Device and method for operating a photovoltaic system

Abstract

The invention relates to a device and to a method for operating a photovoltaic system (1000). The method comprises at least the following steps: detecting (S10) a current value in the photovoltaic system (1000); calculating (S20) an estimated value for an electrical power of a possible arc (1) in the photovoltaic system (1000) using a model, wherein the detected current value is used as an input variable of the model; adapting (S30) a maximum detection time duration (Tmax, Tmax,2) on the basis of the calculated estimated value for the electrical power; detecting (S40) a warning state (W) which indicates a possible occurrence of an arc (1) in the photovoltaic system (1000); continuously measuring (S50) a time duration (td) of the detected warning state (W); triggering (S70) a safety procedure when the continuously measured time duration (td) of the detected warning state (W) reaches the maximum detection time duration (Tmax, Tmax,2); and resetting (S80) the measuring (S50) of the time duration (td) of the detected warning state (W) when the detected warning state (W) comes to an end.

Description

[0001]Title: Device and Method for Operating a Photovoltaic System Field of Invention: The invention relates to a device and a method for operating a photovoltaic system, particularly in the event of a possible (i.e., apparent or actual) occurrence of an electric arc. Technical Background: Electric arcs can occur repeatedly in photovoltaic systems. Extensive standards exist that specify how quickly an electric arc must be extinguished and how frequently such an event may occur before further measures are required, such as a longer-term shutdown of the photovoltaic system, maintenance by a qualified professional, and the like. While, on the one hand, the applicable regulations must be observed, on the other hand, there is an interest in ensuring that photovoltaic systems can be operated continuously with as few restrictions as possible. For this purpose, for example, more precise methods are constantly being developed.Methods for detecting arc faults have been developed that aim to minimize false negative detections (i.e., missed detections of an actual arc fault) and false positive detections (i.e., incorrect detection of an arc fault that did not actually occur). CN 117421 651 A discloses a method for identifying arc faults, particularly in photovoltaic modules. The method consists of acquiring a power spectrum of the photovoltaic module and generating a target power spectrum. The acquired data are represented in a matrix form (feature matrix) to obtain features through deep convolution and channel shuffling. These features are then processed by multiple matrix splices and channel shuffles to reduce the dimensionality of the matrix and obtain global features. Based on this, aArc fault detected. CN 115021 209 A describes a protection mechanism against short circuits in photovoltaic systems, particularly when the short circuit is caused by a fault between lines. For this purpose, IV and PV curves are analyzed immediately after a short circuit, and the number of defective cells in the photovoltaic system is determined. Based on this, a protection mechanism is activated. In principle, this is intended, among other things, to prevent a fire caused by an arc fault. Since a definitive measurement of an arc fault is not possible in real-world photovoltaic systems, and indirect methods for arc fault detection must be used, a certain percentage of false positives (both positive and negative) can occur. If an actual arc fault is not detected, a fire can occur. A false detection where no arc fault is present results in reduced performance / poor efficiency.Customer satisfaction is paramount. Therefore, it is advisable to utilize the permitted limits / time period for detection. Various models are known for the general theoretical description of an electric arc, such as those found in the scientific publications of Hertha Marks Ayrton, "The Electric Arc," New York, D. Van Nostrand Company, 1902; J. Paukert, "The arc voltage and arc resistance of IV fault Arcs," in "Proceedings of the 7th International Symposium on Switching Arc Phenomena," 1993, pages 49-51; or A.D. Stokes and W.T. Oppenlander, "Electric arcs in open air," in "Journal of Physics D: Applied Physics," 1991, pages 26-35. According to some standards, a safety procedure must be triggered when a certain energy output of the electric arc has occurred. While this can be precisely measured in a test setup, it proves very difficult with photovoltaic systems in operation. Summary of the invention: It is an object of the present invention to provide aThe aim is to provide an improved method and an improved device for operating a photovoltaic system, in particular for dealing with possible, i.e., apparent or actual, arcing. This objective is achieved by the subject matter of the independent claims. Accordingly, according to a first aspect, a method for operating a photovoltaic system is provided, comprising the steps of: detecting a current value in the photovoltaic system; calculating an estimate of the electrical power of a possible arcing in the photovoltaic system using a model, wherein the detected current value is used as an input to the model; adjusting a maximum detection time depending on the calculated estimate of the electrical power; and detecting a warning condition indicating a possible occurrence of an arcing in the photovoltaic system (i.e., determining that an arcing may have occurred).is); Continuously measuring the duration of the detected warning condition (i.e., measuring how long the detected warning condition has lasted since its detection); Triggering a safety procedure (particularly for the purpose of extinguishing the potential arc) when the continuously measured duration of the detected warning condition reaches the maximum detection duration; and resetting the measurement of the duration of the detected warning condition when the detected warning condition ends (i.e., when another warning condition occurs, its duration is measured again from zero). A fundamental idea of ​​the present invention is thus that in a warning condition, i.e., when there are indications of an arc, a safety procedure is triggered (and preferably only precisely when) a maximum detection duration has elapsed since the occurrence of the warning condition, which, according to the invention, is not constant but adjusted.The maximum detection time is adjusted depending on a calculated estimate for the electrical power of the potential arc, with the maximum detection time advantageously decreasing monotonically or strictly monotonically with the calculated estimate for the electrical power of the potential arc. The maximum detection time can also be referred to as the "trigger time," since it indicates when the safety procedure must be triggered. This allows, for example, compliance with specifications regarding a maximum energy that the arc may emit before the safety procedure must be triggered. However, according to the invention, a particularly long time is provided before this occurs. This additional time—compared to the prior art—can be used, in particular, to carry out further measurements, for example, to determine with greater certainty whether an arc is actually present or not, in order to enable theto allow the problem to resolve itself, and / or to better assess short-term events in the photovoltaic system within their context. This additional time thus reduces, in particular, the probability of an unnecessary and disruptive intervention in the function of the photovoltaic system due to a false-positive detection of an arc flash. The term "possible arc flash" is repeatedly used in the description of the present invention. This is because, in the context of the present invention, the initial determination is only whether a warning condition exists, i.e., a condition in which an arc flash may have occurred. Various methods exist in the prior art for this purpose (e.g., spectral analyses of the photovoltaic system's power lines), all of which can be used here. During the warning condition, calculations and the like must therefore assume the presence of an arc flash.even if this might not actually be the case. Therefore, the term "power of a potential arc" is used, i.e., the power that an arc would have if the current warning condition were actually based on an arc. In other words, the "power of a potential arc" is not that of just any arc, but the power of the specific arc that is presumed to be present in the warning condition for safety reasons. The term "photovoltaic system," as used here, can include, in particular, all elements arranged between the incident solar radiation on the one hand and an AC output of an inverter on the other, i.e., in particular, photovoltaic modules, module electronics, protective devices (circuit breakers and the like), and the inverter itself. According to some preferred embodiments, variants, or refinements of embodiments, theThe maximum detection time is continuously adjusted, at least when no warning condition is detected. In other words, the method can be configured to continuously determine the current maximum detection time—roughly speaking, how long a warning condition could persist before the safety procedure would need to be triggered. During a warning condition, i.e., when a warning condition is currently detected, the adjustment of the maximum detection time can be omitted. In this case, the last adjusted maximum detection time can be used, for example, as a time threshold to determine whether or not the safety procedure should be triggered. In some embodiments, the adjustment of the maximum detection time can continue even during a warning condition. In this case, the last adjusted maximum detection time can also be one that was adjusted during the warning condition.Alternatively, when a warning condition occurs, a previously measured and stored current value can be used to calculate the maximum detection time specific to that warning condition. According to some preferred embodiments, variants, or refinements of embodiments, the model uses the detected current value as input to determine an estimate of the potential arc voltage. The estimated electrical power can then be calculated using the detected current value and the estimated electrical voltage, particularly by multiplying them. According to some preferred embodiments, variants, or refinements of embodiments, the detected current value is the only variable input to the model. In this case, the model is relatively easy and quick to compute. In alternative embodiments, variants, or refinements ofIn addition to the detected current value, other input variables can be used in embodiments, such as a voltage change upon the occurrence of a potential arc, a rise in the power spectral density, and / or the like. According to some preferred embodiments, variants, or refinements of embodiments, the model uses a plurality of candidate submodels to calculate the estimated electrical power of the potential arc. Each candidate submodel can perform its own estimate. The model's estimate of the electrical power can be based on at least one of the estimates from the candidate submodels. For example, the largest estimate (i.e., the maximum) generated by one of the candidate submodels can be used as the model's estimate. Alternatively, the model's estimate can be calculated from the estimates of the candidate submodels.For example, as their moving average or median, or as a specific quantile x (i.e., a value below which 100*x% of the candidate submodel estimates lie, where the median is the special case of the 0.5 quantile). According to some preferred embodiments, variants, or refinements of embodiments, the maximum detection time is adjusted such that a predetermined electrical energy threshold is not exceeded by the product of the estimated electrical power of the potential arc with the maximum detection time. In other words, the maximum detection time can be set such that the predetermined electrical energy threshold is just reached if the potential arc emits electrical power according to the calculated estimated electrical power for the entire maximum detection time. In this way, for example, normative requirements regarding a maximumThe energy that the potential arc may release before triggering a safety procedure is converted in such a way as to provide as much time as possible. According to some preferred embodiments, variants, or refinements of embodiments, the current value at an input of an inverter and / or module electronics and / or a protective device of the photovoltaic system is detected. The current value can thus be a measured value that is preferably detected (i.e., measured) regularly or continuously. According to some preferred embodiments, variants, or refinements of embodiments, the detected current value is a current value generated by the photovoltaic system at a time before the occurrence of the detected warning condition, for example, the last current value measured before the occurrence of the detected warning condition (i.e., before the start of the detection of the warning condition), the highest current value in a predefined range.Time window before the occurrence of the detected warning condition, or the like. According to some preferred embodiments, variants, or refinements of embodiments, the current value is recorded regularly or continuously. Accordingly, the estimated value for the electrical power can also be calculated regularly or continuously, and thus the detection time can also be advantageously adjusted regularly or continuously, always based on the most recent estimated value for the electrical power, which in turn is always based on the most recent recorded (e.g., measured) current value. According to some preferred embodiments, variants, or refinements of embodiments, the method also includes verifying the detected warning condition during a period in which the duration of the detected warning condition is between zero and the maximum detection duration. Preferably, the warning condition is terminated if theVerification reveals that no arc is present. Accordingly, the warning state advantageously remains in effect if verification does not provide a sufficiently clear result or confirm the presence of the warning state. Alternatively, confirmation of the warning state with a sufficiently high probability during verification can also trigger the immediate execution of a safety procedure (e.g., the next, the mildest, the strictest, or another predetermined safety procedure). According to a second aspect, the invention also provides a device for operating a photovoltaic system, comprising: a current measuring device configured to detect a current value; a power estimation module configured to calculate an estimated value for the electrical power of a possible (or: potential) arc using a model, wherein the detected current value serves as an input variable of theThe system consists of a model; a maximum detection duration adjustment module configured to adjust the maximum detection duration based on the calculated estimated electrical power; an arc flash detection module configured to detect a warning condition indicating a possible arc flash in the photovoltaic system; a timing device configured to continuously measure the duration of the detected warning condition; and a safety device configured to: - execute a safety procedure (particularly for the purpose of extinguishing the potential arc flash) when the continuously measured duration of the detected warning condition reaches the maximum detection duration; and - reset the timing device's measurement of the duration of the detected warning condition when the detected warning condition ends (e.g., is no longer detected).The device according to any embodiment of the second aspect can be adapted according to all embodiments, variants, or refinements of embodiments described with respect to the method according to the first aspect, and vice versa. When "modules" or "devices" are mentioned herein, it is understood that this does not necessarily mean that such modules or devices are designed as separate units. All modules and / or devices can be implemented in hardware and / or software. In cases where modules or devices are implemented as software, the modules or devices can be implemented as sections or components of program code, which may be distinguishable from one another, but which may also be interwoven. Likewise, in cases where one or more modules or devices are implemented as hardware, the functions of one or more modules or devices may be implemented in hardware.Several modules or devices can be implemented by one and the same hardware component. Alternatively or additionally, different functions of a single module or device, or even different functions of different modules or devices, can be implemented on one or more separate hardware components, which therefore do not necessarily have to be directly related to the modules or devices. In this sense, any device, system, method, etc., that possesses all the properties and functions attributed to a specific module or device can be understood as having, representing, or implementing such a module or device. In particular, it is possible that all modules and / or devices are implemented as program code executed by a computer, e.g.,from a server or cloud computing platform. According to some preferred embodiments, variants, or refinements of embodiments, the current measuring device is configured to periodically or continuously detect the current value; the power estimation module is configured to periodically or continuously calculate the estimated electrical power of the potential (or possible) arc using the detected current value; and / or the maximum detection duration adjustment module is configured to periodically or continuously adjust the maximum detection duration based on the calculated estimated electrical power. The functions of the current measuring device, the power estimation module, and the maximum detection duration adjustment module are advantageously synchronized in time and are particularly advantageously performed continuously or with the same regularity, for example, every Dmilliseconds, wherein D may advantageously lie in a range between 1 millisecond and 5 milliseconds (including the boundary values). According to a third aspect, the present invention provides an inverter comprising the device according to one embodiment of the second aspect of the present invention. According to a fourth aspect, the present invention provides a photovoltaic system comprising the device according to one embodiment of the second aspect of the present invention and / or the inverter according to one embodiment of the third aspect of the present invention. According to a fifth aspect, the present invention provides a computer program product comprising executable program code which, when executed by a computing device, performs the method according to one embodiment of the first aspect of the present invention. Such a computing device may be aAny device capable of performing calculations, and in particular of executing software, an application, or an algorithm, may be implemented or be implemented. The computing device may, for example, have at least one processing unit, such as a central processing unit (CPU) and / or a graphics processing unit (GPU) and / or a field-programmable logic gate (FPGA) and / or an application-specific integrated circuit (ASIC) and / or a combination thereof. The computing device may also have main memory operationally coupled to the at least one processing unit, as well as non-volatile memory operationally coupled to the at least one processing unit and the main memory. The computing device may be implemented wholly or entirely in a local device and / or wholly or entirely in a remote system, such as a remotely located server and / or aCloud computing platform. According to a sixth aspect, the present invention provides a non-volatile, computer-readable data storage medium comprising executable program code which, when executed by a computing device, performs the method according to an embodiment of the first aspect of the present invention. The data storage medium may, for example, be configured as or comprise a semiconductor memory, e.g., an SSD. The data storage medium may also comprise or comprise a CD, DVD, Blu-ray, or magnetic storage device. According to a seventh aspect, the present invention provides a data stream comprising, or designed to generate, executable program code which, when executed by a computing device, performs the method according to an embodiment of the first aspect of the present invention. According to aIn the eighth aspect, the present invention provides a computing device configured to carry out the method according to an embodiment of the first aspect of the present invention. Further preferred embodiments, variants, and further developments of embodiments will become apparent from the dependent claims and from the description with reference to the figures. Brief description of the figures: The invention is explained in more detail below with reference to exemplary embodiments in the figures of the drawings. The partially schematic representations show: Fig. 1 a schematic block diagram to explain a device according to an embodiment of the present invention, as well as an inverter and a photovoltaic system according to each of a further embodiment of the present invention; Fig. 2 an exemplary graph to explain the function of the device from Fig. 1; Fig. 3 a further exemplaryGraphs illustrating the function of the device from Fig. 1; Fig. 4 power spectral density spectra, one in the normal state and the other in the warning state of the device from Fig. 1; Fig. 5 another exemplary graph illustrating the function of the device from Fig. 1; Fig. 6 yet another exemplary graph illustrating the function of the device from Fig. 1; Fig. 7 another exemplary graph illustrating the function of the device from Fig. 1; Fig. 8 a schematic flowchart illustrating a method according to a further embodiment of the present invention; Fig. 9 a schematic block diagram illustrating a computer program product according to yet another embodiment of the present invention; and Fig. 10 a schematic block diagram illustrating a data storage medium according to yet another embodiment of the present invention. All figures show identical or functionally equivalent devices.Unless otherwise specified, elements and devices have been provided with the same reference numerals. The numbering of process steps is primarily for their easier differentiation and does not necessarily imply a chronological sequence, although a chronological sequence according to the numbering sequence is a possible variant. Various process steps can also be carried out partially or completely simultaneously. Multiple or iterative execution of process steps is also possible. Detailed description of the figures: Fig. 1 shows a schematic block diagram to explain a device according to an embodiment of the present invention, i.e., a device 100 for operating a photovoltaic system 1000. Thus, Fig. 1 also shows a photovoltaic system 1000 according to an embodiment of another aspect of the present invention, as well as aInverter 300 according to an embodiment of a further aspect of the present invention. The photovoltaic system 1000 shown by way of example in Fig. 1 comprises at least one photovoltaic module 200 and is shown here with two photovoltaic modules 200, whereby the photovoltaic system 1000 can also comprise significantly more photovoltaic modules 200. The photovoltaic system 1000 also comprises an inverter 300, which is configured to convert the direct current, DC, received by the photovoltaic modules 200 (or by at least one photovoltaic module 200) into alternating current, AC. The photovoltaic system 1000 can also comprise further inverters 300 as well as further elements, such as module electronics on the photovoltaic modules 200, protective devices, and the like. Furthermore, the photovoltaic system 1000 comprises a device 100 for operating the photovoltaic system 1000, the operation of which is explained in more detail below.Fig. 1 shows the device 100 arranged on or in the (or one of the) inverters 300. However, the device 100 can also be arranged on another device or distributed across multiple devices. The device 100 comprises at least one current measuring device 110, which is configured to detect a current value. The current value can be measured, for example, at an input of the inverter 300, at module electronics, and / or at a protection device of the photovoltaic system 1000. The detection of the current value can be performed regularly or continuously, as explained above, and in particular (and optionally only) when there is no current warning condition indicating a possible arc flash 1. It is understood that the at least one current measuring device 110 can also be arranged outside the inverter 300, depending on which current value is to be measured and where. Several current measuring devices 110 can be used.Current measuring devices 110 are provided, and the recorded current value can be based on individual current measurements from the multiple current measuring devices 110, e.g., a supremum, a moving average, or a quantile (e.g., a median) of the individual current measurements. The current value can, for example, be a current currently generated by the photovoltaic modules 200, measured at the maximum power point (MPP). Fig. 2 shows an example graph representing a current value I in A (amperes) as a function of time t. Initially, the photovoltaic system 1000 is operated at the MPP, so the recorded current value corresponds to IMPP, i.e., the electric current at the MPP. From time t0, an arc 1 with the arc current I is present. arcAs can be seen from Fig. 2, the preceding current value IMPP can be used as an upper limit (or supremum) for the magnitude of the subsequent arc current Iarc. Accordingly, for example, the last recorded current value before the occurrence of a detected warning condition (or, in other words, before the detection of the warning condition) can be recorded, thus determining the possible arc current I. arc is reasonably estimated. For example, a predetermined number of the most recently detected current values ​​can be stored in a buffer (e.g., current values ​​I). MPPat the maximum power point (MPP), which are then used to measure the current value. The device 100 also includes a power estimation module 120, which is configured to calculate an estimate of the electrical power of a possible (or: potential) arc 1 using a model, wherein the measured current value is used as an input to the model. Figure 1 schematically shows two types or possible locations of arc 1 formation: in the series connection between two photovoltaic modules 200, and between a photovoltaic module 200 and an inverter 300. The measured current value can be the only input to the model, or one of several. Other input variables can be, for example, a voltage change when the potential arc 1 occurs, a rise in the power spectral density, and / or the like.The power estimation module 120, in the embodiment described here, is configured to first calculate an estimate for the electrical voltage of the potential arc 1, i.e., a voltage that an arc 1 would exhibit if such an arc 1 were actually present. From the aforementioned scientific publication by J. Paukert, for example, the following formula (1) can be derived, according to which arc = (20 + 0.534 gap) a. 0 r .1 c 2 , (1) where U arcThe represents the estimated value for the electrical voltage of the potential arc 1 (English: "arc"), and Iarc is the measured current value, which is assumed here (and in the following) to be the electrical current of the potential arc 1. Here, xgap is the electrode gap in millimeters, which is typically unknown for a spontaneously occurring arc 1 (outside of a test setup) and can therefore be replaced by a fixed estimate, for example, an estimate of 0. Formula (1) shows that for typical electrode gaps in typical photovoltaic systems, the resulting uncertainty is in the single-digit percentage range. Accordingly, the estimated value Uarc for the electrical voltage of the potential arc 1 can be calculated, for example, using the following formula (2): ^^arc = 20 ^^a 0 r .1 c 2(2) In other words, the estimated value Uarc for the electrical voltage of the possible arc 1 may include or consist of a power of the detected current value multiplied by a constant. Alternatively, from a model from the above-mentioned scientific publication by HM Ayrton, the following formula (3) can be derived: ^^ = ^^ + ^^^+^^^^ gap arc ^^^gap +^^ arc , (3) where ^^ is the voltage drop across the electrode, ^^ is the voltage gradient, and ^^ and ^^ are constants that describe the non-linear impedance profile of the arc 1, which are usually determined empirically. The estimated value U arcThe electrical voltage of the potential arc 1 can thus be calculated (e.g., according to formula (3)) as a sum, where the measured current value Iarc appears in or forms the denominator of one of the summands of the sum. It is understood that, depending on the planned location and the design of the photovoltaic system 1000, other known formulas for calculating the estimated value Uarc for the electrical voltage of the potential arc 1 can also be used, for example, from the aforementioned scientific publication by Stokes and Oppenlander. From the estimated value Uarc for the electrical voltage of the potential arc 1 and the measured current value as the estimated value Iarc for the electrical current of the potential arc 1, the power estimation module 120 can be calculated according to the estimated value P arcfor the electrical power of the possible (or: potential) arc 1. A model for calculating the estimated value Parc can thus consist of, or include, a formula (or a submodel) for calculating the estimated value Uarc for the electrical voltage of the possible arc 1 in combination with formula (4). Alternatively, a model for calculating the estimated value Parc for the electrical power of the possible arc 1 can also directly be or include a formula or a submodel for a power calculation. The device 100 also has a maximum detection time adaptation module 130, which is configured to set a maximum detection time T. max to adjust depending on the calculated estimated value Parc for the electrical power. The function of the maximum detection time T maxThis was already touched upon previously and will be described in more detail below. The model for calculating the estimated value P arcFor electrical power, a plurality of candidate submodels can be used, with each candidate submodel performing its own estimation and the model's electrical power estimate based on at least one of the candidate submodel estimates. For example, the largest estimate (i.e., the maximum) generated by one of the candidate submodels can be used as the model's estimate. Alternatively, the model's estimate can be calculated from the candidate submodel estimates, for example, as their moving average or median, or as a specific quantile x (i.e., a value below which 100*x% of the candidate submodel estimates lie, where the median is the special case of the 0.5 quantile).Equivalently, a plurality of candidate sub-models can be used to generate the estimated value Uarc for the electrical voltage of the possible arc 1, where the candidate sub-models each provide estimates for and the estimated value for. which is then used to calculate the estimated value for performance, from the estimates of the candidate sub-models for The value is calculated, for example, as their moving average or median, or as a specific quantile x. The device 100 also includes an arc detection module 140, which is configured to detect a warning condition indicating a possible occurrence of an arc 1 in the photovoltaic field. In other words, a warning condition exists, for example, when, for safety reasons, it must be assumed that an arc 1 is present, even if it is not known whether this is actually the case. The detection of the warning condition by the arc detection module 140 can be carried out according to any prior art method for detecting an arc 1 and may, for example, include a Fourier transform and a spectral analysis. Fig.Figure 3 shows a graph where the vertical axis represents the frequencies (in kHz) of electrical signals in at least one conductor of the photovoltaic system 1000, the horizontal axis shows the time course (in ms), and the colored dots indicate the intensity (in dB) of the signals at a specific frequency at a specific time, with darker colors indicating higher intensity. The electrical signals can be tapped, for example, in a negative conductor of the photovoltaic system 1000 (e.g., in a common negative conductor), and depending on the topology, other and / or multiple measurement points are also possible. Figure 3 shows an exemplary and schematic frequency range between 0 kHz and 100 kHz on the vertical axis. It is understood that a wider, narrower, and / or shifted frequency range (or several separate sub-frequency ranges) can also be used for detecting a warning condition W.The photovoltaic system 1000 according to the invention can advantageously include powerline communication for control or communication signals without this impairing the functions of the device 100 in any way. Figure 3 clearly shows how the general frequency behavior in the photovoltaic system 1000 changes abruptly at time t0, and in particular how the overall intensities are significantly higher. Since arcs 1 typically generate pink noise (similar to "white noise") in the electromagnetic spectrum, this can be considered an indication of the occurrence of an arc 1 at time t0. Accordingly, the arc detection module 140 can be configured to detect the presence of a warning condition W at time t0. Figure 4 shows two graphs by way of example, one of which is the power spectral density FN in the normal state N of the photovoltaic system 1000, and the other a power spectral density F. WThe graph represents the warning state W of the photovoltaic system 1000. Accordingly, the graph can be used with the frequency spectrum F. N for example as a vertical cross-section through Fig. 3 in the region of the normal state N e.g. at 1200 ms, and the graph with the frequency spectrum F W For example, it can be considered as a vertical cross-section in the area of ​​the warning condition W, e.g., at 1700 ms. Typically, standards stipulate that a safety procedure, such as shutting down the photovoltaic system 1000, does not have to be executed immediately upon the occurrence of a warning condition W (i.e., upon detection of a possible arc flash). Often, as explained above, a maximum energy quantity E is instead specified. max admitted, i.e., that an electrical energy E emitted by the (possible, or: alleged) arc 1 arc maximum value E maxThe maximum power that may be reached before the safety procedure must be executed is shown in Fig. 5. One graph represents the power Parc of the possible arc 1 (left vertical axis, in watts), and the other represents the total energy E released by arc 1. arc (right vertical axis, in joules), each as a function of time. The total energy output can be calculated by integrating the power P arc to be calculated. According to the invention, it is now exploited that a known estimated value for the power P can be used. arc The maximum detection time Tmax of the possible arc 1 can be calculated from a specification for the maximum energy quantity Emax by the detection maximum duration adaptation module 130. This thus indicates how long a warning condition W may be tolerated (or: can be tolerated) before the required safety procedure must be triggered, whereby in a simple case the following can apply: , where E arca constant, U arc The estimated value for the electrical voltage of the potential arc 1 and Iarc the estimated value for the electric current, given by the detected current value (or calculated based on the detected current value) of the potential arc 1, are shown. Fig. 6 shows a version of the graph in Fig. 3, in which, among other things, the maximum detection time Tmax (corresponding in the present example to an energy output of Earc = 200 J from the arc 1) has been additionally shown with a vertical line. It is understood that, according to the invention, the maximum detection time T max(at least when no warning condition W is currently present, optionally always) is adjusted by the detection maximum duration adjustment module 130, in particular regularly or, more preferably, continuously, depending on the currently detected current value, which can accordingly also be detected (in particular measured) regularly or preferably continuously. Fig. 7 shows an example graph illustrating how the detection maximum duration T is adjusted. max Depending on the currently recorded current value I1, I2, I3, the detection maximum duration adjustment module 130 adjusts accordingly, with I1 <I2<I3. Es kann ein Detektionshöchstzeitdauer- Standardwert Tmax,0 vorgesehen sein, welcher für die Detektionshöchstzeitdauer T maxThis is used when no usable detected current value is currently available. For example, the detection maximum duration adjustment module 130 can be configured to use the detection maximum duration default value Tmax,0 if the detected current value is not considered plausible (i.e., predetermined plausibility rules are not met), is too old (i.e., older than a predetermined duration), no detected current value is available at all (e.g., in the case of a communication error), and / or similar reasons. The device 100 also includes a timing device 150, which is configured to measure a continuous duration td of the detected warning condition W, or, in other words, to measure how long the detected warning condition W has persisted.This can be achieved, for example, by starting a counter Z at the beginning of the detection of the warning condition W, which counts fixed time intervals D (for example, with D in the range between 1 and 5 milliseconds, including the extreme values), i.e., td = Z*D starting at t0. Alternatively, this can be achieved by recording the absolute time t0 of the detection of the warning condition W and subtracting this recorded absolute time from the current time t, i.e., td = t-t0. The device 100 also includes a safety device 160, which is configured to execute a safety procedure for the purpose of extinguishing the potential arc 1 when the continuously measured duration td of the detected warning condition W reaches the maximum detection duration Tmax, i.e., td = Tmax.Preferably, no safety procedure is triggered (or only a different, in particular milder, safety procedure is triggered) as long as td ≤ T. max In particular, preferably no photovoltaic module 200 or the entire photovoltaic system 1000 is switched off as long as td ≤ T max As Fig. 7 illustrates particularly well, the safety procedure is thus triggered relatively earlier when a relatively large current value I3 is detected, and relatively later when a relatively small current value I1 is detected, since the maximum detection time T maxThe safety procedure is modified accordingly. It can include one or more measures (known from the prior art) aimed at extinguishing the potential arc flash 1, up to and including shutting down the photovoltaic system 100. The safety procedure can include sending a message to a central control unit, for example, to a virtual power plant operator, a maintenance person, and / or the like. The safety device 160 can be configured to reset the time measurement td of the detected warning condition W by the timing device 150 when the detected warning condition W ends, i.e., is no longer detected, or in other words, when the indications that suggested the occurrence of an arc flash are no longer present (to a sufficient degree).Advantageously, the period during which the duration td of the detected warning state W increases between 0 and the maximum detection duration Tmax is used by the arc detection module 140 to (further) verify the detected warning state W, i.e., to determine whether an arc 2 is actually present or not. For this purpose, additional measurements (such as of the frequency spectrum) can be taken, additional current values ​​can be recorded, additional models can be applied and their results analyzed (e.g., a machine learning model such as an artificial intelligence entity, for example, an artificial neural network), more time-consuming calculations than those performed for the initial detection of the warning state W can be carried out, and / or similar measures can be taken. If the verification shows that no arc 2 is actually present, the warning state W is preferably terminated immediately, so that, ideally, the process can continue in the normal state N.If, despite (or during) verification, a warning condition W persists (i.e., in particular, an arc flash 2 is considered possible or probable), the detected warning condition W remains in effect, and the time duration td continues to increment. Multiple maximum detection time durations T are also possible. max The safety device 160 is designed to trigger a different and / or additional and / or renewed safety procedure at each successively reached maximum detection time Tmax, typically with increasing effectiveness in extinguishing the arc 1 but simultaneously with a stronger intervention in the function of the photovoltaic system 1000. In Fig. 6, for example, next to the first maximum detection time T max, which here corresponds to an (exemplary) maximum energy of Earc=200 J, and a second maximum detection time T max,2The diagram shows a (model) maximum energy of Earc = 750 J. Therefore, the safety device 160 can be configured to initially detect the warning state when the continuously measured duration td of the warning state W exceeds the first maximum detection time T. max reached (i.e., when td=T max (is) to execute a first, less severe safety procedure. In the event that this safety procedure was insufficient to resolve the warning condition W (i.e., the possibility of an arc flash 1 still exists in the assessment of the arc flash detection module 140), the timing device 150 continues to measure (or: count). When the continuously measured duration td of the detected warning condition W then reaches the second maximum detection duration Tmax,2 (i.e., td = T max,2If a second, more stringent safety procedure is executed, such as shutting down the photovoltaic system 1000 (e.g., using one or more DC and / or AC disconnectors), automatically requesting maintenance personnel, and / or similar measures, the (relatively) milder safety procedure might involve, for example, temporarily reducing the DC power consumption via the lines associated with the detected current value (e.g., from the photovoltaic modules 200), for instance, to a value below a threshold between 200 mA and 300 mA (e.g., below a threshold of 250 mA). If several maximum detection times Tmax, Tmax,2, each linked to different safety procedures (i.e., differing in at least one safety procedure), are provided, preferably all provided maximum detection times Tmax, Tmax,2, are adjusted simultaneously.However, it may also be provided that at least a longer maximum detection time duration Tmax,2 is adjusted less frequently than at least a shorter maximum detection time duration T. max For example, it may be provided that the at least one longer maximum detection time duration Tmax,2 is only adjusted if a warning condition W has already been present for a time duration td between 0 and the at least one shorter maximum detection time duration T maxFig. 8 shows a schematic flowchart to illustrate a method according to a further embodiment of the present invention, i.e., a method for operating a photovoltaic system 1000. The method can be carried out, in particular, with the device 100 according to the invention and / or in the photovoltaic system 1000 according to the invention, but also independently thereof. Accordingly, the method can be adapted according to all options, variants, and refinements described with respect to the device 100 according to the invention and the photovoltaic system 1000 according to the invention, and vice versa. Accordingly, reference is also made to reference numerals in the preceding Figs. 1-7 in the description of the method according to Fig. 8, without this being understood as a limitation.In step S10, a current value is recorded in the photovoltaic system 1000, for example, as explained above with reference to the function of the current measuring device 110. The recorded current value is preferably recorded (in particular measured) regularly or continuously, at least while no warning condition W exists, and is particularly preferably a current value generated by the photovoltaic system 1000 at a time before the occurrence of the detected warning condition W. In the case of several module strings of the photovoltaic system 1000, the present method can be carried out for all module strings together or for each module string individually. Accordingly, the recorded current value can also be, for example, a current value at one of the module strings. In step S20, an estimated value P is obtained. arcThe electrical power of a potential arc 1 in the photovoltaic system 1000 is calculated using a model, where the detected current value is used as an input (either the only one or one of several inputs) of the model, as described above with reference to the power estimation module 120. In step S30, a maximum detection time Tmax,Tmax,2 is calculated as a function of the calculated estimate P. arcfor the electrical power, for example as explained above with reference to the detection maximum duration adaptation module 130. This can be done regularly or continuously, at least if no warning condition W is currently present (i.e., no warning condition W is detected). In step S40, a warning condition W is detected, indicating a possible occurrence of an arc flash 1 in the photovoltaic system 1000, as explained above with reference to the arc flash detection module 140. As already explained, one of the methods known in the prior art can be used for this purpose, for example based on a spectral analysis of the current from the photovoltaic system 1000 (more precisely: from one or more photovoltaic modules 200) or the like.In step S50, the duration td of the detected warning condition W, if one exists, is continuously measured, approximately as explained above with reference to the timing device 150. In step S60, the period during which the duration td of the detected warning condition W is between 0 and the maximum detection duration T is measured. maxThe process, which runs up, is used to verify the detected warning condition W, i.e., to determine with higher accuracy (or even with certainty) (or at least to make the best possible attempt) whether an arc flash 2 is actually present or not. For this purpose, additional measurements (such as of the frequency spectrum) can be taken, additional models applied and their results analyzed (e.g., a machine learning model such as an artificial intelligence entity, for example, an artificial neural network), more time-consuming calculations than those performed for the initial detection S40 of the warning condition W, and / or similar measures. Verification S60 can also be performed, for example, by the arc flash detection module 140.If verification S60 confirms that no arc 2 is present, the warning state W is preferably terminated immediately, allowing the process to ideally continue in the normal state N – see also step S80 below. Verification S60 preferably continues until the maximum detection time Tmax is reached, thus maximizing the chances of avoiding the triggering of an unnecessary safety procedure. During verification S60, data can be continuously aggregated to regularly (or iteratively) produce an increasingly reliable result. If, despite (or during) verification S60, a warning state W persists (i.e., in particular, if an arc 2 is considered possible or probable), the detected warning state W remains in effect, and the time duration td continues to increment continuously (in the continuously running step S50).In an optional variant, if the presence of arc 2 is confirmed with certainty (or with a probability above a threshold) during verification S60, a safety procedure can also be triggered immediately. In step S70, a safety procedure, specifically for the purpose of extinguishing the potential arc 1, is triggered if the continuously measured duration td of the detected warning condition W exceeds the maximum detection time T. maxachieved, approximately as described above with reference to the safety device 160. The safety procedure may, for example, involve reducing the current generated by one or more (or all) photovoltaic modules 200, switching off one or more (or all) strings of the photovoltaic system 100, or the entire photovoltaic system 100, or the like. During the warning state, as long as the maximum detection time T maxIf the warning state has not yet been reached, operation of the photovoltaic system 1000 can continue unchanged. In this way, if the warning state W turns out to be a false positive, the operation of the photovoltaic system 1000 can be prevented from being disruptively restricted. In step S80, the measurement S50 of the duration td of the detected warning state W is reset when the detected warning state W ends, similar to what was described above with reference to the safety device 160. Thus, the photovoltaic system 1000 is returned to its initial state (the normal state N) when a warning state W is no longer detected, and the process can continue continuously. Preferably, the maximum detection time Tmax is continuously (or dynamically) adjusted during the normal state N, while the last determined maximum detection time T is used during the warning state W.maxThe invention is recorded and used. Fig. 9 shows a schematic block diagram of a computer program product 400 according to an embodiment of the present invention. The computer program product 400 comprises executable program code 450, which, when executed, is configured to perform the method according to an embodiment of the present invention, for example, according to Fig. 8. Fig. 10 shows a schematic block diagram of a non-volatile, computer-readable data storage medium 500 according to an embodiment of the present invention. The data storage medium 500 comprises executable program code 550, which, when executed, is configured to perform the method according to an embodiment of the present invention, for example, according to Fig. 8. The non-volatile, computer-readable data storage medium 300 can, for example, be configured as or comprise a semiconductor memory, e.g., an SSD.The data storage medium 300 may also include or comprise a CD, DVD, Blu-Ray or a magnetic storage device.

Claims

Claim 1. A method for operating a photovoltaic system (1000), comprising the steps of: acquiring (S10) a current value in the photovoltaic system (1000); calculating (S20) an estimated value for the electrical power of a possible arc (1) in the photovoltaic system (1000) using a model, wherein the acquired current value is used as an input to the model; adjusting (S30) a maximum detection time duration (Tmax,Tmax,2) depending on the calculated estimated value for the electrical power; detecting (S40) a warning condition (W) indicating a possible occurrence of an arc (1) in the photovoltaic system (1000); continuously measuring (S50) a time duration (td) of the detected warning condition (W); Triggering (S70) of a safety procedure when the continuously measured duration (td) of the detected warning condition (W) exceeds the maximum detection time (T). max, T max,2) reached; and resetting (S80) the measurement (S50) of the duration (td) of the detected warning state (W) when the detected warning state (W) ends.

2. Method according to claim 1, wherein the maximum detection time duration (Tmax, Tmax, 2) is continuously adjusted, at least when no warning state (W) is detected.

3. Method according to claim 1 or 2, wherein in the model, using the detected current value as an input, an estimate for the electrical voltage of the possible arc (1) is determined, and the estimate for the electrical power is calculated using the detected current value and the estimate for the electrical voltage, in particular by multiplying them.

4. Method according to any one of claims 1 to 3, wherein the detected current value is the only variable input of the model.

5. Method according to any one of claims 1 to 4, wherein the model uses a plurality of candidate submodels for calculating the estimate for the electrical power, each candidate submodel performing its own estimate, and the model's estimate for the electrical power is based on at least one of the estimates of the candidate submodels.

6. Method according to any one of claims 1 to 5, wherein the maximum detection time (T) max, T max,2) is adjusted such that the estimated value for the electrical power of the possible arc is multiplied by the maximum detection time (T). max, T max,2 ) a predetermined electrical energy threshold is not exceeded.

7. Method according to any one of claims 1 to 6, wherein the current value at an input of an inverter (300) and / or module electronics and / or a protection device of the photovoltaic system (1000) is detected.

8. Method according to claim 7, wherein the detected current value is a current value generated by the photovoltaic system (1000) at a time prior to the occurrence of the detected warning condition (W).

9. Method according to claim 7 or 8, wherein the current value is detected regularly or continuously, the estimated value for the electrical power is calculated regularly or continuously, and the detection time is adjusted regularly or continuously.

10. Method according to any one of claims 1 to 9, further comprising verifying (S60) the detected warning condition (W) during a period in which the duration (td) of the detected warning condition (W) is between zero and the maximum detection duration (T). max) is, preferably terminating the warning state (W) if verification (S60) shows that there is in fact no arc (2).

11. Device (100) for operating a photovoltaic system (1000), comprising: a current measuring device (110) configured to detect a current value; a power estimation module (120) configured to calculate an estimate for the electrical power of a possible arc (1) using a model, wherein the detected current value is used as an input to the model; a maximum detection time adaptation module (130) configured to set a maximum detection time (T) max, T max,2 ) depending on the calculated estimated value for the electrical power; an arc detection module (140) which is configured to detect a warning condition (W), which indicates a possible occurrence of an arc flash (1) in the photovoltaic system (1000); a timing device (150) configured to measure a continuous duration (td) of the detected warning condition (W); and a safety device (160) configured to: - execute a safety procedure for the purpose of extinguishing the possible arc flash (1) when the continuously measured duration (td) of the detected warning condition (W) reaches the maximum detection duration (Tmax,Tmax,2); and - reset the measurement of the duration (td) of the detected warning condition (W) by the timing device (160) when the detected warning condition (W) ends. 12.Device (100) according to claim 11, wherein the current measuring device (110) is configured to regularly or continuously detect the current value; the power estimation module (120) is configured to regularly or continuously calculate the estimated value for the electrical power of the potential arc (1) using the detected current value; and / or the maximum detection duration adjustment module (130) is configured to regularly or continuously adjust the maximum detection duration (Tmax, Tmax, 2) depending on the calculated estimated value for the electrical power.

13. Inverter (300) comprising the device according to claim 11 or 12.

14. Photovoltaic system (1000) comprising the device (100) according to claim 11 or 12 and / or the inverter according to claim 13.

15. Computer program product (400) comprising executable program code (450) which, when executed by a computing device, performs the method according to any one of claims 1 to 10.

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