Method and System for Optimizing Power Generated by a Photovoltaic System

• US 20130241294A1
• Filed: 09/23/2011
• Published: 09/19/2013
• Est. Priority Date: 09/23/2010
• Status: Active Application

• Current Assignee: Hybridyne Power Electronics Inc. (Atlantic Power & Infrastructure Corp.)
• Original Assignee: Hybridyne Power Electronics Inc. (Atlantic Power & Infrastructure Corp.)
• Inventors: Cleland, Thomas
• Granted Patent: US 10,847,972 B2
• Time in Patent Office: Days
• US Class Current: 307/71
• CPC Class Codes: H01L 31/02021 for solar cells electrical connection means, e.g. junction boxes, specially adapted for structural association with photovoltaic modules H02S40/34
• CPC Class Codes: H02J 1/10 Parallel operation of dc sources
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

In one embodiment, a photovoltaic (PV) power generation system includes a plurality of PV arrays coupled to an automatic switchbox that connects the one or more PV arrays in series or in parallel with each other based at least in part on output voltage of the switchbox.

In this embodiment, the automatic switchbox monitors the output voltage and ensures that the output voltage is within a predetermined operational range. If the output voltage exceeds a first predetermined voltage, then the array switchbox electrically couples one or more PV arrays in parallel with each other, which reduces the output voltage within the predetermined operational range. If the output voltage falls below a second predetermined voltage, the switchbox connects one or more PV arrays in series with each other, which increases the output voltage to within the predetermined range.

Claims

1. An automatic switchbox for combining one or more PV devices in series or in parallel with each other in a photo-voltaic (PV) power generation system, the switchbox comprising:

an input portion, an output portion, and a pair of bus lines coupling the input portion to the output portion, wherein the input portion is capable of receiving power from a plurality of PV devices;

a voltage sensor coupled to the pair of bus lines at the output portion; and

a first plurality of nodes configured to couple one or more PV devices either in parallel or in series with each other based at least in part on the output voltages, wherein each node is associated with any two PV devices.

2. The switchbox of claim 1, further comprising an automatic node controller for controlling the nodes based at least in part on the voltage sensed by the voltage sensor at the output portion, wherein the node controller is electrically coupled to the voltage sensor and to the first plurality of nodes.

3. The switchbox of claim 1:

wherein the pair of bus lines includes a positive direct current (DC) bus line and a negative DC bus line, and wherein the negative DC bus line is capable of receiving power generated from the plurality of PV devices;

wherein the input portion comprises a plurality of input links and a corresponding plurality of output input links, wherein each input link and corresponding output link is associated with a PV device;

wherein each node is connected to an input DC link of one PV device and an output DC link of another PV device; and

wherein the voltage sensor is connected to the pair of bus lines at the output portion.

4. The switchbox of claim 3, wherein a quantity of the first plurality of nodes comprises n nodes, and a quantity of PV devices comprises (n+1) PV devices.

5. The switchbox of claim 4, wherein an n^th node is connected to both an output link of an n^th PV device and an input link of an (n+1)^th PV device.

6. The switchbox of claim 5, wherein the plurality of PV devices comprises a plurality of PV arrays, wherein the switchbox includes forty-one nodes, wherein the switchbox is capable of receiving power from forty-two PV arrays, wherein each PV array in turn includes two PV strings connected in series with each other.

7. The switchbox of claim 5, wherein the n^th node is configured to selectively couple the output link of the n^th PV device either to the negative DC bus line or to the input link of the (n+1)^th PV device and wherein the nth node is configured to selectively either connect the input link of the (n+1)^th PV device to the positive bus line or disconnect the input link of the (n+1)^th PV device from the positive bus line.

8. The switchbox of claim 7,

wherein the n^th node is configured to operate in an active state or a rest state, wherein the when the n^th node is in the active state, the n^th PV device is connected in parallel with one or more PV devices and when the n^th node is in the rest state, the n^th PV device is connected in series with one or more PV devices;

wherein when the n^th node is in the active state, the output link of the n^th PV device is coupled to the negative bus line and the input link of the (n+1)^th PV device is coupled to the positive bus line; and

wherein when the n^th node is in the rest state, the output link of the n^th PV device is coupled to the input link of the (n+1)^th PV device and the input link of the (n+1)^th PV device is disconnected from the positive bus line.

9. The switchbox of claim 8, wherein at least one node includes at least one double pole relay switch comprising a first contact and a second contact, wherein the first contact and the second contact are interlocked so that they move in unison.

10. The switchbox of claim 9, wherein the first contact of an n^th node is connected to the output link of the n^th PV device and the second contact of an n^th node is connected to the input link of the (n+1)^th PV device.

11. The switchbox of claim 10, wherein the first contact of an n^th node is configured to selectively couple the output link of the n^th PV device either to the negative DC bus line or to the input link of the (n+1)^th PV device and second contact of an n^th node is configured to selectively either connect the input link of the (n+1)^th PV device to the positive bus line or disconnect the input link of the (n+1)^th PV device from the positive bus line.

12. The switchbox of claim 11,

wherein when the first contact of an n^th node is coupled to the negative bus line, the interlocked second contact of the n^th node is coupled to the positive bus line, the n^th PV device is connected in parallel with one or more PV devices;

and wherein when the first contact of an n^th node is coupled to the input link of the (n+1)^th PV device, the interlocked second contact is disconnected from the positive bus line, the n^th PV device is connected in series with one or more PV devices.

13. The switchbox of claim 1, wherein the plurality of PV devices comprises a plurality of devices that convert light into electricity, wherein the plurality of PV devices are selected from the group consisting of PV arrays and PV strings.

14. A method comprising:

monitoring an output voltage for a plurality of PV devices at a pair of bus lines, wherein the output voltage is an aggregate voltage generated by the plurality of PV devices;

when the output voltage is greater than a first predetermined value, connecting one or more PV devices in parallel with each other; and

when the output voltage is less than second predetermined value, connecting one or more PV devices in series with each other.

15. The method of claim 14,

wherein the plurality of PV devices comprises a plurality of devices that convert light into electricity, wherein the plurality of PV devices are selected from the group consisting of PV arrays and PV strings;

wherein each PV device includes an input link and output link;

wherein the pair of bus lines comprises a positive DC bus line and a negative DC bus lines;

wherein the plurality of PV devices are connected in series or in parallel each other at a plurality of nodes;

wherein a quantity of the first plurality of nodes comprises “

n”

nodes, and a quantity of PV devices comprises (n+1) PV devices; and

wherein an n^th node is connected to both an output link of an n^th PV device and an input link of an (n+1)^th PV device.

16. The method of claim 15, wherein when the output voltage is greater than a first predetermined value, connecting one or more PV devices in parallel with each other comprises selecting a node and then connecting, at the selected node, one or more PV devices associated with the selected in parallel with each other, wherein selecting the node is selected at random.

17. The method of claim 15, wherein when the output voltage is less than second predetermined value, connecting one or more PV devices in series with each other comprises selecting a node and then connecting, at the selected node, one or more PV devices associated with the selected in series with each other, wherein the node is selected at random.

18. The method of claim 15, connecting one or more PV devices in parallel with each other comprises coupling the output link of the n^th PV device to the negative bus line coupling the input link of the (n+1)^th PV device to the negative bus line.

19. The method of claim 15, connecting one or more PV devices in series with each other comprises coupling the output link of the n^th PV device to the input link of the (n+1)^th PV device and disconnecting the input link of the (n+1)^th PV device from the positive bus line.

20. The method of claim 14 wherein when the output voltage is greater than a first predetermined value, connecting one or more PV devices in parallel with each other comprises when the output voltage is greater than 550 volts, connecting one or more PV devices in parallel with each other.

21. The method of claim 14, wherein when the output voltage is less than second predetermined value, connecting one or more PV devices in series with each other comprises when the output voltage is less than 350 volts.