Method and apparatus for providing power to a utility network

• US 6,600,973 B1
• Filed: 11/24/1999
• Issued: 07/29/2003
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• Current Assignee: American Superconductor Corporation
• Original Assignee: American Superconductor Corporation
• Inventors: Folts, Douglas C., Hubert, Thomas Gregory
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): RODRIGUEZ, PAUL L
• Application Number:
  US09/449,375
• Time in Patent Office: 1,343 Days
• Field of Search: 700/286, 700/292, 700/293, 700/294, 700/295, 700/297, 700/298, 323/207, 323/205, 324/512, 702/58, 702/59, 702/60, 702/64, 702/65, 307/24, 307/26, 307/31, 307/23, 307/64, 307/66, 307/75, 307/87, 307/103, 361/18, 361/115
• US Class Current: 700/297
• CPC Class Codes: H02J 15/00 Systems for storing electric energy mechanical systems therefor F01-F04; in chemical form H01M
• CPC Class Codes: H02J 3/185 wherein such reactive element is purely inductive, e.g. superconductive magnetic energy storage systems [SMES]
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]

Abstract

Power is provided from an energy storage device to a utility network based on a detected condition, such as a fault, in the network. Specifically, it is determined whether a fault on the utility network is a near fault or a far fault relative to the energy storage device. Whether a fault is classified as “near” or “far” is determined based on a voltage drop in the utility network. Power is then supplied to the utility network based on whether the fault is a near fault or a far fault.

Claims

1. A method of providing power from an energy storage device to a utility network, comprising:

determining whether a fault on the utility network comprises a high voltage drop fault or a low voltage drop fault, the high voltage drop fault causing a greater voltage drop on the utility network than the low voltage drop fault; and

supplying power to the utility network based on whether the fault is a high voltage drop fault or a low voltage drop fault, wherein reactive power only is supplied initially in the case of a high voltage drop fault.

2. The method of claim 1, wherein supplying comprises supplying both real and reactive power to the utility network if the fault is a low voltage drop fault.

3. The method of claim 1, further comprising:

supplying real power to the utility network after a high voltage drop fault has been at least partially cleared;

wherein only reactive power is supplied to the utility network before the high voltage drop fault is at least partially cleared.

4. The method of claim 1, wherein determining whether the fault comprises a high voltage drop fault or a low voltage drop fault comprises detecting a voltage drop on the utility network.

5. The method of claim 4, wherein:

if the voltage drop is below a predetermined level, the fault is classified as a high voltage drop fault; and

if the voltage drop is not below a predetermined level, the fault is classified as a low voltage drop fault.

6. The method of claim 5, wherein:

if the voltage drop is between a first percentage and a second percentage of a nominal voltage of the utility network, the fault is classified as a low voltage drop fault; and

if the voltage drop is below the first percentage of the nominal voltage of the utility network, the fault is classified as a high voltage drop fault;

wherein the second percentage is higher than the first percentage.

7. The method of claim 1, wherein the energy storage device comprises a current-mode energy storage device.

8. The method of claim 7, wherein the current-mode energy storage device comprises a superconducting magnet.

9. An apparatus for providing power from an energy storage device to a utility network, comprising:

an inverter which supplies power to the utility network; and

a controller which (i) determines whether a fault on the utility network comprises a high voltage drop fault or a low voltage drop fault, the high voltage drop fault causing a greater voltage drop on the utility network than the low voltage drop fault, and (ii) controls the inverter to supply power to the utility network based on whether the fault is a high voltage drop fault or a low voltage drop fault, the controller controlling the inverter to initially supply reactive power only in the case of a high voltage drop fault.

10. The apparatus of claim 9, wherein the controller controls the inverter to supply both real and reactive power to the utility network if the fault is a low voltage drop fault.

11. The apparatus of claim 9, wherein the controller controls the inverter to (i) supply real power to the utility network when a high voltage drop fault is at least partially cleared, and (ii) supply only reactive power to the utility network before the high voltage drop fault is at least partially cleared.

12. The apparatus of claim 9, wherein the controller determines whether the fault comprises a high voltage drop fault or a low voltage drop fault based on a detected voltage drop in the utility network.

13. The apparatus of claim 12, wherein:

if the voltage drop is below a predetermined level, the controller determines that the fault is a high voltage drop fault; and

if the voltage drop is not below a predetermined level, the controller determines that the fault is a low voltage drop fault.

14. The apparatus of claim 13, wherein:

if the voltage drop is between a first percentage and a second percentage of a nominal voltage of the utility network, the controller determines that the fault is a low voltage drop fault; and

if the voltage drop is below the first percentage of the nominal voltage of the utility network, the controller determines that the fault is a high voltage drop fault;

wherein the second percentage is higher than the first percentage.

15. The apparatus of claim 9, wherein the energy storage device comprises a current-mode energy storage device.

16. The apparatus of claim 15, wherein the current-mode energy storage device comprises a superconducting magnet.

17. A computer program stored on a computer-readable medium for controlling power supplied from an energy storage device to a utility network, the computer program comprising instructions that cause a computer to:

determine whether a fault on the utility network comprises a high voltage drop fault or a low voltage drop fault, the high voltage drop fault causing a greater voltage drop on the utility network than the low voltage drop fault; and

control a supply of power to the utility network based on whether the fault is a high voltage drop fault or a low voltage drop fault, wherein reactive power only is supplied initially in the case of a high voltage drop fault.

18. The computer program of claim 17, wherein controlling comprises causing both real and reactive power to be supplied to the utility network if the fault is a low voltage drop fault.

19. The computer program of claim 17, wherein controlling comprises:

causing real power to be supplied to the utility network when the high voltage drop fault is at least partially cleared; and

causing only reactive power to be supplied to the utility network before the high voltage drop fault is at least partially cleared.

20. The computer program of claim 17, wherein determining whether the fault comprises a high voltage drop fault or a low voltage drop fault is based on a detected voltage drop on the utility network.

21. The computer program of claim 20, wherein:

if the voltage drop is below a predetermined level, the fault is classified as a high voltage drop fault; and

if the voltage drop is not below a predetermined level, the fault is classified as a low voltage drop fault.

22. The computer program of claim 21, wherein:

if the voltage drop is between a first percentage and a second percentage of a nominal voltage of the utility network, the fault is classified as a low voltage drop fault; and

if the voltage drop is below the first percentage of the nominal voltage of the utility network, the fault is classified as a high voltage drop fault;

wherein the second percentage is higher than the first percentage.

23. The computer program of claim 17, wherein the energy storage device comprises a current-mode energy storage device.

24. The computer program of claim 23, wherein the current-mode energy storage device comprises a superconducting magnet.

25. A method of providing power from an energy storage device to a utility network, comprising:

determining a voltage on the utility network; and

supplying power to the utility network based on the voltage;

wherein (i) if the voltage is between a first percentage and a second percentage of a nominal voltage of the utility network, real and reactive power are supplied to the utility network, and (ii) if the voltage is below the first percentage of the nominal voltage of the utility network, reactive power only is supplied to the utility network, the second percentage being higher than the first percentage.