WO2018073090A1

WO2018073090A1 - Device in a direct current circuit for detection and communication purposes

Info

Publication number: WO2018073090A1
Application number: PCT/EP2017/076018
Authority: WO
Inventors: Christopher Merz; Markus Hopf
Original assignee: Sma Solar Technology Ag
Priority date: 2016-10-19
Filing date: 2017-10-12
Publication date: 2018-04-26
Also published as: DE102016119877A1

Abstract

The invention relates to a device (1) for detecting AC signals from a direct current circuit and for communication purposes, having the following: • - a first and a second connection, • - a transmitter (7) with a primary coil and a secondary coil, wherein the first connection is connected to the second connection via a series circuit consisting of a capacitor (6) and the secondary coil, • - a blocking element (5) which is connected parallel to the series circuit, • - a communication unit (8) which generates an AC communication signal and couples same into the direct-current circuit via the transmitter, • - a detection unit (9) which receives and processes an AC signal coupled out of the direct-current circuit via the transmitter, wherein • - the communication unit and the detection unit are connected together to the primary side of the transmitter, and • - a controller (10) which sets the communication unit and the detection unit to a respective activated and deactivated state, wherein • - the communication signal is coupled into the direct current circuit only in the activated state, • - the AC signal is received/processed only in the activated state, and • - the controller controls the states of the units such that maximally one unit is in the activated state at each point in time. The invention further relates to a photovoltaic system comprising a device according to the invention.

Description

DEVICE IN A DC CIRCUIT FOR DETECTION AND

COMMUNICATION

TECHNICAL FIELD OF THE INVENTION

The invention relates to a device for detecting AC signals from a DC circuit of a circuit unit and for communication by means of coupled for the purpose of communication in the DC circuit of the circuit unit AC signals. The invention further relates to a photovoltaic (PV) system as a circuit unit with a DC circuit having a device according to the invention.

Conventional measuring devices often offer the possibility, in addition to detecting or measuring a physical quantity, to communicate the measurement results and / or a signal resulting from the measurement results to a higher-level control unit. Therefore, such measuring devices in addition to a detection unit, which operatively takes over the detection and evaluation of the size to be measured, in addition to a communication unit which is connected for the purpose of data exchange with the parent control unit and communicates with these measurement results, signals but also control instructions. In particular, the detection unit of the device according to the invention is designed to receive and process an AC signal coupled out of the DC circuit of the circuit unit. Such a detection unit can be formed, for example, by an arc detection unit which monitors the DC circuit of the circuit unit connected to the device for the eventual occurrence of an electric arc. Here, the property is exploited that an arc generates a high-frequency AC signal - the so-called arc noise - in the arc affected by the electric circuit. Likewise, the communication unit is adapted to couple an AC signal for the purpose of communication as a communication signal in the DC circuit of the circuit unit. Such a communication unit can be designed, for example, to carry out a so-called power-line communication (PLC), wherein an information to be communicated via a suitable modulation method - eg a frequency and / or amplitude modulation - the injected AC signal is impressed. A communication unit designed for the PLC STATE OF THE ART

DE 10 2013 108 166 A1 discloses a device for detecting AC components of an electric current flowing in a DC circuit. The device comprises an inductance arranged in the DC circuit, an AC path arranged electrically parallel to the inductance, which comprises a series connection of a capacitance and a primary-side winding of a transformer, and a voltage measuring device. A secondary-side winding of the transformer is connected via a low-pass circuit with the voltage measuring device. The device can be used for the detection of arcs and / or communication signals in a photovoltaic system.

From DE 10 2012 104 004 B3 a method is known to detect a type of present in a PV system with a PV generator arc. In the method, an impedance measurement is performed on the PV generator at at least one measurement frequency. Depending on the measured impedance, it is evaluated whether the present arc is a series arc or a parallel arc.

From DE 10 2012 1 12 921 A1 a circuit arrangement for coupling a high-frequency (HF) signal for data transmission on DC lines of a photovoltaic system is known. The circuit arrangement comprises a signal generator for generating an RF signal, a coupling transformer having a primary winding and a secondary winding, and a looped into the DC circuit blocking member, such as an inductor. The signal generator is connected to the primary winding, a series circuit of the secondary winding and a capacitor is connected in parallel with the blocking member.

If both the device for detecting electric arcs and the circuit arrangement for coupling high-frequency signals are operated together in a DC circuit of a photovoltaic system, then the coupled-in RF signals can interfere with the arc detection. This is the case in particular when a frequency of the RF signal for data transmission is at least approximately one frequency 16-190-P-WO - 3_- submitted version of the AC component to be detected for arc detection corresponds. Furthermore, a simultaneous provision of both the device and the circuit arrangement requires a large space and is also associated with relatively high costs.

DE 10 2014 220 421 A1 discloses a measuring node for detecting partial discharges in a subarea of a power supply network to which a mains voltage is applied. The measuring node can be coupled to the power supply network via a coupling circuit and designed for decoupling and analyzing an interference signal from the power supply network. The measuring node may further comprise a communication device, for example a BPL modem.

From DE 10 2014 221 108 A1 a coupling device for coupling a powerline terminal and a measuring device to a multi-phase power supply network is disclosed. In this case, the coupling device comprises a coupling capacitor and a first and a second coupling circuit. The coupling capacitor is connected to a first connection to one of the phases of the power supply network and to a second connection to the first and the second coupling circuit.

OBJECT OF THE INVENTION

The invention has for its object to provide a device for detection and communication according to the preamble of independent claim 1, which is designed on the one hand to decouple and process an AC signal from a DC circuit of a circuit unit connected to the device, and on the other hand is designed to generate an AC signal as a communication signal and to couple it into the DC circuit of the circuit unit. In this case, a disturbing influence between the detection and the communication unit should be excluded as far as possible, or at least significantly reduced. In addition, the device should have a compact design as possible and be as inexpensive as possible. The invention is further based on the object to show a photovoltaic (PV) system with such a device. 16-190-P-WO - 4 - filed

SOLUTION

The object of the invention is achieved by a device having the features of independent claim 1. The dependent claims 2 to 13 are directed to preferred embodiments of the device. The independent claim 14 relates to a photovoltaic (PV) system as a circuit unit with a DC circuit and a device connected to the DC circuit according to the invention.

DESCRIPTION OF THE INVENTION

An inventive device for detecting AC signals from a DC circuit of a circuit unit and for communication includes:

a first and a second terminal for connection to the DC circuit of the circuit unit,

a transformer having a primary winding arranged on a primary side of the transformer and a secondary winding arranged on a secondary side of the transformer, the first connection being connected to the second connection via a series connection of a capacitor and the secondary winding of the transformer,

a blocking element which is connected in parallel to the series circuit of capacitor and secondary winding,

a communication unit which is designed to generate an AC signal as a communication signal and to couple it via the transformer into the DC circuit of the circuit unit,

a detection unit which is designed to receive and process an AC signal coupled out of the DC circuit via the transformer;

wherein the communication unit and the detection unit are connected in common to the primary side of the transformer.

The apparatus further comprises a controller for controlling the communication unit and the detection unit, and is characterized

in that the controller is designed to set the communication unit and the detection unit respectively in an activated and a deactivated state,

wherein a coupling of the communication signal by the communication unit takes place only in the activated state of the communication unit, and

wherein a reception and / or processing of the AC signal by the detection unit takes place only in the activated state of the detection unit. It is the 16-190-P-WO - 5 - filed

Control is designed to control the states of the communication unit and the detection unit such that at any time at most one unit of communication unit and detection unit is in the activated state.

By the detection unit and the communication unit are connected in common to the primary side of the same transformer, the decoupling of the AC signal to be detected, as well as the coupling of the AC signal to be communicated via the same transmitter takes place. Therefore, the transformer is to be provided only once within the device. However, this requires that the coupling of an AC signal generated by the communication unit as a communication signal via the transmitter at the same time superimposed on any existing and to be detected by the detection unit AC signal. Due to this, on the one hand the communication signal can be misinterpreted as an arcing signal. In addition, there is also the risk that an actually existing arc is not recognized due to the superimposition of the communication signal and the arc signal emitted by the arc. In any case, there is a risk of misinterpretation of the AC signals detected by the detection unit. According to the invention, this misinterpretation of the AC signals detected by the detection unit in the device is eliminated by the two common control units. Thus, the controller for controlling the detection unit and the communication unit is configured to respectively set the communication unit and the detection unit in an activated and a deactivated state, such that at most one unit of communication and detection unit is in the activated state. In this way, first time periods are generated in which the detection unit, but not the communication unit is activated. Furthermore, second time periods are generated in which the communication unit, but not the detection unit is activated. The coupling of the communication signal through the communication unit takes place only in their activated - but not in their deactivated state. Accordingly, the detection and / or processing of the AC signal by the detection unit takes place only in the activated - but not in the deactivated state of the detection unit. Thus, coupling of the communication signal is suppressed within the first time period and therefore can not cause any misinterpretation in the reception and / or processing of the decoupled from the DC circuit AC signal within the detection unit. In the same way it is ensured that within the second periods, within which a generation and coupling of the communication signal via the transmitter, no reception and / or no processing of a possibly received AC signal by the detection unit takes place. A deactivated state of the detection unit can be brought about in a simple manner via the controller, by the control of the processing of AC signals by the 16-190-P-WO - 6 ^ filed version

Detection unit blocked for the appropriate period. In principle, a reception of AC signals by the detection unit can remain. Accordingly, an activated state of the detection unit can be brought about via the controller by the controller enabling or allowing the processing for the corresponding period of time. Accordingly, the controller may bring about the deactivated state of the communication unit by blocking the generation of the communication signal within the corresponding period of time. Likewise, it can bring about the activated state of the communication unit by allowing the generation of the communication signal within the respective period of time. Alternatively or cumulatively, an activation and deactivation of the detection and / or communication unit can also take place via corresponding switches which prevent, for example, the reception of the AC signal at the detection unit or an output or the transmission of the communication signal of the communication unit.

The first and second periods follow one after the other alternately. In this case, the alternate activation or deactivation of both units - ie the switching from one state to the other - simultaneously and without time offset to each other. In this case, virtually every time a unit of communication and detection unit is activated. However, the alternate activation or deactivation of the detection and the communication unit can also be done with a time offset to each other. In this case, there are periods in which no unit of detection and communication unit is activated. The first and the second time periods are advantageously in a range from 1 ms to 2000 ms, particularly advantageously in a range from 5 ms to 1000 ms. They can have the same time durations relative to one another but also different durations of time.

The device according to the invention further comprises a blocking member which is connected in parallel to the series circuit of capacitor and secondary winding. In this case, the blocking member is formed so that it has the lowest possible impedance with respect to a direct current, with respect to an alternating current in the frequency range of the AC signal, however, the highest possible impedance. Due to the existence and the interconnection of the blocking member within the device, therefore, a direct current as low impedance as possible is passed from the first to the second terminal of the device via the blocking member and not via the secondary winding of the transformer. Within the DC circuits in question, a current typically flows with a relatively high DC component and a relatively low AC component. In this case, the AC component results, for example, from the deliberate coupling of the AC signal as a communication signal 16-190-P-WO - 7 - filed and / or from the existence of an AC signal to be detected in the DC circuit - for example, as a result of an arc. In the case of the blocking element connected between the first and the second terminal, the DC component flows through the blocking element which is low-impedance for it, while the alternating current component-for example the AC signals to be detected and the communication signal-are conducted via the series connection of capacitor and secondary winding of the transformer. In a situation in which the device is disposed within a DC line of the DC circuit, for example within a DC connection line, the DC current flowing in the DC line can pass the device largely unhindered. At the same time, it is only minimally dampened. Within the device thus the lowest possible power loss is generated, which would otherwise - if necessary by appropriately vorzuhaltende coolant - should be dissipated.

Both the number and the design of the transformer significantly affect the design and thus the cost of the detection and communication device. As mentioned above, the current flowing in the DC circuits in question usually consists of a relatively high DC component and a comparatively small AC component. Although a high DC component can flow within the DC circuit, the device prevents the flow of a DC component through the secondary winding of the transformer due to the capacitor connected in series thereto. Rather, only AC signals whose frequency is within a preferred frequency range, passed through the secondary winding of the transformer by the series circuit of capacitor and secondary winding of the transformer. Since these are typically low-current AC signals, the transformer design can be made compact and inexpensive. In addition, since only one transformer is to be provided within the device, the entire device can also be kept compact and inexpensive. Other components that affect an activation and deactivation in an advantageous manner lead only apparently to a higher cost, as this is overcompensated by the advantageous construction of the transformer.

In one embodiment of the device, the transformer has, in addition to the primary winding, a further primary winding on the primary side. In this case, the communication unit is connected to the primary winding and the detection unit to the further primary winding. The embodiment may, but not necessarily, have a galvanic connection between the primary winding and the further primary winding. Such a connection can be formed for example by a common reference potential. 16-190-P-WO -_8_- filed version

In an alternative embodiment of the device, the transformer has only a primary winding on its primary side. In this case, the communication unit and the detection unit are connected to the same primary winding of the transformer. It is possible that the communication unit and the detection unit are connected in parallel to each other to the same primary winding of the transformer. Alternatively, it is possible that the communication unit and the detection unit are connected in series with the same primary winding of the transformer. Since the detection unit and the communication unit are connected to the same primary winding, a galvanic connection between the detection unit and the communication unit is usually present, which can be used, for example, as a common reference potential.

In an advantageous embodiment of the device, the detection unit is designed to detect an arc in the DC circuit of the circuit unit. This exploits that an arc generates a so-called arc noise in the circuit affected by it. The arc noise is a mixture of high-frequency AC signals with frequencies within a frequency range of about 1 kHz - 500 kHz. For arc detection, the DC circuit to be monitored for an arc is monitored for the existence of one AC signal or several AC signals of different frequencies within this frequency range. The high-frequency AC signal may be either an AC signal or an AC signal. The one or more possibly existing AC signals are decoupled by the transformer from the DC circuit connected to the device and provided for processing via the primary winding or the further primary winding of the detection unit. If a corresponding AC signal or corresponding AC signals are detected, this is interpreted as an indication of the existence of an arc in the DC circuit. Advantageously, a threshold value is stored within the detection unit, wherein when an AC signal detected by the detection unit exceeds the threshold value with respect to its intensity (eg, current or voltage), this is considered to be an arc in the DC circuit. In this case, a pattern recognition of the AC signals detected by the detection unit can be carried out as a plausibility check for the existence of an arc. In this way, a distinction can be made as to whether the AC signals detected by the detection unit are in fact to be assigned to an arc or to another interference event. Advantageously, the detection unit is designed as disclosed in WO 2015/014683 A1, and has a termination resistor connected in parallel with an input of the detection unit and a low-pass filter. The output of the low-pass filter is connected to a voltage measuring device, which in turn is coupled to an evaluation device 16-190-P-WO -_9_- filed version. The detection unit may be configured to signal a result of the processing of the control. The controller, in turn, may cause the communication unit to communicate an alarm signal to a higher-level controller if there is an indication of an arc.

In an advantageous embodiment of the device, the communication unit or the detection unit is additionally designed for receiving and processing a decoupled via the transformer from the DC circuit further communication signal. The communication signal is also an AC signal, which is coupled from another unit, such as a higher-level controller in the DC circuit. In this way results in a bidirectional communication of the device with the higher-level control, in which the device can operate both as a receiver and as a transmitter in the context of communication. It is particularly advantageous if the detection unit is designed for receiving and processing the further communication signal, and it operates quasi in the context of bidirectional communication as a receiver of the further communication signal, while the communication unit as part of the bidirectional communication of the device with the other unit Sender of the communication signal operates. This design is particularly simple and inexpensive to implement, since the detection unit is designed anyway to receive and process the AC signal to be detected. For this reason, only little effort is required to get the detection unit to receive and process the further communication signal.

If the device is designed for bidirectional communication, in an advantageous embodiment, the communication unit or the detection unit is designed to pass on the further communication signal to the controller. Likewise, the controller is designed to control the detection unit and / or the communication unit as a function of the further communication signal. For example, the superordinate controller can remotely control the device by sending control commands in conjunction with the controller. Corresponding control commands may relate to the times for activating and / or deactivating the detection unit and / or the communication unit. Likewise, further parameters of the detection unit - for example the above-mentioned threshold value - can be communicated and set. The higher-level control can likewise remotely control further components present in the device, if appropriate together with the control. This may, for example, possibly affect existing switches in the device. 16-190-P-WO - 10 - filed version

In one embodiment of the device, the blocking member has an inductance. Alternatively, the locking member may comprise a band-stop filter. The band-stop filter may comprise a parallel connection of an inductor and a capacitor. Optionally, the band-stop filter can additionally also have an ohmic resistance connected in parallel with the inductance and the capacitance. The band-stop filter is designed as high impedance as possible for a frequency band between a first frequency and a second frequency lying above the first frequency. Alternatively, the locking member may also have a notch filter. In contrast to the band-stop filter, the notch filter is designed to be highly impedance-only for a specific frequency but not for a frequency band. Deviating from the specific frequency frequencies are attenuated as little as possible. Advantageously, the blocking member is independent of whether it is designed as an inductance, band-stop filter or notch, matched to the frequency of the communication signal, so that the communication signal within the device by the respective blocking member as completely as possible is diverted to the series circuit of capacitor and secondary winding of the transformer. In an advantageous embodiment of the device, the capacitor and the secondary winding of the transformer are selected such that their series connection at a frequency of the communication signal and / or the further communication signal, a resonant frequency - ie an impedance minimum - has. In this way, the series connection is particularly low-impedance for AC signals having the frequency near the frequency of the communication signal or that of the further communication signal. Therefore, the communication signals can pass through the device between the first and the second connection as unhindered as possible. However, it is also within the scope of the invention that the communication signal has a frequency which differs from the resonant frequency of the series circuit of capacitor and secondary winding of the transformer. In this case, there is a somewhat greater attenuation of the communication signal and / or the further communication signal through the impedance of the series connection. Furthermore, however, a DC component is prevented by the secondary winding of the transformer by the capacitor. In the event that the detection unit and the communication unit are connected in the form of a series circuit with the same primary winding of the transformer, the device in an advantageous embodiment additionally has a controllable by the controller first switch, which is designed, a first and a second signal terminal of Detection unit to connect or disconnect from each other. In this case, the device can optionally also be controlled by the controller 16-190-P-WO - 1 1 - filed version second switch, which is designed to connect a first and a second signal terminal of the communication unit to each other or to separate. In this way, a deactivated state of the detection unit can be realized in a simple manner by short-circuiting the first and second signal terminals of the detection unit by closing the first switch. The reception of corresponding AC signals by the detection unit is thus blocked. Conversely, in the activated state of the detection unit, the first switch is opened and the reception of possibly existing AC signals by the detection unit is ensured. The same applies in a corresponding manner for the communication unit in conjunction with the second switch. In the deactivated state of the communication unit, a closed second switch blocks an injection of the communication signal, while in the activated state of the communication unit an opened second switch permits this.

In an alternative embodiment, when the detection unit and the communication unit are connected in series, the apparatus additionally has a first switch which can be controlled by the controller and is designed to connect or disconnect a first and a second signal terminal of the detection unit via a second capacitor. Furthermore, the device additionally has a controllable by the controller second switch, which is designed to connect a first signal terminal of the communication unit via a diode and a third capacitor to a DC voltage source or to separate from each other. The DC voltage source is used in conjunction with the second switch to shift at certain times a potential on the primary side of the transformer relative to a reference potential by an output voltage of the DC voltage source. Thus, lifting takes place when the second switch is closed when the detection unit is activated, while when the communication unit is activated the second switch is open and there is no lifting of the potential on the primary side. As is also explained in detail in the description of the figures for FIG. 1 b, the first and second switches can be realized in a particularly cost-effective manner in this way. In this case, the DC voltage source is not a separate component in most cases, but - for example, to supply the device - already exists.

In general, the first and second switches may be electromechanical switches, eg, relays or semiconductors. In the case of semiconductor switches, it should be noted that these are designed during their operation to block in both directions. If necessary, it is necessary for this purpose to implement the first and the second switch in each case in the form of two semiconductor switches which are antiserial with respect to their intrinsic diode 16-190-P-WO - 12 - filed version interconnected. However, in the latter embodiment, due to the temporary potential shift, it is possible to realize the first and second switches in the form of only one semiconductor switch. In the event that the detection unit and the communication unit are connected in parallel to the same primary winding of the transformer, an advantageous embodiment of the device additionally comprises a controllable by the third control switch, which is designed, the detection unit, in particular a signal terminal of the detection unit, with the Primary winding to connect or disconnect. In the event that the communication unit to the primary winding and the detection unit are connected to the further primary winding of the transformer, an advantageous embodiment of the device additionally comprises a controllable by the third control switch, which is designed, the detection unit, or a signal terminal of the detection unit to connect or disconnect with the other primary winding. In both embodiments, the device may optionally additionally comprise a controllable by the controller fourth switch which is designed to connect the communication unit, in particular a signal terminal of the communication unit to the primary winding or separate from each other. In these cases, in each case a deactivated state of the detection unit is brought about via an open third switch, whereby the reception of an AC signal to be detected by the detection unit is prevented. An activated state of the detection unit is present when the third switch is closed. Analogous considerations apply to the activated state of the communication unit in conjunction with the fourth switch. An activated state of the communication unit is present when the fourth switch is closed, a deactivated state of the communication unit when the fourth switch is open. The third and the fourth switch may be electromechanical switches - eg relays - or semiconductor switches.

A photovoltaic (PV) plant according to the invention has a DC circuit. The DC circuit includes a photovoltaic (PV) generator, a positive DC link, a negative DC link and a DC input of an inverter. The DC input of the inverter is connected to the PV generator via the positive and the negative DC connection line. The inverter is designed to convert DC to AC and has its output connected to an AC grid. The photovoltaic (PV) system is characterized in that the DC circuit of the photovoltaic (PV) system further comprises a device according to the invention. The device is inside one of the DC connection lines 16-190-P-WO-13- filed socket connecting a pole of the PV generator with a DC input terminal of the inverter, wherein the first and the second terminal of the device with only one of the DC connecting lines, either exclusively with the positive or exclusively with the negative DC connection line, is connected. It is desired that the DC component can pass through the device from the first terminal to the second terminal as unhindered as possible. This is ensured in the case of the PV system according to the invention by the blocking member of the device, which connects the first terminal to the second terminal of the device and is connected in parallel with the series circuit of capacitor and secondary winding. The blocking element is designed as low impedance as possible for a DC current flowing in the DC connecting line, while it is designed to be highly impedance-effective for an alternating current component possibly flowing in the DC connecting line. Advantageously, the blocking member is designed as an inductance, a band-stop filter or as a notch filter. A caused by the DC component energy flow within DC interconnects leads so only to a low power loss within the device. This results in the advantages already mentioned in the description of the device.

In a variant of a PV system not according to the invention, a circuit arrangement similar to the device according to the invention, which, in contrast to the device according to the invention, however, has no blocking member, is connected to the positive DC connecting line with a first connection and to the negative DC connecting line with a second connection , In this embodiment of the PV system, it is undesirable for the DC component to pass unhindered through the circuit arrangement from the first connection to the second connection, since in this way a short circuit of the PV generator would be generated. Accordingly, it is desirable here that the circuit arrangement for the DC component has the highest possible impedance. Only AC signals, for example the communication signal, the further communication signal and the AC signal to be detected should be able to pass through the circuit as unhindered as possible. Therefore, the circuit arrangement in this variant of the PV system not according to the invention has no blocking element parallel to the series connection of capacitor and secondary winding. In this way, the capacitor prevents the DC component from passing unimpeded through the circuit arrangement from the first connection to the second connection, and the circuit arrangement therefore has a high impedance for the DC component. Although such a circuit arrangement, as well as their interconnection within the PV system in principle allows a coupling or uncoupling of AC signals, but they involve disadvantages compared to the device according to the invention or the invention 16-190-P-WO - 14 - filed version of the PV system. The essential differences and their disadvantages are explained in more detail in the description of FIG. 5b.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention will be further explained and described with reference to preferred embodiments shown in the figures. shows a first embodiment of the device according to the invention, in which the detection unit and the communication unit are connected in the form of a series circuit with the same primary winding in a first variant; and

1 b shows a further embodiment of the device according to the invention, in which the detection unit and the communication unit are connected in the form of a series connection to the same primary winding; and

Fig. 2a shows a second embodiment of the device according to the invention, in which the detection unit and the communication unit are connected in parallel to each other to the same primary winding; and

Fig. 2b shows a third embodiment of the device according to the invention, in which the detection unit and the communication unit are connected in parallel to each other to the same primary winding; and

3 shows a fourth embodiment of the device according to the invention, wherein a transformer has a primary winding and a further primary winding on a primary side; and

4 shows state curves of the communication unit and the detection unit;

and

5a shows an embodiment of a photovoltaic (PV) according to the invention,

Investment; and

Fig. 5b shows a photovoltaic (PV) system with an alternative integration of a

Detection device. 16-190-P-WO - 15 - filed

DESCRIPTION OF THE FIGURES

In Fig. 1 a, a first embodiment of the device 1 according to the invention for the detection of AC signals from a DC circuit of a circuit unit and for communication is shown. The device 1 has a first 2.1 and a second connection 2.2 for connecting the DC circuit. The device 1 furthermore has a communication unit 8 with a first 18.1 and a second signal terminal 18.2, a detection unit 9 with a first 19.1 and a second signal terminal 19.2 and a transformer 7 with a primary winding 71p on a primary side 7p and a secondary winding 71s on one Secondary side 7s of the transformer 7. The transformer 7 is designed for coupling and decoupling AC signals into and out of the DC circuit of the circuit unit. The communication unit 9 is designed to generate an AC signal as a communication signal and coupled via the transformer 7 in the DC circuit. The detection unit 9 is designed to receive and process a coupled out of the DC circuit via the transformer 7 AC signal. The communication unit 8 and the detection unit 9 are connected in the form of a series circuit with the same primary winding 71 p of the transformer 7. Furthermore, the device 1 includes a controller 10 for controlling the communication unit 9 and the detection unit 8, which is designed to put each of the units 8, 9 respectively in an activated and a deactivated state. The device 1 has a controllable by the controller 10 first switch 1 1 .1 on. The first switch 1 1 .1 is designed to connect the first signal terminal 19. 1 and the second signal terminal 19. 2 of the detection unit 9 in a low-impedance manner - and thus to bridge the signal terminals 19. 1, 19. 2 of the detection unit 9 - or to separate them from one another. Furthermore, the device 1 has a controllable by the controller 10 second switch 1 1.2, which is designed to the first 18.1 and the second signal port 18.2 of the communication unit 8 niederimpedant to interconnect - and thus the signal terminals 18.1, 18.2 of the communication unit 8 to bridge - or separate from each other. The first 1 1 .1 and second switches 1 1.2 may each comprise a semiconductor switch or an electromechanical switch.

In the illustrated case, the first signal terminal 19. 1 of the detection unit 9 and the second signal terminal 18. 2 of the communication unit 8 are connected to a reference potential 21. However, the illustrated connection of the reference potential 21 is only an example and not 16-190-P-WO - 16 - as amended. Alternatively to the illustrated variant, it is also possible that the reference potential 21 is connected to the first signal terminal 18.1 of the communication unit or to the second signal terminal 19.2 of the detection unit 9. The first terminal 2.1 is connected via a series circuit of a capacitor 6 and the secondary winding 71 s of the transformer 7 to the second terminal 2.2 of the device 1. Parallel to the series circuit of capacitor 6 and secondary winding 71 s, a blocking member 5 is connected. The blocking member 5 is here - as in the following figures 1 b, 2 a, 2 b, 3 and 5 a - realized by way of example in the form of an inductance. However, it is alternatively possible in each of the figures that the locking member 5 is formed as a band-stop filter or a notch filter.

In operation of the device 1, the communication unit 8 and the detection unit 9 are alternately set to an activated and a deactivated state by the controller 10, so that when the detection unit 9 is in the activated state, the communication unit 8 is in the deactivated state. In particular, at most each time one of the units 8, 9 is present in the activated state. In this case, the communication unit 8 is designed to perform a generation and / or coupling of the communication signal only in the activated state - but not in the deactivated state. For this purpose, in the deactivated state of the communication unit 8, the second switch 1 1 .2 closed by the controller 10, while it is open in the activated state of the communication unit 8 by the controller 10. As a result, a coupling of the communication signal via the transformer 7 is prevented in the DC circuit. In addition, by the controller 10, generation of the communication signal by the communication unit 8 can be suppressed. Both measures (i.e. "suppression of the generation of the communication signal" and "closing of the second switch 1 1.2") each individually lead to a deactivation of the communication unit 8 and are therefore redundant to one another. Although one of the measures for deactivating the communication unit 8 is sufficient in the context of the invention, here the redundancy of a one-fault security serves to deactivate the communication unit 8 even if one of the measures fails.

Furthermore, the detection unit 9 is designed to receive and / or process an AC signal coupled out of the DC circuit only in its activated state, but not in its deactivated state. For this purpose, the processing of a possibly coupled via the transformer 7 AC signal is suppressed by the controller 10 in the deactivated state of the detection unit 9. In addition, the first switch 1 is 1.1 - driven by the controller 10 - closed while in the activated state of the 16-190-P-WO - 17 - as filed

Detection unit 9 - driven by the controller 10 - is opened. In the case of the detection unit 9, both measures (i.e. "suppression of processing" and "closing of the first switch 11 .1") alone lead to a deactivation of the detection unit 9, which is why one of the measures is already sufficient within the scope of the invention. The redundancy is selected here - analogous to the communication unit 8 - due to the one-fault safety. Since the AC signals to be detected by the detection unit 9 are usually small in comparison to the communication signals generated by the communication unit 8, the detection unit 9 is simultaneously protected by the closed first switch 1 1 .1 from overloading and any possible damage associated therewith. Furthermore, the communication signal generated by the communication unit 8 is not additionally attenuated by an input impedance of the detection unit 9. Rather, the generated communication signal via the closed first switch 1 1.1 low impedance to the detection unit 9 passed over.

In this way, first time periods are created, within which the detection unit 8 receives and processes possibly existing and decoupled AC signals in the DC circuit. This is followed by second time periods in which the detection unit 8 is deactivated and can not receive AC signals due to the closed first switch 1.1, while the communication unit 8 in the activated state couples communication signals via the transformer 7 into the DC circuit. Since the first 19. 1 and the second signal terminal 19. 2 of the detection unit 8 are bridged with low impedance by the first switch 1 1 .1, an attenuation of the communication signal by an input impedance of the detection unit 9 is prevented. Likewise, the input of the detection unit 9 is protected against overdriving and associated possible damage to the communication signal.

1 b shows a further variant of the device 1, which is largely similar to the embodiment of FIG. 1 a, which is why only the differences from the embodiment according to FIG. 1 a are shown below. The same reference numerals in Fig. 1 b as well as the following figures identify the same or equivalent elements. In contrast to FIG. 1 a, the device 1 has a DC voltage source 12 which is designed, in conjunction with the second switch 1 1.2, to temporarily shift a potential on the primary side 7p of the transformer 7 relative to a voltage value U ₂ i of the reference potential 21 , For this purpose, the first signal terminal 18. 1 of the communication unit 8 is connected to an output of the DC voltage source 12 via a series connection of a third capacitor 24, a diode 13 and the second switch 1 1 .2. Furthermore, the device has a second capacitor 23 connected to the second signal terminal 19. 2 of the detection unit 9. Of the 16-190-P-WO - 18 - filed version first switch 1 1.1 is connected on one side with the first signal terminal 19.1 of the detection unit 9 and on the other side with the capacitor 23. When the second switch 1 1.2 is closed, the potential of the primary side 7p of the transformer 7 is shifted relative to the voltage value U ₂ i of the reference potential 21. In this case, the second 23 and the third capacitor 24 block a DC component of the potential-shifted primary side 7p with respect to the first signal terminal 18.1 of the communication unit 8 and the second signal terminal 19.2 of the detection unit 9 and thus prevent an override of the units (8, 9).

In contrast to the embodiment of the device 1 according to FIG. 1a, in the embodiment according to FIG. 1b both the first 11.1 and the second switch 11.2 can be realized in the form of only one semiconductor switch, for example a MOSFET. For a better understanding of the operation of the device 1 each intrinsic diodes of the respective semiconductor switches 1 1.1, 1 1.2 are shown. The diode 13 is antiserially connected with respect to its forward direction to the intrinsic diode of the second semiconductor switch 1 1 .2. The bidirectional blocking in the open state of the first switch 1 1 .1 is ensured by the potential shift poles the intrinsic diode of the first semiconductor switch 1 1.1 in the open state in the reverse direction. For this purpose, advantageously, the potential shift and thus the output voltage U- | _{2 of} the DC voltage source 12 is selected so that an AC signal to be detected at any time completely above the reference potential 21 with the voltage value U ₂ i. In this case, the voltage drop across the diode 13 with the forward voltage U _D, 13 and, if necessary, that of the second switch 1 1 .2 in the conductive state to be considered. For the output voltage U _{12 of} the DC voltage source 12 thus applies Ui ₂ > U ₀ , AC + U _D , 13 + U ₂ i where U ₀ , AC denotes a maximum allowable amplitude of the AC signal to be detected, the maximum allowable amplitude UO.AC of the AC signal to be detected results from the individual design of the detection unit 9 and corresponds to a voltage value whose exceeding at the signal inputs 19.1, 19.2, for example, an override of the detection unit 9 has the consequence. In concrete terms, the output voltage Ui _{2 of} the DC voltage source 12 can be, for example, at least 3.3V above the voltage value U _{21 of} the reference potential 21. With such a choice of the output voltage U _{12 of} the DC voltage source 12 ensures that at a maximum allowable amplitude U _0, AC in the amount of 3V of the AC signal to be detected, the intrinsic diode of the first switch 1 1 .1 associated semiconductor switch always poled in the reverse direction is when the forward voltage U _{D 13 of} the diode 13 is below 0.3V. Therefore, here the first switch 1 1.1 can be realized in the form of only one semiconductor switch. A bidirectional blocking of the second 16-190-P-WO - 19 - as filed

Semiconductor switch 1 1 .2 in its open state via the diode 13, in particular via the forward direction relative to the intrinsic diode of the second semiconductor switch 1 1.2.

FIG. 2a shows a second embodiment of the device 1 according to the invention. From the basic structure, the device 1 of FIG. 2a corresponds to the embodiment shown in FIG. 1a. Therefore, with regard to the basic structure and the basic mode of operation, reference is made to the embodiments under FIG. 1 a and only the differences from the first embodiment will be presented below.

In contrast to the variant shown in FIG. 1 a, in the device 1 according to FIG. 2 a, the communication unit 8 and the detection unit 9 are connected in parallel to the same primary winding 71 p of the transformer 7. The device 1 has no first 1.1 and no second switch 11.2 which are designed to connect or disconnect the first 18.1, 19.1 and the second signal connection 18.2, 19.2 of the communication unit 8 or the detection unit 9, respectively. Instead, the device 1 has a third 1 1 .3 and a fourth switch 1 1 .4, which are each controlled via the controller 10. In this case, the first signal terminal 19.1 of the detection unit 9 is connected via the third switch 1.3 to the first signal terminal 18.1 of the communication unit 8. Furthermore, the second signal terminal 18.2 of the communication unit 8 is connected to the second signal terminal 19.2 of the detection unit 9 via the fourth switch 11 .4. In this way, the third switch 1 1.3 is designed to connect the detection unit 9 to the primary winding 71 s or to separate from each other. Likewise, the fourth switch 1 1 .4 is thus designed to connect or disconnect the communication unit 8 with the primary winding 71 p. In the activated state of the communication unit 8, the fourth switch 1.4 is closed by the controller 10 and opened in the deactivated state of the communication unit 8. Furthermore, in the activated state of the detection unit 9, the third switch 1 1 .3 is closed by the controller 10 and opened in the deactivated state of the detection unit 9. The third 1.3 and the fourth switch 1.4 can each comprise an electromechanical switch or a semiconductor switch.

Similarly to FIG. 1 a, the communication unit 8 and the detection unit 9 are alternately set to an activated and a deactivated state by the controller 10 during operation of the device 1, so that when the detection unit 9 is in the activated state, the communication unit 8 is in the deactivated state. Due to the associated with the state of the communication unit 8 switch position of the fourth 16-190-P-WO - 20 - filed version

Switch 1.4, the communication unit 8 is only in the activated - but not in the deactivated state able to couple a communication signal via the transformer 7 in the DC circuit connected to the device. Likewise, due to the associated with the state of the detection unit 9 switch position of the third switch 1 1 .3 the detection unit 9 only in the activated state - but not in the state in a position capable of an AC signal coupled via the transformer 7 from the DC circuit will, to receive. In this case, the controller 10 of the detection unit 9 can release processing of an AC signal only in its activated state and suppress it in the deactivated state. The suppression of the processing of the AC signal within the deactivated state of the detection unit 9 by the controller 10 is useful for redundancy reasons, but not absolutely necessary, since the reception of a decoupled via the transformer 7 from the DC circuit AC signal in the deactivated state of the detection unit. 9 Already due to the opened third switch 1 1 .3 is prevented. Likewise, suppression of the generation of a communication signal in the deactivated state of the communication unit 8 for redundancy reasons is useful, but not mandatory in the invention, since due to the opened in the deactivated state of the communication unit fourth switch 1.4 a coupling of any communication signal generated within the communication unit 8 is already suppressed.

FIG. 2b shows a third embodiment of the device 1 according to the invention. From the basic structure, the device 1 of FIG. 2b corresponds to the embodiment shown in FIG. 2a. Therefore, with regard to the basic structure and the basic mode of operation, reference is made to the embodiments under FIG. 2a and only the differences from the second embodiment will be described below.

In contrast to FIG. 2 a, the third embodiment according to FIG. 2 b has no third 1 1 .3 and no fourth switch 1 1 .4. Instead, a signal terminal - in this case the first signal terminal 19. 1 - of the detection unit 9 is connected via a band-stop filter 20 to the primary winding 71 p of the transformer 7. Alternatively to the illustrated variant, however, it is also possible that the band-stop filter is arranged within a connecting line of the second signal terminal 19.2 of the detection unit 9 with the primary coil 71p. The band-stop filter 20 is realized in the form of a parallel connection of an inductance, a capacitor and an ohmic resistance and designed with respect to their impedance maximum to the frequency of the communication signal. The ohmic resistance of the band-stop filter is optional and can be omitted. The band-stop filter 20 has a narrow impedance maximum with a high edge steepness and is therefore capable of: 16-190-P-WO - 21 - submitted version on the one hand sufficient to dampen the communication signal and thus to avoid overdriving the detection unit 9, and

on the other hand via the transformer 7 from the DC circuit coupled out AC signals, provided that their frequency has a sufficient distance from the communication frequency, to receive in a strength that allows further processing. The reference potential 21 is connected by way of example to the second signal terminal 18.2 of the communication unit 8 and the second signal terminal 19.2 of the detection unit 9.

In the present embodiment, the deactivated state of the communication unit 8 is brought about by suppressing the generation of the AC signal as a communication signal by the controller 10 and accordingly allowing it in the activated state. The deactivated state of the detection unit 9 is brought about by blocking the processing of an AC signal by the controller 10. Accordingly, the activated state of the detection unit 9 is brought about by the controller 10 of the detection unit allowing the processing of an AC signal.

3 shows a fourth embodiment of the device 1 according to the invention. From the basic construction, this is similar to the embodiment shown in FIG. 2a. Therefore, with regard to the basic structure and the basic mode of operation, reference is made to the statements under FIG. 2a and only the differences from the embodiment according to FIG. 2a are shown below.

In contrast to FIG. 2 a, the embodiment according to FIG. 3 has a further primary winding 72 p on the primary side of the transformer 7 in addition to the primary winding 71 p. In this case, the communication unit 8 is connected via a controllable by the controller 10 fourth switch 1.4 with the primary winding 71 p and the detection unit 9 via a controllable by the controller 10 third switch 1 1 .3 connected to the other primary winding 72p. This variant makes it possible to design winding ratios or transmission ratios between the primary side 7p and the secondary side 7s of the transformer 7 for the communication unit 8 on the one hand and the detection unit 9 on the other hand different from each other. Thus, the detection unit 9 usually requires a higher winding ratio between primary side 7p and secondary side 7s than the communication unit 8 due to a desired amplification in the coupling of the AC signal to be detected from the DC circuit. while it is open in the disabled state. 16-190-P-WO - 22 - filed version

The same applies to the activated or deactivated state of the detection unit 9 in conjunction with the third switch 1 1 .3. In the illustrated case, the primary winding 71p is galvanically isolated from the further primary winding 72p. In the context of the invention, however, a variant is also possible in which a connection of the primary winding 71p, which is assigned to the second signal terminal 18.2 of the communication unit 8, is connected to a terminal of the further primary winding 72p, which is assigned to the first signal terminal 19.1 of the detection unit 9 is. This results in a galvanic connection of the primary winding with the further primary winding 72p, which can optionally be connected to a reference potential (not shown in FIG. 3) assigned to the communication unit 8 and the detection unit 9.

Otherwise, the operation of the device 1 according to FIG. 3 corresponds to the operation of the embodiment according to FIG. 2a, for which reason reference is made here to the text passages listed there.

FIG. 4 shows state profiles for the communication unit 8 and the detection unit 9. The state progression 32 indicates the time-dependent activation or deactivation state of the communication unit 8, while the state progression 33 represents the corresponding time-dependent activation or deactivation state of the detection unit 9. In the case illustrated, the deactivation times of one of the units 8, 9 do not coincide with the corresponding activation times of the respective other unit 9, 8 and there are time periods 34 in which none of the units of communication unit 8 and detection unit 9 is in the activated state. As an alternative to the illustrated state curves 32, 33, however, it is also possible within the scope of the invention for the activation of one of the units 8, 9 to take place quasi simultaneously with the deactivation of the respective other unit 9, 8. In this case, the periods 34 during which none of the units 8, 9 are activated are negligibly small. In any case, however, it applies that at any time at most one of the units of communication unit 8 and detection unit 9 is present in the activated state.

FIG. 5 a shows an embodiment of a photovoltaic (PV) system according to the invention. The PV system 17 has a DC circuit which comprises a PV generator 14, a positive DC connection line 15, a negative DC connection line 16 and a DC input of an inverter 3. The inverter 3 is connected to a network 4 for supplying electrical power. In the illustrated example, it is a single-stage, three-phase inverter 3. In the invention, however, the inverter can also be single-phase and / or multi-stage (ie with a between the DC and 16-190-P-WO - 23 - filed

Input and the DC-AC converter arranged DC / DC converter) be executed. The PV system 17 furthermore has a device 1 according to the invention, which is connected with its first 2.1 and its second connection 2.2 to the DC circuit of the PV system 17 as a circuit unit. In the illustrated case, the device 1 is arranged within the negative DC connection line 16 of the PV system 17. Alternatively, however, it is also possible that the device 1 is arranged within the positive DC connection line 15 of the PV system 17. The device 1 has as detection unit 9 on an arc detection unit and corresponds in the illustrated case of the second embodiment of FIG. 2a, in which the detection unit 9 and the communication unit 8 are connected parallel to each other to the same primary winding 71 p of the transformer 7. Since the device 1 is arranged with its first 2.1 and its second terminal 2.2 within one of the DC connection lines 15, 16, it is necessary that the device 1 between the first 2.1 and the second connection 2.2 with respect to a flowing in the DC circuit DC component is designed low impedance. The low impedance between the first 2.1 and the second terminal 2.2 is provided by the blocking member 5 of the device 1 - shown here in the form of an inductance. The blocking member has a higher impedance with respect to an AC component, for example, an AC signal associated with arc noise and / or a communication signal to be detected. Due to this, an alternating current component flowing in the DC circuit - and thus the AC signal to be detected - is conducted via the secondary winding 71 s of the transformer 7.

The illustrated embodiment of the device 1 is to be understood merely as an example. Alternatively, the other embodiments of the device 1 are possible.

FIG. 5b shows a variant of a photovoltaic (PV) plant not according to the invention. With regard to its construction, the PV system 26 basically corresponds to the first embodiment according to FIG. 5 a, for which reason reference is made to the statements there in relation to the similarities.

In contrast to the first embodiment, a circuit arrangement 25 similar to the device 1 according to FIG. 5 b is no longer arranged within one of the DC connection lines 15, 16 but rather between the positive 15 and the negative DC connection line 16. Specifically, a first terminal 25.1 of the circuit arrangement 25 with the positive DC connection line 15 and a second connection 25.2 of the circuit arrangement 25 with the negative DC connection line 16 16-190-P-WO - 24 - filed. Although the circuit 25 between the first 25.1 and the second terminal 25.2 - analogous to the device 1 according to the invention - the series circuit of capacitor 6 and secondary winding 71 s of the transformer 7, contrary to the device 1 according to the invention but not the blocking element connected in parallel to the series connection 5. Optionally, the PV system 26 in one of the DC connection lines 15, 16 -in this case within the positive DC connection line 15 -between the connection of the circuit arrangement 25 and the inverter 3, can furthermore have a band-stop filter 22 or an inductance which ensures the AC signal to be detected and / or a communication signal are conducted as an AC signal via the circuit arrangement 25 - here the series connection of capacitor 6 and secondary winding 71 s of the transformer 7 - and not via an undesired path connected in parallel with the circuit arrangement 25.

Such a circuit arrangement 25 corresponds - apart from the non-existent in the circuit arrangement 25 locking member 5 between the first 25.1 and the second terminal 25.2 of the device 1 according to the invention. Nevertheless, the circuit arrangement 25, as well as its connection in the DC circuit of the PV system 26 according to FIG. 5b, has some disadvantages compared to the PV system according to the invention according to FIG. 5a. Thus, for example, a dielectric strength of the capacitance 6 in the arrangement according to FIG. 5b is to be interpreted at least to be the voltage difference between the DC connecting lines 15, 16 (here: 1000V to 1500V), whereas in the case of the device 1 according to the invention as well as the PV system according to the invention. Annex 17 may be much smaller according to FIG. 5a. Therefore, in the embodiment according to FIG. 5 a, favorable ceramic capacitors can be used, whereas, in contrast to a variant of the circuit arrangement according to the invention and the corresponding PV system 26 according to FIG. 5 b, comparatively expensive film capacitors must be used. Furthermore, when transmitting an AC signal as a communication signal, it is desirable to keep as constant as possible a signal level defined by a voltage amplitude of the AC signal between the first 2.1 and the second terminal 2.2 of the device when it is coupled in. For this purpose, a loss of the signal level via components connected in parallel must be compensated or corrected accordingly. In the case of the PV system 17 according to the invention according to FIG. 5a, the loss of the signal level is only generated by the blocking member 5 and also influenced only by its component tolerances. In contrast, there is a loss of a signal level in a PV system 26 as shown in FIG. 5b 16-190-P-WO - 25 - filed on a larger number of components whose component tolerances add up. In addition, during operation of the PV system 26, time-dependent impedances in the loss of the signal level must be taken into account. Therefore, a compensation of the losses in the signal level in the embodiment of FIG. 5b compared to the PV system 17 shown in FIG. 5a significantly more expensive.

O - 26 - submitted version

LIST OF REFERENCE NUMBERS

1 device

.1, 2.2 Connection

3 inverters

4 network

5 locking member

6 capacitor

7 transformers

7p primary side

7s secondary side

p, 72p primary winding

71 s secondary winding

8 communication unit

9 detection unit

10 control

- 1 1 .4 switch

12 voltage source

13 diode

14 photovoltaic (PV) generator

15 DC connection line

16 DC connection line

17 photovoltaic (PV) system

18 signal connection

19 signal connection

20 band-stop filter

21 reference potential

22 band-stop filter

23, 24 capacitor

25 circuit arrangement

25. 2 connection

26 Photovoltaic (PV) plant

32, 33 State history

34 time span

Claims

16-190-P-WO - 27 - as filed PATENTAL CLAIMS

1. Device (1) for detecting AC signals from a DC circuit of a circuit unit and having communication,

a first terminal (2.1) and a second terminal (2.2) for connection to the DC circuit of the circuit unit,

a transformer (7) having a primary winding (71p) arranged on a primary side (7p) of the transformer (7) and a secondary winding (71s) arranged on a secondary side (7s) of the transformer (7), the first connection ( 2.1) via a series circuit of a capacitor (6) and the secondary winding (71 s) of the transformer (7) to the second terminal (2.

2) is connected,

- A blocking member (5) which is connected in parallel to the series circuit of capacitor (6) and secondary winding (71 s),

a communication unit (8) which is designed to generate an AC signal as a communication signal and to couple it via the transformer (7) into the DC circuit of the circuit unit,

a detection unit (9) which is designed to receive and process an AC signal coupled out of the DC circuit via the transformer (7),

- Wherein the communication unit (8) and the detection unit (9) are connected in common to the primary side (7p) of the transformer (7), and

a controller (10) for controlling the communication unit (8) and the detection unit (9),

characterized,

- That the controller (10) is designed to enable the communication unit (8) and the detection unit (9) in each case in an activated and a deactivated state, - wherein a coupling of the communication signal is carried out only in the activated state of the communication unit (8),

- Receiving and / or processing of the AC signal is carried out only in the activated state of the detection unit (9), and

- wherein the controller (10) is adapted to control the states of the communication unit (8) and the detection unit (9) such that at any time at most one unit of communication unit (8) and detection unit (9) in the activated state. 2. Device (1) according to claim 1, characterized in that the communication unit (8) and the detection unit (9) to the same primary winding (71 p) of the transformer (7) connected are.

3. Device (1) according to claim 1, characterized in that the transformer (7) in addition to the primary winding (71 p) has a further primary winding (72p) on the primary side (7p), wherein the communication unit (8) to the primary winding (71 p) and the detection unit (9) to the further primary winding (72p) of the transformer (7) is connected.

4. Device (1) according to claim 2, characterized in that the communication unit (8) and the detection unit (9) parallel to each other to the same primary winding (71 p) of the transformer (7) are connected.

5. Device (1) according to claim 2, characterized in that the communication unit (8) and the detection unit (9) are connected as a series circuit with the same primary winding (71 p) of the transformer (7).

6. Device (1) according to one of claims 1 to 5, characterized in that the detection unit (9) is designed to detect an arc in the DC circuit of the circuit unit.

7. Device (1) according to any one of claims 1 to 6, characterized in that the communication unit (8) or the detection unit (9) in addition to receiving and processing via the transformer (7) is decoupled from the DC circuit further communication signal ,

8. Device (1) according to claim 7, characterized in that the communication unit (8) or the detection unit (9) is adapted to pass the further communication signal to the controller (10), and wherein the controller (10) is designed, the Detection unit (9) and / or to control the communication unit (8) in dependence of the further communication signal.

9. Device (1) according to one of claims 1 to 8, characterized in that the locking member (5) has an inductance or a band-stop filter. 10. Device (1) according to one of claims 1 to 9, characterized in that the capacitor (6) and the secondary winding (71 s) of the transformer (7) are selected such in that their series connection has a resonance frequency at a frequency of the communication signal and / or of the further communication signal. 1 1. Device (1) according to one of claims 1 to 10, as far as related to claim 5, characterized in that the device (1) in addition by the controller (10) controllable first switch (1 1.1), which is designed in that a first (19.1) and a second signal terminal (19.2) of the detection unit (9) are connected to one another or separated from one another, and wherein the device (1) optionally additionally includes a second switch (11.1 .2) controllable by the control (10) ) configured to connect or disconnect a first (18.1) and a second signal terminal (18.2) of the communication unit (8) with each other. 12. Device (1) according to one of claims 1 to 10, as far as related back to claim 5, characterized in that the device (1) in addition by the controller (10) controllable first switch (1 1.1), which is designed a first (19.1) and a second signal terminal (19.2) of the detection unit (9) via a second capacitor (23) to connect or disconnect from each other, and

- wherein the device (1) in addition by the controller (10) controllable second switch (1 1 .2), which is designed, a first signal terminal (18.1) of the communication unit (8) via a diode (13) and a third Capacitor (24) with a DC voltage source (12) to connect or disconnect. 13. Device (1) according to one of claims 1 to 10, as far as related back to claim 3 or 4, characterized in that the device (1) additionally by the controller (10) controllable third switch (1 1 .3), which is designed to connect or disconnect the detection unit (9) to the primary winding (71p) or to the further primary winding (72p), and wherein the device (1) optionally additionally comprises a fourth switch (10) which can be controlled by the controller (10). 1 1.4) adapted to connect or disconnect the communication unit (8) with the primary winding (71 p). A photovoltaic (PV) system (17) comprising a DC circuit comprising a photovoltaic (PV) generator (14), a positive (15) and a negative DC connection line (16) and a DC input of an inverter (3 ), wherein the DC input via the positive (15) 16-190-P-WO - 30 - filed and the negative DC connecting line (16) to the PV generator (14) is connected, wherein the inverter (3) is designed for the conversion of direct current into alternating current and the output side with a AC network (4), characterized in that the DC circuit of the PV system (17) further comprises a device (1) according to one of claims 1 to 13, wherein the device (1) within one of the DC connecting lines (15, 16) which connects one pole of the PV generator (14) to a DC input terminal of the inverter (3).