Remotely controlled photovoltaic string combiner

• US 10,205,324 B2
• Filed: 06/24/2015
• Issued: 02/12/2019
• Est. Priority Date: 05/08/2011
• Status: Active Grant

• Current Assignee: Koolbridge Solar, Inc.
• Original Assignee: Koolbridge Solar, Inc.
• Inventors: Dent, Paul Wilkinson
• Primary Examiner(s): Amaya, Carlos
• Application Number:
  US14/749,339
• Publication Number:
  US 20150295413A1
• Time in Patent Office: 1,329 Days
• Field of Search: 307 66
• CPC Class Codes: H02H 3/16 responsive to fault current to earth, frame or mass with balanced or differential arrangement H02H3/26 ; monitoring earth connection H02H5/105
• CPC Class Codes: H02J 2300/00 Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
• CPC Class Codes: H02J 2300/22 The renewable source being solar energy
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/007 Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing uninterruptable power supply H02J9/00
• 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 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: H02J 9/061 for DC powered loads
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: Y02A 30/00 Adapting or protecting infrastructure or their operation
• CPC Class Codes: Y02B 10/10 Photovoltaic [PV]
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

A remote-controlled photovoltaic string combiner is described that selects strings to be combined to a first photovoltaic output circuit or to a second photovoltaic output for the purpose of either controlling the charging of a battery connected to the first photovoltaic output circuit or for diverting current to a diversion load such as a grid-tie inverter. Strings are selected by energizing relays from one or other inverter such that when neither inverter is operating, all strings are deselected and both photovoltaic output circuits are de-energized.

Claims

1. A remote-controlled photovoltaic string combiner operative to selectively combine current generated by each of a plurality of strings of photovoltaic panels into one or more combined output currents, comprising:

first positive and negative combiner output terminals operative to output a first combined current to one or more first loads;

a connection or communication interface to a remote controller circuit; and

a plurality of per-string circuits, each comprising

positive and negative input terminals operative to receive current from a corresponding photovoltaic string;

first positive and negative output terminals connected to the first combiner output terminals;

a first relay connected to the input terminals and having normally-open terminals connected to the first output terminals, the first relay operative to deliver current from the input terminals to the first output terminals when energized by a first control signal from the controller circuit, and to inhibit current from the input terminals reaching the first output terminals when not energized by the first control signal;

wherein the remote controller circuit outputs a separate first control signal for each per-string circuit, thereby selectively combining current from none, some, or all of the photovoltaic strings into the first combined output current; and

a first ganged switch interposed between the remote controller circuit and the string combiner, the first ganged switch operative to interrupt all first control signals such that no photovoltaic string outputs current to the first combiner output.

2. The remote-controlled string combiner of claim 1, further comprising:

second positive and negative combiner output terminals operative to output a second combined current to one or more second loads; and

wherein each per-string circuit further comprises

second positive and negative output terminals connected to the second combiner output terminals; and

a second relay connected to normally-closed terminals of the first relay and having normally-open terminals connected to the second output terminals, the second relay operative to deliver current from the first relay to the second output terminals when the first relay is not energized by the first control signal and the second relay is energized by a second control signal from the controller circuit, and to inhibit current from the first relay reaching the second output terminals when the first relay is not energized by the first control signal and the second relay is not energized by the second control signal;

wherein the remote controller circuit outputs a separate second control signal for each per-string circuit, thereby selectively combining current from none, some, or all of the photovoltaic strings which are not selected to provide current to the first combined output, into the second combined output current.

3. The remote-controlled string combiner of claim 2 wherein each per-string circuit further comprises

positive and negative terminals of a test port;

and

wherein normally-closed terminals of the second relay are connected to the test port terminals;

wherein the connected photovoltaic string voltage and current are present at the test port when both the first and second control signals are not asserted to energize the respective relays.

4. The remote-controlled string combiner of claim 1 wherein each per-string circuit further comprises:

fuses interposed between the input terminals and the first relay; and

a snubber circuit interposed between the fuses and the first relay, the snubber circuit comprising

a capacitor in series with a parallel connection of a first diode and resistor, shunted between the positive and negative conductors, and operative to protect the relay inputs from inrush current and arcing upon making or breaking; and

a blocking diode connected to the positive relay input terminal, and operative to prevent reverse current flow to the connected photovoltaic string.

5. The remote-controlled string combiner of claim 4, wherein the blocking diode is operative to prevent one or more shadowed photovoltaic strings from robbing current from illuminated photovoltaic strings.

6. The remote-controlled string combiner of claim 4, wherein the blocking diode is operative to limit reverse inrush current from the first combiner output terminals when the first relay is energized and the first combiner output terminals are already energized from one or more other per-string circuits.

7. The remote-controlled string combiner of claim 1 configured to be used as a battery charge controller by remotely selecting the photovoltaic string currents to be combined based on the charge state of a battery connected to the first combiner output terminals.

8. The remote-controlled string combiner of claim 1 wherein the combiner is disposed physically proximate the photovoltaic panels.

9. The remote-controlled string combiner of claim 8 wherein a remote controller circuit is disposed remotely from the combiner and photovoltaic panels, and provides separate first control signals for each per-string circuit via a cable or communication interface.

10. The remote-controlled string combiner of claim 1 wherein the first ganged switch is disposed at or proximate a service entrance for power from an electric utility to a facility.

11. The remote-controlled string combiner of claim 1 further comprising a second ganged switch in series with the first ganged switch, such that actuation of either switch is operative to interrupt all first control signals such that no photovoltaic string outputs current to the first combiner output.

12. The remote-controlled string combiner of claim 7 wherein the combiner is mounted on or near an interior side of a sun-facing roof having photovoltaic panels mounted on the exterior side thereof, and further comprising

a DC to AC inverter operative to convert DC power generated by the photovoltaic panels to AC power;

and

wherein the remote controller circuit is within or connected to the DC to AC inverter, such that, when the DC to AC inverter is off, no first control signals are asserted and hence no photovoltaic string is selected to be combined to the first combiner output terminals.

13. The remote-controlled string combiner of claim 12, wherein:

the one or more first loads receiving the first combined output current comprises a rechargeable storage battery connected to the DC to AC inverter; and

the DC to AC inverter is operative to monitor the charge state of the battery and control the first control signals to select more or fewer of the photovoltaic strings to be combined to first combined output current, based on the charge state of the battery.

14. The remote-controlled string combiner of claim 13 further comprising a Smart Load Center operative to receive both AC power from the DC to AC inverter and AC power from an electric utility grid, and wherein the Smart Load Center is operative to select, on a per-circuit breaker basis, whether a branch circuit protected by each circuit breaker receives power from the DC to AC inverter or from the utility grid, based at least in part on the first combined current output by the remote-controlled photovoltaic string combiner.

15. The remote-controlled string combiner of claim 2, further comprising

a first DC to AC inverter operative to convert DC power generated by the photovoltaic panels to AC power;

a first rechargeable battery connected to the first combiner output terminals, and operative to provide DC power to the first DC to AC inverter;

a second DC to AC inverter operative to convert DC power generated by the photovoltaic panels to AC power;

a second rechargeable battery connected to the second combiner output terminals, and operative to provide DC power to the second DC to AC inverter;

wherein the remote controller circuit is distributed between the first and second DC to AC inverters, such that the first DC to AC inverter has priority control over a first group of photovoltaic strings and secondary control over a second group comprising the remaining photovoltaic strings, and the second DC to AC inverter has priority control over the second group of photovoltaic strings and secondary control over the first group of photovoltaic strings.

16. A method of enabling the rapid de-energizing of DC wiring connecting a solar array to one or more loads, comprising:

disposing a photovoltaic string combiner proximate to the solar array;

connecting each of a plurality of strings of photovoltaic cells of the solar array to a separate pair of input terminals of the photovoltaic string combiner;

connecting a single pair of output terminals of the photovoltaic string combiner to the one or more loads;

wherein within the photovoltaic string combiner, each pair of input terminals is connected to a separate relay having a separate associated control signal, and normally-open output terminals of all of the relays are connected to the combiner output terminals, such that input currents from the photovoltaic strings for which the connected relays are energized by their associated control signals are combined at the combiner output terminals, and such that no input current from any photovoltaic string reaches the combiner output terminals unless at least one of the relays is energized by its associated control signal;

routing the plurality of control signals from a remotely disposed control circuit to the photovoltaic string combiner; and

providing at least one ganged switch in the control signal routing, allowing all control signals to be interrupted, thus forcing all relays to be de-energized, and disconnecting all photovoltaic strings from the combiner output terminals.

17. The method of claim 16, wherein routing the plurality of control signals and providing at least one ganged switch in the control signal routing comprises routing the control signals and providing ganged switches such that a switch operative to de-energize the photovoltaic string combiner output terminals is disposed at:

the photovoltaic string combiner;

one or more loads connected to the photovoltaic string combiner output terminals; and

a service entrance for power from an electric utility.