MODULATION CONTROL OF POWER GENERATION SYSTEM

• US 20080067982A1
• Filed: 09/20/2006
• Published: 03/20/2008
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: Pratt & Whitney Canada Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Pratt & Whitney Canada Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: DOOLEY, Kevin Allan
• Granted Patent: US 7,439,713 B2
• Time in Patent Office: Days
• US Class Current: 322/22
• CPC Class Codes: H02P 2101/10 for water-driven turbines
• CPC Class Codes: H02P 2101/30 for aircraft
• CPC Class Codes: H02P 9/34 using magnetic devices with controllable degree of saturation in combination with controlled discharge tube or controlled semiconductor device

Abstract

Methods and apparatuses are disclosed for producing current with a desired output frequency from one or more fixed or variable speed alternators by varying a saturation level of a portion of the alternator(s) based on a output frequency desired, and preferably then rectifying the output to produce a desired electrical output which may be provided as direct current or alternating current to a suitable load.

Claims

1. An apparatus comprising:

a first alternator and a second alternator, each alternator having a rotor and stator, the stator having a plurality of rotor magnetic circuits co-operatively defined between the stator and rotor and a plurality of secondary magnetic circuits, each rotor magnetic circuit encircling a first portion of at least one power winding of the stator, each secondary magnetic circuit encircling a second portion of the power winding disposed outside the rotor magnetic circuits, at least one control winding associated with said secondary magnetic circuits such that a saturating control current through the control winding magnetically saturates at least a portion of said secondary magnetic circuits distinct from the rotor magnetic circuits, the secondary magnetic circuits being paired such that in one secondary magnetic circuit the associated control winding and stator winding second portion are wound around the stator in a same direction while in the other secondary magnetic circuit the associated control winding and stator winding second portion are wound around the stator in opposite directions;

a controlled current source assembly connected to said at least one control winding of each alternator and adapted to provide a periodic DC control current flow thereto, the DC current flow having a maximum amplitude above a saturation level required to saturate said portions of said secondary magnetic circuits;

a first rectifier for converting alternating current from the at least one power winding of said first alternator to a direct current;

a second rectifier for converting alternating current from the at least one power winding of said second alternator direct current; and

a combiner circuit for combining direct current from said rectifiers into an alternating current output.

2. The apparatus as defined in claim 1 wherein the controlled current source assembly provides a variable amplitude DC control current flow to each alternator and which varies out-of-phase with the current provided to the other.

3. The apparatus as defined in claim 1, wherein the controlled current source assembly provides an intermittent DC control current flow to each alternator corresponding to one half-cycle of said alternating current output.

4. The apparatus as defined in claim 1, wherein the controlled current source assembly provides a DC control current flow which varies in a half-sinusoidal pattern.

5. The apparatus as defined in claim 1, wherein a frequency of the periodic DC control current flow is independent of a rotational speed of the respective alternator.

6. The apparatus as defined in claim 1, wherein said first and said second alternators comprise a single machine having a common magnetic rotor, said stator of each alternator being defined as substantially independent sectors of a stator assembly of the machine, said stators being substantially magnetically isolated from one another within the stator assembly, the power windings of said stators being electrically isolated from one another.

7. The apparatus as defined in claim 1, wherein each secondary magnetic circuit is disposed entirely within its respective stator.

8. The apparatus as defined in claim 1, wherein the stator comprises two distinct portions, and wherein the rotor magnetic circuits and secondary magnetic circuits are defined in different of said stator portions.

9. The apparatus as defined in claim 1, wherein the stator has a plurality of radial first slots in which said first portions of the power winding are disposed, and wherein each said first magnetic circuits encircle at least one of said first slots.

10. The apparatus as defined in claim 9, wherein the stator has a plurality of second slots in which said second portions of the power winding and a portion of the control winding are disposed, and wherein each said secondary magnetic circuits encircles one of said second slots.

16. The apparatus as claimed in claim 1 further comprising a feedback monitor circuit adapted to monitor said alternating current output, the monitor communicating with at least one of the saturation control apparatus and the DC-to-AC conversion circuitry.

11. An apparatus comprising:

at least one alternator drivingly connected to a prime mover to produce an alternator alternating current, the alternator having a rotor, a stator assembly and a saturation apparatus, the stator assembly having at least one stator winding for providing said alternator alternating current, the stator winding having at least a pair of legs serially connected with one another, the legs spaced apart circumferentially from one another relative to the stator assembly, the rotor and stator assembly co-operating to define at least two rotor magnetic circuits for conducting rotor magnetic flux, one of the rotor magnetic circuits encircling a first portion of one of said legs of the stator winding and another one of the rotor magnetic circuits encircling a first portion of the other of said legs of the stator winding, the stator assembly defining at least a pair of secondary magnetic circuits for conducting magnetic flux, one of the secondary magnetic circuits encircling a second portion of one of said legs of the stator winding and another one of the secondary magnetic circuits encircling a second portion of the other of said legs of the stator winding, the secondary magnetic circuits being remote from the rotor magnetic circuits, the saturation apparatus associated with at least a portion of each secondary magnetic circuit, said at least a portion of each secondary magnetic circuit being remote from the rotor magnetic circuits, the saturation apparatus adapted to selectively magnetically saturate said portion of each secondary magnetic circuit at a selected frequency, the saturation apparatus adapted to magnetically saturate one of the secondary magnetic circuits in the same direction as magnetic flux circulating that secondary magnetic circuit while magnetically saturating another one of secondary magnetic circuits in the direction opposite to magnetic flux circulating that secondary magnetic circuit;

AC-to-DC conversion circuitry connected to the stator winding adapted to convert the alternator alternating current into direct current; and

DC-to-AC conversion circuitry connected to the AC-to-DC conversion circuitry and adapted to convert the direct current into an alternating current output having an output frequency proportional to the selected frequency.

12. The apparatus as claimed in claim 11, wherein the stator includes a plurality of peripheral slots, and wherein said first portions of the legs of the stator winding are disposed within different said slots.

13. The apparatus as claimed in claim 11, wherein the selected frequency is independent of a rotational speed of the alternator.

14. The apparatus as claimed in claim 11, wherein the prime mover drives the alternator at a variable speed, and wherein the selected frequency is substantially fixed.

15. The apparatus as claimed in claim 11, wherein the desired frequency is lower than a rotation speed of the alternator.

17. The apparatus as claimed in claim 11, wherein the stator assembly comprises a first stator defining the rotor magnetic circuits and a second stator defining the secondary magnetic circuits.

18. An apparatus comprising:

at least one alternator drivingly connected to a prime mover to produce an alternator alternating current, the alternator having a rotor and a stator assembly having at least one stator winding for providing said alternator alternating current, the stator winding having at least a pair of legs serially connected with one another, the legs spaced apart circumferentially from one another relative to the stator assembly, the rotor and stator assembly co-operating to define at least two rotor magnetic circuits for conducting rotor magnetic flux, one of the rotor magnetic circuits encircling a first portion of one of said legs of the stator winding and another one of the rotor magnetic circuits encircling a first portion of the other of said legs of the stator winding, the stator assembly defining at least a pair secondary magnetic circuits for conducting magnetic flux, one of said secondary magnetic circuits encircling a second portion of one of said legs of the stator winding and the other one of said secondary magnetic circuits encircling a second portion of the other of said legs of the stator winding, the secondary magnetic circuits being remote from the rotor magnetic circuits, the secondary magnetic circuits having a saturation apparatus including at least one control winding wound around at least a portion of the secondary magnetic circuits, said at least a portion of the secondary magnetic circuits being remote from the rotor magnetic circuits, the control winding adapted to magnetically saturate said portion of the secondary magnetic circuits when a saturation threshold current passes through the control winding, wherein one of the secondary magnetic circuits has its control winding wound in a same direction as the second portion of the stator winding leg associated therewith, and wherein the other one of the secondary magnetic circuits has its control winding wound in an opposite direction relative to the second portion of the stator winding leg associated therewith;

a controlled current source for providing to the control winding a variable amplitude current having a selected frequency and a maximum amplitude of at least said saturation threshold current;

AC-to-DC conversion circuitry connected to the stator winding and adapted to convert the alternator alternating current into direct current; and

DC-to-AC conversion circuitry connected to the AC-to-DC conversion circuitry and adapted to convert the direct current into an alternating current output having an output frequency proportional to the selected frequency.

19. The apparatus as claimed in claim 18, wherein the current provided to the control winding is direct current varying in amplitude according to said desired frequency.

20. The apparatus as claimed in claim 19, wherein the amplitude varies in a half-sinusoidal manner.

21. The apparatus as claimed in claim 18, wherein the control winding has a multiple turns ratio relative to said second portion of the respective legs of the stator winding.

22. The apparatus as claimed in claim 18, wherein the stator includes a plurality of peripheral slots, and wherein said first portions of the legs of the stator winding are disposed within different said slots.

23. The apparatus as claimed in claim 18, wherein the selected frequency is independent of a rotational speed of the alternator.

24. The apparatus as claimed in claim 18, wherein the prime mover drives the alternator at a variable speed, and wherein the selected frequency is substantially fixed.

25. The apparatus as claimed in claim 18, wherein the selected frequency is lower than a raw output frequency of the alternator.

26. The apparatus as claimed in claim 18, wherein the selected frequency is a complex frequency.

27. The apparatus as claimed in claim 18, wherein the output frequency is substantially equal to the selected frequency.

28. The apparatus as claimed in claim 18, wherein the output frequency is substantially one-half of the selected frequency.

29. The apparatus as claimed in claim 18, further comprising a feedback monitor circuit adapted to monitor said alternating current output, the monitor communicating with at least one of the controlled current source and the DC-to-AC conversion circuitry.

30. The apparatus as claimed in claim 18, wherein the stator assembly comprises a first stator defining the rotor magnetic circuits and a second stator defining the secondary magnetic circuits.

31. The apparatus as claimed in claim 18, wherein the DC-to-AC conversion circuitry includes a switching apparatus driven at the selected frequency.

32. The apparatus as claimed in claim 18, wherein said at least one alternator comprises at least two said alternators each having a said controlled current source and a said AC-to-DC conversion circuitry, and wherein the DC-to-AC conversion circuitry sums the direct currents received from the AC-to-DC conversion circuitry associated with each alternator to provide said alternating current output.

33. The apparatus as claimed in claim 32, wherein the alternators are driven at substantially the same speed.

34. The apparatus as claimed in claim 33, wherein the alternators have a common rotor and the respective stators are provided in non-overlapping sectors of a common stator body.

35. The apparatus as claimed in claim 33, wherein the alternators are driven by the same prime mover.

36. The apparatus as claimed in claim 18, wherein each secondary magnetic circuit circulates only one leg of the stator winding.

37. An apparatus comprising:

an alternator having a rotor, a stator assembly and a saturation apparatus, the stator assembly having at least one stator winding, the winding having at least a pair of legs serially connected with one another, the legs spaced apart circumferentially from one another relative to the stator, the rotor and stator assembly co-operating to define at least two rotor magnetic circuits for conducting rotor magnetic flux, one of the rotor magnetic circuits encircling a first portion of one of said legs of the stator winding and another one of the rotor magnetic circuits encircling a first portion of the other of said legs of the stator winding, the stator assembly defining at least two secondary magnetic circuits for conducting magnetic flux, one of the secondary magnetic circuits encircling a second portion of one of said legs of the stator winding and another one of the secondary magnetic circuits encircling a second portion of the other of said legs of the stator winding, the secondary magnetic circuits being remote from the rotor magnetic circuits, the saturation apparatus adapted to magnetically saturate at least a portion of each secondary magnetic circuit, said at least a portion of each secondary magnetic circuit being remote from the rotor magnetic circuits, the saturation apparatus adapted to magnetically saturate one of the secondary magnetic circuits in the same direction as magnetic flux circulating that secondary magnetic circuit while magnetically saturating the other one of secondary magnetic circuits in the direction opposite to magnetic flux circulating that secondary magnetic circuit; and

a rectifier arranged to convert alternating current from the stator winding into direct current.

38. The apparatus as claimed in claim 37, wherein the saturation apparatus is adapted to magnetically saturate said at least a portion of each secondary magnetic circuit at a substantially constant saturation level.

39. An apparatus for a generating alternating current comprising:

at least one alternator having a stator with at least one stator winding, the stator defining at least two rotor magnetic circuits and at least two secondary magnetic circuits separate from the rotor and the rotor magnetic circuits, the stator winding having first portions thereof encircled only by the rotor magnetic circuits and second portions thereof encircled only by the secondary magnetic circuits;

means for magnetically saturating at least a portion of respective pairs of secondary magnetic circuits in opposite relative directions to thereby regulate alternator output while leaving the rotor magnetic circuits un-saturated;

a control apparatus adapted to control said means to selectively control a saturation level according to a selected pattern;

a rectifier to convert alternating current from the stator winding into a direct current; and

an inverter for converting direct current from the rectifier into alternating current output having an output pattern proportional to said selected pattern.

40. The controller as defined in claim 39, further comprising:

means for monitoring at least one of a deviation of an amplitude and a deviation of a frequency of said alternating current output relative to a reference signal; and

means for varying operation of the control apparatus to reduce said deviation.

41. A method of producing alternating current in a power generating system having at least first and a second alternators each having a stator comprising at least one power winding and at least one control winding, each power winding having a plurality of first portions associated with a plurality of rotor magnetic circuits and a plurality of second portions associated with a plurality of secondary magnetic circuits isolated from the rotor magnetic circuits, each control winding wound around at least a portion of each secondary magnetic circuit said portion of each secondary magnetic circuit being remote from the rotor magnetic circuits, wherein for each secondary magnetic circuit which has its control winding wound in a same direction as the second portion of the stator winding associated therewith there is another secondary magnetic circuit which as has its control winding wound in an opposite direction relative to the second portion of the stator winding associated therewith, said method comprising the steps of:

driving said first and said second alternators to induce alternating current flow in said power windings;

varying in amplitude a control current flow in said control windings of each alternator according to a selected pattern, at least a portion of said selected pattern having a sufficient current amplitude to magnetically saturate said portions of the secondary magnetic circuits to thereby control an amplitude of said induced alternating current flow in the power windings;

converting current flow from the power windings of each alternator into a direct current; and

combining said direct currents of each alternator to provide an alternating current output having a pattern proportional to the selected pattern.

42. The method as defined in claim 41 further comprising:

monitoring a deviation of an instantaneous amplitude of said alternating current output from a reference amplitude; and

varying at least one of an amplitude characteristic and a frequency characteristic of the selected pattern to reduce said deviation.

43. A method for providing alternating current, the method comprising the steps of:

connecting an alternator to a load system, the alternator having a rotor and a stator assembly with at least one stator winding, the stator winding having at least a pair of serially-connected legs spaced apart circumferentially from one another relative to the stator assembly, the legs each having respective first and second portions;

rotating the rotor relative to stator assembly to circulate rotor magnetic flux through the stator along respective first magnetic paths around each of said first portions said legs of the stator winding to induce an alternating current flow in the stator winding, said induced current in the stator winding inducing a secondary magnetic flux flow in the stator assembly in respective second magnetic paths around each of said second portions of said legs of the stator winding, the second magnetic paths defined wholly within the stator assembly and separately from the first magnetic path;

magnetically saturating and de-saturating at a desired frequency at least two portions of the stator assembly remote from the first magnetic path, said stator assembly portions comprising at least a portion of a corresponding one of said second magnetic paths and thereby conducting a said secondary magnetic flux flow therethrough, wherein one of said at least two stator assembly portions is instantaneously saturated in a same direction as secondary magnetic flux flow therethrough while the other one of said stator assembly portions is instantaneously saturated in an direction opposite to secondary magnetic flux flow therethrough;

rectifying the induced alternating current into direct current, the direct current having a cyclical component with a frequency proportional to said desired frequency; and

changing the direct current into an alternating current output having a frequency proportional to said desired frequency.

44. The method as defined in claim 43, wherein the step of connecting an alternator further comprises connecting a second said alternator in parallel with said alternator, and wherein the steps of rotating, magnetically saturating and de-saturating and rectifying are applied to both alternators, and wherein the step of changing includes summing said direct currents obtained from each alternator.

45. The method as defined in claim 44, wherein the step of magnetically saturating and de-saturating the alternators is performed so that the direct current obtained from one alternator provides a half-cycle portion of the alternating current output and the direct current obtained from the other alternator provides a different a half-cycle portion of the alternating current output.

46. The method as defined in claim 45, wherein one half-cycle portion is a positive current half-cycle portion and one half-cycle portion is a negative current half-cycle portion.

47. The method as defined in claim 43, further comprising the steps of

determining an error between the alternating current output and a reference signal, and

modifying at least one of a magnetic saturation amplitude and said desired frequency to reduce said error.

48. A method of generating alternating current output comprising the steps of:

driving an alternator to produce electricity corresponding to a positive half of an output AC cycle;

driving a second alternator to produce electricity corresponding to a negative half of the output AC cycle;

rectifying the respective alternator outputs; and

summing the alternator outputs to provide the alternating current output.

49. The method of claim 48, wherein only one of the alternators produces said electricity at a given point in time.

50. The method of claim 48, wherein the step of summing comprises the step of closing at least one switch and opening another switch to connect one of said alternators to a load while disconnecting the other of said alternators.