Methods and apparatuses for photovoltaic power management

• US 8,390,147 B2
• Filed: 02/11/2010
• Issued: 03/05/2013
• Est. Priority Date: 05/13/2009
• Status: Expired due to Fees

• Current Assignee: Solar Semiconductor Incorporated
• Original Assignee: Solar Semiconductor Incorporated
• Inventors: Stauth, Jason T., Seeman, Michael D., Surana, Sonesh
• Primary Examiner(s): AMAYA, CARLOS DAVID
• Application Number:
  US12/704,300
• Publication Number:
  US 20100289337A1
• Time in Patent Office: 1,118 Days
• Field of Search: 307/77, 307/85, 307/86, 136/244
• US Class Current: 307/77
• 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: H02J 7/0019 using switched or multiplexed charge circuits
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Methods and apparatuses for equalizing voltages across a plurality of photovoltaic units connected in series are provided. The apparatus may include a plurality of energy storage devices. In a first configuration, each of the energy storage devices is configured to be connected in parallel with one of a first set of the photovoltaic units. In a second configuration, each of the energy storage devices is configured to be connected in parallel with one of a second set of the photovoltaic units. The apparatus may also include a plurality of switches configured to switch between the first configuration and the second configuration, to equalize the voltages across the photovoltaic units.

Claims

1. An apparatus for equalizing voltages across a plurality of photovoltaic units connected in series, the apparatus comprising:

a plurality of energy storage devices, wherein;

in a first configuration, each of the energy storage devices is configured to be connected in parallel with one of a first set of the photovoltaic units, and

in a second configuration, each of the energy storage devices is configured to be connected in parallel with one of a second set of the photovoltaic units; and

a plurality of switches configured to switch between the first configuration and the second configuration, to equalize the voltages across the photovoltaic units, wherein;

each of the energy storage devices comprises a circuit having an impedance that is resonant at one or more frequencies, and

the circuit comprises an inductor and a capacitor.

2. The apparatus of claim 1, wherein the inductor and the capacitor are connected in series.

3. The apparatus of claim 2, wherein the inductor comprises at least one of a discrete inductor on a printed circuit board, interconnect layers of a printed circuit board, interconnect layers of an integrated circuit, bondwires that connect an integrated circuit and a printed circuit board, and interconnect wiring that connects printed circuit boards.

4. The apparatus of claim 1, wherein the capacitor has a substantial effective series inductance.

5. The apparatus of claim 1, further comprising a controller configured to output a drive signal to the switches at a switching frequency to control switching of the switches.

6. The apparatus of claim 5, wherein the switching frequency or a harmonic of the switching frequency equals a resonant frequency of at least one of the energy storage devices.

7. The apparatus of claim 1, wherein each of the photovoltaic units comprises a photovoltaic cell.

8. The apparatus of claim 1, wherein each of the photovoltaic units comprises a string of photovoltaic cells that are connected in series.

9. The apparatus of claim 1, wherein each of the photovoltaic units comprises a module that includes at least one string of photovoltaic cells that are connected in series.

10. The apparatus of claim 1, further comprising:

a plurality of bypass energy storage devices, each of which is configured in parallel with one of the photovoltaic units.

11. The apparatus of claim 10, wherein the bypass energy storage devices are capacitors.

12. The apparatus of claim 1, wherein each of the switches comprises a single-pole, double-throw switch that includes at least one MOSFET.

13. The apparatus of claim 1, further comprising:

a power point tracking converter that identifies an aggregate maximum power point for the plurality of photovoltaic units;

wherein the voltages across the photovoltaic units are determined based on the aggregate maximum power point.

14. The apparatus of claim 13, wherein:

the power point tracking converter identifies an individual maximum power point for each of the plurality of photovoltaic units; and

the voltages across the photovoltaic units are determined based on the aggregate maximum power point and the individual maximum power points.

15. The apparatus of claim 13, wherein:

the power point tracking converter identifies the aggregate maximum power point for the plurality of photovoltaic units and another set of photovoltaic units that is connected in parallel with the plurality of photovoltaic units.

16. The apparatus of claim 1, further comprising:

a connecting circuit configured to provide a connection to an external apparatus, the connecting circuit comprising;

a connecting energy storage device; and

a connecting switch connected to the connecting energy storage device;

wherein;

in the first configuration, the connecting energy storage device is configured to be connected in parallel with a photovoltaic unit of the external apparatus via the connecting switch, and

in the second configuration, the connecting energy storage device is configured to be connected in parallel with one of the photovoltaic units of the apparatus via the connecting switch.

17. The apparatus of claim 16, wherein the connecting circuit further comprises:

a connecting bypass energy storage device, which is configured to filter the voltage across the photovoltaic unit of the apparatus that is connected in parallel with the connecting energy storage device in the second configuration.

18. A multi-stage apparatus for equalizing voltages across a plurality of photovoltaic modules connected in series, wherein each of the photovoltaic modules comprises a plurality of photovoltaic units connected in series, the multi-stage apparatus comprising:

a plurality of apparatuses, each of which comprises;

a plurality of energy storage devices, wherein;

in a first configuration, each of the energy storage devices is configured to be connected in parallel with one of a first set of the photovoltaic units within one of the modules, and

in a second configuration, each of the energy storage devices is configured to be connected in parallel with one of a second set of the photovoltaic units within the one of the modules;

a plurality of switches configured to switch between the first configuration and the second configuration; and

a connecting circuit configured to provide a connection between the apparatus and an adjacent apparatus among the plurality of apparatuses, the connecting circuit comprising;

a connecting energy storage device; and

a connecting switch connected to the connecting energy storage device;

wherein;

in the first configuration, the connecting energy storage device is configured to be connected in parallel with a photovoltaic unit of the adjacent apparatus via the connecting switch, and

in the second configuration, the connecting energy storage device is configured to be connected in parallel with one of the photovoltaic units of the apparatus via the connecting switch; and

a plurality of connectors configured to connect each of the apparatuses to an adjacent one of the apparatuses;

wherein;

switching between the first configuration and the second configuration equalizes the voltages across the photovoltaic units of all of the photovoltaic modules,

each of the energy storage devices comprises a circuit having an impedance that is resonant at one or more frequencies, and

the circuit comprises an inductor and a capacitor.

19. A method of equalizing voltages across photovoltaic units connected in series, the method comprising:

in a first configuration, storing a first energy from the photovoltaic units in a plurality of energy storage devices, wherein each of the energy storage devices is connected in parallel with one of a first set of the photovoltaic units;

in a second configuration, storing a second energy from the photovoltaic units in the plurality of energy storage devices, wherein each of the energy storage devices is connected in parallel with one of a second set of the photovoltaic units; and

switching between the first configuration and the second configuration until the voltages across the photovoltaic units are substantially equal, wherein;

each of the energy storage devices comprises a circuit having an impedance that is resonant at one or more frequencies, and

the circuit comprises an inductor and a capacitor.

20. The method of claim 19, wherein a frequency of the switching between the first configuration and the second configuration equals a resonant frequency of the energy storage devices.

21. The method of claim 19, further comprising:

after the switching between the first configuration and the second configuration, sending an energy equal to a difference between the first energy and the second energy to a plurality of bypass energy storage devices.

22. The method of claim 19, further comprising:

identifying an aggregate maximum power point for the plurality of photovoltaic units; and

determining the voltages across the photovoltaic units based on the aggregate maximum power point.

23. The method of claim 22, further comprising:

identifying an individual maximum power point for each of the plurality of photovoltaic units;

wherein the voltages across the photovoltaic units are determined based on the aggregate maximum power point and the individual maximum power points.

24. The method of claim 22, wherein the aggregate maximum power point is identified for the plurality of photovoltaic units and another set of photovoltaic units that is connected in parallel with the plurality of photovoltaic units.

25. An apparatus for equalizing voltages across a plurality of photovoltaic units connected in series, the apparatus comprising:

a plurality of energy storage devices, wherein;

in a first configuration, a first energy storage device is configured to be connected in parallel with a first photovoltaic unit, and a second energy storage device is configured to be connected in parallel with a second photovoltaic unit; and

in a second configuration, the first energy storage device is configured to be connected in parallel with the second photovoltaic unit, and the second energy storage device is configured to be connected in parallel with a third photovoltaic unit; and

a plurality of switches configured to switch between the first configuration and the second configuration, to equalize the voltages across the photovoltaic units, wherein;

each of the energy storage devices comprises a circuit having an impedance that is resonant at one or more frequencies, and

the circuit comprises an inductor and a capacitor.

26. An apparatus for equalizing voltages across a plurality of photovoltaic units connected in series, the apparatus comprising:

an energy storage device, wherein;

in a first configuration, the energy storage device is configured to be connected in parallel with a first one of the photovoltaic units, and

in a second configuration, the energy storage device is configured to be connected in parallel with a second one of the photovoltaic units; and

a switch configured to switch between the first configuration and the second configuration, to equalize the voltages across the photovoltaic units, wherein;

the energy storage device comprises a circuit having an impedance that is resonant at one or more frequencies, and

the circuit comprises an inductor and a capacitor.