Fault detection method of photovoltaic system, operation control device and photovoltaic system

Abstract

The invention discloses a fault detection method of a photovoltaic system, an operation control device, the photovoltaic system and a computer readable storage medium, and the photovoltaic system comprises an inverter and a photovoltaic loop. The photovoltaic loop comprises a photovoltaic module, a direct current cable connecting the photovoltaic module and the inverter and an arc detection sensor arranged at the joint of the direct current cable and the inverter, and the method comprises the following steps: when the direct current cable has an arc discharge fault, obtaining a fault recording wave of the arc detection sensor, the fault recording comprises a normal alternating current signal before an arc discharge fault occurs and a traveling wave signal after the arc discharge fault occurs; performing wavelet transform processing on the fault record to obtain a fault feature of the traveling wave signal; and performing conversion processing according to the fault characteristics to obtain positioning information of the arc discharge fault. Physical positioning of an arc discharge fault can be realized, and timely maintenance and processing are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a fault detection method, an operation control device, a photovoltaic system and a computer-readable storage medium for a photovoltaic system. Background Art

[0002] With the rapid development of new energy and the growing prosperity of the photovoltaic industry, the demand for photovoltaic grid-connected inverters and energy storage inverters has increased. At the same time, hazardous events such as fires caused by DC arcing faults have also emerged. In order to detect DC arcing faults in time and reduce the hazards, various DC arcing detection technologies have emerged.

[0003] At present, the mainstream DC arc detection is to measure the spectrum of DC current. When the amplitude of certain frequency bands of the spectrum reaches a certain threshold, it is determined that a DC arc fault has occurred. However, there is no good detection technology for the physical location of the DC arc fault. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a photovoltaic system fault detection method, an operation control device, a photovoltaic system and a computer-readable storage medium, which can realize the physical positioning of arc faults.

[0005] In a first aspect, an embodiment of the present invention provides a fault detection method for a photovoltaic system, wherein the photovoltaic system includes an inverter and a photovoltaic circuit, wherein the photovoltaic circuit includes a photovoltaic component, a DC cable connecting the photovoltaic component and the inverter, and an arc detection sensor disposed at a connection between the DC cable and the inverter, wherein the method includes:

[0006] When an arcing fault occurs in the DC cable, a fault recording of the arc detection sensor is obtained, wherein the fault recording includes a normal AC signal before the arcing fault occurs and a traveling wave signal after the arcing fault occurs;

[0007] Performing wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal;

[0008] The conversion process is performed according to the fault characteristics to obtain the location information of the arcing fault.

[0009] The fault detection method for a photovoltaic system provided in accordance with an embodiment of the present invention has at least the following beneficial effects: when an arcing fault occurs in a DC cable connecting a photovoltaic module and an inverter, an arc detection sensor arranged at the connection between the DC cable and the inverter records the signals before and after the arcing fault occurs to obtain a fault recording, which is then processed by wavelet transform. Since a traveling wave signal of a specific frequency is generated and transmitted on the DC cable when an arcing fault occurs, wavelet transform processing of the fault recording can extract the fault characteristics of the traveling wave signal after the arcing fault occurs. Finally, after conversion processing, the positioning information of the arcing fault is obtained, thereby enabling the physical positioning of the arcing fault to be achieved, which is conducive to timely maintenance and processing.

[0010] According to the fault detection method provided by some embodiments of the present invention, the performing wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal includes:

[0011] Select wavelet basis function;

[0012] Decomposing the transformation formula of continuous wavelet transform of the wavelet basis function combined with the fault recording to obtain the first duration and the second duration of the traveling wave signal;

[0013] Among them, the first time length is the time length for the traveling wave signal to be transmitted directly from the fault location to the arc detection sensor; the second time length is the time length for the traveling wave signal to be transmitted from the fault location to the photovoltaic component and then reflected to the arc detection sensor.

[0014] According to some embodiments of the present invention, the fault detection method provides a method of converting the fault characteristics to obtain the location information of the arcing fault, including:

[0015] Multiplying the difference between the second time length and the first time length by the transmission speed of the traveling wave signal in the DC cable and dividing the result by 2 to obtain a first distance between the fault location and the photovoltaic component;

[0016] The first distance is subtracted from the length of the DC cable to obtain a second distance between the fault location and the inverter.

[0017] According to the fault detection method provided by some embodiments of the present invention, the wavelet basis function is:

[0018]

[0019] Where: a is the scale coefficient, a≠0, and b is the time position parameter.

[0020] According to the fault detection method provided by some embodiments of the present invention, the transformation formula of the continuous wavelet transform is:

[0021]

[0022] Wherein, f(t) is the signal of the fault recording with R=(-∞, +∞), R represents the value range; ω f(a,b) is the wavelet signal of f(t); ψ(t) is the basic wavelet, ψ * (a,b) is the conjugate of ψ(a,b); a∈R, b∈R.

[0023] The fault detection method provided according to some embodiments of the present invention further includes:

[0024] Acquire the original AC signal collected by the arc detection sensor, and perform bandpass filtering and discrete Fourier transform processing to obtain the fundamental amplitude of the original AC signal;

[0025] When the fundamental wave amplitudes within the first preset time period are all greater than a first preset threshold, it is determined that an arc fault occurs in the DC cable.

[0026] According to the fault detection method provided in some embodiments of the present invention, the photovoltaic circuit is provided with multiple ones. When the fundamental frequencies of the original AC signals of two photovoltaic circuits are consistent, the fundamental amplitudes are both greater than the first preset threshold and the difference between the two fundamental amplitudes is less than the second preset threshold, it is determined that a parallel arc fault occurs in the photovoltaic system.

[0027] According to the fault detection method provided by some embodiments of the present invention, when the voltage difference transmitted from the DC cable to the inverter before and after the arcing fault occurs is greater than a third preset threshold, it is determined that a grounding arcing fault occurs in the DC cable.

[0028] According to the fault detection method provided by some embodiments of the present invention, when the arcing fault that occurs does not belong to a parallel arcing fault and a grounding arcing fault, it is determined that a series arcing fault occurs in the DC cable.

[0029] In a second aspect, an embodiment of the present invention provides an operation control device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the photovoltaic system fault detection method as described in the embodiment of the first aspect above.

[0030] In a third aspect, an embodiment of the present invention provides a photovoltaic system, comprising an operation control device as described in the embodiment of the second aspect above.

[0031] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the photovoltaic system fault detection method as described in the embodiment of the first aspect above.

[0032] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0034] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0035] Figure 1 is a schematic diagram of a photovoltaic system provided by an embodiment of the present invention;

[0036] Figure 2 is a flow chart of a photovoltaic system fault detection method provided by an embodiment of the present invention;

[0037] Figure 3 yes Figure 2 A detailed flowchart of step S220 in FIG.

[0038] Figure 4 It is a schematic diagram of the principle of positioning when an arc fault occurs in a photovoltaic system provided by an embodiment of the present invention;

[0039] Figure 5 yes Figure 2 A detailed flowchart of step S230 in FIG.

[0040] Figure 6 is a flow chart of a photovoltaic system fault detection method provided by another embodiment of the present invention;

[0041] Figure 7 is a flow chart of a photovoltaic system fault detection method provided by a specific embodiment of the present invention;

[0042] Figure 8 It is a structural schematic diagram of the operation control device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0043] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0044] In the description of the embodiments of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, "above", "below", "within", etc. are understood to include the number itself, "at least one" means one or more, "at least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. If there is a description of "first", "second", etc., it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0045] It should be noted that the terms such as setting, installing, and connecting in the embodiments of the present invention should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the embodiments of the present invention in combination with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or mutual communication; it can be directly connected or indirectly connected through an intermediate medium.

[0046] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0047] At present, the mainstream DC arc detection is to measure the spectrum of DC current. When the amplitude of certain frequency bands of the spectrum reaches a certain threshold, it is determined that a DC arc fault has occurred. However, there is no good detection technology for the physical location of the DC arc fault.

[0048] The embodiments of the present invention provide a photovoltaic system fault detection method, an operation control device, a photovoltaic system and a computer-readable storage medium, which can realize the physical positioning of arc faults.

[0049] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0050] Figure 1 Schematic diagram of a photovoltaic system provided by an embodiment of the present invention. Figure 1 The photovoltaic system includes an inverter 100 and a photovoltaic circuit 200 , and the photovoltaic circuit 200 includes a photovoltaic component 210 , a DC cable 220 connecting the photovoltaic component 210 and the inverter 100 , and an arc detection sensor 230 arranged at the connection between the DC cable 220 and the inverter 100 .

[0051] It is understandable that a plurality of photovoltaic circuits 200 may be provided in the photovoltaic system. Accordingly, the inverter 100 also includes multiple MPPT circuits, and the DC cables 220 of each photovoltaic circuit 200 are respectively connected to one MPPT circuit of the inverter 100. Each photovoltaic circuit 200 uses an arc detection sensor 230 to collect the original AC signal, such as collecting the original current signal or collecting the original voltage signal. Among them, the arc detection sensor 230 may use a wide-bandwidth current transformer, a Rogowski coil, or directly use a Hall sensor; the Hall sensor may collect the original current signal; the wide-bandwidth current transformer or the Rogowski coil may directly eliminate the DC component and retain only the AC component when a DC arc fault occurs.

[0052] It should be noted that if Figure 1 As shown, when an arc fault occurs in the DC cable 220, the high-frequency arc generated at the fault point will radiate from the fault point to both ends of the cable and the surrounding space. The high-frequency electromagnetic signals radiated in the space are easily affected by the external environment, and the high-frequency signals transmitted along both ends of the cable are easier to capture. Experience shows that the current and voltage frequencies of DC arcing are generally between 100kHz and 200kHz.

[0053] Reference Figure 2 The first aspect of the present invention provides a photovoltaic system fault detection method, including but not limited to steps S210 to S230:

[0054] Step S210: When an arc fault occurs in the DC cable 220, a fault recording of the arc detection sensor 230 is obtained, where the fault recording includes a normal AC signal before the arc fault occurs and a traveling wave signal after the arc fault occurs;

[0055] After an arc fault occurs in the DC cable 220, the voltage or current at the fault point changes suddenly, and a voltage traveling wave or a current traveling wave is generated under the action of the fault voltage component and propagates along both ends of the DC cable 220. The traveling wave will be refracted and reflected at the wave impedance discontinuity point, such as the connection port between the DC cable 220 and the photovoltaic module 210, the fault point, and the connection port between the DC cable 220 and the inverter 100, so the location of the arc fault point can be measured by using the refraction and reflection principle of the traveling wave, that is, the arc fault distance can be measured by using the arrival time difference between the traveling wave head and the reflected wave head.

[0056] Step S220: performing wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal;

[0057] Step S230: Perform conversion processing according to the fault characteristics to obtain the location information of the arcing fault.

[0058] According to the fault detection method for a photovoltaic system provided by an embodiment of the present invention, when an arcing fault occurs in a DC cable 220 connecting a photovoltaic assembly 210 and an inverter 100, an arc detection sensor 230 arranged at the connection between the DC cable 220 and the inverter 100 records the signals before and after the arcing fault occurs to obtain a fault recording, which is then processed by wavelet transform. Since a traveling wave signal of a specific frequency is generated when an arcing fault occurs and transmitted on the DC cable 220, the fault recording is processed by wavelet transform to extract the fault characteristics of the traveling wave signal after the arcing fault occurs. Finally, the location information of the arcing fault is obtained after conversion processing, thereby realizing the physical location of the arcing fault, which is conducive to timely maintenance and processing.

[0059] Reference Figure 3 In the fault detection method provided in some embodiments of the present invention, the step S220 performs wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal, including but not limited to steps S310 to S320:

[0060] Step S310: Selecting a wavelet basis function;

[0061] Step S320: Decomposing the transformation formula of continuous wavelet transform of wavelet basis function combined with fault recording to obtain the first duration and the second duration of the traveling wave signal;

[0062] Among them, the first time length is the time length that the traveling wave signal is directly transmitted from the fault location to the arc detection sensor 230; the second time length is the time length that the traveling wave signal is transmitted from the fault location to the photovoltaic component 210 and then reflected to the arc detection sensor 230.

[0063] Reference Figure 4 , Figure 4 The schematic diagram is a principle diagram for positioning when an arc fault occurs in a photovoltaic system. When an arc fault occurs at the position shown in the figure, a traveling wave signal of a specific frequency will be generated at the fault location. On the one hand, the traveling wave signal is directly transmitted from the fault location along the DC cable 220 to the inverter 100, so as to be measured by the arc detection sensor 230; on the other hand, it is first transmitted from the fault location along the DC cable 220 to the photovoltaic module 210, then reflected, and then transmitted from the photovoltaic module 210 to the inverter 100 along the DC cable 220, so as to be measured by the arc detection sensor 230. By recording the fault waveform and then performing a wavelet transform, the fault characteristics of the traveling wave signal can be extracted, and the duration of the traveling wave signal of the specific frequency being transmitted twice to the arc detection sensor 230 is recorded, that is, the first duration t1 and the second duration t2.

[0064] It should be noted that by performing wavelet transform on the fault filter detected by the arc detection sensor 230, the frequency component of the traveling wave signal and the specific position of the frequency component in the time domain can be known.

[0065] Reference Figure 5 In the fault detection method provided in some embodiments of the present invention, the conversion process is performed according to the fault characteristics in step S230 to obtain the location information of the arcing fault, including but not limited to steps S510 to S520:

[0066] Step S510: multiplying the difference between the second time length and the first time length by the transmission speed of the traveling wave signal in the DC cable 220 and dividing the result by 2 to obtain a first distance between the fault location and the photovoltaic assembly 210;

[0067] Step S520 : subtract the first distance from the length of the DC cable 220 to obtain a second distance between the fault location and the inverter 100 .

[0068] Reference Figure 4 , x1 is the distance between the fault location and the photovoltaic module 210, that is, the first distance in step S510; x2 is the distance between the fault location and the inverter 100, that is, the second distance in step S520. In addition, the length of the DC cable 220 is denoted as s, which is a known quantity. From the figure, it can be seen that the first distance x1, the second distance x2, the DC cable length s, the first time length t1, and the second time length t2 satisfy the following mathematical relationship:

[0069] x1+x2=s;

[0070] v*(t2-t1)=2x1;

[0071] Wherein, v is the transmission speed of the traveling wave signal in the DC cable 220. It is understandable that the transmission speed of the traveling wave signal in the DC cables 220 of different wire diameters is different, and the wave speed of the traveling wave signal in the cable, that is, the transmission speed, is mainly obtained through actual measurement in engineering, and then written into the MCU connected to the arc detection sensor 230.

[0072] In the fault detection method provided in some embodiments of the present invention, the wavelet basis function is:

[0073]

[0074] Where: a is the scale coefficient, a≠0, and b is the time position parameter.

[0075] In the fault detection method provided in some embodiments of the present invention, the transformation formula of the continuous wavelet transform is:

[0076]

[0077] Wherein, f(t) is the signal of the fault recording with R=(-∞, +∞), R represents the value range; ω f(a,b) is the wavelet signal of f(t); ψ(t) is the basic wavelet, ψ * (a,b) is the conjugate of ψ(a,b); a∈R, b∈R.

[0078] It is understandable that the wavelet basis function may be a db7 wavelet basis function or other commonly used wavelet basis functions. Wavelet transform can decompose the arc or voltage sag time when an arc fault occurs in the DC cable 220, thereby accurately locating the fault.

[0079] In addition, in order to ensure the integrity of the recorded waveform, the fault waveform to be recorded should include the waveform of the t3 time period before the fault to ensure accurate analysis. The length of the t3 time period before the fault can be determined based on the size of the memory resources of the MCU.

[0080] Reference Figure 6 In some embodiments of the present invention, the fault detection method further includes step S610 and step S620:

[0081] Step S610: acquiring the original AC signal collected by the arc detection sensor 230, and performing bandpass filtering and discrete Fourier transform processing to obtain the fundamental amplitude of the original AC signal;

[0082] Step S620: When the fundamental wave amplitudes within the first preset time period are all greater than the first preset threshold, it is determined that an arc fault occurs in the DC cable 220 .

[0083] In this embodiment, the original AC signal collected by the arc detection sensor 230 can be band-pass filtered by a band-pass filter to ensure that the signal frequency is between 100kHz and 200kHz, and the data is digitally processed by a DSP processor, and the fundamental amplitude and fundamental frequency of the original AC signal are determined by discrete Fourier transform processing. If the fundamental amplitude is greater than the first preset threshold, it can be preliminarily determined that a DC arc is generated on the photovoltaic circuit 200. Since the DC arc is difficult to eliminate by itself without a disconnecting device, a first preset time length t4 is set, and the DC circuit is continuously judged within the t4 time period. If the fundamental amplitude is always greater than the first preset threshold, it is determined that a DC arc has occurred in the circuit.

[0084] In the fault detection method provided in some embodiments of the present invention, the photovoltaic circuit 200 is provided with multiple, for example, Figure 1When the fundamental frequencies of the original AC signals of the two photovoltaic circuits 200 are consistent, the fundamental amplitudes are both greater than the first preset threshold, and the difference between the two fundamental amplitudes is less than the second preset threshold, it is determined that a parallel arc fault occurs in the photovoltaic system.

[0085] It can be understood that when the fundamental wave amplitudes obtained by bandpass filtering and discrete Fourier transform processing of the original AC signals of the two photovoltaic circuits 200 are greater than the first preset threshold, it means that arcing faults have occurred in both photovoltaic circuits 200. When the two photovoltaic circuits 200 do not have a parallel arcing fault, that is, the locations where the arcing faults occur in the two photovoltaic circuits 200 are different, the fundamental wave frequencies obtained by bandpass filtering and discrete Fourier transform processing of the original AC signals of the two photovoltaic circuits 200 will be inconsistent or the fundamental wave amplitudes will differ greatly. Therefore, if the fundamental wave frequencies of the two photovoltaic circuits 200 that have arcing faults are consistent and the difference between the two fundamental wave amplitudes is less than the second preset threshold, it can be determined that the two photovoltaic circuits 200 have a parallel arcing fault, and it can be determined that a parallel arcing fault has occurred in the photovoltaic system.

[0086] In the fault detection method provided in some embodiments of the present invention, when the voltage difference between the DC cable 220 and the inverter 100 before and after the arc fault occurs is greater than a third preset threshold, it is determined that a grounding arc fault occurs in the DC cable 220 .

[0087] After the DC cable 220 has a grounding arc fault, the DC power transmitted from the photovoltaic assembly 210 to the inverter 100 through the DC cable 220 will be transmitted to the ground at the fault location, so that the voltage transmitted from the DC cable 220 to the inverter 100 will drop significantly. Therefore, when the voltage difference between the DC cable 220 and the inverter 100 before and after the arc fault occurs is greater than the third preset threshold, it can be determined that the arc fault of the DC cable 220 is a grounding arc fault.

[0088] In the fault detection method provided by some embodiments of the present invention, when the arc fault that occurs does not belong to a parallel arc fault and a ground arc fault, it is determined that a series arc fault occurs in the DC cable 220 .

[0089] It is understandable that the types of arc faults occurring based on the DC cable 220 generally include parallel arc faults, ground arc faults and series arc faults. There are no other obvious judgment conditions for series arc faults. Therefore, it is most accurate and reliable to determine whether a series arc fault occurs by the elimination method.

[0090] In order to more clearly explain the photovoltaic system fault detection method of the present invention, Figure 1 , Figure 4 and Figure 7 A detailed embodiment of the present application is introduced in a comprehensive and detailed manner.

[0091] The fault detection method of the photovoltaic system includes the following steps:

[0092] Step S701: the photovoltaic system is powered on, the inverter 100 is powered on, the arc detection sensor 230 starts to work, and the arc detection sensor 230 collects the original AC signal at the connection between the DC cable 220 and the inverter 100; jump to step S702;

[0093] Step S702: the original AC signal collected by the arc detection sensor 230 triggers the first preset threshold set by the arc detection sensor 230; jump to step S703;

[0094] Step S703: Determine whether the trigger is caused by an interference signal. If it is an interference signal, ignore this trigger and jump back to step S702; if not, jump to step S704;

[0095] Step S704: record the AC signals before and after the fault; jump to step S705;

[0096] Step S705: performing bandpass filtering on the AC signal collected by the arc detection sensor 230 to ensure that the frequency of the signal passing through is between 100kHz and 200kHz, and then performing discrete Fourier transform processing to obtain the fundamental amplitude and fundamental frequency of the AC signal; jump to step S706;

[0097] Step S706: the AC signal collected by the arc detection sensor 230 is continuously sampled for a first preset time length t4, and the collected AC signal is continuously subjected to bandpass filtering and discrete Fourier transform processing;

[0098] Step S707: Determine whether the fundamental amplitude of the AC signal within the first preset time t4 has always exceeded the threshold. If yes, jump to step S708; if no, jump back to step S702;

[0099] Step S708: Determine whether an arc fault occurs; jump to step S709;

[0100] Step S709: Calculate the fundamental amplitude and fundamental frequency of the AC signal collected by the arc detection sensor 230 of other photovoltaic circuits 200; jump to step S710;

[0101] Step S710: Determine whether the fundamental frequencies of the AC signals collected by the arc detection sensors 230 of the multiple photovoltaic circuits 200 are consistent? If yes, jump to step S711; if not, jump to step S713;

[0102] Step S711: Determine whether the difference between the fundamental wave amplitudes of the photovoltaic circuits 200 whose fundamental wave amplitudes exceed the threshold is less than a preset value. If yes, jump to step S712; if not, jump back to step S713;

[0103] Step S712: determine whether a parallel arc fault occurs; jump to step S716;

[0104] Step S713: Determine whether the voltage difference between the DC cable 220 and the inverter 100 before and after the arc fault occurs is greater than a preset threshold. If yes, jump to step S715; if not, jump to step S714;

[0105] Step S714: determine that a series arc fault occurs; jump to step S716;

[0106] Step S715: determine whether a grounding arc fault occurs; jump to step S716;

[0107] Step S716: perform wavelet transform processing to obtain fault characteristics; jump to step S717;

[0108] Step S717: Substitute the formula to calculate and obtain the location information of the arc fault; jump to step S718;

[0109] Step S718: Report the fault.

[0110] In this embodiment, the original AC signal collected by the arc detection sensor 230 is band-pass filtered by a band-pass filter to ensure that the passing signal frequency is between 100kHz and 200kHz. The data is digitally processed by a DSP processor and the fundamental amplitude and fundamental frequency of the original AC signal are determined by discrete Fourier transform processing. If the fundamental amplitude is greater than the first preset threshold, it can be preliminarily determined that a DC arc is generated in the photovoltaic circuit 200. Since DC arc is difficult to eliminate by itself without any disconnection equipment, a first preset time length t4 is set, and the DC circuit is continuously judged within the t4 time period. If the fundamental wave amplitude is always greater than the first preset threshold value, it is determined that DC arcing has occurred in the circuit. In addition, when an arcing fault occurs in the DC cable 220 connecting the photovoltaic component 210 and the inverter 100, the arc detection sensor 230 arranged at the connection between the DC cable 220 and the inverter 100 records the signals before and after the arcing fault occurs to obtain a fault recording, which is then processed by wavelet transform. Since a traveling wave signal of a specific frequency is generated and transmitted on the DC cable 220 when an arcing fault occurs, wavelet transform processing is performed on the fault recording to extract the fault characteristics of the traveling wave signal after the arcing fault occurs. Finally, after conversion processing, the positioning information of the arcing fault is obtained, thereby realizing the physical positioning of the arcing fault, which is conducive to timely maintenance and processing.

[0111] Reference Figure 8 The second aspect of the present invention provides an operation control device 800, including a memory 810, a processor 820, and a computer program stored in the memory 810 and executable on the processor 820. The processor 820 executes the program to implement the photovoltaic system fault detection method of the first aspect of the present invention, for example, to execute Figure 2 Steps S210 to S230 of the method, Figure 3 Steps S310 to S320 of the method, Figure 5 Steps S510 to S520 of the method and Figure 6 Method steps S610 to S620.

[0112] In a third aspect, an embodiment of the present invention provides a photovoltaic system, comprising an operation control device 800 according to the embodiment of the second aspect above.

[0113] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the photovoltaic system fault detection method of the first aspect embodiment above, for example, to execute Figure 2 Steps S210 to S230 of the method, Figure 3 Steps S310 to S320 of the method, Figure 5 Steps S510 to S520 of the method and Figure 6 Method steps S610 to S620.

[0114] It will be appreciated by those skilled in the art that all or some of the steps and systems in the disclosed methods above may be implemented as software, firmware, hardware and appropriate combinations thereof. Some physical components or all physical components may be implemented as software executed by a processor, such as a central processing unit, a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium or a non-transitory medium and a communication medium or a temporary medium. As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technologies, CD-ROM, digital versatile disk DVD or other optical disk storage, magnetic cassettes, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that may be used to store desired information and may be accessed by a computer. Furthermore, it is well known to those skilled in the art that communication media typically embodies computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

[0115] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A photovoltaic system fault detection method, characterized in that: The photovoltaic system includes an inverter and a plurality of photovoltaic circuits, wherein the photovoltaic circuit includes a photovoltaic assembly, a DC cable connecting the photovoltaic assembly and the inverter, and an arc detection sensor arranged at a connection between the DC cable and the inverter, and the method includes: When an arcing fault occurs in the DC cable, a fault recording of the arc detection sensor is obtained, wherein the fault recording includes a normal AC signal before the arcing fault occurs and a traveling wave signal after the arcing fault occurs; Performing wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal; The conversion process is performed according to the fault characteristics to obtain the location information of the arcing fault.

2. The fault detection method according to claim 1, characterized in that: The performing wavelet transform processing on the fault recording to obtain the fault characteristics of the traveling wave signal includes: Select wavelet basis function; Decomposing the transformation formula of continuous wavelet transform of the wavelet basis function combined with the fault recording to obtain the first duration and the second duration of the traveling wave signal; Among them, the first time length is the time length for the traveling wave signal to be transmitted directly from the fault location to the arc detection sensor; the second time length is the time length for the traveling wave signal to be transmitted from the fault location to the photovoltaic component and then reflected to the arc detection sensor.

3. The fault detection method according to claim 2, characterized in that: The conversion process is performed according to the fault characteristics to obtain the location information of the arcing fault, including: Multiplying the difference between the second time length and the first time length by the transmission speed of the traveling wave signal in the DC cable and dividing the result by 2 to obtain a first distance between the fault location and the photovoltaic component; The first distance is subtracted from the length of the DC cable to obtain a second distance between the fault location and the inverter.

4. The fault detection method according to claim 2, characterized in that: The wavelet basis function is: Where: a is the scale coefficient, a≠0, and b is the time position parameter.

5. The fault detection method according to claim 4, characterized in that: The transformation formula of the continuous wavelet transform is: Wherein, f(t) is the signal of the fault recording with R=(-∞, +∞), R represents the value range; ω f(a,b) is the wavelet signal of f(t); ψ(t) is the basic wavelet, ψ * (a,b) is the conjugate of ψ(a,b); a∈R, b∈R.

6. The fault detection method according to claim 1, characterized in that: Also includes: Acquire the original AC signal collected by the arc detection sensor, and perform bandpass filtering and discrete Fourier transform processing to obtain the fundamental amplitude of the original AC signal; When the fundamental wave amplitudes within the first preset time period are all greater than a first preset threshold, it is determined that an arc fault occurs in the DC cable.

7. The fault detection method according to claim 6, characterized in that: The photovoltaic circuit is provided with multiple ones. When the fundamental frequencies of the original AC signals of two photovoltaic circuits are consistent, the fundamental amplitudes are both greater than the first preset threshold, and the difference between the two fundamental amplitudes is less than the second preset threshold, it is determined that a parallel arc fault occurs in the photovoltaic system.

8. The fault detection method according to claim 6 or 7, characterized in that: When the voltage difference between the DC cable and the inverter before and after the arc fault occurs is greater than a third preset threshold, it is determined that a grounding arc fault occurs in the DC cable.

9. The fault detection method according to claim 8, characterized in that: When the arc fault does not belong to a parallel arc fault and a ground arc fault, it is determined that a series arc fault occurs in the DC cable.

10. An operation control device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the photovoltaic system fault detection method according to any one of claims 1 to 9.

11. A photovoltaic system, characterized in that: Includes the operation control device as claimed in claim 10.

12. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the photovoltaic system fault detection method according to any one of claims 1 to 9.

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