Photovoltaic inverter interface device, system, and method

• US 7,964,837 B2
• Filed: 12/31/2007
• Issued: 06/21/2011
• Est. Priority Date: 12/31/2007
• Status: Active Grant

• Current Assignee: SMA Solar Technology AG
• Original Assignee: Advanced Energy Industries Incorporated
• Inventors: Seymour, Eric, Gilmore, Jack A.
• Primary Examiner(s): Sohn; Seung C
• Application Number:
  US11/967,933
• Publication Number:
  US 20090167097A1
• Time in Patent Office: 1,268 Days
• Field of Search: 502/14.R, 502/141, 320/128, 320/140, 136291-293
• US Class Current: 250/214.00R
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 136/291 Applications

Abstract

A photovoltaic system, method and apparatus are disclosed. In an exemplary embodiment, the system includes a first and second inputs adapted to couple to a first and second rails of a photovoltaic array; an inverter configured to convert DC power from the photovoltaic array to AC power; and an interface portion coupled to the first and second inputs and the inverter, the interface portion configured to isolate at least one of the first and second inputs from the inverter and to modulate an application of a voltage from the photovoltaic array to the inverter so as to increase a load on the photovoltaic array and to reduce the voltage applied from the photovoltaic array to the inverter.

Claims

1. A photovoltaic system comprising:

a first and second inputs adapted to couple to a first and second rails of a photovoltaic array;

an inverter configured to convert DC power from the photovoltaic array to AC power; and

an interface portion coupled to the first and second inputs and the inverter, the interface portion configured to isolate at least one of the first and second inputs from the inverter and to modulate an application of a voltage from the photovoltaic array to the inverter so as to increase a load on the photovoltaic array and to reduce the voltage applied from the photovoltaic array to the inverter.

2. The system of claim 1, wherein the interface portion includes

a series switch arranged in parallel with an isolation switch, each of the series and the isolation switches coupled to one of the first and second inputs, the isolation switch configured to open so as to isolate the one of the first and second inputs from the inverter, and the series switch configured to be capable of closing for successively longer times so as to modulate the application of the voltage from the photovoltaic array to the inverter.

3. The system of claim 2, wherein the series switch includes an insulated gate bipolar transistor.

4. The system of claim 1, wherein the interface portion includes:

a shunt switch arranged across the first and second inputs, the shunt switch configured to close for successively shorter times so as to modulate the application of the voltage from the photovoltaic array to the inverter.

5. The system of claim 1, wherein the interface portion includes:

a series switch arranged in parallel with an isolation switch, each of the series and the isolation switches coupled to one of the first and second inputs, the isolation switch configured to open to isolate the one of the first and second inputs from the inverter, and the series switch configured to close for successively longer times so as to modulate the application of the voltage from the photovoltaic array to the inverter; and

a shunt switch arranged across the first and second inputs, the shunt switch configured to close for successively longer periods of time so as to modulate the application of the voltage from the photovoltaic array to the inverter.

6. The system of claim 5, wherein the series switch is adapted to close for successively longer times so as to successively increase a load on the photovoltaic array, and the shunt switch is configured to close for successively longer periods of time so as to decrease an inverter load placed in the photovoltaic array.

7. The system of claim 1, wherein the interface portion is configured to reduce the voltage applied from the photovoltaic array to the inverter from a voltage that is greater than 1000 Volts to a voltage that is less than 1000 Volts.

8. A method for interfacing a photovoltaic array with an inverter comprising:

electrically isolating the photovoltaic array from the inverter;

applying an initial voltage at an output of a photovoltaic array;

modulating a load placed on the photovoltaic array so as to provide a reduced voltage at the output of the photovoltaic array; and

utilizing the reduced voltage to apply power to the inverter.

9. The method of claim 8, wherein the electrically isolating a photovoltaic array from an inverter includes isolating one rail of the photovoltaic array from the inverter.

10. The method of claim 8, wherein the initial voltage applied at the output of the photovoltaic array exceeds 1300 Volts and wherein the reduced voltage is less than 1000 Volts.

11. The method of claim 8, wherein the modulating includes successively placing the load on the photovoltaic array for longer periods of time.

12. The method of claim 8, including electrically coupling, after the reduced voltage from the photovoltaic array reaches a desirable voltage, the photovoltaic array to the inverter.

13. The method of claim 12, wherein the initial voltage is higher than a design-voltage of the inverter.

14. The method of claim 8, including:

shunting current away from the inverter so as to reduce the voltage applied from the photovoltaic array to the inverter; and

electrically isolating the photovoltaic array from the inverter, subsequent to the shunting, so as to remove the inverter from the photovoltaic array.

15. A photovoltaic interface device comprising:

two inputs capable of coupling to a photovoltaic array, the inputs configured to receive an initial voltage applied by the photovoltaic array;

two outputs capable of coupling to an inverter, the outputs configured to apply an operating voltage to the inverter; and

a switching segment configured to gradually place a load across the two inputs so as to reduce the initial voltage applied by the photovoltaic array to the operating voltage of the inverter.

16. The photovoltaic interface of claim 15, wherein the switching segment includes a series switch arranged in parallel with an isolation switch, each of the series and the isolation switches coupled to one of the first and second inputs, the isolation switch configured to open so as to isolate the one of the first and second inputs from the inverter, and the series switch configured to be capable of closing for successively longer times so as to modulate the application of the voltage from the photovoltaic array to the inverter.

17. The photovoltaic interface of claim 16, wherein the switching segment includes a shunt switch disposed across the first and second inputs.

18. The photovoltaic interface of claim 16, wherein the switching segment includes:

a series switch arranged series with at least one of the first and second inputs, the series switch configured to be duty cycled from a low duty cycle to a high duty cycle so as to gradually couple the photovoltaic array to the inverter.

19. The photovoltaic interface of claim 18 wherein the switching segment includes:

a shunt switch disposed across the first and second inputs, the shunt switch configured to close so as to enable the inverter to be removed from the photovoltaic array without exposing the inverter to damaging currents.