CN111726079B - Active photovoltaic string arc fault detection method and system - Google Patents
Active photovoltaic string arc fault detection method and system Download PDFInfo
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Abstract
The invention provides an active photovoltaic string arc fault detection method and system, which comprises the following steps: active signal injection: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic group; current signal acquisition: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group; an arc fault judgment step: according to current signal information on a direct current bus at the string side of the photovoltaic group, wavelet transformation processing is carried out, signal characteristics after wavelet transformation processing are analyzed, the signal characteristics after wavelet transformation processing are compared with input high-frequency signals, whether an arc fault occurs in the photovoltaic group string or not is judged, and active photovoltaic group string arc fault detection result information is obtained. The invention carries out detection on the serial side of the photovoltaic group, thereby fundamentally solving the influence of noise and different operation working conditions of the inverter on the detection.
Description
Technical Field
The invention relates to the technical field of arc fault detection, in particular to an active photovoltaic string arc fault detection method and system.
Background
In recent years, with the improvement of the environmental protection requirement of China and the progress of renewable energy power generation technology, the utilization scale of clean energy is enlarged and the development is rapid. For example, as of 2019, the cumulative installed capacity of photovoltaic power generation in China has reached 204GW, and is the first in the world. However, due to the arc fault of the photovoltaic string, the fire accidents of the photovoltaic power station occur frequently, so that huge economic loss is caused, and the personal safety hidden danger is serious, which is concerned by the industry. At present, there are two main types of arc fault detection techniques for photovoltaic strings: the method is based on a detection method of the change of the relevant physical properties such as sound, light, heat and the like in the arc development process; and the other is a time-frequency detection method based on electric arc signals.
However, many problems still exist with these techniques. The former method, i.e. the detection method based on the change of physical properties such as sound, light, heat, etc., has the disadvantages that the adopted sensors are generally higher in cost, meanwhile, the sensors are easily influenced by the factors such as sound, light, heat, etc. in the environment, and whether the misjudgment is caused by the arc fault of the photovoltaic string is not easy to distinguish. The latter method is based on detecting the time-frequency signal of the electric arc signal, the method is stable, whether the electric arc occurs can be directly judged from the electric signal, however, the method depends on a single time domain or frequency domain criterion, the detection rate is low, the misjudgment rate is high, and the mixed time-frequency criterion is not mature. Meanwhile, the arc signal characteristics are inevitably affected by external conditions, such as inverter noise, different working conditions, and the like, so that misjudgment is caused.
Patent document CN107181460A discloses an algorithm for 4-layer transformation using db6 wavelet to reduce the interference of inverter switching frequency, thereby reducing the false rate; patent document CN104601105A discloses a method for detecting a fault arc of a photovoltaic system under abnormal lighting conditions; research on direct-current arc fault characteristics and detection methods of photovoltaic systems (muglong, wang yijian, jiang, etc., the Chinese Motor engineering journal 2016, 36 (19): 5236-; in the text of direct-current series fault arc characteristic and identification technology research of a photovoltaic system (university of Lianning engineering technology, Zazejie, 2017), time domain and frequency domain analysis are combined to research the problem of series fault arc of the photovoltaic system, and based on characteristic differences of current peak values and current average values when the photovoltaic system normally operates and series fault arc occurs, feasibility of current time domain characteristics in the aspect of series fault arc identification is analyzed, and the conclusion is that standard differences of low-frequency coefficients and standard differences of high-frequency coefficients of current three-layer wavelet decomposition are higher than normal states when series fault arc occurs in the photovoltaic system. These inventions are concerned with enhancing the adaptability to certain external conditions, such as overcoming the influence of inverter noise and the like on the detection result. However, the method cannot adapt to the situation of the combined action of a plurality of environmental factors, and cannot ensure high reliability when a plurality of influencing factors are changed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an active photovoltaic string arc fault detection method and system.
The invention provides an active photovoltaic string arc fault detection method, which comprises the following steps: active signal injection: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic module in a coil coupling mode; current signal acquisition: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group; an arc fault judgment step: according to current signal information on a direct current bus at the string side of the photovoltaic group, wavelet transformation processing is carried out, signal characteristics after wavelet transformation processing are analyzed, the signal characteristics after wavelet transformation processing are compared with input high-frequency signals, whether an arc fault occurs in the photovoltaic group string or not is judged, and active photovoltaic group string arc fault detection result information is obtained.
Preferably, the active injection signal step: a first frequency band setting step: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V; the signal generator generates a high-frequency signal which adopts a sine wave.
Preferably, the active injection signal step: a second frequency band setting step: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V; the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
Preferably, the current signal acquisition step: current signal measurement: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit; wherein the sampling frequency is greater than or equal to 200 kHz.
Preferably, the arc fault determining step includes: judging whether the photovoltaic string has an arc fault; if yes, acquiring arc fault occurrence information; if not, acquiring the information that the arc fault does not occur; and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
According to the invention, the active photovoltaic string arc fault detection system comprises: an active injection signal module: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic module in a coil coupling mode; the current signal acquisition module: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group; an arc fault judgment module: according to current signal information on a direct current bus at the string side of the photovoltaic group, wavelet transformation processing is carried out, signal characteristics after wavelet transformation processing are analyzed, the signal characteristics after wavelet transformation processing are compared with input high-frequency signals, whether an arc fault occurs in the photovoltaic group string or not is judged, and active photovoltaic group string arc fault detection result information is obtained.
Preferably, the active injection signal module: the first frequency band setting module: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V; the signal generator generates a high-frequency signal which adopts a sine wave.
Preferably, the active injection signal module: the second frequency band setting module: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V; the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
Preferably, the current signal acquisition module: the current signal measurement module: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit; wherein the sampling frequency is greater than or equal to 200 kHz.
Preferably, the arc fault determination module includes: judging whether the photovoltaic string has an arc fault; if yes, acquiring arc fault occurrence information; if not, acquiring the information that the arc fault does not occur; and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts an active detection mode, is sensitive to the characteristic change of a circuit loop, and has stronger anti-interference performance and more accuracy compared with a passive mode;
2. according to the invention, a comparison and judgment mode is adopted when a fault is judged, so that the misjudgment rate of the detection device can be effectively reduced;
3. the invention carries out detection on the serial side of the photovoltaic group, thereby fundamentally solving the influence of noise and different operation working conditions of the inverter on the detection.
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Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic diagram of an active photovoltaic string arc fault detection process according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an active photovoltaic string arc fault detection system according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
As shown in fig. 1-2, the method for detecting an arc fault of an active photovoltaic string according to the present invention includes: active signal injection: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic module in a coil coupling mode; current signal acquisition: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group; an arc fault judgment step: according to current signal information on a direct current bus at the string side of the photovoltaic group, wavelet transformation processing is carried out, signal characteristics after wavelet transformation processing are analyzed, the signal characteristics after wavelet transformation processing are compared with input high-frequency signals, whether an arc fault occurs in the photovoltaic group string or not is judged, and active photovoltaic group string arc fault detection result information is obtained.
The invention adopts an active detection method and is sensitive to the change of the circuit loop characteristics. Compared with a passive mode, the anti-interference and environmental adaptability are stronger.
The high-frequency signal with certain characteristics is injected, and the high-frequency signal coupled to the string side of the photovoltaic string is a sine wave with the frequency band of 10-100 kHz and the amplitude of 0-2V, so that the high-frequency detection device is suitable for arc detection; in the fault judgment method, a comparison and judgment mode, namely a mode of comparing the characteristic difference of an input signal and an output signal instead of a fixed threshold value is adopted, so that the misjudgment rate of the detection device is effectively reduced; the detection mode is carried out on the serial side of the photovoltaic group, so that the influence of noise of the inverter is effectively inhibited.
Preferably, the active injection signal step: a first frequency band setting step: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V; the signal generator generates a high-frequency signal which adopts a sine wave.
Preferably, the active injection signal step: a second frequency band setting step: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V; the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
Preferably, the current signal acquisition step: current signal measurement: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit; wherein the sampling frequency is greater than or equal to 200 kHz.
Preferably, the arc fault determining step includes: judging whether the photovoltaic string has an arc fault; if yes, acquiring arc fault occurrence information; if not, acquiring the information that the arc fault does not occur; and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
According to the invention, the active photovoltaic string arc fault detection system comprises: an active injection signal module: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic module in a coil coupling mode; the current signal acquisition module: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group; an arc fault judgment module: according to current signal information on a direct current bus at the string side of the photovoltaic group, wavelet transformation processing is carried out, signal characteristics after wavelet transformation processing are analyzed, the signal characteristics after wavelet transformation processing are compared with input high-frequency signals, whether an arc fault occurs in the photovoltaic group string or not is judged, and active photovoltaic group string arc fault detection result information is obtained.
Preferably, the active injection signal module: the first frequency band setting module: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V; the signal generator generates a high-frequency signal which adopts a sine wave.
Preferably, the active injection signal module: the second frequency band setting module: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V; the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
Preferably, the current signal acquisition module: the current signal measurement module: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit; wherein the sampling frequency is greater than or equal to 200 kHz.
Preferably, the arc fault determination module includes: judging whether the photovoltaic string has an arc fault; if yes, acquiring arc fault occurrence information; if not, acquiring the information that the arc fault does not occur; and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
Specifically, in one embodiment, an active photovoltaic string arc fault detection method includes the following steps: active signal injection: generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic module in a coil coupling mode;
current signal acquisition: sampling and measuring current signals on a direct current bus at the serial side of the photovoltaic group and recording the current signals;
an arc fault judgment step: performing wavelet transformation according to the recorded current signal on the direct current bus at the side of the photovoltaic string, analyzing and processing the characteristics of the current signal, comparing the current signal with an input high-frequency signal, and judging whether the photovoltaic string has an arc fault;
the arc fault determining step includes:
the arc fault judging step comprises the following steps:
step S1, initializing the system;
step S2, intercepting the original current data into current signals with 4096 data lengths;
step S3, wavelet transform is carried out on the intercepted original data, and the energy e of each frequency band is analyzed and calculatedi. Performing a normalization process, i.e. Ei＝ei/∑ei。
And step S4, stabilizing the energy distribution of each frequency band when no arc fault exists. Calculating the energy distribution range of each frequency band: according to a preset value KminAnd KmaxAnd calculating the energy distribution range of each frequency band when no arc fault exists. The preset value KminGive the lower bound and KmaxAn upper bound is given.
And S5, comparing the energy with the input high-frequency signal, if the energy of the selected characteristic frequency band deviates from a preset value, judging that an arc fault occurs, and entering S6, wherein the preset value is determined according to the input high-frequency signal. If the energy distribution of the selected characteristic frequency band deviates from the stable value of the last time period, it is determined that an arc fault occurs, and the process proceeds to step S6.
And step S6, sending out a fault signal.
Preferably, the high-frequency signal is a sine wave with a frequency range of 10 kHz-100 kHz and an amplitude of 0-10V; the high-frequency signal coupled to the string side of the photovoltaic group is a sine wave with a frequency range of 10 kHz-100 kHz and an amplitude of 0-2V.
Preferably, the current signal acquisition step comprises current signal measurement, current signal amplification, a/D conversion and record storage. The sampling frequency is at least 200 kHz.
According to the invention, the active photovoltaic string arc fault detection system comprises: initiative injection signal unit, current signal acquisition unit and electric arc fault judge the unit, wherein:
the active injection signal unit is used for actively outputting a high-frequency signal to the photovoltaic string;
the current signal acquisition unit is used for measuring and recording a current signal on a direct current bus at the serial side of the photovoltaic group;
the arc fault judging unit performs wavelet transformation according to the recorded current signal, compares the wavelet transformation with the input high-frequency signal and is used for judging whether the photovoltaic arc fault occurs or not, and if so, sends a fault signal.
Preferably, the active injection signal unit comprises a signal generator, a coupling coil and a single chip microcomputer. The singlechip control signal generator actively outputs and records high-frequency signals at the string side of the photovoltaic module in a coil coupling mode.
Preferably, the frequency band of the high-frequency signal generated by the signal generator is 10 kHz-100 kHz, and the amplitude is 0-10V; the high-frequency signal coupled to the string side of the photovoltaic group is a sine wave with a frequency range of 10 kHz-100 kHz and an amplitude of 0-2V.
Preferably, the arc fault detection unit includes a rogowski coil, a current signal amplification module, an a/D conversion module, and a storage module.
Preferably, the arc fault determination unit includes a processor. The processor processes the collected current signals, judges whether the photovoltaic string has an arc fault or not, and sends a fault signal if the photovoltaic string has the arc fault.
Specifically, in an embodiment, as shown in fig. 1, an active photovoltaic string arc fault detection method provided by the present invention includes:
active signal injection: the active injection signal module actively outputs high-frequency signals at the string side of the photovoltaic module in a coil coupling mode, and records the signals of the injected high-frequency signals. The frequency of the high-frequency signal generated by the signal module is 10 kHz-100 kHz, and the amplitude of the high-frequency signal is 0-10V. The high-frequency signal injected into the photovoltaic group string side is a sine wave with the frequency of 10 kHz-100 kHz and the amplitude of 0V-2V.
Current signal acquisition: the current signal acquisition module acquires current signals on the photovoltaic direct current bus, measures current firstly, and then the current signals are recorded and stored after being amplified by the current signal amplification module and converted by the A/D conversion module.
An arc fault judgment step: and the arc fault judgment module processes the data recorded by the current signal acquisition module, compares the data with the injected high-frequency signal characteristics, judges whether the photovoltaic string has an arc fault or not, and sends a fault signal if the photovoltaic string has the arc fault.
If the photovoltaic string has no arc fault, the high-frequency signal in the measured output current signal is stable and unchanged, and the characteristics of the output current signal are also stable and unchanged. Therefore, the arc-free fault is that the output signal shows stable and unchanged characteristic difference with the input high-frequency signal and the characteristic of the output signal is kept stable.
The arc fault judging step comprises the following steps:
step S1, initializing the system;
step S2, intercepting the original current data into current signals with 4096 data lengths;
step S3, wavelet transform is carried out on the intercepted original data, and the energy e of each frequency band is analyzed and calculatedi. Performing a normalization process, i.e. Ei＝ei/∑ei。
And step S4, stabilizing the energy distribution of each frequency band when no arc fault exists. Calculating the energy distribution range of each frequency band: according to a preset value KminAnd KmaxAnd calculating the energy distribution range of each frequency band when no arc fault exists. The preset value KminGive the lower bound and KmaxAn upper bound is given.
And S5, comparing the energy with the input high-frequency signal, if the energy of the selected characteristic frequency band deviates from a preset value, judging that an arc fault occurs, and entering S6, wherein the preset value is determined according to the input high-frequency signal. If the energy distribution of the selected characteristic frequency band deviates from the stable value of the last time period, it is determined that an arc fault occurs, and the process proceeds to step S6.
And step S6, sending out a fault signal.
As shown in fig. 2, the active photovoltaic string arc fault detection system provided by the present invention includes:
the device comprises an active injection signal unit, a current signal acquisition unit and an arc fault judgment unit. The active injection signal unit is controlled by a singlechip, and a high-frequency signal generated by the signal generator is a sine wave with the frequency of 10 kHz-100 kHz and the amplitude of 0-10V. The high-frequency signal injected to the photovoltaic string side in a coil coupling mode is a sine wave with the frequency of 10 kHz-100 kHz and the amplitude of 0-2V. The single chip microcomputer records the information of the high-frequency signal generated by the signal generator.
The current signal acquisition unit comprises a Rogowski coil, a current signal amplification module, an A/D conversion module and a storage module. The Rogowski coil measures a current signal on a direct current bus at the string side of the photovoltaic group, the current signal is amplified to an input requirement of the A/D conversion module through the current signal amplification module, and the input requirement is recorded and stored after being processed by the A/D conversion module.
The arc fault judgment unit comprises a processor, wherein the processor carries out wavelet transformation processing on the measured current signal according to the active photovoltaic group string arc fault detection method provided by the invention, analyzes the characteristics of the current signal, compares the characteristics with the characteristics of an input signal, judges whether an arc fault occurs or not, and sends a fault signal if the arc fault occurs.
The invention adopts an active detection mode, is sensitive to the characteristic change of a circuit loop, and has stronger anti-interference performance and more accuracy compared with a passive mode; according to the invention, a comparison and judgment mode is adopted when a fault is judged, so that the misjudgment rate of the detection device can be effectively reduced; the invention carries out detection on the serial side of the photovoltaic group, thereby fundamentally solving the influence of noise and different operation working conditions of the inverter on the detection.
In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (6)
1. An active photovoltaic string arc fault detection method is characterized by comprising the following steps:
active signal injection: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic group;
current signal acquisition: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group;
an arc fault judgment step: performing wavelet transformation processing according to current signal information on a direct current bus at the string side of the photovoltaic group, analyzing signal characteristics after the wavelet transformation processing, comparing the signal characteristics after the wavelet transformation processing with an input high-frequency signal, judging whether the photovoltaic group string has an arc fault, and acquiring active photovoltaic group string arc fault detection result information;
the active signal injection step:
a first frequency band setting step: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V;
the signal generator generates a high-frequency signal and adopts a sine wave;
the active signal injection step:
a second frequency band setting step: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V;
the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
2. The active photovoltaic string arc fault detection method of claim 1, wherein the current signal acquisition step comprises:
current signal measurement: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit;
wherein the sampling frequency is greater than or equal to 200 kHz.
3. The active photovoltaic string arc fault detection method of claim 1, wherein the arc fault determination step comprises:
judging whether the photovoltaic string has an arc fault;
if yes, acquiring arc fault occurrence information;
if not, acquiring the information that the arc fault does not occur;
and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
4. An active photovoltaic string arc fault detection system, comprising:
an active injection signal module: actively generating a high-frequency signal, and actively outputting the high-frequency signal at the string side of the photovoltaic group;
the current signal acquisition module: measuring and recording current signals on the direct current bus at the string side of the photovoltaic group to obtain current signal information on the direct current bus at the string side of the photovoltaic group;
an arc fault judgment module: performing wavelet transformation processing according to current signal information on a direct current bus at the string side of the photovoltaic group, analyzing signal characteristics after the wavelet transformation processing, comparing the signal characteristics after the wavelet transformation processing with an input high-frequency signal, judging whether the photovoltaic group string has an arc fault, and acquiring active photovoltaic group string arc fault detection result information;
the active injection signal module:
the first frequency band setting module: generating a high-frequency signal by a signal generator, and setting the frequency band of the signal to be 10-100 kHz and the amplitude to be 0-10V;
the signal generator generates a high-frequency signal and adopts a sine wave;
the active injection signal module:
the second frequency band setting module: coupling a coil to a high-frequency signal at the string side of the photovoltaic group, so that the frequency band of the high-frequency signal at the string side of the photovoltaic group coupled by the coil is 10 kHz-100 kHz, and the amplitude is 0-2V;
the high-frequency signal of the coil coupled to the photovoltaic group string side adopts a sine wave.
5. The active photovoltaic string arc fault detection system of claim 4, wherein the current signal collection module:
the current signal measurement module: measuring a current signal on a direct current bus at the string side of the photovoltaic group, recording the sampling frequency, and recording and storing the current signal after the current signal is processed by a current signal amplifying unit and an A/D conversion unit;
wherein the sampling frequency is greater than or equal to 200 kHz.
6. The active photovoltaic string arc fault detection system of claim 4, wherein the arc fault determination module comprises:
judging whether the photovoltaic string has an arc fault;
if yes, acquiring arc fault occurrence information;
if not, acquiring the information that the arc fault does not occur;
and acquiring the information of the detection result of the arc faults of the active photovoltaic string according to the information of the occurrence of the arc faults and the information of the non-occurrence of the arc faults.
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