An arc detection circuit and a photovoltaic system

Abstract

This utility model discloses an arc detection circuit and a photovoltaic system. The arc detection circuit includes: a sampling processing module, a phase shifting module, a differential amplification module, a bandpass filter module, and a signal processing module. The sampling processing module is used to acquire the current to be measured and convert it into a sampling voltage; the phase shifting module is connected to the output terminal of the sampling processing module and is used to phase shift the sampling voltage to generate a phase-shifted voltage, with a phase shift angle of less than 90°; the differential amplification module is connected to the output terminals of the sampling processing module and the phase shifting module respectively, and is used to differentially amplify the sampling voltage and the phase-shifted voltage to generate an output voltage; the bandpass filter module is connected to the output terminal of the differential amplification module and is used to filter signals in the output voltage that are outside the arc characteristic frequency range to generate an arc detection voltage; the signal processing module is connected to the output terminal of the bandpass filter module and is used to determine whether arcing has occurred based on the arc detection voltage. This utility model embodiment can improve the accuracy of arc detection results.

Description

Technical Field

[0001] This utility model relates to the field of arc detection technology, and in particular to an arc detection circuit and a photovoltaic system. Background Technology

[0002] Arcing is a breakdown discharge phenomenon of gas under a strong electric field, accompanied by high temperature, intense light, and electromagnetic radiation. A high-temperature arc can instantly ignite nearby insulating materials, dust, or flammable materials, causing equipment damage. Arcing faults are a significant factor in electrical fires and can easily lead to safety accidents; therefore, arcing detection is crucial.

[0003] Current arc detection circuits often consist of amplifier and filter circuits, which are prone to operational amplifier saturation when the sampling ripple is large. Once the operational amplifier is saturated, its output signal is clamped to the maximum threshold voltage that the operational amplifier can output, rather than the actual amplified result of the waveform, causing signal distortion. The output of the operational amplifier after saturation is similar to a square wave signal, which carries high-frequency harmonics, thus affecting the judgment of the arc signal spectrum and consequently affecting the accuracy of the arc detection results. Utility Model Content

[0004] This invention provides an arc detection circuit and a photovoltaic system to improve the accuracy of arc detection results.

[0005] In a first aspect, embodiments of the present invention provide an arc detection circuit, comprising:

[0006] The sampling and processing module is used to acquire the current to be measured and convert it into a sampling voltage.

[0007] A phase-shifting module, connected to the output of the sampling processing module, is used to phase-shift the sampled voltage to generate a phase-shifted voltage, and the phase-shifting angle is less than 90°;

[0008] A differential amplifier module is connected to the output terminal of the sampling processing module and the output terminal of the phase shifting module, respectively, and is used to differentially amplify the sampled voltage and the phase shifting voltage to generate an output voltage;

[0009] A bandpass filter module is connected to the output of the differential amplifier module and is used to filter out signals in the output voltage that are outside the arcing characteristic frequency range and generate an arcing detection voltage.

[0010] The signal processing module is connected to the output of the bandpass filter module and is used to determine whether arcing has occurred based on the arcing detection voltage.

[0011] Optionally, the phase-shifting module includes:

[0012] First operational amplifier, first resistor, and first capacitor;

[0013] One of the first end of the first resistor and the first end of the first capacitor is connected to the output of the sampling processing module, and the other is grounded; the second end of the first resistor and the second end of the first capacitor are both connected to the non-inverting input of the first operational amplifier, the inverting input of the first operational amplifier is connected to the output of the first operational amplifier, and the output of the first operational amplifier serves as the output of the phase shifting module.

[0014] Optionally, the differential amplification module includes:

[0015] The second operational amplifier, the second resistor, the third resistor, the fourth resistor, and the fifth resistor;

[0016] The second resistor is connected between the output of the sampling processing module and the non-inverting input of the second operational amplifier. The third resistor is connected between the output of the phase shifting module and the inverting input of the second operational amplifier. The first end of the fourth resistor is connected to the non-inverting input of the second operational amplifier, and the second end of the fourth resistor is grounded. The fifth resistor is connected between the inverting input of the second operational amplifier and the output of the second operational amplifier. The output of the second operational amplifier serves as the output of the differential amplifier module.

[0017] Optionally, the bandpass filter module includes:

[0018] A low-pass filter unit, the input of which is connected to the output of the differential amplifier module, is used to filter out signals in the output voltage that are greater than a first preset frequency to generate a first filtered signal; wherein, the first preset frequency is the upper limit frequency of the arcing characteristic frequency range.

[0019] A high-pass filter unit is provided, the input of which is connected to the output of the low-pass filter unit, and the output of the high-pass filter unit serves as the output of the band-pass filter module. The high-pass filter unit is used to filter signals in the first filtered signal that are less than a second preset frequency to generate the arc detection voltage. The second preset frequency is the lower limit frequency of the arc characteristic frequency range.

[0020] Optionally, the low-pass filter unit includes: a third operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a second capacitor, and a third capacitor; the first terminal of the sixth resistor serves as the input terminal of the low-pass filter unit; the second terminal of the sixth resistor is connected to the first terminal of the seventh resistor, the first terminal of the eighth resistor, and the first terminal of the second capacitor; the second terminal of the seventh resistor is connected to the inverting input terminal of the third operational amplifier and the first terminal of the third capacitor; the second terminal of the second capacitor is grounded; the second terminals of the eighth resistor and the second terminals of the third capacitor are both connected to the output terminal of the third operational amplifier; the non-inverting input terminal of the third operational amplifier is connected to a reference voltage; and the output terminal of the third operational amplifier serves as the output terminal of the low-pass filter unit.

[0021] The high-pass filter unit includes: a fourth operational amplifier, a ninth resistor, a tenth resistor, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the first terminal of the fourth capacitor serves as the input terminal of the high-pass filter unit; the second terminal of the fourth capacitor is connected to the first terminal of the fifth capacitor, the first terminal of the sixth capacitor, and the first terminal of the ninth resistor; the second terminal of the ninth resistor is grounded; the second terminal of the fifth capacitor is connected to the inverting input terminal of the fourth operational amplifier and the first terminal of the tenth resistor; the second terminals of the sixth capacitor and the tenth resistor are both connected to the output terminal of the fourth operational amplifier; the non-inverting input terminal of the fourth operational amplifier is connected to the reference voltage; and the output terminal of the fourth operational amplifier serves as the output terminal of the high-pass filter unit.

[0022] Optionally, the arc detection circuit further includes: a band-stop filter module, the input of which is connected to the output of the differential amplifier module, and the output of which is connected to the band-pass filter module; the band-stop filter module is used to filter signals with a third preset frequency in the output voltage to generate a second filtered signal; the band-pass filter module is used to filter signals outside the arc characteristic frequency range in the second filtered signal to generate the arc detection voltage; wherein, the third preset frequency is the switching frequency of the switching transistor in the device that generates the current to be measured.

[0023] Optionally, the band-stop filter module includes: an eleventh resistor, a twelfth resistor, a thirteenth resistor, a seventh capacitor, an eighth capacitor, and a ninth capacitor;

[0024] The first terminal of the seventh capacitor serves as the input terminal of the band-stop filter module and is connected to the first terminal of the eleventh resistor; the second terminal of the seventh capacitor is connected to the first terminal of the twelfth resistor and the first terminal of the eighth capacitor; the second terminal of the eleventh resistor is connected to the first terminal of the ninth capacitor and the first terminal of the thirteenth resistor; the second terminals of the twelfth resistor and the ninth capacitor are both grounded; the second terminal of the eighth capacitor serves as the output terminal of the band-stop filter module and is connected to the second terminal of the thirteenth resistor.

[0025] Optionally, the proportional voltage follower module is connected between the output of the bandpass filter module and the signal processing module, and is used to scale the arc detection voltage according to the voltage recognition range of the signal processing module to generate a follower voltage; the signal processing module is used to determine whether arcing has occurred based on the follower voltage.

[0026] Optionally, the proportional voltage follower module includes:

[0027] The voltage divider unit is connected to the output terminal of the bandpass filter module and is used to divide the arc detection voltage to generate a voltage divider voltage.

[0028] A voltage follower is connected to the output terminal of the voltage divider unit and the signal processing module, respectively; the voltage follower is used to perform voltage following on the divided voltage to generate the following voltage.

[0029] Secondly, this utility model embodiment also provides a photovoltaic system, including: an inverter and an arcing detection circuit as provided in any embodiment of this utility model; the arcing detection circuit is used to detect arcing at the DC input terminal or AC output terminal of the inverter.

[0030] The technical solution of this utility model embodiment can convert the current to be measured into a voltage form that is easy to process through a sampling processing module, while completely preserving the arc-related characteristics in the current to be measured. The sampled voltage is phase-shifted within 90° by a phase-shifting module and then differentially amplified by a differential amplification module. This results in a small voltage amplitude after phase-shifting subtraction, preventing output distortion caused by saturation of the differential amplification module due to sampling ripple or excessive effective current. This effectively solves the problem of operational amplifier saturation, signal distortion, and interference with arc signal spectrum judgment caused by large sampling ripple, and effectively expands the applicability and applicable scenarios of this arc detection circuit. Furthermore, because the arc-related characteristics in the sampled voltage and the phase-shifted voltage are out of phase after phase shifting, the arc characteristic signal is still retained after subtracting the sampled voltage and the phase-shifted voltage. The output voltage obtained after phase-shifting subtraction contains the arc characteristic signal from both the sampled voltage and the phase-shifted voltage, which is equivalent to having an additional arc characteristic signal compared to the sampled voltage itself. This is more conducive to arc analysis by the signal processing module and avoids missed detections. By filtering out non-arc characteristic signal frequency bands using a bandpass filter module, the accuracy and anti-interference capability of arc detection are improved. Therefore, this embodiment of the invention can enhance the accuracy of arc detection results.

[0031] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the arc detection circuit provided in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the structure of a phase-shifting module provided in an embodiment of this utility model;

[0035] Figure 3 This is a schematic diagram of another phase-shifting module provided in this embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of the structure of a differential amplifier module provided in an embodiment of this utility model;

[0037] Figure 5This is a schematic diagram of the structure of a bandpass filter module provided in an embodiment of the present invention;

[0038] Figure 6 This is a schematic diagram of another arc detection circuit provided in this embodiment of the present invention;

[0039] Figure 7 This is a schematic diagram of the structure of a band-stop filter module provided in an embodiment of this utility model;

[0040] Figure 8 This is a schematic diagram of the structure of a proportional voltage follower module provided in an embodiment of this utility model;

[0041] Figure 9 This is a waveform diagram of the simulation results under a small current signal;

[0042] Figure 10 This is a waveform diagram of the simulation results under a high current signal. Detailed Implementation

[0043] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0044] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0045] This utility model provides an arc detection circuit that can accurately and reliably detect arcing. Figure 1 This is a schematic diagram of an arc detection circuit provided in an embodiment of this utility model. See also... Figure 1 The arc detection circuit includes: a sampling processing module 10, a phase shifting module 20, a differential amplification module 30, a bandpass filter module 50, and a signal processing module 70.

[0046] Among them, the sampling and processing module 10 is used to acquire the current to be measured I. G And converted into a sampling voltage V in+The phase-shifting module 20 is connected to the output terminal of the sampling processing module 10. The phase-shifting module 20 is used to process the sampled voltage V. in+ Phase shifting is performed to generate phase-shifted voltage V. in- Furthermore, the phase shift angle is less than 90°. The differential amplifier module 30 is connected to the output terminals of the sampling processing module 10 and the phase shift module 20, respectively. The differential amplifier module 30 is used to process the sampled voltage V. in+ and phase shift voltage V in- Differential amplification is performed to generate the output voltage V. in The bandpass filter module 50 is connected to the output of the differential amplifier module 30. The bandpass filter module 50 is used to filter the output voltage V. in Signals outside the characteristic frequency range of arcing are used to generate arcing detection voltage V. Hp The signal processing module 70 is connected to the output of the bandpass filter module 50. The signal processing module 70 is used to process the arc detection voltage V. Hp Determine if arcing has occurred.

[0047] Among them, the current to be measured I G This refers to the current flowing through the location in the circuit where arcing detection is required; in the event of an arcing fault, the measured current I... G This is a mixed current consisting of the abnormal current component caused by arc discharge and the original loop current. For equipment requiring arc detection, the current to be measured, I, is collected at the relevant location. G Arc detection can be performed; the application scenario of the arc detection circuit is not limited here. Depending on the circuit type, the measured current I... G Different characteristics can be observed. For example, when the circuit type is an AC circuit, the arc extinguishes and reignites periodically as the voltage crosses zero, therefore the measured current I... G It exhibits periodic pulse distortion. When the circuit type is a DC circuit, since there is no voltage zero-crossing point, once the arc is generated, it is not easy to extinguish itself. Therefore, the measured current I... G It exhibits continuous, non-periodic high-frequency noise. In practical applications, arcing diagnosis can be adaptively performed based on the circuit type and corresponding arcing characteristics. The sampling processing module 10 may specifically include a current acquisition unit and a voltage conversion unit; the current acquisition unit, for example, is a Hall sensor or other current sensor, used to acquire the current to be measured, I. G The voltage conversion unit may include a resistive element connected between the output terminal of the current acquisition unit and the output terminal of the sampling processing module 10, for converting the measured current I... G The voltage signal is converted into a voltage signal proportional to the current, that is, the measured current I is converted into a voltage signal proportional to the current. G Converted to sampling voltage V in+ And output the sampling voltage V from the output terminal of the sampling processing module 10. in+The core function of the sampling and processing module 10 is to convert the current signal into a voltage form that is easy to process, while fully preserving the measured current I. G Features related to the electric arc, such as amplitude, frequency, and waveform.

[0048] Specifically, phase shifting refers to changing the phase relationship of a signal through phase shifting circuits such as RC phase shifting networks. The phase shifting module 20 can change the phase relationship of the sampled voltage V. in+ The phase shift voltage V is obtained by leading or lagging the original phase shift by a phase angle. in- The output is from the output terminal of the phase shift module 20. In this embodiment, the phase shift angle is set to less than 90°, ensuring a small phase shift angle and a small amplitude of the difference between the signals before and after the phase shift, effectively preventing operational amplifier saturation. Furthermore, because the phase shift angle is less than 90°, the arcing-related characteristic information can still be retained in the difference between the signals before and after the phase shift, thus allowing reliable determination of whether arcing has occurred based on the signal processing results. For example, the phase shift angle can be arbitrarily selected within the range of (0°, 90°), such as setting the phase shift angle to 5°, 10°, 30°, 50°, 70°, or 80°. Further, the phase shift angle can be set between 0° and 30° to avoid operational amplifier saturation by setting a smaller phase shift angle. Specifically, in an arcing detection environment, the sampling voltage V... in+ and phase shift voltage V in- Often subjected to common-mode interference from electromagnetic pulses and power fluctuations, the differential amplifier module 30 significantly attenuates these noises through common-mode suppression, preventing interference from being misinterpreted as an arc signal. For example, the differential amplification ratio in the differential amplifier module 30 can be manually designed; if the differential amplification ratio is designed to be 50, and V... in+ -V in- =0.1V, then the amplified signal is 5V.

[0049] The characteristic frequency range of arcing is, for example, between 10kHz and 200kHz. However, inherent circuit noise, such as thermal noise from the amplifier module itself and spike noise generated by device switching operations, may mask the arcing signal, leading to misjudgment. Using a bandpass filter module (50) that only allows signals within the characteristic arcing frequency range to pass through can filter out other interference signals, ensuring that only the arcing-specific frequency band signal enters the subsequent circuit. This process improves the accuracy and anti-interference capability of arcing detection.

[0050] The signal processing module 70 can adaptively perform arcing diagnosis based on the arcing characteristics of the device under test, such as using spectrum analysis. The specific process of arcing diagnosis will not be elaborated here. Specifically, the signal processing module 70 may include an analog-to-digital converter (ADC) and a digital signal processor (DSP). The analog signal processed by the bandpass filter module 50 is first converted into a digital signal by the ADC, and then the digital signal is received in real time by the DSP. The DSP has high-speed computing capabilities and can complete signal analysis within milliseconds, thereby avoiding the risk of continuous arcing. The DSP can pre-store relevant characteristics of normal waveforms to compare with the measured waveform during arcing detection to determine whether arcing has occurred. For example, the signal processing module 70 can process the arcing detection voltage V... Hp Fourier decomposition is performed to compare the arcing signal with the signal under normal, non-arcging conditions to identify whether arcing has occurred. Specifically, Fourier decomposition can detect the arcing detection voltage V. Hp Converting from the time domain to the frequency domain and extracting the unique frequency components of arcing is the key basis for distinguishing arcing from normal signals.

[0051] In the arc detection circuit provided in this embodiment of the utility model, the sampling processing module 10 can detect the current I to be measured. G It is converted into an easily processed voltage form while fully preserving the measured current I. G Features related to electric arcs. The sampled voltage V... in+ By performing a phase shift within 90° using phase shift module 20 followed by differential amplification using differential amplification module 30, the voltage amplitude after phase shift subtraction is minimized. This prevents output distortion caused by saturation of differential amplification module 30 due to sampling ripple or excessive effective current. It effectively solves the problems of operational amplifier saturation, signal distortion, and interference with arcing signal spectrum judgment caused by large sampling ripple, and effectively expands the applicability and scenarios of this arcing detection circuit. Furthermore, because the sampled voltage V after phase shifting... in+ and phase shift voltage V in- The characteristic phase misalignment associated with arcing, therefore the sampling voltage V in+ and phase shift voltage V in- The arcing characteristic signal will still be retained after subtraction, and the output voltage V obtained after phase shifting and subtraction will also be retained. in Includes sampling voltage V in+ and phase shift voltage V in- The arcing characteristic signal in both is equivalent to the sampling voltage V. in+The system also generates an additional arcing characteristic signal, which is more beneficial for the signal processing module 70 to perform arcing analysis and avoid missed detections. By filtering out non-arcing characteristic signal frequency bands through the bandpass filter module 50, the accuracy and anti-interference capability of arcing detection are improved. Therefore, this embodiment of the invention can improve the accuracy of arcing detection results.

[0052] The above embodiments exemplarily explain the function of each module in the arc detection circuit. The specific structure that each functional module may have is described below.

[0053] In one embodiment, optionally, the phase-shifting module includes: a first operational amplifier, a first resistor, and a first capacitor. One of the first terminals of the first resistor and the first capacitor is connected to the output terminal of the sampling processing module, and the other is grounded; the second terminals of both the first resistor and the first capacitor are connected to the non-inverting input terminal of the first operational amplifier, and the inverting input terminal of the first operational amplifier is connected to its output terminal. The output terminal of the first operational amplifier serves as the output terminal of the phase-shifting module. This embodiment uses operational amplifiers and resistor-capacitor components to construct the phase-shifting module, making its structure simple and easy to implement. In this embodiment, the cutoff frequency of the phase-shifting module (denoted as f) is... c )for: Where R1 represents the first resistor, and its resistance value is used in the calculation; C1 represents the first capacitor, and its capacitance value is used in the calculation; the cutoff frequency refers to the frequency point at which the signal power or amplitude drops to a specific proportion during the phase shift process, and it is the transition point from "allowing the signal to pass" to "signally attenuating the signal".

[0054] Specifically, depending on actual needs, the phase shift module 20 can be configured with a low-pass phase shift circuit structure or a high-pass phase shift circuit structure, which will be explained below.

[0055] Figure 2 This is a schematic diagram of the structure of a phase-shifting module provided in an embodiment of this utility model. See also... Figure 2 In one embodiment, the phase-shifting module 20 optionally has a low-pass phase-shifting circuit structure. The first terminal of the first resistor R1 is connected to the output terminal of the sampling module and connected to the sampling voltage V. in+ The first terminal of the first capacitor C1 is grounded. Correspondingly, the low-pass phase difference (denoted as Ф1) is: Ф1 = -tan... -1 (2π*f*R1*C1), where f is the frequency of the input signal to the phase shift module 20. In the low-pass phase shift module, the output lags the input, resulting in a negative output. The positive power supply terminal of the first operational amplifier U1 is connected to the positive power supply signal V. cc The negative power supply terminal is grounded. The positive power supply signal V... cc For example, 5V.

[0056] Figure 3This is a schematic diagram of another phase-shifting module provided in an embodiment of this utility model. See also... Figure 3 By swapping the positions of the first resistor R1 and the first capacitor C1, a high-pass circuit is created. The high-pass phase difference (denoted as Ф2) is: f is the frequency of the input signal to the phase shift module 20. In the high-pass phase shift module, the output leads the input and the output is positive.

[0057] For example, the arc detection circuit needs to select the appropriate phase-shifting circuit based on the core frequency components of interest in the specific scenario. If the detection target is the low-frequency characteristics of the arc, a low-pass phase-shifting circuit can be used; if the detection target is the high-frequency characteristics of the arc, a high-pass phase-shifting circuit can be used.

[0058] Figure 4 This is a schematic diagram of the structure of a differential amplifier module provided in an embodiment of this utility model. See also... Figure 4 Based on the above embodiments, optionally, the differential amplifier module 30 includes: a second operational amplifier U2, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5; the second resistor R2 is connected between the output terminal of the sampling processing module 10 and the non-inverting input terminal of the second operational amplifier U2; the third resistor R3 is connected between the output terminal of the phase shift module 20 and the inverting input terminal of the second operational amplifier U2; the first terminal of the fourth resistor R4 is connected to the non-inverting input terminal of the second operational amplifier U2, and the second terminal of the fourth resistor R4 is grounded; the fifth resistor R5 is connected between the inverting input terminal of the second operational amplifier U2 and the output terminal of the second operational amplifier U2; the output terminal of the second operational amplifier U2 serves as the output terminal of the differential amplifier module 30; and the positive power supply terminal of the second operational amplifier U2 is connected to a positive power supply signal V. cc For example, 5V, the negative power supply terminal is connected to a negative power supply signal, such as -5V.

[0059] In this embodiment, the input signal of the differential amplifier module 30 is the sampling voltage V. in+ and phase shift voltage V in- The output signal is the output voltage V. in The differential amplification ratio (denoted as A) is: A = R4 / R2, where the equation holds true when R2 = R3 and R4 = R5. R2 = R3 ensures symmetrical resistance in the input circuit, guaranteeing consistent attenuation of the common-mode signal at both input terminals. R4 = R5 ensures symmetrical feedback and balancing resistors, guaranteeing ideal application of the op-amp's input characteristics during differential signal amplification while eliminating the influence of common-mode signals. When this condition is met, the circuit can ideally amplify the differential signal and suppress the common-mode signal.

[0060] Figure 5 This is a schematic diagram of the structure of a bandpass filter module provided in an embodiment of this utility model. See also... Figure 5The bandpass filter module 50 may include a low-pass filter unit 51 and a high-pass filter unit 52. The input terminal of the low-pass filter unit 51 is connected to the output terminal of the differential amplifier module 30, and the low-pass filter unit 51 is used to filter the output voltage V. in A first filtered signal V is generated from a signal with a frequency greater than a first preset frequency. Lp The first preset frequency is the upper limit of the arcing characteristic frequency range. The input of the high-pass filter unit 52 is connected to the output of the low-pass filter unit 51, and the output of the high-pass filter unit 52 serves as the output of the band-pass filter module 50. The high-pass filter unit 52 is used to filter the first filtered signal V. Lp A signal with a frequency lower than the second preset frequency generates an arc detection voltage V. Hp The second preset frequency is the lower limit of the arcing characteristic frequency range. For example, the first preset frequency is 200kHz and the second preset frequency is 10kHz.

[0061] In this embodiment, a bandpass filter module is constructed by setting a low-pass filter unit 51 and a high-pass filter unit 52 connected in series, which can effectively filter out signals outside the arcing characteristic frequency range in the input signal of the bandpass filter module 50.

[0062] For details, see Figure 5 The low-pass filter unit 51 includes: a third operational amplifier U3, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second capacitor C2, and a third capacitor C3. The first terminal of the sixth resistor R6 serves as the input terminal of the low-pass filter unit 51. The second terminal of the sixth resistor R6 is connected to the first terminals of the seventh resistor R7, the eighth resistor R8, and the second capacitor C2. The second terminal of the seventh resistor R7 is connected to the inverting input terminal of the third operational amplifier U3 and the first terminal of the third capacitor C3. The second terminal of the second capacitor C2 is grounded. The second terminals of the eighth resistor R8 and the third capacitor C3 are both connected to the output terminal of the third operational amplifier U3. The non-inverting input terminal of the third operational amplifier U3 is connected to a reference voltage V. ref The output of the third operational amplifier U3 serves as the output of the low-pass filter unit 51.

[0063] Among them, the positive power supply terminal of the third operational amplifier U3 is connected to the positive power supply signal V. cc For example, 5V, the negative power supply terminal is connected to a negative power supply signal, for example, -5V; reference voltage V ref The value is, for example, 2.5V, because the output voltage V in It can be positive or negative; here, a positive reference voltage V is set. ref A DC bias can be provided to boost the output signal of the low-pass filter unit 51 to a positive value, facilitating subsequent processing. The low-pass cutoff frequency of the low-pass filter unit 51 (denoted as f) lp )for: The low-pass filter unit 51 can filter out interference signals with frequencies higher than the low-pass cutoff frequency. For example, if the arcing characteristic frequency is between 10kHz and 200kHz, the low-pass cutoff frequency is set to 200kHz, and the low-pass filter unit 51 only allows signals with frequencies lower than 200kHz to pass through.

[0064] See also Figure 5 The high-pass filter unit 52 includes: a fourth operational amplifier U4, a ninth resistor R9, a tenth resistor R10, a fourth capacitor C4, a fifth capacitor C5, and a sixth capacitor C6. The first terminal of the fourth capacitor C4 serves as the input terminal of the high-pass filter unit 52. The second terminal of the fourth capacitor C4 is connected to the first terminals of the fifth capacitor C5, the sixth capacitor C6, and the ninth resistor R9, respectively. The second terminal of the ninth resistor R9 is grounded. The second terminal of the fifth capacitor C5 is connected to the inverting input terminal of the fourth operational amplifier U4 and the first terminal of the tenth resistor R10, respectively. The second terminals of the sixth capacitor C6 and the tenth resistor R10 are both connected to the output terminal of the fourth operational amplifier U4. The non-inverting input terminal of the fourth operational amplifier U4 is connected to a reference voltage V. ref The output of the fourth operational amplifier U4 serves as the output of the high-pass filter unit 52.

[0065] Among them, the positive power supply terminal of the fourth operational amplifier U4 is connected to the positive power supply signal V. cc For example, 5V, the negative power supply terminal is connected to a negative power supply signal, for example -5V, the reference voltage V. ref The value is, for example, 2.5V. The Qualcomm cutoff frequency (denoted as f) hp )for: The high-pass filter unit 52 can filter out interference signals with frequencies lower than the high-pass cutoff frequency. For example, if the arcing characteristic frequency is between 10kHz and 200kHz, the high-pass cutoff frequency is set to 10kHz, and the high-pass filter unit 52 only allows signals with frequencies higher than 10kHz to pass through.

[0066] It is understood that the above embodiments exemplify the bandpass filter module 50 as including separately configured low-pass filter unit 51 and high-pass filter unit 52, but this is not intended to limit the present invention. In other embodiments, the bandpass filter module 50 may optionally include an integrated bandpass filter chip or bandpass filter circuit structure.

[0067] Figure 6 This is a schematic diagram of another arc detection circuit provided in an embodiment of this utility model. See also... Figure 6 The arc detection circuit may also include a band-stop filter module 40. The input of the band-stop filter module 40 is connected to the output of the differential amplifier module 30, and the output of the band-stop filter module 40 is connected to the band-pass filter module 50; the band-stop filter module 40 is used to filter the output voltage V. inA signal with a third preset frequency is used to generate a second filtered signal V. bs The bandpass filter module 50 is used to filter the second filtered signal V. bs Signals outside the characteristic frequency range of arcing are used to generate arcing detection voltage V. Hp The third preset frequency is the frequency at which the measured current I is generated. G The switching frequency of the switching transistor in the device.

[0068] For example, generating the current to be measured I G The device under test (DUT), that is, the device that needs to be tested for arcing, can be a power conversion device such as an inverter. This type of device typically consists of multiple switching transistors, and power conversion is achieved by controlling the on / off state of each transistor through a certain switching frequency. Therefore, the aforementioned switching frequency may be related to the current under test, I. G The sampling frequency causes interference. In this embodiment, the interference of the switching frequency on the sampling can be effectively filtered out by setting a band-stop filter module 40.

[0069] Specifically, Figure 7 This is a schematic diagram of the structure of a band-stop filter module provided in an embodiment of this utility model. See also: Figure 7 The band-stop filter module 40 includes: an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a seventh capacitor C7, an eighth capacitor C8, and a ninth capacitor C9; the first terminal of the seventh capacitor C7 serves as the input terminal of the band-stop filter module 40 and is connected to the first terminal of the eleventh resistor R11; the second terminal of the seventh capacitor C7 is connected to the first terminals of the twelfth resistor R12 and the eighth capacitor C8, respectively; the second terminal of the eleventh resistor R11 is connected to the first terminals of the ninth capacitor C9 and the thirteenth resistor R13, respectively; the second terminals of the twelfth resistor R12 and the ninth capacitor C9 are both grounded; the second terminal of the eighth capacitor C8 serves as the output terminal of the band-stop filter module 40 and is connected to the second terminal of the thirteenth resistor R13.

[0070] Among them, the input of the band-stop filter module 40 is the output voltage V. in The output is the second filtered signal V. bs The band-stop cutoff frequency of the band-stop filter module 40 (denoted as f). bs )for: The equation holds true when C7 = C8 = C9 / 2 and R11 = R13 = 2 * R12. It is understandable that the switching frequency usually does not overlap with the arcing characteristic frequency, so filtering has no impact on the arcing judgment result. Furthermore, even without the band-stop filter module 40, the switching frequency can be filtered within the signal processing module 70.

[0071] See also Figure 6Optionally, based on the above embodiments, the arc detection circuit may further include a proportional voltage follower module 60. The proportional voltage follower module 60 is connected between the output of the bandpass filter module 50 and the signal processing module 70. The proportional voltage follower module 60 is used to adjust the arc detection voltage V according to the voltage recognition range of the signal processing module 70. Hp Scaling is performed to generate the following voltage V. dsp The signal processing module 70 is used to process the following voltage V. dsp Determine whether arcing has occurred. Specifically, the voltage recognition range of the signal processing module 70 can refer to the range of the signal processing module 70 used to receive the following voltage V. dsp The voltage recognition range of the interface.

[0072] Specifically, Figure 8 This is a schematic diagram of the structure of a proportional voltage follower module provided in an embodiment of this utility model. See also... Figure 8 The proportional voltage follower module 60 includes a voltage divider unit 61 and a voltage follower 62. The voltage divider unit 61 is connected to the output of the bandpass filter module 50 and is used to control the arc detection voltage V. Hp Voltage division is performed to generate a divided voltage. Voltage follower 62 is connected to the output of voltage divider unit 61 and signal processing module 70 respectively; voltage follower 62 is used to follow the divided voltage and generate a following voltage V. dsp In this way, the proportional voltage follower module 60 can detect the arcing voltage V. Hp The voltage is converted to a voltage range that the chip in signal processing module 70 can recognize, and the output voltage V is then converted. in The arc detection voltage V corresponding to the zero voltage value Hp The value of V is adjusted to the center of the voltage recognition range so that both positive and negative arcing characteristic signals can be normally received and recognized by the signal processing module 70. It is understandable that, in actual operation, the output voltage V... in The arc detection voltage V corresponding to the zero voltage value Hp The value of V can be adjusted to a range close to the center of the voltage recognition range after voltage division. It does not need to be strictly the center point value, as long as the output voltage V is guaranteed. in Both positive and negative features can be effectively extracted.

[0073] For details, see Figure 8 The voltage divider unit 61 includes: a fourteenth resistor R14 and a fifteenth resistor R15; the first end of the fourteenth resistor R14 is connected to the output end of the bandpass filter module 50; the second end of the fourteenth resistor R14 serves as the output end of the voltage divider unit 61 and is connected to the first end of the fifteenth resistor R15; the second end of the fifteenth resistor R15 is grounded.

[0074] The voltage follower 62 includes a fifth operational amplifier U5; the non-inverting input of the fifth operational amplifier U5 is connected to the output of the voltage divider unit 61, the inverting input of the fifth operational amplifier U5 is connected to its output, and the output of the fifth operational amplifier U5 is connected to the signal processing module 70. The positive power supply terminal of the fifth operational amplifier U5 is connected to a positive power supply signal V. cc For example, if it is 5V, the negative power supply terminal is connected to the negative power supply model, such as -5V.

[0075] In the above embodiments, the selection of each capacitor, resistor and operational amplifier can be made according to actual needs, and no limitation is made here.

[0076] In summary, the arc detection circuit provided in this embodiment of the invention, through the combination of the phase shift module 20 and the differential amplifier module 30, solves the operational amplifier saturation problem caused by excessive sampling ripple or effective current. Furthermore, the bandpass filter module 50 and the bandstop filter module 40 ensure that the signal entering the signal processing module 70 contains only arc characteristic signals, thus guaranteeing the reliability of arc detection.

[0077] To verify the performance of the arc detection circuit and ensure the reliability of arc detection, the applicant, based on... Figure 6 The structure shown is designed for different measured currents I. G The size was simulated and verified separately, and the output voltage of each module was collected. The waveforms of the simulation results can be found in [reference needed]. Figure 9 and Figure 10 .in, Figure 9 This is a waveform diagram of the simulation results under a small current signal, specifically the measured current I. G The waveforms of the voltage signals output by each module were collected when the peak-to-peak value was 300mA. Figure 10 This is a waveform diagram of the simulation results under a large current signal, specifically the current under test I. G The waveforms of the voltage signals output by each module are shown, acquired when the peak-to-peak value is 5A. (See also...) Figure 9 and Figure 10 It can be seen that this arc detection circuit can detect the current I under both high and low current conditions. G Reliable processing is performed, and even under high current signals, the output voltage V of the differential amplifier module 30 remains stable. in The output voltage remained within ±5V, and no operational amplifier saturation was observed. These results demonstrate that the arc detection circuit designed in this embodiment will not cause sampling distortion due to sampling current saturation, even under conditions of excessive sampling current ripple.

[0078] This utility model embodiment also provides a photovoltaic system, including the arc detection circuit provided in any embodiment of this utility model, which has corresponding beneficial effects. For example, the photovoltaic system includes: an inverter and the arc detection circuit provided in any of the above embodiments; the arc detection circuit is used to detect arcing at the DC input terminal or AC output terminal of the inverter.

[0079] Specifically, an arcing detection circuit can be connected to the DC input terminal of the inverter, in which case the current to be measured is the input current of the DC input terminal; or, an arcing detection circuit can be connected to the AC output terminal of the inverter, in which case the current to be measured is the output current of the AC output terminal.

[0080] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. An arc detection circuit, characterized in that, include: The sampling and processing module is used to acquire the current to be measured and convert it into a sampling voltage. A phase-shifting module, connected to the output of the sampling processing module, is used to phase-shift the sampled voltage to generate a phase-shifted voltage, and the phase-shifting angle is less than 90°; A differential amplifier module is connected to the output terminal of the sampling processing module and the output terminal of the phase shifting module, respectively, and is used to differentially amplify the sampled voltage and the phase shifting voltage to generate an output voltage; A bandpass filter module is connected to the output of the differential amplifier module and is used to filter out signals in the output voltage that are outside the arcing characteristic frequency range and generate an arcing detection voltage. The signal processing module is connected to the output of the bandpass filter module and is used to determine whether arcing has occurred based on the arcing detection voltage.

2. The arc detection circuit according to claim 1, characterized in that, The phase-shifting module includes: a first operational amplifier, a first resistor, and a first capacitor; One of the first end of the first resistor and the first end of the first capacitor is connected to the output of the sampling processing module, and the other is grounded; the second end of the first resistor and the second end of the first capacitor are both connected to the non-inverting input of the first operational amplifier, the inverting input of the first operational amplifier is connected to the output of the first operational amplifier, and the output of the first operational amplifier serves as the output of the phase shifting module.

3. The arc detection circuit according to claim 1, characterized in that, The differential amplifier module includes: a second operational amplifier, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; The second resistor is connected between the output of the sampling processing module and the non-inverting input of the second operational amplifier. The third resistor is connected between the output of the phase shifting module and the inverting input of the second operational amplifier. The first end of the fourth resistor is connected to the non-inverting input of the second operational amplifier, and the second end of the fourth resistor is grounded. The fifth resistor is connected between the inverting input of the second operational amplifier and the output of the second operational amplifier. The output of the second operational amplifier serves as the output of the differential amplifier module.

4. The arc detection circuit according to claim 1, characterized in that, The bandpass filter module includes: A low-pass filter unit, the input of which is connected to the output of the differential amplifier module, is used to filter out signals in the output voltage that are greater than a first preset frequency to generate a first filtered signal; wherein, the first preset frequency is the upper limit frequency of the arcing characteristic frequency range. A high-pass filter unit is provided, the input of which is connected to the output of the low-pass filter unit, and the output of the high-pass filter unit serves as the output of the band-pass filter module. The high-pass filter unit is used to filter signals in the first filtered signal that are less than a second preset frequency to generate the arc detection voltage. The second preset frequency is the lower limit frequency of the arc characteristic frequency range.

5. The arc detection circuit according to claim 4, characterized in that, The low-pass filter unit includes: a third operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, a second capacitor, and a third capacitor; the first terminal of the sixth resistor serves as the input terminal of the low-pass filter unit; the second terminal of the sixth resistor is connected to the first terminal of the seventh resistor, the first terminal of the eighth resistor, and the first terminal of the second capacitor; the second terminal of the seventh resistor is connected to the inverting input terminal of the third operational amplifier and the first terminal of the third capacitor; the second terminal of the second capacitor is grounded; the second terminals of the eighth resistor and the second terminals of the third capacitor are both connected to the output terminal of the third operational amplifier; the non-inverting input terminal of the third operational amplifier is connected to a reference voltage; and the output terminal of the third operational amplifier serves as the output terminal of the low-pass filter unit. The high-pass filter unit includes: a fourth operational amplifier, a ninth resistor, a tenth resistor, a fourth capacitor, a fifth capacitor, and a sixth capacitor; the first terminal of the fourth capacitor serves as the input terminal of the high-pass filter unit; the second terminal of the fourth capacitor is connected to the first terminal of the fifth capacitor, the first terminal of the sixth capacitor, and the first terminal of the ninth resistor; the second terminal of the ninth resistor is grounded; the second terminal of the fifth capacitor is connected to the inverting input terminal of the fourth operational amplifier and the first terminal of the tenth resistor; the second terminals of the sixth capacitor and the tenth resistor are both connected to the output terminal of the fourth operational amplifier; the non-inverting input terminal of the fourth operational amplifier is connected to the reference voltage; and the output terminal of the fourth operational amplifier serves as the output terminal of the high-pass filter unit.

6. The arc detection circuit according to claim 1, characterized in that, Also includes: A band-stop filter module, wherein the input terminal of the band-stop filter module is connected to the output terminal of the differential amplifier module, and the output terminal of the band-stop filter module is connected to the band-pass filter module; The band-stop filter module is used to filter signals with a third preset frequency in the output voltage to generate a second filtered signal; the band-pass filter module is used to filter signals outside the arcing characteristic frequency range in the second filtered signal to generate the arcing detection voltage; wherein, the third preset frequency is the switching frequency of the switching transistor in the device that generates the current to be measured.

7. The arc detection circuit according to claim 6, characterized in that, The band-stop filter module includes: an eleventh resistor, a twelfth resistor, a thirteenth resistor, a seventh capacitor, an eighth capacitor, and a ninth capacitor; The first terminal of the seventh capacitor serves as the input terminal of the band-stop filter module and is connected to the first terminal of the eleventh resistor; the second terminal of the seventh capacitor is connected to the first terminal of the twelfth resistor and the first terminal of the eighth capacitor; the second terminal of the eleventh resistor is connected to the first terminal of the ninth capacitor and the first terminal of the thirteenth resistor; the second terminals of the twelfth resistor and the ninth capacitor are both grounded; the second terminal of the eighth capacitor serves as the output terminal of the band-stop filter module and is connected to the second terminal of the thirteenth resistor.

8. The arc detection circuit according to claim 1, characterized in that, It also includes: a proportional voltage follower module, connected between the output of the bandpass filter module and the signal processing module, used to scale the arc detection voltage according to the voltage recognition range of the signal processing module to generate a follower voltage; the signal processing module is used to determine whether arcing has occurred based on the follower voltage.

9. The arc detection circuit according to claim 8, characterized in that, The proportional voltage follower module includes: The voltage divider unit is connected to the output terminal of the bandpass filter module and is used to divide the arc detection voltage to generate a voltage divider voltage. A voltage follower is connected to the output terminal of the voltage divider unit and the signal processing module, respectively; the voltage follower is used to perform voltage following on the divided voltage to generate the following voltage.

10. A photovoltaic system, characterized in that, include: Inverter and arc detection circuit as described in any one of claims 1-9; The arc detection circuit is used to detect arcing at the DC input or AC output of the inverter.

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