid electric aircraft propulsion system 200 is shown. System 200 presents an AC-AC architecture, whereby alternating current (AC) electric power is generated and applied directly to the electric motor. In an AC-DC-AC architecture, the AC electric power is converted to direct current (DC) and then reconverted to AC electric power to drive the electric motor. The AC-AC architecture is more efficient than the AC-DC-AC architecture because losses occur during the conversion stages from AC to DC and from DC to AC.

[0021] The heat engine 201 is operably coupled to a generator 202. The generator 202 receives motive power (or mechanical energy) from the heat engine 201 and converts the motive power into electrical power. The generator 202 outputs alternating current (AC) electrical power. The AC electrical power is then directly provided to an electric motor 204. The electric motor 204 converts the AC electrical power into mechanical energy in the form of a rotational force. The rotational force is applied to a rotating structure 206 (i.e., a rotating propeller), such as a propeller or a propulsion fan of an aircraft.

[0022] The electric motor 204 also receives AC electrical power from the motor inverter 208. The motor inverter 208 is operably connected to a battery 210 (or an aircraft electrical system). The battery 210 may be a dedicated battery provided for the hybrid electric aircraft propulsion system 200. Alternatively, the electrical power supplied to the inverter 208 may come from: an auxiliary power unit, a supplemental power unit, a backup generator system, or an aircraft electrical system that does not include a battery or capacitor. Therefore, the motor inverter 208 may be connected to the battery 210 via a battery bus on the aircraft or via dedicated wiring and / or connectors. Any type of device containing one or more cells that convert chemical energy directly into electrical energy may be used as a battery 210. In some embodiments, the battery 210 is based on non-chemical principles, such as using power from a supercapacitor in an energy storage mode.

[0023] The motor inverter 208 receives direct current (DC) electrical power from the battery 210 (or another DC source) and converts the DC voltage to an AC voltage, adjusting the frequency and phase of the AC voltage so that the motor 204 can generate mechanical power. When the motor 204 is driven by an external machine force, the motor inverter 208 can also be used in the opposite sense to charge the battery 210, thereby making it act as a generator, in which case the inverter can convert the AC voltage back to a DC voltage. In some embodiments, the motor inverter 208 can also be used in a reverse mode, thereby converting AC electrical power to DC electrical power.

[0024] Thus, the motor 204 has a first input that is operably coupled to the generator 202 to receive a first AC electric power source. The motor 204 also has a second input that is operably coupled to the motor inverter 208 to receive a second AC electric power source. It should be noted that the motor 204 does not need to have two independent inputs (i.e., one from the generator 202 and one from the inverter 208). The output of the generator 202 and the output of the inverter 208 can be combined or connected in parallel before the motor input interface. In response to receiving either the first AC electric power source and the second AC electric power source (or receiving both at the same time), the motor 204 will generate a rotational output for driving the rotating structure 206.

[0025] The controller 212 is configured to selectively drive the motor 204 by using a first AC electric power source from the generator 202, a second AC electric power source from the motor inverter 208, or a combination thereof. When receiving AC electric power from both the generator 202 and the motor inverter 208 simultaneously, a greater amount of power is available to the motor 204. This in turn allows a greater rotational force to be applied to the rotating structure 206.

[0026] In some embodiments, the first AC electric power source provided by the generator 202 is the primary propulsion power source for the electric motor 204. For example, in low power operating conditions, such as in a cruise mode, all propulsion power for the rotating structure 206 may be provided by the generator 202. In high power operating conditions, such as in a climb mode or a takeoff mode, a boost in propulsion power may be provided by the battery 210 through the motor inverter 208. Thus, the electric motor 204 may obtain a secondary or additional electric power source through the motor inverter 208 to supplement the electric power provided by the generator 202.

[0027] In some embodiments, the motor inverter 208 is sized to match the secondary power requirements of the motor 204, i.e., the motor inverter 208 does not need to be a full-size motor inverter in order to drive the motor 204 alone. In addition, no generator converter is required to convert the voltage from AC to DC, because the electric power generated by the generator 202 is fed to the motor 204 without conversion. Therefore, this architecture avoids the need for two conversion stages during low power operating conditions. In some embodiments, the battery 210 is recharged directly from the motor inverter 208.

[0028] In some embodiments, the motor inverter 208 is used to recover from or prevent the desynchronization of the generator 202 and the motor 204. When used for recovery from desynchronization, the motor inverter 208 can resynchronize the frequency of the motor 204 and the frequency of the generator 202 in response to a command or control signal received from the controller 212 or in response to the logic implemented in the inverter 208. The inverter 208 monitors and attempts to control the frequency and phase of the generator 202 and the motor 204. During resynchronization, the controller 212 can temporarily disconnect the generator 202 from the motor 204, for example, by opening a relay between the generator and the motor. Then, the motor inverter 208 can adjust the power of the motor 204 so that the speed of the motor 204 is modified to match the frequency of the motor 204 with the frequency of the generator 202. Then, the motor 204 and the generator 202 can be brought back into phase with each other. Once the motor 204 is back in phase with the generator 202, the connection between the generator 202 and the motor 204 is restored.

[0029] When used to prevent desynchronization, the motor inverter 208 can actively monitor the phase of the motor 204. When a phase mismatch between the generator 202 and the motor 204 is detected, such as in the case where the motor is slowed down by an external force, the motor inverter 208 can send an electrical signal in phase with the motor 204 to provide additional power to bring the motor 204 back into phase with the generator 202. This feature can be performed by the controller 212, or it can be incorporated into the inverter 208.

[0030] In some embodiments, the motor inverter 208 is used to recharge the battery 210 or to provide additional electrical power to the aircraft electrical system connected to the inverter 208. For example, the motor inverter 208 can increase the power demand on the generator 202 so that the power generated by the generator exceeds the power required by the rotating structure 206 or the load, and the excess power is fed back to the battery 210 or the aircraft electrical system. Alternatively, the motor inverter 208 can increase the power to the motor 204 by feeding the energy from the battery 210 to the motor 204. This in turn increases the power available to the rotating structure 206. If necessary, the motor inverter 208 can increase the torque available to the rotating structure 206 (for example: for a variable pitch propeller, additional torque may be required, depending on the selected pitch of the propeller), or it can act as a generator to extract energy from the wind-driven propeller by converting the AC voltage to a DC voltage higher than the DC bus voltage in order to recharge the battery or feed electrical power back to the aircraft electrical system. Inverter 208 has the ability to control the voltage on the DC bus, thereby controlling the power going to the DC bus.

[0031] refer to Figure 3 , another exemplary embodiment of a hybrid electric aircraft propulsion system 200 is shown. In this example, two motors 204a, 204b are driven by a generator 202. Each motor 204a, 204b is associated with its own rotating structure 206a, 206b, respectively. Two motor inverters 208a, 208b are also provided, one motor inverter for feeding each of the motors 204a, 204b, respectively. It should be understood that a single motor inverter 308 can also be used instead of two separate motor inverters 208a, 208b. Then, the motor inverter 308 will be sized for the power requirements of the two motors 204a, 204b, rather than only one of the motors 204a, 204b. In addition, the motor inverter 308 will need to be disconnected from the motor 204a in order to perform the resynchronization of the motor 204b, and disconnected from the motor 204b in order to perform the resynchronization of the motor 204a.

[0032] In some embodiments, in the event that one of the two motor inverters 208a, 208b fails, the two motor inverters 208a, 208b are interconnected. For example, if one motor inverter 208a fails, the other motor inverter 208b can be used to charge the battery 210 or drive the motor 204a associated with the failed motor inverter 208a. This can also be achieved by using a series connection between the motors 204a, 204b and the motor inverters 208a, 208b to allow selective connection and disconnection of the motors 204a, 204b to the motor inverters 208a, 208b.

[0033] In some embodiments, one or more relays 314a, 314b are provided in the interconnection path between the generator 202 and each of the motors 204a, 204b, respectively. The relays 314a, 314b are exemplary embodiments that allow selective connection and disconnection of the generator 202 to either of the motors 204a, 204b. Other connection / disconnection methods may also be used.

[0034] The electric motors 204a, 204b may be provided on separate wings of the aircraft. Alternatively, they may be provided on the same wing of the aircraft. And alternatively, one or both of the electric motors 204a, 204b may be provided in a nacelle or hub of a rotating propulsion device (such as a propeller, fan, lift rotor or booster), or in the hub of a counter-rotating propeller, fan rotor or booster.

[0035] Three or more motors may be provided, with each motor 204 being associated with a motor inverter 208. Alternatively, two or more motor inverters 208 may be combined to form a larger motor inverter 308 for all motors 204 or a subset thereof.

[0036] Figure 4 Yet another embodiment of a hybrid electric aircraft propulsion system 200 is shown. In this example, the generator 202 is a dual-stator generator having a first generator stator 402a driving one motor 204a and a second generator stator 402b driving another motor 204b. It should be noted that this embodiment can also be applied to three or more groups of generator stators, motors and inverters. Two or more of the inverters 208 can be combined to form a larger motor inverter 308 for all motors 204 or their sub-devices. In some embodiments, the motor inverters 208a, 208b include a converter for performing conversion from AC to DC to recharge the battery 210. The motors 204a, 204b are driven independently of each other. In this embodiment, relays 314a, 314b may or may not exist to allow selective connection / disconnection of the generator 202 and the motors 204a, 204b.

[0037] Figure 5Another exemplary embodiment of a hybrid electric aircraft propulsion system 200 is shown. In this example, one or more of the motors 204a, 204b have dual stators. The illustrated example shows a motor 204a having a first motor stator 502a and a second motor stator 504a, and a motor 204b having a first motor stator 502b and a second motor stator 504b. The motor stator 502a is operably coupled to the generator stator 402a, and the motor stator 502b is operably coupled to the generator stator 402b. The motor stator 504a is operably coupled to the motor inverter 208a, and the motor stator 504b is operably coupled to the motor inverter 208b. In this configuration, the generator 202 does not share the same motor stator with the motor inverters 208a, 208b, thus causing the generator power and the motor inverter power to be independent of each other. If the motor inverter 208a is used to recharge the battery 210, the stator 504b will act as a motor and the stator 504a will act as a generator, from which conversion from AC to DC is required to recharge the battery 210. If the motor inverter 208b is used to recharge the battery 210, the stator 504a will act as a motor and the stator 504b will act as a generator, from which conversion from AC to DC is required to recharge the battery 210.

[0038] refer to Figure 6, another embodiment of a hybrid electric aircraft propulsion system 200 is shown. In this example, additional connections are provided between the generator 202, the motors 204a, 204b, and the motor inverters 208a, 208b. By closing relays 314a and 314c and opening relay 314d, the generator stator 402a can be selectively connected to the two stators 502a, 504a of the motor 204a. By closing relays 314b and 314e and opening relay 314f, the generator stator 402b can be selectively connected to the two stators 502b, 504b of the motor 204b. By closing relays 314d and 314c and opening relay 314a, the motor inverter 208a can be selectively connected to the two stators 502a, 502b of the motor 204a. By closing relays 314f and 314e and opening relay 314b, motor inverter 208b can be selectively connected to two stators 502b, 504b of motor 204b. And, if necessary, each stator 502a and / or 502b can be connected to both generator stator 402a and inverter 208A at the same time without opening relay 314a. This helps to use the inverter to provide additional power or extract power to recharge the battery, or provide power to the aircraft DC bus, or regulate and maintain the motor and generator in phase with each other. It is the same for other motors and associated generator stators, inverters, relays, etc. This architecture provides the generator 202 with the ability to drive both stators 502a, 504a or 502b, 504b of either motor 204a, 204b and provides the motor inverter 208a, 208b with the ability to drive both stators 502a, 504a or 502b, 504b of either motor 204a, 204b.

[0039] Figure 6 The architecture also provides the ability to recharge the battery 210 directly from the generator 202 by closing relays 314a, 314c, 314d and / or 314b, 314e, 314f, thereby providing a direct path between the generator 202 and the motor inverters 208a, 208b, respectively. In this case, one or both of the motor inverters 208a, 208b will need to be provided with an AC-DC converter to convert the AC power received by the generator 202 into DC power for the battery 210. If desired, for example if it helps to start the heat engine or drive an auxiliary system connected to the generator shaft before the engine starts, such as a pump, Figure 6 The architecture also provides the ability to use batteries to provide mechanical power to the heat engine by driving stator 402a or 402b as a motor rather than a generator. The same is true for other embodiments.

[0040] Steering Figure 7 , shows yet another embodiment of a hybrid electric aircraft propulsion system 200. In this example, a rotating structure 206c is operably coupled to a heat engine 201 to provide additional propulsion to the aircraft. In fact, the motive force generated by the heat engine 201 can also be directly applied to the rotating structure 206c (such as a propeller or propulsion fan of the aircraft) to supplement the propulsion provided by the rotating structures 206a, 206b.

[0041] It should be noted that although the combination Figure 4 The embodiment shows the rotating structure 206c, but it can also be added to Figure 2 , Figure 3 , Figure 5 and Figure 6 Any of the other embodiments provided in and variations thereof. Variations thereof include, for example, a three-stator generator connected to three motors. It is to be understood that this embodiment is applicable to any number of generator stators and motor stators. Another example of a variation of this embodiment is a three-stator motor, each stator being connected to one of a generator stator, a first motor inverter, and a second motor inverter. The first and second motor inverters can be connected to the same battery or to separate batteries. Other variations will be readily understood by those skilled in the art.

[0042] In some embodiments, various architectures of hybrid-electric aircraft propulsion system 200 are used to address possible failures within system 200. Various examples of failure modes are described below.

[0043] based on Figures 2 to 7 In an embodiment, in the event of a failure of the heat engine 201, propulsion power for the rotating structure 206 is available via the battery 210. However, the available power is limited by the power and energy capacity of the battery 210 (or the aircraft DC bus) and the power rating of the motor inverter 208, 208a, 208b, 308. Similarly, in the event of a generator failure due to a short circuit, propulsion power for the rotating structure 206, 206a, 206b is available via the battery 210, but is limited by the capacity of the battery 210 and the power rating of the motor inverter 208, 208a, 208b, 308. In the event of a battery failure, propulsion power is available, but is limited by the power of the generator 202 and the available fuel for the heat engine 201.

[0044] Based on the presence of at least two electric motors 204a, 204b Figures 3 to 7In the embodiment of the present invention, in the event of a failure of one motor 204a, the other functional motor 204b can obtain full power. In the event of a failure of one motor inverter 208a, one motor 204b can obtain full power and the other motor 204a can obtain partial power, which is limited by the power of the generator 202 and the available fuel of the heat engine 201. If the two motor inverters 208a, 208b are connected together, either motor 204a, 204b can obtain full power.

[0045] Based on the generator 202 having dual stators 402, 404 Figures 4 to 7 In the embodiment of the present invention, in the event of a generator failure due to an open circuit on one of the two stators 402, 404, one of the two motors 204a, 204b can obtain full power. The other of the two motors 204a, 204b can obtain partial power, which is limited by the capacity of the battery 210 and the power rating of the motor inverter 208a, 208b associated therewith. In addition, in the event of a battery depletion, energy from running the generator stator can be transferred to the opposite motor through the two motor inverters.

[0046] Based on the fact that each motor 204a, 204b has two stators Figure 5 In the embodiment, in the event of a failure of one stator 502a or 504a, some power can still be obtained from the motor 204a. If the stator 502a fails, power can still be obtained from the battery 210, and this power is limited by the capacity of the battery 210 and the rated power of the motor inverter 208a associated therewith and the rated power of the remaining motor stator 504a. If the stator 504a fails, power can still be obtained from the generator 202, and this power is limited by the power of the generator 202 and the available fuel of the heat engine 201 and the rated power of the remaining motor stator 502a.

[0047] based on Figure 6 In the embodiment of the present invention, if the inverter 208a or 208b fails, the associated motor 204a or 204b can still obtain full power from the generator stator 402a or 402b with the help of appropriate relay configuration, which is limited by the rating of the generator. Similarly, if the generator stator 402a or 402b fails, the two motor stators of the associated motor 204a or 204b can be powered by the battery 210. Then, the total power available will depend on the rating of the inverter 208a or 208b and the battery 210.

[0048] based on Figure 7In an embodiment, if both motors 204a, 204b fail and the aircraft is out of gas, the power from the battery can be transferred to the main shaft of the heat engine 201 to generate propulsion power for the rotating structure 206c. The motor inverters 208a, 208b can be connected to the generator 202 to act as motors and add power to the rotating structure 206c and other devices such as pumps. If all electrical systems fail, the heat engine 201 can still provide propulsion power for the rotating structure 206c.

[0049] Figure 8 2 is an exemplary embodiment of a motor inverter 208. One of many possible embodiments that may be used with the hybrid electric aircraft propulsion system 200 described herein is shown. Lines V+ and V- are connected to the positive and negative terminals of the battery 210. Lines A, B, C are connected to the motor 204 and represent the three phases of AC electrical power provided to the motor 204.

[0050] refer to Fig. 9 , shows an exemplary embodiment of the controller 212, wherein the controller 212 includes a processing unit 902 and a memory 904, wherein the memory 904 stores computer-executable instructions 906. Fig. 9 It may also represent control functions embedded in the inverter 208. The processing unit 902 may include any suitable device that is configured to implement the system so that the instructions 906, when executed by the controller 212 or other programmable device, may result in the execution of functions / actions / steps as described herein. The processing unit 902 may include, for example, any type of general purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, a central processing unit (CPU), an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, other suitable programmed or programmable logic circuits, or any combination thereof.

[0051] The memory 904 may include any suitable known or other machine-readable storage medium. The memory 904 may include a non-transitory computer-readable storage medium, such as, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or apparatus, or any suitable combination of the foregoing. The memory 904 may include a suitable combination of any type of computer memory located inside or outside the controller 212, such as a random access memory (RAM), a read-only memory (ROM), a compact disk read-only memory (CDROM), an electro-optical memory, a magneto-optical memory, an erasable programmable read-only memory (EPROM) and an electrically erasable programmable read-only memory (EEPROM), a ferroelectric RAM (FRAM), and the like. The memory 904 may include any storage device (e.g., a device) suitable for retrievably storing machine-readable instructions 906 that can be executed by the processing unit 902. It is noted that the controller 212 may be implemented as part of a full authority digital engine controller (FADEC) or other similar devices, including an electronic engine controller (EEC), an engine control unit (EUC), and the like.

[0052] The methods and systems described herein may be implemented in a high-level programming language or an object-oriented programming language or a scripting language or a combination thereof to communicate with a computer system (e.g., controller 212) or to assist in the operation of a computer system (e.g., controller 212). Alternatively, the methods and systems may be implemented in assembly or machine language. The language may be a compiled or interpreted language. Program code for implementing the methods and systems may be stored on a storage medium or device, such as a ROM, a disk, an optical disk, a flash drive, or any other suitable storage medium or device. The program code may be read by a general or special programmable computer for configuring and operating the computer when the storage medium or device is read by the computer to execute the program described herein. Embodiments of the methods and systems may also be considered to be implemented by a non-transitory computer-readable storage medium having a computer program stored thereon. The computer program may include computer-readable instructions that cause the computer (or, in some embodiments, the processing unit 902 of the controller 212) to operate in a specific and predefined manner to perform the functions described herein.

[0053] Computer executable instructions can be in many forms, including program modules, that are executed by one or more computers or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. Typically, the functionality of program modules can be combined or distributed as needed in various embodiments.

[0054] The above description is intended to be exemplary only, and those skilled in the art will recognize that changes can be made to the described embodiments without departing from the scope of the disclosed invention. In view of a review of this disclosure, other modifications falling within the scope of the invention will be apparent to those skilled in the art.

[0055] Various aspects of the systems and methods described herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described above, and therefore their application is not limited to the details and arrangements of the components set forth in the foregoing description or shown in the accompanying drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although specific embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of the invention. The scope of the following claims should not be limited to the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the entire specification.

Claims

1. A method for operating a hybrid electric aircraft propulsion system, the method comprising: Providing alternating current (AC) electric power to the first electric motor to drive the first rotary propeller; providing the first electric motor with AC electrical power from at least one motor inverter operably coupled to a direct current (DC) power source; detecting a fault in a path leading to the first motor; as well as selectively relocating a first switching device between the generator, the at least one motor inverter, and the first motor; wherein the first motor comprises a first motor stator and a second motor stator, wherein the first motor stator is connected to the generator and the second motor stator is connected to the at least one first motor inverter, and wherein providing AC electric power to the first motor comprises applying AC electric power to the second motor stator of the first motor.

2. The method of claim 1 , wherein selectively rearranging the first switching device comprises: disconnecting the generator from the first motor stator of the first electric motor; connecting the at least one motor inverter to the first motor stator of the first motor; and driving the first motor stator and the second motor stator of the first motor using AC electric power from the at least one motor inverter.

3. The method according to claim 1 or 2, further comprising: providing alternating current (AC) electric power to the second electric motor to drive the second rotary propeller; providing the second electric motor with AC electrical power from the at least one motor inverter operably coupled to the DC power source; detecting a fault in a path to the second motor; as well as A second switching device is selectively relocated between the generator, the at least one motor inverter, and the second motor.

4. The method according to claim 3, wherein: The at least one motor inverter includes a first motor inverter dedicated to the first motor and a second motor inverter dedicated to the second motor.

5. The method according to claim 4, wherein: The first motor inverter and the second motor inverter are interconnected, and wherein selectively rearranging the first switching device or the second switching device includes using the first motor inverter with the second motor or using the second motor inverter with the first motor.

6. The method according to any one of claims 3 to 5 further includes detecting a fault in a thermal engine that provides power to the generator, and wherein selectively rearranging the first switching device or the second switching device includes selectively rearranging the first switching device or the second switching device to compensate for the fault in the thermal engine.

7. The method according to claim 4 or 5, wherein: The generator includes a first generator stator connected to the first motor and a second generator stator connected to the second motor.

8. The method according to claim 5, wherein: Selectively rearranging the first switching device includes providing AC power from the second motor inverter to the first motor through the first motor inverter.

9. The method according to claim 5, wherein: Selectively rearranging the first switching device includes providing AC power from the first motor inverter and the second motor inverter to the generator.

10. A hybrid electric aircraft propulsion system comprising: a heat engine configured to output rotational mechanical power; a generator configured to generate a first source of alternating current (AC) electrical power from the rotating mechanical power; at least one motor inverter configured to convert DC electric power received from a DC power source into AC electric power to provide a second AC electric power source; a first electric propulsion machine operably coupled to the generator to receive AC electric power therefrom and operably coupled to the at least one electric machine inverter to receive AC electric power therefrom; as well as a controller configured to detect a fault in a path to a first motor and selectively rearrange switching devices between the generator, the at least one motor inverter, and the first motor to compensate for the fault in the path to the first motor; Wherein, the first electric motor comprises a first motor stator and a second motor stator, wherein the first motor stator is connected to the generator and the second motor stator is connected to the at least one first motor inverter.

11. The system according to claim 10, wherein: Selectively rearranging the first switching device includes: disconnecting the generator from the first motor stator of the first motor; connecting the at least one motor inverter to the first motor stator of the first motor; and driving the first motor stator and the second motor stator of the first motor using AC electric power from the at least one motor inverter.

12. The system according to claim 10 or 11, further comprising: a second electric propulsion machine operably coupled to the generator to receive AC electric power therefrom and operably coupled to the at least one electric machine inverter to receive AC electric power therefrom; as well as Wherein, the controller is also configured to detect a fault in a path leading to the second motor and selectively rearrange a switching device between the generator, the at least one motor inverter and the second motor to compensate for the fault in the path leading to the second motor.

13. The system according to claim 12, wherein: The at least one motor inverter includes a first motor inverter dedicated to the first motor and a second motor inverter dedicated to the second motor.

14. The system of claim 13, wherein the first motor inverter and the second motor inverter are interconnected, and wherein selectively rearranging the first switching device or the second switching device includes using the first motor inverter with the second motor or using the second motor inverter with the first motor.

15. A system according to any one of claims 12 to 14, wherein: The controller is further configured to detect a fault in the heat engine, and wherein selectively rearranging the first switching device or the second switching device includes selectively rearranging the first switching device or the second switching device to compensate for the fault in the heat engine.

16. The system according to claim 13 or 14, wherein: The generator includes a first generator stator connected to the first motor and a second generator stator connected to the second motor.

17. The system of claim 14, wherein: Selectively rearranging the first switching device includes providing AC power from the second motor inverter to the first motor through the first motor inverter.

18. The system of claim 14, wherein: Selectively rearranging the first switching device includes providing AC power from the first motor inverter and the second motor inverter to the generator.

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