Abstract: The disclosure relates to a safety device for a photovoltaic system for feeding into a power supply system, that includes at least one input for connection to a PV generator, at least one output for connection to an inverter, and a switching element for de-energizing the at least one output. The safety device includes an evaluating unit configured to switch the switching element based on a low-frequency signal at the at least one output. The disclosure also relates to a method for operating such a safety device.

Abstract: A method for leakage current compensation in a photovoltaic system includes determining a reference current flowing from at least one current-carrying line under voltage via a capacitor to earth, and generating a compensation current, having a phase and a frequency of the reference current, and having an amplitude adjusted by a negative scaling factor based on the reference current. The method further includes determining a current sum using a differential current sensor for at least a portion thereof, wherein the addends of the current sum are the currents through a complete set of current-carrying lines and the compensation current, minimizing the determined current sum by adjusting the scaling factor, and routing the compensation current through at least one other differential current sensor, such that the compensation current compensates a leakage current component of a differential current monitored by the other differential current sensor. A related device and system is also disclosed.

Abstract: The apparatus for monitoring a photovoltaic system includes an incoupling circuit configured to couple an AC voltage test signal into the photovoltaic system, and an outcoupling circuit configured to outcouple a response signal, which is associated with the test signal, from the photovoltaic system, and an evaluation device, which is connected to the outcoupling circuit. The evaluation device is configured to identify events which adversely affect correct operation of the photovoltaic system. The apparatus is distinguished in that the outcoupling circuit includes a first transformer and a second transformer, each having a respective primary winding and each having a respective secondary winding which is connected to the evaluation device, with the primary windings of the first and second transformers being arranged in different electrical lines between a generator and an inverter in the photovoltaic system. The disclosure also relates to a corresponding method for monitoring a photovoltaic system.

Abstract: A device and corresponding method for monitoring a photovoltaic system to detect an occurrence of events impairing normal operation of the photovoltaic system is provide. The photovoltaic system includes a photovoltaic generator including a first group of photovoltaic modules and a second group of photovoltaic modules being different from the first group. The device includes a first and a second pair of coupling means, both pairs including signal coupling-in means for coupling a test signal into the photovoltaic generator, and a signal coupling-out means for coupling out a response signal from the photovoltaic generator, the first pair of coupling means configured to selectively detect the occurrence of the events in the first group of photovoltaic modules, and the second pair of coupling means configured to selectively detect the occurrence of the events in the second group of photovoltaic modules.

Abstract: The disclosure relates to a method for signaling partial shadowing within a PV generator including at least two partial PV generators connected in parallel. The method includes performing a reference impedance measurement on each of the at least two partial PV generators in a state of uniform irradiation of the PV generator, and determining at least one reference resonant property of each of the at least two partial PV generators from the reference impedance measurement. Furthermore, impedance measurements are carried out on the at least two partial PV generators at a first operating point of the PV generator during operation of the PV generator. Resonant properties of the partial PV generators are determined from the impedance measurements. Partial shadowing within the PV generator is detected and signaled if a difference between the resonant properties of the partial PV generators at the first operating point differs from a difference between the reference resonant properties of the partial PV generators.

Abstract: A method of detecting an arc fault in a power circuit includes injecting an AC-signal into the power circuit and measuring a response signal that is related to the injected AC-signal in the power circuit. The method further includes determining a frequency response of the power circuit from the response signal, analyzing the frequency response, and identifying a preferred frequency. A signal related to AC-current flowing in the power circuit within the preferred frequency range is measured and an occurrence of an arc fault in the power circuit is signaled depending on the measured signal. A system for detecting an arc fault is designed to perform a method as described before.

Abstract: For the purpose of determining a fault current component of a differential current which is measured as a current sum over a plurality of lines carrying a current of an AC current generator, an electric signal which depends on generator voltages present at the AC current generator with respect to earth potential and which is in phase with a leakage current component of the differential current is generated. The electric signal is scaled by multiplying it by a scaling factor; and the scaled electric signal is subtracted from the differential current to obtain a remainder. The scaling factor is repeatedly updated such that the effective value of the remainder reaches a minimum at the present value of the scaling factor.

Abstract: A method for leakage current compensation in a photovoltaic system includes determining a reference current flowing from at least one current-carrying line under voltage via a capacitor to earth, and generating a compensation current, having a phase and a frequency of the reference current, and having an amplitude adjusted by a negative scaling factor based on the reference current. The method further includes determining a current sum using a differential current sensor for at least a portion thereof, wherein the addends of the current sum are the currents through a complete set of current-carrying lines and the compensation current, minimizing the determined current sum by adjusting the scaling factor, and routing the compensation current through at least one other differential current sensor, such that the compensation current compensates a leakage current component of a differential current monitored by the other differential current sensor. A related device and system is also disclosed.

Abstract: A method for detecting an arc fault in a photovoltaic power circuit includes operating a photovoltaic generator at a first working point. A first signal related to a DC-current and/or a DC-voltage in the power circuit is determined. The first signal is analyzed and it is determined whether the signal indicates the presence of an electric arc in the power circuit. If so, the photovoltaic generator is operated at a second working point and a second signal related to the DC-current and/or the DC-voltage is determined. The first and second signals are then compared; and the occurrence of an arc fault in the power circuit is selectively signaled based on the comparison.

Abstract: The disclosure relates to a method for signaling partial shadowing within a PV generator including at least two partial PV generators connected in parallel. The method includes performing a reference impedance measurement on each of the at least two partial PV generators in a state of uniform irradiation of the PV generator, and determining at least one reference resonant property of each of the at least two partial PV generators from the reference impedance measurement. Furthermore, impedance measurements are carried out on the at least two partial PV generators at a first operating point of the PV generator during operation of the PV generator. Resonant properties of the partial PV generators are determined from the impedance measurements. Partial shadowing within the PV generator is detected and signaled if a difference between the resonant properties of the partial PV generators at the first operating point differs from a difference between the reference resonant properties of the partial PV generators.

Abstract: The disclosure relates to a safety device for a photovoltaic system for feeding into a power supply system, that includes at least one input for connection to a PV generator, at least one output for connection to an inverter, and a switching element for de-energizing the at least one output. The safety device includes an evaluating unit configured to switch the switching element based on a low-frequency signal at the at least one output. The disclosure also relates to a method for operating such a safety device.

Abstract: A method for detecting an arc fault in a photovoltaic power circuit includes operating a photovoltaic generator at a first working point. A first signal related to a DC-current and/or a DC-voltage in the power circuit is determined. The first signal is analyzed and it is determined whether the signal indicates the presence of an electric arc in the power circuit. If so, the photovoltaic generator is operated at a second working point and a second signal related to the DC-current and/or the DC-voltage is determined. The first and second signals are then compared; and the occurrence of an arc fault in the power circuit is selectively signaled based on the comparison.

Abstract: A method of detecting an arc fault in a power circuit includes injecting an AC-signal into the power circuit and measuring a response signal that is related to the injected AC-signal in the power circuit. The method further includes determining a frequency response of the power circuit from the response signal, analyzing the frequency response, and identifying a preferred frequency. A signal related to AC-current flowing in the power circuit within the preferred frequency range is measured and an occurrence of an arc fault in the power circuit is signaled depending on the measured signal. A system for detecting an arc fault is designed to perform a method as described before.

Abstract: For the purpose of determining a stray capacitance of an AC current generator a differential current is measured as a current sum over a plurality of lines carrying a current of the AC current generator, an electric signal which depends on generator voltages present at the AC current generator with respect to earth potential and which is in phase with a leakage current component of the differential current is generated. The electric signal is scaled by multiplying it by a scaling factor; and the scaled electric signal is subtracted from the differential current to obtain a remainder. The scaling factor is repeatedly updated such that the effective value of the remainder reaches a minimum at the present value of the scaling factor.