Fault detection device and method and photovoltaic power generation system

Abstract

The invention discloses a fault detection device and method and a photovoltaic power generation system, and belongs to the technical field of electric power. The fault detection device comprises a sampling module used for sampling an output signal of an output cable of a solar cell panel to obtain a sampling signal; the output signal comprises a current bottom noise ripple signal and a fault ripple signal; the signal processing module is used for carrying out wave trapping and conditioning processing on the sampling signals, filtering out signals of a target frequency band in the sampling signals and amplifying signals of other frequency bands to obtain characteristic signals; the target frequency band is a frequency band where the characteristic noise signal coincides with a noise signal generated by the target fault; and the control module is used for detecting whether a fault exists based on the characteristic signal, the background noise model and the fault signal model. According to the fault detection device and method and the photovoltaic power generation system disclosed by the invention, the sampling notch and conditioning processing are combined, the switching frequency noise, the frequency multiplication noise, the current total harmonic distortion noise and the like are suppressed, and the detection accuracy can be improved.

Description

Technical Field

[0001] The present application belongs to the field of electric power technology, and in particular, relates to a fault detection device, method and photovoltaic power generation system. Background Art

[0002] Photovoltaic power generation system is a power generation system that uses solar panels to directly convert solar energy into electrical energy. In the process of power generation in photovoltaic power generation system, there is a risk of DC arcing. Usually, an arc detection device (Arcfault circuit interrupter, AFCI) can be used to detect the DC arcing phenomenon in photovoltaic power system, thereby eliminating the risk of DC arcing. To use AFCI to detect DC arcing, it is necessary to accurately capture the current background noise signal generated during the arcing process.

[0003] However, in the actual process of detecting the fault arc, the switching frequency of the DC bus and its frequency multiple fluctuations will affect the stability of the overall control of the AFCI and the total harmonic distortion (THD) of the current, and may even cause the oscillation of the solar panel current, resulting in false alarms or missed alarms of the fault arc detection.

[0004] In order to suppress the influence of the switching frequency and its frequency multiple fluctuations of the DC bus on the fault arc detection results, the method of reducing the overall gain is usually adopted, but this will reduce the AFCI's ability to recognize the real arc characteristic signal. Therefore, the existing method still has the disadvantage of limited accuracy in fault arc detection. Summary of the invention

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes a fault detection device, method and photovoltaic power generation system, which can improve the accuracy of fault detection.

[0006] In a first aspect, the present application provides a fault detection device, the device comprising:

[0007] A sampling module, used for sampling the output signal of the output cable of the solar panel to obtain a sampling signal; the output signal includes a current noise ripple signal and a fault ripple signal;

[0008] A signal processing module, used to perform notch and conditioning processing on the sampled signal, filter out the signal of the target frequency band in the sampled signal and amplify the signals of other frequency bands to obtain a characteristic signal; the target frequency band is a frequency band where the characteristic noise signal overlaps with the noise signal generated by the target fault;

[0009] The control module is used to detect whether a fault exists based on the characteristic signal, a pre-established background noise model and a fault signal model.

[0010] According to the fault detection device of the present application, the signal processing module is combined with sampling notch processing and conditioning processing to filter out the signal of the target frequency band in the sampling signal and amplify the signals of other frequency bands. It can suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, and reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, so that the overall gain of the fault detection device is improved, the overall recognition capability of fault detection is enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0011] According to an embodiment of the present application, the fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

[0012] According to one embodiment of the present application, the signal processing module includes:

[0013] A notch unit, used for filtering out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain a first-level signal;

[0014] A conditioning unit, used for amplifying the first-level signal to obtain a second-level signal;

[0015] A filtering unit is used to filter the second-level signal to obtain the characteristic signal.

[0016] According to one embodiment of the present application, the trap unit includes at least one trap circuit.

[0017] According to one embodiment of the present application, the trap circuit is a Bainter trap, a passive T-type trap circuit, a type II trap circuit or an RLC trap.

[0018] According to one embodiment of the present application, the trap circuit includes a high-pass filter.

[0019] According to an embodiment of the present application, the notch unit includes: a first operational amplifier.

[0020] According to an embodiment of the present application, the conditioning unit includes: a second operational amplifier.

[0021] According to one embodiment of the present application, the control module includes:

[0022] A matching unit, used for matching the characteristics of the characteristic signal with the background noise model and the fault signal model respectively;

[0023] A control unit is used to determine that the target fault occurs, control the inverter to stop working and / or control the switch module connecting the solar cell panel and the inverter to turn off when the characteristic of the characteristic signal does not match the background noise model but matches the fault signal model.

[0024] In a second aspect, the present application provides a fault detection method, the method comprising:

[0025] Sampling the output signal of the output cable of the solar panel to obtain a sampling signal; the output signal includes a current background noise ripple signal and a fault ripple signal;

[0026] Perform notch and conditioning processing on the sampled signal, filter out the signal of the target frequency band in the sampled signal and amplify the signals of other frequency bands to obtain a characteristic signal; the target frequency band is a frequency band where the characteristic noise signal overlaps with the noise signal generated by the target fault;

[0027] Based on the characteristic signal, a pre-established background noise model and a fault signal model, it is detected whether a fault exists.

[0028] According to the fault detection method of the present application, by combining sampling notch processing and conditioning processing, the signal of the target frequency band in the sampling signal is filtered out and the signals of other frequency bands are amplified, which can suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, and reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, so that the overall gain of the fault detection device is improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0029] According to an embodiment of the present application, the fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

[0030] According to an embodiment of the present application, performing notch and conditioning processing on the sampled signal, filtering out signals of a target frequency band in the sampled signal and amplifying signals of other frequency bands, and obtaining a characteristic signal includes:

[0031] Filtering out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain a first-level signal;

[0032] amplifying the first-level signal to obtain a second-level signal;

[0033] The second-level signal is conditioned to obtain the characteristic signal.

[0034] According to an embodiment of the present application, the detecting whether there is a fault arc based on the characteristic signal, a pre-established background noise model and a fault signal model includes:

[0035] In a case where the feature of the feature signal does not match the background noise model but matches the fault signal model, it is determined that a target fault occurs.

[0036] According to an embodiment of the present application, after determining that a target fault occurs, the method further includes:

[0037] The inverter is controlled to stop working and / or the switch module used for connecting the solar panel and the inverter is controlled to be turned off.

[0038] In a third aspect, the present application provides a photovoltaic power generation system, comprising: a solar panel, an inverter, and a fault detection device as described in the first aspect.

[0039] According to the photovoltaic power generation system of the present application, by combining sampling notch processing and conditioning processing, the signals of the target frequency band in the sampling signal are filtered out and the signals of other frequency bands are amplified, so as to suppress characteristic noises such as switching frequency noise and its frequency multiple noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its frequency multiple noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall recognition capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0040] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 is a structural schematic diagram of a fault detection device provided in an embodiment of the present application;

[0043] Figure 2 is a schematic diagram of the working process of the fault detection device provided in an embodiment of the present application;

[0044] Figure 3 is a control timing diagram of a fault detection device provided in an embodiment of the present application;

[0045] Figure 4 is a schematic diagram of the relationship between the sampling signal strength and the cable length provided in an embodiment of the present application;

[0046] Figure 5 is a schematic diagram comparing the FFT decomposition relationship of the sampling signal before and after the notch provided in the embodiment of the present application;

[0047] Figure 6is a schematic diagram comparing the sampling signal strength before and after the notch provided in an embodiment of the present application;

[0048] Figure 7 is a schematic diagram of the structure of a signal processing module provided in an embodiment of the present application;

[0049] Figure 8 It is one of the structural schematic diagrams of the trap circuit provided in the embodiment of the present application;

[0050] Fig. 9 This is the second structural schematic diagram of the trap circuit provided in the embodiment of the present application;

[0051] Fig.10 It is a flowchart of the fault detection method provided in the embodiment of the present application. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0053] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0054] In the related art, the energy of the switching frequency and its multiple frequency fluctuations or the current total harmonic distortion noise is much greater than the internal noise floor of the inverter. In order to ensure that the overall current noise floor signal does not exceed the range of the internal detection chip of the fault detection device, since the current noise floor signal also contains the switching frequency noise and its multiple frequency noise or the current total harmonic distortion noise and other internal characteristic noises, the overall gain can only be reduced. However, reducing the overall gain will reduce the fault detection device's ability to identify the real arc characteristic signal.

[0055] Therefore, DC busbars often use a large number of electrolytic capacitors, film capacitors, and inductors to ensure that ripple components are suppressed and the quality of current is improved. However, the above electrolytic capacitors, film capacitors, and inductors are not only large in size and high in cost, but also have their own defects. Electrolytic capacitors may experience problems such as electrolyte volatilization, increased internal resistance, and a lower lifespan than other components. When the current is large, the inductance of the inductor decreases, and the filtering effect is greatly reduced. Film capacitors are large in size and small in inductance.

[0056] In summary, the fault detection of photovoltaic power generation systems in related technologies is easily affected by the aforementioned characteristic noise, and the effect of extracting the target frequency band part of the noise signal generated by the target fault is poor, resulting in low accuracy of fault detection of photovoltaic power generation systems.

[0057] The fault detection device, method and photovoltaic power generation system provided in the embodiments of the present application are described in detail below with reference to the accompanying drawings through specific embodiments and their application scenarios.

[0058] like Figure 1 As shown, the fault detection device 100 includes: a sampling module 110 , a signal processing module 120 and a control module 130 .

[0059] In actual implementation, the fault detection device 100 may mainly include the following components: a sampling module 110 , a signal processing module 120 and a control module 130 .

[0060] The general detection process of the fault detection device 100 includes: the sampling module 110 continuously collects and samples the output signal of the output cable of the solar panel, and then conditions it through the signal processing module 120 and finally sends it to the control module 130.

[0061] The sampling module 110 is used to sample the output signal of the output cable of the solar panel to obtain a sampling signal; the output signal includes a current noise ripple signal and a fault ripple signal.

[0062] It should be noted that the output signal of the output cable of the solar panel can be a current ripple signal. When no fault occurs, the output signal of the output cable of the solar panel is a current noise floor ripple signal. The noise floor is the background noise, which refers to the internal noise of the inverter when there is no fault in the photovoltaic power generation system (generally the solar panel). The above-mentioned "machine" refers to the inverter. The noise floor can include internal switching frequency noise, power frequency noise, and external conducted radiation noise.

[0063] In the event of a solar panel failure (such as arcing, etc.), the output current of the output cable of the solar panel will fluctuate violently. By sampling the current ripple signal output by the output cable of the solar panel, it is possible to monitor whether the current of an inverter is stable and normal, thereby determining whether the photovoltaic power generation system has failed. Therefore, in the event that the solar panel has not failed, the current ripple signal it outputs is a current noise ripple signal; in the event that the solar panel has failed, the current ripple signal it outputs includes not only the above-mentioned current noise ripple signal, but also a current ripple signal generated by the fault. The current ripple signal generated by the fault can be called a fault ripple signal.

[0064] Since arc fault is a common fault of solar panels, the following embodiments are described by taking arc fault as an example of target fault, but those skilled in the art can understand that the target fault includes other types of faults.

[0065] In actual implementation, the sampling module 110 may include a collection unit and a sampling unit.

[0066] The collection unit can be used to collect the current ripple signal output by the solar panel through its output cable. It is understandable that when the solar panel does not fail, the fault ripple signal in the output signal of the output cable of the solar panel can be regarded as zero. In some embodiments, the collection unit may include a current transformer or a current sensor. The output cable of the solar panel is a PV cable between the solar panel and the inverter.

[0067] The sampling unit may be used to sample the signal collected by the collection unit. The signal obtained by sampling the signal collected by the collection unit may be referred to as a sampling signal. In some embodiments, the sampling unit may include a sampling resistor.

[0068] The signal processing module 120 is used to perform notch and conditioning processing on the sampled signal, filter out the signal of the target frequency band in the sampled signal and amplify the signals of other frequency bands to obtain the characteristic signal; the target frequency band is the frequency band where the characteristic noise signal overlaps with the noise signal generated by the target fault.

[0069] In actual implementation, the sampling signal obtained by the sampling module 110 can be input into the signal processing module 120, and the signal processing module 120 performs notching and conditioning processing to obtain a characteristic signal. The role of the signal processing module 120 in performing notching and conditioning processing on the sampling signal is to retain the original fault ripple signal, suppress the interference of the characteristic noise signal in the internal noise signal of the inverter on the fault detection, and fully amplify the fault ripple signal.

[0070] It should be noted that the characteristic noise signal may include the switching frequency noise and its multiple frequency fluctuation noise in the internal noise signal of the inverter, as well as the current total harmonic distortion noise, etc. In general, the frequency band of the above characteristic noise signal overlaps a lot with the frequency band of the noise signal generated by the target fault. The frequency band where the above two types of noise signals overlap is the target frequency band. That is, in the target frequency band, there are both characteristic noise signals and noise signals generated by the target fault; in other frequency bands except the target frequency band, there is basically no characteristic noise signal, but there is a noise signal generated by the target fault.

[0071] The specific structure of the signal processing module 120 is not limited in the embodiment of the present application, and any circuit structure that can achieve the aforementioned functions of retaining the original fault ripple signal, suppressing the interference of the characteristic noise signal in the internal noise signal of the inverter on the fault detection, and fully amplifying the fault ripple signal is adopted. In some embodiments, the signal processing module 120 may include multiple filters.

[0072] The control module 130 is used to detect whether a fault exists based on the characteristic signal, a pre-established background noise model and a fault signal model.

[0073] In actual execution, the characteristic signal obtained by the signal processing module 120 may be input into the control module 130 , and the control module 130 determines whether a fault exists based on the characteristic signal.

[0074] In some embodiments, the control module 130 may include any type of control chip, such as a single chip microcomputer or an MCU.

[0075] In some embodiments, the control module 130 may compare the characteristic signal with a pre-established background noise model and a fault signal model to determine whether the characteristic signal conforms to the characteristics of the background noise signal or the characteristics of the noise signal generated by the target fault, thereby determining whether the target fault exists.

[0076] It can be understood that when the characteristic signal meets the characteristics of the background noise signal but does not meet the characteristics of the noise signal generated by the target fault, it can be determined that the target fault does not exist or has not occurred; and when the characteristic signal does not meet the characteristics of the background noise signal but meets the characteristics of the noise signal generated by the target fault, it can be determined that the target fault exists or has occurred.

[0077] In some embodiments, the background noise model may include background noise data under all working conditions obtained based on notch filter sampling within the target frequency band.

[0078] In some embodiments, the fault signal model may include fault ripple signal data collected at at least one length of an output cable of a solar cell within a target frequency band.

[0079] It should be noted that in actual application scenarios, the length of the output cable of the solar cell can be of various types and is uncontrollable. By pre-collecting fault ripple signal data at different lengths of the output cable of the solar cell, the richness of the fault signal model data can be expanded to cope with detection under various conditions and cover various real scenarios.

[0080] In some embodiments, Figure 2 As shown, the working process of the fault detection device 100 may include the following steps:

[0081] Step 210: Collect current data.

[0082] The current ripple signal output by the solar panel through its output cable can be collected by a current transformer or a current sensor.

[0083] Step 220: sampling with a sampling resistor.

[0084] The output signal of the output cable of the solar panel collected by the current transformer or the current sensor can be sampled through the sampling resistor to obtain a sampling signal.

[0085] Step 230: notching and filtering.

[0086] The signal processing module 120 performs notch and filtering processing on the sampled signal to obtain a characteristic signal.

[0087] Step 240: Determine whether the AD port is saturated.

[0088] Determine whether the AD port of the control module 130 is saturated. If the AD port is saturated, the fault detection function of the control module 130 is invalid; if the AD port is not saturated, the fault detection function of the control module 130 is valid and it can be determined whether there is a fault. The AD port is the sampling port of the control module 130.

[0089] Step 250: Fault handling.

[0090] When the AD port of the control module 130 is not saturated, the control module 130 can perform fault processing based on the characteristic signal. The control module 130 can perform fault processing by first determining whether a fault exists; and eliminating the fault if a fault exists.

[0091] In some embodiments, the fault detection device 100 may be as follows: Figure 3The output signal of the solar panel can be sequentially input into the control module 130 after passing through the current sensor, the sampling resistor, and the signal processing module 120 composed of multiple filters; after the control module 130 obtains the fault detection result based on the input signal, the inverter can be controlled based on the fault detection result.

[0092] It should be noted that if Figure 4 As shown, the longer the output cable of the solar panel is, the weaker the characteristic noise signal is. The weaker the signal is, the more difficult it is to sample and condition it. Therefore, the length of the output cable of the solar panel generally limits the accuracy of the fault detection device.

[0093] In addition, the input voltage range of the sampling port of the control module 130 has an upper limit, which cannot exceed the power supply voltage of the control module 130. Therefore, the total amplification factor of the sampling signal by the signal processing module 120 is limited. Once the upper limit is exceeded, the sampling port will be saturated, and the fault detection function of the control module 130 will fail, and it will be impossible to determine whether there is a fault.

[0094] For example, Figure 5 As shown, in some cases, the characteristic noises in the machine, such as the switching frequency noise and its multiple frequency noise and the current total harmonic distortion noise, are concentrated between 15kHz and 30kHz, resulting in a larger power density of the characteristic noise signal within this frequency range, and a higher voltage amplitude of the characteristic signal processed by the signal processing module 120, which makes it easier to saturate the sampling port of the control module 130.

[0095] In order to enable the fault detection device to work properly and ensure the accuracy of fault detection, it is necessary to ensure that in any case without faults, the characteristic signal processed by the signal processing module 120 will not cause saturation of the sampling port of the control module 130. Once the sampling port of the control module 130 is saturated, it will cause the fault detection device to report a false alarm.

[0096] Therefore, under the same K1 times gain, in the worst working condition, the characteristic noise signal before the notch will cause the sampling port to be saturated between 20kHz and 25kHz, and then the value of K1 can only be reduced to (for example, 0.5*K1, etc.) to ensure that in any fault-free situation, the conditioning of the sampling signal will not cause the sampling port of the control module 130 to be saturated. In this case, in order to make the conditioning result between 20kHz and 25kHz meet the requirements, the sampling conditioning performance of the remaining frequency bands will be sacrificed.

[0097] Under the same K1 times gain, the frequency band with a center frequency of 22.5kHz and a bandwidth of 15kHz (this frequency band is the target frequency band) is notched. The characteristic noise signal after notching will not saturate the sampling port under the K1 times gain, and the performance below 15kHz and above 30kHz is the same as the characteristic noise signal before notching amplified by K1 times, and the performance of these two frequency bands is guaranteed to the maximum. It can be understood that the frequency bands below 15kHz and above 30kHz are the aforementioned other frequency bands.

[0098] It can be seen that by performing notch processing on the target frequency band where characteristic noise signals such as switching frequency noise and its frequency multiple noise and current total harmonic distortion noise are located, the characteristic noise signals will not saturate the sampling port in the frequency domain or time domain at a larger amplification factor.

[0099] In the related art, the sampling signal is amplified as a whole, but due to the limitation of the input voltage of the sampling port of the control module 130 and the large energy of the characteristic noise signal, the overall gain is limited. In the embodiment of the present application, after filtering the signal of the target frequency band, although a part of the noise signal generated by the target fault (i.e., the target frequency band part) is sacrificed, the overall gain of the signal of the other frequency bands can be made larger (compared with the related art), and it is easier to extract the characteristics of the noise signal generated by the target fault.

[0100] In addition, the target frequency band is notched to filter out the signal in the target frequency band, which will not affect the sampling and conditioning of the other frequency bands in the noise signal generated by the target fault.

[0101] Therefore, in the embodiment of the present application, the sampling signal is notched and conditioned by the signal processing module 120, the signal of the target frequency band in the sampling signal is filtered out and the signals of other frequency bands are amplified, so that the above-mentioned other frequency band parts in the noise signal generated by the target fault can obtain a greater gain, thereby improving the sampling accuracy, enriching the model data, and optimizing the overall performance.

[0102] For example, Figure 6 As shown in the figure, under a certain K times gain, the sampling signal before notch processing can cause the sampling port to be saturated under some working conditions. However, under K times gain, the sampling signal after notch processing has a large margin to saturate the sampling port under any working condition.

[0103] It should be noted that Figure 6 The arc fault characteristic signal refers to the fault ripple signal when the target fault is a telephone fault.

[0104] By reasonably designing the signal processing module 120, the switching frequency noise of the switching tube of the inverter and its multiple frequency noise, as well as the characteristic noise such as the total harmonic distortion noise of the current are separated from the target identification frequency band of the fault detection device (which can be the aforementioned other frequency bands), and the energy of the part of the noise signal that is not related to fault detection is reduced, and the overall gain of the part of the signal in the target identification frequency band is maximized to obtain a clearer, more accurate and effective background noise model and fault signal model within the range of a longer cable (referring to the output cable of the solar panel), thereby achieving the effect of improving the overall gain of the fault detection device and enhancing the overall identification ability of the fault detection device.

[0105] In some embodiments, any one of the sampling module 110, the signal processing module 120 and the control module 130, and any one of the functional modules included in the sampling module 110, the signal processing module 120 and the control module 130, can be set inside the inverter housing, or can also be set outside the inverter housing, as long as the inventive concept of the embodiments of the present application is met.

[0106] According to the fault detection device provided in the embodiment of the present application, the signal processing module is combined with sampling notch processing and conditioning processing to filter out the signal of the target frequency band in the sampling signal and amplify the signals of other frequency bands, which can suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, and reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, so that the overall gain of the fault detection device is improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0107] In some embodiments, the fault ripple signal comprises an arc fault ripple signal, and the target fault comprises an arc fault.

[0108] In actual implementation, the fault ripple signal may include an arc fault ripple signal. The arc fault ripple signal refers to a current ripple signal generated by an arc fault. Accordingly, the target fault may include an arc fault. Therefore, the fault detection device 100 can achieve more accurate detection of an arc fault.

[0109] According to the fault detection device provided in the embodiment of the present application, the signal processing module is combined with sampling notch processing and conditioning processing to filter out the signal of the target frequency band in the sampling signal and amplify the signals of other frequency bands, so as to suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on arc fault detection, improve the overall gain of the fault detection device, enhance the overall recognition capability of arc fault detection, reduce false alarms, and improve the accuracy of arc fault detection.

[0110] In some embodiments, Figure 7 As shown, the signal processing module 120 may include:

[0111] The notch unit 710 is used to filter out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain the first-level signal;

[0112] The conditioning unit 720 is used to amplify the first-level signal to obtain a second-level signal;

[0113] The filtering unit 730 is used to filter the second-level signal to obtain a characteristic signal.

[0114] In actual implementation, the original sampling signal to be conditioned (i.e., the sampling signal output by the sampling module 110) can be conditioned to retain the original fault ripple signal after being processed by the notch unit 710, the conditioning unit 720, and the filtering unit 730 in sequence, thereby suppressing the interference of the characteristic noise signal in the internal noise signal of the inverter on fault detection and fully amplifying the fault ripple signal.

[0115] In some embodiments, for the original sampling signal to be conditioned, under certain severe working conditions, the amplitude of the sampling voltage corresponding to the switching frequency of the inverter's BOOST circuit will exceed 2V. The amplitude of the sampling voltage corresponding to the switching frequency of the dominant inverter's BOOST circuit must first be reduced by the notch unit 710, and then the conditioning unit 720 can be used in the second stage to amplify the noise signal generated by the target fault that needs to be extracted and amplified.

[0116] It should be noted that the notch unit 710 filters out the signal of the target frequency band from the sampling signal output by the sampling module 110, which can eliminate most of the energy of the sampling signal, thereby reducing the amplitude of the sampling voltage of the signal.

[0117] The filtering unit 730 can further filter the second-stage signal to further implement the filtering conditioning function and obtain a conditioned sampling signal, that is, a characteristic signal.

[0118] According to the fault detection device provided in the embodiment of the present application, the signal of the target frequency band is filtered out by a notch unit to reduce the amplitude of the sampling voltage of the signal to obtain a first-level signal, and the first-level signal is amplified by a conditioning unit to obtain a second-level signal. The switching frequency noise and its multiple frequency noise or current total harmonic distortion noise and other characteristic noises can be suppressed, and the interference of the switching frequency noise and its multiple frequency noise or current total harmonic distortion noise and other characteristic noises on fault detection can be reduced, so that the overall gain of the fault detection device can be improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0119] In some embodiments, the notch unit 710 includes at least one notch circuit.

[0120] In actual implementation, the notch unit 710 may include one or more notch circuits. Each notch circuit can act as a notch filter.

[0121] In principle, a low-pass filter with a cut-off frequency of f1 and a high-pass filter with a cut-off frequency of f2 are connected in parallel and satisfy the condition f1 < f2, then a band-stop filter can be formed to achieve the effect of a notch filter.

[0122] In some embodiments, the notch unit 710 can separately set a notch circuit, and the notch circuit adopts a structure in which the aforementioned low-pass filter with a cut-off frequency of f1 and a high-pass filter with a cut-off frequency of f2 are connected in parallel (f1 < f2).

[0123] In some embodiments, the notch unit 710 can also set a non-inverting proportional operation circuit after the aforementioned notch circuit, so as to obtain an active band-stop filter circuit

[0124] In some embodiments, the center frequency and bandwidth of each notch circuit can be determined in advance through calculation, so as to reduce the influence of characteristic noises such as switching frequency noise and its harmonic noise and total current harmonic distortion noise on fault detection, and establish a better or even optimal background noise model and fault signal model, etc.

[0125] In some embodiments, in the photovoltaic field, the above-mentioned characteristic noises are mainly determined by the internal switching frequency, including the switching frequency of the BOOST circuit of the inverter, the INV switching frequency, and the auxiliary source switching frequency, etc. Among them, the switching frequency of the BOOST circuit of the inverter has the greatest influence because it has a relatively close loop with the fault detection device. The solar panel is connected to the inverter, and after passing through the sampling module, it is the Boost circuit. The inductance and capacitance in the Boost circuit directly affect whether there will be enough switching frequency noise to affect the sampling result.

[0126] When the switching frequencies such as the switching frequency of the BOOST circuit of the inverter, the INV switching frequency, and the auxiliary source switching frequency are known, the above-mentioned switching frequencies can be used as the center frequencies of each notch circuit, and then the bandwidth can be calculated.

[0127] According to the fault detection device provided in the embodiment of the present application, by adopting at least one notch circuit in the notch unit, the signal of the target frequency band can be filtered out to reduce the amplitude of the sampling voltage of the signal, and the characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise can be suppressed, and the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection can be reduced, so that the overall gain of the fault detection device can be improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0128] In some embodiments, the trap circuit is a Bainter trap, a passive T-type trap circuit, a Type II trap circuit, or an RLC trap.

[0129] In actual implementation, any notch circuit included in the notch unit 710 may be a Bainter notch filter, a passive T-type notch circuit, a II-type notch circuit or an RLC notch filter.

[0130] In some embodiments, Figure 8 The output shows the case where the notch unit 710 uses a Bainter notch filter.

[0131] In some embodiments, any trap circuit included in the trap unit 710 may also be a passive T-type trap circuit, a II-type trap circuit, or an RLC trap.

[0132] Taking the double-T trap circuit as an example, its basic structure consists of a series capacitor and inductor and a parallel capacitor, which can filter out single-frequency interference signals and is suitable for high-frequency loop interference suppression.

[0133] Fig. 9 A typical RC double-T trap circuit is shown, which is composed of a RC passive low-pass filter and a RC passive high-pass filter in parallel.

[0134] The parameter values ​​of each component of the double-T trap circuit can satisfy the following relationship:

[0135] C1=C2=C,C3=2C;

[0136] R1=R2=R, R3=1 / 2R.

[0137] The circuit satisfies the following circuit equation:

[0138]

[0139] Through the above formula, we can get

[0140] It can be seen that the above formula satisfies the characteristics of the second-order system, so we can get

[0141]

[0142] Where ω0 is the center frequency, 2β is the bandwidth, and Q is the quality factor.

[0143] In some embodiments, any of the trap circuits included in the trap unit 710 can also use a parallel bandpass filter or a series bandpass filter. The parallel bandpass filter can filter out signals below and above a certain frequency range at the same time, while the series bandpass filter can weaken noise signals in a specific frequency range. The frequency band is set according to filtering out "characteristic noises such as the switching frequency noise of the switch tube and its multiple frequency noise or the current total harmonic distortion noise", and the inventive concept of the present application can be met.

[0144] In some embodiments, any trap circuit included in the trap unit 710 can be directly set on the main power loop to use inductors and capacitors to cooperate with the downstream power line impedance to establish a trap circuit. Alternatively, it can also be set in the signal processing module 120, and after sampling by the current transformer / sensor unit and the sampling resistor, the trap unit 710, the conditioning unit 720 and the filtering unit 730 on the weak current side complete the preset trap and conditioning filtering goals.

[0145] The signal processing module 120 is configured to have a smaller gain in the frequency band where the switching frequency noise of the switching tube and its frequency multiple noise or the current total harmonic distortion noise are located, and a larger gain in the target identification frequency band, so as to meet the inventive concept of the embodiment of the present application.

[0146] According to the fault detection device provided in the embodiment of the present application, the signal of the target frequency band can be filtered out by using a notch circuit such as a Bainter notch filter, a passive T-type notch circuit, a type II notch circuit or an RLC notch filter, so as to reduce the amplitude of the sampling voltage of the signal, suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall recognition capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0147] In some embodiments, the notch circuit includes a high pass filter.

[0148] In actual implementation, any notch circuit included in the notch unit 710 may include a high-pass filter.

[0149] When the target frequency band has a low frequency (i.e., the target frequency band is lower than the frequency threshold), the notch circuit may include a high-pass filter, so that the signal of the target frequency band may be filtered out by the high-pass filter. The target frequency band with a low frequency may fall below the -3dB point of the high-pass filter, so the notch concept of the present application may be realized by using a high-pass filter, and the same effect may be achieved.

[0150] According to the fault detection device provided in the embodiment of the present application, by using a high-pass filter to filter out the signal in the target frequency band when the frequency in the target frequency band is low, so as to reduce the amplitude of the sampling voltage of the signal, it is possible to suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, and reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, so that the overall gain of the fault detection device is improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0151] In some embodiments, the notch unit 710 includes: a first operational amplifier.

[0152] In actual implementation, the notch unit 710 may further include a first operational amplifier.

[0153] Generally speaking, the input impedance of the passive twin-T network is small, and the output impedance is large. It is easily affected by the previous and next stages of the circuit, and its characteristics are not very good. Its Q value is low, and it can only achieve good attenuation characteristics when it is far away from the resonant frequency ω0.

[0154] In the embodiment of the present application, the trap unit 710 is directly designed at the rear stage of the current transformer / current sensor, which can avoid the influence of coupling with the main power circuit, and the first operational amplifier can also be set to change the voltage division coefficient and significantly change the Q value.

[0155] The output signal of the notch unit 710 is output through a voltage follower with a gain of 1 and fed back to the double-T network to form a bootstrap. Then, the Q value can reach more than 50 when the input signal is attenuated by about 0.3, greatly enhancing the filtering effect.

[0156] According to the fault detection device provided in the embodiment of the present application, the filtering effect of the notch unit can be greatly enhanced by the notch unit including the first operational amplifier.

[0157] In actual implementation, the conditioning unit 720 includes: a second operational amplifier.

[0158] In actual implementation, the conditioning unit 720 may include a second operational amplifier. The filtering unit 730 may include a third operational amplifier.

[0159] The notch unit 710, the conditioning unit 720 and the filter unit 730 are essentially filters, so the conditioning unit 720 and the filter unit 730 after the notch unit 710 can also avoid the influence of coupling with the main power circuit. The conditioning unit 720 or the filter unit 730 can also set an operational amplifier to change the voltage division coefficient and greatly change the Q value.

[0160] The output signal of the conditioning unit 720 or the filtering unit 730 is output through a voltage follower with a gain of 1 and fed back to the double-T network to form a bootstrap. Then, the Q value can reach more than 50 when the input signal is attenuated by about 0.3, greatly enhancing the filtering effect.

[0161] According to the fault detection device provided in the embodiment of the present application, the filtering effect of the notch unit can be greatly enhanced by the conditioning unit including a second operational amplifier.

[0162] In some embodiments, the control module 130 includes:

[0163] A matching unit, used to match the characteristics of the characteristic signal with the background noise model and the fault signal model respectively;

[0164] The control unit is used to determine that a target fault occurs when a feature of the characteristic signal does not match the background noise model but matches the fault signal model, and control the inverter to stop working and / or control the switch module used to connect the solar cell panel and the inverter to turn off.

[0165] In actual implementation, the control module 130 may include a matching unit and a control unit.

[0166] The matching unit can match the characteristics of the characteristic signal with the background noise model and the fault signal model respectively to determine whether the characteristics of the characteristic signal match the background noise model, and whether the characteristics of the characteristic signal match the fault signal model.

[0167] When the characteristic of the characteristic signal does not match the background noise model but matches the fault signal model, the control unit may determine that a target fault occurs, and then the inverter stops working and / or controls the switch module for connecting the solar panel and the inverter to be turned off.

[0168] In some embodiments, when the solar panel outputs an arc fault ripple signal, the fault ripple signal generated by the arc will be collected by the current transformer or current sensor of the fault detection device. After the sampled signal is notched and conditioned, it is determined that it does not match the background noise model but matches the fault signal model. After judgment, it is determined that an arc fault has occurred.

[0169] Once the control unit determines that an arc fault occurs, it can issue an instruction to stop the inverter or disconnect the disconnect switch, thereby achieving the effect of arc extinguishing. The switch module for connecting the solar panel and the inverter may include a disconnect switch.

[0170] According to the fault detection device provided in the embodiment of the present application, the characteristics of the characteristic signal are matched with the background noise model and the fault signal model respectively through the matching unit, and the control unit determines that the target fault occurs when the characteristics of the characteristic signal do not match the background noise model but match the fault signal model, controls the inverter to stop working and / or controls the switch module used to connect the solar panel and the inverter to be turned off, so that the target fault can be handled in time, damage to the inverter and the solar panel can be avoided, and the service life of the inverter and the solar panel can be extended.

[0171] The present application also provides a fault detection method. Fig.10 As shown, the method includes: step 1010, step 1020 and step 1030.

[0172] Step 1010: sampling the output signal of the output cable of the solar panel to obtain a sampled signal; the output signal includes a current background noise ripple signal and a fault ripple signal;

[0173] Step 1020, performing notch and conditioning processing on the sampled signal, filtering out the signal of the target frequency band in the sampled signal and amplifying the signals of other frequency bands to obtain a characteristic signal; the target frequency band is a frequency band where the characteristic noise signal and the noise signal generated by the target fault overlap;

[0174] Step 1030: Detect whether a fault exists based on the characteristic signal, the pre-established background noise model and the fault signal model.

[0175] In actual implementation, the execution subject of the fault detection method may be the fault detection device provided in any of the above embodiments. The process of the fault detection device executing the fault detection method can refer to the above embodiments, which will not be described in detail here.

[0176] According to the fault detection method provided in the embodiment of the present application, by combining sampling notch processing and conditioning processing, the signal of the target frequency band in the sampling signal is filtered out and the signals of other frequency bands are amplified, so that the characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise can be suppressed, and the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection can be reduced, so that the overall gain of the fault detection device can be improved, the overall recognition capability of fault detection can be enhanced, false alarms can be reduced, and the accuracy of fault detection can be improved.

[0177] In some embodiments, the fault ripple signal comprises an arc fault ripple signal, and the target fault comprises an arc fault.

[0178] In some embodiments, notching and conditioning the sampled signal, filtering out the signal of the target frequency band in the sampled signal and amplifying the signals of other frequency bands to obtain the characteristic signal includes:

[0179] Filter out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain the first-level signal;

[0180] Amplifying the first-level signal to obtain a second-level signal;

[0181] The second-level signal is filtered to obtain the characteristic signal.

[0182] In some embodiments, detecting whether there is a fault arc based on a characteristic signal, a pre-established background noise model, and a fault signal model includes:

[0183] When the feature of the feature signal does not match the background noise model but matches the fault signal model, it is determined that the target fault occurs.

[0184] In some embodiments, after determining that a target failure occurs, the method further includes:

[0185] The inverter is controlled to stop working and / or the switch module used for connecting the solar panel and the inverter is controlled to be turned off.

[0186] The present application also provides a photovoltaic power generation system. Figure 1 As shown, the photovoltaic power generation system includes: a solar cell panel 200 , an inverter 300 and a fault detection device 100 .

[0187] In actual implementation, the solar panel 200 may be electrically connected to the input end of the fault detection device 100. The output end of the fault detection device 100 may be electrically connected to the inverter 300. The fault detection device 100 may be the fault detection device provided by any of the above embodiments.

[0188] According to the photovoltaic power generation system provided in the embodiment of the present application, by combining sampling notch processing and conditioning processing, the signal of the target frequency band in the sampling signal is filtered out and the signals of other frequency bands are amplified, so as to suppress characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its multiple frequency noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall recognition capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0189] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0190] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a computer software product, which is stored in a storage medium (such as ROM / RAM, a disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0191] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0192] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0193] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A fault detection device, characterized in that: include: A sampling module, used for sampling the output signal of the output cable of the solar panel to obtain a sampling signal; the output signal includes a current noise ripple signal and a fault ripple signal; A signal processing module, used to perform notch and conditioning processing on the sampled signal, filter out the signal of the target frequency band in the sampled signal and amplify the signals of other frequency bands to obtain a characteristic signal; the target frequency band is a frequency band where the characteristic noise signal overlaps with the noise signal generated by the target fault; The control module is used to detect whether a fault exists based on the characteristic signal, a pre-established background noise model and a fault signal model.

2. The fault detection device according to claim 1, characterized in that: The fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

3. The fault detection device according to claim 1, characterized in that: The signal processing module comprises: A notch unit, used for filtering out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain a first-level signal; A conditioning unit, used for amplifying the first-level signal to obtain a second-level signal; A filtering unit is used to filter the second-level signal to obtain the characteristic signal.

4. The fault detection device according to claim 3, characterized in that: The trap unit includes at least one trap circuit.

5. The fault detection device according to claim 4, characterized in that: The notch circuit is a Bainter notch filter, a passive T-type notch circuit, a II-type notch circuit or an RLC notch filter.

6. The fault detection device according to claim 4, characterized in that: The notch circuit includes a high pass filter.

7. The fault detection device according to any one of claims 3 to 6, characterized in that: The notch unit includes: a first operational amplifier.

8. The fault detection device according to claim 3, characterized in that: The conditioning unit includes: a second operational amplifier.

9. The fault detection device according to claim 1, characterized in that: The control module comprises: A matching unit, used for matching the characteristics of the characteristic signal with the background noise model and the fault signal model respectively; A control unit is used to determine that the target fault occurs, control the inverter to stop working and / or control the switch module connecting the solar cell panel and the inverter to turn off when the characteristic of the characteristic signal does not match the background noise model but matches the fault signal model.

10. A fault detection method, characterized in that: include: Sampling the output signal of the output cable of the solar panel to obtain a sampling signal; the output signal includes a current background noise ripple signal and a fault ripple signal; Perform notch and conditioning processing on the sampled signal, filter out the signal of the target frequency band in the sampled signal and amplify the signals of other frequency bands to obtain a characteristic signal; the target frequency band is a frequency band where the characteristic noise signal overlaps with the noise signal generated by the target fault; Based on the characteristic signal, a pre-established background noise model and a fault signal model, it is detected whether a fault exists.

11. The fault detection method according to claim 10, characterized in that: The fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

12. The fault detection method according to claim 10, characterized in that: The step of performing notch and conditioning processing on the sampled signal, filtering out the signal of the target frequency band in the sampled signal and amplifying the signals of other frequency bands to obtain the characteristic signal includes: Filtering out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain a first-level signal; amplifying the first-level signal to obtain a second-level signal; The second-level signal is conditioned to obtain the characteristic signal.

13. The fault detection method according to any one of claims 10 to 12, characterized in that: The detecting whether there is a fault arc based on the characteristic signal, a pre-established background noise model and a fault signal model comprises: In a case where the feature of the feature signal does not match the background noise model but matches the fault signal model, it is determined that a target fault occurs.

14. The fault detection method according to claim 13, characterized in that: After determining that a target fault occurs, the method further includes: The inverter is controlled to stop working and / or the switch module used for connecting the solar panel and the inverter is controlled to be turned off.

15. A photovoltaic power generation system, characterized in that: include: A solar panel, an inverter and a fault detection device as claimed in any one of claims 1 to 9.

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