Patent Publication Number: US-2020277078-A1

Title: Electrical power system for aircraft having hybrid-electric propulsion system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/812,655, filed Mar. 1, 2019, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention is directed to an electrical power system, and more particularly, to an electrical power system for an aircraft having a hybrid-electric propulsion system. 
     2. Description of Related Art 
     The level of air traffic continues to increase worldwide, leading to increased fuel consumption and air pollution. Consequently, efforts are underway to make aircraft more environmentally compatible through the use of specific types of fuel and/or by reducing fuel consumption through the use of more efficient drive systems. 
     For example, aircraft having mixed drive systems that include a combination of various types of engines are known for reducing pollutants and increasing efficiency. Some current combinations include reciprocating engines and jet engines, reciprocating engines and rocket engines, jet engines and rocket engines, or turbojet engines and ramjet engines. 
     While these mixed drive systems are useful, they are not readily adaptable for use on commercial passenger aircraft. However, hybrid-electric propulsion systems that provide power through a combustion engine and an electric motor are indeed adaptable for use with commercial passenger aircraft and can provide efficiency benefits including reduced fuel consumption. The subject invention is directed to an aircraft having such a propulsion system, and to an electrical power system associated with an electric motor of that propulsion system. 
     SUMMARY OF THE DISCLOSURE 
     The subject invention is directed to a new and useful electrical power system for an aircraft having a hybrid-electric propulsion system. The electric power system includes a battery assembly for storing energy, an electric motor controller operatively connected to the battery assembly for conditioning and controlling power to an electric motor, and an electric motor receiving power through the motor controller for delivering torque to a shaft of the hybrid-electric propulsion system. It is envisioned that power would be distributed in this electrical power system using High Voltage Direct Current (HVDC) to reduce power losses in distribution. 
     The electrical power system further comprises a battery management system for monitoring and controlling the battery assembly, and a contactor coil for disconnecting the battery assembly from the electric motor controller. It is envisioned that the battery assembly would be ungrounded with respect to the aircraft. It is further envisioned that the battery management system would control the contactor only during a condition of battery system failure. It is also envisioned that contactor could contain a pre-charge circuit to ensure the system remains service ready, or the pre-charge circuit could be incorporated into the battery assembly itself. 
     Preferably, a thermal fuse is located between the electric motor controller and the electric motor, and a current sensor is operatively associated with the electric motor to detect an overcurrent condition. In addition, means are preferably provided for disconnecting the electric motor from the output shaft to protect the motor in the event of a system failure condition (e.g., line to ground fault). 
     The electric motor controller is operatively associated with an engine control unit of the aircraft to provide redundant control of the delivery of power to the electric motor. The electric motor controller is also operatively associated with the means for disconnecting the electric motor from the output shaft in the event of a system failure condition. It is envisioned that the electric motor controller would be grounded with respect to the aircraft. 
     The architecture of the electric motor controller can vary depending upon the design criteria of the application. For example, in an embodiment of the invention, the digital circuitry of the electric motor controller architecture could include a series of programmable electronic memory components or the like. In another embodiment of the invention, the digital circuitry of the electric motor controller could include a field-programmable gate array (FPGA). In yet another embodiment of the invention, the digital circuitry of the electric motor controller could also include a digital signal processor (DSP) designed to improve the accuracy and reliability of digital communications. 
     It is envisioned that the electric motor controller would have certain conventional features to the extent that it utilizes a three level inverter topology to convert DC power from the battery assembly into Pulse Width Modulation (PWM) to control the speed of the electric motor by varying the switching frequency. 
     In addition, it is envisioned that the electric motor controller would be configured to control current and frequency to the electric motor to control torque output to the shaft. It would also be configured to provide electric power system protections and to communicate with the battery management system. The electric motor controller would also be configured to provide information to the pilot and flight engineer relating to system performance and health, and it is also configured to perform backup torque command calculations in case of ECU failure based on PLA input. 
     In accordance with a preferred embodiment of the subject invention, the electric motor is operatively associated with a heat engine, and together these two power sources define a hybrid electric propulsion system. It is envisioned that the electric motor would be designed to produce a sufficient amount of shaft power suitable for a particular engine configuration or aircraft. 
     It is envisioned that the electric motor and the heat engine of the hybrid-electric propulsion system could be arranged in a parallel drive configuration or in an in-line drive configuration. It is also envisioned that power may be evenly split between the electric motor and the heat engine, or it may be proportionally divided between the two electric motor and the heat engine. For example, in certain application, the electric motor may provide a lower percentage of the overall power relative to the heat engine, or vice versa. 
     These and other features of the electrical power system of the subject invention will become more readily apparent to those having ordinary skill in the art to which the subject invention appertains from the detailed description of the preferred embodiments taken in conjunction with the following brief description of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those having ordinary skill in the art will readily understand how to make and use the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to the figures wherein: 
         FIG. 1  is a side elevational view of an aircraft that includes a hybrid-electric propulsion system operatively associated with the electrical power system of the subject invention; 
         FIG. 2  is a schematic representation of the hybrid-electric propulsion system associated with the electrical power system of the subject invention; and 
         FIG. 3  is a schematic representation of the electrical power system of the subject invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings wherein like reference numeral identify similar structure or features of the subject invention, there is illustrated in  FIG. 1  a commercial aircraft  10  that includes an engine nacelle  12  housing a propulsion system that delivers power to an air mover or propeller  14  to propel the aircraft  10 . 
     In accordance with a preferred embodiment of the subject invention, the propulsion system in engine nacelle  12  is a hybrid electric propulsion system, which is shown schematically in  FIG. 2  and is designated generally by reference numeral  20 . The hybrid-electric propulsion system  20  has an electric motor  22  and a heat engine  24  that deliver power to an air mover or propeller  14 . The electric motor  22  and the heat engine  24  of the hybrid-electric propulsion system  20  can be arranged in a parallel drive configuration or an in-line drive configuration, depending upon the application and/or aircraft. Power can be evenly split between the electric motor  22  and the heat engine  24  (i.e., a split of 50% electric motor power and 50% heat engine power), or power can be divided proportionally between the electric motor  22  and the heat engine  24  (e.g., any split from 10% electric motor power to 90% heat engine power or vice versa). 
     The hybrid-electric propulsion system  20  shown in  FIG. 2 , further includes a Motor Controller (MC)  26  and an Engine Control Unit (ECU)  28  which communicate with one another by way of communication BUS or a similar network or communication system. The hybrid electric propulsion system  20  receives control input from the pilot by way of a Power Lever Angle (PLA) throttle  30  or through a similar electronic or mechanical input control feature. The hybrid-electric propulsion system  20  further includes a Propeller Control Unit (PCU)  32  that receives input from the pilot by way of a Condition Lever Angle (CLA) throttle  34  or a similar electronic or mechanical input control feature. 
     It is envisioned that the electric motor  22  would be designed to provide sufficient shaft power suitable for a particular engine configuration or aircraft. It is further envisioned that the heat engine  24  of the hybrid-electric propulsion system  20  could be a heat engine of any type e.g., a gas turbine, spark ignited, diesel, rotary or reciprocating engine of any fuel type and with any configuration of turbomachiney elements, either turbocharger, turbosupercharger, supercharger and exhaust recovery turbo compounding, either mechanically, electrically, hydraulically or pneumatically driven. An example of a rotary engine suitable for this application is disclosed in U.S. Pat. No. 10,145,291, the disclosure of which is herein incorporated by reference in its entirety. 
     Referring now to  FIG. 3 , the hybrid-electric propulsion system  20  is operatively associated with an electrical power system  40 , which directs and controls the flow of power thereto. Moreover, in the electrical power system  40 , power is distributed using HVDC. Utilizing HVDC results in reduced power losses in power distribution. 
     The electrical power system  40  of the hybrid electric propulsion system  20  of includes a battery assembly  42  including a plurality of battery cells for storing power. The battery cells can be rechargeable. The power system  40  further includes an electric motor  22  that receives power from the battery assembly  42  and delivers torque to an output shaft  44  of the hybrid-electric propulsion system  20 . The power system  40  further includes an electric motor controller  26  that is operatively connected to the battery assembly  42  and the electric motor  22  for conditioning and controlling power to the electric motor  22 . 
     The electrical power system  40  of the subject invention is adapted and configured so the electrical motor controller  26  is cable of handling the full voltage range of the battery (i.e., from 100% SoC to depletion of the battery). It is also envisioned that the line voltage delivered to the electric motor  22  could be AC voltage. It is further envisioned that the power system  40  may be adapted and configured with a circuit to pre-charge the electrical motor controller  26  so that it remains service ready. 
     The electrical power system  40  further includes a battery management system  46 . The battery management system  46  is adapted and configured to monitor battery system conditions (e.g., state of charge, state of health, temperature, etc.) and control battery system functions (e.g., power distribution amongst power cells, thermal management, cell balancing, recharging, etc.). It is further envisioned that the power system  40  may be adapted and configured with a circuit to pre-charge the electrical motor controller  26  so that it remains service ready. 
     A contactor  48  is provided for disconnecting the battery assembly  42  from the electric motor controller  26  when the batteries are taken offline when the electric power lane of the hybrid-electric propulsion system is off, as well as in the event of an emergency condition. It is further envisioned that the pre-charge circuit could be incorporated into contactor  48 . It is also envisioned that the battery assembly  42  would be ungrounded with respect to the aircraft  10 . It is further envisioned that the battery management system  46  would control the contactor  48  only during a condition of battery system failure. Otherwise, the contactor  48  would be controlled manually by the pilot or through the motor controller  26  or the ECU  28 . 
     Preferably, the power system  40  includes a thermal fuse  50  or a similar mechanism located in the power lane between the electric motor controller  26  and the electric motor  22 , which will open in the event a system fault occurs which creates an overcurrent condition. The power system  40  also includes a current sensor that is operatively associated with the electric motor  22  to detect or otherwise sense an overcurrent condition. In addition, a device  52  is provided for disconnecting the electric motor  22  from the shaft  54  to protect the electric motor  22  in the event of an unfavorable operating condition, such as, for example, an overcurrent condition or a line to ground fault condition. 
     The electric motor controller  26  is operatively associated with the ECU  28  of the aircraft  10  to provide redundant control of the delivery of power to the electric motor  22  in the event that the motor control  26  fails or is disrupted. The electric motor controller  26  is also operatively associated with the device  54  for disconnecting the electric motor  22  from the shaft  54  in the event of a system failure or unfavorable operating condition. It is envisioned that the electric motor controller  26  would be grounded with respect to the aircraft  10 . 
     The architecture of the electric motor controller  26  can vary depending upon the design criteria of the application. For example, in an embodiment of the invention, the digital circuitry of the electric motor controller  26  could include a series of programmable electronic memory components or the like. In another embodiment of the invention, the digital circuitry of the electric motor controller  26  could include a field-programmable gate array (FPGA). In yet another embodiment of the invention, the digital circuitry of the electric motor controller  26  could also include a digital signal processor (DSP) designed to improve the accuracy and reliability of digital communications. 
     It is envisioned that the electric motor controller  26  would have certain conventional features to the extent that it utilizes a three level inverter topology to convert DC power from the battery assembly into Pulse Width Modulation (PWM) to control the speed of the electric motor  22  by varying the switching frequency. 
     In addition to such conventional features, it is envisioned that the electric motor controller  26  would be configured to control current and frequency to the electric motor  22  to control torque output to the shaft  54 . It would also be configured to provide electric power system protections (e.g., feeder cable protection) and to communicate with the battery management system  46 . The electric motor controller  26  would be also configured to provide information to the pilot and flight engineer relating to system performance and health, and it would also be configured to perform backup torque command calculations in case of failure of the ECU  28  based on input from PLA  30 . It is also envisioned that the electrical motor controller  26  could be configured to control or otherwise adjust the torsional dynamics between the electric motor  22  and the heat engine  24 . 
     While the subject disclosure has been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.