Island grid power supply apparatus and methods using energy storage for transient stabilization

• US 9,312,699 B2
• Filed: 05/02/2013
• Issued: 04/12/2016
• Est. Priority Date: 10/11/2012
• Status: Active Grant

• Current Assignee: FlexGen Power Systems Inc.
• Original Assignee: FlexGen Power Systems Inc.
• Inventors: Taimela, Pasi, Olivo, Tony, Johnson, Robert William Jr., Moorehead, Doug
• Primary Examiner(s): Fureman, Jared
• Assistant Examiner(s): Pham, Duc M
• Application Number:
  US13/875,603
• Publication Number:
  US 20140103727A1
• Time in Patent Office: 1,076 Days
• Field of Search: 307/76
• US Class Current: 1/1
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2310/10 The network having a local or delimited stationary reach
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/241 The oscillation concerning frequency
• CPC Class Codes: H02J 3/28 Arrangements for balancing of the load in a network by storage of energy
• CPC Class Codes: H02J 3/30 using dynamo-electric machines coupled to flywheels
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 7/44 by static converters

Abstract

A system includes at least one generator coupled to an island grid, at least one energy storage unit and at least one converter coupled to the at least one energy storage unit and configured to be coupled to the island grid. The system further includes a control circuit configured to cause the at least one converter to transfer power between the at least one energy storage unit and the grid responsive to a change in a load on the island grid to maintain operation of the at least one generator at a predetermined operating point. The at least one generator may include a control system configured to match generator output to the load and the control circuit may be configured to maintain the control system of the at least one generator within a predetermined dynamic response capability limit responsive to the change in the load.

Claims

1. An island grid power supply system comprising:

at least one energy storage unit;

at least one converter coupled to the at least one energy storage unit and configured to be coupled to an island grid; and

a control circuit configured to detect a frequency variation of the island grid and to responsively cause the at least one converter to transfer power between the at least one energy storage unit and the island grid, wherein the control circuit comprises a frequency control loop configured to reduce a frequency error of the island grid and a power control loop configured to reduce a power transfer between the energy storage unit and the island grid and wherein the control circuit is configured to control a power transfer from the energy storage unit to the island grid based on a combination of outputs of the frequency control loop and the power control loop.

2. The system of claim 1, wherein the control circuit is configured to cause a power transfer between the energy storage unit and the island grid to compensate for a load response delay of at least one generator coupled to the island grid.

3. The system of claim 2, wherein the control circuit is configured to reduce a power transfer from the energy storage unit to the island grid responsive to the at least one generator delivering increased power to the grid.

4. The system of claim 1, wherein the at least one energy storage unit comprises a first energy storage unit and a second energy storage unit and wherein the control circuit is configured to selectively transfer power between the first and second energy storage units and the island grid under respective first and second load conditions.

5. The system of claim 4, wherein the first energy storage unit has a greater demand capability than the second energy storage unit and wherein the second energy storage unit has a greater energy storage capacity than the first energy storage unit.

6. The system of claim 4, wherein the at least one converter comprises first and second converters configured to couple respective ones of the first and second energy storage units to the island grid.

7. A system comprising:

an island grid;

at least one engine/generator set coupled to the island grid; and

a transient frequency stabilization system comprising at least one energy storage unit and configured to detect a frequency deviation of the island grid and to responsively perform a momentary transfer of energy between the at least one energy storage unit and the island grid, wherein the transient frequency stabilization system comprises;

at least one converter coupled to the at least one energy storage unit and configured to be coupled to the island grid; and

a control circuit configured to detect a frequency variation of the island grid and to responsively cause the at least one converter to transfer power between the at least one energy storage unit and the island grid, wherein the control circuit comprises a frequency control loop configured to reduce a frequency error of the island grid and a power control loop configured to reduce a power transfer between the energy storage unit and the island grid and wherein the control circuit is configured to control a power transfer from the energy storage unit to the island grid based on a combination of outputs of the frequency control loop and the power control loop.

8. The system of claim 7, wherein the control circuit is configured to cause a power transfer between the energy storage unit and the island grid to compensate for a load response delay of at least one generator coupled to the island grid.

9. The system of claim 7, wherein the at least one energy storage unit comprises a first energy storage unit and a second energy storage unit and wherein the control circuit is configured to selectively transfer power between the first and second energy storage units and the island grid under respective first and second load conditions.

10. The system of claim 7, wherein the at least one engine/generator set comprises at least two engine/generator sets coupled to the grid and wherein the system further comprises a system controller configured to control the at least two engine/generator sets responsive to an availability of the transient frequency stabilization system.

11. The system of claim 7, wherein the transient frequency stabilization system is configured to support an island grid load in response to a failure of a first engine/generator set until a second engine/engine generator set assumes the island grid load.

12. The system of claim 7, wherein the at least one generator comprises a variable speed generator.

13. A system comprising:

at least one generator coupled to an island grid;

at least one energy storage unit;

at least one converter coupled to the at least one energy storage unit and configured to be coupled to the island grid; and

a control circuit configured to cause the at least one converter to transfer power between the at least one energy storage unit and the grid responsive to a change in a load on the island grid to maintain operation of the at least one generator at a predetermined operating point, wherein the at least one generator comprises a control system configured to match generator output to the load and wherein the control circuit is configured to maintain the control system of the at least one generator within a predetermined dynamic response capability limit responsive to the change in the load.

14. The system of claim 13, wherein the at least one energy storage unit comprises at least one ultracapacitor.

15. The system of claim 13, wherein the at least one generator comprises a natural gas engine and/or a diesel engine.