Insulation resistance detection circuit and photovoltaic system

Abstract

The utility model discloses an insulation impedance detection circuit and electronic equipment, the insulation impedance detection circuit is applied to a photovoltaic array, the photovoltaic array comprises at least one PV + end, a PV-end and a PE end, the insulation impedance detection circuit comprises a first sampling module, a second sampling module, a third sampling module and a fourth sampling module, the first sampling module is connected with the target PV + end and the PV-end, and the second sampling module is connected with the PE end; the first sampling module is configured to sample a first voltage signal between a target PV + end and a PV-end; and the second sampling module is connected with the PE end and the PV-end, and the second sampling module is configured to adjust the insulation impedance between the PE end and the PV-end so as to respectively sample a second voltage signal and a third voltage signal between the PE end and the PV-end under different insulation impedances. Wherein the first voltage signal, the second voltage signal and the third voltage signal are used for determining first insulation impedance between the target PV + end and the target PE end and second insulation impedance between the target PV-end and the target PE end. In this way, photovoltaic array insulation impedance detection is achieved at low cost.

Description

Technical Field

[0001] The present application relates to the field of electronic circuits, and in particular to an insulation impedance detection circuit and a photovoltaic system. Background Art

[0002] A photovoltaic system is a device that converts the voltage output by photovoltaic cell modules into AC voltage or current and outputs it to the power grid.

[0003] For different application scenarios, there may be one or more photovoltaic panel (PV) inputs, depending on the power level of the household energy storage system. To ensure product reliability and safety, the connected photovoltaic PV array needs to be tested for insulation impedance before the household energy storage system is started. The system can only operate if it meets the minimum insulation impedance requirements. The existing PV array insulation impedance detection method has a high detection cost. Utility Model Content

[0004] In order to solve the above problems, the present application provides an insulation impedance detection circuit, which can detect the insulation impedance of multiple PV arrays of a photovoltaic system at a low cost.

[0005] A technical solution adopted in the present application is: to provide an insulation impedance detection circuit, which is applied to a photovoltaic array, the photovoltaic array includes at least one PV+ terminal, a PV- terminal and a PE terminal, and the insulation impedance detection circuit includes: a first sampling module, connected to the target PV+ terminal and the PV- terminal, the first sampling module is configured to sample the first voltage signal between the target PV+ terminal and the PV- terminal; a second sampling module, connected to the PE terminal and the PV- terminal, the second sampling module is configured to adjust the insulation impedance between the PE terminal and the PV- terminal to respectively sample the second voltage signal and the third voltage signal between the PE terminal and the PV- terminal under different insulation impedances; a processing module, connected to the first sampling module and the second sampling module, the processing module is configured to receive the first voltage signal, the second voltage signal and the third voltage signal, and output the first insulation impedance between the target PV positive terminal and the PE terminal, and the second insulation impedance between the PV negative terminal and the PE terminal.

[0006] In one embodiment, the second sampling module includes: an impedance adjustment unit connected to the PE terminal and the PV-terminal, and the impedance adjustment unit is configured to adjust the insulation impedance between the PE terminal and the PV-terminal; a first differential detection unit connected to the PE terminal and the PV-terminal, and the first differential detection unit is configured to sample the second voltage signal and the third voltage signal between the PE terminal and the PV-terminal under different insulation impedances.

[0007] In one embodiment, the impedance adjustment unit includes: an adjustment resistor, a first end of the adjustment resistor is connected to the PE terminal; an adjustment switch, a first end of the adjustment switch is connected to the second end of the adjustment resistor, and a second end of the adjustment switch is connected to the PV-terminal. The adjustment switch is controlled to be closed or opened to adjust the insulation impedance between the PE terminal and the PV negative terminal.

[0008] In one embodiment, the regulating switch is a relay.

[0009] In one embodiment, the first differential detection unit includes: a comparator, a first input terminal of the comparator is connected to the PE terminal, a second input terminal of the comparator is connected to the PV-terminal, and an output terminal of the comparator is used to output a second voltage signal or a third voltage signal; a first resistor, a first end of the first resistor is connected to the first input terminal of the comparator, and a second end of the first resistor is grounded; a first capacitor, a first end of the first capacitor is connected to the first input terminal of the comparator, and a second end of the first capacitor is grounded; a second resistor, a first end of the second resistor is connected to the second input terminal of the comparator, and a second end of the second resistor is connected to the output terminal of the comparator; a second capacitor, a first end of the second capacitor is connected to the second input terminal of the comparator, and a second end of the second capacitor is connected to the output terminal of the comparator.

[0010] In one embodiment, the first differential detection unit also includes: a third resistor, a first end of the third resistor is connected to the PE terminal, and a second end of the third resistor is connected to the first input terminal of the comparator; a fourth resistor, a first end of the third resistor is connected to the PV-terminal, and a second end of the fourth resistor is connected to the second input terminal of the comparator.

[0011] In one embodiment, the first sampling module includes a second differential detection unit connected to the target PV+ terminal and the PV- terminal, and the second differential detection unit is configured to sample a first voltage signal between the target PV+ terminal and the PV- terminal.

[0012] In one embodiment, the insulation impedance detection circuit and the grid voltage detection circuit are arranged on the same circuit board, and the grid voltage detection circuit is configured to collect the phase voltage of the grid.

[0013] In one embodiment, the grid voltage detection circuit includes: a third capacitor, a first end of the third capacitor is connected to the phase node to be detected; a fourth capacitor, a first end of the fourth capacitor is connected to the PE terminal; a third differential detection unit, connected to the second end of the third capacitor and the second end of the fourth capacitor, and the third differential detection unit is configured to collect the phase voltage to be detected.

[0014] Another technical solution adopted by the present application is to provide an electronic device, which includes the above-mentioned insulation impedance detection circuit.

[0015] The insulation impedance detection circuit provided in the present application includes: a first sampling module, connected to the target PV+ terminal and the PV- terminal, the first sampling module is configured to sample the first voltage signal between the target PV+ terminal and the PV- terminal; a second sampling module, connected to the PE terminal and the PV- terminal, the second sampling module is configured to adjust the insulation impedance between the PE terminal and the PV- terminal, so as to respectively sample the second voltage signal and the third voltage signal between the PE terminal and the PV- terminal at different insulation impedances. Among them, the first voltage signal, the second voltage signal and the third voltage signal are used to determine the first insulation impedance between the target PV+ terminal and the PE terminal, and the second insulation impedance between the PV- terminal and the PE terminal; a processing module, connected to the first sampling module and the second sampling module, the processing module is configured to receive the first voltage signal, the second voltage signal and the third voltage signal, and output the first insulation impedance between the target PV positive terminal and the PE terminal, and the second insulation impedance between the PV negative terminal and the PE terminal. In the above manner, the insulation impedance detection of the connected photovoltaic PV array is performed before the household energy storage system is turned on, thereby improving the safety and reliability of the household energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] in:

[0018] Figure 1 is a structural schematic diagram of a first embodiment of an insulation impedance detection circuit provided by the present application;

[0019] Figure 2 is a structural schematic diagram of a second embodiment of an insulation impedance detection circuit provided by the present application;

[0020] Figure 3 is a structural schematic diagram of a third embodiment of an insulation impedance detection circuit provided by the present application;

[0021] Figure 4 is a structural schematic diagram of a fourth embodiment of an insulation impedance detection circuit provided by the present application;

[0022] Figure 5 is a structural schematic diagram of a fifth embodiment of an insulation impedance detection circuit provided by the present application;

[0023] Figure 6 It is a structural schematic diagram of an embodiment of a photovoltaic system provided in the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It will be appreciated that the specific embodiments described herein are only used to explain the present application, rather than to limit the present application. It should also be noted that, for ease of description, only some but not all structures related to the present application are shown in the drawings. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the art without making creative work are within the scope of protection of the present application.

[0025] The terms "first", "second", etc. in this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] See also Figure 1 , Figure 1 1 is a schematic diagram of the structure of the first embodiment of the insulation impedance detection circuit provided by the present application. The insulation impedance detection circuit 100 of this embodiment is applied to the energy storage system. Taking the photovoltaic array in the system as an example, it can be understood that PV is photovoltaic (photovoltaic). Generally, multiple photovoltaic modules form a photovoltaic array. Therefore, the photovoltaic array includes at least one PV+ terminal, a PV- terminal and a PE terminal (connected to the ground wire). In this embodiment, the insulation impedance detection circuit 100 includes a first sampling module 10, a second sampling module 20 and a processing module 30.

[0028] The first sampling module 10 is connected to the target PV+ terminal (any one of the multiple PV+ terminals) and the PV- terminal, and the first sampling module 10 is configured to sample the first voltage signal between the target PV+ terminal and the PV- terminal; the second sampling module 20 is connected to the PE terminal and the PV- terminal, and the second sampling module 20 is configured to adjust the insulation impedance between the PE terminal and the PV- terminal to respectively sample the second voltage signal and the third voltage signal between the PE terminal and the PV- terminal under different insulation impedances. The first voltage signal, the second voltage signal, and the third voltage signal are used to determine the first insulation impedance between the target PV+ terminal and the PE terminal, and the second insulation impedance between the PV- terminal and the PE terminal; the processing module 30 is connected to the first sampling module 10 and the second sampling module 20, and the processing module 30 is configured to receive the first voltage signal, the second voltage signal, and the third voltage signal, and output the first insulation impedance between the target PV positive terminal and the PE terminal, and the second insulation impedance between the PV negative terminal and the PE terminal.

[0029] Optionally, in one embodiment, the second sampling module 20 includes an impedance adjustment unit 21 and a first differential detection unit 22, the impedance adjustment unit 21 is connected to the PE terminal and the PV-terminal, and the impedance adjustment unit 21 is configured to adjust the insulation impedance between the PE terminal and the PV-terminal; the first differential detection unit 22 is connected to the PE terminal and the PV-terminal, and the first differential detection unit 22 is configured to sample the second voltage signal and the third voltage signal between the PE terminal and the PV-terminal under different insulation impedances.

[0030] In one embodiment, two input signals of the first differential detection unit 22 are connected to the PE terminal and the PV-terminal, respectively. The first differential detection unit 22 includes a differential circuit. Since the input impedance of the differential circuit is very high, the current between the two input signals is very small and almost negligible, thereby achieving electrical isolation between PE and the control ground to avoid ground faults and electrical problems.

[0031] Specifically, the impedance adjustment unit 21 first adjusts the insulation impedance between the PE terminal and the PV-terminal to a first resistance value, and the first differential detection unit 22 samples the second voltage signal between the PE terminal and the PV-terminal at the first resistance value; then, the impedance adjustment unit 21 adjusts the insulation impedance between the PE terminal and the PV-terminal to a second resistance value, and the first differential detection unit 22 samples the third voltage signal between the PE terminal and the PV-terminal at the second resistance value.

[0032] Optionally, in one embodiment, the first sampling module 10 includes a second differential detection unit 11 connected to the target PV+ terminal and the PV- terminal, and the second differential detection unit 11 is configured to sample a first voltage signal between the target PV+ terminal and the PV- terminal.

[0033] In one embodiment, the first differential detection unit 22 and the second differential detection unit 11 are two independent and identical detection units, and the first differential detection unit 22 samples a first voltage signal between the target PV+ terminal and the PV- terminal.

[0034] Optionally, in one embodiment, the processing module processes the received first voltage signal, second voltage signal and third voltage signal to output a first insulation impedance between the target PV positive terminal and PE terminal, and a second insulation impedance between the PV negative terminal and PE terminal.

[0035] See also Figure 2 , Figure 3 and Figure 4 , Figure 2 , Figure 3 and Figure 4 1 is a schematic diagram of the structure of the second embodiment, the third embodiment and the fourth embodiment of the insulation impedance detection circuit provided by the present application. Figure 2 , Figure 3 and Figure 4 As shown, the insulation impedance detection circuit 100 includes a first sampling module 10 , a second sampling module 20 and a processing module 30 .

[0036] The first sampling module 10 is connected to the target PV+ terminal and the PV- terminal, and is configured to sample a first voltage signal U between the target PV+ terminal and the PV- terminal. pvN The second sampling module 20 is connected to the PE terminal and the PV-terminal, and the second sampling module 20 is configured to adjust the insulation impedance between the PE terminal and the PV-terminal to respectively sample the second voltage signal U between the PE terminal and the PV-terminal at different insulation impedances iso_1 and the third voltage signal U iso_2 The processing module 30 is connected to the first sampling module 10 and the second sampling module 20, and the processing module 30 is configured to receive the first voltage signal U pvN , the second voltage signal U iso_1 and the third voltage signal U iso_2 , and output a first insulation impedance between the target PV positive terminal and the PE terminal, and a second insulation impedance between the PV negative terminal and the PE terminal.

[0037] In some optional embodiments, such as Figure 2 and Figure 3As shown, the first differential detection unit 22 includes: a comparator A1, a first resistor RS1, a first capacitor CS1, a second resistor RS2 and a second capacitor CS2. The first input terminal of the comparator A1 is connected to the PE terminal, the second input terminal of the comparator A1 is connected to the PV-terminal, and the output terminal of the comparator A1 is used to output the second voltage signal or the third voltage signal; the first end of the first resistor RS1 is connected to the first input terminal of the comparator A1, and the second end of the first resistor RS1 is grounded; the first end of the first capacitor CS1 is connected to the first input terminal of the comparator A1, and the second end of the first capacitor CS1 is grounded; the first end of the second resistor RS2 is connected to the second input terminal of the comparator A1, and the second end of the second resistor RS2 is connected to the output terminal of the comparator A1; the first end of the second capacitor CS2 is connected to the second input terminal of the comparator A1, and the second end of the second capacitor CS2 is connected to the output terminal of the comparator A1.

[0038] In one embodiment, the first differential detection unit 22 includes a differential circuit, which uses an operational amplifier as a differential amplifier. The operational amplifier has a high input impedance and can achieve high impedance isolation. The input of the differential circuit consists of a positive input terminal and an inverting input terminal. The second differential detection unit 11 uses the difference between the two input voltages of the PE terminal and the PV-terminal as the output voltage to achieve signal amplification and comparison.

[0039] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the first differential detection unit 22 further includes: a third resistor RS3 and a fourth resistor RS4. A first end of the third resistor RS3 is connected to the PE terminal, and a second end of the third resistor RS3 is connected to the first input terminal of the comparator A1; a first end of the fourth resistor RS4 is connected to the PV-terminal, and a second end of the fourth resistor RS4 is connected to the second input terminal of the comparator A1.

[0040] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the impedance adjustment unit 21 includes: an adjustment resistor R and an adjustment switch S1. The first end of the adjustment resistor R is connected to the PE terminal; the first end of the adjustment switch S1 is connected to the second end of the adjustment resistor R, and the second end of the adjustment switch S1 is connected to the PV-terminal. The adjustment switch S1 is controlled to be closed or opened to adjust the insulation impedance between the PV-terminal and the PE terminal.

[0041] For example, Figure 2 As shown, the regulating switch S1 is a relay. When the regulating switch S1 is disconnected, the regulating resistor R is suspended, and the second voltage signal U iso_1 The voltage output by comparator A1, that is, the voltage between the PV-terminal and the PE terminal, is converted into the second voltage signal U iso_1 sent to the processing module.

[0042] For example, Figure 3 As shown, when the regulating switch S1 is closed, the regulating resistor R is connected to the insulation impedance detection circuit 100 and connected in parallel with the insulation detection resistor from the PV-terminal to the PE terminal to be detected. iso_2 The voltage output by comparator A1, that is, the voltage between PV- and PE terminals, is converted into the third voltage signal U iso_2 sent to the processing module.

[0043] In some optional embodiments, such as Figure 4 As shown, Figure 4 The insulation impedance detection circuit 100 shown in FIG. Figure 2 and Figure 3 The main difference of the insulation impedance detection circuit 100 shown in FIG. 1 is that the impedance adjustment unit 21 is reduced, and only the second differential detection unit 11 is retained. In one embodiment, the second differential detection unit 11 and the first differential detection unit 22 are two independent and identical detection units. Therefore, the components in the second differential detection unit 11 are shown in FIG. Figure 2 and Figure 3 The relevant description of the illustrated embodiment will not be repeated here.

[0044] For example, Figure 4 As shown, the first voltage signal U pvN The voltage output by comparator A1, that is, the voltage between the target PV+ terminal and the PV- terminal, is converted into the first voltage signal U pvN sent to the processing module.

[0045] For example, Figure 2 and Figure 4 Taking the embodiment shown in the figure as an example, in the processing module of the energy storage system, the first voltage signal U pvN and the second voltage signal U iso_1 According to KCL (Kirchhoff's Current Law), we can list equation (1), where R pvNt is the insulation resistance between the target PV+ terminal and the PE terminal, R pvNb Is the insulation resistance between the PV-end and the PE end:

[0046]

[0047] For example, Figure 2 , Figure 3 and Figure 4 Taking the embodiment shown in the figure as an example, in the processing module of the energy storage system, the first voltage signal U pvN , the second voltage signal U iso_1 and the third voltage signal U iso_2 According to the KCL formula, formula (2) can be listed:

[0048]

[0049] Formula (1) and formula (2) form a system of two-variable linear equations as formula (3):

[0050]

[0051] Solving the two-variable linear equation system (3) yields the following result:

[0052]

[0053] The processing module of the photovoltaic energy storage system automatically calculates the insulation resistance R between the PV+ terminal and the PE terminal. pvNt And the insulation resistance R between PV- and PE pvNb .

[0054] See also Figure 5 , Figure 5 It is a structural schematic diagram of the fifth embodiment of the insulation impedance detection circuit provided in the present application.

[0055] Optionally, the insulation impedance detection circuit 100 and the grid voltage detection circuit 200 are arranged on the same circuit board, and the grid voltage detection circuit 200 is configured to collect the phase voltage of the grid.

[0056] Optionally, the grid voltage detection circuit 200 includes a third capacitor C3, a fourth capacitor C4 and a third differential detection unit 210. In one embodiment, the third differential detection unit 210 and the first differential detection unit 22 are two independent and identical detection units. Therefore, the third differential detection unit 210 can refer to Figure 2 The description of the first differential detection unit 22 is not repeated here.

[0057] In one embodiment, the third capacitor C3 and the fourth capacitor C4 can be AC ​​blocking capacitors, which can isolate the DC signal and will not affect the DC impedance between the PE terminal and the control ground, thereby maintaining a high impedance state between the PE terminal and the control ground and preventing the first voltage signal U iso_1 and the second voltage signal U iso_2 The insulation resistance decreases as a result of the decrease.

[0058] Specifically, the first end of the third capacitor C3 is connected to the phase node to be detected; the first end of the fourth capacitor C4 is connected to the PE terminal; the third differential detection unit 210 is connected to the second end of the third capacitor C3 and the second end of the fourth capacitor C4, and the third differential detection unit 210 is configured to collect the phase voltage to be detected.

[0059] For example, Figure 5As shown, the voltage output by comparator A1 is the phase voltage U of the grid voltage A, B, C. ABC_Sense , will U ABC_Sense The phase voltage is sent to the DSP controller of the photovoltaic energy storage system to complete the detection of the grid voltage.

[0060] When the insulation impedance detection circuit of this embodiment is applied to electronic equipment, an adjustment resistor and an adjustment switch are used. By opening and closing the adjustment switch, the adjustment resistor is suspended or connected to the insulation impedance detection circuit, so that the voltage values ​​between the PV-terminal and the PE terminal under different insulation impedances are sampled respectively, and the insulation impedance between the target PV+terminal and the PE terminal and the insulation impedance between the PV-terminal and the PE terminal are calculated through the processing module. This embodiment completes the insulation impedance detection with a simple circuit design, saving costs.

[0061] See also Figure 6 , Figure 6 It is a structural schematic diagram of an embodiment of a photovoltaic system provided in the present application. The photovoltaic system includes an insulation impedance detection circuit 100, a grid voltage detection circuit 200, a maximum power tracking boost converter 300, an inverter 400, a bidirectional buck-boost converter 500 and a controller 600. The insulation impedance detection circuit 100 is as introduced in the above embodiment and will not be repeated here.

[0062] Specifically, the insulation impedance detection circuit 100 is connected to the photovoltaic array, the maximum power tracking boost converter 300 and the controller 600; the maximum power tracking boost converter 300 is connected to the inverter 400 and the controller 600; the inverter 400 is connected to the bidirectional buck-boost converter 500, the controller 600, the power grid and the load; the bidirectional buck-boost converter 500 is connected to the maximum power tracking boost converter 300 and the controller 600, and the power grid voltage detection circuit 200 is connected to the inverter 400 and the controller 600.

[0063] It can be understood that the maximum power tracking boost converter, inverter, bidirectional buck-boost converter and controller in the embodiments of the present application are components of the photovoltaic system and are not limited here.

[0064] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An insulation impedance detection circuit, characterized in that: The insulation impedance detection circuit is applied to a photovoltaic array, wherein the photovoltaic array includes at least one PV+ terminal, one PV- terminal and one PE terminal, and the insulation impedance detection circuit includes: A first sampling module, connected to a target PV+ terminal and the PV- terminal, wherein the first sampling module is configured to sample a first voltage signal between the target PV+ terminal and the PV- terminal; a second sampling module connected to the PE terminal and the PV-terminal, wherein the second sampling module is configured to adjust the insulation impedance between the PE terminal and the PV-terminal to respectively sample a second voltage signal and a third voltage signal between the PE terminal and the PV-terminal at different insulation impedances; A processing module is connected to the first sampling module and the second sampling module, and is configured to receive the first voltage signal, the second voltage signal and the third voltage signal, and output a first insulation impedance between the target PV positive terminal and the PE terminal, and a second insulation impedance between the PV negative terminal and the PE terminal.

2. The insulation impedance detection circuit according to claim 1, characterized in that: The second sampling module comprises: an impedance adjustment unit, connected to the PE terminal and the PV-terminal, wherein the impedance adjustment unit is configured to adjust the insulation impedance between the PE terminal and the PV-terminal; A first differential detection unit is connected to the PE terminal and the PV-terminal, and is configured to sample a second voltage signal and a third voltage signal between the PE terminal and the PV-terminal under different insulation impedances.

3. The insulation impedance detection circuit according to claim 2, characterized in that: The impedance adjustment unit comprises: An adjusting resistor, a first end of which is connected to the PE end; A regulating switch, wherein a first end of the regulating switch is connected to a second end of the regulating resistor, and a second end of the regulating switch is connected to the PV-end; The regulating switch is controlled to be closed or opened to adjust the insulation impedance between the PE terminal and the PV negative terminal.

4. The insulation impedance detection circuit according to claim 3, characterized in that: The regulating switch is a relay.

5. The insulation impedance detection circuit according to claim 2, characterized in that: The first differential detection unit comprises: A comparator, wherein a first input terminal of the comparator is connected to the PE terminal, a second input terminal of the comparator is connected to the PV-terminal, and an output terminal of the comparator is used to output the second voltage signal or the third voltage signal; a first resistor, wherein a first end of the first resistor is connected to a first input end of the comparator, and a second end of the first resistor is grounded; A first capacitor, wherein a first end of the first capacitor is connected to the first input end of the comparator, and a second end of the first capacitor is grounded; a second resistor, wherein a first end of the second resistor is connected to a second input end of the comparator, and a second end of the second resistor is connected to an output end of the comparator; A second capacitor, wherein a first end of the second capacitor is connected to the second input end of the comparator, and a second end of the second capacitor is connected to the output end of the comparator.

6. The insulation impedance detection circuit according to claim 5, characterized in that: The first differential detection unit further includes: a third resistor, a first end of the third resistor being connected to the PE end, and a second end of the third resistor being connected to the first input end of the comparator; A fourth resistor, a first end of the third resistor is connected to the PV-terminal, and a second end of the fourth resistor is connected to the second input terminal of the comparator.

7. The insulation impedance detection circuit according to claim 1, characterized in that: The first sampling module includes a second differential detection unit connected to a target PV+ terminal and the PV- terminal, and the second differential detection unit is configured to sample a first voltage signal between the target PV+ terminal and the PV- terminal.

8. The insulation impedance detection circuit according to claim 1, characterized in that: The insulation impedance detection circuit and the grid voltage detection circuit are arranged on the same circuit board, and the grid voltage detection circuit is configured to collect the phase voltage of the grid.

9. The insulation impedance detection circuit according to claim 8, characterized in that: The grid voltage detection circuit comprises: a third capacitor, a first end of the third capacitor being connected to the phase node to be detected; a fourth capacitor, a first end of the fourth capacitor being connected to the PE end; The third differential detection unit is connected to the second end of the third capacitor and the second end of the fourth capacitor, and the third differential detection unit is configured to collect the phase voltage to be detected.

10. A photovoltaic system, characterized in that: The photovoltaic system comprises the insulation impedance detection circuit according to any one of claims 1 to 9.

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