Method of monitoring a photovoltaic generator

1. A method of monitoring a photovoltaic generator for generating current with a number of solar cells connected to an inverter via two external connections the method comprising:

repeated feeding of a current with a frequency spectrum into the generator;

detecting a respective response to the supplied current in the frequency spectrum as an output variable and

detecting a change in the response for monitoring the photovoltaic generator in the event of a change during repeated feeding

wherein the current having a frequency spectrum is fed using a first converter with primary and secondary windings that are connected to a direct current circuit of the generator and that the frequency spectrum is detected using a second converter with primary and secondary windings that are mounted in series with said first converter.

2. The method as set forth in claim 1 ,

wherein the method is performed for detecting a theft or a manipulation.

3. The method as set forth in claim 2 , wherein a second method is utilized during daytime, the second method using a reference sensor and monitoring for a current interruption from the photovoltaic generator.

4. The method as set forth in claim 3 , wherein the reference sensor is configured to be a reference solar generator.

5. The method as set forth in claim 4 , characterized in that a current or voltage amplitude response of the generator is registered when the frequency response is registered as the output variable, an auxiliary variable is formed from measured current or voltage curves and a change of the auxiliary variable is monitored, and an alarm signal occurring above a threshold value of a change of the auxiliary variable.

6. The method as set forth in claim 5 , wherein the auxiliary variable is formed from the sum of the current or voltage amplitudes measured.

7. The method as set forth in claim 5 , wherein the auxiliary variable occurs from an integration of the surfaces beneath the measured curves.

8. The method as set forth in claim 1 , wherein a current with sinusoidal frequencies is fed in a direct current circuit of the generator.

9. The method as set forth in claim 1 , wherein the output variable, a change of which is measured in the frequency spectrum, is a current or an impedance of the generator.

10. The method as set forth in claim 9 , being used on a generator having several solar modules connected in parallel and/or in series.

11. A method as set forth in claim 1 , wherein the method is performed for detecting electric arcs due to contact separation or defective contacts of the photovoltaic generator.

12. A method of monitoring a photovoltaic generator for generating current with a number of solar cells connected between two external connections, characterized by repeated feeding of a current with a frequency spectrum into a generator current circuit, detecting thereby a respective frequency response in the frequency spectrum with the supplied current as an input variable and an electric variable of the generator as an output variable, and detecting a change in the frequency response for monitoring the photovoltaic generator in the event of a change during repeated feeding, a current or voltage amplitude response of the generator is registered when the frequency response is registered as an output variable, an auxiliary variable is formed from measured current or voltage curves and a change of the auxiliary variable is monitored, an alarm signal occurring above a threshold value of a change of the auxiliary variable, and the auxiliary variable is formed from a sum of the current or voltage amplitudes measured.

13. A method of monitoring a photovoltaic generator for generating current with a number of solar cells connected between two external connections, characterized by repeated feeding of a current with a frequency spectrum into a generator current circuit, detecting thereby a respective frequency response in the frequency spectrum with the supplied current as the input variable and an electric variable of the generator as the output variable, and detecting a change in the frequency response for monitoring the photovoltaic generator in the event of a change during repeated feeding, a current having a frequency spectrum being fed using a first converter with primary and secondary winding that is connected to a direct current circuit of the generator and wherein the frequency spectrum is detected using a second converter with primary and secondary winding that is mounted in series with said first converter.

14. The method as set forth in claim 13 , characterized in that a current with sinusoidal frequencies is fed in a direct current circuit of the generator.

15. The method as set forth in claim 13 , characterized in that the electric variable a change of which is measured in the frequency spectrum is a current or an impedance of the generator.