Gain adjustment method and AFCI conditioning circuit

Abstract

The present application belongs to the field of photovoltaic systems. Disclosed are a gain adjustment method and an AFCI conditioning circuit. The gain adjustment method comprises: by means of adjusting the gain of an AFCI conditioning circuit, acquiring first output values corresponding to the AFCI conditioning circuit under a plurality of different gains, wherein the first output values are used for representing AFCI conditioning circuit features that correspond to an inverter corresponding to a solar panel under different operating parameters and / or the solar panel and the inverter under different cable lengths; on the basis of each first output value, performing fitting to obtain an amplitude-frequency characteristic curve corresponding to the solar panel; and on the basis of the amplitude-frequency characteristic curve, determining a solar target gain adjustment strategy.

Description

Gain adjustment method and AFCI conditioning circuit

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to Chinese patent applications No. 202511080406X, filed on August 1, 2025; and No. 2024112269582, filed on September 2, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of photovoltaic systems, and more specifically, to a gain adjustment method and an AFCI conditioning circuit. Background Technology

[0004] Currently, in DC arc fault circuit interrupter (AFCI) technology for photovoltaic power generation systems, the cables between solar panels and inverters can sometimes be very long, exceeding the maximum detection range of existing AFCI technologies. Furthermore, as the cable length increases, the line impedance between the arc fault location and the arc fault sensor also increases, weakening the intensity of the arc characteristic signal and increasing the risk of missed arc fault detection. Related technologies enhance the intensity of the arc characteristic signal by amplifying the overall gain of the conditioning circuit to detect DC arc faults over long cables. However, this method cannot address the impact of differences in active and passive components on the initial gain determination, often resulting in a discrepancy between the initial gain of the conditioning circuit and the design value. This affects the final conditioning effect and consequently the accuracy of the arc fault detection results. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a gain adjustment method and an AFCI conditioning circuit, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the accuracy and precision of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0006] In a first aspect, this application provides a gain adjustment method for an AFCI conditioning circuit, the AFCI conditioning circuit being used to provide multiple different gains, and the input port of the AFCI conditioning circuit being used to connect to a solar panel; the method includes:

[0007] By adjusting the gain of the AFCI conditioning circuit, a first output value corresponding to the AFCI conditioning circuit under various different gains is obtained; the first output value is used to characterize the conditioning circuit characteristics of the inverter corresponding to the solar panel under different operating parameters, and / or the solar panel and the inverter under different cable lengths.

[0008] Based on each of the first output values, the amplitude-frequency characteristic curve corresponding to the solar panel is obtained by fitting.

[0009] Based on the amplitude-frequency characteristic curve, the target gain adjustment strategy corresponding to the solar panel is determined.

[0010] According to the gain adjustment method of this application, by utilizing the multiple gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel is obtained based on the first output value of the AFCI conditioning circuit under various different gains. The gain of the solar panel is then adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the precision and accuracy of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0011] According to one embodiment of this application, obtaining a first output value of the AFCI conditioning circuit under various different gains by adjusting the gain of the AFCI conditioning circuit includes:

[0012] When the AFCI conditioning circuit operates based on the target gain, a second output value of the AFCI conditioning circuit is obtained to characterize the operation of the solar panel under the target operating scenario, and the second output value is determined as the first output value of the solar panel under the target gain.

[0013] The target operating scenario is the scenario where the cable length is the shortest and the operating parameters are the worst.

[0014] According to one embodiment of this application, when the AFCI conditioning circuit operates based on a target gain, acquiring a second output value of the AFCI conditioning circuit to characterize the solar panel operating under a target operating scenario includes:

[0015] When the AFCI conditioning circuit operates based on the target gain, a target signal is injected into the target position corresponding to the solar panel to obtain the second output value output by the AFCI conditioning circuit.

[0016] The target signal is adjusted until the second output value reaches the critical output value corresponding to the target gain of the solar panel, and the critical output value is determined as the second output value.

[0017] According to one embodiment of this application, determining the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve includes:

[0018] Based on the values ​​of the characteristic frequency points in the amplitude-frequency response curve, multiple static gain levels are determined.

[0019] The gain of the solar panel is adjusted based on the multiple static gain levels.

[0020] According to one embodiment of this application, adjusting the gain of the solar panel based on the plurality of static gain levels includes:

[0021] The highest level among the multiple static gain levels is determined as the initial level;

[0022] When the AFCI conditioning circuit operates based on the gain corresponding to the initial gear, the third output value of the AFCI conditioning circuit is obtained.

[0023] If the third output value is less than the threshold gear, the initial gear remains unchanged;

[0024] If the third output value is greater than the threshold level, the initial level is reduced.

[0025] According to one embodiment of this application, adjusting the gain of the solar panel based on the plurality of static gain levels includes:

[0026] Based on the ripple signal with a specific voltage and frequency, the actual cable length corresponding to the solar panel is determined by comparing the frequency response with the amplitude-frequency characteristic curve.

[0027] Based on the actual cable length, an initial static gain level is determined from the plurality of static gain levels;

[0028] The gain of the solar panel is adjusted based on the initial static setting.

[0029] According to one embodiment of this application, determining the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve includes:

[0030] Based on the multiple actual output values ​​of the AFCI conditioning circuit under the current static gain setting during the operation of the solar panel, the risk status is determined; the risk status includes no risk or risk present.

[0031] Based on the risk status and the current static gain level, the gain of the solar panel is adjusted.

[0032] According to one embodiment of this application, adjusting the gain of the solar panel based on the risk status and the current static gain level includes:

[0033] Under the aforementioned risk-free conditions, the current static gain level remains unchanged;

[0034] If there is a risk and the current static gain level is not the lowest level, the current static gain level shall be lowered.

[0035] If there is a risk and the current static gain level is the lowest level, the inverter corresponding to the solar panel will be shut down.

[0036] According to one embodiment of this application, the determination of the risk status based on multiple actual output values ​​corresponding to the current static gain level of the AFCI conditioning circuit during the operation of the solar panel includes:

[0037] If the number of actual output values ​​exceeding the saturation threshold exceeds the target proportion, the risk status is determined to be risky.

[0038] If the number of actual output values ​​exceeding the saturation threshold does not exceed the target proportion, the risk status is determined to be risk-free.

[0039] According to one embodiment of this application, determining the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve includes:

[0040] If, based on the amplitude-frequency characteristic curve, it is determined that each characteristic frequency point is within the target range, then, based on the amplitude-frequency characteristic curve, the target gain adjustment strategy corresponding to the solar panel is determined.

[0041] If, based on the amplitude-frequency characteristic curve, it is determined that at least one characteristic frequency point is not within the target range, the function of the solar panel or the AFCI conditioning circuit is abnormal.

[0042] According to one embodiment of this application, determining the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve includes:

[0043] The current ripple signal is acquired when the control bus voltage is higher than the input voltage and the difference is not greater than the first threshold.

[0044] If no arc-like noise is detected after processing the current ripple signal, the target gain adjustment strategy corresponding to the solar panel is determined based on the amplitude-frequency characteristic curve.

[0045] If the current ripple signal is processed and arc-like noise is detected, it is determined that the AFCI detection link is malfunctioning.

[0046] According to one embodiment of this application, determining the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve includes:

[0047] When the control bus voltage is higher than the input voltage and the difference is greater than the second threshold, the actual output value of the AFCI conditioning circuit is obtained.

[0048] When the actual output value is not saturated, the target gain adjustment strategy corresponding to the solar panel is determined based on the amplitude-frequency characteristic curve.

[0049] If the actual output value is saturated, it is determined that the AFCI detection link function is abnormal.

[0050] Secondly, this application provides a gain adjustment device for an AFCI conditioning circuit, the AFCI conditioning circuit being used to provide a variety of different gains, and the input port of the AFCI conditioning circuit being used to connect to a solar panel; the device includes:

[0051] The first processing module is used to obtain a first output value of the AFCI conditioning circuit under various different gains by adjusting the gain of the AFCI conditioning circuit; the first output value is used to characterize the conditioning circuit characteristics of the inverter corresponding to the solar panel under different operating parameters, and / or the solar panel and the inverter under different cable lengths.

[0052] The second processing module is used to fit the amplitude-frequency characteristic curve corresponding to the solar panel based on each of the first output values;

[0053] The third processing module is used to determine the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve.

[0054] According to the gain adjustment device of this application, by utilizing the multiple gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel is obtained based on the first output value of the AFCI conditioning circuit under various different gains. Thus, the gain of the solar panel is adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the precision and accuracy of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0055] Thirdly, this application provides an AFCI conditioning circuit, including:

[0056] A fault detection device, wherein the input port of the fault detection device is used to connect to a solar panel, and the fault detection device is used to output a first output value corresponding to the solar panel under various different gains by adjusting the gain of the fault detection device;

[0057] The AFCI intelligent module is connected to the output port of the fault detection device and is used to fit the amplitude-frequency characteristic curve corresponding to the solar panel based on each of the first output values; and to determine the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve.

[0058] Fourthly, this application provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the gain adjustment method as described in the first aspect above.

[0059] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the gain adjustment method as described in the first aspect above.

[0060] The above-described one or more technical solutions in the embodiments of this application have at least one of the following technical effects:

[0061] By utilizing the various gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel can be obtained based on the first output value of the AFCI conditioning circuit under various different gains. The gain of the solar panel can then be adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the precision and accuracy of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0062] Furthermore, by dynamically adjusting the gain level, it can respond promptly to some instantaneous fluctuations caused by photovoltaic strings and inverters, and can respond quickly to extreme differences in solar panels caused by weather, thus improving the response rate and exhibiting high real-time performance.

[0063] Furthermore, while adjusting the gain of the solar panel based on the output value of the AFCI conditioning circuit, the AFCI conditioning circuit and the solar panel can also perform a self-test. If the self-test passes, the gain can be adjusted, further improving the accuracy of the gain adjustment and the stability of the system operation.

[0064] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0065] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0066] Figure 1 is a flowchart illustrating one of the gain adjustment methods provided in an embodiment of this application;

[0067] Figure 2 is a second schematic flowchart of the gain adjustment method provided in the embodiments of this application;

[0068] Figure 3 is one of the structural schematic diagrams of the AFCI conditioning circuit provided in the embodiment of this application;

[0069] Figure 4 is a second schematic diagram of the AFCI conditioning circuit provided in an embodiment of this application;

[0070] Figure 5 is a third flowchart illustrating the gain adjustment method provided in the embodiments of this application;

[0071] Figure 6 is a third schematic diagram of the AFCI conditioning circuit provided in the embodiment of this application;

[0072] Figure 7 is a fourth flowchart illustrating the gain adjustment method provided in the embodiments of this application;

[0073] Figure 8 is one of the schematic diagrams of intermediate results of the gain adjustment method provided in the embodiments of this application;

[0074] Figure 9 is a second schematic diagram of the intermediate results of the gain adjustment method provided in the embodiments of this application;

[0075] Figure 10 is a fifth flowchart illustrating the gain adjustment method provided in the embodiments of this application;

[0076] Figure 11 is a fourth schematic diagram of the AFCI conditioning circuit provided in the embodiment of this application;

[0077] Figure 12 is a schematic diagram of the intermediate results of the gain adjustment method provided in the embodiments of this application (the third one).

[0078] Figure 13 is the fifth schematic diagram of the AFCI conditioning circuit provided in the embodiment of this application;

[0079] Figure 14 is a sixth schematic flowchart of the gain adjustment method provided in the embodiments of this application;

[0080] Figure 15 is a sixth schematic diagram of the AFCI conditioning circuit provided in the embodiment of this application;

[0081] Figure 16 is a seventh schematic diagram of the AFCI conditioning circuit provided in an embodiment of this application;

[0082] Figure 17 is a schematic diagram of the AFCI conditioning circuit provided in the embodiment of this application (eighth of the following).

[0083] Figure 18 is a schematic diagram of the AFCI conditioning circuit provided in an embodiment of this application;

[0084] Figure 19 is a seventh flowchart illustrating the gain adjustment method provided in the embodiments of this application;

[0085] Figure 20 is a schematic diagram of the gain adjustment device provided in an embodiment of this application;

[0086] Figure 21 is a schematic diagram of the structure of the electronic device provided in an embodiment of this application;

[0087] Figure 22 is a schematic diagram of the fault detection device provided in an embodiment of this application;

[0088] Figure 23 is a schematic diagram of the operation of the fault detection device provided in the embodiment of this application;

[0089] Figure 24 is a control timing diagram of the fault detection device provided in an embodiment of this application;

[0090] Figure 25 is a schematic diagram of the relationship between sampling signal strength and cable length provided in an embodiment of this application;

[0091] Figure 26 is a schematic diagram comparing the FFT decomposition relationship of the sampled signals before and after notch filtering provided in the embodiments of this application;

[0092] Figure 27 is a schematic diagram comparing the sampling signal intensity before and after notch filtering according to an embodiment of this application;

[0093] Figure 28 is a schematic diagram of the signal processing module provided in an embodiment of this application;

[0094] Figure 29 is a schematic diagram of one of the notch filter circuits provided in the embodiments of this application;

[0095] Figure 30 is a second schematic diagram of the notch filter circuit provided in an embodiment of this application;

[0096] Figure 31 is a flowchart illustrating the fault detection method provided in an embodiment of this application. Detailed Implementation

[0097] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0098] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0099] The gain adjustment method, gain adjustment device, electronic device, and readable storage medium provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0100] The gain adjustment method can be applied to the terminal, and can be executed by the hardware or software in the terminal.

[0101] The gain adjustment method provided in this application embodiment can be executed by an electronic device or a functional module or entity in an electronic device that can implement the gain adjustment method. The electronic devices mentioned in this application embodiment include, but are not limited to, mobile phones, tablets, computers, cameras, and wearable devices. The gain adjustment method provided in this application embodiment is described below using an electronic device as the execution subject.

[0102] As shown in Figure 1, the gain adjustment method includes steps S110, S120 and S130.

[0103] Step S110: By adjusting the gain of the AFCI conditioning circuit, obtain the first output value of the AFCI conditioning circuit under various different gains;

[0104] In this step, the gain adjustment method is used in the AFCI conditioning circuit, and the solar panel is connected to the AFCI conditioning circuit. The AFCI conditioning circuit can be an Arc Fault Circuit Interrupter (AFCI) conditioning circuit, which is a key signal processing part in the AFCI and is mainly used to detect and analyze the characteristics of arc faults in the circuit.

[0105] This AFCI conditioning circuit can provide conditioning gain of different magnitudes. The structure of the AFCI conditioning circuit and the gain adjustment method are described below.

[0106] The photovoltaic-storage system includes solar panels and an inverter. The solar panels are connected to the inverter via output phase lines. The DC-AC conversion module in the inverter completes the AC-DC conversion and is connected to the external power grid. The AFCI conditioning circuit includes a current ripple sampling unit and an operational amplifier filter module.

[0107] The current ripple sampling unit can be a current transformer or a current sensor, etc., connected to the output phase line. The current ripple sampling unit is used to extract the ripple characteristic signal of the PV branch current.

[0108] Understandably, in the AFCI topology, the downstream stage is a boost inductor. The larger the PV current / MPPT current ratio, the more significant the inductance decay of the boost inductor; conversely, the lower the inductance, the greater the ripple noise, and the easier it is for the AFCI to saturate. The inverter can indirectly determine the severity of AFCI saturation by detecting the PV current / MPPT current ratio. Specifically, when the PV current / MPPT current ratio is at its maximum, the ripple is at its maximum and the saturation is most likely; when the PV current / MPPT current ratio is at its minimum, the ripple is at its minimum and the saturation is least likely. In addition, the duty cycle of the boost unit is also a crucial factor affecting the magnitude of ripple noise. When the duty cycle is 0.5, D*(1-D) is at its maximum, meaning the ripple noise is at its maximum when the input voltage is half the bus voltage.

[0109] The operational amplifier filtering module is connected to the current ripple sampling unit and amplifies and filters the output current signal of the current ripple sampling unit. During actual operation, when an electric arc is generated, the current ripple sampling unit senses and detects the intensity of the arc, thus outputting electrical signals of varying intensities. The intensity of the output electrical signal can be affected by factors such as the inductance coefficient of the electronic components in the current sensing device and the resistance value of the sampling resistor. The electrical signal output by the current ripple sampling unit is amplified and filtered by the operational amplifier filtering module to form the output value.

[0110] The AFCI conditioning circuit is equipped with multiple sets of current ripple sampling units with different gains and / or multiple sets of operational amplifier filter modules with different gains, which are used to generate output values ​​under different gains.

[0111] In some embodiments, the current ripple sampling unit includes: a current detection mechanism and a sampling resistor, wherein the current detection mechanism is connected to the output phase line, the sampling resistor is connected to the current detection mechanism, and an operational amplifier filtering module is connected to the sampling resistor to amplify the sampling characteristics of the sampling resistor and filter out noise signals.

[0112] Taking a current ripple sampling unit with three sets of different gains as an example, in these three sets of current ripple sampling units with different gains, the current detection mechanism in each set of current ripple sampling units has the same operating parameters, and the sampling resistor has multiple sets of different gain operating parameters, so that multiple sets of sampling features of different sizes can be obtained. After being amplified and filtered by the operational amplifier filtering module, multiple output values ​​under different gains are formed.

[0113] Since the generated electric arc is typically a discrete value, K is used to represent the magnitude of the arc characteristic signal. In this embodiment, the saturation threshold of the AD port in the control processing module is 3K. Therefore, the resistance value of the sampling resistor and the amplification factor of the operational filtering module remain unchanged. By adjusting the mutual inductance coefficient of the current transformer, which serves as the current detection mechanism, different gain factors can be controlled. For the same arc signal, different output values ​​can be output. As the cable length increases, the worst-case noise floor increases accordingly. Therefore, increasing the mutual inductance coefficient of the current transformer can increase the output value while ensuring it does not exceed the saturation threshold of the AD port in the control processing module.

[0114] In actual operation, the current ripple value of the solar panel under different inverter operating conditions can be tested by setting the AFCI conditioning circuit to the corresponding gain.

[0115] The first output value can be the output value corresponding to different operating conditions and different cable lengths. Different operating conditions can include severe operating conditions, which can be when the peak-to-peak value is large enough, such as approaching or reaching saturation.

[0116] In actual operation, the input value of the AFCI conditioning circuit is the current ripple value, and each current ripple value corresponds to the output value of the AFCI conditioning circuit.

[0117] For inverters, under the nominal operating conditions and rated input range, there exists a certain adverse operating condition, that is, the AFCI performance is poor under this condition. In the AFCI design of inverters, this poor performance can generally be represented as the critical value of unsaturation; this adverse operating condition is the adverse boundary condition.

[0118] For example, if the ADC reference voltage is 3.3V and the derating requirement is 10%, then the critical design output value can be set to OUTA.

[0119] If the gain is 10, then for a boundary output A, there must be a boundary input A; if the gain is 5, then for a boundary output B, there must be a boundary input B. The boundary input B is always greater than the boundary input A. This means that the larger ripple signal, the boundary input B, originates from a shorter cable or a larger PV current / MPPT current compared to A. Therefore, for each gain, there is a corresponding worst-case boundary condition where even a slightly larger ripple input will cause the output to saturate.

[0120] In actual operation, by adjusting the inverter's operating parameters, the first output value corresponding to different gains under the same operating conditions and cable lengths of the solar panel can be obtained. By changing the operating conditions and / or cable lengths, multiple first output values ​​corresponding to different operating conditions and / or cable lengths can be obtained.

[0121] In some embodiments, step S110 may include:

[0122] When the AFCI conditioning circuit operates based on the target gain, the second output value of the AFCI conditioning circuit is obtained to characterize the operation of the solar panel under the target operating scenario, and the second output value is determined as the first output value of the solar panel under the target gain.

[0123] In this embodiment, the target operating scenario can be the scenario with the shortest cable length and the worst operating parameters.

[0124] The target gain can be any gain achievable by the AFCI conditioning circuit. The methods for obtaining the first output value corresponding to different gains are similar.

[0125] The second output value is the actual output value of the AFCI conditioning circuit, and the first output value is the actual output value of the AFCI conditioning circuit when the solar panel is operating under the target operating scenario and the AFCI conditioning circuit is operating based on the target gain.

[0126] It should be noted that, in this application, as shown in Figure 5, the first output value can be the output value of the AFCI conditioning circuit when the inverter is actually operating in the target operating scenario. For example, by traversing the output values ​​of the AFCI conditioning circuit under various operating conditions and cable lengths, the output value under the worst operating condition and the shortest cable length can be obtained; or it can be the output value of the AFCI conditioning circuit when the inverter is not operating, by inputting a target signal to simulate the operation of the inverter.

[0127] In some embodiments, when the AFCI conditioning circuit operates based on a target gain, obtaining a second output value of the AFCI conditioning circuit to characterize the solar panel operating in a target operating scenario may include:

[0128] When the AFCI conditioning circuit operates based on the target gain, a target signal is injected into the target position corresponding to the solar panel to obtain the second output value of the AFCI conditioning circuit.

[0129] Adjust the target signal until the second output value reaches the critical output value corresponding to the target gain of the solar panel, and determine the critical output value as the second output value.

[0130] In this embodiment, the target signal is an artificially injected signal, an instantaneous value that can be adjusted, used to simulate the signal injection during inverter operation. The target signal can be a sine wave signal or a triangular wave signal. This target signal can be injected using a signal generator during the production process, or injected using a single-board DAC during the operation process.

[0131] As shown in Figure 11, the target location can be set across the sampling resistor on the secondary side of the current sensor / current transformer to simulate signal injection during inverter operation. For cases where the current sensor / current transformer is connected in series in the circuit from the solar panel to the inverter, the target location can include, but is not limited to: between the solar panel and the current sensor / current transformer (i.e., before the transformer / sensor); or after the current sensor / current transformer (i.e., at the sampling resistor); or any stage of the AFCI conditioning circuit.

[0132] Taking the target location as TP point as shown in Figure 3 as an example, by setting the signal injection port TP point as shown in Figure 4, the signal is injected through the signal generator of the FT test machine to simulate the signal injection when the inverter is working, and the output value output by the output terminal of the AFCI conditioning circuit is read. Thus, the amplitude-frequency curve of the target frequency point can be fitted, thereby performing initial calibration of the amplitude-frequency characteristics of the solar panel under test.

[0133] As shown in Figure 5, taking an ADC reference voltage of 3.3V and a derating requirement of 10% as an example, the corresponding critical design output signal of the AFCI conditioning circuit is OUTA. By injecting a target signal INA at point TP, the output signal OUT2A of the AFCI conditioning circuit can be obtained. By adjusting the value of INA so that OUT2A = OUTA, the target signal INA is equivalent to the ripple sampling value inside the inverter when the critical design output value is OUTA.

[0134] Since the signal processing unit may have multiple gain sets, such as DeltaA (gain A) and DeltaB (gain B), under the worst-case operating condition of a certain white-box test, there exists a worst-case output. Therefore, corresponding to DeltaA, we can obtain the worst-case output value OUTA; corresponding to DeltaB, we can obtain the worst-case output value OUTB.

[0135] For the same type of solar panel, based on the results of OUTA and OUTB, and through white-box testing, the signals INA and INB that should be injected at the TP point for signal injection can be obtained. When the signals injected at the TP point are INA and INB, OUT2A and OUT2B can be obtained accordingly, and OUT2A = OUTA and OUT2B = OUTB can be satisfied. OUT2A and OUT2B are the first output values, and INA and INB are the target signals.

[0136] Similarly, for multiple gains DeltaA, DeltaB, ..., DeltaN, the input points INA, INB, ..., INN that are worth judging can be identified. Furthermore, the first output values ​​OUT2A, OUT2B, ..., OUT2N can be calibrated as the boundary output signal sampling values ​​of the solar panel under test under the worst-case scenario. The fitted amplitude-frequency response curve can then characterize the output curve of the solar panel under test caused by factors such as the differences in active devices and the tolerance differences in passive devices.

[0137] According to the gain adjustment method provided in the embodiments of this application, the operating state of the inverter is simulated by injecting a target signal, without the need to turn on the inverter, which has high flexibility and is easy to implement.

[0138] Step S120: Based on each first output value, fit the amplitude-frequency characteristic curve corresponding to the solar panel;

[0139] In this step, arc faults typically generate high-frequency noise signals within a specific frequency range. These signals exhibit certain characteristic frequencies (such as the fundamental frequency and its harmonics) in the spectrum. The amplitude-frequency response curve includes multiple characteristic frequencies, with each characteristic frequency corresponding to a gain.

[0140] The amplitude-frequency characteristic is equal to the ratio of the frequency response output amplitude to the input signal amplitude.

[0141] Gain is the ratio of the frequency response output amplitude to the input signal amplitude. It reflects the system's response characteristics to signals of different frequencies and describes the system's ability to transmit sinusoidal signals of different frequencies.

[0142] If the output signal sample value OUT reads the effective value K, the amplitude-frequency characteristic of that frequency point is 2*1.414*K divided by the peak-to-peak value of the input signal.

[0143] If the acquired variable is a 16-bit binary variable and the AD port reference level is 3.3V, then if K is read, the multiple is K / 65535*3.3 divided by the peak-to-peak value of the input signal. This multiple represents the amplitude-frequency characteristic at this frequency point.

[0144] The amplitude-frequency response curve is used to characterize the first output value of a solar panel under a certain working environment, corresponding to different gains. This first output value is related to the inverter operating conditions and the length of the PV cable. Different working environments (such as different solar panels, different operating conditions, or different cable lengths) may result in different amplitude-frequency response curves. The amplitude-frequency response curve obtained by fitting can be used for initial calibration of the amplitude-frequency characteristics of the solar panel under test.

[0145] It's understandable that once a specific board in an inverter is manufactured, its characteristic parameters are fixed. These parameters are influenced by many factors, including a) the core value (u) and inductance of the current transformer / current sensor; b) the tolerances of the filter's RC components; and c) the inverter system impedance. As shown in Figure 12, the two curves are fitting results of the amplitude-frequency response curves of two boards designed with identical parameters. However, due to the aforementioned influencing factors (characteristic parameters), the two curves are roughly similar but slightly different. Injecting a 100mV 27kHz sine wave, if the design value is 22 times, will result in a 27kHz sine wave of approximately 2.2V, which is consistent with expectations. Based on this, the amplitude-frequency response at 27kHz can be approximated as a multiple K, where K≈22.

[0146] For the same solar panel, based on the critical output values ​​OUTA and OUTB at different gains, white-box experiments can be used to obtain the target signal that should be injected at the TP point for signal injection. When the target signals injected at the TP point are INA and INB, the first output values ​​OUT2A and OUT2B are obtained respectively, where OUT2A = OUTA and OUT2B = OUTB.

[0147] At this point, for an AFCI conditioning circuit with DeltaA (gain A) and DeltaB (gain B), the injected target signals INA and INB can bring the solar panel under test to the boundary state. By adjusting the frequency points of the injected INA and INB, the complete amplitude-frequency response curves corresponding to DeltaA (gain A) and DeltaB (gain B) can be obtained, as shown in Figure 8.

[0148] Understandably, through steps S110 to S120, the input points INA, INB...INN that are worth judging can be identified, and the outputs OUT2A, OUT2B...OUT2N can be calibrated, corresponding to the boundary output signal sampling values ​​of the tested solar panel under the worst-case scenario. The output result curve (i.e., the amplitude-frequency characteristic curve) fitted at this time can characterize the output curve of the solar panel caused by factors such as the differences in active devices and the tolerance differences in passive devices.

[0149] The method described in this application can be used to simulate scenarios where the target operating condition is the shortest cable length and the most severe operating parameters, and to fit the AFCI amplitude-frequency response curve of a specific board (or its associated system). Theoretically, the more input points there are, the more accurate the amplitude-frequency response curve will be.

[0150] Step S130: Determine the target gain adjustment strategy based on the amplitude-frequency characteristic curve.

[0151] In this step, the target gain adjustment strategy is a control strategy for adjusting the gain, which may include, but is not limited to: determining the initial gain corresponding to the solar panel. In actual execution, the initial gain can be determined according to the characteristic frequency point in the amplitude-frequency characteristic curve. In some embodiments, the target gain adjustment strategy may also include dynamically adjusted gain, such as dynamically adjusting the corresponding gain according to the characteristic frequency point in the amplitude-frequency characteristic curve based on the real-time operating status of the solar panel.

[0152] Based on the amplitude-frequency characteristic curve of the current solar panel obtained by fitting, the gain control strategy of the solar panel can be set accordingly to cope with the differences in active devices and the tolerance differences in passive devices, improve the accuracy and precision of gain control, thereby improving the gain control effect and the accuracy of subsequent detection.

[0153] According to the gain adjustment method provided in the embodiments of this application, by utilizing the multiple gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel is obtained based on the first output value corresponding to the AFCI conditioning circuit under various different gains. Thus, the gain of the solar panel is adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the precision and accuracy of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0154] In some embodiments, step S130 may include:

[0155] Based on the gain corresponding to the characteristic frequency point in the amplitude-frequency response curve, multiple static gain levels are determined.

[0156] Gain adjustment is performed based on multiple static gain levels.

[0157] In this embodiment, it is understood that arc faults typically generate high-frequency noise signals within a specific frequency range. These signals will exhibit certain characteristic frequency points in the spectrum. If there is a multiple relationship between these characteristic frequency points, such as 2 times, 3 times, etc., it can be considered that there is a multiple identification result of the characteristic frequency points, which can serve as an important basis for judging arc faults.

[0158] If the amplitude-frequency response curve has a characteristic frequency point multiple identification result (marked as KIN), and satisfies the interval (lower limit MIN, upper limit MAX), that is, it meets the preset upper and lower limits, i.e.:

[0159] KINB, KINC...KINN∈(MIN, MAX)

[0160] Based on the above results, static gain settings are made for the AFCI gain levels: KINA, KINB, KINC...KINN, which correspond to levels A, B, C...N, respectively, representing the overall gain of signal processing units of different sizes.

[0161] In some embodiments, the highest level among multiple static gain levels can be used as the initial static gain to adjust the gain of the solar panel.

[0162] In some embodiments, the gain can be adjusted by selecting the corresponding static gain level based on the working environment of the solar panel and the length of the cable.

[0163] Understandably, after a photovoltaic inverter is installed, the cable length is mostly fixed, and there won't be frequent changes to the PV cable length. If the PV cable is long, to ensure performance, the initial gain set using the static range determination method is the maximum optimal gain.

[0164] The static gear determination method can identify single-board differences caused by differences in active components and tolerance differences in passive components, filter out defective products, and keep the initial gain of good products in the best and most reasonable state.

[0165] In some embodiments, adjusting the gain of a solar panel based on multiple static gain levels may include:

[0166] The highest level among multiple static gain levels is determined as the initial level;

[0167] When the AFCI conditioning circuit operates based on the gain corresponding to the initial gear, obtain the third output value of the AFCI conditioning circuit.

[0168] If the third output value is less than or equal to the threshold gear, the initial gear remains unchanged;

[0169] If the third output value is greater than the threshold gear, reduce the initial gear.

[0170] In this embodiment, when the inverter is connected to a solar panel on the market and starts generating electricity, since the cable length from the connected solar panel to the inverter does not change physically during the power generation process, there is an optimal initial speed among the multiple speeds.

[0171] In this embodiment, instead of relying on "knowing the exact cable length of the PV string connected to a certain inverter" for manual control, a signal generator or boost circuit can generate a wave so that the AFCI detection unit can sample the ripple signal and determine the optimal initial gear during the AFCI self-test during power-on initialization.

[0172] The purpose of the self-test here may include one or more of the following: a) determining the optimal initial gear; b) determining whether the overall AFCI link status is normal. The specific testing method will be described in the following examples and will not be elaborated here.

[0173] As shown in Figure 13, the first signal injected by the signal generator is coupled to the PV equivalent impedance model and the subsequent boost circuit in the primary side of the AFCI current ripple sampling unit. Because the Rpv(v,i), Cpv(v), and Lpv(i) are different for different lengths of solar panel cables, and C1 and L1 are fixed in the inverter initialization state (no current in the initialization stage), for a fixed first signal INPUT, because the C1 and L1 are fixed, the Rpv(v,i), Cpv(v), and Lpv(i) are different for different lengths of solar panel cables, and the injected signal shunt to the AFCI detection unit is also different. The corresponding output results for different cable lengths are RUNA, RUNB...RUNN.

[0174] Based on the experiment, the exact values ​​of RUNA, RUNB...RUNN can be obtained, as shown in Figure 14, and then the amplitude-frequency response threshold range at a certain frequency point under different cable lengths can be determined.

[0175] As can be understood, as shown in Figure 10, if the initial gear is the maximum gear, and the sample is less than or equal to the threshold gear under the first signal injection from the signal generator, it proves that the external cable length is extremely long. Keeping the maximum gear unchanged, the process ends.

[0176] If the sample value is greater than the threshold level under the first signal injection from the signal generator, it proves that the current level is too high and the level should be reduced.

[0177] In some embodiments, adjusting the gain of a solar panel based on multiple static gain levels may include:

[0178] Based on the ripple signal with a specific voltage and frequency, the actual cable length corresponding to the solar panel is determined by comparing the frequency response with the amplitude-frequency characteristic curve.

[0179] Based on the actual cable length, the initial static gain setting is determined from multiple static gain settings;

[0180] Gain adjustment is performed based on the initial static setting.

[0181] In this embodiment, as shown in Figure 16, the sampling control unit controls the solar panel to operate within a specific region of the IV curve, thereby controlling the output voltage of the solar panel and thus controlling the voltage of the ripple signal. The sampling control unit also controls the frequency of the Boost circuit, thereby controlling the frequency of the boost ripple signal. By comparing the boost ripple signal with the amplitude-frequency characteristic curve based on the specific voltage and frequency, the order of magnitude of the solar panel's Lpv(i) can be determined, leading to the determination of the external cable length and ultimately the initial static voltage level.

[0182] In some embodiments, a specific region can be the left slope of the maximum power point on the solar panel's IV curve, used to enable the solar panel to output a lower voltage. In actual implementation, the point can be selected based on the IV curve according to the "current bus voltage and required PV input voltage" needed for the boost ripple signal to be injected, so that the solar panel outputs a specific PV voltage.

[0183] Here, the order of magnitude of Lpv(i) characterizes the magnitude of the inductance. It can be understood that for specific types of cables (such as parallel conductors, coaxial cables, etc.), the inductance per meter of cable can be approximated as approximately 0.7 μH / m. Based on the standard conversion value of inductance, and knowing the order of magnitude of Lpv(i) for the solar panel, the cable length can be calculated accordingly.

[0184] As shown in Figure 18, the system injects a ripple signal with a specific voltage and frequency through a ripple injection unit. The injected ripple signal is acquired by the AFCI conditioning circuit detection CT and collected by the AFCI detection unit. By comparing the frequency response with the amplitude-frequency characteristic curve, the order of magnitude of the solar panel Lpv(i) can be determined, thereby determining the length of the external cable and the initial static position.

[0185] The implementation of the ripple injection unit is shown in Figure 17. The ripple signal generator can be a sine wave generator to generate a sine wave signal (i.e., ripple signal) with a specific voltage value and a specific frequency, which is coupled to the main circuit through the current transformer.

[0186] According to the gain adjustment method provided in the embodiments of this application, the initial gain can be kept in the best and most reasonable state based on the optimal initial gear judgment of AFCI self-test.

[0187] In some embodiments, step S130 may include:

[0188] Based on the current sampling values ​​at multiple moments corresponding to the normal operating state of the inverter, the risk status is determined; the risk status includes no risk or the presence of risk.

[0189] Gain control of the solar panel is performed based on the risk status and the current static gain level.

[0190] In this embodiment, the risk status is used to characterize whether there is a saturation risk. If there is a risk, it is considered that the currently selected gain exceeds the actual requirement of the cable length connected to the actual inverter.

[0191] If the output value is saturated, that is, the current gear gain is too high, it may cause the AFCI conditioning circuit to miss or false alarm.

[0192] Among them, the AFCI conditioning circuit failure to report, i.e. the failure of the DC arc fault detection function, means that when a DC arc occurs, it cannot be identified, and therefore cannot be disconnected in time, ultimately causing a fire.

[0193] False alarms from the AFCI conditioning circuit, i.e., false alarms from the DC arc fault detection function, can affect normal power generation.

[0194] In some embodiments, there is a situation where the gain level is selected too high, without saturation, but higher than the actual arc detection requirements (the longer the cable, the greater the required gain). A gain level that is too high will result in a large noise floor and may also easily lead to false alarms from the AFCI conditioning circuit.

[0195] For example, if an inverter is connected to a 300m cable, and considering the inverter's conditioning circuit parameters, a calculated second-level gain is just right, ensuring that the arcing noise from the 300m cable is clearly visible. If a third-level gain is selected, arcing noise from a 400m cable can be detected; this gain is too high, increasing the noise floor sampling during normal operation and thus raising the risk of false alarms. A fifth-level gain can detect arcing noise from an 800m cable, leading to sampling saturation and a sharp increase in AFCI false / missed alarms.

[0196] In some embodiments, determining the risk state based on the output values ​​of the AFCI conditioning circuit at multiple moments corresponding to the normal operating state of the inverter may include:

[0197] If the number of actual output values ​​exceeding the saturation threshold exceeds the target proportion, the risk status is determined to be "risk exists".

[0198] If the number of actual output values ​​exceeding the saturation threshold does not exceed the target proportion, the risk status is determined to be risk-free.

[0199] In this embodiment, the target ratio can be user-defined, such as set to 80% or 90%, etc., and this application does not limit it here. The saturation threshold can be a preset upper limit value corresponding to the effective value, such as set to 3V.

[0200] For example, the output of the AFCI conditioning circuit and the instantaneous effective value of the chip's input AD port can be collected continuously for 1024 points. When the proportion of the effective value of the output value that is greater than the saturation threshold Δmax exceeds 80%, it is judged as saturation.

[0201] In some embodiments, the existence of dynamic risk can also be determined by comparing the average of the effective values ​​of the output values ​​with the saturation threshold Δmax.

[0202] In this embodiment, the average of the valid values ​​of the output value can be calculated as follows:

[0203] Δaverage = 1 / (t2-t1)*∫[t1, t2]|Δ|dt

[0204] Where Δ is the average of the effective values ​​of the output, and [t1, t2] is the sampling period.

[0205] I) If the average Δ value ≤ Δmax, then there is currently no risk;

[0206] II) If the average Δ > Δmax, then a risk is identified.

[0207] As shown in Figure 19, in some embodiments, gain control of the solar panel based on the risk status and the current static gain level may include:

[0208] Under no-risk conditions, the current static gain level should be kept unchanged;

[0209] If there is a risk and the current static gain level is not the lowest level, lower the current static gain level.

[0210] If there is a risk and the current static gain setting is at its lowest level, control the inverter to shut down.

[0211] In this embodiment, I) if the average Δ value < Δmax, then there is currently no risk;

[0212] II) If the average Δ value > Δmax, then lower the current gear.

[0213] III) If the current gear is already the lowest gear, then an alarm will sound and the device will shut down.

[0214] The above formula can be a judgment criterion in the time domain or in the frequency domain.

[0215] In some embodiments, false alarm prevention identification can also be performed.

[0216] The strategies for preventing false alarms are as follows:

[0217] By reducing the loop reference of the circuit where the arc was detected to a negative value, the current is reduced. Then, the loop reference is immediately restored, allowing the current to recover.

[0218] a) If it is a real electric arc and the current cannot be restored, an AFCI alarm will be triggered;

[0219] b) If it is not a real electric arc, it is a false alarm and the current will recover.

[0220] In some embodiments, continuing to refer to Figure 19, gain control of the solar panel based on the risk status and the current static gain level may include:

[0221] If there is a risk and the alarm is false, lower the current static gain level.

[0222] In some embodiments, when the AI ​​model detects an electric arc, it can first determine whether there is a risk of saturation. If a saturation risk is determined to exist, and the false alarm prevention strategy determines it to be a false alarm, the static gain level is immediately reduced by one level.

[0223] In some embodiments, when there is a risk and the current static gain level is not the lowest level, after lowering the current static gain level, the method may further include:

[0224] After the target duration and / or after initializing the AFCI conditioning circuit, restore the static gain level to the initial gain level.

[0225] In this embodiment, the gear restoration strategy may include, but is not limited to: A) restoring the initial optimal gear after upgrade / initialization; B) restoring the initial optimal gear after 24 hours.

[0226] According to the gain adjustment method provided in the embodiments of this application, by dynamically adjusting the gain level, it can respond promptly to some instantaneous fluctuations caused by photovoltaic strings and inverters, and can respond quickly to extreme differences in solar panels caused by weather, thereby improving the response rate and having high real-time performance.

[0227] In some embodiments, the circuit can also perform a self-test to detect whether the solar panel and / or AFCI conditioning circuit are functioning properly. If the function is abnormal, an alarm message is output and boards that do not meet the design specifications are filtered out. If the function is normal, a gain adjustment strategy is executed.

[0228] In some embodiments, self-testing can be performed using various methods, such as generating waves based on a signal generator, generating open-loop waves based on a boost circuit, or generating waves based on a current transformer circuit.

[0229] Firstly, self-testing is performed based on the wave emitted by the signal generator.

[0230] As shown in Figure 13, the signal generation device can be: a) an internal DAC on the chip; b) a white noise generator. The internal DAC can output an injection signal of a specific frequency and magnitude at the injection point. The white noise generator can generate a white noise signal rich in harmonics, which can be achieved through Zener breakdown. Using these signal generation devices, the injection of target signals can be simulated in scenarios with the shortest cable length and the most severe operating parameters.

[0231] As shown in Figure 2, in some embodiments, step S130 may include:

[0232] Given that all characteristic frequency points are within the target range based on the amplitude-frequency response curve, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency response curve.

[0233] If, based on the amplitude-frequency response curve, it is determined that at least one characteristic frequency point is not within the target range, the solar panel function or the AFCI conditioning circuit function is abnormal.

[0234] In this embodiment, the target range can be user-defined, such as being set to the value of the ADC sampling reference value after de-rating. In some embodiments, the target range may include a preset upper limit (Max) and a lower limit (Min).

[0235] Self-testing can be performed based on the signal generator, as shown in Figure 15. After the self-test is started, the AFCI detection unit can detect the result normally, determine whether the overall AFCI link is in normal condition, and set the optimal initial gear.

[0236] If any point on the amplitude-frequency characteristic curve exceeds the preset upper or lower limit, the board is defective; the process ends.

[0237] If the amplitude-frequency response curve, the multiple identification results (marked as KIN) of all measured characteristic frequency points satisfy the interval (MIN, MAX), and conform to the upper and lower limits (upper limit Max and lower limit Min) of the preset amplitude-frequency response range for that frequency point, then according to the above results, the single panel is a good product. The curve fitting result of the good product is shown in Figure 9. The target gain control strategy corresponding to the solar panel can be further determined based on the amplitude-frequency response curve.

[0238] Secondly, self-testing is performed based on an open-loop waveform generated by the boost circuit.

[0239] The boost circuit generates an open-loop waveform, enabling the AFCI detection unit to detect the boost ripple signal shunted in the main circuit based on the AFCT detection CT, as shown in Figure 6. With the help of the AFCI self-test strategy based on the waveform generated by the boost circuit, the overall link function can be self-tested and identified, the functionality of the AFCI conditioning circuit in the actual application scenario can be determined, and the initial static gear setting can be provided.

[0240] For scenarios with high PV voltage input, a boost unit large and small wave self-test can be used, and the specific implementation method is as follows.

[0241] As shown in Figure 2, in some embodiments, step S130 may include:

[0242] The current ripple signal is acquired when the control bus voltage is higher than the input voltage and the difference is not greater than the first threshold.

[0243] In the absence of arc-like noise after processing the current ripple signal, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency characteristic curve.

[0244] After processing the current ripple signal and identifying arc-like noise, it was determined that the AFCI detection link was malfunctioning.

[0245] In this embodiment, the first threshold is a small positive value, used to control the bus voltage to be slightly higher than the input voltage, so as to generate the boost unit's large and small waves. After the current ripple sampling unit detects it, a large number of irrelevant harmonics are generated in the operational amplifier filtering module, forming arc-like noise. Whether the arc-like noise can be identified is used to test the overall function of the AFCI conditioning circuit.

[0246] For scenarios with low PV voltage input, a boost unit limit ripple self-test can be used, and the specific implementation method is as follows.

[0247] As shown in Figure 2, in some embodiments, step S130 may include:

[0248] When the control bus voltage is higher than the input voltage and the difference is greater than the second threshold, the actual output value of the AFCI conditioning circuit is obtained.

[0249] When the actual output value is not saturated, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency characteristic curve.

[0250] If the actual output value is saturated, it is determined that the AFCI detection link function is abnormal.

[0251] In this embodiment, the second threshold is a large positive number, and the second threshold is greater than the first threshold. It is used to control the bus voltage to be much higher than the input voltage, forming a 0.5 duty cycle (if the input voltage is K, then the control bus voltage is 2K). At this time, the D*(1-D) coefficient is the largest, the boost inductor ripple is the largest, and the worst test condition can be simulated. This condition can be approximately equivalent to the worst working parameter scenario in most scenarios and the inverter boost unit can be used to simulate signal injection.

[0252] According to the gain adjustment method provided in the embodiments of this application, while adjusting the gain of the solar panel based on the output value of the AFCI conditioning circuit, the AFCI conditioning circuit and the solar panel can also be self-tested. If the self-test passes, the gain adjustment is performed, thereby further improving the accuracy of gain adjustment and the stability of system operation.

[0253] The gain adjustment method provided in this application can be executed by a gain adjustment device. This application uses a gain adjustment device executing the gain adjustment method as an example to illustrate the gain adjustment device provided in this application.

[0254] This application also provides a gain adjustment device.

[0255] As shown in Figure 20, the gain adjustment device is used for the AFCI conditioning circuit, which provides a variety of different gains. The input port of the AFCI conditioning circuit is used to connect to the solar panel. The device includes: a first processing module 2010, a second processing module 2020, and a third processing module 2030.

[0256] The first processing module 2010 is used to obtain the first output value of the AFCI conditioning circuit under various different gains by adjusting the gain of the AFCI conditioning circuit; the first output value is used to characterize the AFCI conditioning circuit characteristics of the inverter corresponding to the solar panel under different operating parameters, and / or the solar panel and inverter under different cable lengths.

[0257] The second processing module 2020 is used to fit the amplitude-frequency characteristic curve corresponding to the solar panel based on each first output value;

[0258] The third processing module 2030 is used to determine the target gain adjustment strategy for the solar panel based on the amplitude-frequency characteristic curve.

[0259] According to the gain adjustment device provided in the embodiments of this application, by utilizing the multiple gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel is obtained based on the first output value corresponding to the AFCI conditioning circuit under multiple different gains. Thus, the gain of the solar panel is adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the accuracy and precision of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0260] In some embodiments, the first processing module 2010 is configured to:

[0261] When the AFCI conditioning circuit operates based on the target gain, the second output value of the AFCI conditioning circuit is obtained to characterize the operation of the solar panel under the target operating scenario, and the second output value is determined as the first output value of the solar panel under the target gain.

[0262] The target operating scenario is the one with the shortest cable length and the worst operating parameters.

[0263] In some embodiments, the first processing module 2010 is configured to:

[0264] When the AFCI conditioning circuit operates based on the target gain, a target signal is injected into the target position corresponding to the solar panel to obtain the second output value of the AFCI conditioning circuit.

[0265] Adjust the target signal until the second output value reaches the critical output value corresponding to the target gain of the solar panel, and determine the critical output value as the second output value.

[0266] In some embodiments, the third processing module 2030 is configured to:

[0267] Based on the values ​​of the characteristic frequency points in the amplitude-frequency response curve, multiple static gain levels are determined.

[0268] The gain of the solar panel is adjusted based on multiple static gain levels.

[0269] In some embodiments, the third processing module 2030 is configured to:

[0270] The highest level among multiple static gain levels is determined as the initial level;

[0271] When the AFCI conditioning circuit operates based on the gain corresponding to the initial gear, obtain the third output value of the AFCI conditioning circuit.

[0272] If the third output value is less than the threshold gear, the initial gear remains unchanged;

[0273] If the third output value is greater than the threshold gear, reduce the initial gear.

[0274] In some embodiments, the third processing module 2030 is configured to:

[0275] Based on the boost ripple signal with a specific voltage and frequency, the actual cable length corresponding to the solar panel is determined by comparing the frequency response with the amplitude-frequency characteristic curve.

[0276] Based on the actual cable length, the initial static gain setting is determined from multiple static gain settings;

[0277] Gain adjustment of solar panels is performed based on the initial static setting.

[0278] In some embodiments, the third processing module 2030 is configured to:

[0279] Based on the multiple actual output values ​​of the AFCI conditioning circuit under the current static gain setting during the operation of the solar panel, the risk status is determined; the risk status includes no risk or risk present.

[0280] The gain of the solar panel is adjusted based on the risk status and the current static gain level.

[0281] In some embodiments, the third processing module 2030 is configured to:

[0282] Under no-risk conditions, the current static gain level should be kept unchanged;

[0283] If there is a risk and the current static gain level is not the lowest level, lower the current static gain level.

[0284] If there is a risk and the current static gain setting is at its lowest level, shut down the inverter corresponding to the solar panel.

[0285] In some embodiments, the third processing module 2030 is configured to:

[0286] If the number of actual output values ​​exceeding the saturation threshold exceeds the target proportion, the risk status is determined to be "risk exists".

[0287] If the number of actual output values ​​exceeding the saturation threshold does not exceed the target proportion, the risk status is determined to be risk-free.

[0288] In some embodiments, the third processing module 2030 is configured to:

[0289] Given that all characteristic frequency points are within the target range based on the amplitude-frequency response curve, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency response curve.

[0290] If, based on the amplitude-frequency response curve, it is determined that at least one characteristic frequency point is not within the target range, the solar panel function or the AFCI conditioning circuit function is abnormal.

[0291] In some embodiments, the third processing module 2030 is configured to:

[0292] The current ripple signal is acquired when the control bus voltage is higher than the input voltage and the difference is not greater than the first threshold.

[0293] In the absence of arc-like noise after processing the current ripple signal, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency characteristic curve.

[0294] After processing the current ripple signal and identifying arc-like noise, it was determined that the AFCI detection link was malfunctioning.

[0295] In some embodiments, the third processing module 2030 is configured to:

[0296] When the control bus voltage is higher than the input voltage and the difference is greater than the second threshold, the actual output value of the AFCI conditioning circuit is obtained.

[0297] When the actual output value is not saturated, the target gain adjustment strategy for the solar panel is determined based on the amplitude-frequency characteristic curve.

[0298] If the actual output value is saturated, it is determined that the AFCI detection link function is abnormal.

[0299] The gain adjustment device in this application embodiment can be an electronic device or a component within an electronic device, such as an integrated circuit or a chip. The electronic device can be a terminal or other devices besides a terminal. For example, the electronic device can be a mobile phone, tablet computer, laptop computer, PDA, in-vehicle electronic device, mobile internet device (MID), augmented reality (AR) / virtual reality (VR) device, robot, wearable device, ultra-mobile personal computer (UMPC), netbook, or personal digital assistant (PDA), etc. It can also be a server, network attached storage (NAS), personal computer (PC), television set (TV), ATM, or self-service machine, etc. This application embodiment does not specifically limit the specific type of device.

[0300] The gain adjustment device in this application embodiment can be a device with an operating system. This operating system can be Android, iOS, or other possible operating systems; this application embodiment does not specifically limit it.

[0301] The gain adjustment device provided in this application embodiment can realize the various processes implemented in the method embodiments of Figures 1 to 19. To avoid repetition, it will not be described again here.

[0302] This application also provides an AFCI conditioning circuit.

[0303] The AFCI conditioning circuit includes a fault detection device and an AFCI intelligent module.

[0304] The input port of the fault detection device is used to connect to the solar panel, and the fault detection device is used to output the first output value of the solar panel under various different gains by adjusting the gain of the fault detection device.

[0305] The AFCI intelligent module is connected to the output port of the fault detection device to execute the gain adjustment method described in any of the above embodiments. Based on each first output value, it fits the amplitude-frequency characteristic curve corresponding to the solar panel and determines the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve.

[0306] According to the AFCI conditioning circuit provided in the embodiments of this application, by utilizing the various gain adjustment functions provided by the AFCI conditioning circuit, the amplitude-frequency characteristic curve of the solar panel can be obtained based on the first output value corresponding to the AFCI conditioning circuit under various different gains. Thus, the gain of the solar panel can be adjusted according to the amplitude-frequency characteristic curve, which can cope with the differences in active devices and the tolerance differences in passive devices, improve the accuracy and precision of gain adjustment, thereby improving the gain control effect and the accuracy of subsequent detection.

[0307] In some embodiments, an injection port is provided before the input port for injecting the target signal.

[0308] This application also provides an AFCI gain control system.

[0309] As shown in Figure 7, the AFCI gain control system includes: a cloud, a smart gateway, and at least one AFCI conditioning circuit as described in any of the above embodiments.

[0310] The system consists of a smart gateway that communicates with the cloud and an AFCI conditioning circuit connected to the smart gateway. The cloud, acting as the first-level AFCI smart gain management layer, determines the gain level of the corresponding device within the entire system. The smart gateway, acting as the second-level AFCI smart gain management layer, collects data uploaded by lower-level devices and sends it to the cloud. Simultaneously, based on the smart gain level set by the cloud, it implements global control and management of the sampling and control devices for the connected AFCI conditioning signal energy. The AFCI conditioning circuit, acting as the third-level AFCI smart gain execution layer, executes the corresponding smart gain level control according to the control and management of the smart gateway, and completes the sampling, collection, and uploading of the required data.

[0311] A photovoltaic (PV) power generation system is a system that directly converts solar energy into electrical energy using solar panels. During the power generation process of a PV system, there is a risk of DC arcing. An arc fault circuit interrupter (AFCI) is typically used to detect DC arcing in the PV system, thereby mitigating this risk. Applying an AFCI to detect DC arcing requires accurately capturing the background noise signal of the current generated during the arcing process.

[0312] However, in the actual process of detecting fault arcs, the switching frequency and its harmonics on the DC bus can affect the stability of the overall AFCI control and the total harmonic distortion (THD) of the current. It can even cause the solar panel current to oscillate, resulting in false alarms or missed alarms in fault arc detection.

[0313] To suppress the impact of DC bus switching frequency and its harmonic fluctuations on fault arc detection results, the method of reducing the overall gain is usually adopted. However, this reduces the ability of AFCI to identify real arc characteristic signals. Therefore, existing methods still have the drawback of limited accuracy in fault arc detection.

[0314] In related technologies, the energy of switching frequency and its harmonics fluctuations, or total harmonic distortion noise of the current, 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 includes characteristic noises of the machine such as switching frequency noise and its harmonics noise, or total harmonic distortion noise of the current, the overall gain can only be reduced. However, reducing the overall gain will reduce the fault detection device's ability to identify real arc characteristic signals.

[0315] Therefore, DC buses often employ a large number of electrolytic capacitors, film capacitors, and inductors to suppress ripple components and improve current quality. However, these components are not only large and expensive, but also have their own drawbacks. Electrolytic capacitors suffer from electrolyte evaporation, increased internal resistance, and shorter lifespans compared to other components. Inductors experience inductance degradation under high current conditions, significantly reducing their filtering effect. Film capacitors are bulky and have relatively low inductance.

[0316] 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.

[0317] The fault detection device, method, and photovoltaic power generation system provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0318] As shown in Figure 22, the fault detection device 100 includes a sampling module 110, a signal processing module 120, and a control module 130.

[0319] In actual implementation, the fault detection device 100 may mainly include the following components: sampling module 110, signal processing module 120, and control module 130.

[0320] 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, then processes it through the signal processing module 120, and finally sends it to the control module 130.

[0321] The sampling module 110 is used to sample the output signal of the output cable of the solar panel to obtain the sampling signal; the output signal includes the current noise floor ripple signal and the fault ripple signal.

[0322] It should be noted that the output signal of the solar panel's output cable can be a current ripple signal. Under normal circumstances, the output signal of the solar panel's output cable is a current noise floor ripple signal. Here, noise floor refers to the internal noise of the inverter when the photovoltaic power generation system is functioning correctly (generally the solar panel). The "inverter" mentioned above refers to the inverter itself. Noise floor can include internal switching frequency noise, power frequency noise, and external conducted and radiated noise, etc.

[0323] When a solar panel malfunctions (e.g., arcing), the output current of its output cables will fluctuate drastically. By sampling the current ripple signal from the solar panel's output cables, it's possible to monitor whether the inverter's current is stable and normal, thus determining whether a fault has occurred in the photovoltaic power generation system. Therefore, when the solar panel is functioning correctly, its output current ripple signal is the current noise floor ripple signal; when the solar panel malfunctions, its output current ripple signal includes not only the aforementioned current noise floor ripple signal but also the current ripple signal generated by the fault. The current ripple signal generated by the fault can be called the fault ripple signal.

[0324] Since arcing is a common type of fault in solar panels, the following embodiments are described using arcing as the target fault. However, those skilled in the art will understand that the target fault may include other types of faults.

[0325] In actual implementation, the sampling module 110 may include an acquisition unit and a sampling unit.

[0326] The acquisition unit can be used to acquire the current ripple signal output by the solar panel through its output cable. It is understood that, in the absence of a fault in the solar panel, the fault ripple signal in the output signal of the solar panel's output cable can be considered zero. In some embodiments, the acquisition unit may include a current transformer or a current sensor. The output cable of the solar panel is the PV cable between the solar panel and the inverter.

[0327] A sampling unit is used to sample the signal acquired by the acquisition unit. The signal obtained by sampling the signal acquired by the acquisition unit can be called a sampled signal. In some embodiments, the sampling unit may include a sampling resistor.

[0328] The signal processing module 120 is used to perform notch filtering and conditioning on the sampled signal, filter out the target frequency band signal in the sampled signal and amplify the signal of other frequency bands to obtain the characteristic signal; the target frequency band is the frequency band that overlaps with the noise signal generated by the target fault.

[0329] In actual execution, the sampled signal obtained by the sampling module 110 can be input to the signal processing module 120, where it undergoes notch filtering and conditioning to obtain the characteristic signal. The purpose of the notch filtering and conditioning processing of the sampled signal by the signal processing module 120 is to retain the original fault ripple signal, suppress the interference of characteristic noise signals in the inverter's internal noise signal on fault detection, and fully amplify the fault ripple signal.

[0330] It should be noted that characteristic noise signals can include switching frequency noise and its harmonic fluctuation noise from the inverter's internal noise signals, as well as total harmonic distortion (THD) noise. Generally, the frequency bands of these characteristic noise signals largely overlap with the frequency bands of noise signals generated by the target fault. The frequency band where these two types of noise signals overlap is the target frequency band. That is, both characteristic noise signals and noise signals generated by the target fault exist in the target frequency band; in other frequency bands besides the target frequency band, characteristic noise signals are basically absent, but noise signals generated by the target fault are present.

[0331] The specific structure of the signal processing module 120 is not limited in this embodiment. Any circuit structure can be used that can achieve the aforementioned functions of preserving the original fault ripple signal, suppressing the interference of characteristic noise signals in the inverter's internal noise signal on fault detection, and fully amplifying the fault ripple signal. In some embodiments, the signal processing module 120 may include multiple filters.

[0332] The control module 130 is used to detect the presence of faults based on characteristic signals, a pre-established background noise model, and a fault signal model.

[0333] In actual execution, the characteristic signals obtained by the signal processing module 120 can be input into the control module 130, which then determines whether a fault exists based on the aforementioned characteristic signals.

[0334] In some embodiments, the control module 130 may include any type of control chip, such as a microcontroller or MCU.

[0335] In some embodiments, the control module 130 can compare the feature signal with a pre-established background noise model and a fault signal model to determine whether the feature 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 a target fault exists.

[0336] It is understandable that if the characteristic signal matches the characteristics of the background noise signal but not 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; while if the characteristic signal does not match the characteristics of the background noise signal but matches the characteristics of the noise signal generated by the target fault, it can be determined that the target fault exists or has occurred.

[0337] In some embodiments, the noise floor model may include noise floor data for all operating conditions within the target frequency band, based on notch filter sampling.

[0338] In some embodiments, the fault signal model may include fault ripple signal data collected at least one length of the output cable of the solar cell within the target frequency band.

[0339] It should be noted that in practical applications, the length of the output cable of a solar cell can vary and is uncontrollable. By collecting fault ripple signal data in advance at different lengths of the solar cell's output cable, the richness of the fault signal model data can be expanded to cope with detection under various conditions and cover various real-world scenarios.

[0340] In some embodiments, as shown in FIG23, the working process of the fault detection device 100 may include the following steps:

[0341] Step 210: Collect current data.

[0342] The current ripple signal output by the solar panel through its output cable can be collected using a current transformer or a current sensor.

[0343] Step 220: Sample the resistor.

[0344] The output signal of the solar panel's output cable, which is collected by a current transformer or current sensor, can be sampled using a sampling resistor to obtain a sampled signal.

[0345] Step 230: Notch filtering and filtering.

[0346] The signal processing module 120 performs notch filtering and filtering on the sampled signal to obtain the characteristic signal.

[0347] Step 240: Determine if the AD port has reached saturation.

[0348] The system determines whether the AD port of control module 130 has reached saturation. If the AD port is saturated, the fault detection function of control module 130 is disabled; if the AD port is not saturated, the fault detection function of control module 130 is effective and can determine whether a fault exists. The AD port is the sampling port of control module 130.

[0349] Step 250, troubleshooting.

[0350] If the AD port of control module 130 is not saturated, control module 130 can perform fault handling based on characteristic signals. Fault handling by control module 130 may include: first determining whether a fault exists; and if a fault exists, eliminating the fault.

[0351] In some embodiments, the fault detection device 100 can be as shown in FIG24. The output signal of the solar panel can be input to the control module 130 after passing through a current sensor, a sampling resistor, and a signal processing module 120 composed of multiple filters in sequence; after obtaining the fault detection result based on the input signal, the control module 130 can control the inverter based on the fault detection result.

[0352] It should be noted that, as shown in Figure 25, the longer the output cable of a solar panel, the weaker the characteristic noise signal. The weaker the signal, the more difficult it is to sample and condition. Therefore, the length of the solar panel's output cable generally limits the accuracy of fault detection devices.

[0353] Furthermore, the input voltage range of the sampling port of the control module 130 has an upper limit and cannot exceed the power supply voltage of the control module 130. Therefore, the total amplification factor of the sampled signal by the signal processing module 120 is limited. Once the upper limit is exceeded, the sampling port will saturate, the fault detection function of the control module 130 will fail, and it will be impossible to determine whether a fault exists.

[0354] For example, as shown in Figure 26, under certain circumstances, the characteristic noises inside the machine, such as switching frequency noise, its harmonic noise, and total harmonic distortion noise of the current, are concentrated between 15kHz and 30kHz. This results in a higher power density of the characteristic noise signal within this frequency range, and a higher voltage amplitude of the characteristic signal obtained by the signal processing module 120, which makes it easier to saturate the sampling port of the control module 130.

[0355] To ensure the fault detection device functions properly and guarantees accuracy, it is crucial that the characteristic signals processed by the signal processing module 120 do not cause saturation of the sampling port of the control module 130 under any fault-free condition. Saturation of the sampling port of the control module 130 would lead to false alarms from the fault detection device.

[0356] Therefore, under the same gain of K1, in the worst-case scenario, the characteristic noise signal before notch filtering will cause sampling port saturation between 20kHz and 25kHz. Consequently, the value of K1 must be reduced (e.g., to 0.5*K1) to ensure that conditioning the sampled signal will not cause sampling port saturation of the control module 130 under any fault-free condition. In this case, to ensure that the conditioning result between 20kHz and 25kHz meets the requirements, the sampling conditioning performance of other frequency bands will be sacrificed.

[0357] At the same gain of K1, notch filtering is applied to a frequency band with a center frequency of 22.5kHz and a bandwidth of 15kHz (this frequency band is the target frequency band). The characteristic noise signal after notch filtering will not cause sampling port saturation at a gain of K1, and its performance below 15kHz and above 30kHz is the same as the characteristic noise signal before notch filtering amplified by K1, thus maximizing the performance of these two frequency bands. It can be understood that the frequency bands below 15kHz and above 30kHz are the other frequency bands mentioned above.

[0358] Therefore, it can be seen that notch filtering of the target frequency band containing characteristic noise signals such as switching frequency noise, its harmonic noise, and total harmonic distortion noise of current can prevent the sampling port from saturating in the frequency domain or time domain even at a greater amplification factor.

[0359] In related technologies, the sampled signal is amplified as a whole. However, due to the limitations of the input voltage of the sampling port of the control module 130 and the high energy of the characteristic noise signal, the overall gain is limited. In the embodiment of this application, after filtering out 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 signals of the other frequency bands mentioned above is greater (compared to related technologies), making it easier to extract the characteristics of the noise signal generated by the target fault.

[0360] Furthermore, notch filtering of the target frequency band will not affect the sampling and conditioning of other frequency band components in the noise signal generated by the target fault.

[0361] Therefore, in this embodiment of the application, by performing notch filtering and conditioning on the sampled signal through the signal processing module 120, the signal of the target frequency band in the sampled signal is filtered out and the signal of other frequency bands is amplified. This can enable the other frequency band parts in the noise signal generated by the target fault to obtain greater gain, thereby improving the sampling accuracy, enriching the model data, and optimizing the overall performance.

[0362] For example, as shown in Figure 27, under a certain K-fold gain, the sampled signal before notch filtering can cause the sampling port to saturate under some operating conditions. However, the sampled signal after notch filtering, under K-fold gain, has a large margin of safety from causing the sampling port to saturate under any operating condition.

[0363] It should be noted that the arc fault characteristic signal in Figure 27 refers to the fault ripple signal when the target fault is a telephone fault.

[0364] By rationally designing the signal processing module 120, the characteristic noises such as the switching frequency noise, harmonic noise, and total harmonic distortion noise of the inverter's switching transistors are separated from the target identification frequency band (which can be other aforementioned frequency bands) of the fault detection device. The energy of the noise signal that is irrelevant to fault detection is reduced, and the overall gain of the signal in the target identification frequency band is maximized. This results in a clearer, more accurate, and more effective background noise model and fault signal model over a longer cable (referring to the output cable of the solar panel), thereby improving the overall gain of the fault detection device and enhancing its overall identification capability.

[0365] In some embodiments, any one of the sampling module 110, signal processing module 120, and control module 130, as well as any one of the functional modules included in the sampling module 110, signal processing module 120, and control module 130, can be disposed inside the inverter housing or outside the inverter housing, as long as it satisfies the inventive concept of the embodiments of this application.

[0366] According to the fault detection device provided in the embodiments of this application, the signal processing module combines sampling notch processing and conditioning processing to filter out signals in the target frequency band of the sampled signal and amplify signals in other frequency bands. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0367] In some embodiments, the fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

[0368] In actual implementation, the fault ripple signal can include the arc fault ripple signal. The arc fault ripple signal refers to the current ripple signal generated by the arc fault. Correspondingly, the target fault can include the arc fault. Therefore, the fault detection device 100 can achieve more accurate detection of arc faults.

[0369] According to the fault detection device provided in the embodiments of this application, the signal processing module combines sampling notch processing and conditioning processing to filter out signals in the target frequency band of the sampled signal and amplify signals in other frequency bands. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on arc fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of arc fault detection, reduce false alarms, and improve the accuracy of arc fault detection.

[0370] In some embodiments, as shown in FIG28, the signal processing module 120 may include:

[0371] The notch filter unit 710 is used to filter out signals in the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain the first-level signal;

[0372] The conditioning unit 720 is used to amplify the first-stage signal to obtain the second-stage signal;

[0373] The filtering unit 730 is used to filter the second-stage signal to obtain the characteristic signal.

[0374] In actual execution, the original sampled signal to be conditioned (i.e. the sampled signal output by the sampling module 110) is processed by the notch filter unit 710, the conditioning unit 720 and the filtering unit 730 in sequence. It can be conditioned to retain the original fault ripple signal, suppress the interference of characteristic noise signals in the inverter's internal noise signal on fault detection, and make the fault ripple signal fully amplified.

[0375] In some embodiments, under certain adverse operating conditions, the amplitude of the sampling voltage corresponding to the switching frequency of the inverter's BOOST circuit in the original sampled signal to be conditioned may 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 filter unit 710 before the noise signal generated by the target fault that needs to be extracted and amplified can be amplified in the second stage using the conditioning unit 720.

[0376] It should be noted that the notch filter unit 710 filters out the target frequency band signal 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.

[0377] The filtering unit 730 can further filter the second-stage signal to further realize the filtering and conditioning function and obtain the conditioned sampled signal, i.e. the characteristic signal.

[0378] According to the fault detection device provided by the embodiments of the present application, the signal in the target frequency band is filtered by a notch unit to reduce the amplitude of the sampling voltage of the signal, and a first-stage signal is obtained. And the first-stage signal is amplified by a conditioning unit to obtain a second-stage signal, which can suppress characteristic noises such as switching frequency noise, its harmonic frequency noise, or current total harmonic distortion noise, can reduce the interference of characteristic noises such as switching frequency noise, its harmonic frequency noise, or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall recognition ability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0379] In some embodiments, the notch unit 710 includes at least one notch circuit.

[0380] In actual implementation, the notch unit 710 may include one or more notch circuits. Each notch circuit can serve as a notch filter.

[0381] 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.

[0382] In some embodiments, the notch unit 710 can separately set a notch circuit, and the notch circuit adopts a structure in which 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 (f1 < f2).

[0383] In some embodiments, the notch unit 710 can also set an in-phase proportional operation circuit after the aforementioned notch circuit, so as to obtain an active band-stop filter circuit

[0384] In some embodiments, the center frequency and bandwidth of each notch circuit can be determined in advance by calculation to reduce the influence of characteristic noises such as switching frequency noise, its harmonic frequency noise, and current total harmonic distortion noise on fault detection, and establish a better or even optimal background noise model and fault signal model, etc.

[0385] In some embodiments, in the photovoltaic field, the above-mentioned characteristic noises are mainly determined by the internal switching frequency of the machine, including the switching frequency of the BOOST circuit of the inverter, the INV switching frequency, and the switching frequency of the auxiliary source, 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.

[0386] Given the switching frequencies of the inverter's BOOST circuit, INV circuit, and auxiliary source circuit, the aforementioned switching frequencies can be used as the center frequencies of each notch filter circuit, thereby calculating the bandwidth.

[0387] According to the fault detection device provided in the embodiments of this application, by employing at least one notch filter circuit, signals in the target frequency band can be filtered out to reduce the amplitude of the signal sampling voltage. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0388] In some embodiments, the notch circuit is a Bainter notch filter, a T-type notch filter, a Type II notch filter, an MFB multiple feedback notch filter, or an RLC notch filter.

[0389] In actual implementation, any notch circuit included in the notch unit 710 can be a Bainter notch filter, a T-type notch filter, a Type II notch filter, or an RLC notch filter. The T-type notch filter can include a passive T-type notch filter and an active T-type notch filter.

[0390] In some embodiments, FIG29 shows the case where the notch unit 710 uses a Bainter notch filter.

[0391] In some embodiments, the notch filter unit 710 may include any notch filter circuit, such as a T-type notch filter circuit, a type II notch filter circuit, or an RLC notch filter.

[0392] Taking the double-T notch filter circuit as an example, its basic structure consists of a series capacitor and an inductor and a parallel capacitor. It can filter out single-frequency interference signals and is suitable for high-frequency loop interference suppression.

[0393] Figure 30 shows a typical RC dual-T notch filter circuit, which consists of an RC passive low-pass filter and an RC passive high-pass filter connected in parallel.

[0394] The parameter values ​​of each component in the double-T notch filter circuit can satisfy the following relationships: C1=C2=C,C3=2C; R1=R2=R,R3=1 / 2R.

[0395] This circuit satisfies the following circuit equation:

[0396] The above formula can be used to obtain...

[0397] It can be seen that the above equation satisfies the characteristics of a second-order system, therefore we can obtain...

[0398] Where ω0 is the center frequency, 2β is the bandwidth, and Q is the quality factor.

[0399] In some embodiments, any notch circuit included in the notch unit 710 may also use a parallel bandpass filter or a series bandpass filter. A parallel bandpass filter can simultaneously filter out signals below and above a certain frequency range, while a series bandpass filter can attenuate noise signals within a specific frequency range. Setting the frequency band according to filtering out characteristic noise such as the switching frequency noise of the switching transistor and its harmonic noise or the total harmonic distortion noise of the current is sufficient to satisfy the inventive concept of this application.

[0400] In some embodiments, any notch circuit included in the notch unit 710 can be directly set in the main power circuit using an inductor and a capacitor in conjunction with the impedance of the downstream power line to establish the notch circuit. Alternatively, it can be set in the signal processing module 120, where the notch unit 710, conditioning unit 720, and filtering unit 730 on the weak current side complete the preset notch and conditioning filtering target after sampling by the current transformer / sensor unit and sampling resistor.

[0401] The signal processing module 120 is configured to have a smaller gain in the frequency band where the switching frequency noise of the switching transistor and its harmonic noise or the total harmonic distortion noise of the current are located, and a larger gain in the target identification frequency band, which satisfies the inventive concept of the embodiments of this application.

[0402] According to the fault detection device provided in the embodiments of this application, the notch circuit is a Bainter notch filter, a T-type notch filter, a Type II notch filter, an MFB multiple feedback notch filter, or an RLC notch filter. It can filter out signals in the target frequency band, thereby reducing the amplitude of the signal sampling voltage. It can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, thereby reducing the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection. This improves the overall gain of the fault detection device, enhances the overall identification capability of fault detection, reduces false alarms, and improves the accuracy of fault detection.

[0403] In some embodiments, the notch circuit includes a high-pass filter.

[0404] In actual implementation, any notch circuit included in the notch unit 710 may include a high-pass filter.

[0405] When the target frequency band is low (i.e., all target frequencies are below the frequency threshold), the notch filter circuit can include a high-pass filter, which can then filter out signals from the target frequency band. This low-frequency target band can fall below the -3dB point of the high-pass filter. Therefore, essentially using a high-pass filter can achieve the notch filter concept of this application and achieve the same effect.

[0406] According to the fault detection device provided in the embodiments of this application, when the target frequency band is low, a high-pass filter is used to filter out the signal of the target frequency band to reduce the amplitude of the sampling voltage of the signal. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0407] In some embodiments, the notch filter unit 710 includes: a first operational amplifier.

[0408] In actual implementation, the notch filter unit 710 may also include a first operational amplifier.

[0409] Generally, passive double-T networks have low input impedance and high output impedance, making them susceptible to the influence of the preceding and following stages in the circuit. Their characteristics are not very good, and their Q value is low. They can only achieve good attenuation characteristics when they are far from the resonant frequency ω0.

[0410] In this embodiment, the notch filter unit 710 is directly designed after the current transformer / current sensor, which can avoid the influence of coupling with the main power circuit. It can also set the first operational amplifier to change the voltage division coefficient and significantly change the Q value.

[0411] The output signal of the notch filter unit 710 is output through a voltage output device with a gain of 1 and fed back to the dual-T network to form a bootstrap. The Q value when the input signal attenuation is about 0.3 can reach more than 50, which greatly enhances the filtering effect.

[0412] According to the fault detection device provided in the embodiments of this application, the filtering effect of the notch filter unit can be greatly enhanced by including a first operational amplifier.

[0413] In actual implementation, the conditioning unit 720 includes: a second operational amplifier.

[0414] In actual implementation, the conditioning unit 720 may include a second operational amplifier. The filtering unit 730 may include a third operational amplifier.

[0415] The notch filter unit 710, conditioning unit 720, and filter unit 730 all essentially function as filters. Therefore, the conditioning unit 720 and filter unit 730 following the notch filter unit 710 can also avoid the effects of coupling with the main power circuit. The conditioning unit 720 or filter unit 730 can also be configured with an operational amplifier to change the voltage division coefficient, thus significantly changing the Q value.

[0416] When the output signal of the conditioning unit 720 or the filtering unit 730 is output through a voltage output device with a gain of 1 and fed back to the dual-T network to form a bootstrap, the Q value when the input signal attenuation is about 0.3 can reach more than 50, which greatly enhances the filtering effect.

[0417] According to the fault detection device provided in the embodiments of this application, the conditioning unit, including a second operational amplifier, can greatly enhance the filtering effect of the notch filter unit.

[0418] In some embodiments, the control module 130 includes:

[0419] The matching unit is used to match the features of the feature signal with the background noise model and the fault signal model, respectively.

[0420] The control unit is used to determine the occurrence of a target fault when the characteristics of the characteristic signal do not match the background noise model but match the fault signal model, and to control the inverter to stop working and / or control the switching module used to connect the solar panels to the inverter to turn off.

[0421] In actual operation, the control module 130 may include a matching unit and a control unit.

[0422] The matching unit can match the features of the feature signal with the background noise model and the fault signal model respectively to determine whether the features of the feature signal match the background noise model and whether the features of the feature signal match the fault signal model.

[0423] When the characteristics of the characteristic signal do not match the background noise model but match the fault signal model, the control unit can determine that a target fault has occurred, and then the inverter stops working and / or controls the switching module used to connect the solar panels to the inverter to shut down.

[0424] In some embodiments, when the solar panel outputs an arc fault ripple signal, the fault ripple signal generated by the arc is 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. Based on the criteria, it is determined that an arc fault has occurred.

[0425] Once the control unit detects an arcing fault, it can issue a command to stop the inverter or open the trip switch, ultimately extinguishing the arc. The switching module used to connect the solar panels and the inverter may include a trip switch.

[0426] According to the fault detection device provided in the embodiments of this application, the matching unit matches the features of the characteristic signal with the background noise model and the fault signal model respectively. When the features of the characteristic signal do not match the background noise model but match the fault signal model, the control unit determines that a target fault has occurred, controls the inverter to stop working and / or controls the switching module used to connect the solar panel and the inverter to turn off. This can handle the target fault in a timely manner, avoid damage to the inverter and solar panel, and extend the service life of the inverter and solar panel.

[0427] This application also provides a fault detection method. As shown in FIG31, the method includes: step 1010, step 1020 and step 1030.

[0428] Step 1010: Sample the output signal of the output cable of the solar panel to obtain the sampled signal; the output signal includes the current noise floor ripple signal and the fault ripple signal;

[0429] Step 1020: Perform notch filtering and conditioning on the sampled signal to filter out the target frequency band 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 and the noise signal generated by the target fault coincide.

[0430] Step 1030: Based on the characteristic signal, the pre-established background noise model and fault signal model, detect whether a fault exists.

[0431] In actual implementation, the entity executing this fault detection method can be any of the fault detection devices provided in the foregoing embodiments. The process by which the fault detection device executes the fault detection method can be found in the foregoing embodiments, and will not be repeated here.

[0432] According to the fault detection method provided in the embodiments of this application, by combining sampling notch processing and conditioning processing, the target frequency band signal in the sampled signal is filtered out and the signals of other frequency bands are amplified. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0433] In some embodiments, the fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

[0434] In some embodiments, notch filtering and conditioning are performed on the sampled signal to filter out signals in the target frequency band and amplify signals in other frequency bands to obtain a characteristic signal, including:

[0435] Filter out signals in the target frequency band to reduce the amplitude of the signal sampling voltage and obtain the first-level signal;

[0436] The first-stage signal is amplified to obtain the second-stage signal;

[0437] The second-level signal is filtered to obtain the characteristic signal.

[0438] In some embodiments, the detection of the presence of a fault arc is based on characteristic signals, a pre-established background noise model, and a fault signal model, including:

[0439] When the characteristics of the feature signal do not match the background noise model but match the fault signal model, the target fault is determined to have occurred.

[0440] In some embodiments, after determining that a target fault has occurred, the method further includes:

[0441] Control the inverter to stop working and / or control the switching module used to connect the solar panels to the inverter to shut down.

[0442] This application also provides a photovoltaic power generation system. As shown in Figure 22, the photovoltaic power generation system includes: a solar panel 200, an inverter 300, and a fault detection device 100.

[0443] In actual implementation, the solar panel 200 can be electrically connected to the input terminal of the fault detection device 100. The output terminal of the fault detection device 100 can be electrically connected to the inverter 300. The fault detection device 100 can be any of the fault detection devices provided in the foregoing embodiments.

[0444] According to the photovoltaic power generation system provided in the embodiments of this application, by combining sampling notch processing and conditioning processing, the target frequency band signal in the sampled signal is filtered out and the signal of other frequency bands is amplified. This can suppress characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise, reduce the interference of characteristic noises such as switching frequency noise and its harmonic noise or current total harmonic distortion noise on fault detection, improve the overall gain of the fault detection device, enhance the overall identification capability of fault detection, reduce false alarms, and improve the accuracy of fault detection.

[0445] In some embodiments, as shown in FIG21, this application embodiment also provides an electronic device 2100, including a processor 2101, a memory 2102, and a computer program stored in the memory 2102 and executable on the processor 2101. When the program is executed by the processor 2101, it implements the various processes of the above-described gain adjustment method embodiment or fault detection method embodiment and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0446] It should be noted that the electronic devices in the embodiments of this application include the mobile electronic devices and non-mobile electronic devices described above.

[0447] This application also provides a non-transitory computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the various processes of the above-described gain adjustment method embodiment or fault detection method embodiment and achieves the same technical effect. To avoid repetition, it will not be described again here.

[0448] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0449] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described gain adjustment method.

[0450] The processor is the processor in the electronic device described in the above embodiments. The readable storage medium includes computer-readable storage media, such as computer read-only memory (ROM), random access memory (RAM), magnetic disk, or optical disk.

[0451] This application embodiment also provides a chip, which includes a processor and a communication interface. The communication interface is coupled to the processor. The processor is used to run programs or instructions to implement the various processes of the above-described gain adjustment method embodiment or fault detection method embodiment, and can achieve the same technical effect. To avoid repetition, it will not be described again here.

[0452] It should be understood that the chip mentioned in the embodiments of this application may also be referred to as a system-on-a-chip, system chip, chip system, or system-on-a-chip, etc.

[0453] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0454] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0455] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

[0456] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0457] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A gain adjustment method for an AFCI conditioning circuit, the AFCI conditioning circuit being used to provide multiple different gains, the input port of the AFCI conditioning circuit being used to connect to a solar panel; characterized in that, The method includes: By adjusting the gain of the AFCI conditioning circuit, a first output value corresponding to the AFCI conditioning circuit under various different gains is obtained; the first output value is used to characterize the AFCI conditioning circuit characteristics corresponding to the inverter corresponding to the solar panel under different operating parameters, and / or the solar panel and the inverter under different cable lengths. Based on each of the first output values, the amplitude-frequency characteristic curve corresponding to the solar panel is obtained by fitting. Based on the amplitude-frequency response curve, the target gain adjustment strategy is determined.

2. The gain adjustment method according to claim 1, characterized in that, The step of adjusting the gain of the AFCI conditioning circuit to obtain the first output value of the AFCI conditioning circuit under various different gains includes: When the AFCI conditioning circuit operates based on the target gain, a second output value of the AFCI conditioning circuit is obtained to characterize the operation of the solar panel under the target operating scenario, and the second output value is determined as the first output value of the solar panel under the target gain. The target operating scenario is the scenario where the cable length is the shortest and the operating parameters are the worst.

3. The gain adjustment method according to claim 2, characterized in that, When the AFCI conditioning circuit operates based on the target gain, the acquisition of a second output value of the AFCI conditioning circuit, used to characterize the solar panel operating under the target operating scenario, includes: When the AFCI conditioning circuit operates based on the target gain, a target signal is injected into the target position corresponding to the solar panel to obtain the second output value output by the AFCI conditioning circuit. The target signal is adjusted until the second output value reaches the critical output value corresponding to the target gain of the solar panel, and the critical output value is determined as the second output value.

4. The gain adjustment method according to any one of claims 1-3, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: Based on the values ​​of the characteristic frequency points in the amplitude-frequency response curve, multiple static gain levels are determined. Gain adjustment is performed based on the multiple static gain levels.

5. The gain adjustment method according to claim 4, characterized in that, The gain adjustment based on the multiple static gain levels includes: The highest level among the multiple static gain levels is determined as the initial level for gain adjustment; When the AFCI conditioning circuit operates based on the gain corresponding to the initial gear, the third output value of the AFCI conditioning circuit is obtained. If the third output value is less than or equal to the threshold gear, the initial gear remains unchanged; If the third output value is greater than the threshold level, the initial level is reduced.

6. The gain adjustment method according to claim 4, characterized in that, The gain adjustment based on the multiple static gain levels includes: Based on the ripple signal with a specific voltage and frequency, the actual cable length corresponding to the solar panel is determined by comparing the frequency response with the amplitude-frequency characteristic curve. Based on the actual cable length, an initial static gain level is determined from the plurality of static gain levels; Gain adjustment is performed based on the initial static setting.

7. The gain adjustment method according to any one of claims 1-6, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: Based on the multiple actual output values ​​of the AFCI conditioning circuit under the current static gain setting during the operation of the solar panel, the risk status is determined; the risk status includes no risk or risk present. Gain adjustment is performed based on the risk status and the current static gain level.

8. The gain adjustment method according to claim 7, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: Under the aforementioned risk-free conditions, the current static gain level remains unchanged; If there is a risk and the current static gain level is not the lowest level, the current static gain level shall be lowered. If there is a risk and the current static gain level is the lowest level, the inverter corresponding to the solar panel will be shut down.

9. The gain adjustment method according to claim 7, characterized in that, During the operation of the solar panel, the AFCI conditioning circuit determines the risk status based on multiple actual output values ​​corresponding to the current static gain level, including: If the number of actual output values ​​exceeding the saturation threshold exceeds the target proportion, the risk status is determined to be risky. If the number of actual output values ​​exceeding the saturation threshold does not exceed the target proportion, the risk status is determined to be risk-free.

10. The gain adjustment method according to any one of claims 1-9, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: If it is determined that all characteristic frequency points are within the target range based on the amplitude-frequency characteristic curve, the target gain adjustment strategy is determined based on the amplitude-frequency characteristic curve. If, based on the amplitude-frequency characteristic curve, it is determined that at least one characteristic frequency point is not within the target range, the function of the solar panel or the AFCI conditioning circuit is abnormal.

11. The gain adjustment method according to any one of claims 1-10, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: The current ripple signal is acquired when the control bus voltage is higher than the input voltage and the difference is not greater than the first threshold. If no arc-like noise is detected after processing the current ripple signal, the target gain adjustment strategy is determined based on the amplitude-frequency characteristic curve. If the current ripple signal is processed and arc-like noise is detected, it is determined that the AFCI detection link is malfunctioning.

12. The gain adjustment method according to any one of claims 1-11, characterized in that, The step of determining the target gain adjustment strategy based on the amplitude-frequency response curve includes: When the control bus voltage is higher than the input voltage and the difference is greater than the second threshold, the actual output value of the AFCI conditioning circuit is obtained. When the actual output value is not saturated, the target gain adjustment strategy is determined based on the amplitude-frequency characteristic curve; If the actual output value is saturated, it is determined that the AFCI detection link function is abnormal.

13. A gain adjustment device for an AFCI conditioning circuit, the AFCI conditioning circuit being used to provide multiple different gains, the input port of the AFCI conditioning circuit being used to connect to a solar panel; characterized in that, The device includes: The first processing module is used to obtain a first output value of the AFCI conditioning circuit under various different gains by adjusting the gain of the AFCI conditioning circuit; the first output value is used to characterize the AFCI conditioning circuit characteristics of the inverter corresponding to the solar panel under different operating parameters, and / or the solar panel and the inverter under different cable lengths. The second processing module is used to fit the amplitude-frequency characteristic curve corresponding to the solar panel based on each of the first output values; The third processing module is used to determine the target gain adjustment strategy based on the amplitude-frequency characteristic curve.

14. An AFCI conditioning circuit, characterized in that, include: A fault detection device, wherein the input port of the fault detection device is used to connect to a solar panel, and the fault detection device is used to output a first output value corresponding to the solar panel under various different gains by adjusting the gain of the fault detection device; The AFCI intelligent module is connected to the output port of the fault detection device and is used to fit the amplitude-frequency characteristic curve corresponding to the solar panel based on each of the first output values; and to determine the target gain adjustment strategy corresponding to the solar panel based on the amplitude-frequency characteristic curve.

15. The AFCI conditioning circuit according to claim 14, characterized in that, The fault detection device includes: The sampling module is used to sample the output signal of the output cable of the solar panel to obtain the sampled signal; the output signal includes the current noise floor ripple signal and the fault ripple signal; The signal processing module is used to perform notch filtering and conditioning on the sampled signal, filter out the signal in the target frequency band and amplify the signal in other frequency bands to obtain the characteristic signal; the target frequency band is the frequency band where the characteristic noise signal and the noise signal generated by the target fault coincide. 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.

16. The AFCI conditioning circuit according to claim 15, characterized in that, The fault ripple signal includes an arc fault ripple signal, and the target fault includes an arc fault.

17. The AFCI conditioning circuit according to claim 15, characterized in that, The signal processing module includes: A notch filter unit is used to filter out signals in the target frequency band to reduce the amplitude of the sampling voltage of the signal and obtain the first-level signal. The conditioning unit is used to amplify the first-stage signal to obtain the second-stage signal; The filtering unit is used to filter the second-stage signal to obtain the feature signal.

18. The AFCI conditioning circuit according to claim 17, characterized in that, The notch filter unit includes at least one notch filter circuit.

19. The AFCI conditioning circuit according to claim 18, characterized in that, The notch circuit is a Bainter notch filter, a T-type notch filter, a Type II notch filter, or an RLC notch filter.

20. The AFCI conditioning circuit according to claim 18, characterized in that, The notch circuit includes a high-pass filter.

21. The AFCI conditioning circuit according to any one of claims 15 to 20, characterized in that, The notch filter unit includes: a first operational amplifier.

22. The AFCI conditioning circuit according to claim 17, characterized in that, The conditioning unit includes a second operational amplifier.

23. The AFCI conditioning circuit according to claim 15, characterized in that, The control module includes: A matching unit is used to match the features of the feature signal with the background noise model and the fault signal model, respectively. The control unit is configured to determine that the target fault has occurred when the characteristics of the characteristic signal do not match the background noise model but match the fault signal model, and to control the inverter to stop working and / or control the switching module used to connect the solar panel and the inverter to turn off.

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