METHOD FOR DETECTING ARCS IN PHOTOVOLTAIC SYSTEMS AND SUCH A PHOTOVOLTAIC SYSTEM

• US 20120134058A1
• Filed: 06/02/2010
• Published: 05/31/2012
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: Fronius International GmbH (G&K Privatstiftung)
• Original Assignee: Fronius International GmbH (G&K Privatstiftung)
• Inventors: Oberzaucher, Friedrich, Pamer, Andreas, Ritzberger, Guenter
• Granted Patent: US 8,576,520 B2
• Time in Patent Office: Days
• US Class Current: 361/42
• CPC Class Codes: G01R 31/1227 of components, parts or materials G01R31/1209, G01R31/1218, G01R31/18 take precedence; circuits therefor G01R31/14; testing vessels of electrodes G01R31/16
• CPC Class Codes: H02H 1/0015 Using arc detectors
• 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 10/50 Photovoltaic [PV] energy

Abstract

The invention relates to a method for detecting arcs in a direct-current path of a photovoltaic system, wherein values of a current (I_DC) of the direct-current path are detected during a repeating time frame (7) and a mean value (8) is generated, and such a photovoltaic system. In order to reliably detect arcs by means of a component of the photovoltaic system, values of a voltage (U_DC), of the direct-current path are detected during the time frame (7) and a mean value (8, 8′) is generated, and at least one detection signal (9) and at least one detection threshold (10) are continuously calculated based on the mean values (8, 8′) for the current (I_DC) and the voltage (U_DC) by means of a calculation method.

Claims

1. Method for detecting arcs in a direct-current path of a photovoltaic system, wherein values of a current (I_DC) of the direct-current path are detected during a repeating time frame (7) and a mean value (8) is generated, wherein during the time frame (7), values of a voltage (U_DC) of the direct-current path are detected and a mean value (8′

) is generated, and that based on the mean values (8, 8′

) of the current (I_DC) and the voltage (U_DC), at least one detection signal (9) and at least one detection threshold (10) are continuously calculated by means of a calculation method.

2. The method according to claim 1, wherein in order to calculate the at least one detection signal (9) from the respective mean values (8, 8′

), difference mean values are calculated.

3. The method according to claim 1, wherein in order to calculate the at least one detection signal (9) and the at least one detection threshold (10) from the respective mean values (8, 8′

), long-term mean values (11, 11′

) are calculated by digital low-pass filtering.

4. The method according to claim 2, wherein in order to calculate the at least one detection signal (9) from the respective difference mean values, long-term difference mean values are calculated by digital low-pass filtering.

5. The method according to claim 2, wherein after each time frame (7), the detection signal (9) and the detection threshold (10) are calculated by means of a difference mean value, a long-term mean value (11, 11′

) and a long-term difference mean value of each of the current (I_DC) and the voltage (U_DC).

6. The method according to claim 2, wherein a value is generated from the long-term difference mean value and the difference mean value of the voltage (U_DC) and multiplied by a value generated from the long-term difference mean value and the difference mean value of the current (I_DC) to generate the detection signal (9).

7. The method according to claim 6, wherein the values of the detection signal (9) are multiplied by a correction factor greater than 1.

8. The method according to claim 2, wherein the long-term mean values (11, 11′

) of the current (I_DC) and the voltage (U_DC) are multiplied to generate the detection threshold (10).

9. The method according to claim 8, wherein the detection threshold (10) is multiplied by a correction factor less than 1 for detecting a series arc.

10. The method according to claim 8, wherein the detection threshold (10) is multiplied by a correction factor less than 1 for detecting a parallel arc.

11. The method according to claim 1, wherein an arc is detected when the detection threshold (10) is exceeded by the detection signal (9), and a distinction is made between a series arc and a parallel arc.

12. The method according to claim 1, wherein after detection of an arc, said arc is extinguished.

13. The method according to claim 12, wherein to extinguish the parallel arc the direct-current path is short-circuited with a switch, and to extinguish the series arc the current flow in the direct-current path is interrupted.

14. The method according to claim 1, wherein the functioning of the detection method is checked with a test run.

15. The method according to claim 1, wherein the detection method is activated after a starting process of the photovoltaic system.

16. Photovoltaic system having components for feeding power into an AC voltage grid (3), having a DC-DC-converter (4) and a DC-AC-converter (5) for converting the DC voltage (U_DC) with associated direct current (I_DC) generated by at least one solar cell (2) into an AC voltage (U_AC) for feeding into the AC voltage grid (3), and a control device (6), wherein a measurement device for measuring the DC voltage (U_DC) and the direct current (I_DC) is provided, and that the control device (6) is designed for carrying out the method for detecting arcs in a direct-current path of the photovoltaic system according to claim 1.