Turbogenerator power control system

• US 6,325,142 B1
• Filed: 05/22/1999
• Issued: 12/04/2001
• Est. Priority Date: 01/05/1998
• Status: Expired due to Term

• Current Assignee: Capstone Turbine Corp.
• Original Assignee: Capstone Turbine Corp.
• Inventors: Bosley, Robert W., Edelman, Edward C.
• Primary Examiner(s): Bagnell, David
• Assistant Examiner(s): DOUGHERTY, JENNIFER R
• Application Number:
  US09/316,896
• Time in Patent Office: 927 Days
• Field of Search: 166/53, 417/12, 318/140, 318/430, 318/723, 318/801, 290/46, 290/52, 74/41
• US Class Current: 166/53
• CPC Class Codes: E21B 47/009 Monitoring of walking-beam pump systems
• CPC Class Codes: F02C 9/56 with power transmission control
• CPC Class Codes: F04B 47/022 driving of the walking beam
• CPC Class Codes: F05D 2200/15 Inverse
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator

Abstract

A power control system for a turbogenerator which provides electrical power to one or more pump-jack oil wells. When the induction motor of a pump-jack oil well is powered by three-phase utility power, the speed of the pump-jack shaft varies only slightly over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This power variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This power control system comprises a turbogenerator inverter, a load inverter, and a central processing unit which controls the frequency and voltage/current of each inverter. Throughout the oil well'"'"'s pumping cycle, the central processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole steel pump rods and oil, and to rotationally accelerate and decelerate the masses of the motor rotors and counter balance weights. This allows kinetic energy to be alternately stored in and extracted from the moving masses of the oil well and allows the oil pumping power to be precisely controlled. Historical data on the load inverter'"'"'s frequency versus time profile throughout previous pumping cycles, which resulted in nearly constant turbogenerator power requirements, is utilized to further reduce variations in power.

Claims

1. A system, comprising:

a turbogenerator;

a cyclic motion machine driven by an electric motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said inverter in accordance with a variable frequency time profile for said electric motor based on historical machine cycle position and corresponding inverter frequency data to provide a substantially constant power level to said electric motor.

2. A system, comprising:

a turbogenerator;

a cyclic motion machine driven by an electric motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said inverter in accordance with a variable frequency time profile for said electric motor based on historical machine cycle position and corresponding inverter frequency data to provide a substantially constant power level to said electric motor, wherein said variable frequency time profile is established by four control loops, one control loop providing a temperature safety limit, one control loop providing a speed safety limit, one control loop providing a power variation minimizing control based on instantaneous data and one control loop providing power variation minimizing control based on said historical data.

3. The system of claim 2 wherein said controller includes:

a high frequency inverter synchronously connected to said turbogenerator;

a direct current bus electrically connecting said high frequency inverter with said load inverter; and

a processor to control the frequency and voltage/current of said high frequency inverter and said load inverter.

4. The system of claim 3 wherein said control loop providing a power variation minimizing control based on instantaneous data includes a first control loop to adjust fuel flow to said turbogenerator to match the power generated by said turbogenerator with the current power requirements of said electric motor, and a second control loop to adjust said load inverter frequency so that said electric motor power requirements match the current power generated by said turbogenerator.

5. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well having axially moving and rotationally moving masses, and said processor varies the frequency of said load inverter to accelerate and decelerate said axially moving and rotationally moving masses of said pump-jack oil well to control the power requirements of said electric motor driving said pump-jack oil well.

6. The system of claim 5 wherein the frequency of said load inverter is varied to minimize variations in the power requirements of said electric motor driving said pump-jack oil well over the operating cycle of said pump-jack oil well.

7. The system of claim 5 wherein the frequency of said load inverter is established to match the oil pumping rate of said pump-jack oil well with the rate at which oil seeps into the oil well.

8. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor varies the instantaneous frequency of said load inverter over the operating cycle of said pump-jack oil well.

9. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor varies the instantaneous voltage of said load inverter over the operating cycle of said pump-jack oil well.

10. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor varies the instantaneous current of said load inverter over the operating cycle of said pump-jack oil well.

11. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor varies the frequency of said load inverter over the operating cycle of said pump-jack oil well to reduce variations in the power requirements of said electric motor driving said pump-jack oil well.

12. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor varies the voltage or current of said load inverter over the operating cycle of said pump-jack oil well to control the slip of said electric motor driving said pump-jack oil well.

13. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and, over the operating cycle of said pump-jack oil well, said processor controls the instantaneous pumping work performed by said pump-jack oil well and the instantaneous pumping work being extracted from said pump-jack oil well.

14. The system of claim 3 wherein said cyclic motion machine driven by an electric motor is a pump-jack oil well, and said processor causes the total of instantaneous pumping energy required or produced by said pump-jack oil well, and the instantaneous kinetic energy extracted from or inserted into said pump-jack oil well, to be substantially constant over the operating cycle of said pump-jack oil well.

15. A system, comprising:

a turbogenerator;

a plurality of cyclic motion machines each driven by an electric motor;

a load inverter connected to said turbogenerator to deliver power to each of said motors; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said load inverter in accordance with a variable frequency time profile for said electric motor of each of said plurality of machines based on historical machine cycle position and corresponding inverter frequency data for each of said plurality of machines to provide a substantially constant total power level to said motors.

16. A system, comprising:

a turbogenerator;

a plurality of cyclic motion machines each driven by an electric motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said load inverter in accordance with a variable frequency time profile for said electric motor of each of said plurality of machines based on historical machine cycle position and corresponding inverter frequency data for each of said plurality of machines to provide a substantially constant total power level to said motors, wherein said variable frequency time profile is established by four control loops, one control loop providing a temperature safety limit, one control loop providing a speed safety limit, one control loop providing a power variation minimizing control based on instantaneous data and one control loop providing power variation minimizing control based on said historical data.

17. The system of claim 16 wherein:

said plurality of cyclic motion machines each driven by an electric motor are a plurality of pump-jack oil wells;

said controller includes a high frequency inverter synchronously connected to said turbogenerator, a direct current bus electrically connecting said high frequency inverter with said load inverter, and a processor to control the frequency and voltage/current of said high frequency inverter and said load inverter; and

said control loop providing a power variation minimizing control based on instantaneous data includes a first control loop to adjust fuel flow to said turbogenerator to match the power generated by said turbogenerator with the current power requirements of said plurality of pump-jack oil well'"'"'s electric motors, and a second control loop to adjust said load inverter frequency so that the power requirements of said plurality of pump jack oil well'"'"'s electric motors match the current power generated by said turbogenerator.

18. A system, comprising:

a turbogenerator including a permanent magnet generator/motor, a compressor, and a gas turbine having a combustor;

at least one pump-jack oil well driven by an electric induction motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said load inverter in accordance with a variable frequency time profile for said electric induction motor of said pump-jack oil well based on historical pump-jack oil well cycle position and corresponding inverter frequency data to provide a substantially constant power level to said motor.

19. A system, comprising:

a turbogenerator including a permanent magnet generator/motor, a compressor, and a gas turbine having a combustor;

at least one pump-jack oil well driven by an electric induction motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said load inverter in accordance with a variable frequency time profile for said electric induction motor of said pump-jack oil well based on historical pump-jack oil well cycle position and corresponding inverter frequency data to provide a substantially constant power level to said motor, wherein said controller includes a plurality of primary control loops.

20. The system of claim 19 wherein one of said primary control loops is a turbine exhaust gas temperature control loop.

21. The system of claim 19 wherein one of said primary control loops is a turbogenerator speed control loop.

22. The system of claim 19 wherein one of said primary control loops is a power control loop.

23. The system of claim 19 wherein said primary control loops include a turbine exhaust gas temperature control loop and a turbogenerator speed control loop.

24. The system of claim 19 wherein said primary control loops include a turbine exhaust gas temperature control loop and a power control loop.

25. The system of claim 19 wherein said primary control loops include a power control loop and a turbogenerator speed control loop.

26. The system of claim 19 wherein said primary control loops include a turbine exhaust gas temperature control loop, a turbogenerator speed control loop, and a power control loop.

27. The system of claim 26 wherein said turbine exhaust gas temperature control loop and said turbogenerator speed control loop command fuel input to the turbogenerator combustor.

28. The system of claim 27, further comprising:

a selector to select the minimum fuel command from said turbine exhaust gas temperature control loop and said turbogenerator speed control loop.

29. The system of claim 26 wherein said controller further comprises a turbogenerator speed command control loop and a turbogenerator power command control loop.

30. The system of claim 26 wherein said controller further comprises a maximum turbogenerator speed control loop and a maximum turbine exhaust gas temperature control loop.

31. A system, comprising:

a turbogenerator including a permanent magnet generator/motor, a compressor, and a gas turbine having a combustor;

at least one pump-jack oil well driven by an electric induction motor;

a load inverter connected to said turbogenerator to deliver power to said motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said load inverter in accordance with a variable frequency time profile for said electric induction motor of said pump-jack oil well based on historical pump-jack oil well cycle position and corresponding inverter frequency data to provide a substantially constant power level to said motor;

a high frequency inverter synchronously connected to said turbogenerator;

a direct current bus electrically connecting said high frequency inverter with said load inverter; and

a processor to control the frequency and voltage/current of said high frequency inverter and said load inverter.

32. The system of claim 31 wherein said processor includes a plurality of primary control loops.

33. The system of claim 32 wherein one of said primary control loops is a turbine exhaust gas temperature control loop.

34. The system of claim 32 wherein one of said primary control loops is a turbogenerator speed control loop.

35. The system of claim 32 wherein one of said primary control loops is a power control loop.

36. The system of claim 32 wherein said primary control loops include a turbine exhaust gas temperature control loop and a turbogenerator speed control loop.

37. The system of claim 32 wherein said primary control loops include a turbine exhaust gas temperature control loop and a power control loop.

38. The system of claim 32 wherein said primary control loops include a power control loop and a turbogenerator speed control loop.

39. The system of claim 32 wherein said primary control loops include a turbine exhaust gas temperature control loop, a turbogenerator speed control loop, and a power control 3 loop.

40. The system of claim 39 wherein said turbine exhaust gas temperature control loop and said turbogenerator speed control loop command fuel output to the turbogenerator combustor.

41. The system of claim 40, further comprising:

a selector to select the minimum fuel command from said turbine exhaust gas temperature control loop and said turbogenerator speed control loop.

42. The system of claim 39 wherein said controller additionally includes a turbogenerator speed command control loop and a turbogenerator power command control loop.

43. The system of claim 39 wherein said controller additionally includes a maximum turbogenerator speed control loop and a maximum turbine exhaust gas temperature control loop.

44. The system of claim 31 wherein said processor utilizes a once per pumping cycle signal generated by each pump-jack oil well that is powered by said turbogenerator to synchronize said historical inverter frequency versus time data with said pump-jack oil well'"'"'s pumping cycle position.

45. The system of claim 31 wherein said processor comprises shift registers to store the average load inverter frequency data to be frequency and phase locked to the pumping cycle of each said pump-jack oil well being powered by said turbogenerator.

46. The system of claim 31 wherein said processor computes the average historical frequency of the load inverter for any point within a pumping cycle for each said pump-jack oil being powered by said turbogenerator.

47. The system of claim 31 wherein said processor computes the substantially best frequency for the load inverter at any point in time to minimize the variations in turbogenerator power requirements of one or more pump-jack oil wells powered by said turbogenerator, said processor computing the substantially best frequency based on historical frequency versus time data for the load inverter and once per pump cycle signals from said pump-jack oil wells powered by said turbogenerator.

48. The system of claim 31 wherein said processor includes a frequency computer for each pump-jack oil well supplied with electrical power by said turbogenerator, said frequency computer receiving a once per pump cycle signal from its associated pump-jack oil well and computing the substantially best frequency for the load inverter.

49. The system of claim 48 wherein said processor additionally includes an averager to receive the computed frequencies from said frequency computer for each pump-jack oil well and to calculate a compromise frequency for each pump-jack oil well.

50. The system of claim 48 wherein each frequency computer includes a plurality of inverter pulse registers.

51. The system of claim 48 wherein each frequency computer includes a plurality of inverter pulse registers and a plurality of motor slip pulse registers.

52. A system, comprising:

a turbogenerator including a permanent magnet generator/motor, a compressor, and a gas turbine having a combustor;

a plurality of pump-jack oil wells each driven by an electric induction motor;

a load inverter connected to said generator to deliver power to said induction motors; and

a controller controlling said turbogenerator and said inverter to establish a variable frequency time profile for each said electric induction motor of each said plurality of pump-jack oil wells, said controller utilizing pump-jack oil well cycle position data and historical data on the variable frequency versus pump-jack oil well cycle position profile of each of said plurality of pump-jack oil wells to provide a substantially constant total power level to said induction motors.

53. A system, comprising:

a turbogenerator including a permanent magnet generator/motor, a compressor, and a gas turbine having a combustor;

a plurality of pump-jack oil wells each driven by an electric induction motor;

a load inverter connected to said generator to deliver power to said induction motors; and

a controller controlling said turbogenerator and said inverter to establish a variable frequency time profile for each said electric induction motor of each said plurality of pump-jack oil wells, said controller utilizing pump-jack oil well cycle position data and historical data on the variable frequency versus pump-jack oil well cycle position profile of each of said plurality of pump-jack oil wells to provide a substantially constant total power level to said induction motors, wherein said variable frequency time profile is established by four control loops, one control loop providing a temperature safety limit, one control loop providing a speed safety limit, one control loop providing a power variation minimizing control based on instantaneous data and one control loop providing power variation minimizing control based on historical data.

54. A method of controlling a system including a turbogenerator and a cyclic motion machine driven by an electric motor, comprising:

providing electrical power from said turbogenerator to said electric motor of said cyclic motion machine;

controlling said turbogenerator and said cyclic motion machine to establish a variable frequency time profile for said electric motor of said cyclic motion machine; and

utilizing cyclic motion machine cycle position data and historical data on the variable frequency versus cyclic motion machine cycle position profile to provide a substantially constant power level to said electric motor during repetitive cyclic motion cycles.

55. A method of controlling a system including a turbogenerator and a cyclic motion machine driven by an electric motor, comprising:

providing electrical power from said turbogenerator to said electric motor of said cyclic motion machine;

controlling said turbogenerator and said cyclic motion machine to establish a variable frequency time profile for said electric motor of said cyclic motion machine; and

utilizing instantaneous data on power and historical data on power to provide a substantially constant power level requirement for said turbogenerator during current repetitive cyclic motion cycles.

56. A method of controlling a system including a turbogenerator and a plurality of cyclic motion machines each driven by an electric motor, comprising:

providing electrical power from said turbogenerator to said electric motor of each of said plurality of cyclic motion machines through a load inverter connected to each said electric motor;

controlling said turbogenerator and said inverter to establish a variable frequency time profile for said electric motor of each of said plurality of cyclic motion machines; and

utilizing cyclic motion machine cycle position data and historical data on the variable frequency versus cyclic motion machine cycle position profile to provide a substantially constant total power level to said electric motors during current repetitive cyclic motion cycles.

57. A method of controlling a system including a turbogenerator and a plurality of cyclic motion machines each driven by an electric motor, comprising:

providing electrical power from said turbogenerator to said electric motor of each of said plurality of cyclic motion machines through a load inverter connected to each said electric motor;

controlling said turbogenerator and said inverter to establish a variable frequency time profile for said electric motor of each of said plurality of cyclic motion machines, said variable frequency time profile being established by four control loops, one control loop providing a temperature safety limit, one control loop providing a speed safety limit, one control loop providing a power variation minimizing control based on instantaneous data and one control loop providing power variation minimizing control based on historical data; and

utilizing cyclic motion machine cycle position data and historical data on the variable frequency versus cyclic motion machine cycle position profile to provide a substantially constant total power level to said electric motors during current repetitive cyclic motion cycles.

58. A method to reduce variations in the power level provided to a cyclic motion machine having cyclically varying power requirements, comprising:

connecting an induction motor to the cyclic motion machine to drive the machine;

connecting a load inverter to the motor to provide power to the motor;

monitoring the inverter frequency at a preselected number of machine positions during a machine cycle for a predetermined number of machine cycles to accumulate historical data; and

varying the load inverter frequency over each machine cycle in accordance with the historical data to reduce variations in the power level required by the motor.

59. The method of claim 58, wherein varying the load inverter frequency comprises:

varying the load inverter frequency to accelerate the motor over preselected ranges of each machine cycle to reduce variations in the power level required by the motor.

60. The method of claim 59, wherein varying the load inverter frequency to accelerate the motor over preselected ranges of each machine cycle comprises:

varying the load inverter frequency to accelerate the motor during periods of reduced machine load over each machine cycle to insert kinetic energy into the machine and reduce variations in the power level required by the motor.

61. The method of claim 58, wherein varying the load inverter frequency comprises:

varying the load inverter frequency and the load inverter voltage.

62. The method of claim 61, wherein varying the load inverter frequency and the load inverter voltage comprises:

varying the load inverter voltage approximately with the square root of the load inverter frequency.

63. The method of claim 58, further comprising:

connecting a turbogenerator to the load inverter to provide power to the load inverter.

64. The method of claim 63, further comprising:

controlling the speed of the turbogenerator.

65. The method of claim 64, wherein controlling the speed of the turbogenerator comprises:

maintaining the speed of the turbogenerator at a generally constant level.

66. The method of claim 65, wherein maintaining the speed of the turbogenerator at a generally constant level comprises:

maintaining the speed of the turbogenerator generally at a level required to produce the power supplied by the load inverter to the motor.

67. The method of claim 64, wherein controlling the speed of the turbogenerator comprises:

maintaining the speed of the turbogenerator generally at a level required to maintain the average frequency of the load inverter substantially at a preselected level.

68. The method of claim 67, wherein maintaining the speed of the turbogenerator generally at a level required to maintain the average frequency of the load inverter substantially at a preselected level further comprises:

measuring the instantaneous power provided by the load inverter to the motor; and

varying the load inverter frequency in response to the difference between the measured instantaneous power and a preselected motor power level.

69. The method of claim 58, wherein varying the load inverter frequency comprises:

maintaining the average frequency of the load inverter generally at the frequency of a utility grid connected to the load inverter.

70. The method of claim 58, wherein the machine is an oil well pump-jack, and varying the load inverter frequency comprises:

maintaining the average frequency of the load inverter generally at the frequency required to match the pumping rate of the pump-jack to the seepage rate of oil into the oil well.

71. The method of claim 58, further comprising:

connecting a controller to the load inverter to monitor and vary the load inverter frequency.

72. The method of claim 71, wherein connecting the controller further comprises:

providing a controller registry to accumulate the historical data.

73. The method of claim 72, wherein providing the controller registry comprises:

providing a controller registry to accumulate the historical data at each of a preselected number of machine positions during each machine cycle for a predetermined number of machine cycles.

74. The method of claim 73, wherein providing the controller registry comprises:

providing the controller registry to store the historical data to be frequency and phase locked to the cycles of the machine.

75. The method of claim 58, further comprising:

connecting an energy storage device to the inverter; and

controlling the inverter to transfer excess energy produced by the machine from the motor to the energy storage device.

76. A method to reduce variations in the total power level provided to a plurality of cyclic motion machines having cyclically varying power requirements, comprising:

connecting an induction motor to each cyclic motion machine to drive the respective machine;

connecting a load inverter to the motors to provide power to the motors;

monitoring the inverter frequency at a preselected number of machine positions during a machine cycle for each machine over a predetermined number of machine cycles to accumulate historical data; and

varying the load inverter frequency during the machines'"'"' cycles in accordance with the historical data to reduce variations in the total power level required by the motors.

77. The method of claim 76, wherein varying the load inverter frequency comprises:

varying the load inverter frequency in accordance with the average value of the historical data accumulated for the plurality of machines at each machine position.