System and method for protection during inverter shutdown in distributed power installations
A protection method in a distributed power system including of DC power sources and multiple power modules which include inputs coupled to the DC power sources. The power modules include outputs coupled in series with one or more other power modules to form a serial string. An inverter is coupled to the serial string. The inverter converts power input from the string and produces output power. When the inverter stops production of the output power, each of the power modules is shut down and thereby the power input to the inverter is ceased.
1. A protection device for a photovoltaic system for feeding into a power supply system, the device comprising:
at least one input for connection to a solar panel;
at least one output configured to be connected to an inverter;
a switching element for de-energizing the at least one output based on a signal; and
a monitoring and detection mechanism configured to control the switching element based on the signal comprising a frequency which corresponds to a system frequency in the power supply system.
2. The protection device as claimed in claim 1 , wherein the monitoring and detection mechanism detects signals having a predetermined frequency.
3. The protection device as claimed in claim 1 , wherein power from the solar panel is removed via a short circuit of the inputs to the device.
4. The protection device as claimed in claim 1 , wherein power from the solar panel is removed via a separating of the connection of the at least one input and the at least one output.
5. The protection device of claim 1 , wherein the signal is at a higher frequency up-converted from the power supply system.
6. The protection device of claim 1 , wherein the monitoring and detection mechanism monitors a voltage and frequency of the power supply system.
7. The protection device as claimed in claim 1 , wherein the signal is a current signal.
8. The protection device of claim 1 , wherein the at least one output is configured to provide a communication path with the inverter.
9. A method for operating a photovoltaic system for feeding into a power supply system, the photovoltaic system comprising at least one input for connection to a solar panel and at least one output configured to be in communication with an inverter, comprising:
determining a level of a low-frequency signal at the at least one output, wherein the signal comprises a frequency which corresponds to system frequency in the power supply system;
connecting the at least one output to the at least one input, if the level of the low-frequency signal is detected; and
de-energizing the at least one output if the low-frequency signal is not detected.
10. The method as claimed in claim 9 , wherein the low-frequency signal comprises a frequency which corresponds to two times the system frequency in the power supply system.
11. The method of claim 9 , wherein de-energizing the at least one output comprises creating a short circuit of the at least one input.
12. The method of claim 9 , wherein de-energizing the at least one output comprises separating of the connection of the at least one input and the at least one output.
13. The method of claim 9 , wherein the low-frequency signal is at a higher frequency up-converted from the power supply system.
14. A protection device for a photovoltaic system for feeding into a power supply system, the device comprising:
at least one input for connection to a solar panel;
at least one output;
a switching element for de-energizing the at least one output based on a signal; and
a monitoring and detection mechanism configured to control the switching element based on the signal comprising a frequency which corresponds to a system frequency in the power supply system.
15. The protection device as claimed in claim 14 , wherein the monitoring and detection mechanism detects signals having a predetermined frequency.
16. The protection device as claimed in claim 14 , wherein power from the solar panel is removed via a short circuit of the inputs to the device.
17. The protection device as claimed in claim 14 , wherein power from the solar panel is removed via a separating of the connection of the at least one input and the at least one output.
18. A method for operating a photovoltaic system for feeding into a power supply system, the photovoltaic system comprising at least one input for connection to a solar panel and at least one output, comprising:
determining a level of a low-frequency signal at the at least one output, wherein the signal comprises a frequency which corresponds to system frequency in the power supply system;
connecting the at least one output to the at least one input, if the level of the low-frequency signal is detected; and
de-energizing the at least one output if the low-frequency signal is not detected.
19. The method as claimed in claim 18 , wherein the low-frequency signal comprises a frequency which corresponds to two times the system frequency in the power supply system.
20. The method of claim 18 , wherein de-energizing the at least one output comprises creating a short circuit of the at least one input.
21. The method of claim 18 , wherein de-energizing the at least one output comprises separating of the connection of the at least one input and the at least one output.
22. The method of claim 18 , wherein the low-frequency signal is at a higher frequency up-converted from the power supply system.