Turbogenerator power control system

• US 6,265,786 B1
• Filed: 10/27/1998
• Issued: 07/24/2001
• 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., Lampe, Steven W., Peticolas, Brian W., Edelman, Edward C.
• Primary Examiner(s): Thorpe, Timothy S.
• Assistant Examiner(s): Gartenberg, Ehud
• Application Number:
  US09/181,213
• Time in Patent Office: 1,001 Days
• Field of Search: 318/723, 318/801, 290/46, 290/52, 74/41, 417/44.1, 417/53
• US Class Current: 290/52
• 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
• CPC Class Codes: Y10T 74/18182 Pump jack type

Abstract

A power control system for a turbogenerator which provides electrical power to pump-jack oil well. When the induction motor of a pump-jack is powered by three-phase utility power, the speed of the shaft varies only slightly over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This 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 pumping cycle, the processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole pump rods and oil, and to rotationally accelerate and decelerate 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 pumping power to be precisely controlled, resulting in a constant turbogenerator power requirement.

Claims

1. A system, comprising:

a turbogenerator;

a cyclic motion machine driven by an electric motor;

a low frequency inverter powered by said turbogenerator, said inverter connected to said electric motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said inverter during each cycle of said cyclic motion machine to provide a generally constant power level to said electric motor.

2. The system of claim 1, wherein said controller further includes:

a high frequency inverter synchronously connected to said turbogenerator;

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

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

3. The system of claim 1 wherein said controller includes:

a bridge rectifier connected to said turbogenerator to convert high frequency three-phase electrical power produced by said turbogenerator into direct current electrical power;

a direct current bus electrically connecting said bridge rectifier with said low frequency inverter; and

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

4. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well having axial and rotational masses, and said processor comprises:

a processor varying the frequency of said low frequency inverter to control the power provided to said electric motor to accelerate and decelerate said axial and rotational masses of said pump-jack oil well.

5. The system of claim 4 wherein said processor comprises:

a processor varying the frequency of said low frequency inverter to minimize variations in the power requirements of said electric motor driving said pump-jack oil well over each operating cycle of said pump-jack oil well.

6. The system of claim 4 wherein said processor comprises:

a processor varying the frequency of said low frequency inverter to control the power provided to said electric motor to match the oil pumping rate of said pump-jack oil well with the rate at which oil seeps into the oil well.

7. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous frequency of said low frequency inverter over each operating cycle of said pump-jack oil well.

8. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous voltage of said low frequency inverter over the operating cycle of said pump-jack oil well.

9. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous current of said low frequency inverter over each operating cycle of said pump-jack oil well.

10. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter over each 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.

11. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the voltage of said low frequency inverter over each operating cycle of said pump-jack oil well to control the slip of said electric motor.

12. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter to control the instantaneous pumping work performed by said pump-jack oil well and the instantaneous pumping work extracted from said pump-jack oil well.

13. The system of claim 2 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter to maintain the sum of the instantaneous pumping energy required by said pump-jack oil well, the instantaneous pumping energy produced by said pump-jack oil well, the instantaneous kinetic energy extracted from said pump-jack oil well, and the instantaneous kinetic energy inserted into said pump-jack oil well to be substantially constant over each operating cycle of said pump-jack oil well.

14. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well having axial and rotational masses, and said processor comprises:

a processor varying the frequency of said low frequency inverter to control the power provided to said electric motor to accelerate and decelerate said axial and rotational masses of said pump-jack oil well to control the power requirements of said electric motor.

15. The system of claim 14 wherein said processor comprises:

a processor varying the frequency of said low frequency inverter to minimize variations in the power requirements of said electric motor over each operating cycle of said pump-jack oil well.

16. The system of claim 14 wherein said processor comprises:

a processor varying the frequency of said low frequency inverter to control the power provided to said electric motor to match the oil pumping rate of said pump-jack oil well with the rate at which oil seeps into the oil well.

17. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous frequency of said low frequency inverter over each operating cycle of said pump-jack oil well.

18. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous voltage of said low frequency inverter over each operating cycle of said pump-jack oil well.

19. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the instantaneous current of said low frequency inverter over each operating cycle of said pump-jack oil well.

20. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter over each 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.

21. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the voltage of said low frequency inverter over each operating cycle of said pump-jack oil well to control the slip of said electric motor.

22. The system of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter to control the instantaneous pumping work performed by said pump-jack oil well and the instantaneous pumping work extracted from said pump-jack oil well.

23. The combination of claim 3 wherein said cyclic motion machine is a pump-jack oil well, and said processor comprises:

a processor varying the frequency of said low frequency inverter to maintain the sum of the instantaneous pumping energy required by said pump-jack oil well, the instantaneous pumping energy produced by said pump-jack oil well, the instantaneous kinetic energy extracted from said pump-jack oil well, and the instantaneous kinetic energy inserted into said pump-jack oil well to be substantially constant over each operating cycle of said pump-jack oil well.

24. A system, comprising:

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

an electric induction motor supplied with electrical power by said low frequency inverter;

a pump-jack oil well driven by said electric induction motor; and

a controller controlling said turbogenerator and said inverter to vary the frequency of said inverter to maintain a generally constant power output level for said turbogenerator.

25. The system of claim 24 wherein said controller comprises:

one or more primary control loops controlling said turbogenerator.

26. The system of claim 25 wherein said controller comprises:

a turbine exhaust gas temperature control loop controlling said turbogenerator.

27. The system of claim 25 wherein said controller comprises:

a turbogenerator speed control loop controlling said turbogenerator.

28. The system of claim 25 wherein said controller comprises:

a power control loop controlling said turbogenerator.

29. The system of claim 25 wherein said controller comprises:

a turbine exhaust gas temperature control loop and a turbogenerator speed control loop controlling said turbogenerator.

30. The system of claim 25 wherein said controller comprises:

a turbine exhaust gas temperature control loop and a power control loop controlling said turbogenerator.

31. The system of claim 25 wherein said controller comprises:

a power control loop and a turbogenerator speed control loop controlling said turbogenerator.

32. The system of claim 25 wherein said controller comprises:

a turbine exhaust gas temperature control loop, a turbogenerator speed control loop, and a power control loop, said loops controlling said turbogenerator.

33. The system of claim 32 wherein said controller comprises:

a turbine exhaust gas temperature control loop and a turbogenerator speed control loop controlling said controller to regulate fuel input to said gas turbine combustor.

34. The system of claim 33, further comprising:

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

35. The system of claim 32 wherein said controller further comprises:

a turbogenerator speed command control loop and a turbogenerator power command control loop controlling said turbogenerator.

36. The system of claim 32 wherein said controller further comprises:

a maximum turbogenerator speed control loop and a maximum turbine exhaust gas temperature control loop controlling said turbogenerator.

37. The system of claim 24 wherein said pump-jack oil well includes a down hole rod string, and said controller further comprises:

a controller monitoring the phase relationship of the voltage and current of said electric induction motor to measure the resonant velocities of the down hole rod string and to damp said resonances with modulations in the torque of said electric induction motor.

38. The system of claim 24 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 low frequency inverter; and

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

39. The system of claim 38 wherein said processor further comprises:

a plurality of primary control loops controlling said turbogenerator.

40. The system of claim 39 wherein said processor comprises:

a turbine exhaust gas temperature control loop controlling said turbogenerator.

41. The system of claim 39 wherein said processor comprises:

a turbogenerator speed control loop controlling said turbogenerator.

42. The system of claim 39 wherein said processor comprises:

a power control loop controlling said turbogenerator.

43. The system of claim 39 wherein said processor comprises:

a turbine exhaust gas temperature control loop and a turbogenerator speed control loop controlling said turbogenerator.

44. The system of claim 39 wherein said primary control loops comprise:

a turbine exhaust gas temperature control loop and a power control loop controlling said turbogenerator.

45. The system of claim 39 wherein said primary control loops include a power control loop and a turbogenerator speed control loop controlling said turbogenerator.

46. The system of claim 39 wherein said primary control loops comprise:

a turbine exhaust gas temperature control loop, a turbogenerator speed control loop, and a power control loop, said loops controlling said turbogenerator.

47. The system of claim 46 wherein said controller comprises:

a turbine exhaust gas temperature control loop and turbogenerator speed control loop controlling said controller to regulate fuel output to said gas turbine combustor.

48. The system of claim 47, wherein said controller further comprises:

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

49. The system of claim 46 wherein said controller further comprises:

a turbogenerator speed command control loop and a turbogenerator power command control loop controlling said turbogenerator.

50. The system of claim 46 wherein said controller further comprises:

a maximum turbogenerator speed control loop and a maximum turbine exhaust gas temperature control loop controlling said turbogenerator.

51. A method of controlling a system including a turbogenerator and a cyclical motion machine driven by an electric motor, comprising the steps of:

providing electrical power from said turbogenerator to said electric motor; and

controlling said turbogenerator and said cyclical motion machine to supply a generally constant level of power to said electric motor and maintain a generally constant power output level for said turbogenerator.

52. 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; and

connecting a controller to the load inverter to control the power provided to the motor by varying the load inverter frequency, the controller varying the load inverter frequency over each machine cycle to reduce variations in the power level required by the motor.

53. The method of claim 52, wherein connecting the controller to the load inverter to control the power provided to the motor by 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.

54. The method of claim 53, 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 over periods of reduced machine load during each machine cycle to insert kinetic energy into the machine and reduce variations in the power level required by the motor.

55. The method of claim 52, wherein connecting a controller to the load inverter to control the power provided to the motor by varying the load inverter frequency comprises:

connecting a controller to the load inverter to control the power provided to the motor by varying the load inverter frequency and the load inverter voltage.

56. The method of claim 55, wherein connecting a controller to the load inverter to vary the load inverter frequency and the load inverter voltage comprises:

connecting a controller to the load inverter to control the power provided to the motor by varying the load inverter voltage approximately with the square root of the load inverter frequency.

57. The method of claim 52, further comprising:

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

58. The method of claim 57, wherein connecting a controller to the load inverter to control the power provided to the motor by varying the load inverter frequency further comprises:

connecting the controller to the turbogenerator to control the speed of the turbogenerator.

59. The method of claim 58, wherein connecting the controller to the turbogenerator to control the speed of the turbogenerator comprises:

connecting the controller to the turbogenerator to maintain the speed of the turbogenerator at a generally constant level.

60. The method of claim 59, wherein connecting the controller to the turbogenerator to maintain the speed of the turbogenerator at a generally constant level comprises:

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

61. The method of claim 58, wherein connecting the controller to the turbogenerator to control the speed of the turbogenerator comprises:

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

62. The method of claim 61, wherein connecting the controller to the turbogenerator to maintain the speed of the turbogenerator generally at a level required to maintain the average frequency of the load inverter generally 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.

63. The method of claim 52, wherein connecting the controller to the load inverter to vary the load inverter frequency comprises:

connecting the controller to the load inverter to maintain the average frequency of the load inverter generally at the frequency of a utility grid connected to the load inverter.

64. The method of claim 52, wherein the machine is an oil well pump-jack, and connecting the controller to the load inverter to vary the load inverter frequency comprises:

connecting the controller to the load inverter to maintain 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.

65. The method of claim 58, further comprising:

connecting an energy storage device to the inverter; and

connecting the controller to the load inverter to transfer excess energy produced by the machine from the motor to the energy storage device.