AFCI sampling improved circuit and photovoltaic inverter

Abstract

The utility model is suitable for the technical field of photovoltaic inverters, and provides an AFCI sampling improved circuit and a photovoltaic inverter, the AFCI sampling improved circuit comprises an arc discharge current detection circuit, a programmable gain amplification circuit, a filter circuit and an analog-to-digital conversion circuit; the output end of the arc discharge current detection circuit is connected with the input end of the programmable gain amplification circuit, the output end of the programmable gain amplification circuit is connected with the input end of the filter circuit, and the output end of the filter circuit is connected with the input end of the analog-to-digital conversion circuit. The output end of the analog-to-digital conversion circuit is connected with the feedback end of the programmable gain amplification circuit. According to the technical scheme of the utility model, arc discharge current signals can be prevented from being topped, and the anti-interference capability of the system and the flexibility of signal processing are effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to photovoltaic technical field especially relates to a kind of AFCI sampling improved circuit and photovoltaic inverter. BACKGROUND

[0002] The arc-drawing detection circuit based on AFCI (Arc Fault Circuit Interrupters) equipped in the photovoltaic inverter on the market usually detects the current of photovoltaic string through Hall current sensor, and when the internal conductor contact part is loose or the wire insulation layer is broken and there is a large current passing through, spark or arc will be generated, at this time, the current signal detected by the Hall current sensor is converted into voltage signal through resistance, and the voltage signal is amplified by the amplification circuit with fixed amplification multiple, and finally transmitted to the corresponding analysis processing module. Among them, the amplification threshold of the amplification circuit to the current signal is usually set based on historical data or user experience, which is a fixed value.

[0003] However, the amplitude of the current of photovoltaic string is uncertain, and if the fixed gain amplification circuit is used to amplify the corresponding current signal, the current signal will be "topped", and in order to avoid the current signal being "topped", the gain resistance of the amplification circuit needs to be replaced to change the gain multiple, which will increase the workload of detection and reduce the detection efficiency. Moreover, if the detection environment is complex, the detection result is easily affected by environmental interference factors such as noise, which will lead to inaccurate detection and even trigger false alarm. UTILITY MODEL CONTENTS

[0004] The utility model provides AFCI sampling improved circuit, aims at avoiding arc current signal being "topped", and effectively improving the anti-interference ability of system and the flexibility of signal processing.

[0005] The utility model is realized in this way, an AFCI sampling improved circuit, the AFCI sampling improved circuit includes arc current detection circuit, programmable gain amplification circuit, filter circuit and analog-digital conversion circuit;

[0006] The output end of the arc current detection circuit is connected with the input end of the programmable gain amplification circuit, the output end of the programmable gain amplification circuit is connected with the input end of the filter circuit, the output end of the filter circuit is connected with the input end of the analog-digital conversion circuit, and the output end of the analog-digital conversion circuit is connected with the feedback end of the programmable gain amplification circuit;

[0007] The arc current detection circuit is used for detecting the current signal of photovoltaic string and converting into voltage signal;

[0008] The programmable gain amplification circuit is configured to amplify the voltage signal.

[0009] The filter circuit is configured to filter the amplified voltage signal.

[0010] The analog-to-digital conversion circuit is configured to convert the filtered voltage signal into a digital signal and feed back to the programmable gain amplification circuit for gain adjustment.

[0011] Further, the programmable gain amplification circuit comprises a decoder, a switch driver and an adjustable gain amplification circuit.

[0012] The output of the decoder is connected to the input of the switch driver, and the multiple outputs of the switch driver are connected to the multiple selection terminals of the adjustable gain amplification circuit one by one.

[0013] The input of the adjustable gain amplification circuit is connected to the output of the arc current detection circuit, and the output of the adjustable gain amplification circuit is connected to the input of the filter circuit.

[0014] Further, the adjustable gain amplification circuit comprises a gain selection circuit and an operational amplification circuit.

[0015] The gain selection circuit is provided with a first terminal, a second terminal and multiple selection terminals, and the operational amplification circuit is provided with a first positive input terminal, a second positive input terminal, a first negative input terminal and a second negative input terminal.

[0016] The multiple selection terminals of the gain selection circuit are connected to the multiple outputs of the switch driver one by one, the first terminal of the gain selection circuit is connected to the first negative input terminal of the operational amplification circuit, and the second terminal of the gain selection circuit is connected to the second negative input terminal of the operational amplification circuit.

[0017] The first positive input terminal and the second positive input terminal of the operational amplification circuit are both connected to the output of the arc current detection circuit, and the output of the operational amplification circuit is connected to the input of the filter circuit. Further, the gain selection circuit is provided with multiple gain circuits, and the multiple gain circuits are connected in parallel, one end of which is connected to the first negative input terminal of the operational amplification circuit, and the other end is connected to the second negative input terminal of the operational amplification circuit.

[0018] Further, the gain circuit comprises a first resistor and a first electron tube, the first resistor and the first electron tube are connected in series, and the controlled terminal of the first electron tube is connected to the switch driver.

[0019] Further, the resistance values of the first resistors in each gain circuit are different.

[0020] Further, the operational amplifier circuit comprises a first operational amplifier, a second operational amplifier, a third operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor;

[0021] The positive input end of the first operational amplifier is connected with the output end of the arc current detection circuit, the negative input end of the first operational amplifier is connected with the first end of the gain selection circuit and one end of the second resistor, and the output end of the first operational amplifier is connected with the other end of the second resistor and one end of the third resistor;

[0022] The positive input end of the second operational amplifier is connected with the output end of the arc current detection circuit, the negative input end of the second operational amplifier is connected with the second end of the gain selection circuit and one end of the fourth resistor, and the output end of the second operational amplifier is connected with the other end of the fourth resistor and one end of the fifth resistor;

[0023] The positive input end of the third operational amplifier is connected with the other end of the fifth resistor and one end of the seventh resistor, and the other end of the seventh resistor is grounded; the negative input end of the third operational amplifier is connected with the other end of the third resistor and one end of the sixth resistor, and the output end of the third operational amplifier is connected with the input end of the filter circuit and the other end of the sixth resistor.

[0024] Further, the arc current detection circuit comprises at least one set of current detection circuit and signal conversion circuit;

[0025] The current detection circuit is connected with the signal conversion circuit, and the signal conversion circuit is connected with the programmable gain amplifier circuit.

[0026] Further, the current detection circuit comprises a Hall sensor, and the signal conversion circuit comprises a transient voltage suppression diode, an eighth resistor, a ninth resistor and a first capacitor;

[0027] The output end of the Hall sensor is connected with one end of the eighth resistor, one end of the ninth resistor and one end of the transient voltage suppression diode, the other end of the eighth resistor is connected with the other end of the transient voltage suppression diode and one end of the first capacitor, and the other end of the first capacitor is grounded; the other end of the ninth resistor is connected with the programmable gain amplifier circuit.

[0028] The utility model also provides a photovoltaic inverter, the photovoltaic inverter includes the AFCI sampling improvement circuit of any one in foregoing.

[0029] The technical scheme of the utility model discloses, through the arc current detection circuit detection photovoltaic group string's current signal and conversion voltage signal, through programmable gain amplifier circuit amplification processing, again through filter circuit filtering processing and analog-digital conversion circuit analog-digital conversion feedback to programmable gain amplifier circuit, to supply programmable gain amplifier circuit according to the feedback result dynamic adjustment gain multiple, avoid signal to be " cut top " or amplitude too small, effectively improved the anti-interference ability of system and the flexibility of signal processing. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is the circuit block diagram of an embodiment of the AFCI sampling improved circuit provided by the utility model;

[0031] Figure 2 It is Figure 1 The circuit block diagram of an embodiment of the programmable gain amplifier circuit in;

[0032] Figure 3 It is Figure 2 The circuit structure schematic diagram of an embodiment of the programmable gain amplifier circuit in;

[0033] Figure 4 It is Figure 1 The circuit structure schematic diagram of an embodiment of the arc current detection circuit in. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following is combined with the drawings and examples, and the utility model is further described in detail.It should be understood that the specific embodiments described here are only used to explain the utility model, and are not used to limit the utility model.

[0035] The AFCI arc detection circuit for detecting photovoltaic group string on the market currently, the gain multiple of the signal amplification circuit equipped by it is often fixed, but the current amplitude of photovoltaic group string has uncertainty, if the fixed gain amplification circuit is used to amplify the corresponding current signal, then the phenomenon that the current signal is " cut top " can exist, and in order to avoid the current signal to be " cut top ", the gain resistor of amplification circuit needs to be replaced to change the gain multiple, and the replacement of resistor on hardware increases the workload of detection and reduces the detection efficiency.Moreover, if the detection environment is complex, the detection result is susceptible to environmental interference factors such as noise, then it can lead to inaccurate detection and even trigger false alarm.

[0036] The AFCI sampling improved circuit provided by the utility model can dynamically adjust the gain multiple according to the current amplitude of photovoltaic group string by setting programmable gain amplifier circuit 20, can avoid the arc current signal to be " cut top ", and effectively improve the anti-interference ability of system and the flexibility of signal processing.

[0037] Embodiment one

[0038] Please refer to Figure 1 The first embodiment of the present application provides an AFCI sampling improvement circuit, which comprises an arc current detection circuit 10, a programmable gain amplification circuit 20, a filter circuit 30 and an analog-digital conversion circuit 40.

[0039] The connection relationship is that the output end of the arc current detection circuit 10 is connected with the input end of the programmable gain amplification circuit 20, the output end of the programmable gain amplification circuit 20 is connected with the input end of the filter circuit 30, the output end of the filter circuit 30 is connected with the input end of the analog-digital conversion circuit 40, and the output end of the analog-digital conversion circuit 40 is connected with the feedback end of the programmable gain amplification circuit 20.

[0040] The arc current detection circuit 10 is used for detecting the current signal of each photovoltaic string and converting it into a voltage signal, and the arc current signal generated when the conductor contact part in the photovoltaic system is loose or the conductor insulation layer is broken can also be detected by the arc current detection circuit 10.

[0041] The programmable gain amplification circuit 20 is used for amplifying the voltage signal output by the arc current detection circuit 10, and the gain multiple can be dynamically adjusted according to the digital signal fed back by the analog-digital conversion circuit 40, so as to avoid the problems that the signal is "cut off" or the amplitude is set too small.

[0042] The filter circuit 30 is used for filtering the voltage signal amplified by the programmable gain amplification circuit 20, filtering out high-frequency noise and unnecessary frequency components, and retaining the effective frequency range of the arc signal, and the filter circuit 30 can be composed of a low-pass filter.

[0043] The analog-digital conversion circuit 40 is used for converting the voltage signal after filtering into a digital signal, and feeding the digital signal back to the programmable gain amplification circuit 20, so that the programmable gain amplification circuit 20 dynamically adjusts the gain multiple according to the feedback digital signal; the analog-digital conversion circuit 40 also transmits the digital signal to the circuit module at the back end for analysis and processing, that is, the output end of the analog-digital conversion circuit 40 is also connected with an analysis and processing module, so as to realize arc alarm. The analog-digital conversion circuit 40 can be an analog-digital converter.

[0044] The technical scheme of the present application detects the current signal of the photovoltaic string by the arc current detection circuit 10 and converts it into a voltage signal, amplifies it by the programmable gain amplification circuit 20, filters it by the filter circuit 30, and converts it into an analog-digital signal by the analog-digital conversion circuit 40, and then feeds it back to the programmable gain amplification circuit 20, so that the programmable gain amplification circuit 20 dynamically adjusts the gain multiple according to the feedback result, avoids the problems that the signal is "cut off" or the amplitude is too small, and effectively improves the anti-interference ability of the system and the flexibility of signal processing.

[0045] Embodiment Two

[0046] Referring to Figure 2 In an embodiment, the programmable gain amplification circuit 20 comprises a decoder 201, a switch driver 202 and a tunable gain amplification circuit 203; wherein the output of the decoder 201 is connected to the input of the switch driver 202, the switch driver 202 has multiple outputs, and the multiple outputs of the switch driver 202 are connected to the multiple selection terminals of the tunable gain amplification circuit 203 one by one; the input of the tunable gain amplification circuit 203 is connected to the output of the arc current detection circuit 10, and the output of the tunable gain amplification circuit 203 is connected to the input of the filter circuit 30.

[0047] In this embodiment, the decoder 201 can be selected as a digital circuit or a logic circuit, which is used to convert the software-controlled level combination into a gain selection signal of the tunable gain amplification circuit 203. That is, the decoder 201 receives the level signal from the control pin and converts it into a gain selection signal sent to the switch driver 202, and the switch driver 202 drives the corresponding switch tube in the tunable gain amplification circuit 203 to be turned on to achieve the purpose of selecting the corresponding gain multiple. The input of the decoder is connected to the output of the analog-to-digital conversion circuit 40 to dynamically adjust the gain of the tunable gain amplification circuit 203 according to the digital signal output by the analog-to-digital conversion circuit 40.

[0048] The switch driver 202 is used to drive the corresponding switch tube in the tunable gain amplification circuit 203 to be turned on according to the gain selection signal of the decoder 201, and to select the corresponding gain multiple by driving the corresponding switch tube in the tunable gain amplification circuit 203 to be turned on, so as to realize dynamic adjustment of the gain multiple.

[0049] Embodiment Three

[0050] Referring to Figure 3 In an embodiment, the tunable gain amplification circuit 203 comprises a gain selection circuit 2031 and an operational amplification circuit 2032; the gain selection circuit 2031 is provided with a first terminal, a second terminal and multiple selection terminals; the operational amplification circuit 2032 is provided with a first positive input terminal, a second positive input terminal, a first negative input terminal and a second negative input terminal; the multiple selection terminals of the gain selection circuit 2031 are connected to the multiple outputs of the switch driver 202 one by one, the first terminal of the gain selection circuit 2031 is connected to the first negative input terminal of the operational amplification circuit 2032, and the second terminal of the gain selection circuit 2031 is connected to the second negative input terminal of the operational amplification circuit 2032; the first positive input terminal and the second positive input terminal of the operational amplification circuit 2032 are both connected to the output of the arc current detection circuit 10, and the output of the operational amplification circuit 2032 is connected to the input of the filter circuit 30.

[0051] The gain selection circuit 2031 is provided with a plurality of gain circuits, such as Figure 3 R11 and S11 in series as one gain circuit, R12 and S12 in series as another gain circuit, and so on, and the plurality of gain circuits are connected in parallel, with one end connected to the first negative input terminal of the operational amplifier circuit 2032 and the other end connected to the second negative input terminal of the operational amplifier circuit 2032. Each gain circuit includes a first resistor and a first electron tube, and the first resistor and the first electron tube are connected in series, and the control ends of the plurality of first electron tubes are respectively connected to the corresponding output terminals of the switch driver 202 and are driven to be turned on or turned off by the switch driver 202.

[0052] The control ends of each first electron tube (i.e. S11-S1n) serve as a plurality of selection terminals of the gain selection circuit 2031, the common end of each first resistor serves as a second terminal of the gain selection circuit 2031, and the common end of each first electron tube serves as a first terminal of the gain selection circuit 2031.

[0053] Further, the resistance values of the first resistors in each gain circuit are different, i.e. the resistance values of the resistors R11-R1n are different.

[0054] The specific principle is that the decoder 201 receives the level signal from the control pin, converts it into a gain selection signal, and sends it to the switch driver 202, which drives the first electron tube of the corresponding gain circuit in the gain selection circuit 2031 according to the gain selection signal to make the first resistor in the gain circuit access the operational amplifier circuit 2032. Since the resistance values of the resistors accessed are different, the gain of the operational amplifier circuit 2032 is also different, and by changing the resistance values of the resistors accessed by the operational amplifier circuit 2032, the gain multiple is dynamically adjusted.

[0055] Further, in actual application, it can be set that when the arc voltage signal amplitude is greater than 3.2V, it is determined that the "top cutting" phenomenon occurs, and the gain multiple of the operational amplifier circuit 2032 is reduced by changing the resistance values of the resistors accessed until the voltage signal amplitude is between 2V-3.2V; when the amplitude of the arc voltage signal is less than 2V, it is determined that the amplitude is too small, and the gain multiple of the operational amplifier circuit is increased until the signal amplitude is between 2V-3.2V, and when the amplitude of the arc voltage signal is between 2-2.3V, the gain multiple remains unchanged.

[0056] For ease of understanding, please refer to Figure 3 In a specific embodiment, the circuit structure of the operational amplifier circuit 2032 is as follows:

[0057] The operational amplifier circuit 2032 comprises a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a seventh resistor R7, and the connection relationship is as follows:

[0058] The positive input terminal of the first operational amplifier U1 is connected with the output terminal of the arc current detection circuit 10, the negative input terminal of the first operational amplifier U1 is connected with the first end (i.e. the common end of S11-S1n) of the gain selection circuit 2031 and one end of the second resistor R2, and the output terminal of the first operational amplifier U1 is connected with the other end of the second resistor R2 and one end of the third resistor R3;

[0059] The positive input terminal of the second operational amplifier U2 is connected with the output terminal of the arc current detection circuit 10, the negative input terminal of the second operational amplifier U2 is connected with the second end (i.e. the common end of R11-R1n) of the gain selection circuit 2031 and one end of the fourth resistor R4, and the output terminal of the second operational amplifier U2 is connected with the other end of the fourth resistor R4 and one end of the fifth resistor R5;

[0060] The positive input terminal of the third operational amplifier U3 is connected with the other end of the fifth resistor R5 and one end of the seventh resistor R7, the other end of the seventh resistor R7 is grounded, the negative input terminal of the third operational amplifier U3 is connected with the other end of the third resistor R3 and one end of the sixth resistor R6, and the output terminal of the third operational amplifier U3 is connected with the input terminal of the filter circuit 30 and the other end of the sixth resistor R6.

[0061] Embodiment four

[0062] Please refer to Figure 4 In an embodiment, the arc current detection circuit 10 comprises at least one set of current detection circuit 101 and signal conversion circuit 102; the current detection circuit 101 is connected with the signal conversion circuit 102, and the signal conversion circuit 102 is connected with the programmable gain amplification circuit 20.

[0063] The current detection circuit 101 in the embodiment is used for detecting the current signal of the photovoltaic string.

[0064] The signal conversion circuit 102 in the embodiment is used for converting the current signal detected by the current detection circuit into a voltage signal and inputting the voltage signal into the programmable gain amplification circuit 20.

[0065] Please continue to refer to Figure 4 Further, in a specific embodiment, each set of current detection circuit 101 can comprise a Hall sensor, and the current signal of the photovoltaic string is detected by the Hall sensor.

[0066] In a specific embodiment, each group of signal conversion circuit 102 comprises a transient voltage suppression diode TVS1, an eighth resistor R81, a ninth resistor R91 and a first capacitor C11; the output end of the Hall sensor is connected with one end of the eighth resistor R81, one end of the ninth resistor R91 and one end of the transient voltage suppression diode TVS1, the other end of the eighth resistor R81 is connected with the other end of the transient voltage suppression diode TVS1 and one end of the first capacitor C11, the other end of the first capacitor C11 is grounded; the other end of the ninth resistor R91 is connected with the programmable gain amplification circuit 20.

[0067] It can be understood that when it is necessary to detect the current of multiple photovoltaic strings, multiple groups of current detection circuit 101 and signal conversion circuit 102 can be arranged, and the circuit structures of each group of current detection circuit 101 and signal conversion circuit 102 are the same.

[0068] In the embodiment, the transient voltage suppression diode TVS1 plays a protection role;

[0069] The eighth resistor R81 and the ninth resistor R91 play a voltage dividing role, and are used for converting the current signal output by the Hall sensor into a voltage signal;

[0070] The first capacitor C1 is used for filtering and improving signal quality.

[0071] The core of the utility model lies in: this AFCI sampling improvement circuit passes through setting programmable gain amplification circuit 20 and can according to the digital signal of the feedback of analog-digital conversion circuit 40 dynamic adjustment gain multiple, make system work in the gain state required, guarantee arc current signal can be effectively amplified in inverter working process, ensure signal stability, improve signal quality, and relative to gain fixed amplification circuit, system can dynamic adjustment gain according to interference factor in the environment, improve signal-to-noise ratio, further strengthen the anti-interference ability of system.

[0072] The utility model also provides a photovoltaic inverter, the photovoltaic inverter includes the AFCI sampling improvement circuit as any one of the above. The detailed structure of the AFCI sampling improvement circuit can refer to the above embodiment, which will not be repeated here; It can be understood that, since the AFCI sampling improvement circuit is used in the photovoltaic inverter of the utility model, the embodiments of the photovoltaic inverter of the utility model include all the technical solutions of all the embodiments of the AFCI sampling improvement circuit, and the technical effects achieved are also completely the same, which will not be repeated here.

[0073] The above merely describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An AFCI sampling improvement circuit, comprising: The AFCI sampling improvement circuit comprises an arc current detection circuit, a programmable gain amplification circuit, a filter circuit and an analog-digital conversion circuit; The output end of the arc current detection circuit is connected with the input end of the programmable gain amplification circuit, the output end of the programmable gain amplification circuit is connected with the input end of the filter circuit, the output end of the filter circuit is connected with the input end of the analog-digital conversion circuit, and the output end of the analog-digital conversion circuit is connected with the feedback end of the programmable gain amplification circuit; The arc current detection circuit is used for detecting a current signal of a photovoltaic string and converting the current signal into a voltage signal. The programmable gain amplification circuit is used for amplifying the voltage signal. The filter circuit is used for filtering the voltage signal after the amplification. The analog-digital conversion circuit is used for converting the voltage signal after the filtering into a digital signal and feeding back to the programmable gain amplification circuit for gain adjustment.

2. The AFCI sampling improvement circuit of claim 1, wherein, The programmable gain amplification circuit comprises a decoder, a switch driver and an adjustable gain amplification circuit. The output end of the decoder is connected with the input end of the switch driver, and a plurality of output ends of the switch driver are connected with a plurality of selection ends of the adjustable gain amplification circuit one by one. The input end of the adjustable gain amplification circuit is connected with the output end of the arc current detection circuit, and the output end of the adjustable gain amplification circuit is connected with the input end of the filter circuit.

3. The AFCI sampling improvement circuit of claim 2, wherein, The adjustable gain amplification circuit comprises a gain selection circuit and an operational amplification circuit. The gain selection circuit is provided with a first end, a second end and a plurality of selection ends, and the operational amplification circuit is provided with a first positive input end, a second positive input end, a first negative input end and a second negative input end. The plurality of selection ends of the gain selection circuit are connected with the plurality of output ends of the switch driver one by one, the first end of the gain selection circuit is connected with the first negative input end of the operational amplification circuit, and the second end of the gain selection circuit is connected with the second negative input end of the operational amplification circuit. The first positive input end and the second positive input end of the operational amplification circuit are both connected with the output end of the arc current detection circuit, and the output end of the operational amplification circuit is connected with the input end of the filter circuit.

4. The AFCI sampling improvement circuit of claim 3, wherein, The gain selection circuit is provided with a plurality of gain circuits, one end of the plurality of gain circuits connected in parallel is connected with the first negative input end of the operational amplification circuit, and the other end is connected with the second negative input end of the operational amplification circuit.

5. The AFCI sampling improvement circuit of claim 4, wherein, Each gain circuit comprises a first resistor and a first electron tube, the first resistor and the first electron tube are connected in series, and the controlled end of the first electron tube is connected with the switch driver.

6. The AFCI sampling improvement circuit of claim 5, wherein, The resistance values of the first resistors in the gain circuits are different.

7. The AFCI sampling improvement circuit of claim 6, wherein, The operational amplification circuit comprises a first operational amplifier, a second operational amplifier, a third operational amplifier, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a seventh resistor. The positive input end of the first operational amplifier is connected with the output end of the arc current detection circuit, the negative input end of the first operational amplifier is connected with the first end of the gain selection circuit and one end of the second resistor, and the output end of the first operational amplifier is connected with the other end of the second resistor and one end of the third resistor; The positive input end of the second operational amplifier is connected with the output end of the arc current detection circuit, the negative input end of the second operational amplifier is connected with the second end of the gain selection circuit and one end of the fourth resistor, and the output end of the second operational amplifier is connected with the other end of the fourth resistor and one end of the fifth resistor; The positive input end of the third operational amplifier is connected with the other end of the fifth resistor and one end of the seventh resistor, and the other end of the seventh resistor is grounded; the negative input end of the third operational amplifier is connected with the other end of the third resistor and one end of the sixth resistor, and the output end of the third operational amplifier is connected with the input end of the filter circuit and the other end of the sixth resistor.

8. The AFCI sampling improvement circuit of any one of claims 1-7, wherein, The arc current detection circuit comprises at least one set of current detection circuit and signal conversion circuit; The current detection circuit is connected with the signal conversion circuit, and the signal conversion circuit is connected with the programmable gain amplification circuit.

9. The AFCI sampling improvement circuit of claim 8, wherein, The current detection circuit comprises a Hall sensor, and the signal conversion circuit comprises a transient voltage suppression diode, an eighth resistor, a ninth resistor and a first capacitor; The output end of the Hall sensor is connected with one end of the eighth resistor, one end of the ninth resistor and one end of the transient voltage suppression diode, the other end of the eighth resistor is connected with the other end of the transient voltage suppression diode and one end of the first capacitor, and the other end of the first capacitor is grounded; the other end of the ninth resistor is connected with the programmable gain amplification circuit.

10. A photovoltaic inverter, characterized by The photovoltaic inverter comprises the AFCI sampling improvement circuit according to any one of claims 1-9.

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