System and method for dual mode control of a turbogenerator/motor

• US 6,410,992 B1
• Filed: 08/23/2000
• Issued: 06/25/2002
• Est. Priority Date: 08/23/2000
• Status: Expired due to Fees

• Current Assignee: Capstone Turbine Corp.
• Original Assignee: Capstone Turbine Corp.
• Inventors: Wacknov, Joel B., Wall, Simon R., Gilbreth, Mark G., Keller, Ken
• Primary Examiner(s): Ponomarenko, Nicholas
• Application Number:
  US09/644,527
• Time in Patent Office: 671 Days
• Field of Search: 290/40.R, 290/40.C, 290/52, 322/20, 322/36, 322/37, 307/70, 307/85, 307/145
• US Class Current: 290/52
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved
• CPC Class Codes: H02P 9/02 Details of the control
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator

Abstract

A method of controlling a permanent magnet turbogenerator/motor includes providing a protected load connected in parallel with the turbogenerator/motor through a pulse width modulated inverter configured in a first operating mode to supply controlled current from the turbogenerator/motor to a utility electrical power source, and selectively connected to the utility electrical power source through an isolation device, monitoring the utility electrical power source, and automatically disconnecting the protected load from the utility electrical power source while reconfiguring the pulse width modulated inverter in a second operating mode to supply controlled voltage to the protected load when a fault is detected in the utility electrical power source. The present invention provides an external or integrated dual mode controller which can be used to provide automatic transitions of a turbogenerator/motor between grid-connected modes where a PWM inverter provides a controlled AC current source to stand-alone modes where the PWM inverter provides a controlled AC voltage source to a protected load. Three phase rotation sequence can be set to positive or negative rotation, or be set to the last measured rotation for the utility grid to enable automatic transitions from stand-alone to grid-connect modes. In addition, the present invention provides for detecting a reference phase angle of the three-phase power provided by a utility grid such that gradual synchronization/resynchronization of a protected parallel connected load can be performed by appropriately controlling the PWM inverter prior to re-connection to the utility grid.

Claims

1. A method of controlling a permanent magnet turbogenerator/motor comprising:

providing a protected load connected in parallel with the turbogenerator/motor through a pulse width modulated inverter configured in a first operating mode to supply controlled current from the turbogenerator/motor to a utility electrical power source, and selectively connected to the utility electrical power source through an isolation device;

monitoring the utility electrical power source; and

automatically disconnecting the protected load from the utility electrical power source by opening the isolation device and reconfiguring the pulse width modulated inverter in a second operating mode to supply controlled voltage to the protected load when a fault is detected in the utility electrical power source.

2. The method of claim 1 wherein monitoring the utility electrical power source comprises monitoring a phase rotation sequence of the utility electrical power source.

3. The method of claim 1 wherein monitoring the utility electrical power source comprises monitoring a phase reference angle of the utility electrical power source.

4. The method of claim 1 wherein monitoring the utility electrical power source comprises detecting loss of power supplied by the utility electrical power source.

5. The method of claim 1 further comprising:

automatically reconfiguring the pulse width modulated inverter to supply controlled current from the turbogenerator/motor when the step of monitoring determines the utility electrical power source is acceptable for reconnection; and

controlling the isolation device to automatically reconnect the protected load to the utility electrical power source.

6. The method of claim 5 wherein the monitoring step includes determining a reference phase angle of the electrical utility power source, the method further comprising controlling the pulse width modulated inverter to synchronize phase angle of the controlled voltage supplied to the protected load with the reference phase angle of the electrical utility power source prior to controlling the isolation device to automatically reconnect the protected load to the utility electrical power source.

7. The method of claim 1 further comprising:

providing utility electrical power to the permanent magnet turbogenerator/motor through the pulse width modulated inverter to start the permanent magnet turbogenerator/motor to achieve self-sustaining operation of the permanent magnet turbogenerator/motor.

8. The method of claim 1 further comprising:

providing an energy storage and discharge system for the pulse width modulated inverter to provide electrical energy to the inverter when utility electrical power is unavailable to start the permanent magnet turbogenerator/motor and during self-sustained operation when the permanent magnet turbogenerator/motor cannot meet an instantaneous load requirement during self-sustained operation.

9. A system for controlling a permanent magnet turbogenerator/motor having an associated protected load, the system comprising:

a controllable isolating device for selectively connecting the protected load in parallel with a utility electrical power source;

an inverter configurable in a first operating mode to supply power from the turbogenerator/motor to the utility electrical power source, and a second operating mode to supply power from the turbogenerator/motor to the protected load; and

a controller in communication with the controllable isolating device and the inverter, the controller selectively monitoring the utility electrical power source to detect a power source fault, opening the isolating device to disconnect the protected load from the utility electrical power source, and automatically transitioning from the first operating mode to the second operating mode to provide power to the protected load.

10. The system of claim 9 further comprising means for monitoring the utility electrical power source to detect a phase rotation sequence of the utility electrical power source.

11. The system of claim 9 further comprising means for monitoring the utility electrical power source to determine a phase reference angle of the utility electrical power source.

12. The system of claim 9 further comprising means for monitoring the utility electrical power source to detect loss of power supplied by the utility electrical power source.

13. The system of claim 9 wherein the controller includes control logic for automatically transitioning from the second operating mode to the first operating mode after determining that the utility electrical power source is acceptable for reconnection and control logic for operating the isolation device to automatically reconnect the protected load to the utility electrical power source.

14. The system of claim 9 further comprising means for determining a reference phase angle of the electrical utility power source, wherein the controller controls the inverter to synchronize phase angle of the controlled voltage supplied to the protected load with the reference phase angle of the electrical utility power source prior to controlling the isolation device to automatically reconnect the protected load to the utility electrical power source.

15. The system of claim 9 wherein the controllable isolation device comprises an electronic switch connected in series with a mechanical switch.

16. The system of claim 15 wherein the electronic switch comprises a thyristor.

17. The system of claim 15 wherein the mechanical switch comprises a motorized circuit breaker.

18. The system of claim 15 wherein the mechanical switch comprises a contactor.

19. The system of claim 9 wherein the controllable isolation device comprises a motorized circuit breaker.

20. The system of claim 9 wherein the controllable isolation device comprises a contactor.

21. The system of claim 9 further comprising:

an energy storage and discharge system in communication with the controller for providing electrical energy to the permanent magnet turbogenerator/motor when utility electrical power is unavailable to start the permanent magnet turbogenerator/motor and/or during self-sustained operation when the permanent magnet turbogenerator/motor cannot meet an instantaneous load requirement during self-sustained operation.

22. A system for controlling a permanent magnet turbogenerator/motor to transition between a grid-connect operating mode in which the permanent magnet turbogenerator/motor is connected in parallel with an electrical utility power grid, and a stand-alone mode in which the permanent magnet turbogenerator/motor is disconnected from the electrical utility power grid, the system comprising:

a first controller having a configurable pulse width modulated inverter operably associated with the permanent magnet turbogenerator/motor, the configurable pulse width modulated inverter for supplying controlled AC current to the electrical utility power grid when operating in the grid-connect operating mode and for supplying controlled voltage from the turbogenerator/motor when operating in the stand-alone operating mode;

an isolating device for controllably connecting a protected load and the first controller to the electrical utility power grid;

a second controller connected to the electrical utility power grid and in communication with the first controller and the isolating device, wherein the second controller monitors the electrical utility power grid to detect loss of grid power and communicates a grid transfer command to the first controller when a loss of grid power is detected such that the first controller transitions the pulse width modulated inverter from the grid-connect operating mode to the stand-alone operating mode and communicates corresponding status information to the second controller, the second controller then controlling the isolating device to disconnect the protected load from the electrical utility power grid.

23. The system of claim 22 further comprising:

an energy storage and discharge system in communication with the first controller to provide electrical energy to the pulse width modulated inverter during transitions from the grid connect operating mode to the stand-alone operating mode.

24. The system of claim 22 wherein the second controller monitors the electrical utility power grid to determine when the power grid is acceptable for reconnection, the second controller communicating a command to the first controller such that the first controller automatically transitions the pulse width modulated inverter from the stand-by operating mode to the grid-connect operating mode and communicates corresponding status information to the second controller, the second controller then controlling the isolating device to reconnect the protected load to the electrical utility power grid.

25. The system of claim 22 wherein the first controller monitors the electrical utility power grid to determine a phase rotation sequence of the power grid.

26. The system of claim 25 wherein the first controller controls the pulse width modulated inverter to provide the same phase rotation sequence to the protected load as the electrical utility power grid prior to transitioning between the stand-by and grid-connect operating modes.

27. The system of claim 22 wherein the second controller monitors the electrical utility power grid to determine a phase reference angle of the power grid and communicates this to the first controller.

28. The system of claim 27 wherein the first controller controls the pulse width modulated inverter to provide the same phase reference angle to the protected load as the electrical utility power grid prior to transitioning between the stand-by and grid-connect operating modes.

29. A method of transitioning a permanent magnet turbogenerator/motor based electric power generation system between operating modes, one operating mode being a grid connect mode in which the permanent magnet turbogenerator/motor based electric power generation system is connected in parallel with an electric utility power grid, and the other operating mode being a stand-alone mode in which the permanent magnet turbogenerator/motor based electric power generation system is not connected in parallel with an electric utility power grid, the method comprising:

when the permanent magnet turbogenerator/motor based electric power generation system is operating in grid connect mode, monitoring the electric utihty power grid to detect a fault, and opening an isolation device to automatically disconnect the permanent magnet turbogenerator/motor based electric power generation system from the electric utility power grid; and

when the permanent magnet turbogenerator/motor based electric power generation system is operating in stand-alone mode, monitoring the electric utility power grid to determine when reconnection is acceptable, and closing the isolation device to automatically reconnect the permanent magnet turbogenerator/motor based electric power generation system in parallel with the electric utility power grid.

30. The method of claim 29 further comprising:

monitoring the electric utility power grid to determine a phase rotation sequence; and

synchronizing phase rotation sequence of the permanent magnet turbogenerator/motor based electric power generation system with the phase rotation sequence of the electric utility power grid prior to transitioning between operating modes.

31. The method of claim 29 further comprising:

monitoring the electric utility power grid to determine a phase reference angle; and

synchronizing phase reference angle of the permanent magnet turbogenerator/motor based electric power generation system with the phase reference angle of the electric utility power grid prior to transitioning between operating modes.

32. The method of claim 29 further comprising:

when the permanent magnet turbogenerator/motor based electric power generation system is operating in stand-alone mode, modifying phase rotation sequence of power generated by the permanent magnet turbogenerator/ motor based electric power generation system based on a received phase rotation sequence command.

33. A system for controlling a permanent magnet turbogenerator/motor to transition between a grid-connect operating mode in which the permanent magnet turbogenerator/motor is connected in parallel with an electrical utility power grid, and a stand-alone mode in which the permanent magnet turbogenerator/motor is, disconnected from the electrical utility power grid, the system comprising:

an isolating device for controllably connecting and disconnecting a protected load and the turbogenerator/motor to the electrical utility power grid;

a controller in communication with the controllable isolating device, the controller including a configurable pulse width modulated inverter operably associated with the permanent magnet turbogenerator/motor for supplying power to the electrical utility power grid when operating in the grid-connect operating mode and for supplying power from the turbogenerator/motor when operating in the stand-alone operating mode;

wherein the controller monitors the electrical utility power grid to detect loss of grid power, automatically transitions the pulse width modulated inverter from the grid-connect operating mode to the stand-alone operating mode, and controls the isolating device to disconnect the protected load from the electrical utility power grid.

34. The system of claim 33 wherein the controller monitors the electric utility power grid to determine a phase rotation sequence and controls the pulse width modulated inverter to synchronize phase rotation sequence of the turbogenerator/motor with the phase rotation sequence of the electric utility power grid prior to transitioning between operating modes.

35. The system of claim 33 wherein the controller monitors the electric utility power grid to determine a phase reference angle and controls the pulse width modulated inverter to synchronize phase reference angle of the turbogenerator/motor with the phase reference angle of the electric utility power grid prior to transitioning between operating modes.

36. The system of claim 33 wherein the controller modifies the rotation sequence of power generated by the turbo generator/motor based on a received phase rotation sequence command.

37. The system of claim 36 wherein the controller modifies the rotation sequence based on a received phase rotation sequence command only if the turbogenerator/motor is operating in stand-alone mode.

38. The system of claim 36 wherein the controller controls the pulse width modulated inverter to provide a positive phase rotation sequence for the power generated by the turbogenerator/motor.

39. The system of claim 36 wherein the controller controls the pulse width modulated inverter to provide a negative phase rotation sequence for the power generated by the turbogenerator/motor.

40. The system of claim 33 wherein the controller operates with resynchronization to resynchronize power generated by the turbogenerator/motor and the electric utility grid when transitioning from the stand-alone operating mode to the grid-connect operating mode and without stop and automatic restart functions such that the turbogenerator/motor does not stop and then automatically restart during a transition between operating modes.

41. The system of claim 33 wherein the controller operates without resynchronization and without stop and automatic restart functions.

42. The system of claim 33 wherein the controller operates without resyncrhonization and with stop and automatic restart functions.

43. A method for controlling a permanent magnet turbogenerator/motor to automatically transition between a grid-connect operating mode in which the turbogenerator/motor is connected in parallel with an electrical utility power grid, and a stand-alone mode in which the permanent magnet turbogenerator/motor is disconnected from the electrical utility power grid, the method comprising:

monitoring the electrical utility power grid to detect a rotation sequence for power generated by the electrical utility; and

controlling the turbogenerator/motor to synchronize a rotation sequence of the turbogenerator/motor with the rotation sequence of the power generated by the electrical utility prior to transitioning between the grid-connect operating mode and the stand-alone operating mode.

44. The method of claim 43 further comprising:

monitoring the electrical utility power grid to determine a phase reference angle; and

synchronizing the phase reference angle of power generated by the turbogenerator/motor with the determined phase reference angle of the electrical utility power grid.

45. The method of claim 43 wherein the step of controlling comprises controlling the turbogenerator/motor to provide a positive rotation sequence.

46. The method of claim 43 wherein the step of controlling comprises controlling the turbogenerator/motor to provide a negative rotation sequence.

47. The method of claim 43 further comprising:

receiving a rotation sequence command; and

controlling the rotation sequence of the turbogenerator/motor based on the rotation sequence command.

48. The method of claim 47 wherein the step of controlling the rotation sequence is performed only when the turbogenerator/motor is operating in the stand-alone mode.