Safety switch for photovoltaic systems
Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.
1. A system comprising:
a power generation installation comprising:
a plurality of power sources comprising a first power source and a second power source connected to each other at a first node, and
at least one switching element connected, in parallel with the first power source, between the first node and a second node, wherein the second power source is serially connected, at the first node, to the parallel connected at least one switching element and first power source, and wherein the parallel connected at least one switching element and first power source are connected, at the second node, to a power converter; and
a controller configured to:
detect a sensor measurement indicative of a potentially unsafe condition at the power generation installation;
control the at least one switching element to create a short circuit across the first power source but not across the second power source;
receive a sensor measurement indicating that the potentially unsafe condition is no longer present; and
control the at least one switching element to eliminate the short circuit across the first power source.
2. The system according to claim 1 , wherein the first power source and the second power source are connected to the power converter.
3. The system according to claim 1 , further comprising an electrical T-connector disposed at the first node.
4. The system according to claim 1 , wherein at least one of the first power source or the second power source comprises a photovoltaic generator.
5. The system according to claim 1 , wherein the at least one switching element comprises at least one of a transistor or a relay.
6. The system according to claim 1 , further comprising a communication device coupled to the controller, wherein the communication device is configured to receive a message indicative of the potentially unsafe condition and to provide an indication of the potentially unsafe condition to the controller, and wherein the communication device comprises at least one of a power line communication device or a wireless communication device.
7. The system according to claim 1 , further comprising a sensor coupled to the controller, wherein the sensor is configured to measure one or more electrical parameters and to provide one or more measurements of the one or more electrical parameters to the controller, and wherein the one or more measurements include the sensor measurement indicative of the potentially unsafe condition.
8. The system according to claim 7 , wherein the sensor comprises a current sensor, and wherein the sensor measurement indicative of the potentially unsafe condition includes at least one of: a high current measurement, a measurement indicating a change in current flow or a measurement indicating a mismatch with another electrical parameter.
9. A method comprising:
detecting, by a controller, a sensor measurement indicative of a potentially unsafe condition at a power generation installation comprising a first power source, a second power source connected to the first power source at a first node, and at least one switching element connected, in parallel with the first power source, between the first node and a second node, wherein the second power source is serially connected, at the first node, to the parallel connected at least one switching element and first power source, and wherein the parallel connected at least one switching element and first power source are connected, at the second node, to a power converter;
controlling, by the controller, the at least one switching element to create a short circuit across the first power source but not across the second power source;
receiving, by the controller, a sensor measurement indicating that the potentially unsafe condition is no longer present; and
controlling, by the controller, the at least one switching element to eliminate the short circuit across the first power source.
10. The method according to claim 9 , wherein the first power source and the second power source are connected to an electrical T-connector disposed at the first node.
11. The method according to claim 9 , further comprising:
receiving, by a communication device, a message indicative of the potentially unsafe condition and providing an indication of the potentially unsafe condition to the controller,
wherein the communication device comprises at least one of a power line communication device or a wireless communication device.
12. The method according to claim 9 , further comprising measuring, by a sensor, one or more electrical parameters and providing one or more measurements of the one or more electrical parameters to the controller, wherein the one or more measurements include the sensor measurement indicative of the potentially unsafe condition.
13. The method according to claim 12 , wherein the sensor comprises a current sensor, and wherein the sensor measurement indicative of the potentially unsafe condition includes at least one of: a high current measurement, a measurement indicating a change in current flow, or a measurement indicating a mismatch with another electrical parameter.
14. The method according to claim 9 , further comprising drawing, by an auxiliary power circuit coupled to at least one of the first power source or the second power source, power from the at least one of the first power source or the second power source, and providing the drawn power to the controller.
15. A system comprising:
a first power source having at least a first terminal and a second terminal;
a second power source having at least a first terminal and a second terminal, the second terminal of the second power source connected to the first terminal of the first power source; and
a power device comprising:
a first input terminal connected to the second terminal of the first power source;
a second input terminal connected to the first terminal of the first power source and the second terminal of the second power source;
a third input terminal connected to the first terminal of the second power source;
a power converter connected between the first and third input terminals;
a switch disposed between the first and second input terminals; and
a controller configured to control the switch to be OFF during normal operating conditions and to be ON in response to an unsafe condition.
16. The system according to claim 15 , wherein the second input terminal, the first terminal of the first power source and the second terminal of the second power source are connected using a T-connector.
17. The system according to claim 15 , wherein the first power source and the second power source are connected to one another at an electrical T-connector disposed at a midpoint.
18. The system according to claim 15 , wherein at least one of the first power source or the second power source comprises a photovoltaic generator.
19. The system according to claim 15 , further comprising a communication device coupled to the controller, wherein the communication device is configured to receive a message indicative of the unsafe condition and to provide an indication of the unsafe condition to the controller, and wherein the communication device comprises at least one of a power line communication device or a wireless communication device.
20. The system according to claim 15 , further comprising a sensor coupled to the controller, wherein the sensor is configured to measure one or more electrical parameters and to provide one or more measurements of the one or more electrical parameters to the controller, wherein the one or more measurements include a sensor measurement indicative of the unsafe condition.
21. The system according to claim 20 , wherein the sensor comprises a current sensor, and wherein the sensor measurement indicative of the unsafe condition includes at least one of: a high current measurement, a measurement indicating a change in current flow, or a measurement indicating a mismatch with another electrical parameter.