Residual current detection circuit and alternating current power supply system

Abstract

The utility model relates to a residual current detection circuit and an AC power supply system. The residual current detection circuit comprises a Rogowski coil winding a conductor, a passive integration unit circuit, a first filtering unit circuit, a low-frequency integration unit circuit and a second filtering unit circuit. The passive integration unit circuit is used for carrying out integration processing on an input voltage to obtain a first integration signal, and the input voltage is related to a residual current detected by the Rogowski coil; the first filtering unit circuit is used for filtering the first integral signal to obtain a filtered signal; the low-frequency integral unit circuit is used for carrying out integral processing on the filtering signal to obtain a second integral signal; the second filtering unit circuit is used for reducing the gain of the low-frequency integral unit circuit to a target value; the output end of the second filtering unit circuit is used for outputting target current, the target current is residual current, the problem that small current does not output large current saturation is solved, and in addition, the Rogowski coil can be suitable for being installed and used in a narrow space.

Description

Technical Field

[0001] The present disclosure relates to the technical field of electronic circuits, and in particular to a residual current detection circuit and an AC power supply system. Background Art

[0002] In the related art, iron-core current transformers are commonly used for current detection. However, they are relatively large and inconvenient to install. In addition, iron-core current transformers are affected by the excitation current, resulting in no output at low currents, saturation at high currents, and non-linear output. Utility Model Content

[0003] The present disclosure aims to provide a residual current detection circuit and an AC power supply system. The residual current detection circuit avoids the problem in the related art of using an iron core current transformer for current detection, which is affected by the excitation current and causes a small current to have no output and a large current to be saturated. In addition, the iron core current transformer has a relatively large installation size and is inconvenient to fix. Therefore, the use of a Rogowski coil can adapt to installation and use in a small space.

[0004] In order to achieve the above objectives, in a first aspect, the present disclosure provides a residual current detection circuit, comprising:

[0005] a Rogowski coil wound around a conductor;

[0006] a passive integration unit circuit, configured to integrate an input voltage to obtain a first integration signal, wherein the input voltage is related to a residual current detected by the Rogowski coil;

[0007] a first filtering unit circuit, wherein an input end of the first filtering unit circuit is connected to an output end of the passive integration unit circuit, and the first filtering unit circuit is used to filter the first integrated signal to obtain a filtered signal;

[0008] a low-frequency integration unit circuit, wherein an input end of the low-frequency integration unit circuit is connected to an output end of the first filtering unit circuit, and the low-frequency integration unit circuit is used to integrate the filtered signal to obtain a second integrated signal;

[0009] a second filtering unit circuit, wherein an input end of the second filtering unit circuit is connected to an output end of the low-frequency integration unit circuit, and the second filtering unit circuit is used to reduce the gain of the low-frequency integration unit circuit to a target value, wherein the target value is lower than a cutoff frequency;

[0010] The output end of the second filtering unit circuit is used to output a target current, and the target current is the residual current.

[0011] Optionally, the passive integration unit circuit includes a first resistor and a first capacitor, the first resistor is connected in parallel to both ends of the Rogowski coil, the first end of the first capacitor is connected to the first resistor, the second end of the first capacitor is connected to the ground, the first end of the first capacitor is the output end of the passive integration unit circuit, and the output end of the passive integration unit circuit outputs the first integration signal.

[0012] Optionally, the first filtering unit circuit includes a second resistor, a third resistor, a fourth resistor, a second capacitor and a third capacitor;

[0013] The second resistor, the third resistor and the fourth resistor are connected in series in sequence, the first end of the second resistor is the input end of the low-frequency integration unit circuit, the second end of the second resistor is grounded through the second capacitor, the common end of the third resistor and the fourth resistor is grounded through the third capacitor, and the end of the fourth resistor not connected to the third resistor serves as the output end of the first filtering unit circuit, and the output end of the first filtering unit circuit outputs the filtered signal.

[0014] Optionally, the low-frequency integration unit circuit includes a first operational amplifier, a fifth resistor, a sixth resistor and a fourth capacitor;

[0015] The non-inverting input terminal of the first operational amplifier serves as the input terminal of the low-frequency integration unit circuit, the output terminal of the first operational amplifier serves as the output terminal of the low-frequency integration unit circuit, and the output terminal of the low-frequency integration unit circuit outputs the second integrated signal. The output terminal of the first operational amplifier is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the first terminal of the fourth capacitor, and the second terminal of the fourth capacitor and the inverting input terminal of the first operational amplifier are both grounded through the sixth resistor.

[0016] Optionally, the second filtering unit circuit includes a second operational amplifier, a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a fifth capacitor, a sixth capacitor, and a seventh capacitor;

[0017] The non-inverting input terminal of the second operational amplifier serves as the input terminal of the second filtering unit circuit, the inverting input terminal of the second operational amplifier is connected to the first terminal of the seventh resistor, and the second terminal of the seventh resistor is grounded via the fifth capacitor; the output terminal of the second operational amplifier is respectively connected to the first terminal of the eighth resistor, the first terminal of the ninth resistor, and the first terminal of the tenth resistor, the second terminal of the ninth resistor serves as the output terminal of the second filtering unit circuit, the second terminal of the eighth resistor is grounded via the eleventh resistor, the second terminal of the eighth resistor is also connected to the inverting input terminal of the second operational amplifier, the second terminal of the tenth resistor is grounded via the sixth capacitor, and the twelfth resistor is connected in parallel across the sixth capacitor;

[0018] The second end of the tenth resistor is also connected to the non-inverting input terminal of the third operational amplifier, the inverting input terminal of the third operational amplifier is grounded through the thirteenth resistor, the seventh capacitor is connected between the inverting input terminal of the third operational amplifier and the output terminal of the third operational amplifier, the output terminal of the third operational amplifier is connected to the first end of the fourteenth resistor, the second end of the fourteenth resistor is grounded through the sixteenth resistor, and the second end of the fourteenth resistor is also connected to the inverting input terminal of the first operational amplifier through the fifteenth resistor.

[0019] Optionally, it also includes an input matching unit circuit, the input end of the input matching unit circuit is connected to the output end of the low-frequency integration unit circuit, the output end of the input matching unit circuit is connected to the input end of the second filtering unit circuit, and the input matching unit circuit is used to perform input matching on the first operational amplifier and the second operational amplifier.

[0020] Optionally, the input matching unit circuit includes a seventeenth resistor and an eighth capacitor;

[0021] The first end of the seventeenth resistor serves as the input end of the input matching unit circuit, and the second end of the seventeenth resistor serves as the output end of the input matching unit circuit;

[0022] A first end of the eighth capacitor is connected to the second end of the seventeenth resistor, and a second end of the eighth capacitor is grounded.

[0023] Optionally, the first operational amplifier is a low-noise operational amplifier.

[0024] Optionally, the first operational amplifier is a high-bandwidth operational amplifier.

[0025] In a second aspect, the present disclosure provides an AC power supply system, comprising the residual current detection circuit described in any one of the first aspects above.

[0026] The Rogowski coil is a flexible current transformer. Through the above technical solution, the Rogowski coil is used to detect the residual current, and is optimized in combination with the passive integral unit circuit, the first filter unit circuit, the low-frequency integral unit circuit and the second filter unit circuit. The real residual current detected by the Rogowski coil is restored, the current monitoring range is wide, and the problem of small current no output and large current saturation caused by the influence of the excitation current when using the iron core current transformer for current detection in the related technology is avoided; in addition, the installation size of the iron core current transformer is relatively large and it is not convenient to fix. Therefore, the use of the Rogowski coil can adapt to installation and use in a small space.

[0027] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0029] Figure 1 is a block diagram of a residual current detection circuit according to an exemplary embodiment of the present disclosure.

[0030] Figure 2 FIG. 1 is a schematic diagram of a residual current detection circuit according to an exemplary embodiment of the present disclosure.

[0031] Description of Reference Numerals

[0032] R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; R6-sixth resistor; R7-seventh resistor; R8-eighth resistor; R9-ninth resistor; R10-tenth resistor; R11-eleventh resistor; R12-twelfth resistor; R13-thirteenth resistor; R14-fourteenth resistor; R15-fifteenth resistor; R16-sixteenth resistor; R17-seventeenth resistor; C1-first capacitor; C2-second capacitor; C3-third capacitor; C4-fourth capacitor; C5-fifth capacitor; C6-sixth capacitor; C7-seventh capacitor; C8-eighth capacitor; U1-first operational amplifier; U2-second operational amplifier; U3-third operational amplifier; m1-common end; out-output end of the second filtering unit circuit. DETAILED DESCRIPTION

[0033] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0034] In the prior art, a residual current detection circuit is required in the AC power supply system. Iron-core current transformers are used for this purpose. However, iron-core current transformers are relatively large and difficult to secure. Furthermore, due to the influence of the excitation current, the use of iron-core current transformers can lead to problems such as no output at low currents, saturation at high currents, and inability to output linearly.

[0035] In view of this, the embodiments of the present disclosure provide a residual current detection circuit and an AC power supply system, which realize residual current monitoring and have a wide current monitoring range, avoiding the problem of using an iron-core current transformer for current detection in the related art, which is affected by the excitation current and causes small current to have no output and large current to be saturated; in addition, the installation size of the iron-core current transformer is relatively large and it is not convenient to fix it. Therefore, the use of a Rogowski coil can adapt to installation and use in a small space.

[0036] The embodiments of the present disclosure are further explained and illustrated below with reference to the accompanying drawings.

[0037] Figure 1 yes Figure 1 FIG1 is a block diagram of a residual current detection circuit according to an exemplary embodiment of the present disclosure. Figure 1 , the residual current detection circuit may include:

[0038] Rogowski coil, a Rogowski coil is wound around a conductor;

[0039] A passive integration unit circuit, the passive integration unit circuit is used to integrate the input voltage to obtain a first integration signal, the input voltage is related to the residual current detected by the Rogowski coil;

[0040] a first filtering unit circuit, wherein an input end of the first filtering unit circuit is connected to an output end of the passive integration unit circuit, and the first filtering unit circuit is used to filter the first integrated signal to obtain a filtered signal;

[0041] a low-frequency integration unit circuit, wherein an input end of the low-frequency integration unit circuit is connected to an output end of the first filtering unit circuit, and the low-frequency integration unit circuit is used to integrate the filtered signal output by the first filtering unit circuit to obtain a second integrated signal;

[0042] a second filtering unit circuit, wherein an input end of the second filtering unit circuit is connected to an output end of the low-frequency integration unit circuit, and the second filtering unit circuit is used to reduce the gain of the low-frequency integration unit circuit to a target value, where the target value is lower than the cutoff frequency;

[0043] The output end of the second filtering unit circuit is used to output a target current, which is the residual current.

[0044] The Rogowski coil is a flexible current transformer. By means of the technical scheme, the Rogowski coil is used for detecting the residual current, and the passive integration unit circuit, the first filter unit circuit, the low-frequency integration unit circuit and the second filter unit circuit are combined for optimization, so that the real residual current detected by the Rogowski coil is restored, the monitoring range of the current is wide, and the problem of small current no output and large current saturation caused by the influence of excitation current when the iron core type current transformer is used for current detection in the related art is avoided. In addition, the installation size of the iron core type current transformer is relatively large, and it is not convenient to fix. Therefore, the Rogowski coil can be used for installation and use in a narrow space.

[0045] It should be noted that the Rogowski coil is a ring-shaped coil uniformly wound on a non-ferromagnetic material (i.e. a conductor). When the residual current to be monitored passes through the center of the Rogowski coil along the axis, a corresponding changing magnetic field is generated in the volume surrounded by the ring-shaped winding. According to Faraday's law of electromagnetic induction, the changing magnetic field will generate an induced voltage in the Rogowski coil, i.e. the input voltage described above. The input voltage output by the Rogowski coil is linearly related to the derivative of the residual current, i.e. the input voltage reflects the differential of the residual current with respect to time. In order to restore the real residual current, the passive integration unit circuit, the first filter unit circuit, the low-frequency integration unit circuit and the second filter unit circuit are used for integration and filtering to obtain the real residual current detected by the Rogowski coil.

[0046] In the formula, the residual current can be a current to be monitored in an alternating power supply system.

[0047] Figure 2 FIG. 1 is a circuit result schematic diagram of a residual current detection circuit according to an example embodiment of the present disclosure. Figure 2 The specific structures of the passive integration unit circuit, the first filter unit circuit, the low-frequency integration unit circuit and the second filter unit circuit are shown in FIG. 2, and the following will be described with reference to Figure 2 The passive integration unit circuit, the first filter unit circuit, the low-frequency integration unit circuit and the second filter unit circuit are exemplarily described.

[0048] Continuing to refer to Figure 2 In a possible manner, the passive integration unit circuit includes a first resistor R1 and a first capacitor C1, the first resistor R1 is connected in parallel across the Rogowski coil, the first end of the first capacitor C1 is connected with the first resistor R1, the second end of the first capacitor C1 is connected with the ground, the first end of the first capacitor C1 is an output end of the passive integration unit circuit, and the output end of the passive integration unit circuit outputs a first integration signal.

[0049] Among them, the first resistor R1 and the first capacitor C1 constitute a passive RC integrator, which can generate an output voltage corresponding to the integral of the input voltage. The output voltage is the voltage across the first capacitor C1, and the voltage across the first capacitor C1 is the first integrated signal.

[0050] The passive RC integrator is used to implement signal integration operations, thereby achieving functions such as signal smoothing or filtering.

[0051] Continue to refer to Figure 2 In a possible manner, the first filtering unit circuit includes a second resistor R2, a third resistor R3, a fourth resistor R4, a second capacitor C2 and a third capacitor C3; the second resistor R2, the third resistor R3 and the fourth resistor R4 are connected in series in sequence, the first end of the second resistor R2 is the input end of the low-frequency integration unit circuit, the second end of the second resistor R2 is grounded through the second capacitor C2, the common end m1 of the third resistor R3 and the fourth resistor R4 is grounded through the third capacitor C3, and the end of the fourth resistor R4 not connected to the third resistor R3 serves as the output end of the first filtering unit circuit, and the output end of the first filtering unit circuit outputs the filtered signal.

[0052] The first filtering unit circuit is used to filter out the high-frequency signal in the first integrated signal to obtain a low-frequency signal in the first integrated signal. The low-frequency signal is the filtered signal outputted from the output end of the first filtering unit circuit.

[0053] The first filtering unit circuit can filter out noise signals in the first integrated signal, thereby providing a data basis for accurately restoring the waveform of the residual current detected by the Rogowski coil.

[0054] Continue to refer to Figure 2 In a possible manner, the low-frequency integration unit circuit includes a first operational amplifier U1, a fifth resistor R5, a sixth resistor R6, and a fourth capacitor C4; the non-inverting input terminal of the first operational amplifier U1 serves as the input terminal of the low-frequency integration unit circuit, the output terminal of the first operational amplifier U1 serves as the output terminal of the low-frequency integration unit circuit, the output terminal of the low-frequency integration unit circuit outputs a second integrated signal, the output terminal of the first operational amplifier U1 is connected to the first terminal of the fifth resistor R5, the second terminal of the fifth resistor R5 is connected to the first terminal of the fourth capacitor C4, and the second terminal of the fourth capacitor C4 and the inverting input terminal of the first operational amplifier U1 are both grounded through the sixth resistor R6.

[0055] After the first filtering unit circuit filters out the high-frequency signal in the first integrated signal, a low-frequency signal in the first integrated signal is obtained, and the low-frequency signal is integrated based on the low-frequency integration unit circuit.

[0056] It is worth noting that the output signal (second integrated signal) of the first filtering unit circuit is proportional to the integral of the input signal (filtered signal).

[0057] The first operational amplifier U1 may be a low-noise operational amplifier, the first operational amplifier U1 may be a high-bandwidth operational amplifier, or the first operational amplifier U1 may be a low-noise and high-bandwidth operational amplifier.

[0058] The waveform of the residual current detected by the Rogowski coil is accurately restored by the low-frequency integration unit circuit.

[0059] Continue to refer to Figure 2 In a possible embodiment, the second filtering unit circuit includes a second operational amplifier U2, a third operational amplifier U3, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a fifth capacitor C5, a sixth capacitor C6, and a seventh capacitor C7;

[0060] The non-inverting input terminal of the second operational amplifier U2 serves as the input terminal of the second filtering unit circuit, the inverting input terminal of the second operational amplifier U2 is connected to the first terminal of the seventh resistor R7, and the second terminal of the seventh resistor R7 is grounded via the fifth capacitor C5; the output terminal of the second operational amplifier U2 is respectively connected to the first terminal of the eighth resistor R8, the first terminal of the ninth resistor R9, and the first terminal of the tenth resistor R10, the second terminal of the ninth resistor R9 serves as the output terminal of the second filtering unit circuit, the second terminal of the eighth resistor R8 is grounded via the eleventh resistor R11, and the second terminal of the eighth resistor R8 is also connected to the inverting input terminal of the second operational amplifier U2, the second terminal of the tenth resistor R10 is grounded via the sixth capacitor C6, and the twelfth resistor R12 is connected in parallel across the sixth capacitor C6;

[0061] The second end of the tenth resistor R10 is also connected to the non-inverting input terminal of the third operational amplifier U3, the inverting input terminal of the third operational amplifier U3 is grounded through the thirteenth resistor R13, a seventh capacitor C7 is connected between the inverting input terminal of the third operational amplifier U3 and the output terminal of the third operational amplifier U3, the output terminal of the third operational amplifier U3 is connected to the first end of the fourteenth resistor R14, the second end of the fourteenth resistor R14 is grounded through the sixteenth resistor R16, and the second end of the fourteenth resistor R14 is also connected to the inverting input terminal of the first operational amplifier U1 through the fifteenth resistor R15.

[0062] Among them, the non-inverting input terminal of the second operational amplifier U2 receives the output terminal of the low-frequency integration unit circuit to output the second integration signal, and the second end of the ninth resistor R9 is used to output the target current. It can be understood that, Figure 2The out shown in is equivalent to the output end of the second filtering unit circuit.

[0063] Among them, the second filtering unit circuit is based on reducing the gain of the low-frequency integration unit circuit to below the cut-off frequency, rather than making the gain of the low-frequency integration unit circuit tend to be stable, which reduces the noise of the entire residual current detection circuit and makes the DC offset of the first operational amplifier U1 zero, avoiding limiting the range of the output signal, that is, avoiding limiting the output range of the residual current.

[0064] In a possible manner, the residual current detection circuit may further include an input matching unit circuit, the input end of the input matching unit circuit being connected to the output end of the low-frequency integration unit circuit, the output end of the input matching unit circuit being connected to the input end of the second filtering unit circuit, and the input matching unit circuit being used to perform input matching on the first operational amplifier and the second operational amplifier.

[0065] Continue to refer to Figure 2 The input matching unit circuit includes a seventeenth resistor R17 and an eighth capacitor C8; the first end of the seventeenth resistor R17 serves as the input end of the input matching unit circuit, and the second end of the seventeenth resistor R17 serves as the output end of the input matching unit circuit; the first end of the eighth capacitor C8 is connected to the second end of the seventeenth resistor R17, and the second end of the eighth capacitor C8 is grounded.

[0066] It is worth noting that the seventeenth resistor R17 is used to achieve resistance matching, and the eighth capacitor C8 is used to achieve capacitance matching.

[0067] In order to ensure the performance of the second filtering unit circuit, input matching is performed at the input end of the second operational amplifier U2 in the above manner, which is beneficial to reducing signal distortion or gain variation caused by input impedance mismatch.

[0068] The embodiment of the present disclosure further provides an AC power supply system, including the above-mentioned residual current detection circuit, to provide leakage protection for the AC power supply system used in the factory.

[0069] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0070] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0071] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A residual current detection circuit, characterized in that: include: a Rogowski coil wound around a conductor; a passive integration unit circuit, configured to integrate an input voltage to obtain a first integration signal, wherein the input voltage is related to a residual current detected by the Rogowski coil; a first filtering unit circuit, wherein an input end of the first filtering unit circuit is connected to an output end of the passive integration unit circuit, and the first filtering unit circuit is used to filter the first integrated signal to obtain a filtered signal; a low-frequency integration unit circuit, wherein an input end of the low-frequency integration unit circuit is connected to an output end of the first filtering unit circuit, and the low-frequency integration unit circuit is used to integrate the filtered signal to obtain a second integrated signal; a second filtering unit circuit, wherein an input end of the second filtering unit circuit is connected to an output end of the low-frequency integration unit circuit, and the second filtering unit circuit is used to reduce the gain of the low-frequency integration unit circuit to a target value, wherein the target value is lower than a cutoff frequency; The output end of the second filtering unit circuit is used to output a target current, and the target current is the residual current.

2. The circuit according to claim 1, wherein: The passive integration unit circuit includes a first resistor and a first capacitor. The first resistor is connected in parallel to both ends of the Rogowski coil. The first end of the first capacitor is connected to the first resistor, and the second end of the first capacitor is connected to the ground. The first end of the first capacitor is the output end of the passive integration unit circuit, and the output end of the passive integration unit circuit outputs the first integration signal.

3. The circuit according to claim 1, wherein: The first filtering unit circuit includes a second resistor, a third resistor, a fourth resistor, a second capacitor and a third capacitor; The second resistor, the third resistor and the fourth resistor are connected in series in sequence, the first end of the second resistor is the input end of the low-frequency integration unit circuit, the second end of the second resistor is grounded through the second capacitor, the common end of the third resistor and the fourth resistor is grounded through the third capacitor, and the end of the fourth resistor not connected to the third resistor serves as the output end of the first filtering unit circuit, and the output end of the first filtering unit circuit outputs the filtered signal.

4. The circuit according to claim 1, wherein: The low-frequency integration unit circuit includes a first operational amplifier, a fifth resistor, a sixth resistor and a fourth capacitor; The non-inverting input terminal of the first operational amplifier serves as the input terminal of the low-frequency integration unit circuit, the output terminal of the first operational amplifier serves as the output terminal of the low-frequency integration unit circuit, and the output terminal of the low-frequency integration unit circuit outputs the second integrated signal. The output terminal of the first operational amplifier is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the first terminal of the fourth capacitor, and the second terminal of the fourth capacitor and the inverting input terminal of the first operational amplifier are both grounded through the sixth resistor.

5. The circuit according to claim 4, characterized in that The second filtering unit circuit includes a second operational amplifier, a third operational amplifier, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a fifth capacitor, a sixth capacitor, and a seventh capacitor; The non-inverting input terminal of the second operational amplifier serves as the input terminal of the second filtering unit circuit, the inverting input terminal of the second operational amplifier is connected to the first terminal of the seventh resistor, and the second terminal of the seventh resistor is grounded via the fifth capacitor; the output terminal of the second operational amplifier is respectively connected to the first terminal of the eighth resistor, the first terminal of the ninth resistor, and the first terminal of the tenth resistor, the second terminal of the ninth resistor serves as the output terminal of the second filtering unit circuit, the second terminal of the eighth resistor is grounded via the eleventh resistor, the second terminal of the eighth resistor is also connected to the inverting input terminal of the second operational amplifier, the second terminal of the tenth resistor is grounded via the sixth capacitor, and the twelfth resistor is connected in parallel across the sixth capacitor; The second end of the tenth resistor is also connected to the non-inverting input terminal of the third operational amplifier, the inverting input terminal of the third operational amplifier is grounded through the thirteenth resistor, the seventh capacitor is connected between the inverting input terminal of the third operational amplifier and the output terminal of the third operational amplifier, the output terminal of the third operational amplifier is connected to the first end of the fourteenth resistor, the second end of the fourteenth resistor is grounded through the sixteenth resistor, and the second end of the fourteenth resistor is also connected to the inverting input terminal of the first operational amplifier through the fifteenth resistor.

6. The circuit according to claim 5, characterized in that It also includes an input matching unit circuit, the input end of the input matching unit circuit is connected to the output end of the low-frequency integration unit circuit, the output end of the input matching unit circuit is connected to the input end of the second filtering unit circuit, and the input matching unit circuit is used to perform input matching on the first operational amplifier and the second operational amplifier.

7. The circuit according to claim 6, characterized in that The input matching unit circuit includes a seventeenth resistor and an eighth capacitor; The first end of the seventeenth resistor serves as the input end of the input matching unit circuit, and the second end of the seventeenth resistor serves as the output end of the input matching unit circuit; A first end of the eighth capacitor is connected to the second end of the seventeenth resistor, and a second end of the eighth capacitor is grounded.

8. The circuit according to claim 4, characterized in that The first operational amplifier is a low-noise operational amplifier.

9. The circuit according to claim 4, characterized in that The first operational amplifier is a high-bandwidth operational amplifier.

10. An AC power supply system, characterized in that: The residual current detection circuit comprises the residual current detection circuit according to any one of claims 1 to 9.

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