Arc detection circuit and arc detection system

Abstract

The utility model discloses an arc detection circuit and an arc detection system of a photovoltaic inverter, and belongs to the technical field of arc fault detection. The utility model provides an arc detection circuit for a photovoltaic inverter, and the circuit comprises a filter circuit which accesses an arc signal for detecting the photovoltaic inverter, carries out the filtering processing of the arc signal based on a target passband frequency, and provides a first signal, and the target passband frequency is an effective frequency band of the arc signal; the trap circuit is connected with the output end of the filter circuit and is used for carrying out trap processing on the filtered arc signal based on a target band elimination frequency and providing a second signal, and the target band elimination frequency is the working frequency band of the photovoltaic inverter; and the detection unit is connected with the output end of the trap circuit and judges whether an arc fault exists or not according to the second signal. According to the arc detection circuit of the photovoltaic inverter, the phenomena of missing report and false report of arc detection caused by noise generated in the working process of the photovoltaic inverter can be reduced, and the accuracy of arc detection is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of arc fault detection, and particularly relates to an arc detection circuit and an arc detection system. BACKGROUND

[0002] With the development of photovoltaic power generation technology, the number of solar devices is increasing, and the number of various connection points is also increasing, and the risk of direct current arc fault is also increasing. In order to prevent the occurrence of electric shock or fire hazards, it is necessary to add an arc fault protection circuit in the power system, but the accuracy and stability of the arc fault protection circuit in the power system are difficult to meet the requirements. CONTENT OF THE UTILITY MODEL

[0003] The application aims to at least solve one of the technical problems existing in the prior art. To this end, the application provides an arc detection circuit and an arc detection system, which reduces the phenomenon of false negatives and false positives caused by noise generated during the operation of a photovoltaic inverter, and improves the accuracy of arc detection.

[0004] In a first aspect, the application provides an arc detection circuit of a photovoltaic inverter, which comprises:

[0005] a filter circuit configured to access an arc signal detected by the photovoltaic inverter, and to perform filter processing on the arc signal based on a target passband frequency, to provide a first signal after filtering, the target passband frequency being an effective frequency band of the arc signal;

[0006] a notch circuit connected to the output end of the filter circuit, and configured to perform notch processing on the filtered arc signal based on a target stopband frequency, to provide a second signal after notch processing, the target stopband frequency being an operating frequency band of the photovoltaic inverter;

[0007] a detection unit connected to the output end of the notch circuit, and configured to determine whether an arc fault exists according to the second signal.

[0008] According to the arc detection circuit of the photovoltaic inverter of the application, the filter circuit can perform filter processing on the arc signal in the effective frequency band of the arc signal, the detection range is large, the notch circuit can limit the operating frequency band of the photovoltaic inverter to the stopband, to reduce the phenomenon of false negatives and false positives caused by noise generated during the operation of the photovoltaic inverter, and improve the accuracy of arc detection.

[0009] According to one embodiment of the application, the filter circuit comprises two cascaded stages of multi-feedback filter circuits, the input end of the first stage of multi-feedback filter circuits is used to access the arc signal, and the output end of the second stage of multi-feedback filter circuits is electrically connected to the input end of the notch circuit.

[0010] According to one embodiment of the present application, the multi-feedback filter circuit comprises:

[0011] a first resistor, a first end of the first resistor being an input end of the multi-feedback filter circuit;

[0012] a first capacitor, a first end of the first capacitor being electrically connected with a second end of the first resistor;

[0013] a second capacitor, a first end of the second capacitor being electrically connected with the second end of the first resistor;

[0014] a second resistor, a first end of the second resistor being electrically connected with a second end of the first capacitor and a second end of the second capacitor;

[0015] a first comparator, a negative phase input end of the first comparator being electrically connected with the second end of the second resistor, a positive phase input end of the first comparator being used for inputting a first reference voltage, an output end of the first comparator being electrically connected with the second end of the second resistor, and the output end of the first comparator being an output end of the multi-feedback filter circuit;

[0016] a third resistor, a first end of the third resistor being electrically connected with the first resistor, and a second end of the third resistor being used for inputting a second reference voltage.

[0017] According to one embodiment of the present application, the notch filter comprises a Bainter notch filter, an input end of the Bainter notch filter being electrically connected with an output end of the second-stage multi-feedback filter circuit, and an output end of the Bainter notch filter being electrically connected with the detection unit.

[0018] According to one embodiment of the present application, the Bainter notch filter comprises:

[0019] an inverting proportional operational amplifier, a negative phase input end of the inverting proportional operational amplifier being electrically connected with the output end of the second-stage multi-feedback filter circuit, and a positive phase input end of the inverting proportional operational amplifier being used for inputting a third reference voltage;

[0020] an integral amplifier, a negative phase input end of the integral amplifier being electrically connected with an output end of the inverting proportional operational amplifier, and a positive phase input end of the integral amplifier being used for inputting a fourth reference voltage;

[0021] a non-inverting proportional operational amplifier, a positive phase input end of the non-inverting proportional operational amplifier being electrically connected with an output end of the integral amplifier, and an output end of the non-inverting proportional operational amplifier being electrically connected with the detection unit and a negative phase input end of the non-inverting proportional operational amplifier respectively;

[0022] a fourth resistor, a first end of the fourth resistor being electrically connected with the negative phase input end of the integral amplifier, and a second end of the fourth resistor being electrically connected with the output end of the non-inverting proportional operational amplifier;

[0023] The first end of the fifth resistor is electrically connected with the ground node;

[0024] The first end of the third capacitor is electrically connected with the output end of the integral amplifier and the second end of the fifth resistor respectively, and the second end of the third capacitor is electrically connected with the negative phase input end of the inverting proportional operational amplifier.

[0025] According to an embodiment of the present application, the inverting proportional operational amplifier comprises:

[0026] The first end of the sixth resistor is electrically connected with the output end of the second-stage multi-feedback filter circuit;

[0027] The negative phase input end of the second comparator is electrically connected with the second end of the sixth resistor, and the positive phase input end of the second comparator is used for connecting with the third reference voltage;

[0028] The first end of the seventh resistor is electrically connected with the second end of the sixth resistor, and the second end of the seventh resistor is electrically connected with the output end of the second comparator.

[0029] According to an embodiment of the present application, the integral amplifier comprises:

[0030] The negative phase input end of the third comparator is electrically connected with the output end of the second comparator, and the positive phase input end of the third comparator is used for connecting with the fourth reference voltage;

[0031] The first end of the fourth capacitor is electrically connected with the negative phase input end of the third comparator, and the second end of the third capacitor is electrically connected with the output end of the third comparator.

[0032] According to an embodiment of the present application, the in-phase proportional operational amplifier comprises:

[0033] The positive phase input end of the fourth comparator is electrically connected with the output end of the third comparator;

[0034] The first end of the eighth resistor is electrically connected with the output end of the fourth comparator;

[0035] The first end of the ninth resistor is electrically connected with the second end of the eighth resistor and the negative phase input end of the fourth comparator respectively, and the second end of the ninth resistor is electrically connected with the ground node.

[0036] According to an embodiment of the present application, the range of the target passband frequency is 20kHz-60kHz, and the range of the target stopband frequency is 35kHz-37kHz.

[0037] In a second aspect, the present application provides an arc detection system, which comprises the arc detection circuit as described above.

[0038] According to the arc detection system provided in the application, the filter circuit in the arc detection circuit can filter the arc signal in the effective frequency band of the arc signal, the detection range is large, the notch circuit can limit the working frequency band of the photovoltaic inverter in the stop band, so as to reduce the noise generated in the working process of the photovoltaic inverter, and the phenomenon of false negatives and false positives caused by the noise is reduced, and the accuracy of arc detection is improved.

[0039] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and / or realization of the inherent aspects of the application. BRIEF DESCRIPTION OF DRAWINGS

[0040] The above and / or additional aspects and advantages of the application will become apparent and be readily appreciated from the description of the embodiments, which follows, including the accompanying drawings.

[0041] Figure 1 is a structural block diagram of an arc detection circuit of a photovoltaic inverter provided by an embodiment of the application;

[0042] Figure 2 is a circuit diagram of a multi-feedback filter circuit provided by an embodiment of the application;

[0043] Figure 3 is a structural block diagram of a Bainter notch filter provided by an embodiment of the application;

[0044] Figure 4 is a circuit diagram of a Bainter notch filter provided by an embodiment of the application;

[0045] Figure 5 is a simulation waveform diagram of the amplitude / phase frequency response of the arc detection circuit provided by an embodiment of the application;

[0046] Figure 6 is a structural schematic diagram of the arc detection system provided by an embodiment of the application.

[0047] Reference signs:

[0048] Filter circuit 100, first-stage multi-feedback filter circuit 110, second-stage multi-feedback filter circuit 120, notch circuit 200, Bainter notch filter 210, inverting proportional operational amplifier 211, integrating amplifier 212, non-inverting proportional operational amplifier 213, detection unit 300, analog-to-digital converter 310, deep learning module 320, first to twelfth resistors R1-R12, first to fourth capacitors C1-C4, first to fourth comparators U1-U4. DETAILED DESCRIPTION

[0049] Embodiments of the present application are described below in detail with reference to the accompanying drawings, wherein like or similar elements are denoted by the same or similar reference signs throughout the drawings. The embodiments described below are exemplary only, and are not intended to limit the present application.

[0050] In the following description, "circuitry" refers to an electrical line loop formed by at least one element or sub-circuit through electrical or electromagnetic connection. When it is said that an element or circuit is "coupled to" or "connected to" another element or that the element / circuit is "coupled between" or "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when it is said that an element is "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0051] In the description, the terms "first", "second", and the like are used to distinguish similar objects, and are not used to describe a particular order or sequence. It should be understood that the numerical descriptors used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than that illustrated or described here, and the objects distinguished by "first", "second", etc. are usually a class, not limited to the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / ", generally means that the front and rear associated objects are in an "or" relationship.

[0052] In addition, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0053] With the increasing demand for clean energy around the world, photovoltaic power generation technology is developing rapidly. With the continuous maturity of technology and the continuous decline of cost, solar devices have gradually become an important part of the urban energy structure. This trend has led to a sharp increase in electrical connection points involved in solar power generation systems, and each connection point is a potential source of failure, especially in a direct current environment, as the current flows in a single direction and the voltage is high, which is more likely to cause a direct current arc fault.

[0054] In order to prevent the occurrence of electric shock or fire hazards, it is necessary to add an arc fault protection circuit in the power system, but the accuracy and stability of the arc fault protection circuit in the power system are difficult to meet the requirements.

[0055] Referring to Figure 1 One embodiment of the present application proposes an arc detection circuit of a photovoltaic inverter, which comprises a filter circuit, a notch circuit 200 and a detection unit 300. The filter circuit is configured to access the arc signal detected by the photovoltaic inverter and perform filtering processing on the arc signal based on a target passband frequency, and provide a first signal after filtering, and the target passband frequency is the effective frequency range of the arc signal; the notch circuit 200 is connected with the output end of the filter circuit, and is configured to perform notch processing on the filtered arc signal based on a target stopband frequency, and provide a second signal after notch processing, and the target stopband frequency is the working frequency range of the photovoltaic inverter; the detection unit 300 is connected with the output end of the notch circuit 200, and is configured to judge whether there is an arc fault according to the second signal.

[0056] The filter circuit is mainly used for filtering processing on the original arc signal detected from the photovoltaic inverter. The original arc signal usually contains various frequency components, including useful arc characteristic signals and useless noise and interference signals. The filter circuit is mainly used for filtering out useless noise and interference signals.

[0057] The input end of the filter circuit is used for accessing the original arc signal detected from the photovoltaic inverter. The signals in the target passband frequency range in the original arc signal can be output from the output end of the filter, that is, the first signal is the signal with the frequency in the target passband frequency range.

[0058] The effective frequency range of the arc signal can be different due to different arc types, working conditions and application scenarios, so the range of the target passband frequency can be selected according to the effective frequency range of the arc signal in the actual application scenario, which is not limited here. For example, when the effective frequency range of the arc signal is between 10 kHz and 50 kHz, the range of the target passband frequency is set to 10 kHz to 50 kHz, which can effectively eliminate the frequency components irrelevant to arc detection or with large interference.

[0059] The notch circuit 200 is electrically connected with the output end of the filter circuit, and is mainly used for suppressing the interference signals of part of the specific frequencies in the first signal, avoiding the potential influence of the interference signals of the specific frequencies on the arc detection result, and transmitting the signal after notch processing to the detection unit 300, and the second signal is the signal in the first signal except the signal with the frequency in the target stopband frequency range.

[0060] It should be noted that the frequency of the driving signal of the switching tube in the photovoltaic inverter is usually also in the range of the target passband frequency of the filter circuit, and when the target band-stop frequency of the notch circuit 200 is set as the frequency of the driving signal of the switching tube, the working frequency band of the photovoltaic inverter can be avoided to be misjudged as an arc signal, and the accuracy of arc detection can be improved.

[0061] The detection unit 300 is connected with the output end of the notch circuit 200, and the detection unit 300 can be internally provided with a logic judgment mechanism to judge whether there is an arc fault according to the characteristics of the second signal.

[0062] In some other embodiments, the arc detection circuit of the photovoltaic inverter can further include an alarm circuit electrically connected with the detection unit 300, and after the detection unit 300 detects an arc fault, the detection unit 300 will immediately trigger the preset alarm mechanism or protection action in the alarm circuit, such as cutting off the fault circuit, issuing an audible and light alarm, and the like, so as to improve the safety of the whole system.

[0063] According to the arc detection circuit of the photovoltaic inverter, the filter circuit can filter the arc signal in the effective frequency band of the arc signal, the detection range is large, the notch circuit 200 can limit the working frequency band of the photovoltaic inverter in the stop band, so as to reduce the noise generated in the working process of the photovoltaic inverter, and avoid the phenomenon of false alarm and false alarm caused by the noise to the arc detection, and improve the accuracy of the arc detection.

[0064] Reference Figure 2 In some embodiments, the filter circuit includes two-stage multi-feedback filter circuits connected in cascade, the input end of the first-stage multi-feedback filter circuit 110 is used to access the arc signal, and the output end of the second-stage multi-feedback filter circuit 120 is electrically connected with the input end of the notch circuit 200.

[0065] The first-stage multi-feedback filter circuit 110 is mainly used to respond to the high-frequency noise in the arc signal, and can effectively attenuate or eliminate the high-frequency interference in the arc signal, so as to provide a relatively pure signal basis for subsequent signal processing. In addition, the first-stage multi-feedback filter circuit 110 can also pre-amplify or pre-adjust the signal to a certain extent, so as to adapt to the processing requirements of the subsequent circuit.

[0066] The second-stage multi-feedback filter circuit 120 is mainly used for fine filtering processing of the signal processed by the first-stage multi-feedback filter circuit 110. The second-stage multi-feedback filter circuit 120 focuses on suppressing the noise in the middle and low frequency band, so as to meet the demand of the system for extracting the specific characteristics of the arc signal.

[0067] What is needed is that the parameters of the electrical elements in the first-stage multi-feedback filter circuit 110 and the second-stage multi-feedback filter circuit 120 can be selected according to the actual application scenario to adjust the gain and phase of the corresponding filter circuit. When the signal amplitude is large, filtering can be performed first and then amplification can be performed to avoid noise saturation; for a signal with high signal-to-noise ratio, amplification can be performed first and then filtering can be performed to avoid causing nonlinear distortion.

[0068] The cascaded two-stage multi-feedback filter circuit is adopted to filter the original arc signal, which not only improves the efficiency and precision of the arc signal processing, but also enhances the stability and anti-interference ability of the system.

[0069] Continuing to refer to Figure 2 In some embodiments, the multi-feedback filter circuit comprises a first resistor R1, a first capacitor C1, a second capacitor C2, a second resistor R2, a first comparator U1, and a third resistor R3. The first end of the first resistor R1 is the input end of the multi-feedback filter circuit; the first end of the first capacitor C1 is electrically connected to the second end of the first resistor R1; the first end of the second capacitor C2 is electrically connected to the second end of the first resistor R1; the first end of the second resistor R2 is electrically connected to the second end of the first capacitor C1, and the second end of the second resistor R2 is electrically connected to the second end of the second capacitor C2; the negative phase input end of the first comparator U1 is electrically connected to the second end of the second resistor R2, the positive phase input end of the first comparator U1 is used to connect a first reference voltage, the output end of the first comparator U1 is electrically connected to the second end of the second resistor R2, and the output end of the first comparator U1 is the output end of the multi-feedback filter circuit; the first end of the third resistor R3 is electrically connected to the first resistor R1, and the second end of the third resistor R3 is used to connect a second reference voltage.

[0070] The negative phase input end of the first comparator U1 has two negative feedback paths from the output end, and the two negative feedback paths can work independently or cooperatively to filter the input signal. This design makes the filter circuit have higher flexibility and adjustability in frequency response and phase characteristics.

[0071] Since the first amplifier is used as the core element, the multi-feedback filter circuit generally has high gain, so that the filter can effectively suppress noise while amplifying weak signals.

[0072] According to Kirchhoff's current law, the center frequency f0 of the multi-feedback filter circuit can be calculated by the following formula:

[0073]

[0074] wherein R1 is the resistance value of the first resistor R1, R2 is the resistance value of the second resistor R2, R3 is the resistance value of the second resistor R2, C1 is the capacitance value of the first capacitor C1, and C2 is the capacitance value of the second capacitor C2.

[0075] Peak gain A of the multi-feedback filter circuit m The peak gain A of the multi-feedback filter circuit can be calculated by the following formula:

[0076]

[0077] The quality factor Q of the multi-feedback filter circuit can be calculated by the following formula:

[0078]

[0079] From the above calculation formulas, it can be seen that the center frequency f0, the peak gain A and the quality factor Q of the multi-feedback band-pass filter are respectively controlled by different elements, which can be independently designed, thereby improving the flexibility of the system. m

[0080] In some embodiments, the notch circuit 200 includes a Bainter notch filter 210, an input end of the Bainter notch filter 210 is electrically connected with the output end of the second-stage multi-feedback filter circuit 120, and an output end of the Bainter notch filter 210 is electrically connected with the detection unit 300.

[0081] The Bainter notch filter 210 generally includes a feedback loop formed by multiple amplifiers, and the quality factor of the Bainter notch filter is not dependent on the precise matching of elements, but is related to the gain of the amplifiers. This feature makes the notch depth not easily affected by environmental factors such as temperature drift and aging, thereby improving the stability and reliability of the filtering. In addition, the Bainter notch filter 210 can accurately suppress signals of a specific frequency while maintaining the passability of signals of other frequencies, thereby improving the signal-to-noise ratio and anti-interference ability of the signals.

[0082] Reference Figure 3 ​In some embodiments, the Bainter trap 210 includes an inverting proportional operational amplifier 211, an integrating amplifier 212, a non-inverting proportional operational amplifier 213, a fourth resistor R4, a fifth resistor R5, and a third capacitor C3. The negative phase input end of the inverting proportional operational amplifier 211 is electrically connected to the output end of the second-stage multi-feedback filter circuit 120, and the positive phase input end of the inverting proportional operational amplifier 211 is used to access a third reference voltage; the negative phase input end of the integrating amplifier 212 is electrically connected to the output end of the inverting proportional operational amplifier 211, and the positive phase input end of the integrating amplifier 212 is used to access a fourth reference voltage; the positive phase input end of the non-inverting proportional operational amplifier 213 is electrically connected to the output end of the integrating amplifier 212, and the output end of the non-inverting proportional operational amplifier 213 is electrically connected to the detection unit 300 and the negative phase input end of the non-inverting proportional operational amplifier 213, respectively; the first end of the fourth resistor R4 is electrically connected to the negative phase input end of the integrating amplifier 212, and the second end of the fourth resistor R4 is electrically connected to the output end of the non-inverting proportional operational amplifier 213; the first end of the fifth resistor R5 is electrically connected to the ground node; the first end of the third capacitor C3 is electrically connected to the output end of the integrating amplifier 212 and the second end of the fifth resistor R5, respectively, and the second end of the third capacitor C3 is electrically connected to the negative phase input end of the inverting proportional operational amplifier 211.

[0083] In some embodiments, the inverting proportional operational amplifier 211 is electrically connected to the first end of the tenth resistor R10, and the second end of the tenth resistor R10 is electrically connected to the negative phase input end of the integrating amplifier 212; the output end of the integrating amplifier 212 is electrically connected to the first end of the eleventh resistor R11, and the second end of the eleventh resistor R11 is electrically connected to the output end of the integrating amplifier 212 and the second end of the fifth resistor R5, respectively, and the output end of the non-inverting proportional operational amplifier 213 is electrically connected to the twelfth resistor R12.

[0084] The inverting proportional operational amplifier 211 realizes the amplification and inversion of the signal through its input and feedback resistance network. The input signal enters the inverting input end of the amplifier through the input resistance, and the output signal is fed back to the inverting input end through the feedback resistance, forming a negative feedback, thereby stabilizing the amplification factor and reducing distortion.

[0085] The integrating amplifier 212 is electrically connected to the inverting proportional operational amplifier 211 and the non-inverting proportional operational amplifier 213, respectively, and cooperates with the peripheral fourth resistor R4, fifth resistor R5, and third capacitor C3 to provide low-pass or high-pass filtering function according to design requirements, to achieve the required frequency response.

[0086] The non-inverting proportional operational amplifier 213 is mainly used for merging and processing the signals from the inverting proportional operational amplifier 211 and the integrating amplifier 212, and finally generating a trap response.

[0087] The specific principles of the above modules have been well explained in the related art, and will not be described here.

[0088] Referring to Figure 4 In some embodiments, the inverting proportional operational amplifier 211 includes a sixth resistor R6, a second comparator U2, and a seventh resistor R7. The first end of the sixth resistor R6 is electrically connected to the output end of the second-stage multi-feedback filter circuit 120; the negative phase input end of the second comparator U2 is electrically connected to the second end of the sixth resistor R6, and the positive phase input end of the second comparator U2 is used to access a first reference voltage. The first end of the seventh resistor R7 is electrically connected to the second end of the sixth resistor R6, and the second end of the seventh resistor R7 is electrically connected to the output end of the second comparator U2.

[0089] In some embodiments, the integral amplifier 212 includes a third comparator U3 and a fourth capacitor C4. The negative phase input end of the third comparator U3 is electrically connected to the output end of the second comparator U2, and the positive phase input end of the third comparator U3 is used to access a second reference voltage; the first end of the fourth capacitor C4 is electrically connected to the negative phase input end of the third comparator U3, and the second end of the third capacitor C3 is electrically connected to the output end of the third comparator U3.

[0090] In some embodiments, the in-phase proportional operational amplifier 213 includes a fourth comparator U4, an eighth resistor R8, and a ninth resistor R9. The positive phase input end of the fourth comparator U4 is electrically connected to the output end of the third comparator U3; the first end of the eighth resistor R8 is electrically connected to the output end of the fourth comparator U4; the first end of the ninth resistor R9 is electrically connected to the second end of the eighth resistor R8 and the negative phase input end of the fourth comparator U4, respectively, and the second end of the ninth resistor R9 is electrically connected to the ground node.

[0091] The gain of the inverting proportional operational amplifier 211 wherein R6 is the resistance value of the sixth resistor R6, and R7 is the resistance value of the seventh resistor R7; the gain of the in-phase proportional operational amplifier 213 wherein R8 is the resistance value of the eighth resistor R8, and R9 is the resistance value of the ninth resistor R9.

[0092] According to the gain of the inverting proportional operational amplifier 211 and the gain of the in-phase proportional operational amplifier 213, it can be calculated that the center frequency of the Bainter trap filter 210 The peak gain A of the Bainter trap filter 210 m1 =G2, the quality factor of the Bainter trap filter 210 The three parameter characteristics of the Bainter trap filter 210, the center frequency f1, the quality factor Q1, and the gain Am, are respectively determined by different elements, and there is a regularity, which improves the robustness and flexibility of the system.

[0093] In some embodiments, the target passband frequency ranges from 20 kHz to 60 kHz, and the target stopband frequency ranges from 35 kHz to 37 kHz.

[0094] When the effective frequency band of the arc signal is between 20 kHz and 60 kHz, the target passband frequency is set to range from 20 kHz to 60 kHz, which can effectively eliminate frequency components irrelevant to arc detection or with large interference.

[0095] The frequency of the driving signal of the switching tube in the photovoltaic inverter is usually about 36 kHz. By setting the target stopband frequency to range from 35 kHz to 37 kHz, the working frequency band of the photovoltaic inverter can be avoided to be misjudged as an arc signal, and the accuracy of arc detection can be improved.

[0096] Reference Figure 5 The waveform (1) is the amplitude / phase frequency response curve of the filter circuit 100, and the waveform (2) is the amplitude / phase frequency response curve of the notch circuit 200. As can be seen from the simulation waveform, the passband of the filter circuit 100 has an equal-amplitude ripple. By setting the parameters of each component in the filter circuit 100, the gain minimum point of the filter circuit 100 can be superimposed with the notch frequency band of the notch circuit 200, and the two can complement each other.

[0097] Reference Figure 6 One embodiment of the present application provides an arc detection system, which comprises the arc detection circuit described above.

[0098] In some embodiments, the detection unit 300 comprises an analog-to-digital converter 310 and a deep learning module 320. The output end of the notch circuit 200 is electrically connected to the analog-to-digital converter 310. The analog-to-digital converter 310 is mainly used to convert the analog voltage or current signal captured by the arc detection sensor into a digital signal.

[0099] The output end of the analog-to-digital converter 310 can be electrically connected to the deep learning module 320. The deep learning module 320 has the ability of self-learning and evolution. With the continuous accumulation of data, the deep learning module 320 can continuously optimize its detection model, improve the detection accuracy and response speed, and make the arc detection system continuously adapt to different application scenarios and working environments.

[0100] According to the photovoltaic system of the present application, the filter circuit in the arc detection circuit can filter the arc signal in the effective frequency band of the arc signal, has a large detection range, and the notch circuit 200 can limit the working frequency band of the photovoltaic inverter to the stopband, so as to reduce the phenomenon of false negatives and false positives caused by noise generated during the operation of the photovoltaic inverter, and improve the accuracy of arc detection.

[0101] While the embodiments of the application have been shown and described, it is to be understood that the embodiments can be varied, modified, substituted and changed by those skilled in the art without departing from the principles and spirit of the application, the scope of which is defined by the claims and their equivalents.

Claims

1. An arc detection circuit for a photovoltaic inverter, characterized by, The method comprises the following steps: A filter circuit is configured to access an arc signal detected by the photovoltaic inverter, and filter the arc signal based on a target passband frequency, which is an effective frequency band of the arc signal, to provide a first filtered signal. A notch filter circuit is connected to the output end of the filter circuit, and is configured to notch filter the filtered arc signal based on a target band-stop frequency, which is an operating frequency band of the photovoltaic inverter, to provide a second notched signal. A detection unit is connected to the output end of the notch filter circuit, and is configured to determine whether an arc fault exists according to the second signal.

2. The arc detection circuit of claim 1, wherein, The filter circuit comprises two cascaded stages of multi-feedback filter circuits, the input end of the first stage of multi-feedback filter circuits is used to access the arc signal, and the output end of the second stage of multi-feedback filter circuits is electrically connected to the input end of the notch filter circuit.

3. The arc detection circuit of claim 2, wherein, The multi-feedback filter circuit comprises: A first resistor, the first end of the first resistor being the input end of the multi-feedback filter circuit; A first capacitor, the first end of the first capacitor being electrically connected to the second end of the first resistor; A second capacitor, the first end of the second capacitor being electrically connected to the second end of the first resistor; A second resistor, the first end of the second resistor being electrically connected to the second end of the first capacitor, and the second end of the second resistor being electrically connected to the second end of the second capacitor; A first comparator, the negative phase input end of the first comparator being electrically connected to the second end of the second resistor, the positive phase input end of the first comparator being used to access a first reference voltage, the output end of the first comparator being electrically connected to the second end of the second resistor, and the output end of the first comparator being the output end of the multi-feedback filter circuit; A third resistor, the first end of the third resistor being electrically connected to the first resistor, and the second end of the third resistor being used to access a second reference voltage.

4. The arc detection circuit of claim 2, wherein, The notch filter circuit comprises a Bainter notch filter, the input end of the Bainter notch filter being electrically connected to the output end of the second stage of multi-feedback filter circuits, and the output end of the Bainter notch filter being electrically connected to the detection unit.

5. The arc detection circuit of claim 4, wherein, The Bainter notch filter comprises: An inverting proportional operational amplifier, the negative phase input end of the inverting proportional operational amplifier being electrically connected to the output end of the second stage of multi-feedback filter circuits, and the positive phase input end of the inverting proportional operational amplifier being used to access a third reference voltage; An integral amplifier, the negative phase input end of the integral amplifier being electrically connected to the output end of the inverting proportional operational amplifier, and the positive phase input end of the integral amplifier being used to access a fourth reference voltage; A non-inverting proportional operational amplifier, the positive phase input end of the non-inverting proportional operational amplifier being electrically connected to the output end of the integral amplifier, and the output end of the non-inverting proportional operational amplifier being electrically connected to the detection unit and the negative phase input end of the non-inverting proportional operational amplifier, respectively; A fourth resistor, the first end of the fourth resistor being electrically connected to the negative phase input end of the integral amplifier, and the second end of the fourth resistor being electrically connected to the output end of the non-inverting proportional operational amplifier. A fifth resistor, a first end of the fifth resistor is electrically connected with the ground node; A third capacitor, a first end of the third capacitor is electrically connected with the output end of the integral amplifier and a second end of the fifth resistor respectively, and a second end of the third capacitor is electrically connected with the negative phase input end of the inverting proportional operational amplifier.

6. The arc detection circuit of claim 5, wherein, The inverting proportional operational amplifier comprises: A sixth resistor, a first end of the sixth resistor is electrically connected with the output end of the multi-feedback filter circuit of the second stage; A second comparator, a negative phase input end of the second comparator is electrically connected with a second end of the sixth resistor, and a positive phase input end of the second comparator is used for connecting with a third reference voltage; A seventh resistor, a first end of the seventh resistor is electrically connected with the second end of the sixth resistor, and a second end of the seventh resistor is electrically connected with an output end of the second comparator.

7. The arc detection circuit of claim 6, wherein, The integral amplifier comprises: A third comparator, a negative phase input end of the third comparator is electrically connected with an output end of the second comparator, and a positive phase input end of the third comparator is used for connecting with a fourth reference voltage; A fourth capacitor, a first end of the fourth capacitor is electrically connected with the negative phase input end of the third comparator, and a second end of the third capacitor is electrically connected with the output end of the third comparator.

8. The arc detection circuit of claim 7, wherein, The in-phase proportional operational amplifier comprises: A fourth comparator, a positive phase input end of the fourth comparator is electrically connected with an output end of the third comparator; An eighth resistor, a first end of the eighth resistor is electrically connected with the output end of the fourth comparator; A ninth resistor, a first end of the ninth resistor is electrically connected with a second end of the eighth resistor and a negative phase input end of the fourth comparator respectively, and a second end of the ninth resistor is electrically connected with the ground node.

9. The arc detection circuit of any one of claims 1-8, wherein, The target passband frequency ranges from 20 kHz to 60 kHz, and the target stopband frequency ranges from 35 kHz to 37 kHz.

10. An arc detection system characterized by, The arc detection circuit comprises the arc detection circuit according to any one of claims 1-9. The arc detection circuit comprises the arc detection circuit according to any one of claims 1-9.

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