Regulation of Contribution of Secondary Energy Sources to Power Grid

• US 20110221276A1
• Filed: 03/11/2010
• Published: 09/15/2011
• Est. Priority Date: 03/11/2010
• Status: Active Grant

• Current Assignee: Fluence Energy LLC (AES Corporation)
• Original Assignee: AES Corporation
• Inventors: Shelton, J. Christopher, Meersman, Steven, Geinzer, Jay
• Granted Patent: US 8,914,158 B2
• Time in Patent Office: Days
• US Class Current: 307/66
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02J 7/35 with light sensitive cells

Abstract

An energy storage medium is combined with a secondary energy source that supplies power to an electricity distribution grid. The charge and discharge behavior of the energy storage medium is controlled so that rapid increases in the output of a secondary source of energy are absorbed by the storage system, whereas rapid decreases in the output of the secondary source are compensated by discharging stored energy onto the grid. The combined contributions of the secondary source and the energy storage system ensures a rate of change that does not exceed a defined level. Maximum and minimum output power levels for the secondary source can be established to define a normal operating range. The charging or discharging of the energy storage system is also performed when the secondary output power level exceeds or falls below the limits of the defined range.

Claims

1. A method of regulating the output power of a source of electricity that is supplied to an electricity distribution grid, comprising:

determining whether (a) the output power of the electricity source is outside a predetermined range, and (b) the rate of change of the output power exceeds a predefined maximum value;

if either or both of conditions (a) and (b) is determined to be met, regulating the output power supplied to the grid by transferring energy between an energy storage medium and the electricity grid.

2. The method of claim 1, wherein said predetermined range is defined by a lower limit value, and wherein, if the output power of the electricity source is less than said lower limit value, energy is transferred from the energy storage medium to the electricity grid.

3. The method of claim 2, further including the step of constraining the amount of energy transferred from the energy storage medium to the electricity grid in accordance with the predefined maximum value for the rate of change.

4. The method of claim 3, wherein the amount of energy transferred from the energy storage medium to the electricity grid is further constrained in accordance with the lesser of the state of charge of the energy storage medium and the maximum power rating of the energy storage medium.

5. The method of claim 2, wherein said predetermined range is further defined by an upper limit value, and wherein, if the output power of the electricity source is greater than said upper limit value, energy is transferred from the electricity grid to the energy storage medium.

6. The method of claim 5, further including the step of constraining the amount of energy transferred to the energy storage medium from the electricity grid in accordance with the predefined maximum value for the rate of change.

7. The method of claim 6, wherein the amount of energy transferred to the energy storage medium from the electricity grid is further constrained in accordance with the lesser of the unused capacity of the energy storage medium and the maximum power rating of the energy storage medium.

8. The method of claim 1, wherein the predetermined range is a function of a temporal factor.

9. The method of claim 1, wherein the predetermined range is a function of a geographic parameter that influences the output of the electricity source.

10. The method of claim 1, wherein the predetermined range is a function of the state of charge of the energy storage medium.

11. The method of claim 1 wherein the predetermined maximum rate of change is a function of a temporal factor.

12. The method of claim 1, wherein the predetermined maximum rate of change is a function of a geographic parameter that influences the output of the electricity source.

13. The method of claim 1, wherein the predetermined maximum rate of change is a function of the output of the electricity source.

14. The method of claim 1, wherein the predetermined maximum rate of change is a function of the state of charge of the energy storage medium.

15. The method of claim 1 wherein, if neither of conditions (a) or (b) is determined to be met, performing the following additional steps:

determining whether a state of charge (SoC) of the energy storage medium is within predetermined thresholds; and

transferring energy between the energy storage device and the electricity grid to bring the SoC within said predetermined limits when the SoC of the energy storage device is outside said predetermined thresholds.

16. The method of claim 15, wherein the step of transferring energy between the energy storage device and the electricity grid to bring the SOC within said predetermined thresholds comprises:

defining an upper value and a lower value for transferring energy between the energy storage medium and the electricity grid, each of which is based upon a most recent amount of electricity being supplied to the electricity grid and the maximum value for the rate of change;

determining whether the output power of the electricity source is greater than the upper value, and if so transferring energy from the electricity grid to the energy storage medium, and

if the output power of the electricity source is not greater than the upper value, determining whether the output power of the electricity source is less than the lower value, and if so transferring energy to the electricity grid from the energy storage medium.

17. The method of claim 16, further including the step of constraining the amount of energy transferred from the energy storage medium to the electricity grid in accordance with the lesser of the state of charge of the energy storage medium and the maximum power rating of the energy storage medium.

18. The method of claim 16, further including the step of constraining the amount of energy transferred to the energy storage medium from the electricity grid in accordance with the lesser of the unused capacity of the energy storage medium and the maximum power rating of the energy storage medium.

19. The method of claim 15, wherein the predetermined thresholds are a function of a temporal factor.

20. A system for regulating the output power of a source of electricity that is supplied to an electricity distribution grid, comprising:

at least one energy storage medium;

a converter system that, in response to a command to add energy to or absorb energy from the grid, selectively couples said storage medium to the grid to transfer energy between the energy storage medium and the grid; and

a power regulating system that determines whether (a) the output power of the electricity source is outside a predetermined range, and (b) the rate of change of the output power exceeds a predefined maximum value, and controls said converter system to transfer energy between the energy storage device and the electricity grid when either or both of conditions (a) and (b) is determined to be met.

21. The system of claim 20, wherein said power regulating system further includes a frequency regulating system that determines whether the operating frequency of the electricity grid is within a predetermined range of a nominal operating frequency, and controls said converter system to transfer energy between the energy storage device and the electricity grid to bring the operating frequency within said range.

22. The system of claim 21, wherein the transfer of energy is a function of the operating frequency of the electricity grid.