Method and apparatus for controlling power drawn from an energy converter

• US 20070040540A1
• Filed: 08/14/2006
• Published: 02/22/2007
• Est. Priority Date: 09/29/2003
• Status: Active Grant

• Current Assignee: Xantrex Technology Incorporated (Mission Critical Electronics LLC)
• Original Assignee: Xantrex Technology Incorporated (Mission Critical Electronics LLC)
• Inventors: Cutler, Henry
• Granted Patent: US 7,432,691 B2
• Time in Patent Office: Days
• US Class Current: 323/283
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources maximum power point systems in particular G05F1/67
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Methods, apparatus, media and signals for controlling power drawn from an energy converter to supply a load, where the energy converter is operable to convert energy from a physical source into electrical energy. Power drawn from the energy converter is changed when a supply voltage of the energy converter meets a criterion. The criterion and the change in the amount of power drawn from the energy converter are dependent upon a present amount of power supplied to the load. The methods, apparatus, media and signals described herein may provide improvements to DC to AC maximum power point tracking in an energy conversion system such as a photovoltaic power generation system.

Claims

1. A method of controlling power drawn from an energy converter to supply a load, where the energy converter is operable to convert energy from a physical source into electrical energy, the method comprising changing the amount of power drawn from the energy converter when a supply voltage of the energy converter meets a criterion, said criterion and a change in the amount of power drawn from the energy converter being dependent upon a present amount of power supplied to the load.

2. The method of claim 1 further comprising measuring said supply voltage.

3. The method of claim 1 wherein changing said power drawn from the energy converter comprises decreasing said power drawn from the energy converter by an amount corresponding to a change in said power supplied to the load in a time interval.

4. The method of claim 1 wherein changing said power drawn from the energy converter comprises increasing said power drawn from the energy converter by an amount associated with a range of power supplied to the load.

5. The method of claim 1 further comprising deeming said supply voltage satisfies said criterion when said supply voltage is within a first range of voltages relative to a reference voltage.

6. The method of claim 5 wherein said reference voltage corresponds to a maximum power point of the energy conversion device.

7. The method of claim 5 wherein said first range includes voltages greater than said reference voltage.

8. The method of claim 5 wherein said first range includes voltages less than said reference voltage.

9. The method of claim 5 wherein said first range includes voltages less than said reference voltage and voltages greater than said reference voltage.

10. The method of claim 5 wherein said first range excludes a range of voltages within a limit of said reference voltage.

11. The method of claim 5 wherein said first range is dependent upon a trend in measured values of said supply voltage.

12. The method of claim 11 wherein said first range is dependent upon a change in said supply voltage occurring after an increase in said power drawn from the energy converter.

13. The method of claim 12 wherein said first range is bounded between minimum and maximum limits.

14. The method of claim 1 further comprising performing said method periodically.

15. The method of claim 14 further comprising defining a period for performing said method periodically.

16. The method of claim 15 wherein defining said period comprises defining said period as a function of said power supplied to the load.

17. The method of claim 16 further comprising increasing said period when said power supplied to the load is relatively low and decreasing said period when said power supplied to the load is relatively high.

18. The method of claim 5 further comprising adjusting said reference voltage periodically.

19. The method of claim 5 further comprising increasing said reference voltage when the change in the amount of power drawn from the energy converter results in a change in said supply voltage within a second range.

20. The method of claim 19 wherein said second range is dependent upon the present amount of power being supplied to the load.

21. The method of claim 20 wherein said second range is relatively small when the present amount of power supplied to the load is relatively large and wherein said second range is relatively large when the present amount of power supplied to the load is relatively small.

22. The method of claim 19 wherein an amount by which said reference voltage is decreased is dependent upon the present amount of power supplied to the load.

23. The method of claim 22 wherein the amount by which said reference voltage is decreased is relatively large when the present amount of power supplied to the load is relatively low and wherein the amount by which said reference voltage is decreased is relatively low when the present amount of power supplied to the load is relatively high.