Method and apparatus for converting direct current to alternating current

• US 7,796,412 B2
• Filed: 03/20/2007
• Issued: 09/14/2010
• Est. Priority Date: 03/23/2006
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Fornage, Martin
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US11/725,763
• Publication Number:
  US 20070221267A1
• Time in Patent Office: 1,274 Days
• Field of Search: 363/21.13, 363/97, 363/131, 323/906, 250/203.4
• US Class Current: 363/97
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• 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 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 the DC and converting the DC to the AC using at least one flyback mode of a plurality of flyback modes of operation of a flyback converter, wherein the plurality of flyback modes comprises at least two of regular flyback, interleaved flyback, and quasi-resonant flyback; and

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

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

a memory for storing data representing the control signals; and

a sequencer for sequentially selecting the data from the memory to produce the control signals.

3. 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 line voltage and coupling at least one sample to the controller.

4. The apparatus of claim 3 wherein the controller selects the at least one flyback mode in response to the at least one sample.

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

6. The apparatus of claim 1, wherein the controller selects the interleaved flyback mode as a result of a power requirement exceeding a power threshold.

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

8. The apparatus of claim 1 wherein the conversion circuit is phase locked to an AC power grid voltage.

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

10. A method for converting direct current (DC) to alternating current (AC), comprising:

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

selecting, in response to monitored signals from the monitoring step, at least one flyback mode from a plurality of flyback modes for operation of a flyback converter, wherein the plurality of flyback modes comprises at least two of regular flyback, interleaved flyback and quasi-resonant flyback; and

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

11. The method of claim 10 wherein the monitored signals comprise at least one of a DC voltage, a DC current, and an AC voltage.

12. The method of claim 11 wherein the selecting is based upon a state of the DC voltage and the DC current.

13. The method of claim 10 wherein the interleaved flyback is selected when a power requirement for the conversion circuit exceeds a predefined power threshold.

14. The method of claim 10 wherein the monitored signals form an address for accessing data representing control signals for selecting the at least one flyback mode.

15. Apparatus for generating solar power comprising:

at least one solar panel for producing direct current (DC) from sunlight;

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

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

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

16. The apparatus of claim 15 wherein the plurality of flyback modes comprises at least two of a regular flyback mode, an interleaved flyback mode, and quasi-resonant flyback mode.

17. The apparatus of claim 16 wherein the interleaved flyback mode utilizes at least two power stages within the micro-inverter.

18. The apparatus of claim 15 wherein the micro-inverter comprises a conversion circuit and a controller, where the controller controls a mode of operation of the conversion circuit.