Methods and systems for intentionally isolating distributed power generation sources

• US 7,834,479 B2
• Filed: 03/01/2006
• Issued: 11/16/2010
• Est. Priority Date: 03/01/2005
• Status: Active Grant

• Current Assignee: Beacon Power (RGA Labs, Inc.)
• Original Assignee: Beacon Power Corporation (RGA Labs, Inc.)
• Inventors: Rojas, Hernan Alex, Lazarewicz, Matthew L., Capp, F. William
• Primary Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US11/817,580
• Publication Number:
  US 20080278000A1
• Time in Patent Office: 1,721 Days
• Field of Search: 307/21, 700/286, 363/74
• US Class Current: 307/21
• CPC Class Codes: H02J 3/04 for connecting networks of the same frequency but supplied from different sources
• 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

Abstract

A method and system for operating a mini-grid including one or more power generation sources and one or more loads independently from a utility grid is provided, where the mini-grid is disconnected from the utility grid in response to a power disruption over the utility grid. A universal interconnect device forms a connection between the mini-grid and the utility grid. In the disconnected state, the mini-grid operates independently from the utility grid, such that the power generation sources of the mini-grid supply the loads. Frequency and voltage regulation are provided by the universal interconnect device through a monitoring function performed by a controller in conjunction with at least an energy storage device, which can absorb or generate power as needed.

Claims

1. A method for operating a mini-grid including one or more power generation sources and one or more loads connected to a bus, comprising the steps of:

monitoring a condition of a utility grid;

disconnecting the mini-grid from the utility grid to operate the mini-grid independently in response to a power disruption over the utility grid;

monitoring at least one of a frequency and a voltage of power on the bus; and

providing an interconnect device connected to the bus, the interconnect device including at least one of;

an energy storage device for absorbing or releasing real power to control the frequency of the power on the bus, and a power quality compensator for absorbing or releasing reactive power to control the voltage of the power on the bus.

2. The method of claim 1, and further including the step of connecting the mini-grid to the utility grid upon receiving a signal from the utility grid.

3. The method of claim 1, and further including the step of connecting the mini-grid to the utility grid upon sensing a normal operating state of the utility grid.

4. The method of claim 1, wherein the step of monitoring the condition of the utility grid includes receiving a signal from the utility grid.

5. The method of claim 1, wherein the step of monitoring the condition of the utility grid includes sensing an operating state of the utility grid.

6. The method of claim 1, wherein after the disconnecting step, the mini-grid is operated independently of the utility grid.

7. The method of claim 6, wherein during independent operation of the mini-grid, at least one DG source is operated to supply power to at least one load connected to the mini-grid.

8. The method of claim 1, wherein the energy storage device includes at least one flywheel energy storage system.

9. The method of claim 1, wherein the interconnect device includes at least the energy storage device, the power quality compensator, and a communication/control module for monitoring at least one of the frequency and the voltage of the bus.

10. A method for operating a mini-grid independently of a utility grid, comprising the steps of:

providing the mini-grid including one or more power generation sources and one or more loads connected to a bus;

monitoring at least one of a frequency and a voltage of power on the bus; and

providing an interconnect device connected to the bus, the interconnect device including at least one of;

an energy storage device for absorbing or releasing real power to control the frequency of the power on the bus, and a power quality compensator for absorbing or releasing reactive power to control the voltage of the power on the bus.

11. The method of claim 10, wherein the step of operating the interconnect device is carried out by adding or removing one of the power generation sources.

12. The method of claim 10, wherein the interconnect device is operated by adding or removing one of the loads.

13. A system for operating a mini-grid including one or more power generation sources and one or more loads connected to a bus, comprising:

a switch for connecting the mini-grid to a utility grid; and

a universal interconnect device provided between the switch and the bus, the universal interconnect device configured to monitor a condition of the utility grid and disconnect the mini-grid from the utility grid in response to a power disruption over the utility grid;

the universal interconnect device further including a controller for monitoring at least one of a frequency and a voltage of power on the bus, the controller operable to activate at least one of an energy storage device and a power quality compensator to control the frequency or voltage of the power on the bus.

14. The system of claim 13, wherein by disconnecting the mini-grid from the utility grid, the utility grid operates independently from the utility grid.

15. The system of claim 14, wherein during independent operation of the mini-grid, at least one DG source is operated to supply power to at least one load connected to the mini-grid.

16. The system of claim 14, wherein the controller activates the energy storage device to generate or absorb real power from the bus to control the frequency.

17. The system of claim 14, wherein the controller activates the power quality compensator to generate or absorb reactive power from the bus to control the voltage.

18. The system of claim 13, wherein the energy storage device includes at least one flywheel energy storage system.

19. The system of claim 13, wherein the power quality compensator is an AC/DC inverter.

20. The system of claim 13, wherein the bus is a three-phase AC bus.

21. A universal interconnect device for forming a connection between a utility grid and a mini-grid having one or more power generation sources and one or more loads connected to a bus, comprising:

a device for connecting the universal interconnect device to the bus;

a controller configured to monitor a condition of the utility grid and disconnect the mini-grid from the utility grid in response to a power disruption over the utility grid, such that after disconnection the mini-grid operates independently from the utility grid, where the controller monitors at least one of a frequency and a voltage of power on the bus; and

an energy storage device for absorbing or releasing real power to control the frequency of the power on the bus.

22. The universal interconnect device of claim 21, and further including a power quality compensator for absorbing or releasing reactive power to control the voltage of the power on the bus.