BE1024328B1 - Multi-strand photovoltaic system, method for operating such and strand shutdown device for such - Google Patents

Abstract

The invention relates to a multi-strand photovoltaic system with a Strandabschaltvorrichtung, a method for switching off and on again a single or individual photovoltaic strands (10, 10 ') from or to a parallel circuit with other photovoltaic strings, in particular to a common inverter and a Strandabschaltvorrichtung this. The multi-strand photovoltaic system (1) comprises: two or more photovoltaic strands (10, 10 ') which are each formed by series-connected photovoltaic modules (12, 12'), a central collection point (22a, 22b), on which the photovoltaic strings (10, 10 ') are connected in parallel by means of stranded conductors to produce a current-carrying connection between the photovoltaic strings and the central collection point, wherein at least one of the photovoltaic strings (10, 10') in the associated branch line between the photovoltaic modules of this photovoltaic string and the central collection point has a Strangabschaltvorrichtung (40), by means of which the current-carrying connection between the at least one photovoltaic string (10, 10 ') and the central collection point (22a, 22b) is user-controlled separable for selectively shutting off the at least one photovoltaic string individually from the parallel circuit, wherein at least one of the photovoltaic cells Strands remains in operation.

Description

(30) Priority information:

(73) Owner:

PHOENIX CONTACT GmbH & Co. KG

32825, BLOMBERG

Germany (72) inventor:

HÖFT Wolfgang 32683 BARNTRUP Germany

END Andreas Stefan 31860 EMMERTHAL Germany (54) Multistrand photovoltaic system, method for operating such and string shutdown device for such (57) The invention relates to a multistrand photovoltaic system with a string shutdown device, a method for switching off and on again a single or individual photovoltaic Strings (10, 10 ') from or to a parallel connection with further photovoltaic strings, in particular on a common inverter, and a string shutdown device therefor. The multi-strand photovoltaic system (1) comprises: two or more photovoltaic strings (10, 10 '), which are each formed by series-connected photovoltaic modules (12, 12'), a central collection point (22a, 22b), at which the photovoltaic strings (10, 10 ') are connected in parallel by means of string lines in order to establish a current-carrying connection between the photovoltaic strings and the central collecting point, with at least one of the photovoltaic strands (10, 10') in the associated string line between the Photovoltaic modules of this photovoltaic string and the central collecting point has a string shutdown device (40), by means of which the current-carrying connection between the at least one photovoltaic string (10, 10 ') and the central collecting point (22a, 22b) can be disconnected in a user-controlled manner to specifically switch off the at least one photovoltaic string individually from the parallel connection, at least one of the photovoltaic S remains in operation.

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BELGIAN INVENTION PATENT

FÖD Wirtschaft, K.M.B., Mittelstand & publication number: 1024328 Energy filing number: BE2017 / 5253

Office of Intellectual Property Boarding. Classification: H02S 50/00

Issued on: 01/25/2018

The Minister for Enterprise

Due to the Paris Treaty of March 20, 1883 for the protection of industrial property;

Introduced under the Act of March 28, 1984 on Inventive Patents, Article 22, for applications prior to September 22, 2014;

Based on Title I “Invention Patents” of Book XI of the Economic Code, Article XI.24, introduced for applications from September 22, 2014;

Based on the royal decree of December 2, 1986 on the registration, granting and maintenance of patents for invention, Article 28;

Based on the protocol, taken on 11/04/2017 at the Intellectual Property Office.

Considering that for patent applications that fall within the scope of Title 1, Book XI, of the Economic Code, in accordance with Article XI.19, Section 4, second paragraph, of the Economic Code, if the patent application is the subject of a search report in which a lack of unity of invention within the meaning of paragraph 1 is mentioned, and if the applicant does not limit his application and does not file a divisional application in accordance with the search report, the granted patent will be limited to the claims for which the search report was created.

DECIDES:

Article 1. - An invention patent is granted to:

PHOENIX CONTACT GmbH & Co. KG, Flachsmarktstrasse 8, 32825 BLOMBERG Germany;

represented by :

for a period of 20 years, subject to the payment of the annual patent fees mentioned in Article XI.48, §1 of the Economic Code, for: multi-strand photovoltaic system, method of operating such and string shutdown device for such.

INVENTOR:

HÖFT Wolfgang, Breslauer Ring 9, 32683, BARNTRUP;

END Andreas Stefan, Länder 31, 31860, EMMERTHAL;

PRIORITIES) :

SEPARATION:

Partial application of the previous application: Date of filing of the previous application:

Article 2. - This patent is granted without any prior examination of the patentability of the invention, without guaranteeing the merit of the invention or the accuracy of its description, and at the own risk of the patent applicant (s).

Brussels, 25/01/2018, in special representation:

BE2017 / 5253

Multistrand photovoltaic system, method for operating such and string shutdown device for such

description

Field of the Invention

The invention relates to a multistrand photovoltaic system with a string shutdown device, a method for switching off and on again a single or several individual photovoltaic strings from or to a parallel connection from the photovoltaic strings, in particular on a common inverter, and a string shutdown device therefor.

Background of the Invention

A photovoltaic system typically comprises a large number of photovoltaic modules, which are connected in series to form strings, sometimes also referred to as “strings”, in order to achieve a nominal photovoltaic generator DC voltage of typically currently up to 1000 volts or even 1500 volts. Furthermore, depending on the number of interconnected photovoltaic modules and their individual voltage, if necessary, several of the photovoltaic strings are connected in parallel, of which each photovoltaic string can generate, for example, a nominal current of 10 A. If several lines are connected in parallel, this is also referred to as a multi-line or multi-line connection.

Due to the high voltage and the high currents in the DC voltage part of the photovoltaic system, there is maintenance or malfunctions, e.g. in the event of a fire, the danger that people could be exposed to life-threatening voltages.

Although a photovoltaic system typically has a main disconnector in the so-called generator junction box, this can be used, e.g. in the event of damage from fire, water, hail, etc. on the solar panels or on the connecting cables, do not isolate the area in front of the generator junction box. Furthermore, selective activation of individual photovoltaic modules is also not possible with this.

For this reason, photovoltaic module protection circuits were developed with which the photovoltaic modules can be switched off individually (cf. WO2013 / 026539 A1 and the product SCK-RSD-100 from the applicant). Furthermore, start boxes were developed with which such "intelligent" photovoltaic modules can be reactivated (cf.

WO2014 / 122325 A1 and the products SCK-RSD-400 and SCK-RSD-600 from the applicant).

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So-called optimizers and micro-inverters can only switch off a photovoltaic string in a single string connection by reducing the string-side impedance to such an extent that a short circuit and therefore no voltage is present on the string. In the case of a multi-strand connection, this short circuit enables current flow from the parallel-connected strand to the short-circuited strand. However, this technique cannot be used to switch individual strings in a multi-strand connection.

DE 10 2016 117 049 (not previously published) describes a reverse current protection circuit by means of which it is possible to separate a line from the central collection point in order to prevent cross currents. The aim of DE 10 2016 117 049 is to automatically prevent a current flow against the direction of flow of the photovoltaically generated current from the other photovoltaic strings (cross current or reverse current) by means of the reverse current protection circuit. The present invention builds on this, which is why the disclosure content of DE 10 2016 117 049 is hereby incorporated by reference, and provides the possibility of a single-strand shutdown actively triggered on user request for multi-strand photovoltaic systems.

General description of the invention

The present invention has set itself the task of providing a multi-strand photovoltaic system that can reconcile high security requirements and high yield. Another aspect of the invention is to provide a multistrand photovoltaic system which is easy to maintain and repair and which enables the user to switch off individual photovoltaic strings of the multistrand photovoltaic system as desired, in particular without the multistrand -Have to switch off the photovoltaic system as a whole.

Another aspect of the object of the invention is to provide a string shutdown device for a multistrand photovoltaic system, which is reliable, safe and long-lasting, and has low conduction and heat generation, in particular in conventional, possibly even existing boxes to be installed in a photovoltaic system.

Another aspect of the object of the invention is to provide a method for operating a multi-strand photovoltaic system which offers a high level of safety and flexibility in operation, maintenance and in the event of faults.

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The object of the invention is solved by the subject matter of the independent claims. Advantageous developments of the invention are defined in the subclaims.

The multi-strand photovoltaic system according to the invention comprises two or more photovoltaic strings. The photovoltaic strings are each formed by series-connected photovoltaic modules, the photovoltaic modules being connected in series by means of a two-pole string line (positive pole and negative pole).

The multi-strand photovoltaic system also has a central collection point at which the photovoltaic strings are connected in parallel in order to establish a current-carrying connection between the photovoltaic strings and the central collection point. In other words, the central collection point forms a parallel switching point of the photovoltaic strings.

The multi-strand photovoltaic system preferably further comprises a common inverter, sometimes also called a solar inverter, for the two or more photovoltaic strings, which converts the direct voltage generated by the photovoltaic modules into alternating voltage. The inverter is therefore connected downstream of the central collection point. The multi-strand photovoltaic system can also be used without an inverter, e.g. be connected to a charging unit.

The inverter has a direct current input to which the photovoltaic strings are connected and electrically connected during production. In the multi-strand photovoltaic system, several photovoltaic strings are connected in parallel to the same DC input of the inverter. For this purpose, the multiple photovoltaic strings are connected in parallel via the central collection point, which is upstream of the DC input of the inverter, and then connected to the same DC input of the inverter. The plurality of parallel photovoltaic strings are preferably controlled by the same power optimizer, typically a maximum power point tracker (MPPT), in order to optimize their performance depending on the irradiation situation.

At least one of the parallel photovoltaic strings, preferably all of the parallel photovoltaic strings, at the central collection point or on the inverter now have a string shutdown device in their respective associated string line, in particular between the photovoltaic modules of this respective photovoltaic string and the central gathering point

BE2017 / 5253, by means of which the current-carrying connection between this associated photovoltaic string and the central collection point can be user-controlled, that is to say can be selectively separated at the request of the user, around the at least one photovoltaic string or any desired photovoltaic string, specifically and individually switch off from parallel connection.

In other words, a separate string shutdown device is provided for each photovoltaic string. I.e. one individual or several individual photovoltaic strings can be switched off in a targeted manner and the other photovoltaic strings of the parallel connection remain in operation and can continue to feed in photovoltaically generated electricity via the central collecting point, in particular into the inverter. It is therefore a string shutdown device for user-controlled single string shutdown within the parallel connection from the photovoltaic strings.

Advantageously, the user can e.g. For maintenance purposes, repairs or in the event of localized malfunctions, specifically switch off one or more of the photovoltaic strings individually or disconnect the live connection of the photovoltaic strings desired by the user to the central collection point, so that they no longer feed in electricity via the central collection point. Accordingly, entire photovoltaic strings are switched off (and not just individual photovoltaic modules) or the current-carrying connection of one or more entire photovoltaic strings to the central collection point is disconnected. One advantage lies in the fact that one or more photovoltaic strings can be individually switched off and serviced in a controlled manner, but the other photovoltaic strings remain productive, i.e. that the multi-strand photovoltaic system, although with reduced output, remains fundamentally productive. This means that safety requirements can be met on the one hand and the yield of the multi-strand photovoltaic system can be maintained as far as possible.

Preferably, the string shutdown device between the photovoltaic modules of the associated photovoltaic string and the central collecting point comprises a switch device in at least one branch of the string line (positive pole or negative pole) of the associated photovoltaic string and a control device for controlling the switch device, which functions to control the switch device with it is coupled.

The switch device defines a closed and an open state, and in the closed state conducts the photovoltaically generated current from the

BE2017 / 5253 associated photovoltaic string with little loss through to the central collection point. In the open state, the switch device interrupts the passage of the photovoltaically generated current from the associated photovoltaic string to the central collection point. In other words, the switch device disconnects the connection of the associated photovoltaic string to the central collection point, specifically in the direction of current flow of the current photovoltaically generated by the associated photovoltaic string.

In response to user input, the control device is designed to open the switch device in a user-controlled manner in order to switch off the associated string or to separate it from the central collection point in such a way that the flow of the photovoltaically generated current from the associated photovoltaic string is interrupted.

The control device is preferably also designed to specifically close the associated switch device again after user input, the closing of the associated switch device still being dependent on the fulfillment of test conditions in order to respond to the user input and, if applicable, the fulfillment of the test conditions, the associated photovoltaics Reconnect the k-strand to the central assembly point if both criteria are met.

For example, the string shutdown device can in a housing of a start box belonging to the respective photovoltaic k-string or another string box belonging to the respective photovoltaic k-string or connected in the respective string, which is connected between the series-connected photovoltaic k-modules of the associated photovoltaic k-string and the central collecting point is built in. The user can then switch off the associated string at an external switch on the cross-photovoltaic module box, or the user selectively sends a switch-off trigger signal from one central control of the multi-string photovoltaic system to one or individual string boxes, in response to which Associated string shutdown device or the associated string shutdown devices switches off or switch off the associated photovoltaic strings.

In this respect, the user can advantageously switch off the desired one or more photovoltaic strings or disconnect the current-carrying connection to the central collecting point in an advantageous manner locally on the associated photovoltaic branch or centrally on the plant side, but in particular controlled across photovoltaic modules.

In particular, the control device is designed to receive an external user-generated string shutdown trigger signal and in response to the

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Switch off the triggering signal of the associated photovoltaic string from the parallel connection by the control device opening the switch device and thus disconnecting the current-carrying connection of the associated photovoltaic string, at least in the direction of flow of the current photovoltaically generated by this photovoltaic string, with the central collecting point. The line shutdown device is accordingly, in particular, an actively switchable and / or electronically controlled line shutdown device.

According to a preferred embodiment of the invention, the string cut-off device can additionally comprise a reverse current protection circuit and / or a sensor connected to the control device for measuring an electrical characteristic on the associated photovoltaic string, the control device being designed to respond to the electrical measured with the sensor Parameter to automatically interrupt the connection of the associated photovoltaic string to the central collection point in the reverse flow direction. In other words, the line cut-off device is preferably combined with the reverse current protection circuit according to DE 10 2016 117 049.

The advantages of backflow prevention in accordance with the invention described in DE 10 2016 117 049 and the present targeted, user-controlled shutdown of individual photovoltaic strings can thus be combined synergistically. The string shutdown device and the reverse current protection circuit can advantageously be accommodated in the same housing or in the same string box associated with a specific photovoltaic string, and at least partially have common components.

The switch device is preferably designed to interrupt the current flow in both directions in the open state, that is to say the flow of the current photovoltaically generated by the associated photovoltaic string as well as cross-currents or reverse currents from the other photovoltaic strings connected in parallel in the associated ones Interrupt photovoltaic string.

The switch device can thus advantageously perform a synergistic double function.

The strand cut-off device or the switch device preferably comprises a back-to-back circuit comprising two semiconductor switches, e.g. two transistors, in particular a back-to-back circuit comprising two field-effect transistors, in particular a back-to-back circuit comprising two MOSFETs, which is connected in series in the string line. A back-to7

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Back circuit comprising two semiconductor switches has the advantage that when both semiconductor switches are open, the current-carrying connection is separated in both directions or the current flow is interrupted in both directions.

More preferably, the line shutdown device or the

Switch device a relay, which is connected in series in the string line.

Particularly preferably, the line cut-off device or the switch device comprises a parallel connection from the relay and the back-to-back circuit from two semiconductor switches, in particular a parallel connection from the relay and the back-to-back circuit from two (MOSFET) transistors, the latter Parallel connection is connected in series in the string line. An advantage of this parallel connection is that no high current relay has to be used, but a simple small standard relay can be used.

When switching off, the relay is preferably first opened and the parallel semiconductor switch is only opened after a delay after the relay has opened.

When (re) switching on, the semiconductor switch is first closed and the parallel relay is only closed after a time delay.

As a result, the relay only needs to switch a low voltage in the range of one volt, which prevents sparking at the relay. This contributes to the longevity of the circuit.

In other words, the string shutdown device is designed to first close the semiconductor switches, in particular the MOSFET transistors, when the associated photovoltaic string is connected to the central collecting point, and then to close the relay only after a time delay. As a result, a multiplicity of the switching processes can be advantageously carried out first by the semiconductor switches, e.g. the back-to-back MOSFET circuit can be performed. On the one hand, the number of switching operations of the relay can be kept low, and on the other hand, the relay is relieved during the switching operation by the parallel semiconductor switch. In production operation, however, the relay relieves the semiconductor switches. Nevertheless, when the switch device is open, i.e. when both the semiconductor switches and the relay are open, a bidirectional separation of the electrical connection can be achieved, i.e. the current flow can be interrupted in both directions. As a result, the advantages of individual line disconnection and reverse current prevention can be combined with one another in a simple manner. Furthermore, the relay can be spared, which increases the longevity of the

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Line shutdown device is useful and can be used to ensure safety, reliability and longevity.

Furthermore, the string shutdown device can preferably be designed to check electrical parameters of the associated photovoltaic string in a test routine before the relevant photovoltaic string is switched on again and to close the switch device if predefined threshold values for the electrical parameters are maintained and after user approval. I.e. The switch device is only closed when both are present, i.e. if both the test conditions for the electrical parameters are met and the user is approved for (re) switching on. Only then is the associated photovoltaic string switched on again at the central collection point.

In particular, the semiconductor switches can initially be closed on a test basis and electrical parameters, in particular the phase current, can be measured with the relay still open.

This process can be repeated several times before the relay is also closed, so that the relay can be protected.

In particular, the string shutdown device comprises a current sensor which measures the photovoltaically generated current flow through the associated string line. The string cut-off device preferably closes the relay only when the photovoltaically generated current flowing through the string line exceeds a predefined threshold value. This can ensure that the associated photovoltaic string is only put into operation when it is fully operational.

The string shutdown device or the switch device preferably has a power loss in the production operation of the associated photovoltaic string of less than 1 W, for example at 1000 volts and 10 amperes per photovoltaic string.

The line switch-off device or the switch device can accordingly also comprise semiconductor switches, but preferably the line switch-off device or the switch device has not only semiconductor components, but at least one non-semiconductor-based switch, in particular the relay. The photovoltaically generated current therefore preferably flows at least temporarily, in particular in the permanent production operation of the photovoltaic string, in the part of the photovoltaic string in which the full nominal voltage of the several serial photovoltaic modules or of the entire photovoltaic string (typically.> 500 volts ) is present, preferably exclusively, through metallic conductors, for example Metal cables, metal connectors and / or relays and at least not permanently

BE2017 / 5253 through semiconductor components. As a result, the power loss can advantageously be kept low, so that the line cut-off device can optionally be installed in existing housings without overheating.

Each parallel photovoltaic string preferably has such a string shutdown device in front of the central collection point. The string shutdown devices are cross-photovoltaic module, i.e. are each responsible for the entire photovoltaic string with several series-connected photovoltaic modules.

The string disconnection devices have a positive pole input and a negative pole input on the input side (i.e. on the string or photovoltaic module side) for connecting the positive pole or negative pole of the string line, and on the output side (i.e. on the collecting point side) a positive pole output and a negative pole output for connecting the positive pole or negative pole to a continuation of the string line to the central collection point of the photovoltaic strings or up to the DC input of the inverter. Accordingly, in particular the entire string voltage is present at the string shutdown device and / or the entire string current flows through the string shutdown device in order to be combined in parallel downstream with the currents of the other parallel photovoltaic strings at the central collecting point in the direction of the inverter. Thus, the positive pole outputs and the negative pole outputs of the parallel photovoltaic strings are connected to the positive pole or negative pole of the central collecting point or, via the central collecting point, to the positive pole and the negative pole of the DC input of the inverter. The

String shutdown device now provides an individual shutdown option for the associated photovoltaic string.

As has already been explained above, the present invention has particular advantages in combination with the reverse current protection according to DE 10 2016 117 049.

Thus, if the string shutdown device also acts as a reverse current protection device, this also prevents a cross current from becoming so large that the direction of current flow in the associated photovoltaic string is reversed, i.e. a negative current flows back into the associated photovoltaic string. In an advantageous manner, undesired reverse currents can be prevented, which could otherwise arise if the associated photovoltaic string should have a lower impedance than the inverter or corresponding pantograph downstream of the central collecting point. This can have a positive impact on the lifespan of the associated photovoltaic modules. Depending on

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Safety equipment of the photovoltaic system, the reverse current protection function can also increase the safety of the system, especially when switching off individual photovoltaic strings or the photovoltaic system, e.g. due to insufficient radiation, maintenance work or in the event of a hazard shutdown, in particular in which the reverse current protection function prevents the shutdown of the associated photovoltaic string from being prevented due to reverse current.

The string cut-off device is preferably installed in an electrically insulating housing which has a positive pole connection for the positive pole of the string line and a negative pole connection for the negative pole of the string line of the associated photovoltaic string at the string-side input. Furthermore, the line cut-off device preferably has a positive pole connection for the positive pole and a negative pole connection for the negative pole of the extension of the branch line, which leads to the central collecting point, at the output on the collecting point. The connections on the housing are preferably as photovoltaic connectors, e.g. trained in accordance with the applicant's SUNCLIX® system. The housing with the string shutdown device, which can be inserted with the connectors in the two lines of the string line of the associated photovoltaic module, can therefore form a separately pluggable unit in the form of a string shutdown box, which can also be used as a retrofit solution in existing string lines between the photovoltaic modules one photovoltaic string each and the central collection point or the common inverter can be inserted in order to retrofit an existing multistrand photovoltaic system.

The string shutdown device preferably contains a sensor connected to the control device for measuring an electrical parameter on the associated photovoltaic string. In response to the electrical characteristic measured with the sensor, the control device can switch the switch device, but possibly only if there is also user authorization. In particular, in response to the electrical characteristic measured with the sensor, the control device prevents the switch device and / or at least the relay, e.g. if the measured electrical parameter lies outside a safety condition for the first electrical parameter that is relevant for the restart.

The sensor is preferably a current sensor or a voltage sensor, which measures at least one of the following electrical parameters:

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Input voltage at the string-side input of the string cut-off device,

Output voltage at the collector-side or inverter-side output of the string shutdown device,

- string current of the associated photovoltaic string or through the string shutdown device or string box,

- negative current flow.

A negative current flow means that the current in the photovoltaic string flows through the string shutdown device counter to the flow direction of the current photovoltaically generated during operation. I.e. the current sensor is in particular designed to also be able to measure a negative current flow.

If, in addition to the user-controlled string shutdown, a reverse current protection function is also desired, the combined string shutdown and reverse current protection device opens the switch device in response to one or more of these electrical parameters measured with the sensor or sensors and interrupts the connection of the associated photovoltaic string to the parallel connection with the other photovoltaic strings and thus to the DC input of the inverter. The line cut-off and / or reverse current protection device therefore preferably contains a current sensor which can also measure negative currents and / or an input voltage sensor and / or an output voltage sensor.

In this way, it can advantageously be continuously and separately determined on each photovoltaic string in a simple manner whether there is a state of the associated photovoltaic string that lies outside the desired operating and safety parameters.

According to a preferred embodiment of the invention, the sensor is accordingly a current sensor which can measure the current flow, possibly also a negative current flow through the phase cut-off and reverse current protection device. The string shutdown and reverse current protection device can connect the associated photovoltaic string to the central collection point, i.e. to the parallel connection with the other photovoltaic strings and to the direct current input of the inverter, at least if the current in the associated photovoltaic string is negative and / or exceeds a predefined threshold value for the amount of the negative current. However, a negative current is not a necessary prerequisite for the disconnection. Depending on which operating and safety parameters are specified, the string shutdown and

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Reverse current protection device also carry out the interruption when the current is still positive but is below a predefined safety threshold value. This can e.g. then occur when the photovoltaic modules of the associated photovoltaic string are shaded considerably more than the photovoltaic modules of the other photovoltaic strings. In this case, the cross currents may not yet result in a negative total current flow in the associated photovoltaic string, but may reduce the current generated by the photovoltaic string from the associated photovoltaic string so far that the production operation of this associated photovoltaic string is no longer economically sensible, so that it is better to interrupt the connection of this associated photovoltaic string to the parallel connection with the other photovoltaic strings and to the common inverter. This can be particularly useful if the current measured by the string cut-off and reverse current protection device is still positive, but considerably below the maximum current of the photovoltaic string, e.g. is less than 10% of the maximum current of the photovoltaic string. In other words, the control device is preferably designed to switch the switch device automatically, or to interrupt the connection of the associated photovoltaic string to the parallel connection and to the inverter, if the condition occurs that the string current I becomes smaller than a predefined threshold value IO . The predefined threshold value IO can be selected between positive and considerably smaller than the maximum current of the associated photovoltaic string and a negative safety value for the current flow. Expressed mathematically, the switching condition can be defined as l <IO, where IO is selected from an interval [11,12], where 11 is a negative safety value at which the associated photovoltaic string could be damaged and I2 is a positive value below which a economic operation no longer makes sense.

In particular, the control device of the string shutdown and reverse current protection device also electrically connects the associated photovoltaic string to the parallel connection with the other photovoltaic strings and to the common inverter, if the operating and safety parameters permit this and the user release, e.g. in the form of a trigger signal, e.g. by a closed switch. For this purpose, the control device is connected to a sensor device for measuring at least one electrical parameter.

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According to a preferred embodiment, the sensor device comprises an input voltage sensor which measures the string-side input voltage at the string shutdown device and / or an output voltage sensor which measures the collector-side or inverter-side output voltage at the string shutdown device. In response to the measured string-side input voltage and / or the measured collector-side or inverter-side output voltage, the control device switches the associated photovoltaic string, whose connection to the central collecting point is interrupted, back to the central collecting point with the other parallel photovoltaic strings and thus electrically to the DC input of the inverter when the user approval is available.

According to a further preferred embodiment of the invention, the input voltage is compared with the output voltage and the control device switches in response to the comparison of the measured string-side input voltage and the measured collector-side or inverter-side output voltage switch device, in particular in that the associated photovoltaic k string, the connection thereof is interrupted to the central collection point, is switched on again to the other parallel photovoltaic strings and to the DC input of the inverter when the user release is available. The voltage comparison can ensure that the desired operating and safety parameters are fulfilled after the relevant photovoltaic string has been switched on again, e.g. that no negative current flows back into the associated photovoltaic k string or that the positive production current exceeds a minimum value by the associated photovoltaic k string being switched on again electrically only when the difference between output voltage U2 minus input voltage U1 is less than one predefined threshold U0. If U0 = 0, this means that the output voltage U2 is lower than the input voltage U1. There may be a certain tolerance here, in particular the effect can be exploited that the input voltage of the associated photovoltaic string, whose connection to the central collecting point is interrupted, is the open circuit voltage, whereas the output voltage, which is that of the other parallel photovoltaic Module generated voltage, already represents a load voltage, which is typically about 20% lower than the open circuit voltage because the inverter is already working. Accordingly, the controller can respond to the comparison of the open circuit voltage of the associated one

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Photovoltaic strings associated with the load voltage of the other photovoltaic strings

Connect the photovoltaic string, whose connection to the central collection point is interrupted, back to the central collection point with the other parallel photovoltaic strings and thus to the DC input of the inverter when the user approval has been given.

In addition to the voltage comparison, it can also be checked whether the voltage of the associated photovoltaic string exceeds a predefined threshold value U_min, e.g. to ensure that the associated photovoltaic string can generate sufficient power at this time.

The combined string shutdown and reverse current protection device accordingly preferably comprises a switch device which, in the closed state, electrically connects the associated photovoltaic string in parallel with the other photovoltaic strings and in the open state the current-carrying connection of the associated photovoltaic string to the central collection point or to the Inverter in the string line interrupts bidirectionally.

The switch device should be designed for a separation voltage of at least 500 volts, better at least 1000 volts and / or for a through current of at least 5 amps, better at least 10 amps. In particular, the total voltage of the associated photovoltaic string is to be interrupted or switched by the switch device and / or the entire production current of the associated photovoltaic string is to flow through the switch device in the production operation of the photovoltaic string.

The semiconductor switches and / or the relay which are preferably used for this purpose are preferably designed as normally open contacts. At first glance, this might appear to be disadvantageous, since electrical power is required to maintain the on state.

However, this is accepted in order to achieve the associated security, namely that the connection of the associated photovoltaic string is interrupted in the normal state of the switch device to the parallel connection with the other photovoltaic strings and to the DC input of the inverter.

Advantageously, semiconductor switches, e.g. MOS-FETs are used which have an RDS-On (Resistance-Drain-Source-On, also known as switch-on resistance in German) of e.g. have at least 50 mOhm, possibly even several 100 mOhm or more. Although this creates a relatively large loss line of possibly one watt, a few watts

BE2017 / 5253 or more, which is particularly acceptable due to the relief provided by the parallel relay.

The presently disclosed invention can be used particularly advantageously in photovoltaic systems in which the series-connected photovoltaic modules in at least one of the photovoltaic strings, preferably in all photovoltaic strings, each have protective circuits by means of which the photovoltaic modules are individually isolated from the associated one String can be switched off, and wherein the protective circuits of the individual photovoltaic modules short-circuit the output of the respective photovoltaic module at the connection points for the string line in order to generate a low-resistance bypass for the respective photovoltaic module. Such protective circuits for the photovoltaic modules are described in more detail in WO2013 / 026539 A1, to which reference is hereby made and which in this regard is hereby incorporated by reference. Furthermore, the presently disclosed invention can be used particularly advantageously in photovoltaic systems in which the associated photovoltaic string has a start circuit which is designed to reactivate such or other protective circuits of the individual photovoltaic modules of the associated photovoltaic string. Such starting circuits for the photovoltaic strings are described in more detail in WO2014 / 122325 A1, to which reference is hereby made and which in this regard is hereby incorporated by reference.

Such a start circuit for starting the associated photovoltaic string and the string shutdown device for the associated photovoltaic string can preferably be accommodated in a common housing, so that a string box with a combined start and individual string shutdown function for the associated photovoltaic string is created. The strand box is provided with positive pole and negative pole connections at the input and positive pole and negative pole connections at the output of the strand box between the series of photovoltaic modules of the associated photovoltaic string and the central assembly point with the other photovoltaic strings in the associated photovoltaic String switched where it can perform both functions - string shutdown and starting the associated photovoltaic string and possibly reverse current protection for the same photovoltaic string. In this way, superfluous components, in particular plug connections, can be saved, which can have a positive effect on the costs, service life and loss of the photovoltaic system. The power loss of the string shutdown device is so low in production, especially when the relay is closed, that the thermal load is acceptable.

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Each photovoltaic string of the parallel connection is preferably at the central one

Collection point or the DC input of the same inverter with the described

String shut-off device or string box equipped across photovoltaic modules.

The invention also relates to a method for user-controlled or user-triggered switching off and (on) switching on of a user-selected individual photovoltaic string of a multi-string photovoltaic system as described above from or to the central collection point or to the DC input of the inverter. The process includes the following steps:

Targeted triggering of the string shutdown device of the associated photovoltaic string by the user in order to switch off the associated photovoltaic string from the central collection point or to separate the current-carrying connection to the central collection point. In particular, at least one other photovoltaic string remains connected to the central collection point and continues to feed in electricity via the central collection point, so that the multistrand photovoltaic system basically remains productive.

Targeted triggering of the string shutdown device of the associated photovoltaic string by the user in order to switch the associated photovoltaic string back on to the central collection point or to connect it to the central collection point in a current-carrying manner, in particular if further test conditions with regard to electrical parameters are met.

The invention further relates to the string shutdown device for a photovoltaic string of a multistrand photovoltaic system for the user-controlled targeted disconnection of the associated photovoltaic k string from other photovoltaic k strings of the multistrand photovoltaic system connected in parallel to the central collection point.

The string shutdown device comprises a switch device which, in the closed state, connects the associated photovoltaic string in a current-carrying manner in parallel with the other photovoltaic strings via a central collecting point and in the open state interrupts the current-carrying connection of the associated photovoltaic string to the central collecting point.

The string shutdown device further comprises a control device which is designed to switch the switch device from the closed state into the open state in response to a control signal triggered by a user, in order to separate the associated photovoltaic string from the central collecting point in a user-triggered manner.

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The line switch-off device comprises in particular a parallel connection from a

Semiconductor switch back-to-back circuit and a relay, i.e. an electromechanical

Counter.

It is apparent to the person skilled in the art that the invention can be used particularly advantageously for photovoltaic systems, but in principle can also be used for other DC generators, in particular if these have a parallel connection at a central collection point or at a common inverter. These should not be excluded.

The invention is explained in more detail below on the basis of exemplary embodiments and with reference to the figures, the same and similar elements being partially provided with the same reference numerals and the features of the different

Embodiments can be combined.

Brief description of the figures

Show it:

1 is a block diagram of a photovoltaic system with parallel photovoltaic strings,

2 shows a block diagram of a protective circuit for a photovoltaic module,

Fig. 3 is a block diagram of a start box with strand shutdown device and

Reverse current protection function,

Fig. 4 is a more detailed block diagram of the switch device S1, and

Fig. 5 is a flowchart for starting, testing and switching off the associated

Photovoltaic string.

Detailed description of the invention

With reference to FIG. 1, the multi-strand photovoltaic system 1 comprises a plurality of photovoltaic strings connected in parallel, of which only two photovoltaic strands 10, 10 'are shown for the sake of simplicity.

Each photovoltaic string comprises a plurality of photovoltaic modules or panels 12, 12 ', each of which is equipped with a protective circuit 14, 14', e.g. as described in WO 2013/026539 A1. The protective circuits 14, 14 'are each assigned to a photovoltaic module 12, 12' and the respective string line 16, 16 'leads through the protective circuit 14, 14' associated with the photovoltaic string 10, 10 'with two poles.

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With reference to FIG. 2, each protective circuit 14, 14 ′ contains a short-circuit switch S3 for short-circuiting the associated photovoltaic module 12, 12 ′ as well as a serial isolating switch S4, with which the associated photovoltaic module 12, 12 ′ from the photovoltaic string 10 , 10 'can be separated. In the event of shading or failure of a photovoltaic module 12, 12 ', the short-circuit switch S3 closes and the serial isolating switch S4 opens, so that the respective photovoltaic module 12, 12' is disconnected from the string, runs idle and the photovoltaic string 10, 10 'nevertheless remains closed, so that the photovoltaically generated current of the other photovoltaic modules of this photovoltaic string 10, 10 'can continue to flow through the string line 16, 16', which is also closed in this protected state. For further details of the exemplary protective circuit 14, 14 ', reference is made to WO 2013/026539, which in this regard is hereby made the subject of the present disclosure by reference.

Referring back to FIG. 1, a start box 20, 20 'is inserted into each line 10, 10', through which both line lines 16, 16 'pass. On the inverter side of the starter boxes 20, 20 ', extensions 17, 17' of the string lines 16, 16 'at the central collection point 22a, 22b, or their plus and minus poles, are connected in parallel in order to generate the photovoltaically generated power of the plurality of photovoltaic strands 10, 10 'etc. connected in parallel into the DC input 24a, 24b of the common inverter 26. At the alternating current output 28 of the inverter 26, the alternating current is made available for feeding into a supply network.

In this example, the start boxes 20, 20 'are supplied by an external 24-volt power supply 32 in order to carry out the desired switching operations. However, the supply can also be provided by a start photovoltaic module, which has no protective circuit 14, 14 'and thus automatically supplies the respective photovoltaic string 10, 10' and thus the associated start box 20, 20 'with electrical power when the light falls . For further details, reference is made to WO 2014/122325 A1, which in this regard is hereby made the subject of the present disclosure by reference.

Referring now to FIG. 3, a photovoltaic string 10 from the plurality of parallel photovoltaic strings is shown. All other photovoltaic strings 10, 10 'etc. connected in parallel have the same structure, so that a corresponding repetition can be dispensed with in this regard.

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The photovoltaic modules 12 with a connected protective circuit 14, which is not shown separately in FIG. 3 for the sake of simplicity, form the photovoltaic string 10 in series connection. The positive pole 16a and the negative pole 16b of the string line 16 are connected to a positive pole input 34a and a negative pole input 34b of the start box 20 is connected in order to be fed into the start box 20. Corresponding extensions 17 of the strand line 16 to the positive pole 24a or to the negative pole 24b of the direct current input 24 of the inverter 26 are connected to a positive pole output 36a or a negative pole output 36b. The current photovoltaically generated by the photovoltaic modules 12 of the photovoltaic string 10 therefore flows through the start box 20 during production operation. At the inputs and outputs 34a, 34b; 36a, 36b, the module-side and assembly-side sections 16 of the strand line are preferably connected with plug connectors (not shown). The second photovoltaic string 10 'connected in parallel or further parallel photovoltaic strings are symbolized by the dashed lines which lead to the two poles of the central collecting point 22a, 22b.

The start box 20 now contains a line cut-off device 40 which is integrated in the housing 21 of the start box. The string shutdown device 40 comprises a switch device S1, which is connected in series in the photovoltaic string 10, in this example in a branch of the string line (in this example, the positive pole). With the serial switch device S1, the current-carrying connection of the associated photovoltaic string 10 to the inverter 26 can be interrupted in a user-controlled manner. A control device 42 in the form of a microcontroller controls the serial isolating switch device S1 and monitors a current sensor 44, an input voltage sensor 46, an output voltage sensor 48 and a trigger signal sensor 49 in order to obtain electrical parameters.

The input voltage sensor 46 is connected in parallel to the input connections 34a, 34b of the start box 20 in order to measure the input voltage U1, which is the string voltage of the associated photovoltaic string 10. The output voltage sensor 48 is connected in parallel to the output connections 36a, 36b of the start box 20 in order to measure the output voltage U2, which is the voltage that is present at the inverter 26, i.e. which is the voltage that is applied to the inverter 26 by the parallel connection of all other photovoltaic strings. In production operation, the current sensor 44 measures the string current which, when the photovoltaic string 10 produces electricity in the normal direction, which is referred to here as positive, through the string line 16

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Start box 20, the continuation of the string line 17 and the inverter 26 flows in order to be fed into the inverter with the correct polarity. However, the current sensor 44 is preferably also designed to detect a current flow in the reverse direction, i.e. to measure a current which is negative with respect to the normal current direction of production of the photovoltaic string 10 (that is to say with the opposite polarity to the direct current inputs 24a, 24b of the inverter). Alternatively, however, two separate current sensors, one for the positive current flow and one for the negative current flow, can also be provided (not shown). The string shutdown device 40 is accordingly designed to measure positive and / or negative current flow. In this example, the trigger signal sensor 49 is a voltage sensor, which measures the operating voltage at a starting current transformer 33. The trigger signal is monitored by the control device 42 in order to trigger the string shutdown. The trigger signal can, however, also be another trigger signal which triggers the control device 42 to trigger the string shutdown.

The start box 20 also contains a short-circuit switch S2, which is also controlled by the control device 42 and can impress a start current in the associated photovoltaic string 10 in order to switch the protective circuits 14, e.g. to start after sunrise. At night, during maintenance or in the event of a fault, the protective circuits 14 are in the safety state, as a result of which each photovoltaic module 12 is separated from the associated string 10 and the string line 16 is short-circuited. For this purpose, switch S3 is closed and switch S4 is open. In the associated basic position of the start box 20 or the line switch-off device 40, the serial switch device S1 and the

Short-circuit switch S2 both open and are in their normal state (Normal Open). A main function of the serial switch device S1 is to interrupt the current-carrying connection of the associated photovoltaic string 10 to the inverter 26 and to the further parallel photovoltaic strings. The short-circuit switch S2 is used to trigger string-side short-circuits in the associated photovoltaic string 10 and the photovoltaic modules 12 of the associated photovoltaic string 10 via an impressed starting current, which in this example is generated by the external power supply 32 and the internal starting current transformer 33, to activate. After sending the start pulse, the string voltage U1 and the inverter voltage U2 are measured and compared in order to electrically switch the associated photovoltaic string to the parallel connection and the inverter 26 in response to the voltage comparison, if one

BE2017 / 5253 corresponding user approval is available. The serial switch device S1 is closed in response to a comparison of the phase voltage U1 and the inverter voltage U2, i.e. the switching condition for the connection process of the serial switch device S1 depends on a comparison of the phase voltage U1 and the inverter voltage U2. The serial switch device S1 is closed in particular only when the string voltage U1 of the associated photovoltaic string 10 is either greater than the inverter voltage U2 or only by a predetermined threshold value U0 (slightly) less than the inverter voltage U2. In other words, a switching condition for the serial switch device S1 for the electrical connection of the photovoltaic string 10 to the parallel connection and to the inverter 26: U1> = U2-U0, where U0 is a predefined value for the maximum permissible voltage difference for the safe connection of the associated photovoltaic string 10 to the inverter. The predefined switching value U0 stored in the microcontroller is therefore (significantly) smaller than the maximum possible voltage of the associated photovoltaic string 10. Only when such a switching condition, which depends on the electrical parameters of the associated photovoltaic string 10 and the other photovoltaic strings, is fulfilled , the control device 42 controls the serial switch device S1 in such a way that the switch device S1 is closed and thus connects the associated photovoltaic string 10 to the inverter 26. A system start of the associated photovoltaic string 10 is thus possible without the risk of undesired reverse currents occurring.

In order to detect undesirable reverse currents from the other photovoltaic strings in the associated photovoltaic string 10 in production operation, in which the serial switch device S1 is closed, the current flow through the backflow protection circuit is monitored during production operation. For this purpose, a current measurement is carried out with the current sensor 44. The current sensor 44 accordingly carries out permanent monitoring of the phase current, including the sign of the phase current, that is to say as to whether the phase current is negative. If the string current should become negative or a state is approached, the microcontroller 42 controls the serial switch device S1 so that it opens and the current-carrying connection of the photovoltaic string 10 to the central collection point 22a, 22b and to the inverter 26 interrupts.

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So that all start boxes clean the associated photovoltaic string 10

Disconnect the inverter 26, when the entire photovoltaic system 1 shuts down, the serial switch devices S1 of all string shutdown devices 40 of all photovoltaic strings are also opened as soon as the inverter voltage U2 is below a predefined one

Minimum voltage U_min, where U_min e.g. can be in the range of about 30 volts.

4, the switch device S1 comprises a parallel connection of a back-to-back circuit 50 of two semiconductor switches, in this example two MOS-FETs 52, and a relay 54. The semiconductor switches and / or the relay are for the full nominal String voltage and the full nominal string current of the associated photovoltaic string 10 designed, which typically up to 1000 volts or even 1500 volts as well Can be 10A. Such MOS-FETs 52, however, have a typical one

Starting resistance, the so-called resistance drain source on or RDS-on for short, from several 100 mOhm. This results in a power loss in the range of a few watts in a typical photovoltaic string 10 on the MOS-FETs 52. Since such a power loss is primarily for installation in existing housings, e.g. In the present start box 20, which is undesirable, the relay 54 relieves the back-to-back circuit 50 from the two MOS-FETs 52 in continuous operation. I.e. the switch-on process is first carried out by the back-to-back circuit from the two MOS-FETs 52 and when the associated photovoltaic string 10 has been in production operation for a certain minimum time, the parallel relay 54 is closed in order to relieve the MOS-FETs 52. This on the one hand avoids the permanent generation of high power loss at the MOS-FETs 52 and on the other hand the relay 54 is protected.

With such a back-to-back circuit 50 comprising two semiconductor switches, the desired individual strand cut-off can now also take place by the string shutdown device 40 being user-controlled by the switch device S1, i.e. Both the back-to-back circuit 50 and the relay 54 open and thus select and switch off the associated photovoltaic string 10 in a user-controlled manner. For this purpose, the current-carrying connection between the associated photovoltaic string 10 or the DC generator and the central collection point 22a, 22b or the inverter 26 is bidirectionally separated by means of the switch device S1, i.e. a possible current flow in both directions is interrupted. For this purpose, the two MOS-FETs 52, which are installed in the back-to-back circuit 50, are used in the semiconductor switching part of the switch device S1.

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Because the photovoltaic string 10 can be separated for both directions of current flow, each photovoltaic string can be safely switched individually. The

Switch device S1 disconnects the associated photovoltaic string 10 or the associated DC generator by means of the back-to-back circuit 50 from two MOSFETs 52 against a current flow in both directions.

In this example, the internal firmware of the line switch-off device 40 or of the start box 20 is set up in such a way that the supply input 35 of the start current transformer 33 is used for the trigger signal in order to specifically trigger the line switch-off device 40 in a user-triggered manner. When the user opens the switch S5 on the external power supply 32, the control device 42 triggers the switch-off process in response to the measurement of the missing supply voltage U3. For this purpose, a trigger signal sensor 49 in the form of a voltage sensor is installed in the start box 20, which measures the supply voltage U3 at the start current transformer 33. If the supply voltage U3 at the starting current transformer 33 falls below a predefined threshold value, which here is determined by the test condition “U ext. Start = Off ¹ , this represents, for example, the trigger signal for the control device 42, whereupon the control device 42 automatically opens the switch device S1. In other words, the user only needs to open the switch S5 on the start box 20 in order to trigger the strand shutdown in a user-controlled manner. In the present example, relay 54 is first opened for string shutdown and then back-to-back circuit 50 is opened after a time delay in order to separate the associated photovoltaic string 10 from central collection point 22a, 22b. Due to the separation and the associated interruption of the current flow from the associated photovoltaic string 10, the protective circuits 14 of the photovoltaic modules 12 in turn automatically switch to the safety state in which they are short-circuited and no longer apply voltage to the photovoltaic string 10. The associated photovoltaic string 10 is thus separated from the central collection point 22a, 22b and is safely switched off.

5, the start and shutdown sequence of the string shutdown device 40 is as follows, for example.

At system start at 102, switch device S1 is open in step 104. A query in step 106 checks whether the input voltage U1 falls below a minimum voltage U_min1. If the condition U1 <U_min1, where in the present example

U_min1 = 30 V DC, is fulfilled and the user is enabled to start (U ext. Start = on),

BE2017 / 5253 in this example the condition that the switch S5 is closed and thus the

The supply voltage at the start current transformer 33 is present (U ext. Start = on)

Step 108 with the short-circuit switch S2 triggered the start pulses to the associated

Start photovoltaic string 10. The serial switch device S1 remains open and the loop goes back to step 104.

If the associated photovoltaic string 10 has now started as a result of the start pulses, in that the associated protective circuits 14 have electrically connected the associated photovoltaic modules 12 to the photovoltaic string 10, the string voltage U1 should be significantly above the predefined minimum value U_min1 - provided there is no error is present - and the associated photovoltaic string 10 is not totally shaded. After the condition U1 <U_min1 is no longer fulfilled in normal irradiation and without interference in step 106 and the user is still enabled to start (U ext. Start = on), a further query is made in step 110 as to whether the input voltage U1 of the associated photovoltaic string 10 is greater than or equal to the output voltage U2 of the associated photovoltaic string 10 minus a predefined threshold value U0 (U1> = U2-U0), wherein U0 in this example is 20 V DC, but could also be zero. This condition should preferably be met for a predefined minimum time tO, which in this case is tO = 1s. Furthermore, it is checked again whether the voltage U1 is greater than or equal to a minimum value U_min2, in order to ensure that the associated photovoltaic string 10 is still electrically connected, U_min2 = 150 V DC in this example. Furthermore, it is checked again whether the user release (U ext. Start = on) is present. If at least one of these three test conditions is not met in query step 110, the loop goes back to step 104 and query 106.

If, however, all of these three test conditions in query 110 are met, it is checked in step 111 whether the phase current I is greater than a predefined threshold value l_min, l_min being 500 mA (in the positive direction) in this example. If this test condition is not fulfilled, the microcontroller 42 controls the serial switch device S1 in step 112a such that only the back-to-back circuit 50 closes. If this test condition I> I_min is met, the microcontroller 42 controls the serial switch device S1 in step 112b in such a way that the back-to-back circuit 50 and the relay 54 close. In both cases 112a, 112b, the associated photovoltaic string 10 is connected to the central collection point 22a, 22b or the inverter 26, and the associated photovoltaic string 10 feeds electricity

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Power into the central collection point 22a, 22b or the inverter 26, the switch device S1, however, only after the relay 54 has been closed in step 112b, i.e. in the state for continuous production operation, works particularly low loss. Because the back-to-back circuit 50 alone is already closed in step 112a, this routine in step 112b causes the relay 54 to close at different times only after a delay after the semiconductor switch back-to-back circuit 50 has closed in step 112a. Through this routine, the relay 54 only takes over the current flow from I> 500 mA and only needs to switch a low voltage of typically 1 volt.

During production operation, a test step 114 then continuously or regularly checks whether a) there is a negative current greater than or equal to a predefined minimum value LReverse, specifically over a predefined minimum time t1 (t1 = 1s), or b) whether the input voltage U1 falls below a predefined minimum value U_min3 (here U1_min3 = 150V) or c) whether the user release is not available (U ext. Start = Off). The minimum value LReverse for the negative current is typically in the milliampere range. In this example, the corresponding test condition is therefore whether there is a negative current of at least 20 mA (l_Reverse <= - 20mA). As long as all three test results a), b), c) are negative, i.e. Logically a) OR b) OR c) = NO, the switch device S1 is kept closed.

A further test step 116 is then carried out by querying in an error monitor whether the temperature is <130 ° C. and whether the differential voltage between U1 and U2 is greater than 2V. If this error check is also negative, the loop to test step 111 is closed. Steps 111-116 accordingly form a permanent or continuous monitoring circuit for the associated photovoltaic string 10 to ensure that no undesired values of the monitored electrical parameters occur even in production operation.

If the query in step 114 shows that one of the three test conditions mentioned is positive, i.e. logical a) OR b) OR c) = YES, e.g. if there is an undesirably high negative reverse current because e.g. the associated photovoltaic string 10 is shaded considerably more than the other photovoltaic strings, or because the associated photovoltaic string 10 has lost string voltage to such an extent that the threshold condition U1 <U_min3 is met, or because the user-controlled shutdown request is present by the user pressing the switch S5 has opened (U ext. Start = Off), the loop goes back to step 104, ie the switch device S1 opens as described above. Preferably the

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Switch device S1 or both the MOSFETs 52 and the relay 54 are designed as normally open contacts, so that S1 automatically falls into the open state if it is not kept in the closed state (loop 111-116) by the control device 42 .

Loop 111-116 therefore represents the production operation of the associated photovoltaic string 10.

The user can therefore in step 114 by triggering the condition U ext. Start = Off, here by opening switch S5, intervene in loop 111-116 as desired to disconnect the current-carrying connection of the associated photovoltaic string 10 in a user-controlled manner from the central collection point or to switch off the associated photovoltaic string 10 in a user-controlled manner. If so user-controlled by triggering the condition U ext. Start = Off the query in step 114 is set to "yes", the loop 111-116 is interrupted and the path of the test / control routine goes to step 104, in which the switch device S1 opens, even if all the electrical parameters meet predefined test conditions. The user thus has the possibility of triggering or triggering the shutdown of the associated photovoltaic string 10 in a user-controlled manner at his own discretion.

If the error monitoring in step 116 gives a positive result, i.e. If one of the two error conditions mentioned applies, the switch device S1 is opened in a step 118 as in step 114 and the signaling output is additionally toggled, which emits an error message for the user. The cycle is then ended with step 120. This typically signals a malfunction.

With the present invention, it is possible to switch off in a user-controlled manner any photovoltaic string 10 that is equipped with such a string shutdown device 40 or that is in production operation. This can be done by means of the switch device S1 from a parallel connection of a MOSFET back-to-back circuit 50 and a relay 54 and a corresponding control e.g. 5 can be achieved. The switch device S1 installed in the start box is able to separate the photovoltaic string and prevent the current flow. This causes the protective circuits 14 (e.g. Phoenixcontact SCK-RSD-100) installed on the photovoltaic modules 12 in the present example also to be switched off. In other words, in the present example, the protective circuits 14 installed on the photovoltaic modules 12 are then automatically deactivated and the individual photovoltaic modules 12 are switched off, so that the

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2017/5253 entire photovoltaic string 10 is not only electrically separated from the central collection point 22a, 22b, but also no longer carries a dangerous voltage.

The system is advantageously manufacturer-independent. It can too

Switch-off units from other manufacturers can be separated from the multi-strand network. The

The shutdown process is initiated by the microcontroller installed in the strand shutdown device 40 or actively triggered by the user or customer via the external input 35.

To start the photovoltaic string 10, start pulses are sent via the string line 16 to the protective circuits 14 of the photovoltaic modules 12 of the associated photovoltaic string 10 (step 108) in order to reactivate the unloaded photovoltaic string 10, but not yet immediately to connect the central collection point 22a, 22b. The test routine is then carried out with steps 110-116 according to FIG. 5.

In summary, the present invention enables a single line shutdown via a higher-level control unit and represents an advantageous function for the customer to not only in an emergency, but also e.g. Switch off individual photovoltaic strings for maintenance purposes.

It is apparent to the person skilled in the art that the above-described embodiments are to be understood as examples and the invention is not restricted to them, but can be varied in many ways without leaving the scope of the claims. It can also be seen that the features regardless of whether they are in the

Description, the claims, the figures or otherwise disclosed also individually define essential components of the invention, even if they are described together with other features.

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Claims (15)

Claims: 1. Multistrand photovoltaic system (1) with string shutdown, comprising: two or more photovoltaic strings (10, 10j, which are each formed by series-connected photovoltaic modules (12, 12j, a central collection point (22a, 22b) at which the photovoltaic strings (10, 10j by means of string lines (16, 17) are connected in parallel in order to establish a current-carrying connection between the photovoltaic strings (10, 10j and the central collection point (22a, 22b)), at least one of the photovoltaic strands (10, 10j having a string shutdown device (40) by means of which the current-carrying connection between the at least one photovoltaic string (10, 10j and the central collection point can be disconnected in a user-controlled manner in order to switch off the at least one photovoltaic string (10, 10j. 2. Multistrand photovoltaic system (1) according to claim 1, wherein the string shutdown device (40) has a switch device (S1) in the string line (16, 17) of the at least one photovoltaic string and a control device (42) for controlling the switch device ( S1), wherein the switch device (S1) defines a closed and an open state and in the closed state conducts photovoltaically generated electricity from the at least one photovoltaic line (10, 10j) to the central collection point (22a, 22b) and in the open state Condition the passage of photovoltaically generated current from the at least one photovoltaic string (10, 10 j) is interrupted, and the control device (42) is designed to open the switch device (S1) in a user-controlled manner in response to a user input. 3. M ultistrang-photovoltaic system (1) according to claim 2, wherein the control device (42) is designed to receive an external string shutdown trigger signal (U ext. Start = Off) and in response to the string shutdown trigger signal (U ext. Start = Off) to switch off the at least one photovoltaic string (10, 10j) by the control device (42) opening the switch device (S1) BE2017 / 5253 and thus separates the at least one photovoltaic string (10, 10j at least on one side from the central collection point (22a, 22b). 4. Multi-strand photovoltaic system (1) according to claim 2 or 3, wherein the switch device (S1) is designed to interrupt the current flow in both directions in the open state. 5. M ultistrang-photovoltaic system (1) according to one of the preceding claims, wherein the string shutdown device (40) is a back-to-back circuit (50) comprising two semiconductor switches, in particular a back-to-back circuit two MOSFET transistors (52). 6. M ultistrang-photovoltaic system (1) according to any one of the preceding claims, wherein the string shutdown device (40) comprises a relay (54). 7. M ultistrang-photovoltaic system (1) according to one of the preceding claims, wherein the string cut-off device (40) is a parallel connection of a relay (54) and a back-to-back circuit (50) of two semiconductor switches, in particular a parallel circuit comprising a relay (54) and a back-to-back circuit (50) comprising two MOSFET transistors (52). 8. M ultistrang-photovoltaic system (1) according to any one of claims 6-7, wherein the string cut-off device (40) is designed to switch off the associated photovoltaic string (10, 10 j from the central collection point (22 a , 22b) first open the relay (54) and only after a time delay thereafter open the semiconductor switches, in particular the MOSFET transistors (52). 9. M ultistrang photovoltaic system (1) according to one of the preceding claims, wherein the string shutdown device (40) is designed to carry out a test routine (102120) before switching on the associated photovoltaic string (10, 10 j), in the test routine (102-120) to test at least one electrical parameter (U1, U2,1) of the associated photovoltaic string (10,10j) and if it is complied with BE2017 / 5253 of a predefined threshold value for the at least one electrical parameter to switch on the at least one photovoltaic string (10, 10j if a user release is available. 10. Multi-strand photovoltaic system (1) according to any one of claims 6-9, wherein the string shutdown device (40) is designed to initially connect the associated photovoltaic string (10, 10j to the central collection point (22a, 22b) to close the semiconductor switches, in particular the MOSFET transistors (52), and to close the relay (54) only after a time delay. 11. Multi-strand photovoltaic system (1) according to claim 10, wherein the strand cut-off device (40) is designed to measure the photovoltaically generated current flow through the associated strand line (16, 17) and only then to close the relay (54), when the photovoltaically generated current (I) flowing through the string line (16, 17) exceeds a predefined threshold value (I_min). 12. M ultistrang-photovoltaic system (1) according to one of the preceding claims, wherein the string shutdown device (40) has a control device (42) and a control device (42) connected to the sensor device (46,48) for measuring at least one electrical Contains parameter (U1, U2) on the associated photovoltaic string (10, 10j), the control device (42) being designed to respond to the at least one electrical parameter (U1, U2) measured with the sensor device (46, 48) To turn on the photovoltaic string (10, 10jan) electrically the central collection point (22a, b) when a user release is present, the sensor device in particular comprising: an input voltage sensor (46), which measures the string-side input voltage (U1) at the string cut-off device (40) and / or an output voltage sensor (48), which measures the collecting point-side output voltage (U2) at the string cut-off device (40), and wherein the control device (42 ) is designed in response to the measured string-side input voltage (U1) and / or to the measured BE2017 / 5253 output voltage (U2) on the collecting point and the associated photovoltaic string (10, 10jan to electrically switch on the central collection point (22a, b) if one User approval exists. 13. Multi-strand photovoltaic system (1), in particular according to one of the preceding claims, comprising: two or more photovoltaic strings (10, 10j, which are each formed by series-connected photovoltaic modules (12, 12j, a central collection point (22a, 22b) at which the photovoltaic strings (10, 10j by means of string lines (16, 17) are connected in parallel in order to establish a current-carrying connection between the photovoltaic strings (10, 10j and the central collection point (22a, 22b), at least one of the photovoltaic strings (10, 10j having a string shutdown device (40) which is connected in parallel in the string line (16, 17) from a semiconductor switch back-to-back circuit (50) and a relay (54). 14. A method for the user-controlled switching off and on again of a selected photovoltaic string (10, 10j of a multistrand photovoltaic system (1), in particular according to one of the preceding claims, of other photovoltaic cables connected in parallel to a central collecting point (22a, 22b). Strands (10.10 j of the multi-strand photovoltaic system (1), comprising the following steps: targeted triggering (U ext. Start = Off) of a string shutdown device (40) of the associated photovoltaic string (10,10j by a user in order to shutdown the associated photovoltaic string (10,10j from the central collection point (22a, 22b), targeted triggering ( U ext. Start = On) of the string shutdown device (40) of the associated photovoltaic string (10,10j by the user in order to switch the associated photovoltaic string (10,10j back on to the central collection point (22a, 22b), possibly in Response to the fulfillment of further test conditions. 15. String shutdown device (40) for a photovoltaic string (10, 10 j of a multi-string photovoltaic system (1), in particular according to one of the preceding claims, for 2017/5253 BE2017 / 5253 user-controlled, targeted disconnection of the associated photovoltaic string (10, 10 ') from other photovoltaic strings (10, 10') of the multistrand photovoltaic system (1) connected in parallel to a central collection point (22a, 22b) : a switch device (S1) which, in the closed state, connects the 5 associated photovoltaic strings (10, 10 ') in a current-carrying manner in parallel with the other photovoltaic strings (10, 10') via the central collecting point (22a, 22b) and in the open state the current-carrying connection of the associated photovoltaic string (10, 10 ') to the central collection point (22a, 22b), a control device (42), the control device (42) being designed 10 in response to a control signal triggered by a user (U ext. Start = Off) (S1) to switch from the closed state to the open state in order to separate the associated photovoltaic string (10, 10 ') from the central collection point (22a, 22b) in a user-controlled manner.