Method and device for detecting faulty connection of photovoltaic module

Abstract

A method and apparatus for detecting a faulty installation of a photovoltaic module (5) equipped with an associated module level shut-off device MLSD (3) connected in series as a chain to a string loop interface of a detector device (2) within a string (1) of photovoltaic modules, wherein the method comprises the steps of: sending (S1), by the detector device (2), an operation permission (PTO) signal via its loop serial interface to a chain of serially connected module level shut-off devices (MLSDs) of the string of photovoltaic modules (1) using a power line communication PLC, and sending (S2), by the detector device (2), an operation permission (PTO) signal via its loop serial interface to the chain of serially connected module level shut-off devices (MLSDs) of the string of photovoltaic modules (1); capturing (S2), by the detector device (2), as a result of an on-state transient generated by the module level shut-off device MLSD (3) in response to an operation permission PTO signal received by the chain of series-connected module level shut-off devices MLSD (3) from the loop serial interface of the detector device (2), a string voltage waveform provided by the chain of serially connected module level shut-off devices MLSD (3) of the string of photovoltaic modules (1) to the loop string interface of the detector device (2), wherein an opening delay of the resulting opening transient is distributed over a predefined maximum delay period; and analyzing (S3), by the detector device (2), the captured string voltage waveform Vstr provided by the chain of serially connected module level shutoff devices MLSD (3) of the string of photovoltaic modules (1) to determine the number N of photovoltaic modules (5) correctly installed within the string of photovoltaic modules (1) and associated module level shutoff devices MLSD (3) within the string of photovoltaic modules (1).

Description

[0001] The invention relates to a method and a device for detecting a faulty connection of a photovoltaic module equipped with a module-level shut-off device by means of a detector device connected to the module-level shut-off device.

[0002] A photovoltaic system may include one or more photovoltaic module (PVM) strings within a photovoltaic array. The photovoltaic array may be connected to an inverter via a DC line for converting a DC current received from the photovoltaic array into an AC current. Each photovoltaic module of the photovoltaic module string may include an associated module-level shutdown device (MLSD) for monitoring and / or controlling the associated photovoltaic module via, for example, a power line connecting a base station of the module-level shutdown system to the module-level shutdown device.

[0003] Figure 1 The invention shows a photovoltaic module PVM including a predetermined number N. i In a conventional system, each photovoltaic module has an associated module-level shutdown device MLSD. The module-level shutdown device MLSD is connected in series via a DC cable to a test device that can be used to test the functionality of the photovoltaic module string. The device can be connected by Figure 1 The power line communication PLC shown communicates with the module level shutdown device MLSD. Figure 1 During the installation of the photovoltaic system shown, it may be useful to check the number N of photovoltaic modules PVM that are operating normally in the photovoltaic module string. The open circuit voltage V oc To calculate the number of photovoltaic modules N. For example, the measured string voltage V str can be divided by the open circuit voltage V oc To determine the number of photovoltaic modules in a photovoltaic module string.

[0004] However, the open circuit voltage V oc The difficulty lies in the open circuit voltage V oc The photovoltaic module PVM varies depending on the module type, temperature, sunlight, etc. For example, since the measured value V str = 480V may correspond to 37V oc The 13 photovoltaic modules PVM or each with 34V oc The 14 PV modules PVM are identical, so it is difficult to tell whether all PV modules PVM have been correctly connected. Therefore, using conventional methods, it is impossible to verify whether all PV modules PVM and their associated module-level shutdown devices MLSD within a PV module string have been correctly installed, especially since the open-circuit voltage V oc uncertainty.

[0005] It is therefore an object of the present invention to provide a method and a device for reliably detecting a faulty connection of a photovoltaic module within a photovoltaic module string.

[0006] According to a first aspect of the invention, this object is achieved by a method for detecting a faulty connection of a photovoltaic module, the method comprising the features of claim 1 .

[0007] According to a first aspect, the invention provides a method for detecting a faulty installation of a photovoltaic module provided with an associated module level shutdown device MLSD connected in series within a photovoltaic module string to a string loop interface of a detector device, wherein the method comprises the following steps:

[0008] The detector device sends an operation permission PTO signal to the chain of serially connected module-level shutdown devices MLSD of the photovoltaic module string through its string loop interface using power line communication PLC;

[0009] capturing, by the detector device, a string voltage waveform applied by the chain of series-connected module-level shutdown devices MLSD of the photovoltaic module string to the string loop interface of the detector device as a result of a turn-on transient generated by the module-level shutdown device MLSD in response to an operation permissive PTO signal received by the chain of series-connected module-level shutdown devices MLSD from the string loop interface of the detector device, wherein a turn-on delay of the generated turn-on transient is spread over a predefined maximum delay time period; and

[0010] The captured string voltage waveform provided by the chain of serially connected module level shutdown devices MLSD of the photovoltaic module string is analyzed by the detector device to determine the number N of photovoltaic modules and associated module level shutdown devices MLSD correctly installed in the photovoltaic module string.

[0011] In a possible embodiment of the method according to the first aspect of the invention, the turn-on transients generated by the module-level shutdown device MLSD of the photovoltaic module string are randomly distributed within the predefined maximum delay time period.

[0012] In a further possible embodiment of the method according to the first aspect of the invention, said detector device connected to the chain of series connected module level shutdown devices MLSD of said string of photovoltaic modules is implemented in an inverter device.

[0013] In an alternative embodiment of the method according to the first aspect of the invention, said detector device connected to the chain of series-connected module-level shutdown devices MLSD of said photovoltaic module string is implemented in a testing device for testing said photovoltaic module string.

[0014] In another possible embodiment of the method according to the first aspect of the present invention, the captured string voltage waveform provided by the photovoltaic module string is analyzed in the time domain by a processing unit of the detector device.

[0015] In another possible embodiment of the method according to the first aspect of the present invention, the captured string voltage waveform provided by the photovoltaic module string is analyzed in the frequency domain after signal transformation by the processing unit of the detector device.

[0016] In another possible embodiment of the method according to the first aspect of the present invention, the captured string voltage waveform comprises a stepped string voltage applied to the string loop interface of the detector device of the chain of module-level shutdown devices connected in series to the photovoltaic module PVM string, and is converted by an analog-to-digital converter ADC of a data acquisition unit of the detector device at a specific sampling rate SR into a digital signal comprising string voltage data samples stored in a data memory of the data acquisition unit of the detector device.

[0017] In a further possible embodiment of the method according to the first aspect of the invention, a sample histogram h is derived by the processing unit of the detector device from the string voltage data samples stored in the data memory of the data acquisition unit of the detector device.

[0018] In another possible embodiment of the method according to the first aspect of the invention, the sample histogram h is derived from stored string voltage data samples by repeatedly counting the string voltage data samples having the (substantially) same constant string voltage applied to the string loop interface of the detector device by the chain of module-level shutdown devices MLSD connected in series of the photovoltaic module string for the entire string voltage waveform, the detector device being connected in a closed loop to the chain of module-level shutdown devices connected in series of the photovoltaic module string.

[0019] In another possible embodiment of the method according to the first aspect of the invention, the processing unit of the detector device performs a discrete Fourier transform DFT on the histogram h of the string voltage data samples to calculate a spectrum H of the sample histogram h in the frequency domain.

[0020] In another possible embodiment of the method according to the first aspect of the present invention, the number of periods between peaks in the calculated sample histogram h, which corresponds to the number of voltage steps in the stepped string voltage waveform provided by the photovoltaic modules of the photovoltaic module string to the string loop interface of the detector device connected to the photovoltaic module string, indicates the number of correctly installed photovoltaic modules within the photovoltaic module string.

[0021] The average open circuit voltage V of the photovoltaic module correctly installed in the photovoltaic module string can also be determined. oc , to investigate the health status of the corresponding PV module strings.

[0022] In another possible embodiment of the method according to the first aspect of the invention, the DFT index at the maximum peak within the calculated histogram spectrum H derived by the processing unit of the detector device indicates the number N of photovoltaic modules and associated module-level shutdown devices MLSD correctly installed in the photovoltaic module string.

[0023] In another possible embodiment of the method according to the first aspect of the invention, a comparator of the processing unit of the detector device compares the determined number N of photovoltaic modules and associated module-level shutdown devices MLSD correctly installed in the photovoltaic module string with a predefined set number N of photovoltaic modules. set A comparison is performed to verify that all photovoltaic modules and associated module level shutdown devices MLSD have been properly installed to the string loop interface of the detector device.

[0024] In a further possible embodiment of the method according to the first aspect of the invention, if the number N of photovoltaic modules and associated module-level shut-off devices MLSD correctly installed in the photovoltaic module string and correctly connected to the detector device is less than the predefined set number N set , countermeasures are automatically triggered by the controller of the detector device.

[0025] In a further possible embodiment of the method according to the first aspect of the invention, if the number N of photovoltaic modules and associated module-level shut-off devices MLSD correctly installed in the photovoltaic module string and correctly connected to the detector device is less than the predefined set number N set , the module-level shutdown device MLSD of the photovoltaic module string is turned off by stopping the operation permission PTO signal, and is turned on again by sending the operation permission PTO signal again, so as to repeat the detection process.

[0026] In another possible embodiment of the method according to the first aspect of the invention, the operation permission PTO signal is a periodic signal sent by a signal sending unit of the detector device through power line communication PLC in a downlink channel, and the detector device is connected to a chain of module-level shutdown devices MLSD connected in series of the photovoltaic module string via a pair of DC cables.

[0027] In another possible embodiment of the method according to the first aspect of the present invention, the operation permission PTO signal includes an encoded address to individually activate the associated module-level shutdown device MLSD of the photovoltaic module string, and triggers the generation of a corresponding start-up transient in response to the received power line communication PLC operation permission PTO signal to individually turn on the photovoltaic module connected to the addressed module-level shutdown device MLSD.

[0028] According to another aspect, the invention provides a detector arrangement comprising the features of claim 12 .

[0029] According to a second aspect, the invention provides a detector device having a string loop interface connected to a chain of series connected module level shutdown devices MLSD of a string of photovoltaic modules, the detector device comprising means for performing the method according to the first aspect of the invention.

[0030] In a possible embodiment of the detector device according to the second aspect of the invention, the detector device comprises:

[0031] a signal sending unit for sending an operation permission PTO signal to a chain of serially connected module level shutdown devices MLSD of the photovoltaic module string by means of a power line communication PLC through a string loop interface of the detector device;

[0032] a signal capture unit for capturing a string voltage waveform as a result of a turn-on transient step generated by a chain of serially connected module-level shut-off devices MLSD of the photovoltaic module string in response to a received operation permissive PTO signal, the string voltage waveform being provided by the chain of serially connected module-level shut-off devices MLSD of the photovoltaic module string to the string loop interface of the detector device, wherein a turn-on delay of the turn-on transient is distributed within a predefined maximum delay time period; and

[0033] A processing unit for analyzing a captured string voltage waveform provided to the string loop interface of the detector device by a chain of serially connected module-level shutdown devices MLSD of the photovoltaic module string to determine the number N of photovoltaic modules and associated module-level shutdown devices MLSD correctly installed in the photovoltaic module string.

[0034] In another possible embodiment of the detector device according to the second aspect of the invention, the detector device further comprises a user interface and / or a control interface for signaling a faulty installation or a fault-free installation of photovoltaic modules and associated module level shutdown devices MLSD within the photovoltaic module string.

[0035] According to another aspect, the present invention also provides a module level shutdown device MLSD for a photovoltaic module string comprising the features of claim 15 .

[0036] According to a third aspect, the present invention provides a module-level shutdown device MLSD for a photovoltaic module string, comprising:

[0037] a first interface, which can be connected to a string loop interface of a detector device in a chain manner with other module-level shutdown devices MLSD of the photovoltaic module string via a DC cable to form a closed loop;

[0038] a second interface connected to an associated photovoltaic module, and

[0039] A controller, the controller being used to generate a control signal for turning on or off the associated photovoltaic module to be applied to the main switch of the module-level shutdown device MLSD in response to an operation permission PTO signal received by the module-level shutdown device MLSD via its first interface from the string loop interface of the detector device, wherein the delay of the control signal generated by the controller of the module-level shutdown device MLSD relative to the reception time of the operation permission PTO signal is distributed within a predefined maximum delay time period.

[0040] In a possible embodiment of the module-level shutdown device MLSD according to the third aspect of the present invention, the controller of the module-level shutdown device MLSD is used to distribute the control signal applied to the main switch of the module-level shutdown device MLSD so as to randomly turn on or off the associated photovoltaic module within the predefined maximum delay time period.

[0041] In the following, possible embodiments of different aspects of the present invention are described in more detail with reference to the accompanying drawings.

[0042] Figure 1 shows a block diagram of a conventional MLSD test setup for illustrating the problem underlying the present invention;

[0043] Figure 2 schematically illustrates a string of photovoltaic modules connected to a detector device according to one aspect of the present invention;

[0044] Figure 3 shows a block diagram of a possible exemplary embodiment of a detector arrangement according to another aspect of the invention;

[0045] Figure 4 A flow chart showing an exemplary embodiment of a method for detecting a faulty connection of a photovoltaic module within a photovoltaic module string according to another aspect of the present invention;

[0046] Figure 5shows a possible exemplary embodiment of a module level shutdown device MLSD according to another aspect of the invention;

[0047] Figure 6 It shows that Figure 5 A block diagram of a possible exemplary embodiment of a control unit within a module level shutdown device MLSD is shown;

[0048] Figure 7 Another exemplary embodiment of a module level shutdown device MLSD according to the present invention is shown;

[0049] Figure 8 It shows that Figure 7 A block diagram of a possible embodiment of a control unit in a module level shutdown device MLSD is shown;

[0050] Fig. 9 shows a signal diagram for illustrating the operation of the method and apparatus according to the present invention;

[0051] Fig.10 shows another signal diagram for illustrating a possible exemplary embodiment of the method and the device according to the invention;

[0052] Fig.11 An exemplary histogram illustrating the operation of the method and apparatus according to the present invention is shown;

[0053] Fig.12 Another schematic diagram for illustrating the operation of a possible exemplary embodiment of the method and apparatus according to the present invention is shown.

[0054] As in Figure 2 As can be seen in FIG. 1 , a photovoltaic module string 1 can be connected to a detector device 2. The detector device has a string loop interface that can be connected to a plurality of module-level shutdown devices 3-1, 3-2, 3-3 ... 3-N via a DC cable 4. A module-level shutdown device (MLSD) 3-i is connected in series to the string loop interface of the detector device 2 of the photovoltaic module string 1 in the MLSD chain to form a Figure 2 Each module-level shutoff device 3-i includes an associated photovoltaic module 5-i of the photovoltaic module string 1, such as Figure 2 As shown in the schematic diagram.

[0055] Therefore, each module-level shut-off device 3-i of the photovoltaic module string 1 includes a first interface 6 for connecting in series to its immediately adjacent module-level shut-off devices 3-(i-1), 3-(i+1) via two DC cables 4 to form a chain with other module-level shut-off devices 3-i, and the chain is connected to the string loop interface of the detector device 2 via a pair of DC cables 4 to form a closed loop. As can be seen, the first module-level shut-off device 3-1 and the last module-level shut-off device 3-N in the chain of the serially connected module-level shut-off devices 3-i within the photovoltaic module string 1 are connected to the string loop interface of the detector device 2 via a pair of DC cables 4. The detector device 2 can be integrated in another unit, in particular, in an inverter device that can be permanently connected to the photovoltaic module string 1. The detector device 2 can also be integrated in a portable test device that can be connected to the photovoltaic module string 1 for performing tests.

[0056] Each module-level shut-off device 3 - i comprises a second interface 7 connected to its associated photovoltaic module 5 - i, such as Figure 2 As shown. The photovoltaic module 5-i generates a current I in response to the received sunlight. The current I is supplied to the second interface 7 of the module-level shutdown device 3-i. At the first interface 6, a corresponding voltage V is generated. The circuit voltage V of the serially connected module-level shutdown devices 3-i of the MLSD chain generates a string voltage V applied to the string loop interface of the detector device 2 str The detector device 2 can communicate with the module-level shutdown device 3-i using power line communication PLC. Therefore, communication is performed via a DC cable 4, which connects the module-level shutdown devices 3-i in series with each other in a chain manner and connects them to the string loop interface of the detector device 2, thereby forming a Figure 2 The closed loop is shown.

[0057] Figure 3 A block diagram of a possible exemplary embodiment of a detector device 2 for a photovoltaic module string 1 is shown. Figure 3 In the illustrated embodiment, the detector device 2 comprises a signal sending unit 2A, a signal capturing unit 2B and a processing unit 2C.

[0058] In a possible embodiment, the signal sending unit 2A of the detector device 2 is used to send the operation permission PTO signal to the connected module-level shutdown devices 3-i of the photovoltaic module string 1 via the power line communication PLC via the string loop interface. The string loop interface of the detector device 2 includes the connection of the detector device 2 to the first interface 6-1 of the first MLSD 3-1 and the first interface 6-N of the last MLSD 3-N of the chain of serially connected module-level shutdown devices 3-i of the photovoltaic module string 1 through two DC cables 4. Therefore, the signal sending unit 2A in the detector device 2 sends the operation permission PTO signal to activate the module-level shutdown device MLSD 3. The module-level shutdown devices MLSD 3 are connected to the PV modules 5 one by one, because each MLSD 3 causes an individual connection delay.

[0059] The signal capture unit 2B of the detector device 2 is used to capture the string voltage waveform V str (t), as a result of the non-simultaneous connection of MLSD 3, the above string voltage waveform V str (t) is provided to the string loop interface of the detector device 2 by the chain of serially connected module level shutdown devices (MLSD) 3-i of the photovoltaic module string 1. The result is a turn-on transient step generated by the module level shutdown devices 3-i of the photovoltaic module string 1 in response to the received operation permissive PTO signal, wherein the turn-on delay of the turn-on transient is distributed within a predefined maximum delay time period.

[0060] like Figure 3 As shown, the detector device 2 further comprises a processing unit 2C, which is used to analyze the captured string voltage waveform V provided by the chain of module-level shutdown devices 3-i connected in series in the photovoltaic module string 1. str (t) to determine the number N of photovoltaic modules 5 and associated module-level shutoff devices 3 that have been correctly installed in the photovoltaic module string 1 .

[0061] In a possible embodiment, the detector device 2 may include additional entities. In a possible embodiment, the detector device 2 may include a user interface UI to signal a faulty installation or a fault-free installation of the photovoltaic modules 5 and their associated module-level shutoff devices 3 within the photovoltaic module string 1. The detector device 2 may also include an integrated control and data interface to signal a faulty installation or a fault-free installation of the photovoltaic modules 5 and their associated module-level shutoff devices 3 within the photovoltaic module string 1 to a remote central control entity of an automation system.

[0062] Figure 4 shows the use of Figure 3 Flow chart of an exemplary embodiment of a method for detecting a faulty connection of a photovoltaic module 5 equipped with an associated module-level shut-off device 3 using a detector device 2 shown. Figure 4 In the exemplary embodiment shown, the detection method comprises three main method steps S1 , S2 , S3 .

[0063] In a first step S1, the signal sending unit 2A of the detector device 2 sends an operation permission PTO signal to the loop of the serially connected module-level shutdown devices 3-i of the associated photovoltaic module string 1 using the power line communication PLC to activate the module-level shutdown devices MLSD 3 one by one with a connection delay.

[0064] In a further step S2, the signal capture unit 2B of the detector device 2 connected to the chain of serially connected module-level shutdown devices 3-i of the photovoltaic module string 1 captures the string voltage waveform V provided by the chain of module-level shutdown devices 3-i of the photovoltaic module string 1 as a result of the non-simultaneous connection of the MLSDs 3. str (t). As a result, the module-level shutdown device 3-i responds to the module-level shutdown device 3-i through the DC cable 4 from Figure 2 The turn-on transient is generated by the operation permission PTO signal received by the serial loop interface of the detector device 2 of the loop shown. The turn-on delay of the turn-on transient is distributed within a predefined maximum delay time period. In a possible embodiment, the turn-on delay of the turn-on transient is randomly distributed within the predefined maximum delay time period. In a possible implementation, the turn-on delay of the turn-on transient can be distributed within a maximum delay time period defined in a range between 0.1 seconds and 10 seconds. For example, at each first method step S1, a new random value can be generated in each MLSD 3.

[0065] In another step S3, the processing unit 2C of the detector device 2 analyzes the captured string voltage waveform V provided by the chain of module-level shutdown devices 3-i connected in series to the string loop interface of the detector device 2 in the photovoltaic module string 1. str (t) to determine the number N of photovoltaic modules 5 - i and their associated module-level shutoff devices 3 - i that have been correctly installed in the corresponding photovoltaic module string 1 .

[0066] In a possible embodiment, Figure 2 As shown in Figure 3 The detector device 2 shown in the block diagram of may be implemented in an inverter device that converts a DC string voltage generated by a photovoltaic module string 1 into an AC current that is supplied to a load and / or a grid.

[0067] In an alternative embodiment, if Figure 2 As shown and Figure 3The detector device 2 shown in the block diagram of FIG. 1 can also be implemented in a test device for testing a photovoltaic module string 1. The test device can be a portable device connected to the photovoltaic module string 1 for executing a test procedure. The test procedure can include, for example, Figure 4 The detection method is shown in the flow chart.

[0068] In a possible embodiment, the string voltage waveform V provided by the module-level shutdown device 3 - i of the photovoltaic module string 1 and captured by the signal capture unit 2B of the detector device 2 str (t) can be analyzed in the time domain by the processing unit 2C of the detector device 2. In a preferred embodiment, after performing a signal transformation to the frequency domain, the captured string voltage waveform V provided by the chain of series module-level shutdown devices 3-i of the photovoltaic module string 1 is analyzed by the processing unit 2C of the detector device 2. str (t).

[0069] In a possible embodiment, the captured string voltage waveform V str (t) includes a stepped string voltage (such as Fig.10 As shown in FIG. 1 , the detector device 2 is connected to the chain of module-level shutdown devices 3 - i of the photovoltaic module string 1 in a loop manner. The string voltage waveform V captured by the signal capture unit 2B of the detector device 2 str (t) can be converted into a digital signal at a specific sampling rate SR by the analog-to-digital converter ADC of the signal acquisition unit 2B of the detector device 2. The data acquisition unit of the detector device 2 can be formed as follows Figure 3 The digital signal may include string voltage data samples stored in a data memory integrated in the signal capture unit 2B or in a processing unit 2C of the detector device 2.

[0070] In a possible embodiment, the sample histogram h is derived by the signal processing unit 2C of the detector device 2 from string voltage data samples stored in a data memory integrated into the data acquisition unit of the detector device 2. In a possible embodiment, the sample histogram h can be derived from the stored string voltage data samples by repeatedly counting each string voltage data sample after a voltage step with a substantially identical constant string voltage, wherein the substantially identical constant string voltage is applied by the actually active module-level shut-off devices 3-i of the photovoltaic module string 1 to the string loop interface of the signal capture unit 2B of the detector device 2 of the photovoltaic module string 1.

[0071] In a preferred embodiment, the signal processing unit 2C of the detector device 2 is used to perform a discrete Fourier transform DFT on the sample histogram h of the string voltage data samples stored in the data memory of the data acquisition unit. The data processing unit 2C can perform a discrete Fourier transform DFT on the sample histogram h of the string voltage data samples to calculate a histogram spectrum H of the sample histogram h in the frequency domain.

[0072] The number of periods between peaks in the calculated sample histogram h is related to the step-shaped string voltage waveform V applied to the string loop interface of the detector device 2 by the chain of serially connected module-level shutdown devices 3-i of the photovoltaic module string 1 str (t) corresponds to the number of voltage steps N, indicating the number of correctly installed photovoltaic modules 5-i and associated module-level shutdown devices 3-i within the photovoltaic module string 1. In addition, the number of periods between peaks in the calculated sample histogram h allows to compare the string voltage V str The average open circuit voltage V of the module-level shutdown device 3 of the photovoltaic module 5 correctly installed in the photovoltaic module string 1 is determined by combining oc .

[0073] In a possible embodiment, the DFT index at the maximum peak in the calculated histogram spectrum H derived by the processing unit 2C of the detector device 2 of the photovoltaic module string 1 indicates the number N of correctly installed photovoltaic modules 5 and associated module-level shutdown devices 3 in the corresponding photovoltaic module string 1 .

[0074] In a possible embodiment, the determined number N of photovoltaic modules 5 and associated module-level shutoff devices 3 that have been correctly installed in the photovoltaic module string 1 can be compared with a predefined set number N by a comparator integrated in the processing unit 2C of the detector device 2. set The comparison is performed to verify that all photovoltaic modules 5 and the associated module-level shutdown devices 3 have been correctly installed in the corresponding photovoltaic module string 1. In a possible embodiment, the number N is set set It may be input by the user via the user interface UI of the detector device 2. In an alternative embodiment, the number N is set set It can be read from the configuration memory CONFIG-MEM or obtained from the remote central control entity of the photovoltaic system via the control and data interface. set It can be, for example, the number of all photovoltaic modules 5 purchased by the user to be installed in the photovoltaic module string 1 of the user's photovoltaic system. After the photovoltaic modules 1 are installed, it can be verified whether all photovoltaic modules 5 and the associated module-level shutdown devices 3 have been correctly installed. If the DFT index at the maximum peak is equal to N set , this is the case.

[0075] In such Figure 4In another possible embodiment of the method shown, if the number N of photovoltaic modules 5 and associated module-level shutdown devices 3 that have been correctly connected to the string loop interface of the detector device 2 of the corresponding photovoltaic module string 1 is less than the predefined set number N set , the countermeasures can be automatically triggered by the controller of the detector device 2 of the photovoltaic module string 1. In addition, if it is found that the number N of photovoltaic modules 5 and the associated module-level shutdown devices 3 correctly connected to the string loop interface of the detector device 2 of the photovoltaic module string 1 is less than the predefined set number N set , then the module-level shutoff device 3-i of the string loop interface of the detector device 2 connected to the photovoltaic module string 1 can be automatically closed by the controller of the detector device 2 by stopping the operation permission PTO transmission of the signal transmission unit 2A, and can be opened again by resending the operation permission PTO signal by the signal transmission unit 2A to repeat the detection process. Figure 4 The method shown in the flowchart in FIG. 1 can be used when it is found that the number N of correctly installed photovoltaic modules 5 and associated module-level shutoff devices 3 is less than a predetermined desired set number N of photovoltaic modules 5 and module-level shutoff devices 3. set Repeat in case of .

[0076] In such Figure 4 In a possible embodiment of the method shown, the detection method can be performed during or after the installation of the photovoltaic module string 1. In particular, after the installation process has been completed, such as Figure 4 The method shown allows verifying whether all photovoltaic modules 5-i and the associated module-level shutdown devices 3-i of the corresponding photovoltaic module string 1 have been correctly installed. The detector device 2 can be integrated in an inverter having a DC input connected to the loop of the module-level shutdown device 3-i. Figure 2 After the module-level shutdown device 3-i of the photovoltaic module string 1 is shown, the detector device 2 integrated in the inverter can be activated as shown in FIG. Figure 4 The detection process shown in the flowchart of FIG. 1 is used to determine whether all photovoltaic modules 5 - i and the associated module-level shutdown devices 3 - i have been correctly installed.

[0077] In another possible embodiment, also during normal operation of the PV module string 1 and its connected inverter, a detection method may be performed in the background, for example periodically monitoring whether all PV modules 5 - i and associated module-level shutdown devices 3 - i are still fully operational.

[0078] In yet another embodiment, the detector device 2 may be integrated into a portable testing device that is connected to the photovoltaic module string 1 after installation to verify whether the installation has been successfully completed.

[0079] In a possible embodiment, the operation permission PTO signal is a periodic signal sent by the signal sending unit 2A of the detector device 2 of the photovoltaic module string 1 to the module-level shutdown device 3-i of the photovoltaic module string 1 in the downlink channel / DC cable 4 using the power line communication PLC. The first interfaces 6-i of the module-level shutdown devices 3-i of the photovoltaic module string 1 are connected in series with each other in a chain manner via the DC cable 4. The first module-level shutdown device 3-1 and the last module-level shutdown device 3-N of the MLSD chain are connected to the string loop interface 4 of the detector device 2 via a pair of DC cables 4 to form a closed loop with the detector device 2, as shown in FIG. Figure 2 shown.

[0080] In a possible embodiment, the operation permission PTO signal may also include an encoded address to individually activate a specific associated module-level shutdown device 3-i of the photovoltaic module string 1, and trigger the generation of a corresponding start-up signal transient in response to the received power line communication PLC operation permission PTO signal to individually turn on the associated photovoltaic module 5 connected to the addressed module-level shutdown device 3.

[0081] Figure 5 A block diagram illustrating a possible exemplary embodiment of a module-level shutdown device 3 - i of a photovoltaic module string 1 according to one aspect of the present invention is shown. Figure 5 As can be seen in FIG. 1 , the module-level shutdown device 3 comprises a first interface 6, which can be connected to the string loop interface of the detector device 2 in a chain manner with other module-level shutdown devices 3-i via a DC current cable 4 to form a closed loop. The module-level shutdown device 3 also comprises a second interface 7 connected to its associated photovoltaic module 5, such as Figure 5 The module-level shutdown device 3 includes a controller 8, which is used to generate a control signal CRTL to turn on or off the associated photovoltaic module 5 through the switch 10 in response to the operation permission PTO signal received by the module-level shutdown device 3 from the signal sending unit 2A of the detector device 2 of the photovoltaic module string 1 via the first interface 6. Figure 5 In the simplified schematic diagram of the module-level shutdown device 3 shown, the module-level shutdown device 3 includes a PLC AFE (analog front end) filter 9 for filtering the PLC signal and feeding the filtered signal to the controller 8 .

[0082] Figure 6 A possible exemplary embodiment of a controller 8 in a module-level shutdown device 3 receiving a filtered signal from a PLC RFE 9 is shown. In the illustrated embodiment, the controller 8 integrated in the module-level shutdown device 3 has a PLC receiver for demodulating the received baseband signal. A subsequent PTO decoder is used to decode the received PTO command. A random number generator integrated in the controller 8 of the module-level shutdown device 3 can control a delay block, such as Figure 6 The delayed signal is supplied to the switch control circuit, which is used to drive the main switch 10 of the module-level shutdown device 3, as shown in FIG. Figure 5 As shown in the circuit diagram. Figure 6 The controller 8 shown in the schematic block diagram of can be implemented in different ways. Figure 6 The controller 8 shown may be implemented using a microcontroller, an ASIC or an FPGA or another hardware solution or even a mixture of these different technical implementations. Figure 6 Each block shown in the figure may be implemented as a hardware or software module.

[0083] Figure 7 An alternative embodiment of the module-level shutdown device 3 in the photovoltaic module string 1 according to the present invention is shown. Figure 7 In the embodiment shown, the module-level shutdown device 3 is operated by radio communication instead of PLC communication. Figure 7 In the illustrated embodiment, the module-level shutdown device 3 includes an RF receiver 11 to receive a radio communication command signal from an RF transmitter, which may be integrated as a signal transmission unit 2A in the detector device 2 of the photovoltaic module string 1 .

[0084] Figure 8 Shown as Figure 7 A possible exemplary embodiment of a controller 8 in a module-level shutdown device 3 is shown. Figure 6 The controller 8 shown includes a PTO decoder, a random number generator RNG, a delay block and a switch control circuit for driving the main switch 10 .

[0085] Fig. 9 A schematic diagram is shown for illustrating the operation of the method and apparatus according to the present invention. Fig. 9 The randomized opening delay of the module-level shut-off devices 3 - i within the photovoltaic string 1 according to the first method step S1 is illustrated. Fig. 9 In the example shown, a number N (here N=13) of photovoltaic modules 5 are subsequently switched on at different points in time (signal transients). The first photovoltaic module 5 is switched on at approximately 100 milliseconds, and the last (thirteenth) photovoltaic module 5 is switched on at approximately 900 milliseconds. Fig. 9 All photovoltaic modules 5 included in the example shown have an open circuit voltage V of about 35 V. oc .exist Fig. 9 In the given example of , the eighth photovoltaic module 5 and the ninth photovoltaic module 5 are turned on almost at the same time. For example, the eighth photovoltaic module 5 can be turned on together with the second photovoltaic module 5 in the chain. Fig. 9 The diagram shows the signal transients within a predefined maximum delay period of, for example, 1000 milliseconds. The distribution of the turn-on transients within 1000 milliseconds, i.e. within 1 second, is shown. Fig. 9 As shown. The maximum delay time distribution can be configured or predefined according to the use case in the design phase of the photovoltaic system 1. The maximum delay time period can be limited to a range of 0.1 seconds to 10 seconds, for example. For each connection, i.e. at each module-level shutdown device 3, another random value can be generated by the random number generator RNG of the controller 8 integrated in the module-level shutdown device 3, such as Figure 6 , Figure 8 shown.

[0086] According to the second method step S2, this indeed results in a string voltage waveform V provided by the chain of module-level shutdown devices 3 of the photovoltaic module string 1, which is applied to the string loop interface of the detector device 2. str (t), such as Fig.10 As shown. Usually, the string voltage waveform V str (t) is generated by the non-simultaneous connection of MLSD 3. Fig.10 As can be seen in FIG. 1 , the captured string voltage waveform V of the string loop interface applied to the signal capture unit 2B of the detector device 2 is str (t) Increase gradually. Fig.10 Each voltage step occurs in Fig. 9 At the time of the corresponding signal transient shown in . Fig.10 At each voltage step of the captured string voltage waveform shown, the photovoltaic module 5 is turned on in the loop by its associated module-level shutdown device 3 through the main switch 10, as shown in FIG. Figure 5 , Figure 7 As shown in the schematic block diagram of Fig.10 Each voltage step of the captured string voltage waveform shown represents a photovoltaic module 5 and its associated module-level shutdown device 3. Fig. 9 , Fig.10 In the example of FIG. 5 , the voltage step at approximately 700 milliseconds is barely visible, since both photovoltaic modules 5 are switched on almost simultaneously.

[0087] In a possible embodiment, the step waveform V can be str (t) to perform the following in the time domain: Fig.10 The step-shaped waveform V str (t). If the constant voltage between two voltage steps is small or very small, the counting of voltage steps in the time domain proves to be difficult and error-prone. Therefore, in a preferred embodiment of the method and device according to the present invention, the captured string voltage waveform V provided by the module-level shutdown device 3 of the photovoltaic module string 1 is performed in the frequency domain after the signal transformation. str(t) is analyzed to determine the number N of correctly installed photovoltaic modules 5 and associated module-level shutdown devices 3 in the photovoltaic module string 1. This makes the detection of correctly installed photovoltaic modules 5 and associated module-level shutdown devices 3 faster than the step waveform V in the time domain. str The analysis of (t) is more flexible, robust, and less error-prone.

[0088] Fig.11 An exemplary sample histogram h is illustrated which is derived by the processing unit 2C of the detector device 2 from string voltage data samples stored in the data memory of the detector device 2, also according to the third method step S3. Fig.11 In the example of FIG. 1 , the peak value near 275 V is not visible / almost not visible because, as mentioned above, the two photovoltaic modules 5 are turned on almost at the same time. In a possible embodiment, the stored string voltage data samples can be countered to obtain the same string voltage V str The string voltage data samples are counted to derive the sample histogram h, where the same string voltage V str The chain of module-level shutdown devices 3 of the photovoltaic module string 1 is applied to the string loop interface of the detector device 2 of the photovoltaic module string 1 . Fig.11 The pictures shown correspond to Fig.10 The string voltage waveform V str (t). As long as the voltage amplitude is substantially constant, the samples are counted with the counter using the sampling rate SR.

[0089] In a further processing step, the processing unit 2C of the detector device 2 may process the Fig.11 The sample histogram h of the string voltage data samples shown in FIG. 1 is subjected to a discrete Fourier transform DFT. In this way, the processing unit 2C of the detector device 2 can calculate the spectrum of the sample histogram h in the frequency domain, such as Fig.12 As shown, as a histogram spectrum H. In the frequency domain, Fig.10 The almost invisible constant voltage at about 700ms and Fig.11 The barely visible sample at about 275 V in the image is not a problem for DFT calculations.

[0090] Also according to the third step S3, Fig.12 The calculated sample histogram H shown corresponds to Fig.11 The sample histogram h of the string voltage data samples shown in FIG. Fig.10 The step-shaped string voltage waveform V shown is provided by the chain of module-level shutdown devices 3 of the photovoltaic module string 1 to the string loop interface of the detector device 2. str In the illustrated diagram, the DFT index (x) and the amplitude / abs of the peak value (y) can be seen.

[0091] The DFT index N at the maximum peak in the calculated histogram spectrum H derived by the processing unit 2C of the detector device 2 indicates the number N of correctly installed photovoltaic modules 5 and associated module-level shutdown devices 3 in the corresponding monitored photovoltaic module string 1. Fig.12 In the example shown, the number N of correctly installed photovoltaic modules 5 and associated module-level shutdown devices 3 is thirteen (N=13). This can be derived from the maximum peak in the histogram spectrum H. The absolute value (ABS(DFT)) of the DFT index zero (N=0) (not shown) is usually higher than all other values. Therefore, in a possible embodiment, it is excluded before looking for the maximum value in the histogram spectrum H. The maximum peak is the first peak in the histogram spectrum H, also as shown in FIG. Fig.12 as shown in the example.

[0092] The determined number N of correctly installed photovoltaic modules 5 and associated module-level shut-off devices 3 can be compared with a predefined set number N of photovoltaic modules 5 and associated module-level shut-off devices 3 by a comparator of the processing unit 2C of the detector device 2. set The comparison is performed to verify that all photovoltaic modules 5 have been correctly installed in the photovoltaic module string 1 and have been correctly connected to the string loop interface of the detector device 2 via the loop DC cable 4. If the detector device 2 is integrated in the inverter of the photovoltaic module string 1, it can also be verified in this way that the photovoltaic modules 5 and the associated module-level shutdown devices 3 have been correctly connected to the DC input of the inverter of the photovoltaic module string 1. For example, in Fig.12 In the example shown, if the planned number N of photovoltaic modules 5 and associated module-level shutoff devices 3 in the photovoltaic module string 1 is 14 (N set =14) and it is determined that the number N of correctly installed photovoltaic modules 5 and associated module-level shut-off devices 3 is only 13 (N=13), it can be found that one photovoltaic module 5 and / or its associated module-level shut-off device 3 has not been correctly installed. In this case, the controller of the detector device 2 can trigger countermeasures in a possible embodiment, in particular, send a warning message to a remote central control entity of the photovoltaic system. In addition, a warning message can be displayed to the operator of the photovoltaic system on the display unit of the user interface UI of the detector device 2. In addition, if the number N of photovoltaic modules 5 and associated module-level shut-off devices 3 that have been correctly installed in the photovoltaic module string 1 is less than a predefined or preconfigured set number N set , the module-level shut-off device 3 of the photovoltaic module string 1 can be automatically shut down by the controller of the detector device 2 by stopping sending the operation permission PTO signal. The controller of the detector device 2 can start sending the operation permission PTO signal again to repeat the above steps. Figure 4The detection process shown in the flowchart of . The operation permission PTO signal may include a periodic signal sent by the signal sending unit 2A of the detector device 2 to the loop of the module-level shutdown device 3 of the photovoltaic module string 1 via the power line communication PLC in the downlink channel / DC cable 4, and the loop of the module-level shutdown device 3 of the photovoltaic module string 1 is connected to the detector device 2 of the photovoltaic module string 1 via the DC cable 4.

[0093] In a possible embodiment, the waveform analysis may be performed by a tester comprising an integrated detector device 2. In an alternative embodiment, the waveform analysis may be performed by a detector device 2 integrated in an inverter connected to the respective photovoltaic module string 1 .

[0094] The signal transmission unit 2A of the detector device 2 can transmit a PLC PTO signal to the chain of module-level shutdown devices 3 connected in series in the downlink channel, and the string voltage waveform V str (t) is captured by the signal capture unit 2B of the detector device 2. In a possible embodiment, a microcontroller with a built-in 12-bit analog-to-digital converter ADC can be used to perform signal waveform capture and signal analysis. The processing unit 2C including such a microcontroller can be used to calculate Fig.11 The histogram h shown and Fig.12 The histogram H is shown. The number of periods between peaks (i.e., the number of voltage steps) can be determined by using the DFT of the FFT. Fig.12 The FFT results shown can be used to derive the number N of correctly connected photovoltaic modules 5 and associated module-level shutdown devices 3 within the photovoltaic module string 1 .

[0095] In summary, the signal transmission unit 2A in the detector device 2 transmits the operation permission PTO signal to activate the module-level shut-off device MLSD 3. The module-level shut-off device MLSD 3 connects the PV modules PVM 5 one by one. The connection delay of each module-level shut-off device MLSD 3 is determined by a random number within a predefined period. The capture unit 2B collects the string voltage waveform V generated by the non-simultaneous connection of the MLSD 3. str (t) samples. The processing unit 2C obtains the string voltage waveform V str (t) generating a histogram and then determining the number of appropriately connected photovoltaic modules PVM 5 equipped with associated module level shutdown devices MLSD 3 by applying a discrete Fourier transform DFT to the generated histogram.

[0096] In the case where the photovoltaic system comprises a multi-string system having a plurality of photovoltaic module strings 1, the detection method according to the invention can be performed individually on each photovoltaic module string 1 of the photovoltaic system. The method according to the invention can be performed by the photovoltaic system owner or by an operator who performs the installation of the photovoltaic system. The method according to the invention can also be used to monitor the photovoltaic system during its operation, for example to detect interruptions of installation connections within the photovoltaic system.

[0097] The present invention at least includes the following embodiments:

[0098] Embodiment 1. A method for detecting a faulty installation of a photovoltaic module (5), the photovoltaic module (5) being provided with an associated module level shut-down device MLSD (3) connected in series to a string loop interface of a detector device (2) within a photovoltaic module string (1),

[0099] The method comprises the following steps:

[0100] - the detector device (2) sends (S1) an operation permission PTO signal to the chain of module-level shutdown devices MLSD (3) connected in series of the photovoltaic module string (1) through its string loop interface using power line communication PLC;

[0101] - Capturing (S2) the string voltage waveform (V str (t)), as a result of a turn-on transient generated by the module-level shutdown device MLSD (3) in response to an operation permission PTO signal received by the chain of the series-connected module-level shutdown devices MLSD (3) from the string loop interface of the detector device (2), the string voltage waveform (V str (t)) applied by the module level shutdown device MLSD (3) of the photovoltaic module string (1) to the string loop interface of the detector device (2), wherein the turn-on delay of the generated turn-on transient is distributed within a predefined maximum delay time period; and

[0102] - analyzing (S3) by the detector device (2) a captured string voltage waveform V provided by the chain of serially connected module level shutdown devices MLSD (3) of the photovoltaic module string (1); str (t) to determine the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1).

[0103] Embodiment 2. The method according to embodiment 1, wherein the turn-on transients generated by the module-level shutdown device MLSD (3) of the photovoltaic module string (1) are randomly distributed within the predefined maximum delay time period.

[0104] Embodiment 3. A method according to any one of the preceding embodiments 1 or 2, wherein the detector device (2) of the chain of module-level shutdown devices MLSD (3) connected in series to the photovoltaic module string (1) via a string loop interface is implemented in an inverter device, or in a test device for testing the photovoltaic module string (1).

[0105] Embodiment 4. The method according to any one of the preceding embodiments 1 to 3, wherein the captured string voltage waveform V provided by the chain of serially connected module-level shutdown devices MLSD (3) of the photovoltaic module string (1) str (t) Analyzed by a processing unit (2C) of the detector device (2) in the time domain or in the frequency domain after signal transformation.

[0106] Embodiment 5. The method according to any one of the above embodiments 1 to 4, wherein the captured string voltage waveform V str (t) comprising a stepped string voltage applied to the string loop interface of the detector device (2), the detector device (2) being connected in a closed loop manner to the chain of serially connected module level shutdown devices (MLSD) (3) of the photovoltaic module string (1), and wherein the captured string voltage waveform V is converted by an analog-to-digital converter ADC of a data acquisition unit of the detector device (2) at a specific sampling rate SR str (t) converting into a digital signal comprising string voltage data samples stored in a data memory of a data acquisition unit of the detector device (2).

[0107] Embodiment 6. A method according to embodiment 5, wherein a sample histogram (h) is derived by the processing unit (2C) of the detector device (2) from the string voltage data samples stored in the data memory of the data acquisition unit of the detector device (2), wherein the sample histogram (h) is derived from the stored string voltage data samples by repeatedly counting the string voltage data samples having the same constant string voltage applied to the string loop interface of the detector device (2) by the chain of module-level shutdown devices (MLSD) connected in series of the photovoltaic module string (1) for the entire string voltage waveform, and the detector device (2) is connected to the chain (3) of module-level shutdown devices (MLSD) connected in series of the photovoltaic module string (1) in a closed loop manner.

[0108] Embodiment 7. A method according to any one of the preceding embodiments 1 to 6, wherein the processing unit (2C) of the detector device (2) performs a discrete Fourier transform DFT on the sample histogram (h) of the string voltage data samples to calculate a spectrum (H) of the sample histogram (h) in the frequency domain.

[0109] Embodiment 8. A method according to embodiment 7, wherein the DFT index at the maximum peak in the calculated histogram spectrum (H) derived by the processing unit (2C) of the detector device (2) of the chain of serially connected module-level shutdown devices MLSD (3) connected to the photovoltaic module string (1) indicates the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1),

[0110] The comparator of the processing unit (2C) of the detector device (2) compares the determined number N of photovoltaic modules (5) correctly installed in the photovoltaic module string (1) and the associated module level shutdown devices MLSD (3) with a predefined set number N. set A comparison is performed to verify that all photovoltaic modules (5) and associated module level shutdown devices MLSD (3) have been properly installed within the photovoltaic module string and properly connected to the string loop interface of the detector device (2).

[0111] Embodiment 9. The method according to embodiment 8, wherein if the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1) and correctly connected to the string loop interface of the detector device (2) is less than the predefined set number N set , a countermeasure is triggered by the controller of the detector device (2), and / or wherein, if the number N of photovoltaic modules (5) and associated module-level shut-off devices MLSD (3) correctly installed in the photovoltaic module string (1) and correctly connected to the detector device (2) is less than the predefined set number N set , the module-level shut-off device MLSD (3) of the photovoltaic module string (1) is turned off by stopping the sending of the operation permission PTO signal, and is turned on again by sending the operation permission PTO signal again to repeat the process of the detection method.

[0112] Embodiment 10. A method according to any one of embodiments 1 to 9, wherein the operation permission PTO signal is a periodic signal sent by the signal sending unit (2A) of the detector device (2) through the power line communication PLC in a downlink channel, and the detector device (2) is connected to the chain of module-level shutdown devices MLSD (3) connected in series of the photovoltaic module string (1) via a pair of DC cables (4).

[0113] Embodiment 11. A method according to embodiment 10, wherein the operation permission PTO signal includes an encoded address to individually activate a specific associated module-level shutdown device MLSD (3) of the photovoltaic module string (1), and triggers the generation of a corresponding start-up transient in response to a received power line communication PLC operation permission PTO signal to individually turn on the associated photovoltaic module (5) connected to the addressed module-level shutdown device MLSD (3).

[0114] Embodiment 12. A detector device (2) having a string loop interface connected to a chain of serially connected module-level shutdown devices MLSD (3) of a photovoltaic module string (1), the detector device (2) comprising a unit for performing a method according to any one of the preceding embodiments 1 to 11.

[0115] Embodiment 13. The detector device (2) according to embodiment 12, comprising:

[0116] - a signal transmission unit (2A) for transmitting an operation permission PTO signal to the chain of connected module-level shutdown devices MLSD (3) of the series connection of the photovoltaic module string (1) by means of a power line communication PLC through a string loop interface of the detector device (2);

[0117] - a signal capture unit (2B) for capturing, as a result of a turn-on transient step generated by the module-level shut-off device MLSD (3) of the photovoltaic module string (1) in response to a received operation permission PTO signal, a string voltage waveform V provided to the string loop interface of the detector device (2) by the chain of the serially connected module-level shut-off devices MLSD (3) of the photovoltaic module string (1) str (t), wherein the turn-on delay of the turn-on transient is distributed within a predefined maximum delay period; and

[0118] - a processing unit (2C) for analyzing a captured string voltage waveform V provided by a chain of serially connected module-level shutdown devices MLSD (3) of the photovoltaic module string (1); str (t) to determine the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1).

[0119] Embodiment 14. The detector device according to Embodiment 12 or 13 further comprises a user interface and / or a control and data interface for signaling a faulty installation or a fault-free installation of the photovoltaic module (5) and the associated module-level shutdown device MLSD (3) within the photovoltaic module string (1).

[0120] Embodiment 15. A module-level shutdown device MLSD (3) of a photovoltaic module string (1), comprising:

[0121] a first interface (6) which can be connected in a chain manner with other module level shutdown devices MLSD via a DC cable (4) and connected to a string loop interface of the detector device (2) to form a closed loop;

[0122] a second interface (7) connected to an associated photovoltaic module (5), and

[0123] A controller (8) is used to generate a control signal (CRTL) for turning on or off the associated photovoltaic module (5) applied to the main switch (10) of the module-level shutdown device (3) in response to an operation permission PTO signal received by the module-level shutdown device MLSD (3) via its first interface (6) from the string loop interface of the detector device (2), wherein the delay of the generated control signal (CRTL) relative to the reception time of the operation permission PTO signal is distributed by the controller (8) of the module-level shutdown device MLSD (3) within a predefined maximum delay time period.

[0124] Embodiment 16. A module-level shutdown device MLSD according to embodiment 15, wherein the controller (8) of the module-level shutdown device MLSD (3) includes a random number generator (RNG), which is used to distribute the control signal (CRTL) applied to the main switch (10) of the module-level shutdown device (3) to randomly turn on or off the associated photovoltaic module (5) within the predefined maximum delay time period.

Claims

1. A method for detecting faulty installations of photovoltaic modules (5) within a photovoltaic module string (1), each photovoltaic module (5) being equipped with an associated module level shut-off device MLSD (3) connected in series to a string loop interface of a detector device (2), The method comprises the following steps: - the detector device (2) uses power line communication PLC to send (S1) an operation permission PTO signal to the chain of module-level shutdown devices MLSD (3) connected in series of the photovoltaic module string (1) through the string loop interface of the detector device (2); - Capturing (S2) the string voltage waveform (V str (t)), as a result of a turn-on transient generated by the chain of the series-connected module-level shutdown devices MLSD (3) in response to the operation permission PTO signal sent to the chain of the series-connected module-level shutdown devices MLSD (3) through the string loop interface of the detector device (2), the string voltage waveform (V str (t)) applied by said chain of said series-connected module level shutdown devices MLSD (3) of said photovoltaic module string (1) to said string loop interface of said detector device (2), wherein a turn-on delay of a generated turn-on transient is distributed within a predefined maximum delay time period; and - analyzing (S3) by the detector device (2) the captured string voltage waveform V applied by the chain of serially connected module-level shutdown devices MLSD (3) of the photovoltaic module string (1) str (t) to determine the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1), and - The captured string voltage waveform V is converted by the analog-to-digital converter ADC of the signal capture unit (2B) of the detector device (2) at a specific sampling rate SR str (t) converted into a digital signal comprising string voltage data samples stored in a data memory of the signal capture unit (2B) of the detector device (2), wherein the captured string voltage waveform V str (t) comprising a stepped string voltage applied to the string loop interface of the detector device (2), the detector device (2) being connected in a closed loop manner to the chain of serially connected module level shutdown devices MLSD (3) of the photovoltaic module string (1).

2. The method according to claim 1, wherein the turn-on transients generated by the module-level shutdown device MLSD (3) of the photovoltaic module string (1) are randomly distributed within the predefined maximum delay time period.

3. A method according to any one of the preceding claims 1 or 2, wherein the detector device (2) of the chain of module-level shutdown devices MLSD (3) connected in series to the photovoltaic module string (1) via a string loop interface is implemented in an inverter device, or in a test device for testing the photovoltaic module string (1).

4. The method according to any one of the preceding claims 1 to 3, further comprising the following steps: The processing unit (2C) of the detector device (2) analyzes the captured string voltage waveform V applied by the chain of serially connected module-level shutdown devices MLSD (3) of the photovoltaic module string (1) in the time domain or in the frequency domain after signal transformation. str (t).

5. The method according to claim 1, further comprising the steps of: A sample histogram (h) is derived by a processing unit (2C) of the detector device (2) from the string voltage data samples stored in the data memory of the signal capture unit (2B) of the detector device (2) by repeatedly counting the string voltage data samples having the same constant string voltage applied to the string loop interface of the detector device (2) by the chain of module-level shutdown devices MLSD (3) connected in series to the photovoltaic module string (1) for the entire string voltage waveform, wherein the detector device (2) is connected to the chain of module-level shutdown devices MLSD (3) connected in series to the photovoltaic module string (1) in a closed loop manner.

6. The method according to claim 5, further comprising the steps of: A discrete Fourier transform (DFT) is performed by the processing unit (2C) of the detector device (2) on the sample histogram (h) of the string voltage data samples, and a spectrum (H) of the sample histogram (h) is calculated in the frequency domain.

7. The method according to claim 6, further comprising the steps of: determining the number N of photovoltaic modules (5) and associated module-level shut-off devices MLSD (3) correctly installed in the photovoltaic module string (1) based on the DFT index at the maximum peak in the calculated histogram spectrum (H) derived by the processing unit (2C) of the detector device (2) of the chain of serially connected module-level shut-off devices MLSD (3) connected to the photovoltaic module string (1); and, The comparator of the processing unit (2C) of the detector device (2) compares the determined number N of photovoltaic modules (5) correctly installed in the photovoltaic module string (1) and the associated module level shutdown devices MLSD (3) with a predefined set number N. set A comparison is performed to verify that all photovoltaic modules (5) and associated module level shutdown devices MLSD (3) have been properly installed within the photovoltaic module string and properly connected to the string loop interface of the detector device (2).

8. The method according to claim 7, further comprising the steps of: If the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1) and correctly connected to the string loop interface of the detector device (2) is less than the predefined set number N set , then a countermeasure is triggered by the controller of the detector device (2), and / or If the number N of photovoltaic modules (5) and associated module-level shutoff devices MLSD (3) correctly installed in the photovoltaic module string (1) and correctly connected to the detector device (2) is less than the predefined set number N set , the module-level shut-down device MLSD (3) of the photovoltaic module string (1) is turned off by stopping the sending of the operation permission PTO signal, and the module-level shut-down device MLSD (3) of the photovoltaic module string (1) is turned on by sending the operation permission PTO signal again, so as to repeat the process of the detection method.

9. A method according to any one of the preceding claims 1 to 8, wherein the operation permission PTO signal is a periodic signal sent by a signal sending unit (2A) of the detector device (2) via a power line communication PLC in a downlink channel, and the detector device (2) is connected to the chain of module-level shutdown devices MLSD (3) connected in series of the photovoltaic module string (1) via a pair of DC cables (4).

10. The method according to claim 9, further comprising the steps of: A specific associated module-level shutoff device MLSD (3) of the photovoltaic module string (1) is individually activated by a coded address included in the operation permission PTO signal, and the generation of a corresponding start-up transient is triggered in response to a received power line communication PLC operation permission PTO signal to individually turn on the associated photovoltaic module (5) connected to the addressed module-level shutoff device MLSD (3).

11. A detector device (2) having a string loop interface connected to a chain of serially connected module level shutdown devices MLSD (3) of a string of photovoltaic modules (1), the detector device (2) comprising a unit for performing the method according to any of the preceding claims 1 to 10.

12. The detector device (2) according to claim 11, comprising: - a signal sending unit (2A) for sending an operation permission PTO signal to the chain of serially connected module-level shut-down devices MLSD (3) of the photovoltaic module string (1) by means of a power line communication PLC through a string loop interface of the detector device (2); - a signal capture unit (2B), the signal capture unit (2B) is used to capture the string voltage waveform V str (t), as a result of a turn-on transient step generated by the module-level shutdown device MLSD (3) of the photovoltaic module string (1) in response to a received operation permission PTO signal, the string voltage waveform V str (t) applied to the string loop interface of the detector device (2) by the chain of the series-connected module level shutdown devices MLSD (3) of the photovoltaic module string (1), wherein the turn-on delay of the turn-on transient is distributed within a predefined maximum delay time period; and - a processing unit (2C) for analyzing the captured string voltage waveform V applied by the chain of serially connected module-level shutdown devices MLSD (3) of the photovoltaic module string (1); str (t) to determine the number N of photovoltaic modules (5) and associated module-level shutdown devices MLSD (3) correctly installed in the photovoltaic module string (1), The signal capture unit (2B) includes an analog-to-digital converter ADC, which is used to convert the captured string voltage waveform V into a digital signal at a specific sampling rate SR. str (t) converted into a digital signal comprising a string voltage data sample stored in a data memory of the signal capture unit (2B) of the detector device (2), wherein the captured string voltage waveform V str (t) comprising a stepped string voltage applied to the string loop interface of the detector device (2), the detector device (2) being connected in a closed loop manner to the chain of serially connected module level shutdown devices MLSD (3) of the photovoltaic module string (1).

13. The detector device according to claim 11 or 12 further comprises a user interface and / or a control and data interface for signaling a faulty installation or a fault-free installation of the photovoltaic modules (5) and the associated module-level shutdown device MLSD (3) within the photovoltaic module string (1).

14. A module level shutdown device MLSD (3) for a photovoltaic module string (1), comprising: a first interface (6) which can be connected in a chain manner with other module level shutdown devices MLSD via a DC cable (4) and connected to a string loop interface of the detector device (2) to form a closed loop; a second interface (7) connected to an associated photovoltaic module (5), and A controller (8) is used to generate a control signal (CRTL) for turning on or off the associated photovoltaic module (5) applied to the main switch (10) of the module-level shutdown device (3) in response to an operation permission PTO signal received by the module-level shutdown device MLSD (3) via its first interface (6) from the string loop interface of the detector device (2), wherein the controller (8) is also used to distribute the delay of the generated control signal (CRTL) relative to the reception time of the operation permission PTO signal within a predefined maximum delay time period.

15. The module-level shutdown device MLSD (3) according to claim 14, wherein the controller (8) comprises a random number generator (RNG) for distributing the control signal (CRTL) applied to the main switch (10) of the module-level shutdown device MLSD (3) to randomly turn on or off the associated photovoltaic module (5) within the predefined maximum delay time period.

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