Method and apparatus for converting direct current to alternating current

• US 20070221267A1
• Filed: 03/20/2007
• Published: 09/27/2007
• Est. Priority Date: 03/23/2006
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: PVI Solutions Incorporated
• Inventors: Fornage, Martin
• Granted Patent: US 7,796,412 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• 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: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 3/285 Single converters with a plurality of output stages connected in parallel parallel operation of a plurality of converters in dc distribution networks H02J1/10
• CPC Class Codes: H02M 3/33515 with digital control
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode
• CPC Class Codes: Y02B 10/10 Photovoltaic [PV]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

A method and apparatus for converting Direct Current (DC) to Alternating Current (AC). The method comprises performing system analysis on at least one of a DC current, DC voltage, or an AC voltage; utilizing the system analysis for selecting at least one conversion parameter; and converting DC to AC utilizing the at least one conversion parameter.

Claims

1. Apparatus for converting Direct Current (DC) to Alternating Current (AC), comprising:

a conversion circuit for receiving a DC voltage and converting the DC voltage to an AC voltage using at least one of a plurality of flyback mode of operation; and

a controller, coupled to the conversion circuit, for generating control signals to select at least one flyback mode from a plurality of flyback modes of operation.

2. The apparatus of claim 1 wherein the controller comprises:

a memory for storing data representing control signals; and

a sequencer for sequentially selecting data from the memory to produce control signals for the at least one selected flyback mode of operation.

3. The apparatus of claim 1 wherein the plurality of flyback modes comprise at least two of regular flyback, interleaved flyback, and quasi-resonant flyback.

4. The apparatus of claim 1, wherein the conversion circuit comprises a sampling circuit for sampling at least one of a DC current, a DC voltage, and an AC voltage and coupling at least one sample to the controller.

5. The apparatus of claim 3 wherein the controller selects at least one flyback mode in response to the samples of at least one of the DC current, DC voltage and AC voltage.

6. The apparatus of claim 1, wherein the controller selects at least one flyback mode to produce effective maximum power point tracking.

7. The apparatus of claim 3, wherein the controller selects the interleaved flyback mode as result of a power requirement exceeding a power threshold.

8. The apparatus of claim 1 wherein flyback mode selection dynamically occurs during an AC voltage cycle.

9. The apparatus of claim 1 wherein the conversion circuit is phase locked to a power grid voltage.

10. The apparatus of claim 1 wherein the conversion circuit comprises an input circuit, at least one power stage and an output circuit.

11. A method for converting direct current to alternating current, comprising:

monitoring at least one of an input signal and output signal of a conversion circuit;

selecting, in response to the monitored signals, at least one flyback mode from a plurality of flyback modes for operation of the conversion circuit; and

converting DC to AC utilizing the conversion circuit operating in the selected at least one flyback mode.

12. The method of claim 11 wherein the monitored input signal and output signal comprise at least one of a DC voltage, a DC current, and an AC voltage.

13. The method of claim 11 wherein the plurality of modes comprise at least two of regular flyback, interleaved flyback and quasi-resonant flyback.

14. The method of claim 12 wherein the selection of the mode is based upon the state of the DC voltage and the DC current.

15. The method of claim 13 wherein the interleaved mode is selected when a power requirement for the conversion circuit exceeds a predefined power threshold.

16. The method of claim 15 wherein the monitored signals for an address for accessing data representing control signals for selecting the mode of operation.

17. Apparatus for generating solar power comprising:

at least one solar panel for producing DC voltage from sunlight;

a micro-inverter coupled to each of the at least one solar panels for converting the DC voltage into AC voltage using at least one selected flyback mode that is selected from a plurality of flyback modes;

an electric panel, coupled to the micro-inverter, for controlling distribution of the AC voltage;

an electric meter, coupled to the electric panel, for measuring the amount of AC voltage that is coupled to a power grid.

18. The apparatus of claim 17 wherein the plurality of modes comprise at least two of a regular flyback mode, an interleaved flyback mode, and quasi-resonant flyback mode.

19. The apparatus of claim 18 wherein the interleaved flyback mode utilizes at least two power stages within the micro-inverter.

20. The apparatus of claim 17 wherein the micro-inverter comprises a conversion circuit and a controller, where the controller controls the mode of operation of the conversion circuit.