Power factor improving arrangement

• US 5,399,955 A
• Filed: 03/28/1994
• Issued: 03/21/1995
• Est. Priority Date: 09/27/1990
• Status: Expired due to Term

• Current Assignee: Avaya Incorporated
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: McIntosh, James L., Glaser, Richard W.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): BERHANE, ADOLF D
• Application Number:
  US08/218,468
• Time in Patent Office: 358 Days
• Field of Search: 323/208, 323/209, 323/210, 323/211
• US Class Current: 323/208
• CPC Class Codes: G05F 1/70 Regulating power factor; Regulating reactive current or power
• CPC Class Codes: H02J 3/1807 using series compensators
• CPC Class Codes: Y02E 40/30 Reactive power compensation
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

An impedance compensator for adjusting the power factor of a power distribution system by directly measuring impedance at a point in the power distribution system and dynamically adjusting that impedance to be resistive yielding a power factor of one. The compensator dynamically inserts and removes both capacitance and inductance to adjust the impedance. The inductance is utilized to make coarse adjustments to the impedance, whereas the capacitance is utilized to make fine adjustments.

Claims

1. Apparatus for adjusting a power factor in a power distribution system, comprising:

means for continuously determining an impedance of said power distribution system;

means for convening said impedance of said power distribution system to a voltage representing said impedance;

means responsive to said voltage for indicating whether said impedance is capacitive, inductive, or resistive;

means for controlling an amount of capacitance in parallel with said power distribution system to adjust said impedance to be substantially resistive resulting in said power factor being substantially unity with said capacitance having a predetermined maximum and minimum values; and

means for controlling an amount of inductance in series with said power distribution system to adjust said impedance to be substantially resistive resulting in said power factor being substantially unity upon said predetermined maximum or minimum values of capacitance having been exceeded.

2. The apparatus of claim 1 wherein said capacitance controlling means continuously controls the amount of said parallel capacitance.

3. The apparatus of claim 1 wherein said inductance controlling means comprises a plurality of inductive components;

an inductance controller responsive to said capacitance being at said predetermined minimum value for inserting one of said inductive components whereby said amount of inductance inserted in series with said power distribution system is increased; and

said inductance controller further responsive to said capacitance being at said predetermined minimum value for removing one of said inductive components whereby said amount of said inductance inserted in series with said power distribution system is decreased.

4. Apparatus for adjusting a power factor in a power distribution system, comprising:

means for continuously determining an impedance of said power distribution system;

a transformer for reflecting said impedance;

an oscillator responsive to said reflected impedance for generating a frequency representing said impedance;

a frequency-to-voltage converter responsive to said frequency for generating said voltage;

means responsive to said voltage for indicating whether said impedance is capacitive, inductive, or resistive; and

means for adjusting said impedance to be substantially resistive resulting in said power factor being substantially unity.

5. The apparatus of clam 4 wherein said indicating means comprises an error amplifier responsive to said voltage for generating an error voltage such that said error voltage is substantially equal to a predetermined center voltage upon said impedance being resistive and said error voltage being shifted to a first voltage range from said predetermined center voltage upon said impedance being capacitive and said error voltage being shifted to a second voltage range from said predetermined center voltage upon said impedance being inductive.

6. The apparatus of claim 5 wherein said adjusting means comprises means for controlling the amount of capacitance contributed to said impedance by said apparatus such that said capacitance controlling means responsive to said error voltage being in said first voltage range to reduce the contributed capacitance and responsive to said error voltage being in said second voltage range to increase the contributed capacitance.

7. The apparatus of claim 6 wherein said indicating means further comprises a set amplifier responsive to said voltage being equal to or greater than a first predetermined absolute voltage value from said error voltage in said second voltage range for generating a set signal;

a reset amplifier responsive to said voltage being equal to or greater than a second predetermined absolute voltage value from said error voltage in said first voltage level for generating a reset signal;

said adjusting means further comprises an inductance controlling means to control inductance contributed by said apparatus to said impedance for increasing inductance in response to said set signal; and

said inductance controlling means further responsive to said reset signal for decreasing the amount of inductance contributed to said impedance by said apparatus.

8. The apparatus of claim 7 wherein said inductance controlling means comprises a plurality of inductive components;

an inductance controller responsive to said set signal for inserting one of said inductive components to increase the amount of inductance contributed to said impedance; and

said inductance controller further responsive to said reset signal for removing one of said inductive components to decrease the amount of inductance contributed to said impedance.

9. The apparatus of claim 8 wherein said inductance controlling means further comprises electrically actuated switches each individually connected in parallel with one of said inductive components;

said inductance controller inserts said one of said inductive components by opening the electrically actuated switch connected in parallel and removes said one of said inductive components by closing said connected electrically actuated switch; and

said electrically actuated switches are open in the absence of electricity in said power distribution system resulting in all of said inductive components being inserted upon electricity initially being applied to said power distribution system which limits the surge of electrical current with said power distribution system.

10. A method for adjusting a power factor in a power distribution system, said method comprising the steps of:

continuously determining an impedance of said power distribution system;

converting said impedance of said power distribution system to a voltage representing said impedance;

indicating in response to said voltage whether said impedance is capacitive, inductive, or resistive;

controlling an amount of capacitance in parallel with said power distribution system to adjust said impedance to be substantially resistive resulting in said power factor being substantially unity with said capacitance having a predetermined maximum and minimum values; and

controlling an amount of inductance in series with said power distribution system to adjust said impedance to be substantially resistive resulting in said power factor being substantially unity upon said predetermined maximum or minimum values of capacitance having been exceeded.

11. The method of claim 10 wherein said capacitance controlling step continuously controls the amount of said parallel capacitance.

12. The method of claim 10 wherein said inductance controlling step comprises the steps of

inserting one of a plurality of inductive components in response to said capacitance being at said predetermined minimum value whereby said amount of inductance inserted in series with said power distribution system is increased;

and

removing one of said inductive components in response to said capacitance being at said predetermined minimum value whereby said amount of said inductance inserted in series with said power distribution system is decreased.

13. A method for adjusting a power factor in a power distribution system, said method comprising the steps of:

continuously determining an impedance of said power distribution system;

reflecting said impedance with a transformer;

generating a frequency representing said impedance by an oscillator responsive to said reflected impedance;

generating said voltage by a frequency-to-voltage converter responsive to said frequency;

indicating in response to said voltage whether said impedance is capacitive, inductive, or resistive; and

adjusting said impedance to be substantially resistive resulting in said power factor being substantially unity.

14. The method of claim 13 wherein said indicating step comprises the step of generating an error voltage with an error amplifier responsive to said voltage such that said error voltage is substantially equal to a predetermined center voltage upon said impedance being resistive and said error voltage being shifted to a first voltage range from said predetermined center voltage upon said impedance being capacitive and said error voltage being shifted to a second voltage range from said predetermined center voltage upon said impedance being inductive.

15. The method of claim 14 wherein said adjusting step comprises the step of controlling the amount of capacitance contributed to said impedance by said method such that said capacitance controlling responsive to said error voltage being in said first voltage range to reduce the contributed capacitance and responsive to said error voltage being of said second voltage range to increase the contributed capacitance.

16. The method of claim 15 wherein said indicating step further comprises the steps of generating a set signal with a set amplifier responsive to said voltage being equal to or greater than a first predetermined absolute voltage value from said error voltage in said second voltage range;

generating a reset signal with a reset amplifier responsive to said voltage being equal to or greater than a second predetermined absolute voltage value from said error voltage in said first voltage level;

said adjusting step further comprises the step of controlling inductance contributed by said method to said impedance for increasing inductance in response to said set signal; and

said inductance controlling step further responsive to said reset signal for decreasing the amount of inductance contributed to said impedance by said method.

17. The method of claim 16 wherein said inductance controlling step comprises the steps of inserting one of a plurality of inductive components in response to said set signal to increase the amount of inductance contributed to said impedance;

and

removing one of said inductive components in response to said reset signal to decrease the amount of inductance contributed to said impedance.