PRODUCING A PHASOR REPRESENTATION OF AN ELECTRICAL ENTITY IN A MULTIPHASE AC ELECTRIC POWER SYSTEM

• US 20090312967A1
• Filed: 08/02/2006
• Published: 12/17/2009
• Est. Priority Date: 08/02/2006
• Status: Abandoned Application

• Current Assignee: Ziwen Yao
• Original Assignee: Ziwen Yao
• Inventors: Yao, Ziwen
• Application Number:
  US12/376,055
• Publication Number:
  US 20090312967A1
• Time in Patent Office: Days
• US Class Current: 702/60
• CPC Class Codes: G01R 29/18 Indicating phase sequence; Indicating synchronism
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/22 Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units

Abstract

A phasor representation of an electrical entity at a geographical location in a multiple phase AC electric power system is produced by receiving a synchronization signal from a remote source, producing a sampling time signal in response to the synchronization signal and a local reference time signal, and producing samples representing an amount of the entity in respective ones of the phases in the AC power system in response to the sampling time signal and the electrical entity in respective ones of the phases in the AC power system. A transformation is performed on the samples to produce a two-axis rotating reference frame representation of the electrical entity in a two-axis rotating reference frame. For each sample, a representation of a sampling time associated with the sample is produced. The two-axis rotating reference frame representation and the representation of the sampling time comprise the phasor representation.

Claims

1. An apparatus for producing a first phasor representation of an electrical

entity at a geographical location in a multiple phase AC electric power system, the apparatus comprising:

a receiver operably configured to receive a synchronization signal from a remote source;

a local reference time signal generator operably configured to generate a local reference time signal;

a sampling time signal generator operably configured to produce a sampling time signal in response to said synchronization signal and said local reference time signal;

a sampling circuit operably configured to produce samples representing an amount of said electrical entity in respective ones of said phases in said AC power system in response to said sampling time signal and said entity in respective ones of said phases in said AC power system;

a processor operably configured to perform a transformation on said samples to produce a two-axis rotating reference frame representation of said electrical entity in a two-axis rotating reference frame;

a time stamp generator operably configured to produce time stamps representing time at which respective said samples are taken by said sampling circuit;

wherein said two-axis rotating reference frame representation and said time stamp comprise said first phasor representation.

2. The apparatus of claim 1 wherein said receiver is operably configured to receive a synchronization signal that is also received by at least one other apparatus operable to produce a second phasor representation of an electrical entity at a different geographical location in said multiple phase AC electric power system.

3. The apparatus of claim 1 wherein said receiver is operably configured to receive a wirelessly transmitted synchronization signal.

4. The apparatus of claim 3 wherein said receiver is operably configured to receive a global positioning system (GPS) signal from a GPS system.

5. The apparatus of claim 1 wherein said sampling time signal generator comprises:

a) a counter incremented in response to said local reference time signal;

b) a circuit operably configured to determine a difference in counts between said counter incremented by said local reference time signal and a counter associated with said synchronization signal, in response to receipt of said synchronization signal;

c) a circuit operably configured to add to a count value produced by said counter incremented by said local reference time signal, a fraction of said difference in counts, to produce a sample count value; and

d) a circuit operably configured to cause a sample of said electrical entity to be produced when said sample count value satisfies a criterion.

6. The apparatus of claim 1 wherein said processor is operably configured to perform a Blondel-Park Transformation on said sampled signals.

7. The apparatus of claim 6 wherein said processor is operably configured to set transformation coefficients of said Blondel-Park Transformation in response to said sampling time signal and a frequency value representing a rotation frequency of said two-axis rotating reference frame.

8. The apparatus of claim 1 wherein said two-axis rotating reference frame representation comprises a direct axis component and a quadratic axis component.

9. The apparatus of claim 1 wherein said two-axis rotating reference frame representation comprises a modulus component and an angle component.

10. The apparatus of claim 1 wherein said processor is operably configured to cancel contributions of harmonics included in said two-axis rotating reference frame representation.

11. The apparatus of claim 10 wherein said processor is operably configured to store successive ones of said two-axis rotating reference frame representation and sum particular ones of said successive ones of said two-axis rotating reference frame representation.

12. The apparatus of claim 11 further comprising a first-in-first-out buffer in communication with said processor for storing said successive ones of said two-axis rotating reference frame representation.

13. The apparatus of claim 11 wherein said processor is operably configured to separately sum a component of a two-axis rotating reference frame representation associated with time t, with a component of a two-axis rotating reference frame representation associated with time t-Δ

₁, to produce a first suppressed harmonic representation of said component of said two-axis rotating reference frame representation.

14. The apparatus of claim 13 wherein t-Δ

₁ represents a time Δ

₁ sample periods before time t.

15. The apparatus of claim 14 wherein Δ

₁ represents ¼

of a period of a fundamental frequency of said electrical entity.

16. The apparatus of claim 13 further comprising a fundamental frequency signal generator in communication with said processor and operably configured to determine a fundamental frequency of said electrical entity and wherein said processor is operably configured to set Δ

₁ in response to said fundamental frequency.

17. The apparatus of claim 13 wherein said processor is operably configured to cancel contributions of harmonics included in said first suppressed harmonic representation to produce a second suppressed harmonic representation.

18. The apparatus of claim 18 wherein said processor is operably configured to store successive ones of said first suppressed harmonic representation and sum particular ones of said successive ones of said first suppressed harmonic representation.

19. The apparatus of claim 18 further comprising a first-in-first-out buffer for storing said first suppressed harmonic representation.

20. The apparatus of claim 19 wherein said processor is operably configured to separately sum a component of a first suppressed harmonic representation associated with time t, with a component of a first suppressed harmonic representation associated with time t-Δ

₂ to produce said second suppressed harmonic representation.

21. The apparatus of claim 20 wherein t-Δ

₂ represents a time Δ

₂ sample periods before time t.

22. The apparatus of claim 21 wherein Δ

₂ represents 1/24 of a period of a fundamental frequency of said electrical entity.

23. The apparatus of claim 20 further comprising a fundamental frequency signal generator in communication with said processor and operably configured to determine a fundamental frequency of said electrical entity and wherein said processor is operably configured to set Δ

₂ in response to said fundamental frequency.

24. A method of producing a first phasor representation of an electrical entity at a geographical location in a multiple phase AC electric power system, the method comprising:

receiving a synchronization signal from a remote source;

producing a sampling time signal in response to said synchronization signal and a local reference time signal;

producing samples representing an amount of said entity in respective ones of said phases in said AC power system in response to said sampling time signal and said electrical entity in respective ones of said phases in said AC power system;

performing a transformation on said samples to produce a two-axis rotating reference frame representation of said electrical entity in a two-axis rotating reference frame;

for each sample, producing a representation of a sampling time associated with said sample; and

wherein said two-axis rotating reference frame representation and said representation of said sampling time comprise said first phasor representation.

25. The method of claim 24 wherein receiving said synchronization signal comprises receiving a synchronization signal that is also received by at least one other apparatus operable to produce a second phasor representation of an electrical entity at a different geographical location in said multiple phase AC electric power system.

26. The method of claim 24 wherein receiving said synchronization signal comprises receiving a wirelessly transmitted synchronization signal.

27. The method of claim 26 wherein receiving said wirelessly transmitted synchronization signal comprises receiving a global positioning signal system (GPS) signal from a GPS system.

28. The method of claim 24 wherein producing said sampling time signal comprises determining a difference in counts between a counter incremented by the local reference time signal and a counter associated with said synchronization signal in response to receipt of said synchronization signal.

29. The method of claim 28 wherein producing said sampling time signal comprises adding to a count value produced by said counter incremented by said local reference time signal a fraction of said difference in counts to produce a sample count value and causing a sample of said entity to be produced when said sample count value satisfies a criterion.

30. The method of claim 24 wherein performing a transformation comprises performing a Blondel-Park Transformation on said sampled signals.

31. The method of claim 30 wherein performing a Blondel-Park transformation comprises setting transformation coefficients of said Blondel-Park Transformation in response to said sampling time signal and a frequency value representing a rotation frequency of said two-axis rotating reference frame.

32. The method of claim 24 wherein said two-axis rotating reference frame representation comprises a direct axis component and a quadratic axis component.

33. The method of claim 24 wherein said two-axis rotating reference frame representation comprises a modulus component and an angle component.

34. The method of claim 24 further comprising canceling contributions of harmonics included in said two-axis rotating reference frame representation.

35. The method of claim 34 wherein canceling contributions of harmonics comprises storing successive ones of said two-axis rotating reference frame representation and summing particular ones of said successive ones of said two-axis rotating reference frame representation.

36. The method of claim 35 wherein storing said successive ones of said two-axis rotating reference frame representation comprises storing said two-axis rotating reference frame representations in a first-in-first-out buffer.

37. The method of claim 35 wherein summing particular ones of said successive ones of said two-axis rotating reference frame representation comprises separately summing a component of a two-axis rotating reference frame representation associated with time t, with a component of a two-axis rotating reference frame representation associated with time t-Δ

₁, to produce a first suppressed harmonic representation of said component of said two-axis rotating reference frame representation.

38. The method of claim 37 wherein t-Δ

₁ represents a time Δ

₁ sample periods before time t.

39. The method of claim 37 wherein Δ

₁ represents ¼

of a cycle of a fundamental frequency of said electrical entity.

40. The method of claim 37 further comprising determining a fundamental frequency of said electrical entity and setting Δ

₁ in response to said fundamental frequency.

41. The method of claim 36 further comprising canceling contributions of harmonics included in said first suppressed harmonic representation to produce a second suppressed harmonic representation.

42. The method of claim 41 wherein canceling contributions of harmonics comprises storing successive ones of said first suppressed harmonic representation and summing particular ones of said successive ones of said first suppressed harmonic representation.

43. The method of claim 42 wherein storing successive ones of said first suppressed harmonic representation comprises storing said first suppressed harmonic representation in a first-in-first-out buffer.

44. The method of claim 43 wherein summing particular ones of said successive ones of said first suppressed harmonic representation comprises separately summing a component of a first suppressed harmonic representation associated with time t, with a component of a first suppressed harmonic representation associated with time t-Δ

₂ to produce said second suppressed harmonic representation of said two-axis rotating reference frame representation.

45. The method of claim 44 wherein t-Δ

₂ represents a time Δ

₂ sample periods before time t.

46. The method of claim 45 wherein Δ

₂ represents 1/24 of a period of a fundamental frequency of said electrical entity.

47. The method of claim 44 further comprising determining a fundamental frequency of said electrical entity and setting Δ

₂ in response to said fundamental frequency.

48. An apparatus for producing a first phasor representation of an electrical entity at a geographical location in a multiple phase AC electric power system, the apparatus comprising:

means for receiving a synchronization signal from a remote source;

means for producing a sampling time signal in response to said synchronization signal and a local reference time signal;

means for producing samples representing an amount of said entity in respective ones of said phases in said AC power system in response to said sampling time signal and said electrical entity in respective ones of said phases in said AC power system;

means for performing a transformation on said samples to produce a two-axis rotating reference frame representation of said electrical entity in a two-axis rotating reference frame;

means for producing a representation of a sampling time associated with respective said samples;

wherein said two-axis rotating reference frame representation and said representation of said sampling time comprise said first phasor representation.

49. The apparatus of claim 48 wherein receiving said synchronization signal comprises receiving a synchronization signal that is also received by at least one other apparatus operable to produce a second phasor representation of an electrical entity at a different geographical location in said multiple phase AC electric power system.

50. The apparatus of claim 48 wherein said means for receiving said synchronization signal comprises means for receiving a wirelessly transmitted synchronization signal.

51. The apparatus of claim 50 wherein said means for receiving said wirelessly transmitted synchronization signal comprises means for receiving a Global Positioning System (GPS) signal from a GPS system.

52. The apparatus of claim 48 wherein said means for producing said sampling time signal comprises:

a) a counter incremented by a local clock signal;

b) means for determining a difference in counts between said counter incremented by said local reference time signal and a counter associated with said synchronization signal, in response to receipt of said synchronization signal.

53. The apparatus of claim 52 wherein said means for producing said sampling time signal comprises means for adding to a count value produced by said counter incremented by said local reference time signal a fraction of said difference in counts to produce a sample count value and for causing a sample of said entity to be produced when said sample count value satisfies a criterion.

54. The apparatus of claim 48 wherein said means for performing a transformation comprises means for performing a Blondel-Park Transformation on said sampled signals.

55. The apparatus of claim 54 wherein said means for performing a Blondel-Park transformation comprises means for setting transformation coefficients of said Blondel-Park Transformation in response to said sampling time signal and a frequency value representing a rotation frequency of said two-axis rotating reference frame.

56. The apparatus of claim 48 wherein said two-axis rotating reference frame representation comprises a direct axis component and a quadratic axis component.

57. The apparatus of claim 48 wherein said two-axis rotating reference frame representation comprises a modulus component and an angle component.

58. The apparatus of claim 48 further comprising means for canceling contributions of harmonics included in said two-axis rotating reference frame representation.

59. The apparatus of claim 58 wherein said means for canceling contributions of harmonics comprises means for storing successive ones of said two-axis rotating reference frame representation and means for summing particular ones of said successive ones of said two-axis rotating reference frame representation.

60. The apparatus of claim 59 wherein said means for storing said successive ones of said two-axis rotating reference frame representation comprises a first-in-first out buffer for storing said two-axis rotating reference frame representations.

61. The apparatus of claim 59 wherein said means for summing particular ones of said successive ones of said two-axis rotating reference frame representation comprises means for separately summing a component of a two-axis rotating reference frame representation associated with time t, with a corresponding component of a two-axis rotating reference frame representation associated with time t-Δ

₁, to produce a first suppressed harmonic representation of said component of said two-axis rotating reference frame representation.

62. The apparatus of claim 61 wherein t-Δ

₁ represents a time Δ

₁ sample periods before time t.

63. The apparatus of claim 61 wherein Δ

₁ represents ¼

of a period of a fundamental frequency of said electrical entity.

64. The apparatus of claim 61 further comprising means for determining a fundamental frequency of said electrical entity and setting Δ

₁ in response to said fundamental frequency.

65. The apparatus of claim 59 further comprising means for canceling contributions of harmonics included in said first suppressed harmonic representation.

66. The apparatus of claim 65 wherein said means for canceling contributions of harmonics comprises means for storing successive ones of said first suppressed harmonic representation and means for summing particular ones of said successive ones of said first suppressed harmonic representation.

67. The apparatus of claim 66 wherein said means for storing successive ones of said first suppressed harmonic representation comprises a first-in-first-out buffer for storing said first suppressed harmonic representation.

68. The apparatus of claim 67 wherein said means for summing particular ones of said successive ones of said first suppressed harmonic representation comprises means for separately summing a component of a first suppressed harmonic representation associated with time t, with a component of a first suppressed harmonic representation associated with time t-Δ

₂ to produce a second suppressed harmonic representation of said two-axis rotating reference frame representation.

69. The apparatus of claim 68 wherein t-Δ

₂ represents a time Δ

₂ sample periods before time t.

70. The apparatus of claim 68 wherein Δ

₂ represents 1/24 of a period of a fundamental frequency of said electrical entity.

71. The apparatus of claim 68 further comprising means for determining a fundamental frequency of said electrical entity and setting Δ

₂ in response to said fundamental frequency.

72. A method of canceling contributions of harmonics included in a succession of two-axis rotating reference frame representations of an electrical entity in a multiple phase AC electric power system, the method comprising:

associating successive ones of said two-axis rotating reference frame representations with respective times t; and

separately summing components of a two-axis rotating reference frame representation associated with time t, with corresponding components of a two-axis rotating reference frame representation associated with time t-Δ

₁, to produce a first suppressed harmonic representation of said two-axis rotating reference frame representations.

73. The method of claim 72 wherein associating comprises storing successive ones of said two-axis rotating reference frame representations in a first-in-first-out buffer.

74. The method of claim 73 wherein t-Δ

₁ represents a time Δ

₁ sample periods before time t.

75. The method of claim 73 wherein Δ

₁ represents ¼

of a cycle of a fundamental frequency of said electrical entity.

76. The method of claim 73 further comprising determining a fundamental frequency of said electrical entity and setting Δ

₁ in response to said fundamental frequency.

77. The method of claim 72 further comprising canceling contributions of harmonics included in said first suppressed harmonic representation.

78. The method of claim 77 wherein canceling contributions of harmonics comprises storing successive ones of said first suppressed harmonic representation and summing particular ones of said successive ones of said first suppressed harmonic representation.

79. The method of claim 78 wherein storing said successive ones of said first suppressed harmonic representation comprises storing said first suppressed harmonic representation in a first-in-first-out buffer.

80. The method of claim 79 wherein summing particular ones of said successive ones of said first suppressed harmonic representation comprises separately summing a component of a first suppressed harmonic representation associated with time t, with a component of a first suppressed harmonic representation associated with time t-Δ

₂ to produce a second suppressed harmonic representation of said component of said first suppressed harmonic representation.

81. The method of claim 80 wherein t-Δ

₂ represents a time Δ

₂ sample periods before time t.

82. The method of claim 81 wherein Δ

₂ represents 1/24 of a period of a fundamental frequency of said electrical entity.

83. The method of claim 80 further comprising determining a fundamental frequency of said electrical entity and setting Δ

₂ in response to said fundamental frequency.