WO2011098235A2

WO2011098235A2 - Module bypass circuit for a photovoltaic module

Info

Publication number: WO2011098235A2
Application number: PCT/EP2011/000525
Authority: WO
Inventors: Bernard Frank
Original assignee: Wieland Electric Gmbh
Priority date: 2010-02-09
Filing date: 2011-02-04
Publication date: 2011-08-18
Also published as: DE102010007495A1; DE202011110074U1; WO2011098235A3

Abstract

The invention specifies a module bypass circuit (30) for a photovoltaic module (2). The module bypass circuit (30) comprises a bypass diode (33) and a switching element (46) connected in parallel therewith, and also a control circuit (64) which measures the diode voltage (Ud) present across the bypass diode (33) and which, in the event of an abrupt change in the diode voltage (Ud) which lies outside predefined limiting values, activates the switching element (46) by means of a trigger signal (A).

Description

description

Module bypass circuit for a photovoltaic module

The invention relates to a module bypass circuit for a photovoltaic module. The invention further relates to a module junction box or a module connector and a photovoltaic module, which are each provided with such a module bypass circuit.

Photovoltaic systems, which are suitable for generating alternating currents or high direct currents which are suitable in particular for feeding into the public power grid, are becoming increasingly widespread. Such photovoltaic systems are often mounted as so-called rooftop systems on rooftops.

A typical photovoltaic system comprises a plurality of (photovoltaic) modules, which are connected in series to achieve sufficiently high voltages in so-called strings. In general, a conventional photovoltaic system comprises a plurality of parallel strands, which are interconnected in a generator junction box. The generator junction box is followed by an inverter downstream of an inverter, which converts the DC generated by the modules initially in the characteristic of public power grids AC. Each module, in turn, is typically formed by a number of in-module solar cells connected in series.

As part of a photovoltaic system, the solar cells of each module, as well as powerful modules, individual subgroups of these solar cells, in each case a so-called bypass diode connected in anti-parallel. Thus, for example, three bypass diodes in series are connected in antiparallel in series to a conventional module with, for example, 36 solar cells, each of which in each case bridges a subgroup of solar cells comprising 12 solar cells. The or each bypass diode prevents an overloading of the respectively bridged solar cells in the event that one or more of these solar cells fails or is shaded, while the upstream or downstream solar cells are exposed and current pro- duce. Without the antiparallel bypass diode, a failed or shaded solar cell would be reverse biased by the surrounding cells. If a sufficient voltage is generated by the adjacent, functional solar cells in this state, this could lead to a breakthrough of the unserviceable or shaded solar cell without the bypass diode. This in turn can lead to the destruction of the module or even the creation of an arc with the associated risk of fire.

In the presence of the bypass diode, on the other hand, the current generated by the functional and irradiated solar cells can flow around the inoperable or shaded solar cell (s), so that an overloading of this solar cell (s) is avoided.

Due to the modules connected as part of a photovoltaic system, sufficient solar radiation usually generates considerable voltages and currents that can be fatal to humans. This is particularly problematic, especially since the modules of a photovoltaic system in a dangerous error, e.g. in case of a ground fault or a fire, can not be switched off easily. Rather, the photovoltaic modules constantly produce electricity as long as they are exposed. This can e.g. In a fire of a house equipped with a rooftop system, the extinguishing work considerably more difficult, if not impossible.

There are basically various protective measures for automatic shutdown of a photovoltaic system in case of failure provided. In particular, DE 10 2005 018 173 B4 discloses short-circuiting the photovoltaic system by means of a protective device interposed between the modules and the inverter. The short circuit is in this case by means of a thyristor, which maintains the short circuit after its ignition until the photovoltaic system with the onset of darkness is de-energized. If necessary, the thyristor is opened via a separate control line. WO 2009/073868 A1 discloses a further protective measure for a photovoltaic system in which each module is assigned a microcontroller-controlled circuit which continuously records a 100 Hz signal sent by the inverter into the DC voltage line of the photovoltaic system. This alternating signal superimposed on the direct current serves as a switching signal for the respective control modules associated with the individual modules, which switch off the output of the respective module as soon as the alternating signal fails.

The invention has for its object to provide a further improved, particularly particularly safe and reliable protective measure for a photovoltaic system, which eliminates the emergence of dangerous voltages and currents and the associated risk of injury and / or fire in the event of a fault.

This object is achieved by the features of claim 1. Thereafter, a module bypass circuit for a (photovoltaic) module is specified. The module bypass circuit comprises a bypass diode which is conventional per se, but in which a switching element is additionally connected in parallel. The module bypass circuit further comprises a control circuit which detects the diode voltage applied across the bypass diode and which then energizes (ie opens or, in other words, turns on) the switching element when the magnitude of the diode voltage jumps - in predetermined limits changes.

On the one hand, the invention is based on the consideration that the solar cells of a photovoltaic system should be short-circuited in the smallest possible units or subgroups in order to prevent the emergence of dangerous voltages or currents already in the approach. By according to the invention the already existing bypass diodes are supplemented by a switching device for short-circuiting the respective bridged solar cells, it is possible to short-circuit the modules of the photovoltaic system at least on a modular scale, but usually even on a submodular scale. Since the bypass diodes are already present in conventional photovoltaic modules or their junction boxes or plugs, the module bypass circuit can also be used. without having to change anything in the conventional design of a photovoltaic module.

The invention is further based on the consideration that the shutdown of a photovoltaic system by an external switching signal always carries a certain risk of error, e.g. as a result of faulty signal transmission, inaccessibility of the signal generator in the event of fire, etc. The invention therefore has the aim of creating a decentralized and independently operating protection device that is not dependent on external switching signals. The solution according to the invention is based on the knowledge that the voltages occurring during normal operation of a photovoltaic system, in particular the diode voltage dropping across each bypass diode, generally change only slowly over time. In particular, the ordinary fluctuation of solar radiation that generates these tensions, with the change of day and night and the change of the clouding state always takes place on comparatively long time scales of a few seconds, minutes or even hours.

On the other hand, as is known, a sudden change in the diode voltage has a high probability of an error state, so that time jumps in the magnitude of the diode voltage can advantageously be used as a trigger for short-circuiting the modules.

Unlike in the prior art, the short-circuiting of the photovoltaic modules is therefore generally not triggered by an external switching signal to be actively generated, but automatically by a typical symptom of a fault. Each of the module bypass circuits thus operates autonomously, whereby a particularly low risk of error is achieved. Advantageously, however, the module bypass circuit nevertheless offers the option of actively switching off the photovoltaic system. Thus, as is known, a voltage jump is actively generated by means of the inverter or a switching element arranged in the DC voltage path of the system, which simulates a fault and brings the or each module bypass circuit for triggering the short circuit. In a preferred embodiment of the module bypass circuit, the control circuit comprises a trigger element for generating the trigger signal. This triggering member expediently comprises a differentiator and a downstream comparator circuit. The differentiator, which is designed in the simplest case as an RC low-pass filter, serves to generate a change signal characteristic of the temporal change of the diode voltage. The downstream comparator circuit is preferably essentially formed by one or more comparators, in particular in the form of Schmitt triggers. The or each comparator or Schmitt trigger here compares the change signal with (each) a predetermined threshold signal and generates the trigger signal when the change signal exceeds this threshold signal (in the case of a positive change signal) or falls below (in the case of a negative change signal).

In addition to the circuit part which reacts to jumps in the diode voltage, the trigger element in an expedient embodiment of the module bypass circuit additionally comprises an overtemperature detection circuit. This circuit metrologically detects an ambient temperature or a measuring signal correlating therewith and triggers a switching signal if this ambient temperature exceeds a predetermined maximum value. The overtemperature detection circuit is in this case arranged in particular such that the ambient temperature detected by it corresponds at least approximately to the temperature of the associated photovoltaic module.

The overtemperature detection circuit improves the tripping safety of the module bypass circuit. In particular, the over-temperature detection circuit makes it possible in many cases to short-circuit the assigned module even before the occurrence of a critical fault, namely in particular when a failure of one or more solar cells is imminent due to overheating of solar cells, but has not yet occurred. The temperature-dependent tripping of the module bypass circuit also enables safe triggering of the module bypass circuit even with a module fire. In a preferred development of the invention, the control circuit additionally comprises a switching state memory which further maintains the once triggered trigger signal, so that the photovoltaic system is kept in the safe short-circuit state after the first triggering. The switching state memory is in this case formed in particular by an RS flip-flop.

In order to eliminate the short circuit, and to be able to easily restore the photovoltaic system in the event of a temporary error state back to the operable state, the control circuit in a preferred embodiment of the invention additionally comprises a reset element, through which the state memory a reset signal is supplied to the trigger signal break up.

In an expedient variant of the invention, the reset element comprises a dark phase detection filter which generates the reset signal when the diode voltage at least predominantly falls below a predetermined threshold value over a comparatively long period of time. The dark phase detection filter is formed, for example, by a capacitor circuit with a downstream comparator (for example Schmitt trigger), wherein the capacitor is gradually discharged via a resistor after dark, so that the comparator triggers when the capacitor voltage has dropped sufficiently. A "long period" in the sense of dark-phase detection is on the order of at least half an hour, but preferably the dark-phase detection filter is dimensioned so that the reset signal is only generated if the diode voltage remains stable for several hours, in particular 3 to 12 hours. lasting period predominantly falls below the threshold.

In order to be able to actively reset the photovoltaic system to the operative state, if necessary, the reset element preferably additionally or alternatively to the dark phase detection filter comprises a switching signal detection filter which generates the reset signal when the diode voltage falls below a predetermined threshold value in a predetermined manner Switching signal pattern corresponds. Expediently, a voltage limiter is provided in the context of the module bypass circuit parallel to the bypass diode as well as serially with the switching element, which in a simple and effective embodiment is preferably realized by a zener diode. The voltage limiter in this case has the effect that the diode voltage does not completely collapse even when the module bypass circuit is switched on. Rather, the diode voltage is maintained in the controlled state of the module bypass circuit by the voltage limiter at a constant, albeit small value. In terms of its forward voltage (when a Zener diode is also called a "Zener voltage"), the voltage limiter is dimensioned in such an advantageous manner that a sum voltage is present across the module bypass circuits intended to be connected one behind the other in a string of photovoltaic modules Safety Extra Low Voltage (SELV) according to protection class 3 in accordance with DIN EN 61140 (VDE 0140-1) The protective extra-low voltage is 50 V for direct currents.

The switching element of the module bypass circuit is preferably an electronic switching element, in particular a bipolar transistor or a field effect transistor, e.g. a MOSFET. In terms of rational production, the control circuit is expediently designed as an integrated circuit. In addition, the bypass diode and / or the switching element and / or (if present) the voltage limiter are preferably also integrated in this circuit. The module bypass circuit is preferably integrated in a module junction box or in a module connector with which a photovoltaic module is usually connected to the associated strand. Alternatively, the module bypass circuit can also be integrated in the photovoltaic module.

An embodiment of the invention will be described in more detail with reference to a drawing. Show: 1 is a schematic simplified diagram of a photovoltaic system with a number of arranged in three parallel strands photovoltaic modules, each module is connected by means of a module junction box to a strand line,

2 in a simplified circuit diagram in a more detailed representation of one of the photovoltaic modules and the module junction box, wherein the module junction box comprises three module bypass circuits,

3 is a simplified circuit diagram of the structure of one of the module bypass circuits of FIG. 2,

4 shows in a simplified circuit diagram a dark phase detection filter of the module bypass circuit, and

5 shows a simplified circuit diagram of a switching signal detection filter of the module bypass circuit.

Corresponding parts and sizes are always provided with the same reference numerals in all figures.

The (photovoltaic) system 1 shown in simplified form in FIG. 1 comprises a number of (photovoltaic) modules 2, a generator connection box 3, a separation point 4 and an inverter 5. The system 1 is in particular an on-roof system. Alternatively, the installation 1 can also be a building-integrated installation (for example façade-proof installation) or a field installation.

The modules 2 of Appendix 1 are divided into three groups (hereinafter referred to as strands 6a, 6b and 6c). The modules 2 assigned to a common strand 6a-6c are in each case connected in series with one another in an associated stranded line 7a, 7b and 7c. The connection of each module 2 to the associated strand line 7a, 7b or 7c in this case takes place in each case by means of a (modul lanschluss-) box 8, which is contacted with corresponding module connections (not explicitly shown).

The different strands 6a, 6b and 6c are connected in parallel with each other. The parallel connection of the strands 6a, 6b and 6c takes place here by the generator Connection box 3, in which the strand lines 7a-7c are brought together to form a common manifold 9. The bus 9 connects the generator junction box 3 via the separation point 4 with a DC input 10 of the inverter 5. A (here single phase trained) AC output 11 of the inverter 5 is connected by means of a feed line 12 with two phases 13 of a three-phase power network 14.

Each of the modules 2 is formed according to FIG. 2 by a number of (here by way of example 36) solar cells 20. The solar cells 20 of each module 2 are connected inside the module via a series line 21 in series. On the anode side, the row line 21 contacts the socket 8 in a module input contact 22 and on the cathode side in a module output contact 23. In each case after one third of the series connection formed along the row line 21, i. in each case after twelve series-connected solar cells 20, the row line 21 is also contacted via a respective branch line 24 and 25 with a first branch contact 26 and a second branch contact 27. Within the box 8 are the module input contact

22 and the first branch contact 26, the first branch contact 26 and the second branch contact 27 and the second branch contact 27 and the module output contact

23 are each connected via a module bypass circuit 30. The module input contact 22 and the module output contact 23 are further connected via a respective associated strand terminal contact 31 in the strand line 7a, 7b or 7c.

Through the branch lines 24 and 25, the solar cells 20 of the module 2 are subdivided into three subgroups 32a, 32b and 32c of twelve solar cells 20, wherein the solar cells 20 of a common subgroup 32a, 32b or 32c are bridged via the respectively associated module bypass circuit 30.

According to FIG. 3, each of the module bypass circuits 30 comprises a bypass diode 33, which is connected in anti-parallel to the series-connected solar cells 20 of the associated subgroups 32a-32c, and thus in reverse direction against the potential gradient prevailing in the series line 21 as intended. In parallel connection to the diode 33, the module bypass circuit 30 comprises a differentiator 34, which is formed in the simplest form by an RC element. The differentiator 34 is connected on the output side to two parallel Schmitt triggers 35 and 36.

Another Schmitt trigger 37 is connected on the input side to a temperature detection circuit 38, which in turn is formed of a voltage divider with a temperature-dependent resistor 39 and an ordinary resistor 40 with weak or vanishing temperature dependence and a constant voltage source 41. The constant voltage source 41 is hereby replaced by a capacitor circuit, not shown, with an associated voltage limiter, which is fed from the series line 21. In summary, the temperature detection circuit 38 with the downstream Schmitt trigger 37 form an overtemperature detection circuit.

The outputs of the Schmitt triggers 35, 36 and 37 are combined in an OR gate 42. The Schmitt triggers 35,36 and 37, together with the differentiator 34, the temperature detection circuit 38 and the OR gate 42, a trigger member 43 of the module bypass circuit 30th

The output of the OR gate 42 is connected to the setting input (S) of an RS flip-flop 44, which acts as a switching state memory in the context of the module bypass circuit 30. The non-inverting output (Q) of the RS flip-flop 44 is connected via a resistor 45 to the base of an (npn) transistor 46, which serves as a switching element for bypassing the bypass diode 33 in the context of the module bypass circuit 30. The transistor 46 is connected in parallel with the diode 33. In series with the transistor 46, but in parallel with the diode 33, the transistor 46, a resistor 47 and a Zener diode 48 are connected upstream.

In addition to the trigger member 43, the module bypass circuit 30 comprises a reset member 49, which is essentially constituted by a (dark phase detection) Filter 50 and a parallel switched (switching signal detection) filter 51 and another OR gate 52 is formed.

The dark phase detection filter 50 and the switching signal detection filter 51 are each connected on the input side in parallel with the diode 33. The outputs of the two filters 50 and 51 are connected via the OR gate 52 to the reset input (R) of the RS flip-flop. The switching signal detection filter 51 is optionally additionally connected to the non-inverting output (Q) of the RS flip-flop 44.

The dark phase detection filter 50 comprises in a preferred embodiment of the Modülbypassschaltung 30 shown in FIG. 4, a capacitor 53 which is connected in parallel with the diode 33. The capacitor 53, a charging resistor 54 and a diode 55 are connected upstream. In this case, the diode 55 is connected in the forward direction into the potential gradient which is applied as a rule in the forward direction, and is thus poled in the opposite direction to the bypass diode 33. In parallel to the capacitor 53, the filter 50 comprises a discharge resistor 56. The filter 50 further includes a Schmitt trigger 58, which is the input side connected to a capacitor 53 and the charging resistor 54 intermediate tap 57. The output of the Schmitt trigger 58 is connected via a monostable multivibrator 59 to an input of the OR gate 52 (FIG. 3), and via this to the reset input (R) of the RS flip-flop 44.

The switching signal detection filter 51 comprises, as shown in FIG. 5, a window comparator 60 connected in parallel with the bypass diode 33. The output of the window comparator 60 is connected to an input of an AND gate 61 whose second input is connected to the non-inverting output (Q) of the RS Flip-flops 44 is connected. The output of the AND gate 61 is connected to the OR gate 52 (FIG. 3) via a pulse train filter 62 and a monostable multivibrator 63 downstream of it, and via this to the resetting input (R) of the RS flip-flop 44. The trigger member 43 and the reset member 49, together with the RS flip-flop 44 and the downstream resistor 45, a control circuit 64 of the module bypass circuit 30. The electronic components of the control circuit 64 via a fed from the row line 21 capacitor circuit (not explicitly shown) with supplied the required operating voltage. The control circuit 64 is combined with the transistor 46 and the bypass diode 33 in an integrated circuit.

Under solar irradiation, the modules 2 generate a DC voltage which is applied to the inverter 5 via the generator connection box 3 and the separation point 4. The strands 7a-7c together with the bus 9 form a direct current path of the plant 1. Under ordinary and homogeneous homogeneous solar radiation, for example, in each strand 6a, 6b and 6c a direct current with a voltage amount of e.g. 800V and a current of, for example, about 10A generated. The bus 9 thus carries a direct current of 800V and 30A.

The inverter 5 converts this direct current into a grid-compatible alternating current, which is fed via the alternating voltage output 11 and the feed line 12 into the power grid 14.

In a normal mode of operation of the module bypass circuits 30, the bypass diode 33 is reverse biased when the transistor 46 is off (i.e., off). The diode 33 is thus energized in this case, so that above the diode 33, a diode voltage Ud drops, which corresponds to the voltage generated by the solar cell 20 voltage swing.

The differentiator 34 detects this diode voltage Ud and outputs on the output side a change signal D to the downstream Schmitt triggers 35 and 36. The Schmitt triggers 35 and 36 act as a comparator circuit within the module bypass circuit 30. The Schmitt trigger 35 compares the change signal D here with a predetermined positive threshold value, while the Schmitt trigger 35 compares the change signal D with a predetermined positive threshold value. mitt-trigger 36, the change signal D with a predetermined negative

Threshold compares.

In normal operation of the system 1, the diode voltage Ud depends on the temporal fluctuation of the incident sunlight. As a rule, it is only subject to a slight change over time, especially since the intensity of the incident sunlight, e.g. During the day-night transition or a change in the clouding condition, changes usually only slowly, especially on a scale of a few seconds to minutes, significantly. Significant voltage jumps, in particular temporal changes of the diode voltage Ud with voltage swings of several percent of the diode voltage Ud on the time scale of a few milliseconds, on the other hand, generally do not occur in the fault-free operation of the photovoltaic system 1. Rather, such voltage jumps typically occur only in the case of a fault, in particular in the case of a ground fault or when an arc occurs.

This circumstance is exploited by the Schmitt triggers 35 and 36. As long as the diode voltage Ud in the normal operation of the system 1 is only slightly variable in time, the change signal D has only a comparatively small amount. In the case of a pronounced jump in the diode voltage Ud, on the other hand, the change signal D briefly assumes high positive values (in the case of a sudden increase in the diode voltage Ud) or negative values (in the case of a sudden drop in the diode voltage Ud). The threshold values given to the Schmitt triggers 35 and 36 are now dimensioned such that one of the two Schmitt triggers 35 or 36 triggers, i. a positive trigger signal A outputs when the diode voltage Ud has a sudden change in time of predetermined size, for example, a voltage jump of more than 5% of the diode voltage Ud within 10 msec.

As soon as one of the Schmitt triggers 35,36 triggers, and the output of the OR gate 42 is turned on, and thus the trigger signal A to the setting input (S) of the RS flip-flop 44 out. The RS flip-flop 44 then turns on its non-inverting output (Q), so that the trigger signal A via the resistor 45 is switched to the base of the transistor 46, and the transistor 46 aufsteuert.

By controlling the transistor 46, the bypass diode 33 is bridged low resistance, so that the bridged by the bypass diode 33 solar cells 20 of the respective sub-group 32a-32c are short-circuited.

The control of one of the module bypass circuits 30 of the system 1 in turn triggers a voltage jump in the series line 21, which causes the triggering of adjacent module bypass circuits 30. A single, sufficient voltage jump in the series line 21 of a module 2 thus brings about all module bypass circuits 30 in the manner of a chain reaction, so that in a final state, all modules 2 of the system 1 on the order of the subgroups 32a, 32b and 32c, and thus submodular Scale, shorted. The ruling in the strand lines 7a, 7b and 7c and the manifold 9 DC voltage thus largely comes to a standstill. This process, which is also referred to below as the "emergency shutdown" of system 1, can also be triggered by a switching device which generates a voltage jump in this line 7a-7c by blocking one of the line leads 7a-7c One or more such switching devices are Optionally, such switchgear can be triggered manually or by a wired or wireless signal, and one or more of these switching devices can also be designed as thermal switches or smoke detectors to provide emergency shutdown in case of fire.

A triggering principle independent thereof, the temperature detection circuit 38 follows in combination with the Schmitt trigger 37. The operating principle of this circuit based on the fact that (hereinafter referred to as temperature signal T) voltage applied to the center tap of the voltage divider formed by the resistors 39 and 40, is due to the temperature dependence of the resistor 39 changes with changing temperature. Depending on the Characteristic characteristic of the resistor 39 exceeds or falls below the temperature signal T a Schmitt trigger 37 predetermined limit when the prevailing at the location of the resistor 39 ambient temperature exceeds a predetermined maximum value, for example 150 ° C. Since the module junction box 8 and the module bypass circuits 30 integrated therein lie directly against the module 2, the detected ambient temperature corresponds approximately to the temperature of the respective associated module 2.

When exceeding the maximum temperature of the Schmitt trigger 37 thus triggers and outputs the trigger signal A via the OR gate 42 to the setting input (S) of the RS flip-flop 44. In this way, the transistor 46 is turned on, which in turn - like described above - the emergency shutdown of Appendix 1 is initiated.

Instead of the temperature detection circuit 38 with the downstream Schmitt trigger 37, a thermal switch may also be provided in the row line 21, which opens when the maximum temperature is exceeded and thus generates a voltage jump triggering the module bypass circuit 30.

The zener diode 48, when the transistor 46 is turned on, ensures that the diode voltage Ud does not drop to zero. Rather, the diode voltage Ud with transistor 46 turned on has a substantially equivalent amount of zener voltage, e.g. 1, 5 volts.

The zener diode 48 is selected with regard to its Zener voltage such that in total across the module bypass circuits 30 connected in series in each of the strings 6a, 6b and 6c there is a voltage which is always lower than the protective extra-low voltage (SELV), i. is less than 50 volts.

The RS flip-flop 44 acts as a switching state memory by still maintaining the trigger signal A when the triggered Schmitt trigger 35, 36 or 37 switches back. Thus, the system 1 remains in safe short-circuit condition, even if the triggering condition, eg an overtemperature in one the modules 2, no longer exists. The reset element 49 assigned to each module bypass circuit 30 serves to switch the module bypass circuits 30 back into the normal operating mode, and thus to restore the system 1 to the functional state.

By means of the dark phase detection filter 50, the reset is automatically initiated when the modules 2 are left for a long time, e.g. exposed to sunlight for more than 4 hours. During such a dark phase, typically during the night, the diode voltage Ud regularly returns to a negligible value. The capacitor 53 of the dark phase detection filter 50, which was charged during a previous phase of operation of the system 1 via the diode 55 and the charging resistor 54 is therefore gradually discharged during the dark phase on the high impedance discharge resistor 56. As soon as the capacitor voltage Uc applied across the capacitor 53 falls below a predetermined threshold value, the Schmitt trigger 58 triggers and outputs a reset signal R via the monostable multivibrator 59 improving the signal characteristic and the OR gate 52 to the reset input (R) of the RS Flip-flop 44, which then breaks off the trigger signal A output via the non-inverting output (Q) and thus blocks the transistor 46 again. The resetting of the module bypass circuits 30 by the respective dark phase detection filter 50 has the consequence that the system 1 returns to normal after the night following an emergency shutdown at dawn.

The switching signal detection filter 51 of the reset element 49, on the other hand, allows the module bypass circuits 30 to be reset to the normal operating mode by an external switching signal by significantly reducing the diode voltage Ud below the value corresponding to the Zener voltage of the diode 48 in accordance with a predetermined switching signal pattern. By way of example, this switching signal pattern is predetermined as a three-pulse sequence, in the course of which the diode voltage Ud is lowered three times in succession for the duration of one second in each case with interpulse intervals of two seconds. The lowering of the diode voltage is preferably carried out by temporarily shorting the bus 9 by means of the inverter 5 or by a separate short circuit, which may be integrated, for example, in the generator junction box 3 or elsewhere in the wiring.

The threshold values of the window comparator 60 of the filter 51 are selected with predetermined tolerance above and below the zener voltage of the diode 48. With the transistor 46 turned on, the window comparator 60 is therefore turned on in the normal state, i. outputs a HIGH level or, in other words, a logical one value. By the externally controlled lowering of the diode voltage Ud and the window comparator 60 is switched, especially in this case, the diode voltage Ud drops below the lower threshold of the window comparator 60. The window comparator 60 thus outputs the external switching signal as a digital pulse train signal P to an input of the AND gate 61. The trigger signal A is connected to the other input of the AND gate 61. Therefore, the AND gate 61 passes the pulse train signal P only when the transistor 46 is turned on. In the normal operating mode, and thus in the absence of the trigger signal A, the AND gate 61 blocks it.

By means of the downstream pulse sequence filter 62, the pulse train signal P supplied by the AND gate 61 is then checked as to whether it corresponds to the predetermined switching signal pattern. As soon as the pulse sequence filter 62 recognizes the switching signal pattern, it outputs the reset setting signal R, which in turn is connected to the reset input (R) of the RS flip-flop 44 via the monostable flip-flop 63 and the OR gate 52 for resetting the module bypass circuit 30.

LIST OF REFERENCE NUMBERS

1 (potovoltage) plant

2 (photovoltaic) module

3 generator connection box

4 separation point

5 inverters

6a-6c strand

7a-7c string line

8 (module connection) box

9 manifold

10 DC input

11 AC output

13 phase

14 power grid

20 solar cell

21 row line

22 module input contact

23 module output contact

24 branch line

25 branch line

26 branch contact

27 branch contact

30 Module bypass circuit

31 line contact

32a-32c subgroup

33 bypass diode

34 differentiators

35 Schmitt triggers

36 Schmitt triggers

37 Schmitt triggers

38 temperature detection circuit

39 resistance resistance

Constant voltage source

OR gate

trigger member

RS flip-flop

resistance

transistor

resistance

Zener diode

Reset portion

(Dunkelphasenerkennungs-) filter

(Schaltsignalerkennungs-) filter

OR gate

capacitor

load resistance

diode

discharge

center tap

Schmitt trigger

(monostable) flip-flop

window

And gate

Pulse sequence filters

(monostable) flip-flop

Control circuit

trigger signal

change signal

Pulse train signal

Reset signal

temperature signal

capacitor voltage

diode voltage

Claims

claims

1. Module bypass circuit (30) for a photovoltaic module (2), with a bypass diode (33) and a parallel to this switching element (46), as well as with a control circuit (64), the over the bypass diode (33) applied diode voltage (Ud) detects, and the switching element (46) aufsteuert at a predetermined outside predetermined limits abrupt change of the diode voltage (Ud) by means of a trigger signal (A).

2. module bypass circuit (30) according to claim 1,

wherein the control circuit (64) comprises a trigger element (43) with a differentiator (34) and a downstream comparator circuit (35,36), wherein the differentiator (34) generates a for the temporal change of the diode voltage (Ud) characteristic change signal (D) , and wherein the comparator circuit (35,36) compares this change signal (D) with at least one predetermined threshold value and generates the trigger signal (A) when the threshold value is exceeded or undershot.

3. module bypass circuit (30) according to claim 2,

wherein the trigger member (43) additionally comprises an overtemperature detection circuit (37, 38) detecting an ambient temperature and which triggers the triggering signal (A) when the ambient temperature exceeds a predetermined maximum value.

4. Module bypass circuit (30) according to one of claims 1 to 3,

wherein the control circuit (64) comprises a switching state memory (44) and a reset element (49), wherein the switching state memory (44) the generated trigger signal (A) until the generation of a reset signal (R) by the reset member (49) upright.

5. module bypass circuit (30) according to claim 4,

wherein the reset member (49) comprises a dark phase detection filter (50) which generates the reset signal (R) when the diode voltage (Ud) at least predominantly falls below a predetermined threshold value over a comparatively long period of time.

6. module bypass circuit (30) according to claim 4 or 5,

wherein the reset member (49) comprises a switching signal detection filter (51) which generates the reset signal (R) when the diode voltage (Ud) falls below a predetermined limit in a manner corresponding to a predetermined switching signal pattern.

7. module bypass circuit (30) according to one of claims 1 to 6,

with a voltage limiter (48) connected in parallel to the bypass diode (33) and serially connected to the switching element (46), in particular in the form of a Zener diode.

8. module bypass circuit (30) according to one of claims 1 to 7,

wherein the switching element (46) is an electronic switching element, in particular a bipolar transistor or a field effect transistor.

9. module bypass circuit (30) according to one of claims 1 to 8,

wherein the control circuit (64) is formed as an integrated circuit.

10. Module junction box (8) or module connector for connecting a photovoltaic module (2), with an integrated module bypass circuit (30) according to one of claims 1 to 9.

11. Photovoltaic module (2) with an integrated module bypass circuit (30) according to one of claims 1 to 9.