DE102017108507A1 - Photovoltaic system, protection circuit and method for self-shutdown of a photovoltaic string - Google Patents

Abstract

The invention relates to a photovoltaic system (1) with a switching device (38) for switching on and off at least one photovoltaic string (10), a safety circuit for autonomous or automated switching off a portion of the photovoltaic system or at least one photovoltaic string (10) and a method for autonomous or automated shutdown of the part of the photovoltaic system or the at least one photovoltaic string (10) of the photovoltaic system (1). The photovoltaic system (1) comprises: at least one photovoltaic string (10), wherein the at least one photovoltaic string is formed by photovoltaic modules (12), which are connected in series with one another by means of a string line and thus a string voltage (U1) generate a sensor device (46) for measuring an electrical parameter of the photovoltaic string (10), in particular the string voltage (U1), a switching device (38) which is incorporated in the strand line to at least a portion of the photovoltaic system (1 ) or the at least one photovoltaic string with the switching device (38) on and off, a control device (42) which is designed to compare the electrical characteristic with a predefined threshold value, in particular a threshold voltage, and in response to the comparison Output signal to the switching device (38), so that with the switching device (38) of the at least one part of the photovoltaic system or the at least one photovoltaic string can be turned off.

Description

Field of the invention

The invention relates to a photovoltaic system with a switching device for switching on and off of at least one photovoltaic string in response to the specification by a control device and a method for autonomously switching off at least a portion of the photovoltaic system or at least one photovoltaic string of photovoltaic Investment.

Background of the invention

A photovoltaic system typically includes a plurality of photovoltaic modules connected in series, sometimes called "strings", in series to achieve a nominal photovoltaic generator DC voltage of typically currently up to 1000 volts or even 1500 volts. Further, depending on the number of interconnected photovoltaic modules and their individual voltage in turn, if necessary, several of the photovoltaic strings connected in parallel, of which each photovoltaic string can produce, for example, a nominal current of 10A. When multiple strings are connected in parallel, this is also referred to as multistream or multi-string interconnection.

Due to the high voltage and the high currents in the DC part of the photovoltaic system or the photovoltaic generator, there is maintenance or incidents such. in the event of a fire, the risk of people being exposed to life-threatening tensions.

In addition, the system voltage generated by a photovoltaic system or the output from each photovoltaic module module voltage depends on different environmental conditions such as temperature in particular. The module voltage is regularly subject to a temperature gradient, the module voltage increases with decreasing temperature. A photovoltaic system is therefore typically designed for the most adverse environmental conditions that may possibly occur at the installation site, so that the photovoltaic system in favorable conditions, i. a high level of solar radiation with then warm photovoltaic modules, typically working away from their optimal working conditions to safely exclude any overvoltages.

Finally, it must be taken into account regularly in the plant construction of photovoltaic systems that errors can already occur in the design of the photovoltaic system or in the interconnection of the photovoltaic modules, whereby overvoltages in individual strands of the photovoltaic system can be caused For the above reasons, can also pose a threat and, for example, can lead to electric shock or fire.

Photovoltaic module protection circuits have been developed with which the photovoltaic modules can be switched off individually (cf. WO2013 / 026539 A1 and the product SCK-RSD-100 of the Applicant). Furthermore, starting boxes were developed with which such "intelligent" photovoltaic modules can be reactivated (cf. WO2014 / 122325 A1 as well as the products SCK-RSD-400 and SCK-RSD-600 of the Applicant).

In the DE 10 2016 117 049 (not prepublished) is further described a reverse current protection circuit, by means of which it is possible to separate a strand from the central collection point to prevent cross-currents. The objective of the DE 10 2016 117 049 it is, by means of the reverse current protection circuit automatically prevent current flow against the flow direction of the photovoltaic generated in the respective strand current from the other photovoltaic strands (cross-flow or return current).

In another German patent application of the same Applicant a Strandabschaltvorrichtung is described for single strand shutdown in a multi-strand photovoltaic system.

The present invention is based on the aforementioned inventions, which is why the disclosure of the DE 10 2016 117 049 and other filed patent applications (Attorney Docket No. 16PH 0346DEP and 16PH 0439DEP) are hereby incorporated by reference.

Furthermore, the present invention is based on the recognition that, for example, to electrically disconnect a photovoltaic string from a composite of a parallel circuit of strings in a multi-strand photovoltaic system, a suitable DC disconnector is required.

Although a photovoltaic system typically has a DC main circuit breaker in the so-called generator junction box, it is not possible to isolate the area in front of the generator junction box, for example in the case of damage caused by fire, water, hail etc. on the solar panels or on the connection lines. Furthermore, such DC main circuit breakers in the generator junction box are typically manually operated, so that higher-level remote control is typically not possible. In addition, such hand-operated DC main circuit breaker are large in size and cost-intensive and also not switchable quickly. There are also motorized emergency switch known, but these are also space and cost intensive. A selective activation of individual photovoltaic strings or even parts of a photovoltaic string is by the way not possible.

Nonetheless, in switching operations within a photovoltaic generator, typically a combination of high DC string voltage and high DC string current is to be switched. When switching a high DC voltage and a high DC current, it may come to a non-extinguishing arc due to the missing zero crossings, unlike an AC application. At a common AC voltage frequency, an arc would typically extinguish by itself at the latest after 10 ms.

From the WO 2016/091281 A1 a device with a switching device for switching an alternating voltage or an alternating current is known, which has a bridging device for bridging the switching device in an operating phase. However, this device is described exclusively for alternating voltage or alternating current.

General description of the invention

The present invention is based inter alia on the finding that with the switching device disclosed here photovoltaic generators in the DC part (DC part), partially or completely, safely and loss of power on and off or electrically disconnected and reconnected and this the Basis for many applications.

The present invention has set itself the task of providing a photovoltaic system, the overvoltages especially in individual photovoltaic strands, possibly in parts of photovoltaic strands or in a plurality of photovoltaic strands, for example, caused by misplanning against this background , Failure during installation or by climatic influences such as in particular the temperature, to prevent even on Strangebene safely. The measuring and switching device adapted for this purpose is cost-effective, reliable and long-lasting at the DC strand voltages and DC line currents typical in photovoltaic systems, has a low power loss and can be accommodated in a small installation space. This measuring and switching device may also be suitable for retrofitting into existing photovoltaic systems.

A further aspect of the object of the invention is to provide a photovoltaic system which allows an increase in the output power already at the level of the photovoltaic system compared to known photovoltaic systems, without limiting the safety with regard to possible overvoltages.

A further aspect of the object of the invention is to provide a protective circuit for a photovoltaic system which already effectively protects against excessive voltages at the level of the line and allows the output power to be increased to the level of the photovoltaic system.

A further aspect of the object of the invention is to provide a method for automatically shutting off preferably a photovoltaic string, or a part of a photovoltaic string or a plurality of photovoltaic strings, of a photovoltaic system, which provides a high degree of safety offers protection against overvoltages; Furthermore, the method offers a high flexibility, e.g. during maintenance, and is convenient for the user to use.

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 invention relates to a photovoltaic system with at least one strand or photovoltaic strand, wherein the at least one photovoltaic string is formed by photovoltaic modules, which are connected in series with each other by means of a strand line and thus generate a common or added strand voltage. They provide photovoltaically generated electrical power with the desired phase voltage and a desired string current to a current collector, such as an inverter (sometimes referred to as a solar inverter). However, the photovoltaic system can also be connected without an inverter, for example to a charging unit as a current collector.

Currently, according to protection class II, phase voltages of up to 1000 V DC are possible. A further increase to up to 1500 V DC, the limit value of the low-voltage definition according to VDE0100, is being worked on. In the context of the invention, therefore, DC strand voltages are to be switched, which amount to a multiple of the voltage of a single photovoltaic module.

The photovoltaic system according to the invention further comprises a sensor device for measuring an electrical parameter of the photovoltaic string, in particular the strand voltage, a switching device which is installed in the strand line to at least part of the photovoltaic system or the at least one photovoltaic strand with the Switching device on and off, and a control device which is designed to compare the electrical characteristic with a predefined threshold, in particular a threshold voltage, and output in response to the comparison, a signal to the switching device, so that with the switching device of at least one part of the photovoltaic string or the at least one photovoltaic string can be switched off.

Photovoltaic systems are exposed to different environmental conditions depending on the location. Depending on the temperature gradient of the individual solar cell, the open voltage and the power output of the photovoltaic module change primarily due to the ambient temperature or the module temperature. An exemplary and typical value for the temperature gradient in the open-circuit voltage is -0.4% / K. This means that photovoltaic systems are typically planned and executed with a "safety margin" of a few hundred volts to the aforementioned current voltage limit of 1000 V or 1500 V respectively. For example, under no circumstances may the open-circuit voltage of a photovoltaic string exceed the voltage limit even on particularly cold winter days.

However, higher losses occur at low voltages and high currents, so that a photovoltaic system operating at a higher voltage and possibly smaller currents can not only have a higher output due to a larger number of PV modules, but also with a better one Efficiency works.

At the module level with a typical rated open circuit voltage of 37 V, the temperature-induced voltage difference between, for example, a cold winter's night at -20 ° C and module temperatures in summer under direct sunlight of + 65 ° C, ie at a temperature of 85 K, values of typically 12 , Reach 58 V at the aforementioned temperature gradient. This corresponds to 34% of the rated open circuit voltage. In a typical photovoltaic string of 25 modules, the voltage difference in the example above adds up to 314.5 volts. The system must therefore be designed accordingly, that in winter under no circumstances the voltage limit of 1000 V is exceeded. This costs the photovoltaic system in summer a lot of potential, which can not be exhausted, since the system is operated with a significantly lower strand voltage to safely avoid possible flashovers or a fire of the solar system.

However, since the highest yield is always collected in the summer and the photovoltaic system gives off significantly less power in winter due to the low solar radiation, the constructively fixed angle of the PV modules to the sun and depending on the location by shading and snow cover, it is makes economic sense to switch off the at least one photovoltaic string or the entire photovoltaic system on a few days in winter when an overvoltage threatens, and to forego the relatively low yield on these days. In the summer, on the other hand, the yield can be optimized, so that the potential failure in the winter is compensated quickly.

The photovoltaic system according to the invention, however, is also protected against overvoltages if the system is not planned, for example, by qualified personnel and errors occur during the planning or construction of the photovoltaic system. When a predefined threshold value, typically the voltage limit of 1000 V or 1500 V, is exceeded, the photovoltaic system protected according to the invention is designed so that the part of the photovoltaic string or the at least one photovoltaic string is switched off. This also has significance in the event that the photovoltaic system can be switched on and off by an external signal, for example via a communication signal controlled by the inverter, and the plant operator no longer influences the direct connection.

The photovoltaic system may further comprise a further sensor device, in particular an ambient temperature sensor for measuring the ambient temperature of the photovoltaic system or a module temperature sensor for measuring at least one module temperature of the photovoltaic modules, wherein the measurement signal of the sensor device is output to the control device and evaluated by the control device becomes.

The ambient or module temperature can be used in a simple example to record the cause of the shutdown of the photovoltaic string. With the determination of the ambient or module temperature, however, an imminent exceeding of a threshold value, ie typically an expected exceeding of the voltage limit of 1000 V or 1500 V, can be anticipated. If it is to be expected that the threshold value is exceeded, then possibly only a part of a photovoltaic string can be switched off preventively or only when the threshold value is exceeded, so that the remaining solar modules of the photovoltaic string can continue to deliver a power. Finally, the ambient or module temperature can also be logged for monitoring the measured line voltage and, if necessary, the correctness of the voltage measurement by the sensor device can thus be checked.

The photovoltaic system may further comprise a memory area associated with the memory for storing the threshold value. In this case, the control device may be designed to access the memory area for the purpose of comparing the electrical parameter of the at least one photovoltaic string with the threshold value in order to read it out. Preferably, the threshold value stored in the memory area can be changed by user input, so that it is possible to respond to changing requirements, for example a change in the voltage limit, with simple means and in this case, if necessary, no new circuit would be required.

The switching device of the photovoltaic system is installed in series in the strand line to turn on and off the at least one photovoltaic string with the switching device, i. the at least one photovoltaic string from the current collector, e.g. from a central collection point or from an inverter to electrically disconnect.

The switching device of the photovoltaic system preferably comprises a hybrid switch with a, in particular electromechanical, relay and a parallel to the relay connected semiconductor switching device, which in particular has at least one, preferably two semiconductor switches or transistors. As a result, the switching operations in which the strand voltage must be switched, are performed by the semiconductor switching device and the relay relieves the semiconductor switching device of the string current when the relay is closed in continuous operation. In other words, on the one hand with the relay when switching on and off only the remaining voltage across the semiconductor switching device connected and on the other commutes the relay due to its low resistance almost completely generated by the at least one photovoltaic string strand current.

When switching on the photovoltaic string with the preferred switching device so in particular the semiconductor switching device first switches on the photovoltaic string alone, the relay is open and initially also remains open. After a certain time delay, the relay is then additionally closed in the case of previously closed semiconductor switching device, so that the semiconductor switching device is relieved of the current flow by the later-closed relay connected in parallel. As a result, the relay only needs to switch a low voltage and the semiconductor switching device needs to carry the string current at best for a short time and not permanently. As a result, cheap standard semiconductor switch and standard relay can be used and the power loss in continuous operation can still be kept low. The shutdown takes place in reverse order; first the relay is opened with the semiconductor switching device still closed and after a certain time delay the semiconductor switching device is opened when the relay has already been opened. In other words, after opening the relay, the at least one photovoltaic string is switched off by additionally opening the semiconductor switching device.

The switching device furthermore preferably has a hybrid switch with a relay and a semiconductor switching device connected in parallel to the relay with at least one semiconductor switch.

The hybrid switch may define a closed state and an open state, wherein in the closed state photovoltaically generated current is passed from the at least one photovoltaic string to a current collector and the hybrid switch in the open state, the passage of photovoltaically generated electricity from the at least one photovoltaic string breaks. The control device can then in particular be further configured to open the hybrid switch in a user-controlled manner in response to a user input.

In one embodiment, the hybrid switch may comprise a parallel connection of the relay and a back-to-back circuit of two semiconductor switches, in particular a parallel circuit of a relay and a back-to-back circuit of two field-effect transistors, preferably MOSFETs.

The switching device, the control device and the sensor device connected to the control device for measuring the electrical characteristic of the at least one associated photovoltaic line are housed in a preferred embodiment in a common switch housing housing.

In another example, the controller may be configured to electrically connect the associated photovoltaic string to the current collector in response to the at least one electrical characteristic measured by the sensor device when there is a user enable.

Incidentally, the sensor device may include, for example, an input voltage sensor which measures the input side voltage U1 on the switching device, i. the strand tension. Furthermore, the sensor device may comprise an output voltage sensor which measures the current collector-side output voltage U2 at the switching device.

The control device can be configured to electrically connect the associated photovoltaic line to the central collection point in response to the measured line-side input voltage U1 and / or to the measured current-collector-side output voltage U2 if a user enable is present.

The threshold value is in particular a threshold voltage for the phase voltage of the at least one photovoltaic string. The value of the threshold voltage is preferably greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably 1250 V +/- 30%. In typical current applications in Germany, for example, the threshold voltage could be set to 1000V or 1500V in accordance with current standards.

According to the invention is also a protection circuit which is designed for the DC part of a photovoltaic system for switching off a part of a photovoltaic string or at least one photovoltaic strand of a photovoltaic system of a current collector. The protection circuit can be prepared so that it can be used as a simple retrofit option for existing solar systems.

The protective circuit according to the invention comprises a sensor device for measuring an electrical parameter of the photovoltaic string, in particular the string voltage, a switching device which is installed in the string to at least part of the photovoltaic system or the at least one photovoltaic string with the switching device of a Switch on and off current collector and a control device which is designed to compare the electrical characteristic with a predefined threshold, in particular a threshold voltage, and output in response to the comparison, a signal to the switching device, so that with the switching device of at least a part of Photovoltaic strand or the at least one photovoltaic string can be switched off by the current collector.

According to the invention is also a method for autonomous or "automated" switching off at least a portion of a photovoltaic system or at least one photovoltaic string of a photovoltaic system, wherein the at least one photovoltaic string is formed by photovoltaic modules, which by means of a string line serially interconnected and thus generate a strand voltage. The method comprises the steps of setting a threshold voltage, measuring the current string voltage generated in the at least one photovoltaic string with a sensor device, comparing the current string voltage with the threshold voltage and when the threshold voltage is exceeded by the current string voltage automatic triggering (U ext ) a switching device by a trigger signal to turn off the at least one photovoltaic string or the part of a photovoltaic string from the current collector.

In the method for automatically switching off at least a part of a photovoltaic system or at least one photovoltaic line of a photovoltaic system, the defined threshold voltage can be stored in a memory area of a control device. In this version is the Threshold particularly easily digitally accessible and possibly modifiable with programmatic means, so that an adaptation to voltage specifications or changing environmental conditions or the like. By means of "update" can be changed.

The independently switched-off photovoltaic system can be switched back to the current collector by means of triggers (U ext., Start = on) of the switching device of the at least one photovoltaic string by a trigger signal to the part of the photovoltaic string or the at least one photovoltaic string turn on again.

It may be advantageous to consider the ambient temperature or the module temperature for the method. Therefore, in one embodiment, the method may include the further steps of measuring the ambient temperature with the sensor device and taking into account the measured ambient temperature in comparing the current strand voltage with the threshold voltage or at the restart of the portion of the photovoltaic string or at least comprise a photovoltaic string.

The switching device is installed in the DC part of the photovoltaic generator, preferably in front of the central collection point and switches on here the at least one photovoltaic string on and off. However, the invention is not limited to the fact that exactly one switching device switches exactly one photovoltaic string. It is also within the scope of the invention that a plurality of parallel-connected photovoltaic strings are connected in common by the same switching device and also that the photovoltaic generator has only one photovoltaic string. Generally, therefore, a part of or the entire photovoltaic generator is switched by the switching device. However, it is in particular not a circuit at the module level at a low module voltage, but a circuit of a plurality of photovoltaic string connected in series photovoltaic modules, which requires the high switching voltage. Thus, the switching device is connected between the plurality of serially connected photovoltaic modules and the current collector, e.g. the inverter or between the plurality of serially connected photovoltaic modules and a generator junction box. The switching device is electronic and thus externally triggerable. Therefore, the switching device, or in the presence of multiple switching devices, the switching devices can be remotely or automatically triggered by the user, which is advantageous over a conventional hand-operated DC disconnector in the generator junction box.

The switching device is advantageously, despite the typical in photovoltaic systems DC strand voltages and DC line currents cost, reliable and durable, and has a low power dissipation. It can be accommodated in particular in a small space.

Advantageously, a photovoltaic system is thus provided, which makes it possible to turn on and off at least one photovoltaic line user-controlled and possibly electronically triggered, which is comfortable and ensures high safety standards, and is maintenance and repair friendly.

The switching device is preferably used in the strand cabling. In particular, the switching device is accommodated by a photovoltaic module-overlapping strand box, preferably with a (plastic) housing, and this strand box is inserted into the strand cabling between the series connection of the photovoltaic modules and the current collector. The strand box may have at the input and / or output connector for releasable insertion into the strand line and for retrofitting. As a result, even the retrofitting of existing photovoltaic systems is possible.

The switching device can in a strand box, eg in a start box according to WO2014 / 122325 A1 integrated, which is hereby incorporated in full by reference.

The user can e.g. switch off the associated photovoltaic string at an external switch on the photovoltaic module cross-strand box or the user sends from a central control of the multi-strand photovoltaic system selectively to one, single, multiple or all strand boxes a shutdown trigger signal, wherein in response then switch off the associated switching device or the associated switching devices or the associated photovoltaic strings or switch off. The strand box can also switch off the photovoltaic string particularly advantageously by a signal from the protective circuit or by a signal generated in the string box by the control device.

The user can thus advantageously locally on the associated photovoltaic strand and / or centrally on the plant side, but in particular but photovoltaic module cross-controlled controlled, the targeted or the switch off desired photovoltaic strings or separate their current-carrying connection to the central collection point or inverter.

The switching device preferably switches either the Pluspolleiter or Minuspolleiter and thus separates the electrical circuit of the at least one photovoltaic string. Nevertheless, it may be advantageous to insert the strand box into both conductors (positive pole and negative pole) of the string line, in front of and behind the first or last photovoltaic module, into the at least one photovoltaic string.

The relay and the semiconductor switching device are connected in parallel to each other and the parallel connection of relay and semiconductor switching device is connected in series in the photovoltaic string. The relay and the semiconductor switching device are therefore connected in series and parallel to each other in the photovoltaic string.

The photovoltaic system comprises a photovoltaic generator with one or more parallel photovoltaic strings. If several photovoltaic strings are connected in parallel, the switching device can selectively switch on or off either one photovoltaic string or optionally also several or all photovoltaic strings, depending on which nominal currents supply the photovoltaic strings and for which current the switching means designed. That for multiple photovoltaic strings, the switching device may be located upstream or downstream of the central collection point. The central collection point forms a parallel switching point of several photovoltaic strings. In the presence of several parallel photovoltaic strings (multi-strand photovoltaic system), however, it is particularly advantageous to arrange the switching device upstream of the central collection point.

This has several advantages, firstly, then only the power of a photovoltaic string must be switched per switching device and secondly, each photovoltaic string can be individually switched on and off. In a multi-strand photovoltaic system so two or more photovoltaic strings are connected in parallel and the photovoltaic strings are each formed by serially connected photovoltaic modules.

In other words, in the DC part of the photovoltaic system, the at least one photovoltaic string is disconnected from the current collector, e.g. the inverter separated by the hybrid switch opens, thereby interrupting the flow of current from the at least one photovoltaic string to the pantograph and the at least one photovoltaic string is turned on by the hybrid switch closes and electrically connects the at least one photovoltaic string with the current collector so the current flow from the at least one photovoltaic string into the current collector is made possible.

In particular, the switching device defines a closed state and an opened state and, in the closed state, conducts photovoltaically generated current from the at least one photovoltaic string to a current collector and interrupts in the opened state the transmission of photovoltaically generated current from the at least one photovoltaic strand. Preferably, a control device is embodied which is designed to open and / or close the switching device or the hybrid switch in a user-controlled manner in response to a user input. Thus, the user, e.g. in the event of malfunctions or maintenance work, the at least one photovoltaic string can be selectively switched on and off at any time.

Preferably, the control means is adapted to receive an external user-generated generated strand shut-off trigger signal and to turn off the at least one photovoltaic string in response to the strand turn-off trigger signal by the control means opening the switching means and thereby directing the at least one photovoltaic string at least one side thereof Pantograph disconnects.

Further preferably, the control means is adapted to generate an autonomously generated strand shut-off trigger signal in response to the signal of the sensor device, that is typically in response to the strand voltage, and to turn off the at least one photovoltaic strand in response to the strand turn-off trigger signal in that the control device opens the switching device and thus separates the at least one photovoltaic strand at least on one side from the current collector. The switching device is therefore in particular an actively switching or switchable and / or electronically controlled switching device.

In a multi-strand photovoltaic system, at least one of the parallel photovoltaic strings, preferably all of the parallel photovoltaic strings in their respective associated string line, in particular between the photovoltaic modules of this particular photovoltaic string and the central collection point a switching device according to the invention, by means of which the current-carrying connection between this associated photovoltaic string and the central collection point is user-controlled, so selectively separable on request of the user to the at least one photovoltaic string, or to any desired photovoltaic string targeted and individually off the parallel circuit. In other words, the switching device according to the invention can also be used for single-strand shutdown in a multi-strand photovoltaic system. That is, it can be a single or multiple individual photovoltaic strands can be selectively switched off and the other photovoltaic strings of the parallel circuit remain in operation and can continue to feed photovoltaically generated electricity through the central collection point, in particular in the inverter. In this case, the user can thus, for example, for maintenance purposes, repair or localized malfunction specifically off one or more of the photovoltaic strings individually or separate the current-carrying connection of the user or the desired photovoltaic strands to the central collection point, so that they no Feed more electricity through the central collection point. It can therefore be switched off all photovoltaic strands (and not just individual photovoltaic modules) or the current-carrying connection of one or more whole photovoltaic strands are separated to the central collection point.

The at least one semiconductor switch or transistor is in particular a field-effect transistor, preferably a MOSFET.

It has proved to be particularly advantageous if the switching device or the hybrid switch is designed to interrupt the current flow in the opened state not only in one direction, but in both directions. As a result, not only a safety shutdown, e.g. in case of faults or maintenance, so an interruption of the flow of photovoltaic electricity generated by the associated photovoltaic string can be achieved. It is also possible to use currents in opposite directions, ie, transverse or return currents, e.g. from other parallel-connected photovoltaic strings, be interrupted in the associated photovoltaic. This is particularly advantageous in multi-strand photovoltaic systems, but optional for the presently claimed invention.

This can e.g. be achieved in that the hybrid switch comprises a back-to-back circuit of two semiconductor switches or transistors, in particular a back-to-back circuit of two field effect transistors, preferably of two MOSFETs comprises, or the semiconductor switching device of a such back-to-back circuit exists. In other words, the hybrid switch is a parallel circuit of the relay and a back-to-back circuit of two semiconductor switches, in particular a parallel circuit of a relay and a back-to-back circuit of two field effect transistors, preferably MOSFETs. This parallel circuit is connected serially in the string line.

According to a preferred embodiment of the invention, the switching device may additionally comprise a reverse current protection circuit. The switching device may comprise a sensor connected to the control device for measuring an electrical characteristic on the associated photovoltaic string, wherein the control device is adapted to connect the associated photovoltaic string to the central collection point in response to the electrical characteristic measured with the sensor to automatically break even in the reverse current direction. In other words, the switching device is preferably with the reverse current protection function according to the DE 10 2016 117 049 combined. Thus, the advantages of the backflow prevention according to the in the DE 10 2016 117 049 described invention and a user-controlled shutdown in the DC part of a photovoltaic system are combined, but this is optional.

The switching device is preferably designed to close the semiconductor switching device, in particular the field effect transistor (s), preferably MOSFETs, when the associated photovoltaic string or electrical connection is connected to the current collector, and to close the relay after a time delay thereafter shut down.

The switching device is preferably further formed when switching off the associated photovoltaic string, or separating the associated photovoltaic string from the current collector, first to open the relay and only after a time delay thereafter the semiconductor switching device, in particular the one or more field effect transistors, preferably to open MOSFETs.

This can ensure that the relay does not have to switch the full phase voltage, so that a due to the DC voltage may not be extinguished arc can be avoided. Nevertheless relieves the relay, the semiconductor switching device in continuous operation, so that the long-term power loss in an acceptable for the specific installation conditions in a photovoltaic generator Frame can be kept. Advantageously, no high current relay needs to be used, but a simple small standard relay can be used. The relay is spared, which enhances the longevity of the switchgear and ensures safety, reliability and longevity in the degree required for photovoltaic systems.

The switching device may be configured to perform a test routine before (re) switching on the at least one photovoltaic string, to test at least one electrical parameter of the associated photovoltaic string in the test routine, and to maintain a predefined threshold value for the at least one electrical parameter to turn on the at least one photovoltaic string, if a user release is present.

The switching device can also be designed to measure the photovoltaically generated current flow through the associated string line and to close the relay only when the photovoltaic current I flowing through the string exceeds a predefined threshold I_min, or after a time delay after the By the strand line flowing photovoltaically generated current I has exceeded a predefined threshold I_min.

The switching device may further include a control device and a sensor device connected to the control device for measuring at least one electrical parameter on the associated photovoltaic string. The control device may be configured to electrically connect the associated photovoltaic line to the current collector in response to the at least one electrical characteristic measured by the sensor device, if a user enable is present, wherein the sensor device in particular comprises an input voltage sensor which detects the input voltage U1 at the input side Measuring device measures and / or comprises an output voltage sensor which measures the collection point side output voltage U2 to the switching device. The control device may be designed to control the switching operations of the relay and / or the semiconductor switches in response to the measured line-side input voltage U1 and / or to the measured collector-point-side output voltage U2.

Advantageously, when turned on, a plurality of switching operations may first be performed by the semiconductor switching device, e.g. the back-to-back MOSFET circuit is performed, e.g. until certain operating parameters are reached before the relay is closed. In other words, when switched on, the relay remains open until certain operating parameters have been reached, even if several switching operations are performed with the semiconductor switching device during this time. Thus, the number of switching operations of the relay can be kept low. In production or continuous operation, in particular after the desired operating parameters have been reached, the relay then relieves the semiconductor switching device. Nevertheless, with the hybrid switch fully open, i. when both the semiconductor switches and the relay are open, bidirectional isolation of the electrical connection is achieved, i. the current flow in both directions are interrupted when a back-to-back circuit is used.

The time delay when switching on and / or when switching off is preferably less than or equal to 2000 ms, preferably less than or equal to 700 ms, preferably less than or equal to 300 ms. At least the semiconductor switching device should not be closed longer than for this maximum delay time and not relieved by the relay, so closed the semiconductor switching device and the relay be open when the full (rated) strand current, or if a strand current of greater than or equal to 5 A, greater than or equal to 8 A, greater than or equal to 10 A, or 12.5 A +/- 40% flows through the semiconductor switching device. This means that the maximum delay time can be calculated from the time at which, at least theoretically, the nominal current could flow, if the irradiation is correspondingly large. In other words, the hybrid switch is controlled so that a state in which the semiconductor switching device is closed, the relay can be opened, and at the same time the rated current can flow, that is, the rated current can flow through the non-relieved semiconductor circuit is not longer than the maximum delay time. More preferably, the delay time between 50 ms and 2000 ms, preferably between 100 ms and 1000 ms, preferably between 150 ms and 500 ms, preferably between 200 ms and 300 ms, at least if in the photovoltaic string, a strand current flows or at least can flow , which essentially corresponds to the rated current. Depending on which components are used, the semiconductor switching device can at least for a correspondingly short delay time to pass through the full strand performance even without relief by the relay alone, even if it is installed without special cooling measures in a strand box. The time delay of the switching operation of the semiconductor switching device can therefore be related to the previous switching operation of the relay or vice versa or to the achievement of certain threshold values for the electrical characteristics, eg for the input voltage U1, for the output voltage U2 and / or for the phase current I.

The part of the photovoltaic generator which is switched by the switching device, that is to say in particular the associated photovoltaic line, preferably has a nominal DC voltage of greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably 1250 V +/- 30% and / or a DC rated current of greater than or equal to 5 A, preferably greater than or equal to 8 A, preferably greater than or equal to 10 A, preferably of 12.5 A +/- 40%.

The hybrid switch as a whole is therefore for a DC switching voltage of greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably 1250 V +/- 30% and / or for a DC forward current of greater than or equal to 5 A, preferably greater than or equal to 8 A, preferably greater than or equal to 10 A, preferably designed from 12.5 A +/- 40%. In particular, the hybrid switch as a whole is designed for a DC switching voltage of greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably of 1250 V +/- 30%.

In particular, the semiconductor switching device or are the field effect transistors, preferably MOSFETs, preferably for a drain-source voltage (V _DS ) of greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably from 1250 V +/- 30% trained.

The semiconductor switching device or the field effect transistor (s), preferably MOSFETs, are preferably for a drain current (I _D ) of greater than or equal to 5 A, preferably greater than or equal to 8 A, preferably greater than or equal to 10 A, preferably 12.5 A +/- 40% trained.

Due to the short duration of the current flow through the semiconductor switching device, the power loss occurring at the hybrid switch is nevertheless justifiable. There is no need to use overly large and expensive semiconductor switches.

Field-effect transistors, preferably MOSFETs, can be used, which have a turn-on resistance (Resistance-Drain-Source-On, RDS-on) of greater than or equal to 100 mOhm, preferably greater than or equal to 300 mOhm, preferably greater than or equal to 500 mOhm, preferably 690 mOhm +/- 40%.

Although this generates a relatively large power loss of possibly one watt, a few watts or more, but this is acceptable in particular by the discharge through the parallel relay. Such field effect transistors, in particular MOSFETs, are inexpensive and have a small size.

The one or more semiconductor switches, field-effect transistors, or MOSFETs can, based on a rated current of 8.5 A or 10 A of the at least one photovoltaic string, even a calculated power loss of greater than or equal to 2 W, greater than or equal to 5 W, greater than or equal to 10 W, in particular greater than or equal to 40 W, when the one or more semiconductor switches, field effect transistors or MOSFETs are closed and the relay is open (intermediate switching state).

On the other hand, based on a nominal current of 8.5 A or 10 A of the at least one photovoltaic string, the hybrid switch nevertheless only generates a calculated power loss of preferably less than or equal to 10 W, preferably less than or equal to 5 W, preferably less than or equal to 2 W, preferably less than or equal to 1 W, when the semiconductor switching device and the relay are closed (continuous operation state). In particular, in production mode, the hybrid switch has a power dissipation of less than or equal to 1 W, for example 1000 volts and 10 amps (typ., Plus 25% reserve) per photovoltaic string when the semiconductor switching device and the relay are closed.

The relay is preferably designed for a DC transmission current of greater than or equal to 5 A, preferably greater than or equal to 8 A, preferably greater than or equal to 10 A, preferably 12.5 A +/- 40%. On the other hand, it is preferably sufficient if the relay is designed for a DC switching current of less than or equal to 8 A, in particular less than or equal to 6 A, in particular less than or equal to 4 A, in particular 2 A +/- 50%.

Furthermore, it is preferably sufficient if the relay has a maximum AC switching voltage of less than or equal to 800 V, in particular less than or equal to 500 V, in particular of 400 V +/- 50%.

This keeps cost and size of the relay, especially for installation in a strand box also within reasonable limits.

Further preferably, the switching device may be designed to check electrical characteristics of the associated photovoltaic string before (re) turning on the associated photovoltaic string in a test routine and to close the switching device while maintaining predefined threshold values for the electrical parameters and after user release. That the closing of the switching device takes place only when both are present, i. if both the test conditions for the electrical characteristics are met, as well as the user release for the (re-) to power up. Only then the associated photovoltaic string is switched on again. In particular, the semiconductor switches can first be closed as a test and electrical parameters, such as input voltage, output voltage and / or the strand current can be measured while the relay is still open. This process can be repeated several times before the relay is also closed, whereby the relay can be spared.

In particular, the switching device thus comprises a current sensor, which measures the photovoltaically generated current flow through the associated string line. The switching device preferably closes the relay only when the photovoltaically generated current flowing through the line exceeds a predefined threshold. This can ensure that the associated photovoltaic string is only taken into permanent production mode when it is fully operational.

Preferably, at least at times, in particular in the permanent production operation of the photovoltaic string, the photovoltaically generated current flows in the part of the photovoltaic string in which the full nominal voltage of the plurality of series photovoltaic modules or the entire photovoltaic string is applied, preferably exclusively by metallic Ladder, eg Metal cables, metal connectors and the relay and at least not permanently by semiconductor devices. As a result, the power loss can be kept low in an advantageous manner, so that the switching device can optionally be installed in existing housing, without these overheat.

In a multi-strand photovoltaic system, each parallel photovoltaic string preferably has such a switching device in front of the central collection point. The switching devices are photovoltaic module-spanning, i. are each responsible for the entire photovoltaic string with several serially interconnected photovoltaic modules.

The switching devices have input side (ie photovoltaic strand or photovoltaic module-side) a positive terminal and a negative terminal for connecting the positive pole or negative pole of the strand line and the output side (ie collection point side) a positive terminal and a negative terminal for connecting the positive pole or negative pole of a Continuation of the string line up to the central collection point of the photovoltaic strings or to the DC input of the inverter. Accordingly, in particular the entire phase voltage is applied to the switching device and / or the entire phase current flows through the switching device

As already stated above, the present invention develops particular advantages in combination with the backflow protection according to the DE 10 2016 117 049 , If the switching device also acts as a reverse current protection device in a multi-strand photovoltaic system, this additionally prevents a cross-flow from becoming so great that the direction of the current flow in the associated photovoltaic string is reversed, ie a negative current back into the associated photovoltaic system. Strand flows. This can be achieved in particular with the back-to-back circuit comprising two semiconductor switches, in particular the back-to-back circuit comprising two field-effect transistors, for example MOSFETs. Advantageously, therefore, unwanted return currents can be prevented, which could otherwise arise if the associated photovoltaic string should be low-impedance than the inverter or corresponding current collector downstream of the central Sammelppunkt. This can have a positive influence on the lifetime of the associated photovoltaic modules. Depending on the safety equipment of the photovoltaic system, the reverse current protection function can also increase the safety of the system, in particular when switching off individual photovoltaic strings or the photovoltaic system, eg due to inadequate irradiation, maintenance work or in the event of a danger switch-off, in particular in which the reverse current protection function prevents that a shutdown of the associated photovoltaic string is prevented due to a return current.

Preferably, the switching device is installed in an electrically insulating housing, which has a positive pole connection for the positive pole of the string line and a negative terminal for the negative pole of the string line of the associated photovoltaic string at the string-side input. Further Preferably, the switching means at the collective point-side output on a positive pole terminal for the positive pole and a negative pole terminal for the negative pole of the extension of the strand line, which leads to the central collection point, on. The terminals on the housing are preferably designed as photovoltaic connectors, eg according to the Applicant's SUNCUX® system. The housing with the switching 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 strand box, which also as a retrofit solution in existing strand lines between the photovoltaic modules each of a photovoltaic string and the central collection point or the common inverter can be inserted to retrofit an existing multi-strand photovoltaic system.

Preferably, the switching device includes a sensor connected to the control device for measuring an electrical characteristic at the associated photovoltaic string. In response to the measured with the sensor electrical characteristic, the control device can switch the switching device, but possibly only if there is a user release. In particular, in response to the electrical characteristic measured with the sensor, the control device prevents the closing of the switching device and / or at least the relay, e.g. If the measured electrical characteristic is outside a decisive for the restarting safety condition for the first electrical characteristic.

• - Eingangsspannung am strangseitigen Eingang der Schalteinrichtung,
• - Ausgangsspannung am sammelpunktseitigen bzw. wechselrichterseitigen Ausgang der Schalteinrichtung,
• - Strangstrom des zugehörigen Photovoltaik-Strangs bzw. durch die Schalteinrichtung oder Strangbox,
• - negativer Stromfluss.

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

• Input voltage at the line-side input of the switching device,
• Output voltage at the collector-side or inverter-side output of the switching device,
• Strand current of the associated photovoltaic string or by the switching device or strand box,
• - negative current flow.

A negative current flow means that the current in the photovoltaic string flows counter to the direction of flow of the photovoltaically generated current during operation by the switching device. That the current sensor is in particular designed to be able to measure a negative current flow.

The hybrid switch may open in response to one or more of these electrical characteristics measured with the sensor or sensors and interrupt the connection of the associated photovoltaic string to the current collector. The switching device thus preferably contains a current sensor, which may optionally also measure negative currents, and / or an input voltage sensor and / or an output voltage sensor.

Further details of an optional additional backflow prevention are described below.

According to a preferred embodiment of the invention, the sensor is a current sensor, which can also measure a negative current flow through the switching device. The switching device can interrupt the connection of the associated photovoltaic string to the central collection point, ie to the parallel connection with the other photovoltaic strings and to the DC input of the inverter, at least if the current in the associated photovoltaic string is negative and / or a predefined Threshold for the amount of negative current exceeds. However, a negative current is not a necessary condition for disconnection. Depending on which operating and safety parameters are specified, the switching device can already perform the interruption even if the current is still positive, but is below a predefined safety threshold. This can occur, for example, when the photovoltaic modules of the associated photovoltaic string are significantly more shaded than the photovoltaic modules of the other photovoltaic strings. In this case, the cross-currents may not yet provide for a total negative current flow in the associated photovoltaic string, but may already reduce the photovoltaic-generated current from the associated photovoltaic string to such an extent that the production operation of that associated photovoltaic string does not make economic sense, so it is better to break the connection of this associated photovoltaic string to the parallel connection with the other photovoltaic strings and to the common inverter. This may be useful, in particular, if the current measured by the switching device is still positive, but is considerably below the maximum current of the photovoltaic string, for example less than 10% of the maximum current of the photovoltaic string. In other words, the control device is preferably designed to automatically switch the switching device, or the connection of the associated Photovoltaic string to the parallel circuit and to interrupt the inverter when the condition occurs that the strand current I is smaller than a predefined threshold I0. The predefined threshold I0 can be selected between positive and significantly smaller than the maximum current of the associated photovoltaic string and a negative safety value for the current flow. Mathematically speaking, the switching condition can be defined as I <I0, where I0 is selected from an interval [I1, I2], where I1 is a negative safety value at which the associated photovoltaic string could be damaged and I2 is a positive value, below whose economic operation no longer makes sense.

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

According to a preferred embodiment, in response to the measured line side input voltage and / or the measured collector side or inverter side output voltage, the switching device switches the associated photovoltaic line whose connection to the central collection point is interrupted back to the central collection point with the other parallel photovoltaics Strands and thus to the DC input of the inverter electrically, if the user release is present.

According to a further preferred embodiment of the invention, the input voltage is compared with the output voltage and the controller controls the switching device in response to the comparison of the measured line side input voltage and the measured current collector side output voltage, in particular to the associated photovoltaic string whose connection to the current collector is interrupted again to the pantograph when the user release is present. The voltage comparison can ensure that after the electrical restart of the associated photovoltaic string the desired operating and safety parameters are fulfilled, e.g. that no negative current flows back into the associated photovoltaic string or the positive production current exceeds a minimum value by the associated photovoltaic string is only electrically switched on again when the difference between output voltage U2 minus input voltage U1 is smaller than a predefined threshold U0. If U0 = 0, this means that the output voltage U2 is smaller than the input voltage U1. In this case, a certain tolerance can be present, in particular, the effect can be exploited that the input voltage of the associated photovoltaic string whose connection to the central collection point is interrupted, the open circuit voltage, whereas the output voltage, which is different from that of the other parallel photovoltaic modules generated voltage already represents a load voltage, which is typically about 20% lower than the open circuit voltage, because the inverter is already working. Thus, in response to comparing the open circuit voltage of the associated photovoltaic string with the load voltage of the other photovoltaic strings, the controller may return the associated photovoltaic string whose connection to the central collection point is interrupted to the central collection point with the other parallel photovoltaic cells. Strings and thus to the DC input of the inverter turn on when the user release is present. In addition to the voltage comparison, it is still possible to check 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.

In the closed state, the switching device electrically connects the associated photovoltaic line to the current collector and, in the open state, bi-directionally interrupts the current-carrying connection of the associated photovoltaic line to the current collector within the line.

Preferably, the semiconductor switches used and / or the relay are designed as normally open (Normally Off or Normally Open, NO). While this may seem disadvantageous at first glance, electrical power is required to hold the on-state. However, this is accepted in order to achieve the associated safety, namely that the connection of the associated photovoltaic string in the normal state of the switching device to the parallel circuit with the other photovoltaic strings and to the DC input of the inverter is interrupted.

The presently disclosed invention is particularly advantageous to use in photovoltaic systems in which the series-connected photovoltaic modules in at least one of the photovoltaic strands, preferably in all photovoltaic strands, each have protective circuits, by means of which the Photovoltaic modules can be individually switched off from the associated photovoltaic string, and wherein the protection circuits of the individual photovoltaic modules short-circuits the output of the respective photovoltaic module at the connection points for the stranded line to produce a low-resistance bypass for the respective photovoltaic module , Such protective circuits for the photovoltaic modules are in the WO2013 / 026539 A1 which is hereby incorporated by reference and which is hereby incorporated by reference. Furthermore, the presently disclosed invention is particularly advantageous to use in photovoltaic systems in which the associated photovoltaic string has a start circuit, which is designed to re-activate such or other protection circuits of the individual photovoltaic modules of the associated photovoltaic string. Such starting circuits for the photovoltaic strings are in the WO2014 / 122325 A1 which is hereby incorporated by reference and which is hereby incorporated by reference.

Preferably, such a start circuit for starting the associated photovoltaic string and the switching device for the associated photovoltaic string can be accommodated in a common housing, so that a strand box with combined on and off function for the associated photovoltaic string is formed. The strand box is provided with positive and negative terminals at the input and positive and negative terminals at the outlet of the string box between the series of photovoltaic modules of the associated photovoltaic string and the central collection point with the other photovoltaic strings in the associated photovoltaic cells. Strand switched. As a result, superfluous components, in particular connectors can be saved, which can have a positive effect on costs, life and loss management of the photovoltaic system. The power loss of the switching device is so low in production mode with the relay closed that the thermal load is acceptable.

Preferably, each photovoltaic string is equipped with the described photovoltaic module-overlapping switching device or strand box.
user-controlled triggering of the switching device of the at least one photovoltaic string by an electrical or electronic trigger signal in order to disconnect the at least one photovoltaic string from the current collector,
user-controlled triggering of the switching device of the at least one photovoltaic string by an electrical or electronic trigger signal to turn on the at least one photovoltaic string back to the current collector, possibly in response to the fulfillment of further test conditions.

It will be apparent to those skilled in the art that although the invention can be used particularly advantageously for photovoltaic systems, it can also be used in principle for other DC generators. These should not be excluded.

In the following the invention will be explained in more detail by means of embodiments and with reference to the figures, wherein the same and similar elements are partially provided with the same reference numerals and the features of the various embodiments can be combined.

list of figures

• 1 ein Blockschaltbild einer Photovoltaik-Anlage mit parallelen Photovoltaik-Strängen,
• 2 ein Blockschaltbild einer Schutzschaltung für ein Photovoltaik-Modul,
• 3 ein Blockschaltbild einer Strangbox mit der Schalteinrichtung,
• 4 einen Schaltplan der Ansteuerung der Hybrid-Schaltung aus Relais und MOSFET-Back-to-Back-Schaltung,
• 5 einen Schaltplan für ein Schaltnetzteil zur Ansteuerung der MOSFET-Back-to-Back-Schaltung,
• 6 ein schematisches Ablaufdiagramm für das Starten, Überwachen und Abschalten des zugehörigen Photovoltaik-Strangs, und
• 7 ein Ablaufdiagramm für das Starten, Prüfen, Überwachen und Abschalten des zugehörigen Photovoltaik-Strangs.

Show it:

• 1 a block diagram of a photovoltaic system with parallel photovoltaic strings,
• 2 a block diagram of a protection circuit for a photovoltaic module,
• 3 a block diagram of a strand box with the switching device,
• 4 a circuit diagram of the control of the hybrid circuit of relay and MOSFET back-to-back circuit,
• 5 a circuit diagram for a switching power supply for driving the MOSFET back-to-back circuit,
• 6 a schematic flow diagram for starting, monitoring and switching off the associated photovoltaic string, and
• 7 a flow chart for starting, testing, monitoring and switching off the associated photovoltaic string.

Detailed description of the invention

Referring to 1 includes the multi-strand photovoltaic system 1 a plurality of photovoltaic strings connected in parallel, of which only two photovoltaic strings for the sake of simplicity 10 . 10 ' are shown.

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

Referring to 2 contains every protection circuit 14 . 14 ' a short-circuit switch S3 for strand side shorting of the associated photovoltaic module 12 . 12 ' and a serial disconnect switch S4 with which the associated photovoltaic module 12 . 12 ' from the photovoltaic string 10 . 10 ' can be separated. For shading or failure of a photovoltaic module 12 . 12 ' closes the short-circuit switch S3 and the serial disconnect switch S4 opens, leaving the respective photovoltaic module 12 . 12 ' separated from the photovoltaic strand, idles and the photovoltaic strand 10 . 10 ' still remains closed, so that continues to generate the photovoltaic power of the remaining photovoltaic modules of this photovoltaic string 10 . 10 ' by the closed also in this protective state string line 16 . 16 ' can flow. For further details of the protection circuit optional for the present invention 14 . 14 ' will be on the WO 2013/026539 Reference is hereby made to the subject matter of the present disclosure by reference.

Again referring to 1 is in every photovoltaic strand 10 . 10 ' a string box 20 . 20 ' inserted, which as starting boxes according to the WO 2014/122325 A1 may be formed, and through which both strand lines 16 . 16 ' go through it. Inverter side of the strand boxes 20 . 20 ' are sequels 17 . 17 ' the string lines 16 . 16 ' at a central collection point 22a . 22b , or its plus and minus pole, connected in parallel to the photovoltaic power generated in this example, several photovoltaic strands 10 . 10 ' etc. connected in parallel in the DC input 24a . 24b of the common inverter 26 feed. At the AC output 28 of the inverter 26 the alternating current is provided for feeding into a supply network.

The string boxes 20 . 20 ' in this example are from an external 24 volt power supply 32 ( 2 ) to perform the desired switching operations. However, the supply can also be done by a start-up photovoltaic module, which no protection circuit 14 . 14 ' has and therefore automatically with incident light the respective photovoltaic strand 10 . 10 ' and with it the associated strand box 20 . 20 ' supplied with electrical power. For more details, see the WO 2014/122325 A1 Reference is hereby made to the subject matter of the present disclosure by reference.

The string box 20 has a module temperature sensor in this example 49b on to the immediate temperature of the photovoltaic module 12 to measure and forward this or derived information to the controller.

Referring to 3 is a string box 20 one of the photovoltaic strands 10 shown in more detail. All other parallel connected photovoltaic strings 10 . 10 ' etc., if available, are preferably constructed the same. However, the present invention can also be used in a single-strand photovoltaic system 1 So with a DC generator 2 to be used, which consists of only one photovoltaic strand 10 consists.

The photovoltaic modules 12 with connected protection circuit 14 , what a 3 the sake of simplicity, is not shown separately, form the photovoltaic string in a series circuit 10 , The positive pole 16a and the negative pole 16b the string line 16 are at a positive pole entrance 34a or a minus pole input 34b the strand box 20 connected to the strandbox 20 to be fed. To a positive pole output 36a or a negative pole output 36b are corresponding sequels 17 the string line 16 to the positive pole 24a or to the negative pole 24b of the DC input 24 of the inverter 26 , which in this example forms the current collector for the photovoltaic power, connected. The one of the photovoltaic modules 12 of the photovoltaic string 10 Photovoltaically generated electricity flows accordingly in the production operation through the strand box 20 therethrough. At the entrances and exits 34a . 34b ; 36a . 36b are the module-side and collection-point-side sections 16 . 17 the strand line, preferably with connectors (not shown) connected. Additional optional parallel photovoltaic strings 10 ' are the dashed lines, which are the two poles of the central collecting point 22a . 22b lead, symbolizes.

The string box 20 contains a switching device 38 , which in the preferably waterproof plastic housing 21 the strand box 20 is integrated. The switching device 38 includes a hybrid switch S1 which serially into the photovoltaic string 10 , in this example in a branch of the strand line (in this example, the positive pole) is connected. With the serial hybrid switch S1, the current-carrying connection of the associated photovoltaic string 10 to the inverter 26 user-controlled interrupted and the associated photovoltaic string 10 to be turned off. A control device 42 in the form of a microcontroller controls the serial hybrid switch S1, which may also be referred to as a disconnect hybrid switch, and monitors a current sensor 44 , an input voltage sensor 46 and an output voltage sensor 48 to electrical characteristics of the associated photovoltaic string 10 to win.

The input voltage sensor 46 is parallel to the input terminals 34a . 34b the strand box 20 connected to measure the input voltage U1, which is the strand voltage of the associated photovoltaic string 10 is. The output voltage sensor 48 is parallel to the output terminals 36a . 36b the strand box 20 is switched to measure the output voltage U2 which is the voltage at the inverter 26 is applied. In the case of a multi-stranded photovoltaic system, the output voltage U2 is the voltage that results from the parallel connection of all other photovoltaic strings to the inverter 26 is created. The current sensor 44 Measures the string current in the production plant, which in the case of electricity production of the photovoltaic string 10 in the normal direction, which is referred to herein as positive, through the string line 16 , the stringbox 20 and the continuation of the string line 17 into the inverter 26 flows to the inverter 26 to be fed. The current sensor 44 Optionally, it is also designed to provide a current flow in the reverse direction, ie one with respect to the normal current direction of the production of the photovoltaic string 10 negative current (ie reverse pole to the DC inputs 24a . 24b of the inverter). Alternatively, however, two separate current sensors may be provided, one for the positive current flow and one for the negative current flow (not shown). The switching device 38 is therefore, if desired, designed to measure positive and / or negative current flow.

In the basic position of the strand box 20 or the switching device 38 is the serial hybrid switch S1 open and is in its normal state (Normally Open). A major function of the serial hybrid switch S1 is to provide the current carrying connection of the associated photovoltaic string 10 to the inverter 26 to interrupt. A short-circuit switch S2 is used to make string-side shorts in the associated photovoltaic string 10 trigger and the photovoltaic modules 12 of the associated photovoltaic string 10 to activate via an impressed starting current. After sending the start pulse, the line voltage U1 and the inverter voltage U2 are measured and compared to determine the associated photovoltaic string in response to the voltage comparison 10 to the inverter 26 to switch on electrically, if necessary, if there is a corresponding user approval.

The serial hybrid switch S1 In this example, in response to a comparison of the strand voltage U1 and the inverter voltage U2 closed, ie the switching condition for the power-on of the serial hybrid switch S1 depends in this example on a comparison of the strand voltage U1 and the inverter voltage U2 from. The serial hybrid switch S1 in particular, closed only when the strand tension U1 of the associated photovoltaic string 10 either greater than the inverter voltage U2 or only by a predetermined threshold U0 (slightly) smaller than the inverter voltage U2 , In other words, a switching condition for the serial hybrid switch S1 for 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 safely switching on the associated photovoltaic string 10 to the inverter. The predefined and stored in the microcontroller switching value U0 is therefore (significantly) smaller than the maximum possible voltage of the associated photovoltaic string 10 , Only when such a switching condition, which of electrical characteristics of the associated photovoltaic string 10 and possibly the other photovoltaic strands depends, is met, controls the controller 42 the serial hybrid switch S1 such that the hybrid switch S1 is closed and thus the associated photovoltaic string 10 to the inverter 26 turns. Thus, in this particular embodiment, a system start of the associated photovoltaic string 10 even without the risk of the occurrence of unwanted backflow possible.

To unwanted return currents from the other present in this example photovoltaic strands in the associated photovoltaic string 10 in production, in which the serial hybrid switch S1 is closed, during the production operation, the current flow including the current flow direction is monitored. This is permanently a current measurement with the current sensor 44 carried out. By means of the current sensor 44 Therefore, a permanent monitoring of the string current performed, including the sign of the strand current, ie whether the strand current is negative. If the phase current should become negative, or a condition close to that is reached, the microcontroller will control 42 the serial hybrid switch S1 in that this opens and the current-carrying connection of the photovoltaic string 10 to the central collection point 22a . 22b and to the inverter 26 interrupts.

So that all strand boxes 20 the respective associated photovoltaic string 10 clean from the inverter 26 disconnect when the entire photovoltaic system 1 shuts down, are, preferably and if present, the serial hybrid switch S1 all switching devices 38 all photovoltaic strings also open as soon as the inverter voltage U2 is below a predefined minimum voltage U_min, where U_min may be in the range of about 30 volts, for example.

Referring to 3 and 4 includes the hybrid switch S1 a parallel circuit of a back-to-back circuit 50 of two semiconductor switches, in this example, two field effect transistors, more precisely two MOS FETs 52, and an electromechanical relay 54. The hybrid switch S1 as a whole, it is designed for the full nominal string voltage and the full nominal string current of the associated photovoltaic string 10, which are typically up to 1000 volts or even 1500 volts and, for example, 10 amperes. The MOS FETs 52, however, have a typical on-resistance, the so-called resistance-drain-source-on or RDS-on, in this example 690 mOhm. As a result, in the case of a typical photovoltaic string 10 on the MOS FETs 52, a power loss in the range of a few watts can arise. For example, with an RDS-on of 690 mOhm and a nominal phase current of I _nom = 10 A, a calculated power loss P _VL = RDS-on * (I _nom ) ² , ie in this example P _VL = 69 watts. Since such a power loss, in particular for installation in existing (plastic) housing is undesirable, the relay 54 relieves the back-to-back circuit 50 from the two MOS FETs 52 in continuous operation. That is, the turn-on is first performed by the back-to-back circuit of the two MOS FETs 52 and when the associated photovoltaic string 10 is in production for a certain minimum time, the parallel relay 54 is closed to the MOS FETs 52 relieve. This avoids, on the one hand, the permanent generation of high power dissipation at the MOS FETs 52 and, on the other hand, a relay 54 which alone would not be capable of switching at a nominal DC line voltage of 1000 V or even 1500 V without due The DC voltage would create an increased risk of a non-extinguishing arc.

The hybrid switch S1 can be built with commercially available, relatively small and inexpensive components despite the stringent requirements of nominal string voltage, nominal string current, and DC application.

• 1 Pol 16A,
• 1 Form A (NO) Kontakt (AgSnO2 or W pre-make contact + AgSnO2)
• mono- oder bistabile Spule
• 5kV/10mm Spulenkontakt
• verstärkte Isolation
• WG Version: Produkt gemäß IEC60335-1
• RTS3T: Elektronischer Ballast UL508/NEMA 410 bewertet
• RTS3T: 165/20ms Einschaltspitzenstrom

Kontaktdaten RT.3T RTS3L Kontaktanordnung 1 Form A (NO) Kontakt Nennspannung 250VAC Max. Schaltspannung 400VAC Nennstrom 16A Begrenzender Dauerstrom 16A, UL: 20A (RTS3L) Begrenzender Einschaltstrom, max. 20ms (Glühlampen) 165A peak 120A peak max. 200µs 800A peak Schaltleistung max. 4000VA Kontaktmaterial W (pre-make cont.) +AgSnO₂ AgSnO₂ Kontaktart pre-make contact single contact Betriebsfrequenz, mit/ohne Last 360/3600h^-1 Betriebs-/Auslösezeit max., DC Spule 10/5ms Betriebs-/Rückstellzeit max., bistable version 10/10ms Prellzeit max. 4ms For example, the RT.3T and RTS3L relays from TE Connectivity Ltd. (see www.te.com) with the following properties:

• 1 Pole 16A .
• 1 form A (NO) contact (AgSnO2 or W pre-make contact + AgSnO2)
• mono or bistable coil
• 5kV / 10mm coil contact
• reinforced insulation
• WG Version: Product according to IEC60335-1
• RTS3T: Electronic Ballast UL508 / NEMA 410 rated
• RTS3T: 165 / 20ms inrush current

contact details RT.3T RTS3L Contact configuration 1 form A (NO) contact nominal voltage 250VAC Max. switching voltage 400VAC current 16A Limiting continuous current 16A, UL: 20A (RTS3L) Limiting inrush current, Max. 20ms (incandescent) 165A peak 120A peak Max. 200μs 800A peak Switching capacity max. 4000VA Contact material W (pre-make cont.) + AgSnO ₂ AgSnO ₂ Contact type pre-make contact single contact Operating frequency, with / without load 360 / 3600h ^-1 Operating / tripping time max., DC coil 10 / 5ms Operating / reset time max., Bistable version 10 / 10ms bounce Max. 4ms

For the back-to-back circuit 50, for example, the STH12N120K5-2, STP12N120K5, STW12N120K5, or STWA12N120K5 MOSFETs from ST (see www.st.com) with the following properties have proved suitable: V _DS : 1200V RDS-on max. 690 mOhm I _D 12 A P _TOT 250 W V _GS Gate-source voltage ± 30V I _D Drain current at T _C = 25 ° C 12 A I _D Drain current at T _C = 100 ° C 7.6 A I _DM Drain current (pulsed) 48 A P _TOT Total dissipation at Tc = 25 ° C 250 W I _AR Max current during repeated or single pulse avalanche 4 A E _AS Single pulse avalanche energy 215 mJ dv / dt Acute diode reset voltage drop 4.5V / ns dv / dt MOSFET dv / dt insensitivity 50 V / ns

With such a hybrid circuit S1 consisting of the relay 54 and the MOSFET back-to-back circuit 50, and the associated control electronics, the photovoltaic string can be switched on and off safely and long term.

It is so by means of the hybrid switch S1 the current-carrying connection between the associated photovoltaic string 10 or the part of the DC generator connected thereto 2 and the central collection point 22a . 22b or the inverter 26 , in this example, even bidirectional, separated, ie it is a possible current flow, in this example in both directions, interrupted.

If the user initiates a trigger signal to switch off, which here with the test condition "U ext. Start = Off "is called, opens the controller 42 automatically the hybrid switch S1 ,

When switching off the photovoltaic string 10 First, the relay 54 and only with a time delay thereafter the back-to-back circuit 50 open to the associated photovoltaic string 10 from the central collection point 22a . 22b to separate. The time delay when switching on and / or off in this embodiment is about 200 ms to 300 ms, which is short enough not to overload the MOSFET back-to-back circuit 50/52 without special cooling.

Furthermore, the strand box 20 in the embodiment shown a memory 43 on, the control device 42 assigned and for storing a threshold is provided.

The string box 20 Optionally also an ambient temperature sensor 49a have, with which the ambient temperature is measured, for example, the influence of the ambient temperature on the strand voltage U1 capture.

4 shows the hybrid switch S1 with a drive circuit 60 for controlling the relay 54 and a more detailed illustration of MOSFET back-to-back 50/52.

At the control entrance 62 "Relay" receives the drive circuit 60 a standard signal ( 0 / 1 ) as a trigger signal from the controller 42 , A bipolar transistor 64 switches against earth 66 "GND". Parallel to the relay 54 is a freewheeling element for spark interruption, in this example, a freewheeling diode 68 connected. The gate voltage of the semiconductor switching device 50 or FET back-to-back circuit is potential-free against Source.

5 shows a switching power supply 70 for controlling the MOSFET back-to-back 50/52 circuit. About drain 72 flow up to 10 A. A clock 74 gives a 50/50 clock at about 200kHz to the switching transistors 76 , This part of the drive which generates the drive signal for the MOSFET back-to-back circuit 50/52 is galvanically isolated from the MOSFET back-to-back circuit 50/52. The galvanic isolation is done by means of a printed circuit board transformer 78 produced.

The diodes V17, C35, C36 provide the rectification and smoothing of the chopped voltage of 19.4 V.

Furthermore, the drive for MOSFET back-to-back circuit 50/52 includes an optocoupler 82 , which is a galvanic isolation from the control device 42 causes. About the control output 84 The drive signal is provided and the voltage of the power supply is via the optocoupler 82 to the MOSFET back-to-back circuit 50/52 turned on.

The connections gate 86 and Source 88 These are the MOSFET back-to-back circuits 50 / 52 are connected.

Referring to 6 runs a simple start, monitor and shutdown sequence of the switching device 38 for example, following.

At system startup at 102 is the photovoltaic string 10 . 10 ' from the pantograph 26 electrically isolated. The photovoltaic strand 10 is started by the associated photovoltaic modules 12 be electrically turned on, whereupon the strand tension U1 increases. The photovoltaic strand 10 becomes electric with the pantograph 26 connected.

In the operation of the photovoltaic string 10 , but possibly even before connecting the photovoltaic string 10 to the pantograph 26 , becomes the strand tension U1 in step 113 continuously, ie typically at fixed test intervals. The of the sensor device 46 , ie in particular the strand tension sensor 46 measured strand voltage U1 or a signal derived therefrom is sent to the control device 42 forwarded, which in the step 115 checks if the strand tension U1 below the threshold, ie below 1000 V DC in this example. If this is not the case, the operation continues and a next voltage measurement can take place in the specified test interval.

However, put the controller in step 115 determines that the electrical characteristic of the photovoltaic string 10 , so in particular the strand tension U1 , exceeds the threshold, a trigger signal for string shutdown is generated and to the switching device 38 output. It takes place in step 118 the strand shutdown. After switching off the photovoltaic string 10 from the pantographs 26 goes the photovoltaic system 1 in step 120 in the off state.

Referring to 7 runs the start and shutdown sequence of the switching device 38 with monitoring of the strand voltage, for example, as follows.

At system startup at 102 is the hybrid switch S1 in step 104 open (semiconductor switching device 50 and relays 54 open). In a query in step 106 it checks if the input voltage U1 a minimum voltage U_min1 falls below. If the condition U1 <U_min1, where in the present example U_min1 = 30 V DC, is fulfilled and the user release for starting (U ext. Start = on) is present, in the step 108 with the short-circuit switch S2 the starting pulses are triggered to the associated photovoltaic string 10 to start. The serial hybrid switch S1 remains open and the loop goes back to the crotch 104 ,

If now by the start pulses of the associated photovoltaic string 10 is started by the associated protection circuits 14 the associated photovoltaic modules 12 to the photovoltaic strand 10 have switched on electrically, should the strand voltage U1 significantly above the predefined minimum value U_min1 - if there is no error - and the associated photovoltaic string 10 not totally shadowed. So after the step 106 the condition U1 <U_min1 is no longer fulfilled under normal irradiation and without interference and the user release for starting (U ext. Start = on) is still present, another query is made in step 110 as to whether the input voltage U1 of the associated photovoltaic string 10 greater than or equal to the output voltage U2 of the associated photovoltaic string 10 minus a predefined threshold U0 is (U1> = U2- U0 ), in which U0 in this example is 20V DC, but could be zero. This condition should preferably be for a predefined minimum time t0 be fulfilled, which in this case t0 = 1s. Furthermore, it is checked again whether the voltage U1 greater than or equal to a minimum U_min2 is to ensure that the associated photovoltaic string 10 is still electrically connected, in which example U_min2 = 150 V DC. It is also checked again whether the user release (U ext. Start = on) is present. If at least one of these three test conditions in the query step 110 is not satisfied, the loop goes back to the step 104 and to the query 106 ,

However, all of these three test conditions are in the query 110 is met, in step 111 tested whether the strand current I is greater than a predefined threshold I_min, where I_min in this example is 500 mA (in the positive direction). If this test condition is not met, the microcontroller controls 42 in step 112a the serial hybrid switch S1 in such a way that initially only the semiconductor switching device 50 or back-to-back circuit closes. If this test condition I> I_min is met, the microcontroller controls 42 in step 112b the serial hybrid switch S1 in such a way that the back-to-back circuit 50 remains closed and now also the relay 54 closes. In both cases 112a . 112b becomes the associated photovoltaic string 10 to the central collection point 22a . 22b or the inverter 26 turned on and the associated photovoltaic string 10 feeds electrical power here via the central collection point 22a . 22b into the inverter 26 one, the hybrid switch S1 but only after closing the relay 54 in step 112b , ie in the state for the permanent production operation, works particularly low loss. In that the semiconductor switching device 50 or back-to-back circuit alone before in step 112a is closed, causes this routine in step 112b a time-delayed closing of the relay 54 only after a delay after closing the semiconductor switch back-to-back circuit 50 in step 112a , The time delay in the present example is about 200 ms to 300 ms, which is short enough not to overload the MOSFET back-to-back circuit 50, even though the full nominal phase current should flow.

The relay 54 assumes the current flow in this example only from I> 500 mA and only needs to switch a low voltage of typically 1 volt, so that a relatively small, inexpensive and in particular not designed for switching 1000 V DC relay can be used, such as the properties described above.

During the production operation is then in a test step 114 permanently or regularly checked, a) whether a negative current is greater than or equal to a predefined minimum value I_Reverse, 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) if the user release is not present (U ext. start = Off). The minimum I_Reverse for the negative current is typically in the milli-ampere range. In this example, the corresponding test condition is whether there is a negative current of at least 20 mA (I_Reverse <= - 20mA). As long as all three test results a), b), c) are negative, ie logically a) OR b) OR c) = NO, the hybrid switch becomes S1 kept closed.

Further, during the production operation, in a monitoring step 115 especially at regular test intervals the input voltage U1 from the sensor device 46 supervised. The measured voltage or a quantity derived therefrom is sent to the control device 42 which outputs this value with that in the memory area 43 the control device 42 stored threshold US compares. If the measured voltage is less than the threshold voltage, ie the test result d) also negative, the hybrid switch S1 kept closed.

Subsequently, another test step 116 carried out by interrogated in an error monitoring, whether the temperature is <130 ° C and whether the difference voltage between U1 and U2 greater than 2V. If this error check also fails, the loop becomes the test step 111 closed. The steps 111 - 116 thus form a permanent or continuous monitoring circuit for the associated photovoltaic string 10 as a result, even in production operation, no undesired values of the monitored electrical parameters occur.

If the query in step 114 shows that one of the three test conditions mentioned is positive, ie logically a) OR b) OR c) OR d) = YES, eg if there is an undesirably high negative reverse current, because, for example, the associated photovoltaic string 10 is significantly more shaded than the other photovoltaic strands, or because of the associated photovoltaic string 10 so far has lost strand voltage that the threshold condition U1 <U_min3 is met, or because the user-controlled shutdown request to the controller 42 is present (U ext. start = off) or the string voltage U1 is greater than the threshold voltage US, the loop goes back to the step 104 ie the hybrid switch S1 opens, leaving only the relay 54 is opened and only after a time delay, the semiconductor switching device 50 , Preferably, the hybrid switch S1 or both the mosfets 52 as well as the relay 54 designed as a normally open (normally open), so that the hybrid switch S1 as a whole automatically falls into the open state, if not the MOSFETs 52 and the relay 54 from the controller 42 in the closed state (loop 111 - 116 ) being held. Again, if necessary, the time delay is ensured. The loop 111 - 116 therefore represents the production operation of the associated photovoltaic string 10 ,

The user can in the step 114 by triggering the condition U ext. Start = Off, as desired in the loop 111 - 116 engage the current-carrying connection of the associated photovoltaic string 10 user-controlled by the inverter 26 to separate or the associated photovoltaic string 10 disable user-controlled. If so user controlled by triggering the condition U ext. Start = Off the query in the step 114 is set to "yes", the loop becomes 111 - 116 interrupted and the path of the test / control routine goes to the step 104 in which the hybrid switch S1 opens, even if all electrical parameters meet the predefined test conditions. The user therefore has the option of switching off the associated photovoltaic string 10 user-driven to trigger or trigger in its sole discretion. Again, if necessary, the time delay is ensured.

If the error monitoring in step 116 gives a positive result, ie if one of the two mentioned error conditions is true, is in one step 118 the hybrid switch S1 as in the step 114 opened and additionally the reporting output toggled, which gives an error message to the user. Subsequently, the cycle with the step 120 completed. This typically signals a fault.

If necessary, the monitoring with step 115 be so logically linked that exceeding the threshold voltage US in a positive result also with step 118 the message output is toggled and an error message is output for the user. This is useful, for example, in the context of the installation of the photovoltaic system, since in this case an overvoltage may rather be attributable to a faulty installation and an overvoltage in this case completely stops the operation of the photovoltaic system.

With the present invention, it is possible to anyone with such a switching device 38 Equipped started or in production operation located photovoltaic strand 10 user-controlled switch off, ie from the pantograph 26 to separate. This is done by means of the hybrid switch S1 from a parallel connection of a MOSFET back-to-back circuit 50 and a relay 54 and a corresponding control eg according to 7 accomplished.

The one in the strandbox 20 built-in hybrid switch S1 is capable of the photovoltaic strand 10 to separate and to prevent the flow of electricity. This causes the photovoltaic modules in the present example 12 built protection circuits 14 (eg Phoenix Contact SCK-RSD- 100 ) also turn off. In other words, in the present example, those on the photovoltaic modules then automatically deactivate 12 built protection circuits 14 and switch the individual photovoltaic modules 12 off, leaving the entire photovoltaic strand 10 not just electrically from the central collection point 22a . 22b is separated, but also no dangerous contact voltage leads more.

To start the photovoltaic string 10 be over the string line 16 Start pulses to the protective circuits 14 the photovoltaic modules 12 of the associated photovoltaic string 10 sent (step 108 ) to the unloaded photovoltaic strand 10 but not directly to the central collection point 22a . 22b to join. Thereafter, the check routine with steps 110 - 116 according to 7 carried out.

The present invention enables switching on and off of the at least one photovoltaic string 10 via a (module) higher-level control unit and represents an advantageous function for the customer, not only in an emergency, but also, for example, for maintenance purposes photovoltaic strings or entire areas of a DC generator 2 off.

In summary, with the present switching device 38 be switched on a small volume a large power with low power dissipation. The nominal power of the photovoltaic string is preferred 10 at least 10 kW, which from the hybrid switch S1 as a whole can be switched. The loss line of the hybrid switch S1 however, at nominal 1000 V and 10 A is less than or equal to 10 W, preferably less than or equal to 5 W, preferably less than or equal to 2 W, preferably less than or equal to 1 W, when the relay 54 the current commutes. The advantages of the different types of switching (electromechanical, semiconductor) are combined in a meaningful way. When switching the semiconductor switching device takes over 50 the first switching operation by up to 1000 V in possibly small load range (eg up to 500 mA) on and off again. Here is the important advantage of the semiconductor switching device with respect to the DC application 50 used to switch large voltages without sparking. After switching the semiconductor switching device 50 But then it is primarily about getting the power loss of the flowing stream under control. For this, the product parameters of a semiconductor are not ideal, because with increasing voltage at UBS, the internal leakage resistance RDS-on increases. For this purpose, the advantages of an electromechanical switch in the form of a relay 54 used. Although small-sized relays are not able to separate high DC voltages, large currents up to eg 16 amps are unproblematic.

When switched on, only the semiconductor switching device 50 , and then time-delayed, the relay is turned on 54. When switching off, this is correspondingly reversed, also with time delay. The relay 54 Thus, only switches on the remaining voltage across the semiconductor switching device both when switching on and when switching off 50 , or the MOSFETs 52 , commutes but due to the low Durchleitwiederstands almost the entire power. Thus, the switching device 38 suitable to switch 1000 V with 10 A DC / DC with low power loss. Thus, with the invention, a photovoltaic string 10 or parts of the DC generator 2 Size optimized and cost optimized controlled on and off.

It will be apparent to those skilled in the art that the above-described embodiments are to be read by way of example, and that the invention is not limited to them, but that they can be varied in many ways without departing from the scope of the claims. It is also to be understood that the features, independently as they are disclosed in the specification, claims, figures, or otherwise, also individually define essential components of the invention, even if described together with other features.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2013/026539 A1 [0006, 0106, 0113]
• WO 2014/122325 A1 [0006, 0052, 0106, 0115, 0116]
• DE 102016117049 [0007, 0009, 0067, 0093]
• WO 2016/091281 A1 [0013]
• WO 2013/026539 [0114]

Claims (15)

Photovoltaic system (1) comprising: at least one photovoltaic string (10), wherein the at least one photovoltaic string is formed by photovoltaic modules (12), which are connected in series with one another by means of a string line and thus generate a string voltage (U1), a sensor device (46) for measuring an electrical parameter of the photovoltaic string (10), in particular the string voltage (U1), a switching device (38), which is installed in the strand line, in order to switch on and off at least part of the photovoltaic system (1) or the at least one photovoltaic string with the switching device (38), a control device (42) which is designed to compare the electrical parameter with a predefined threshold value, in particular a threshold voltage, and to output a signal to the switching device (38) in response to the comparison, so that with the switching device (38) the at least a part of the photovoltaic system or the at least one photovoltaic string can be switched off. Photovoltaic system (1) according to Claim 1 , further comprising a further sensor device (49), in particular an ambient temperature sensor (49a) for measuring the ambient temperature of the photovoltaic system (1) or a module temperature sensor (49b) for measuring at least one module temperature of the photovoltaic modules (12), wherein the measurement signal of Sensor device is output to the control device and is evaluated by the control device with. Photovoltaic system (1) according to any one of the preceding claims, further comprising a control means (42) associated memory area (43) for storing the threshold value, wherein the control device is formed for the comparison of the electrical characteristic of the at least one photovoltaic strand (10 ) with the threshold value to access the memory area, wherein in particular the threshold stored in the memory area is variable by user input. Photovoltaic system (1) according to one of the preceding claims, wherein the switching device (38) comprises a hybrid switch (S1) with a relay (54) and a parallel to the relay (54) connected semiconductor switching device (50) with at least one semiconductor switch. Photovoltaic system (1) according to one of the preceding claims, wherein the hybrid switch (S1) defines a closed state and an open state, and in the closed state, passes photovoltaically generated power from the at least one photovoltaic string (10) to a current collector and, in the opened state, transmits photovoltaically generated current from the at least one Photovoltaic strand (10) interrupts, and wherein the control device (42) is designed in particular to automatically or automatically open the hybrid switch (S1) in response to the signal generated on the voltage comparison or to open the hybrid switch (S1) in a user-controlled manner in response to a user input. Photovoltaic system (1) according to one of the preceding claims, wherein the hybrid switch (S1) comprises a parallel connection of the relay (54) and a back-to-back circuit (50) of two semiconductor switches, in particular a parallel connection of a relay (54 ) and a back-to-back circuit (50) comprising two field-effect transistors, preferably MOSFETs (52). Photovoltaic system (1) according to one of the preceding claims, wherein the switching device (38), the control device (42) and the sensor device (46, 48) connected to the control device (42) for measuring the strand tension of the at least one associated photovoltaic strand (10) housed in a common switch housing. Photovoltaic system (1) according to one of the preceding claims, wherein the control device (42) is designed to electrically connect the associated photovoltaic line (10) to the current collector in response to the at least one electrical parameter measured by the sensor device (46, 48), in particular when the sensor device is present comprising: an input voltage sensor (46) measuring the line side input voltage (U1) on the switching device (38) and / or an output voltage sensor (48) measuring the output side voltage (U2) on the switching device (38), and wherein the control means (42) is adapted to electrically connect the associated photovoltaic string (10) to the central collection point (22a, b) in response to the measured line side input voltage (U1) and / or the measured current collector side output voltage (U2) User release exists. Photovoltaic system (1) according to one of the preceding claims, wherein the threshold value is a threshold voltage for the strand voltage of the at least one photovoltaic string (10), and wherein the threshold voltage is greater than or equal to 300 V, preferably greater than or equal to 600 V, preferably greater than or equal to 800 V, preferably 1250 V +/- 30%. Protection circuit formed for the DC part of a photovoltaic system (1), in particular according to one of the preceding claims, for switching off a part of the photovoltaic system or at least one photovoltaic string (10) of the photovoltaic system from a current collector (26), wherein the protection circuit comprises a sensor device (46, 48) for measuring an electrical parameter of the photovoltaic string (10), in particular the string voltage (U1), a switching device (38) which is installed in the string line, at least part of the photovoltaic system (1) or the at least one photovoltaic string with the switching device (38) by a pantograph on and off and a control device (42), which is designed to compare the electrical characteristic with a predefined threshold, in particular a threshold voltage, and in Response to the comparison to output a signal to the switching device (38), so that with the scarf teinrichtung (38) of the at least one part of the photovoltaic system or the at least one photovoltaic string can be switched off by the current collector comprises. Method for automatically switching off at least part of a photovoltaic system (1) or at least one photovoltaic line (10) of a photovoltaic system (1), in particular according to one of the preceding claims, wherein the at least one photovoltaic line is replaced by photovoltaic modules (12 ) is formed, which are connected in series with one another by means of a strand line and thus generate a strand voltage (U1), comprising the following steps: Defining a threshold value, in particular a threshold voltage, Measuring a current electrical parameter, in particular the string voltage, generated in the at least one photovoltaic string with a sensor device (46), Comparing the current electrical characteristic with the threshold, when the threshold is exceeded by the current electrical parameter automatic shutdown of the at least one photovoltaic string (10) or the part of the photovoltaic system (1) of the current collector (26). Method according to the preceding claim, wherein the automatic switching off of the at least one photovoltaic line (10) or of the part of the photovoltaic system (1) from the current collector (26) triggers (U ext. Start = off) a switching device (38). by a trigger signal from a control device (42). Method according to one of Claims 11 or 12 , wherein the defined threshold value is stored in a memory area (43) of a control device (42). Method according to one of Claims 11 to 13 , further comprising the step of triggering (U ext. start = On) the switching device (38) of the at least one photovoltaic string (10) by a trigger signal to the part of the photovoltaic system (1) or the at least one photovoltaic string ( 10) again to the pantograph (26) to turn on. Method according to one of Claims 11 to 14 additionally comprising the step of measuring the ambient temperature or the module temperature with the sensor means (49, 49a, 49b) and taking into account the measured ambient temperature or module temperature in comparing the current electrical characteristic with the threshold or when the part of the photovoltaic system or of the at least one photovoltaic string (10).

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