Method and apparatus for localizing and quenching an arc

Patent metadata

Field	Value
Publication number	US-9478675-B2
Application number	US-201414540214-A
Country	US
Kind code	B2
Filing date	Nov 13, 2014
Priority date	May 18, 2012
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

The disclosure relates to a method for localizing and quenching an arc in a PV generator of a PV system, wherein the PV generator includes at least two PV subgenerators. An arc quenching circuit is associated with each PV subgenerator. The method includes detecting an arc in the PV generator. Then, a probability value is determined for each of the PV subgenerators, wherein the probability value is correlated with a probability that the arc is located in the corresponding PV subgenerator. A sequence for activating the arc quenching circuits is then determined that is dependent on the determined probability values. Then, the arc quenching circuits are activated successively in the order of the determined sequence.

First claim

The invention claimed is:

1. A method for localizing and quenching an arc in a photovoltaic (PV) generator of a PV system, wherein the PV generator comprises at least two PV subgenerators, and wherein an arc quenching circuit is associated with each PV subgenerator, said method comprising:
detecting an arc in the PV generator;
determining a probability value for each of the PV subgenerators which is correlated with a probability that the arc is located in the corresponding PV subgenerator;
determining a sequence for activating the arc quenching circuits associated with the PV subgenerators based on the determined probability values; and
successively activating the arc quenching circuits in the order of the determined sequence.

2. The method as claimed in claim 1 , wherein the probability values are determined based on noise levels of AC voltage signals in the PV subgenerators.

3. The method as claimed in claim 2 , wherein the arc quenching circuits are activated in the sequence of decreasing noise levels.

4. The method as claimed in claim 1 , wherein the probability values are determined from changes in measured partial currents flowing through the PV subgenerators.

5. The method as claimed in claim 4 , wherein measured values for the partial currents are stored continuously, and wherein the probability values are determined based on the measured values for the partial currents which have been measured during the occurrence of the arc.

6. The method as claimed in claim 1 , wherein the probability values are determined based on noise levels of AC voltage signals in the PV subgenerators, and based on changes in measured values of partial currents flowing through the PV subgenerators.

7. The method as claimed in claim 6 , further comprising:
performing a check to ascertain whether the change in the partial currents correlates temporally with a change in the noise levels; and
implementing a plausibility check with respect to the probability of an arc in the PV subgenerator depending on the check.

8. The method as claimed in claim 1 , further comprising:
interrupting a partial current through the corresponding PV subgenerator upon activating the corresponding arc quenching circuit.

9. The method as claimed in claim 1 , further comprising short-circuiting the corresponding PV subgenerator upon activating the corresponding arc quenching circuit.

10. The method as claimed in claim 8 , wherein, in order to interrupt the partial current through the corresponding PV subgenerator, in each case one switching element, each comprising an electromechanical switch and a semiconductor switch arranged in parallel therewith, is provided, and wherein the interruption of the partial current through the corresponding PV subgenerator comprises switching of the respective semiconductor switch of the switching element after all of the electromechanical switches of the switching elements have been opened.

11. The method as claimed in claim 1 , further comprising signalling an arc as having been localized in a PV subgenerator if, after activation of the arc quenching circuit which is associated with this PV subgenerator, an arc is no longer detected in the PV generator.

12. An apparatus for localizing and quenching an arc in a photovoltaic (PV) generator of a PV system, wherein the PV generator comprises at least two PV subgenerators, comprising:
an arc quenching circuit associated with each PV subgenerator;
an arc detection device associated with each PV subgenerator; and
a control device per PV subgenerator or a central control device for the entire PV system, wherein each control device or the central control device is configured:
to determine a probability value for each of the PV subgenerators, wherein the probability value is correlated with a probability that an arc is located in the corresponding PV subgenerator;
to determine a sequence for activating the arc quenching circuits depending on the determined probability values; and
to successively activate the arc quenching circuits in the order of the determined sequence.

13. An apparatus for quenching an arc in a photovoltaic (PV) system, comprising:
a plurality of monitoring circuits, each respectively associated with a PV subgenerator of the PV system, wherein each of the monitoring circuits is configured to provide an indication signal that is indicative of a presence of an arc in the respective PV subgenerator; and
a control circuit configured to receive the indication signal from each of the plurality of monitoring circuits, and further configured to generate a plurality of control signals to the plurality of monitoring circuits in response thereto, wherein the plurality of control signals dictate a sequence for activating arc quenching circuits associated with the monitoring circuits of the respective PV subgenerators, and wherein the sequence is based on a determined probability value for each PV subgenerator that correlates with a probability that an arc is located in the corresponding PV subgenerator.

14. The apparatus of claim 13 , wherein each of the plurality of monitoring units comprises a current measurement device configured to detect an AC component of a partial current associated with its respective PV subgenerator, wherein the AC component comprises a characteristic indicative of a presence of an arc.

15. The apparatus of claim 14 , wherein the AC component of a partial current is converted by the monitoring unit to an AC voltage component that comprises a noise level associated with the respective PV subgenerator.

16. The apparatus of claim 14 , wherein the control circuit is configured to receive the AC component of a partial current or a signal associated therewith as the indication signal, compare the indication signal to a threshold, and draw a conclusion regarding presence of an arc based on a result of the comparison.

17. The apparatus of claim 14 , wherein the control circuit is configured to receive the AC component of a partial current or a signal associated therewith as values of each monitoring unit and sort the values in terms of their magnitude to form a sorted sequence, and wherein the sorted sequence is employed to generate the activating sequence by the control circuit.

18. The apparatus of claim 14 , wherein the current measurement device of each of the plurality of monitoring units is further configured to detect changes in partial currents flowing through the respective PV subgenerators, and wherein probability values associated with an occurrence of an arc are associated with the detected changes in partial currents and the AC component of the partial currents.

19. The apparatus of claim 13 , wherein each of the plurality of monitoring units comprises a current measurement device configured to detect changes in partial currents flowing through the respective PV subgenerators, and wherein probability values associated with an occurrence of an arc are associated with the detected changes in partial currents.

Assignees

• Sma Solar Technology Ag

Inventors

• Behrends Holger
• Kratochvil Marcel
• Hopf Markus

Classifications

• G01R31/1227

  of components, parts or materials (G01R31/1209, G01R31/1218, G01R31/18 take precedence; circuits therefor G01R31/14; testing vessels of electrodes G01R31/16) · CPC title

• H02H7/20

  for electronic equipment (for converters H02H7/10; for electric measuring instruments G01R1/36; for DC voltage or current semiconductor regulators G05F1/569; for amplifiers H03F1/52; for electronic switching circuits H03K17/08) · CPC title

• H02J3/381

  Dispersed generators · CPC title

• H02H7/261

  involving signal transmission between at least two stations (transmission of signals in general H02H1/0061) · CPC title

• H02J2101/24

  Photovoltaics · CPC title