Cell-to-grid redundandt photovoltaic system

• US 9,299,861 B2
• Filed: 10/31/2012
• Issued: 03/29/2016
• Est. Priority Date: 06/15/2010
• Status: Active Grant

• Current Assignee: Spectrum Solar, LLC
• Original Assignee: Tenksolar, Inc.
• Inventors: Meyer, Dallas W., Berg, Lowell, Novotny, John, Gross, Shady, Meyer, Forrest C.
• Primary Examiner(s): Bourke, Allison
• Application Number:
  US13/664,885
• Publication Number:
  US 20130062956A1
• Time in Patent Office: 1,245 Days
• Field of Search: 136/244, 307/82
• US Class Current: 1/1
• CPC Class Codes: H01L 31/02008 for solar cells or solar cell modules
• CPC Class Codes: H01L 31/048 Encapsulation of modules
• CPC Class Codes: H01L 31/0504 specially adapted for series or parallel connection of solar cells in a module
• CPC Class Codes: H01R 4/2475 the contact members penetrating the insulation being actuated by screws, nuts or bolts
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02M 7/003 Constructional details, e.g. physical layout, assembly, wiring or busbar connections
• CPC Class Codes: H02S 40/32 comprising DC/AC inverter means associated with the PV module itself, e.g. AC modules
• CPC Class Codes: H02S 40/34 comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
• CPC Class Codes: H02S 40/36 characterised by special electrical interconnection means between two or more PV modules, e.g. electrical module-to-module connection
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: H02S 50/10 Testing of PV devices, e.g. of PV modules or single PV cells testing of semiconductor devices during manufacturing H01L22/00
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

In an embodiment, a photovoltaic system includes multiple photovoltaic modules and a module-to-module bus. Each photovoltaic module defines a first end and a second end opposite the first end. Each photovoltaic module includes multiple photovoltaic cells and multiple converters. Energy generated by each photovoltaic cell has multiple paths through the photovoltaic cells to the second end. The converters are electrically coupled to the photovoltaic cells at the second end such that energy generated by each photovoltaic cell is receivable at any of the converters. The module-to-module bus is electrically coupled to each of the photovoltaic modules. The module-to-module bus has an output. Energy generated by each photovoltaic module is receivable at the output independent of any other of the photovoltaic modules.

Claims

1. A photovoltaic system comprising:

a plurality of photovoltaic modules, each photovoltaic module defining a first end and a second end opposite the first end, wherein each photovoltaic module comprises;

a plurality of photovoltaic cells, wherein energy generated by each photovoltaic cell has multiple paths through the plurality of photovoltaic cells to the second end; and

a plurality of converters electrically coupled to the plurality of photovoltaic cells at the second end such that energy generated by each photovoltaic cell is receivable at any of the plurality of converters; and

a module-to-module bus electrically coupled to each of the plurality of photovoltaic modules, the module-to-module bus having an output, wherein energy generated by each photovoltaic module is receivable at the output independent of any other of the plurality of photovoltaic modules,

wherein;

each of the plurality of photovoltaic modules further comprises;

a circuit card mechanically coupled to the second end; and

a digital controller disposed on the circuit card;

the plurality of converters are disposed on the circuit card; and

the digital controller of each of the photovoltaic modules is configured to;

trickle charge current onto the module-to-module bus when a voltage on the module-to-module bus is less than a minimum threshold to determine whether a capacitive element is attached to the module-to-module bus;

in response to determining that the capacitive element is attached to the module-to-module bus, continue to trickle charge current onto the module-to-module bus until the voltage on the module-to-module bus rises above the minimum threshold;

close a protection relay when the voltage on the module-to-module bus rises above the minimum threshold to ensure zero current switching, the protection relay being electrically coupled between the module-to-module bus and an output bus of the circuit card, the output bus being electrically coupled to outputs of each of the plurality of converters;

operate the plurality of converters in a maximum current mode when the voltage on the module-to-module bus is between the minimum threshold and an intermediate threshold greater than the minimum threshold;

operate the plurality of converters in a constant voltage mode when the voltage on the module-to-module bus is between the intermediate threshold and a maximum threshold greater than the minimum threshold; and

open the protection relay when the voltage on the module-to-module bus rises above the maximum threshold or falls below the minimum threshold.

2. The photovoltaic system of claim 1, wherein:

the plurality of photovoltaic cells are arranged in a plurality of rows, wherein the plurality of rows are electrically coupled in series;

each of the plurality of photovoltaic modules further comprises a plurality of conductive row strips electrically coupling the photovoltaic cells in each row to each other in parallel; and

the multiple paths through the plurality of photovoltaic cells to the second end include the plurality of conductive row strips such that generated current can flow, via the plurality of conductive row strips, around photovoltaic cells with low performance and/or low illumination and through photovoltaic cells with relatively higher performance and/or higher illumination to the second end.

3. The photovoltaic system of claim 1, wherein:

each of the plurality of photovoltaic modules further comprises a continuous backsheet, the continuous backsheet comprising a ground plane for the plurality of photovoltaic cells;

the continuous backsheet is electrically coupled between a first subset of the plurality of photovoltaic cells at the first end and a second subset of the plurality of photovoltaic cells at the second end;

a first end connection between the continuous backsheet and the first subset of the plurality of photovoltaic cells at the first end comprises an anode of the photovoltaic module;

a second end connection between the plurality of converters and the second subset of the plurality of photovoltaic cells at the second end comprises a cathode of the photovoltaic module; and

the continuous backsheet is configured to carry module return current from the cathode to the anode.

4. The photovoltaic system of claim 3, wherein:

the plurality of photovoltaic cells are arranged in a plurality of rows, wherein the plurality of rows are electrically coupled in series, and the plurality of rows includes a first row that includes the first subset of the plurality of photovoltaic cells, and a last row that includes the second subset of the plurality of photovoltaic cells; and

the first end connection comprises;

a ground strip electrically and mechanically coupled to the continuous backsheet at the first end; and

a plurality of serial interconnects electrically and mechanically coupling each photovoltaic cell in the first row to the ground strip.

5. The photovoltaic system of claim 3, wherein the circuit card of each of the plurality of photovoltaic modules further comprises a positive connector and a negative connector, and wherein each of the plurality of photovoltaic modules further comprises:

an internal bus strip extending along a width of each corresponding photovoltaic module, wherein;

the internal bus strip is coupled to a cathode of each of the photovoltaic cells in the second subset of the plurality of photovoltaic cells; and

the internal bus strip includes a tab extending through a slot formed in the continuous backsheet to the positive connector of the circuit card, the tab electrically coupling the internal bus strip to the positive connector of the circuit card; and

one or more tabs extending from the continuous backsheet to the negative connector of the circuit card, the one or more tabs electrically coupling the continuous backsheet to the negative connector of the circuit card.

6. The photovoltaic system of claim 5, wherein the one or more tabs extending from the continuous backsheet ground the circuit card to the continuous backsheet, the one or more tabs including:

an integral tab integrally formed from the continuous backsheet and extending in a plane substantially normal to a plane defined by the continuous backsheet;

or

a discrete tab mechanically and electrically coupled to the continuous backsheet and extending in a plane substantially normal to the plane defined by the continuous backsheet.

7. The photovoltaic system of claim 1, wherein

the plurality of converters are each controlled independently of the others by the digital controller via paired enable and pulse width modulation (PWM) lines from the digital controller to each of the plurality of converters.

8. The photovoltaic system of claim 1, wherein:

the plurality of converters for each of the plurality of photovoltaic modules are operated in pairs;

each operating pair is operated out of phase with other operating pairs; and

each converter in a pair is operated 180 degrees out of phase with the other converter in the pair.

9. The photovoltaic system of claim 1, wherein:

the circuit card includes a negative connector and a positive connector;

each of the plurality of converters is independently electrically coupled to the positive connector via a corresponding fuse; and

in the event of a finite resistance short failure in one of the plurality of converters, the digital controller is configured to;

route all current from the plurality of photovoltaic cells through the one of the plurality of converters until the corresponding fuse opens; and

in response to opening the fuse, resume normal operation using at least some remaining ones of the plurality of converters.

10. The photovoltaic system of claim 1, wherein the digital controller is powered solely by energy generated by the photovoltaic module.

11. The photovoltaic system of claim 1, wherein:

the circuit card includes a positive connector electrically coupled to a row of the plurality of photovoltaic cells at the second end;

the plurality of converters are disposed on the circuit card in a line with a spacing of less than three millimeters between adjacent converters; and

each of the plurality of converters is disposed within a range of five to ten millimeters from the positive connector.

12. The photovoltaic system of claim 1, wherein each of the plurality of photovoltaic modules further includes an optical signal source communicatively coupled to the digital controller and mounted to the circuit card such that optical signals emitted by the optical signal source are visible from a front of each corresponding photovoltaic module.

13. The photovoltaic system of claim 12, wherein the digital controller is configured to operate the optical signal source to emit optical signals comprising status information.

14. The photovoltaic system of claim 13, wherein the status information comprises at least one of the following for the corresponding photovoltaic module:

power and fault codes, a module serial ID, full fault logs, accumulated energy production, temperature, or a number of on/off cycles.

15. The photovoltaic system of claim 1, wherein each of the plurality of photovoltaic modules further comprises a radio frequency (RF)-emitting device communicatively coupled to the digital controller, the digital controller being configured to operate the RF-emitting device to transmit information to others of the plurality of photovoltaic modules and/or to a data collection device included in the photovoltaic system.

16. The photovoltaic system of claim 1, wherein each of the plurality of photovoltaic modules further comprises an undermount assembly within which the circuit card is disposed, the undermount assembly including a housing comprising:

a main body; and

a plurality of feet extending from the main body, the plurality of feet being substantially coplanar,

wherein;

the undermount assembly is mechanically coupled to a continuous backsheet of the corresponding photovoltaic module using an adhesive or tape disposed between the continuous backsheet and the plurality of feet; and

the main body defines two slots through which two corresponding risers pass through the main body to electrically couple to the circuit card.

17. The photovoltaic system of claim 16, wherein:

each undermount assembly further comprises a black cover thermally coupled to the circuit card;

the black cover includes one or more protrusions exposed external to the undermount assembly that dissipate thermal energy away from the undermount assembly; and

the black cover includes an edge in direct contact with or within 8 millimeters of a frame of the corresponding photovoltaic module that dissipates heat into the frame and away from the undermount assembly.

18. The photovoltaic system of claim 16, wherein:

each of the two risers includes;

a base defining a tapped hole; and

a C-shaped end opposite the base, the C-shaped end including a top and a bottom, the top including an insulation-penetrating member and the bottom including a clamping member, the top being closer to the base than the bottom;

the undermount assembly for each of the plurality of photovoltaic modules further comprises;

two nests extending from a bottom surface of the main body, each of the two nests being integral to the main body or separately attached thereto, each of the two nests defining a slot in communication with a different one of the slots defined by the main body, each riser passing through a slot defined in a corresponding one of the nests and a corresponding slot defined in the main body;

two caps, one each attached to a corresponding one of the two nests; and

two screws, one each securing the circuit card to a corresponding one of the risers through the tapped hole defined in the base of the riser;

the module-to-module bus comprises two wires, each having a cross-sectional area greater than or equal to 15 square millimeters and each having an insulating jacket;

each of the two wires is disposed within the C-shaped end of each of the two risers without stripping the insulating jacket from the two wires during installation;

the clamping member of each of the two risers being clamped during installation to clamp a corresponding one of the two wires against the insulation-penetrating member of each of the two risers such that the insulation-penetrating member penetrates the insulating jacket and electrically couples the corresponding wire to the corresponding riser;

the C-shaped end of each of the two risers extends from a corresponding one of the two nests;

after electrically coupling the corresponding wire to the corresponding riser, each of the two caps is attached to a corresponding one of the two nests to enclose the C-shaped end of each of the two risers and a portion of each of the two wires where the insulating jacket has been penetrated within a corresponding one of the nests and a corresponding one of the caps and to protect a corresponding electrical connection between the C-shaped end and the corresponding wire from environmental contaminants.

19. The photovoltaic system of claim 1, wherein each of the plurality of converters is operated with a duty cycle D in a range from [(V_out−

V_in)/V_out−

0.05]<

D<

0.75, where V_out and V_in are an output voltage and an input voltage of the corresponding converter.

20. The photovoltaic system of claim 1, wherein each of the plurality of photovoltaic modules further comprises:

measurement circuitry configured to measure an output current to the module-to-module bus or an input current from the module-to-module bus; and

a digital controller configured to, based on the measurement, monitor an offset between the output current and the input current and/or to limit output current when the output current exceeds a preset limit.

21. A photovoltaic system comprising:

a plurality of photovoltaic modules, each photovoltaic module defining a first end and a second end opposite the first end, wherein each photovoltaic module comprises;

a plurality of photovoltaic cells, wherein energy generated by each photovoltaic cell has multiple paths through the plurality of photovoltaic cells to the second end; and

a plurality of converters electrically coupled to the plurality of photovoltaic cells at the second end such that energy generated by each photovoltaic cell is receivable at any of the plurality of converters;

a module-to-module bus electrically coupled to each of the plurality of photovoltaic modules such that the plurality of photovoltaic modules are electrically connected in parallel; and

a plurality of inverters electrically coupled to the module-to-module bus such that energy generated by each photovoltaic module is receivable at any of the plurality of inverters;

wherein;

each of the plurality of photovoltaic modules further comprises;

a circuit card mechanically coupled to the second end; and

a digital controller disposed on the circuit card;

the plurality of converters are disposed on the circuit card; and

the digital controller of each of the photovoltaic modules is configured to;

trickle charge current onto the module-to-module bus when a voltage on the module-to-module bus is less than a minimum threshold to determine whether a capacitive element is attached to the module-to-module bus;

in response to determining that the capacitive element is attached to the module-to-module bus, continue to trickle charge current onto the module-to-module bus until the voltage on the module-to-module bus rises above the minimum threshold;

close a protection relay when the voltage on the module-to-module bus rises above the minimum threshold to ensure zero current switching, the protection relay being electrically coupled between the module-to-module bus and an output bus of the circuit card, the output bus being electrically coupled to outputs of each of the plurality of converters;

operate the plurality of converters in a maximum current mode when the voltage on the module-to-module bus is between the minimum threshold and an intermediate threshold greater than the minimum threshold;

operate the plurality of converters in a constant voltage mode when the voltage on the module-to-module bus is between the intermediate threshold and a maximum threshold greater than the minimum threshold; and

open the protection relay when the voltage on the module-to-module bus rises above the maximum threshold or falls below the minimum threshold.

22. The photovoltaic system of claim 21, wherein the module-to-module bus comprises a continuous and uninterrupted wire to which each of the plurality of photovoltaic modules is electrically coupled.

23. The photovoltaic system of claim 21, wherein one or more energy storage devices are coupled in parallel to the module-to-module bus.

24. The photovoltaic system of claim 23, wherein based on a DC setpoint and AC curtailment of each of the plurality of inverters and on a current state of charge of the one or more energy storage devices, current flows through the module-to-module bus and one or more of the plurality of inverters:

into the one or more energy storage devices from any or all phases of a multiphase AC power grid to which each of the plurality of inverters is coupled;

or

from the one or more energy storage devices into any or all phases of the multiphase AC power grid.

25. The photovoltaic system of claim 21, wherein each of the plurality of inverters is configured to be further coupled to any or all three phases of a three-phase AC power grid.

26. The photovoltaic system of claim 21, wherein the plurality of inverters comprise three inverters, and wherein each of the three inverters is further coupled to a different phase of a three-phase AC power grid using a Wye or Delta connection.

27. The photovoltaic system of claim 26, wherein each of the three inverters has a different DC setpoint and AC curtailment such that during operation current selectively flows:

to different phases of the three-phase AC power grid;

into one or more energy storage devices coupled in parallel to the module-to-module bus via the module-to-module bus; and

/or

from the one or more energy storage devices via the module-to-module bus.

28. The photovoltaic system of claim 26, wherein each of the three inverters has a different DC setpoint such that during operation current flows:

from one or more phases of the three-phase AC power grid through one or more of the plurality of inverters with a relatively high DC setpoint to the module-to-module bus; and

from the module-to-module bus through one or more of the plurality of inverters with a relatively low DC setpoint to one or more other phases of the three-phase AC power grid.

29. The photovoltaic system of claim 21, wherein each of the plurality of inverters may be selectively disabled and enabled based on one or more criteria.

30. The photovoltaic system of claim 21, wherein the plurality of inverters are communicatively coupled together and are configured to communicate with each other to coordinate control of inverter-specific settings, the inverter-specific settings including a DC setpoint and AC curtailment of each of the plurality of inverters.