Solar Photovoltaic Module Safety Shutdown System

• US 20110088741A1
• Filed: 06/10/2010
• Published: 04/21/2011
• Est. Priority Date: 10/19/2009
• Status: Active Grant

• Current Assignee: Helios Focus, LLC
• Original Assignee: Helios Focus, LLC
• Inventors: Dunton, Randy Richard, Sutton, Geoffrey Nicholas Barnard
• Granted Patent: US 8,859,884 B2
• Time in Patent Office: Days
• US Class Current: 136/244
• CPC Class Codes: H02S 50/00 Monitoring or testing of PV systems, e.g. load balancing or fault identification
• CPC Class Codes: H03K 17/687 the devices being field-effect transistors
• CPC Class Codes: H03K 17/691 using transformer coupling
• CPC Class Codes: H03K 17/7955 using phototransistors
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A PV system may be used in case of emergencies. Each individual photovoltaic module receives a signal to determine if it is allowed to be operational or must shut down. Modules by default are shut off and safe to handle, absent the signal and in the presence of light.

Claims

1. A photovoltaic system comprising:

at least a first and second connected photovoltaic module;

a system-monitor to detect power and, in response, to generate a system-on signal to said first and second photovoltaic modules indicative of the presence of power;

a switch in each module to disable each individual module, said switch activated by loss of said signal; and

a connector in each module, coupled to a switch in the module, to connect a DC signal produced by one photovoltaic module to the other photovoltaic module.

2. The system of claim 1 including a manually controlled and lockable switch with visual feedback to enable or disable the modules.

3. The system of claim 1 including a sensor to disable each module.

4. The system of claim 3 wherein said sensor is selected from the group including motion, moisture, or heat sensors.

5. The system of claim 1, said switch including a current limiting resistor that provides power to an opto-isolated FET driver integrated circuit, which provides a gate voltage to the FET.

6. The system of claim 5 wherein the inherent capacitance of the FET'"'"'s gate stores enough charge to remain at a high enough voltage to allow the FET to remain on during the entire AC cycle.

7. The system of claim 5 including a resistor to protect the FET during the transition from conducting (on) to open (off) and to drain the charge in time to avoid overheating due to power dissipation.

8. The system of claim 1 wherein if said system-on signal is inactive said modules are turned off.

9. The system of claim 1 including an isolation device.

10. The system of claim 9 wherein said isolation device is a transformer or an optical isolator.

11. The system of claim 1 wherein said switch includes a photovoltaic driver to generate light for half an AC cycle and convert the light to a DC voltage applied to switch to enable said modules.

12. The system of claim 1 wherein said switch includes a MOSFET whose inherent gate capacitance is high enough to avoid the need for a gate charge storage device and a resistor coupled to said MOSFET.

13. A solar module junction box for a photovoltaic system including a plurality of connected photovoltaic modules, said box comprising:

a first connector to connect a system-on signal to said photovoltaic module;

a switch to disable said module, said switch controlled by said signal;

a logic element coupled to switch; and

a second connector, coupled to said switch, to connect a DC signal produced by said module to another module.

14. The box of claim 13, said switch including a current limiting resistor that provides power to an opto-isolated FET driver integrated circuit, which provides a gate voltage to the FET.

15. The box of claim 14 wherein the inherent capacitance of the FET'"'"'s gate stores enough charge to remain at a high enough voltage to allow the FET to remain on during the entire AC cycle.

16. The box of claim 15 including a resistor to protect the FET during the transition from conducting (on) to open (off) and to drain the charge in time to avoid overheating due to power dissipation.

17. A solar module switch assembly for a photovoltaic system comprising:

a field effect transistor connectable to said system to control power generated by one of a plurality of individual modules in said system;

an opto-isolated FET driver integrated circuit to provide a gate voltage to said transistor;

a current limiting resistor coupled across said FET driver to provide power to said driver; and

a connector to connect a system-on signal, said switch assembly to turn off said module when said system-on signal is lost.

18. The switch assembly of claim 17 wherein said system-monitor detects the presence of power.

19. The switch assembly of claim 17 wherein the inherent capacitance of the transistor'"'"'s gate stores enough charge to remain at a high enough voltage to allow the transistor to remain on during an AC power cycle.

20. The switch assembly of claim 19 including a second resistor to protect the transistor during the transition from conducting to open and to drain charge in time to avoid overheating due to power dissipation.

21. The switch assembly of claim 17 wherein when AC power is lost, said switch to receive a signal to turn off the module.