Device for distributed maximum power tracking for solar arrays

• US 8,963,518 B2
• Filed: 12/09/2011
• Issued: 02/24/2015
• Est. Priority Date: 07/13/2004
• Status: Active Grant

• Current Assignee: Tigo Energy, Inc
• Original Assignee: Tigo Energy, Inc
• Inventors: Wolfs, Peter
• Primary Examiner(s): Behm, Harry
• Assistant Examiner(s): Grubb, Matthew
• Application Number:
  US13/316,388
• Publication Number:
  US 20120146420A1
• Time in Patent Office: 1,173 Days
• Field of Search: 307/5, 307/75, 307/84, 307/77, 323/906, 323/299, 323/284, 323/285, 323/271, 136/244, 363/65
• US Class Current: 323/271
• CPC Class Codes: G05F 1/67 to the maximum power available from a generator, e.g. from solar cell
• CPC Class Codes: G05F 5/00 Systems for regulating electric variables by detecting deviations in the electric input to the system and thereby controlling a device within the system to obtain a regulated output
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• 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 system for providing power from solar cells whereby each cell or cell array is allowed to produce its maximum available power and converted by an operatively connected DC/DC converter. Each cell or cell array has its own DC/DC converter. In one form the system includes one or more solar generators wherein each solar generator has one to nine solar cells; a maximum power tracker operatively associated with each solar generator, each maximum power tracker including a buck type DC/DC converter without an output inductor, each maximum power tracker being operatively connected in series with each other; an inductor operatively connected to the series connected maximum power trackers; and means for providing electrical power from the inductor to load means, wherein each maximum power tracker is controlled so that the operatively associated solar generator operates at its maximum power point to extract maximum available power.

Claims

1. A system, comprising:

a plurality of solar units, each solar unit of the solar units comprising;

a solar generator having at least one solar cell to generate electric power;

only one pair of output connections to provide output; and

a DC/DC converter coupled between the solar generator and the pair of output connections to receive electricity provided by the solar generator in entirety and to provide the output via the pair of output connections, wherein the DC/DC converter includes

a switch,

an energy storage capacitor coupled between the solar generator and the switch, and

a controller configured to control the switch to operate the solar generator at a maximum power point independent of other solar units of the plurality of solar units;

an output inductor; and

a set of wires configured to connect output connections of the solar units and the output inductor in series;

wherein when the switch is turned on, the solar generator and the energy storage capacitor are connected in parallel and further connected in the series connection of the solar units established by the set of wires;

wherein when the switch is turned off,

the solar generator and the energy storage capacitor are electronically disconnected from the series connection, and

the DC/DC converter provides at least one path for the series connection.

2. The system of claim 1, wherein the at least one path includes a diode.

3. The system of claim 1, wherein the DC/DC converter has no inductor.

4. The system of claim 3, wherein the DC/DC converter is a buck-type converter.

5. A method, comprising:

connecting outputs of a plurality of solar units in series to form a series connection, wherein each of the solar units comprising

a solar generator having at least one solar cell to generate electric power, and

a DC/DC converter coupled with the solar generator to receive the electric power generated by the solar generator in entirety and configured to output the electric power through the plurality of solar units connected in series, wherein the DC/DC converter comprises

a switch, and

an energy storage capacitor coupled between the solar generator and the switch;

wherein when the switch is turned on, the solar generator and the energy storage capacitor are connected in parallel for the series connection in the plurality of solar units;

wherein when the switch is turned off,

the solar generator and the energy storage capacitor are electronically disconnected from the series connection, and

the DC/DC converter provides at least one path for the series connection, and

controlling the switch of the DC/DC converter of each of the solar units to operate the respective solar generator at a maximum power point independent of other solar units of the plurality of solar units that are connected in series.

6. The method of claim 5, wherein each of the solar units has an energy storage capacitor and a controller;

and a duty cycle of the DC/DC converter is adjusted via the controller to operate the solar generator at the maximum power point, based on a voltage of the solar generator, and a voltage of the energy storage capacitor.

7. The method of claim 5, further comprising:

coupling an inductor with the plurality of solar units in series to provide the electric power to a load.

8. The method of claim 7, wherein the DC/DC converter comprises a step down converter.

9. The method of claim 8, wherein the inductor is a single inductor shared by DC/DC converters of the solar units connected in series.

10. The method of claim 7, further comprising:

connecting the plurality of solar units to the load including devices that use or store the electric power.

11. The method of claim 5, wherein the at least one path includes a diode.

12. The method of claim 11, wherein the DC/DC converter is a buck-type converter without an output inductor.

13. A method, comprising:

generating electricity in direct current (DC) using a solar generator; and

operating a first switch of a converter, coupled between the solar generator and a series connection of solar generators, according to a duty cycle to allow the solar generator to supply a first current to the series connection of solar generators via the first switch of the converter, wherein

the first switch is controlled to operate the solar generator at a maximum power point independent of other solar generators in the series connection of solar generators;

the converter is configured to allow a second current larger than the first current to flow through the series connection of solar generators, and

the converter includes an energy storage capacitor coupled in parallel with the solar generator and coupled between the solar generator and the first switch;

wherein

when the first switch is turned on, the solar generator provides the first current to the series connection of solar generators, the energy storage capacitor provides a third current, and the second current is equal to or larger than a sum of the first current and the third current; and

wherein, when the first switch is turned off, the solar generator and the energy storage capacitor are electronically disconnected from the series connection of solar generators, and the converter provides at least one path for the series connection of solar generators.

14. The method of claim 13, wherein the solar generator has at least one solar cell;

and the converter has no inductor.

15. The method of claim 14, wherein the converter is a buck-type converter without an output inductor.

16. The method of claim 13, wherein when the first switch is turned on, an output voltage of the converter is substantially equal to an output voltage of the solar generator.

17. The method of claim 16, wherein the at least one path includes at least one of:

a diode,

a second switch, wherein the converter turns off the second switch when the first switch is turned on, and

a synchronous rectifier.

18. The method of claim 13, wherein the converter further comprises a controller to control the first switch according to the duty cycle.

19. The method of claim 18, wherein the controller is to further control the first switch according to at least one of:

a phase shift, and a synchronizing signal.

20. The method of claim 13, wherein the converter is a first converter and the solar generator is a first solar generator;

and the series connection of solar generators further comprises a second solar generator and a second converter connected to the first converter in series, the second converter having at least a second switch, the second solar generator to provide electricity to the series connection of solar generators via the second switch of the second converter, the second converter configured to allow the second current, larger than a current from the second solar generator, to flow through the series connection of solar generators; and

the method further comprises;

operating a second switch of the second converter according to a duty cycle separately from the duty cycle according to which the first switch of the first converter is operated to separately maximize power output from the first solar generator and the power output from the second solar generator.