METHOD AND APPARATUS FOR IMPROVED BURST MODE DURING POWER CONVERSION

• US 20110292701A1
• Filed: 08/09/2011
• Published: 12/01/2011
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Fornage, Martin
• Granted Patent: US 8,319,378 B2
• Time in Patent Office: Days
• US Class Current: 363/95
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: H02J 2300/26 involving maximum power point tracking control for photovoltaic sources
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 7/42 Conversion of dc power input into ac power output without possibility of reversal
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A method and apparatus for power conversion. In one embodiment, the apparatus comprises a DC-AC conversion stage; an intermediate capacitor coupled across the DC-AC conversion stage; and a burst mode controller coupled to the intermediate capacitor and the DC-AC conversion stage, wherein the burst mode controller (i) maintains a voltage of the intermediate capacitor below a preset limit during a storage period and (ii) drives the DC-AC conversion stage to convert DC input to AC output during a burst period, wherein the storage and burst periods occur during a burst mode operation.

Claims

1. An apparatus for power conversion, comprising:

a DC-AC conversion stage;

an intermediate capacitor coupled across the DC-AC conversion stage; and

a burst mode controller coupled to the intermediate capacitor and the DC-AC conversion stage, wherein the burst mode controller (i) maintains a voltage of the intermediate capacitor below a preset limit during a storage period and (ii) drives the DC-AC conversion stage to convert DC input to AC output during a burst period, wherein the storage and burst periods occur during a burst mode operation.

2. The apparatus of claim 1, wherein the DC input results from a DC input current and energy stored in the intermediate capacitor.

3. The apparatus of claim 2, further comprising a DC-DC conversion stage coupled across the intermediate capacitor, wherein the DC-DC conversion stage provides the DC input current.

4. The apparatus of claim 2, wherein the energy is stored during the storage period and the storage period is at least one AC grid voltage cycle.

5. The apparatus of claim 1, wherein the DC-AC conversion stage is disabled during the storage period.

6. The apparatus of claim 1, wherein the preset limit is 10% of an average voltage from a DC source.

7. The apparatus of claim 1, wherein the burst mode operation occurs when input power from a DC source is below a burst mode threshold.

8. The apparatus of claim 7, further comprising a maximum power point tracking (MPPT) controller for biasing the DC source proximate a maximum power point (MPP).

9. The apparatus of claim 1, wherein the AC output is synchronous with an AC grid voltage.

10. The apparatus of claim 1, wherein the storage period ends and the burst period begins based on the voltage.

11. A method for power conversion, comprising:

storing energy during a storage period, wherein a voltage of an intermediate capacitor across a DC-AC conversion stage is maintained below a preset limit during the storage period; and

driving a DC-AC conversion stage to convert DC input to AC output during a burst period, wherein the storage and burst periods occur during a burst mode operation.

12. The method of claim 11, wherein the DC input results from a DC input current and the energy stored in the intermediate capacitor.

13. The method of claim 12, wherein the DC input current is provided by a DC-DC conversion stage coupled across the intermediate capacitor.

14. The method of claim 12, wherein the storage period is at least one AC grid voltage cycle.

15. The method of claim 11, further comprising disabling the DC-AC conversion stage during the storage period.

16. The method of claim 11, wherein the preset limit is 10% of an average voltage from a DC source.

17. The method of claim 11, wherein the burst mode operation occurs when input power from a DC source is below a burst mode threshold.

18. The method of claim 17, further comprising biasing the DC source proximate a maximum power point (MPP).

19. The method of claim 11, wherein the AC output is synchronous with an AC grid voltage.

20. The method of claim 11, wherein the storage period ends and the burst period begins based on the voltage.