Insulation resistance detection circuit, control method and control device thereof and photovoltaic equipment

Abstract

The invention provides an insulation resistance detection circuit, a control method and device thereof and photovoltaic equipment, and relates to the field of photovoltaic technologies. The insulation resistance detection circuit comprises a sub-detection circuit, the sub-detection circuit comprises a positive detection resistor and a negative detection resistor, and the sub-detection circuit is used for detecting the bus voltage between a positive bus and a negative bus through the positive detection resistor and detecting the negative voltage to ground of the negative bus through the negative detection resistor; wherein the number of the sub-detection circuits is two, the two sub-detection circuits comprise a first sub-detection circuit and a second sub-detection circuit, the resistance value of the positive electrode detection resistor and the resistance value of the negative electrode detection resistor in the first sub-detection circuit are not equal, and the resistance value of the positive electrode detection resistor and the resistance value of the negative electrode detection resistor in the second sub-detection circuit are equal. According to the invention, low-cost and high-reliability insulation impedance detection is realized.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to an insulation impedance detection circuit and a control method, a control device and a photovoltaic device. Background Art

[0002] For a photovoltaic power generation system, it is necessary to ensure that the photovoltaic panels have a sufficiently large insulation impedance relative to the ground (GND) during operation, so the insulation impedance of the photovoltaic panels to the ground needs to be detected.

[0003] In the related art, the insulation impedance detection circuit used in the photovoltaic power generation system sets a detection resistor on the DC bus at the output end of the photovoltaic power generation system, and sets one or more relays, and controls one or more relays to switch the switch state through software to increase the disturbance amount, thereby realizing insulation impedance detection. Since the detection process involves software control, the detection logic is relatively complex and the hardware cost is high. In addition, when the relay fails or malfunctions, it will directly lead to the failure of the insulation impedance detection, resulting in poor reliability of the insulation impedance detection circuit. Summary of the invention

[0004] The present application aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] To this end, a first aspect of the present application provides an insulation impedance detection circuit.

[0006] A second aspect of the present application provides a photovoltaic device.

[0007] A third aspect of the present application provides a control method for an insulation impedance detection circuit.

[0008] A fourth aspect of the present application provides a control device for an insulation impedance detection circuit.

[0009] A fifth aspect of the present application provides a readable storage medium.

[0010] In view of this, the first aspect of the present application provides an insulation impedance detection circuit, which is used to detect the impedance of a DC bus to ground. The DC bus includes a positive bus and a negative bus. The insulation impedance detection circuit includes: a sub-detection circuit, the sub-detection circuit includes a positive detection resistor and a negative detection resistor, and the sub-detection circuit is used to detect the bus voltage between the positive bus and the negative bus through the positive detection resistor, and to detect the negative pole-to-ground voltage of the negative bus through the negative detection resistor; wherein the number of sub-detection circuits is two, the two sub-detection circuits include a first sub-detection circuit and a second sub-detection circuit, the resistance values ​​of the positive detection resistor and the negative detection resistor in the first sub-detection circuit are not equal, and the resistance values ​​of the positive detection resistor and the negative detection resistor in the second sub-detection circuit are equal.

[0011] In the technical solution, for example, for scenarios such as photovoltaic systems, the photovoltaic modules used as power generation modules include N-type photovoltaic modules and P-type photovoltaic modules, wherein the N-type photovoltaic modules are mainly conductive through electrons, while the P-type photovoltaic modules are conductive through holes. During use, taking the N-type photovoltaic module as an example, if the voltage passing through the cell is negative and the frame is positively biased, that is, the photovoltaic module is subjected to negative bias, the leakage anode ions flow into the cell.

[0012] When impurities appear in the semiconductor, these impurities will form a conductive channel inside the battery, and long-term high voltage of negative polarity will cause leakage current between the glass and packaging materials. Among them, the packaging materials of photovoltaic modules can be divided into external packaging materials and internal packaging materials. External packaging materials include glass backplane, TPT (Thermoplastic Polyester Elastome) backplane, aluminum frame and edge sealant, etc. Internal packaging materials include EVA (ethylene-vinyl acetate copolymer) film, PVB (Polyvinyl Butyral) film, PIB (Polyisobutylene) laminating sealant, etc.

[0013] When a large amount of charge accumulates on the surface of the battery cell, the passivation effect of the battery cell surface deteriorates, resulting in a decrease in the fill factor, short-circuit current and open-circuit voltage of the battery panel. This phenomenon is called the PID (Potential Induced Degradation) effect, which will cause the power generation of the photovoltaic system to decrease, seriously affecting the power generation of the power station. At this time, the manifestation is the reduction of the insulation impedance to the ground of the DC bus of the photovoltaic power generation component. Therefore, it is necessary to monitor the insulation impedance to the ground of the DC bus in real time and intervene as soon as the insulation impedance to the ground is detected to be reduced.

[0014] The present application proposes an asymmetric insulation impedance detection circuit that does not require a signal relay. When performing insulation impedance detection through the insulation impedance detection circuit, there is no need to set up a complex software control process of the switch device. Since there is no need to set up a switch device, it is possible to avoid insulation impedance detection failure caused by failure of the switch device, thereby achieving low-cost, high-reliability insulation impedance detection. The specific implementation of the insulation impedance detection circuit of the present application is described in detail below.

[0015] Exemplarily, the insulation impedance of the positive bus in the bus voltage to the ground is Rins+, and the insulation impedance of the negative bus in the bus voltage to the ground is Rins-. When performing insulation impedance detection, the voltage value of the positive bus to the negative bus, that is, the bus voltage Vpv of the DC bus, and the voltage value of the negative bus to the ground, that is, the negative voltage to the ground Vg, are sampled. The insulation impedance of the positive bus to the ground Rins+ and the insulation impedance of the negative bus to the ground Rins- are determined based on the bus voltage Vpv and the negative voltage to the ground Vg.

[0016] At this time, the calculation is performed using the following formula (1):

[0017]

[0018] Among them, Vpv is the bus voltage, Vg is the negative electrode to ground voltage, R1 is the positive electrode detection resistor, R2 is the negative electrode detection resistor, R7 is the second resistor, and R5, R6, R7, R8 and R9 are constants.

[0019] The selection of positive and negative detection resistors is the key to the insulation impedance detection circuit. When the positive detection resistor and the negative detection resistor are equal, the sub-detection circuit is generally recorded as a symmetrical detection circuit, and when the positive detection resistor and the negative detection resistor are not equal, the sub-detection circuit is considered to be an asymmetrical detection circuit.

[0020] Assuming that the positive electrode detection resistor is R1 and the negative electrode detection resistor is R2, then in the symmetrical detection circuit, that is, in the second sub-detection circuit mentioned above, R1 = R2. The changes in the insulation impedance Rins+ of the positive busbar to the ground and the insulation impedance Rins- of the negative busbar to the ground can be divided into the following three cases:

[0021] Case 1: The insulation impedance Rins+ of the positive busbar to ground changes, while the insulation impedance Rins- of the negative busbar to ground remains unchanged (the resistance value of Rins- is assumed to be infinite in this case);

[0022] Case 2: The insulation impedance Rins+ of the positive busbar to the ground remains unchanged, while the insulation impedance Rins- of the negative busbar to the ground changes;

[0023] In case three, the insulation impedance Rins+ of the positive busbar to ground and the insulation impedance Rins- of the negative busbar to ground both change.

[0024] At this time, for the second sub-detection circuit, in case one, the larger Rins+ is, the smaller the negative bus voltage to ground sampling value is. In case two, the larger Rins- is, the larger the negative bus voltage to ground sampling value is. In case three, Rins+ and Rins- change at the same time, and the negative bus voltage to ground sampling value remains basically unchanged. Since the negative bus voltage to ground sampling value does not change basically when Rins+ and Rins- change at the same time, the insulation impedance value cannot be calculated by calculating the difference between the bus voltage Vpv of the DC bus and the negative voltage to ground Vg to infer the insulation impedance Rins+ of the positive bus and the insulation impedance Rins- of the negative bus.

[0025] In response to the above problems, the present application adds an asymmetric detection circuit, that is, the above-mentioned first sub-detection circuit. In the first sub-detection circuit, R1≠R2. Assume that R1=k×R2, where k is the proportional coefficient, for example, k is 10 / 7. For the asymmetric first sub-detection circuit, in the above-mentioned cases 1, 2, and 3, the insulation impedance Rins+ of the positive bus to ground and the insulation impedance Rins- of the negative bus to ground can be calculated by the difference between the collected bus voltage Vpv of the DC bus and the negative voltage to ground Vg.

[0026] If only an asymmetric detection circuit is set, then in a specific case, for example, when k is 10 / 7 and R1=10 / 7×R2, ​​if Rins+=10 / 7×Rins-, it will result in R1×Rins-=R2×Rins+. At this time, it can be inferred from the above formula (1) that the difference between the bus voltage and the negative bus voltage sampling value remains basically unchanged.

[0027] In this regard, an asymmetric detection circuit and a symmetrical detection circuit are simultaneously provided in the present application, that is, the first sub-detection circuit and the second sub-detection circuit mentioned above, and insulation detection is performed on the bus circuit respectively through the two sub-detection circuits. When the insulation impedance to the ground detected by the two sub-detection circuits meets the requirements, it is confirmed that the insulation of the equipment to the ground is normal, otherwise it is considered that the insulation of the equipment to the ground is abnormal.

[0028] The insulation impedance detection circuit proposed in the embodiment of the present application does not need to set up a complex software control process of the switching device, and since there is no need to set up a switching device, it can avoid the failure of insulation impedance detection caused by failure of the switching device, thereby realizing low-cost and high-reliability insulation impedance detection.

[0029] In addition, the insulation impedance detection circuit in the above technical solution provided by the present application may also have the following additional technical features:

[0030] In some technical solutions of the present application, optionally, the insulation impedance detection circuit further includes: a controller, the controller is electrically connected to the first sub-detection circuit and the second sub-detection circuit, and the controller is used to:

[0031] Determine first impedance detection information based on the first bus voltage and the first negative pole voltage to ground; wherein the first bus voltage and the first negative pole voltage to ground are detected by a first sub-detection circuit; determine second impedance detection information based on the second bus voltage and the second negative pole voltage to ground; wherein the second bus voltage and the second negative pole voltage to ground are detected by a second sub-detection circuit; and, determine the insulation impedance detection result of the DC bus based on the first impedance detection information and the second impedance detection information.

[0032] In this technical solution, the first sub-detection circuit is an asymmetric detection circuit, and the second sub-detection circuit is a symmetric detection circuit. Among them, for the second sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in scenarios other than when the insulation impedance of the positive bus to the ground Rins+ and the insulation impedance of the negative bus to the ground Rins- change simultaneously. For the first sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in all scenarios except when R1×Rins-=R2×Rins+ is satisfied.

[0033] The present application combines the first sub-detection circuit and the second sub-detection circuit, and detects the first bus voltage Vpv1 and the first negative electrode to ground voltage Vg1 through the first sub-detection circuit, and calculates Rins1+ and Rins1- using the above formula (1). Similarly, detects the second bus voltage Vpv2 and the second negative electrode to ground voltage Vg2 through the second sub-detection circuit, and calculates Rins2+ and Rins2- using the above formula (1).

[0034] Among them, Rins1+ and Rins1- are the above-mentioned first impedance detection information, and Rins2+ and Rins2- are the above-mentioned second impedance detection information.

[0035] The insulation impedance detection result of the DC bus is determined by comparing the first detection information and the second detection information to see whether both meet the ground insulation impedance threshold required for safe and stable operation of the system.

[0036] Exemplarily, when both the first detection information and the second detection information meet the above-mentioned ground insulation impedance threshold, it is determined whether the detection result meets the requirement. When either the first detection information or the second detection information does not meet the above-mentioned ground insulation impedance threshold, it is determined that the detection result does not meet the requirement.

[0037] The present application combines a symmetrical detection circuit and an asymmetrical detection circuit, and can ensure that the detection result of the insulation impedance to ground is accurate and reliable under any circumstances.

[0038] In some technical solutions of the present application, optionally, the sub-detection circuit includes: a positive detection resistor, a first end of the positive detection resistor is electrically connected to the positive bus, and a second end of the positive detection resistor is grounded; a first comparator, a first input end of the first comparator is electrically connected to the negative bus, a second input end of the first comparator is electrically connected to the first end of the positive detection resistor, and an output end of the first comparator is used to output the bus voltage.

[0039] In this technical solution, the positive electrode detection resistor is R1, one end of the positive electrode detection resistor is connected to the positive electrode bus, and the other end is grounded and connected to the first input terminal (input positive electrode) of the first comparator. The second input terminal (input negative electrode) of the first comparator is connected to the negative electrode bus through a voltage divider resistor. Through the above simple circuit structure, the insulation impedance of the DC bus to the ground can be accurately detected without setting additional switching devices, which simplifies the structure of the insulation impedance detection circuit and improves the reliability of the insulation impedance detection circuit.

[0040] In some technical solutions of the present application, optionally, the sub-detection circuit also includes: a first capacitor, a first end of the first capacitor is electrically connected to the second input end of the first comparator, and a second end of the first capacitor is electrically connected to the negative bus; a first resistor, and the first resistor is connected in parallel with the first capacitor.

[0041] In this technical solution, a first capacitor and a first resistor connected in parallel are arranged between the first input terminal of the first comparator and the positive electrode detection resistor, which can reliably absorb the noise signal in the circuit and improve the detection accuracy.

[0042] In some technical solutions of the present application, optionally, the sub-detection circuit also includes: a negative electrode detection resistor, a first end of the negative electrode detection resistor is grounded; a second comparator, a first input end of the second comparator is electrically connected to the negative electrode bus, a second input end of the second comparator is electrically connected to the second end of the negative electrode detection resistor, and an output end of the second comparator is used to output a negative electrode voltage to ground.

[0043] In this technical solution, the negative electrode detection resistor is R2, one end of the negative electrode detection resistor is connected to the negative electrode bus, the other end is grounded, and connected to the first input terminal (input positive electrode) of the second comparator. The second input terminal (input negative electrode) of the second comparator is connected to the negative electrode bus through a voltage divider resistor. Through the above simple circuit structure, the insulation impedance of the DC bus to the ground can be accurately detected without setting additional switching devices, which simplifies the structure of the insulation impedance detection circuit and improves the reliability of the insulation impedance detection circuit.

[0044] In some technical solutions of the present application, optionally, the sub-detection circuit also includes: a second capacitor, a first end of the second capacitor is electrically connected to the second input end of the second comparator, and a second end of the second capacitor is electrically connected to the negative bus; a second resistor, and the second resistor is connected in parallel to the second capacitor.

[0045] In this technical solution, a second capacitor and a second resistor connected in parallel are arranged between the second input terminal of the second comparator and the positive electrode detection resistor, which can reliably absorb the noise signal in the circuit and improve the detection accuracy.

[0046] The second aspect of the present application provides a photovoltaic device, including: a photovoltaic power generation component, the output end of the photovoltaic power generation component is electrically connected to a DC bus; an insulation impedance detection circuit as provided in any of the above technical solutions, the insulation impedance detection circuit is electrically connected to the DC bus, and is used to detect the impedance of the DC bus to ground.

[0047] In this technical solution, the photovoltaic device includes the insulation impedance detection circuit provided in any of the above technical solutions, and therefore also includes all the beneficial effects of the insulation impedance detection circuit provided in any of the above technical solutions, which will not be described again to avoid repetition.

[0048] In a third aspect, the present application provides a control method for an insulation impedance detection circuit, wherein the insulation impedance detection circuit includes a first sub-detection circuit and a second sub-detection circuit, wherein the resistance values ​​of the positive electrode detection resistor and the negative electrode detection resistor in the first sub-detection circuit are not equal, and the resistance values ​​of the positive electrode detection resistor and the negative electrode detection resistor in the second sub-detection circuit are equal; the control method includes:

[0049] Obtain a first bus voltage, a first negative pole-to-ground voltage, a second bus voltage, and a second negative pole-to-ground voltage of a DC bus; wherein the first bus voltage and the first negative pole-to-ground voltage are detected by a first sub-detection circuit, and the second bus voltage and the second negative pole-to-ground voltage are detected by a second sub-detection circuit; determine first impedance detection information according to the first bus voltage and the first negative pole-to-ground voltage, and determine second impedance detection information according to the second bus voltage and the second negative pole-to-ground voltage; determine an insulation impedance detection result of the DC bus based on the first impedance detection information and the second impedance detection information.

[0050] In this technical solution, the first sub-detection circuit is an asymmetric detection circuit, and the second sub-detection circuit is a symmetric detection circuit. Among them, for the second sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in scenarios other than when the insulation impedance of the positive bus to the ground Rins+ and the insulation impedance of the negative bus to the ground Rins- change simultaneously. For the first sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in all scenarios except when R1×Rins-=R2×Rins+ is satisfied.

[0051] The present application combines the first sub-detection circuit and the second sub-detection circuit, and detects the first bus voltage Vpv1 and the first negative electrode to ground voltage Vg1 through the first sub-detection circuit, and calculates Rins1+ and Rins1- using the above formula (1). Similarly, detects the second bus voltage Vpv2 and the second negative electrode to ground voltage Vg2 through the second sub-detection circuit, and calculates Rins2+ and Rins2- using the above formula (1).

[0052] Among them, Rins1+ and Rins1- are the above-mentioned first impedance detection information, and Rins2+ and Rins2- are the above-mentioned second impedance detection information.

[0053] The insulation impedance detection result of the DC bus is determined by comparing the first detection information and the second detection information to see whether both meet the ground insulation impedance threshold required for safe and stable operation of the system.

[0054] The present application combines a symmetrical detection circuit and an asymmetrical detection circuit, and can ensure that the detection result of the insulation impedance to ground is accurate and reliable under any circumstances.

[0055] In some technical solutions of the present application, optionally, based on the first impedance detection information and the second impedance detection information, an insulation impedance detection result of the DC bus is determined, including: when the first impedance detection information and the second impedance detection information both meet the insulation detection conditions of the DC bus, determining that the insulation impedance detection result is through the insulation detection; or, when either the first impedance detection information or the second impedance detection information does not meet the insulation detection conditions of the DC bus, determining that the insulation impedance detection result is not through the insulation detection.

[0056] In this technical solution, let the positive electrode detection resistor be R1 and the negative electrode detection resistor be R2. For the symmetrical detection circuit, that is, in the second sub-detection circuit mentioned above, R1=R2, and for the asymmetrical detection circuit, that is, in the first sub-detection circuit mentioned above, R1≠R2. For the second sub-detection circuit, Rins+ and Rins- change at the same time, and the negative bus voltage to ground sampling value remains basically unchanged. For the first sub-detection circuit, under certain circumstances, if R1×Rins-=R2×Rins+ is just satisfied, the difference between the bus voltage and the negative bus voltage to ground sampling value remains basically unchanged.

[0057] In this regard, an asymmetric detection circuit and a symmetrical detection circuit are simultaneously provided in the present application, that is, the first sub-detection circuit and the second sub-detection circuit mentioned above, and insulation detection is performed on the bus circuit respectively through the two sub-detection circuits. When the insulation impedance to the ground detected by the two sub-detection circuits meets the requirements, it is confirmed that the insulation of the equipment to the ground is normal, otherwise it is considered that the insulation of the equipment to the ground is abnormal.

[0058] Exemplarily, when both the first detection information and the second detection information meet the above-mentioned ground insulation impedance threshold, it is determined whether the detection result meets the requirement. When either the first detection information or the second detection information does not meet the above-mentioned ground insulation impedance threshold, it is determined that the detection result does not meet the requirement.

[0059] The present application realizes accurate and reliable insulation impedance detection to ground by combining an asymmetric detection circuit and a symmetric detection circuit without setting a switching device and complex switch control logic.

[0060] In a fourth aspect, the present application provides a control device for an insulation impedance detection circuit, comprising: a memory for storing programs or instructions; a processor for implementing a control method for an insulation impedance detection circuit as in any of the above-mentioned technical solutions when executing the programs or instructions, and therefore also including all the beneficial effects of the control method for an insulation impedance detection circuit as in any of the above-mentioned technical solutions, which will not be described again here to avoid repetition.

[0061] In a fifth aspect, the present application provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, a control method for an insulation impedance detection circuit as in any of the above-mentioned technical solutions is implemented. Therefore, all the beneficial effects of the control method for an insulation impedance detection circuit as in any of the above-mentioned technical solutions are also included. To avoid repetition, they will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0063] Figure 1 A circuit diagram showing an insulation impedance detection circuit of some embodiments of the present application;

[0064] Figure 2 A circuit diagram showing a first sub-detection circuit of some embodiments of the present application;

[0065] Figure 3 A circuit diagram showing a second sub-detection circuit of some embodiments of the present application;

[0066] Figure 4 A flow chart showing a control method of an insulation impedance detection circuit in some embodiments of the present application;

[0067] Figure 5 A structural block diagram of a control device of an insulation impedance detection circuit in some embodiments of the present application is shown.

[0068] Reference numerals:

[0069] 10 insulation impedance detection circuit, R1 positive detection resistor, R2 negative detection resistor, 102 first sub-detection circuit, 104 second sub-detection circuit, 106 controller, Q1 first comparator, C1 first capacitor, R4 first resistor, Q2 second comparator, C2 second capacitor, R7 second resistor, PV+ positive bus, PV- negative bus. DETAILED DESCRIPTION

[0070] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0071] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present application is not limited to the specific embodiments disclosed below.

[0072] Refer to the following Figures 1 to 5 An insulation impedance detection circuit and a control method, a control device, and a photovoltaic device provided according to some embodiments of the present application are described.

[0073] In some embodiments of the present application, an insulation impedance detection circuit is provided. Figure 1 A circuit diagram of an insulation impedance detection circuit according to some embodiments of the present application is shown. Figure 2 A circuit diagram of a first sub-detection circuit of some embodiments of the present application is shown, Figure 3 A circuit diagram of a second sub-detection circuit of some embodiments of the present application is shown, such as Figure 1 , Figure 2 and Figure 3 As shown, the insulation impedance detection circuit 10 is used to detect the impedance of the DC bus to ground, the DC bus includes a positive bus and a negative bus, and the insulation impedance detection circuit 10 includes:

[0074] A sub-detection circuit, the sub-detection circuit includes a positive detection resistor R1 and a negative detection resistor R2, and the sub-detection circuit is used to detect the bus voltage between the positive bus PV+ and the negative bus PV- through the positive detection resistor R1, and to detect the negative pole-to-ground voltage of the negative bus PV- through the negative detection resistor R2; wherein, the number of sub-detection circuits is two, and the two sub-detection circuits include a first sub-detection circuit 102 and a second sub-detection circuit 104, the resistance values ​​of the positive detection resistor R1 and the negative detection resistor R2 in the first sub-detection circuit 102 are not equal, and the resistance values ​​of the positive detection resistor R1 and the negative detection resistor R2 in the second sub-detection circuit 104 are equal.

[0075] In this embodiment, for example, for a scenario such as a photovoltaic system, the photovoltaic components used as power generation components include N-type photovoltaic components and P-type photovoltaic components, wherein the N-type photovoltaic components are mainly conductive through electrons, while the P-type photovoltaic components are conductive through holes. During use, taking the N-type photovoltaic component as an example, if the voltage passing through the cell is negative and the frame is positively biased, that is, the photovoltaic component is subjected to a negative bias, the leakage anode ions flow into the cell.

[0076] When impurities appear in the semiconductor, these impurities will form a conductive channel inside the battery, and long-term high voltage of negative polarity will cause leakage current between the glass and packaging materials. Among them, the packaging materials of photovoltaic modules can be divided into external packaging materials and internal packaging materials. External packaging materials include glass backplane, TPT (Thermoplastic Polyester Elastome) backplane, aluminum frame and edge sealant, etc. Internal packaging materials include EVA (ethylene-vinyl acetate copolymer) film, PVB (Polyvinyl Butyral) film, PIB (Polyisobutylene) laminating sealant, etc.

[0077] When a large amount of charge accumulates on the surface of the battery cell, the passivation effect of the battery cell surface deteriorates, resulting in a decrease in the fill factor, short-circuit current and open-circuit voltage of the battery panel. This phenomenon is called the PID (Potential Induced Degradation) effect, which will cause the power generation of the photovoltaic system to decrease, seriously affecting the power generation of the power station. At this time, the manifestation is the reduction of the insulation impedance to the ground of the DC bus of the photovoltaic power generation component. Therefore, it is necessary to monitor the insulation impedance to the ground of the DC bus in real time and intervene as soon as the insulation impedance to the ground is detected to be reduced.

[0078] The present application proposes an asymmetric insulation impedance detection circuit 10 that does not require a signal relay. When performing insulation impedance detection through the insulation impedance detection circuit 10, there is no need to set up a complex software control process of the switch device. Since there is no need to set up a switch device, it is possible to avoid insulation impedance detection failure caused by failure of the switch device, thereby achieving low-cost, high-reliability insulation impedance detection. The specific implementation of the insulation impedance detection circuit 10 of the present application is described in detail below.

[0079] For example, Figure 1As shown, let PV+ be the positive bus PV+, PV- be the negative bus PV-, let the insulation resistance of the positive bus PV+ to the ground in the bus voltage be Rins+, let the insulation resistance of the negative bus PV- to the ground in the bus voltage be Rins-. When performing insulation resistance detection, the voltage value of the positive bus PV+ to the negative bus PV-, that is, the bus voltage Vpv of the DC bus, and the voltage value of the negative bus PV- to the ground, that is, the negative voltage to the ground Vg, are sampled. According to the bus voltage Vpv and the negative voltage to the ground Vg, the insulation resistance of the positive bus PV+ to the ground Rins+ and the insulation resistance of the negative bus PV- to the ground Rins- are determined.

[0080] At this time, the calculation is performed using the following formula (1):

[0081]

[0082] Among them, Vpv is the bus voltage, Vg is the negative pole to ground voltage, R1 is the positive pole detection resistor, R2 is the negative pole detection resistor, R5, R6, R7, R8 and R9 are Figure 1 The resistors shown in , and R5, R6, R7, R8 and R9 are constants.

[0083] The selection of the positive electrode detection resistor R1 and the negative electrode detection resistor R2 is the key to the insulation impedance detection circuit 10. When the positive electrode detection resistor R1 and the negative electrode detection resistor R2 are equal, the sub-detection circuit is generally recorded as a symmetrical detection circuit, and when the positive electrode detection resistor and the negative electrode detection resistor R2 are not equal, the sub-detection circuit is considered to be an asymmetrical detection circuit.

[0084] Assuming that the positive electrode detection resistor is R1 and the negative electrode detection resistor is R2, then in the symmetrical detection circuit, that is, in the second sub-detection circuit 104, R1=R2. The changes in the insulation impedance Rins+ of the positive bus PV+ to the ground and the insulation impedance Rins- of the negative bus PV- to the ground can be divided into the following three cases:

[0085] Case 1: The insulation impedance Rins+ of the positive bus PV+ to the ground changes, while the insulation impedance Rins- of the negative bus PV- to the ground remains unchanged (the resistance value of Rins- is assumed to be infinite in this case);

[0086] In case 2, the insulation impedance Rins+ of the positive bus PV+ to the ground remains unchanged, while the insulation impedance Rins- of the negative bus PV- to the ground changes;

[0087] In case three, the insulation impedance Rins+ of the positive bus PV+ to ground and the insulation impedance Rins- of the negative bus PV- to ground both change.

[0088] At this time, for the second sub-detection circuit 104, in case 1, the larger Rins+ is, the smaller the negative bus PV-to-ground voltage sampling value is. In case 2, the larger Rins- is, the larger the negative bus PV-to-ground voltage sampling value is. In case 3, Rins+ and Rins- change at the same time, and the negative bus PV-to-ground voltage sampling value remains basically unchanged. The detection data of the second sub-detection circuit 104 is specifically shown in Table 1 below:

[0089] Table 1

[0090]

[0091] Since the PV-to-ground voltage sampling value basically does not change when Rins+ and Rins- change at the same time, the insulation impedance value cannot be calculated by calculating the difference between the bus voltage Vpv of the DC bus and the negative voltage to ground Vg to infer the insulation impedance Rins+ of the positive bus PV+ and the insulation impedance Rins- of the negative bus PV-.

[0092] To solve the above problem, the present application adds an asymmetric detection circuit, namely the first sub-detection circuit 102. In the first sub-detection circuit 102, R1≠R2. Assuming R1=k×R2, where k is a proportionality coefficient, for example, k is 10 / 7, the data of the first sub-detection circuit 102 is shown in Table 2 below:

[0093] Table 2

[0094]

[0095] As shown in Table 2, for the asymmetric first sub-detection circuit 102, in the above-mentioned cases 1, 2 and 3, the insulation impedance Rins+ of the positive bus PV+ to the ground and the insulation impedance Rins- of the negative bus PV- to the ground can be inferred by the difference between the collected bus voltage Vpv of the DC bus and the negative pole voltage to the ground Vg.

[0096] If only an asymmetric detection circuit is set, then in a specific case, for example, when k is 10 / 7 and R1=10 / 7×R2, ​​if Rins+=10 / 7×Rins- is satisfied, it will result in R1×Rins-=R2×Rins+. At this time, it can be inferred from the above formula (1) that the difference between the bus voltage and the negative bus PV-to-ground voltage sampling value remains basically unchanged.

[0097] In this regard, an asymmetric detection circuit and a symmetrical detection circuit are simultaneously provided in the present application, namely, the first sub-detection circuit 102 and the second sub-detection circuit 104 mentioned above. The insulation of the bus circuit is detected by the two sub-detection circuits respectively. When the insulation impedance to the ground detected by the two sub-detection circuits meets the requirements, it is confirmed that the insulation of the equipment to the ground is normal; otherwise, it is considered that the insulation of the equipment to the ground is abnormal.

[0098] The insulation impedance detection circuit 10 proposed in the embodiment of the present application does not need to set up a complex software control process of the switching device, and since there is no need to set up a switching device, it can avoid the failure of insulation impedance detection caused by failure of the switching device, thereby realizing low-cost and high-reliability insulation impedance detection.

[0099] In addition, the insulation impedance detection circuit 10 in the above embodiment provided by the present application may also have the following additional technical features:

[0100] In some embodiments of the present application, optionally, the insulation impedance detection circuit 10 further includes: a controller 106, the controller 106 is electrically connected to the first sub-detection circuit 102 and the second sub-detection circuit 104, and the controller 106 is used to:

[0101] According to the first bus voltage and the first negative pole voltage to ground, first impedance detection information is determined; wherein the first bus voltage and the first negative pole voltage to ground are detected by the first sub-detection circuit 102; according to the second bus voltage and the second negative pole voltage to ground, second impedance detection information is determined; wherein the second bus voltage and the second negative pole voltage to ground are detected by the second sub-detection circuit 104; and, based on the first impedance detection information and the second impedance detection information, the insulation impedance detection result of the DC bus is determined.

[0102] In this embodiment, the first sub-detection circuit 102 is an asymmetric detection circuit, and the second sub-detection circuit 104 is a symmetric detection circuit. Among them, for the second sub-detection circuit 104, it can accurately detect the insulation impedance to ground of the DC bus except for the scenario where the insulation impedance to ground Rins+ of the positive bus PV+ and the insulation impedance to ground Rins- of the negative bus PV- change simultaneously. For the first sub-detection circuit 102, it can accurately detect the insulation impedance to ground of the DC bus in all scenarios except satisfying R1×Rins-=R2×Rins+.

[0103] The present application combines the first sub-detection circuit 102 and the second sub-detection circuit 104, and detects the first bus voltage Vpv1 and the first negative electrode to ground voltage Vg1 through the first sub-detection circuit 102, and uses the above formula (1) to calculate Rins1+ and Rins1-. Similarly, the second bus voltage Vpv2 and the second negative electrode to ground voltage Vg2 are detected by the second sub-detection circuit 104, and the above formula (1) is used to calculate Rins2+ and Rins2-.

[0104] Among them, Rins1+ and Rins1- are the above-mentioned first impedance detection information, and Rins2+ and Rins2- are the above-mentioned second impedance detection information.

[0105] The insulation impedance detection result of the DC bus is determined by comparing the first detection information and the second detection information to see whether both meet the ground insulation impedance threshold required for safe and stable operation of the system.

[0106] Exemplarily, when both the first detection information and the second detection information meet the above-mentioned ground insulation impedance threshold, it is determined whether the detection result meets the requirement. When either the first detection information or the second detection information does not meet the above-mentioned ground insulation impedance threshold, it is determined that the detection result does not meet the requirement.

[0107] The present application combines a symmetrical detection circuit and an asymmetrical detection circuit, and can ensure that the detection result of the insulation impedance to ground is accurate and reliable under any circumstances.

[0108] In some embodiments of the present application, optionally, the sub-detection circuit includes: a positive detection resistor R1, a first end of the positive detection resistor R1 is electrically connected to the positive bus PV+, and a second end of the positive detection resistor R1 is grounded; a first comparator Q1, a first input end of the first comparator Q1 is electrically connected to the negative bus PV-, a second input end of the first comparator Q1 is electrically connected to the first end of the positive detection resistor R1, and an output end of the first comparator Q1 is used to output the bus voltage.

[0109] In this embodiment, the positive electrode detection resistor is R1, one end of the positive electrode detection resistor R1 is connected to the positive electrode bus PV+, the other end is grounded, and connected to the first input terminal (input positive electrode) of the first comparator Q1. The second input terminal (input negative electrode) of the first comparator Q1 is connected to the negative electrode bus PV- through a voltage divider resistor. Through the above simple circuit structure, the insulation impedance of the DC bus to the ground can be accurately detected without setting additional switching devices, which simplifies the structure of the insulation impedance detection circuit 10 and improves the reliability of the insulation impedance detection circuit 10.

[0110] In some embodiments of the present application, optionally, the sub-detection circuit also includes: a first capacitor C1, a first end of the first capacitor C1 is electrically connected to the second input end of the first comparator Q1, and a second end of the first capacitor C1 is electrically connected to the negative bus PV-; a first resistor R4, and the first resistor R4 is connected in parallel to the first capacitor C1.

[0111] In this embodiment, a first capacitor C1 and a first resistor R4 connected in parallel are provided between the first input terminal of the first comparator Q1 and the positive electrode detection resistor R1, which can reliably absorb the noise signal in the circuit and improve the detection accuracy.

[0112] In some embodiments of the present application, optionally, the sub-detection circuit also includes: a negative electrode detection resistor R2, a first end of the negative electrode detection resistor R2 is grounded; a second comparator Q2, a first input end of the second comparator Q2 is electrically connected to the negative electrode bus PV-, a second input end of the second comparator Q2 is electrically connected to the second end of the negative electrode detection resistor R2, and an output end of the second comparator Q2 is used to output a negative electrode voltage to ground.

[0113] In this embodiment, the negative electrode detection resistor is R2, one end of the negative electrode detection resistor R2 is connected to the negative electrode bus PV-, the other end is grounded, and is connected to the first input terminal (input positive electrode) of the second comparator Q2 through the resistor R6. At the same time, the first input terminal of the second comparator Q2 is connected to the negative electrode bus PV- through the resistor R6 and the filter capacitor C3. The second input terminal (input negative electrode) of the second comparator Q2 is connected to the negative electrode bus PV- through a voltage divider resistor. Through the above simple circuit structure, the insulation impedance of the DC bus to the ground can be accurately detected without setting additional switching devices, which simplifies the structure of the insulation impedance detection circuit 10 and improves the reliability of the insulation impedance detection circuit 10.

[0114] In some embodiments of the present application, optionally, the sub-detection circuit also includes: a second capacitor C2, a first end of the second capacitor C2 is electrically connected to the second input end of the second comparator Q2, and a second end of the second capacitor C2 is electrically connected to the negative bus PV-; a second resistor R7, and the second resistor R7 is connected in parallel to the second capacitor C2.

[0115] In this embodiment, a second capacitor C2 and a second resistor R7 are provided in parallel between the second input terminal of the second comparator Q2 and the positive electrode detection resistor R1, which can reliably absorb the noise signal in the circuit and improve the detection accuracy.

[0116] In some embodiments of the present application, a photovoltaic device is provided, including: a photovoltaic power generation component, the output end of the photovoltaic power generation component is electrically connected to a DC bus; an insulation impedance detection circuit as provided in any of the above embodiments, the insulation impedance detection circuit is electrically connected to the DC bus, and is used to detect the impedance of the DC bus to ground.

[0117] In this embodiment, the photovoltaic device includes the insulation impedance detection circuit provided in any of the above embodiments, and therefore also includes all the beneficial effects of the insulation impedance detection circuit provided in any of the above embodiments, which will not be described again to avoid repetition.

[0118] In some embodiments of the present application, a control method for an insulation impedance detection circuit is provided, wherein the insulation impedance detection circuit includes a first sub-detection circuit and a second sub-detection circuit, wherein the resistance values ​​of the positive detection resistor and the negative detection resistor in the first sub-detection circuit are not equal, and the resistance values ​​of the positive detection resistor and the negative detection resistor in the second sub-detection circuit are equal.

[0119] Figure 4 A flow chart showing a control method of an insulation impedance detection circuit in some embodiments of the present application is shown. Figure 4 As shown, the control method includes:

[0120] Step 402, obtaining a first bus voltage, a first negative pole-to-ground voltage, a second bus voltage, and a second negative pole-to-ground voltage of a DC bus; wherein the first bus voltage and the first negative pole-to-ground voltage are obtained by detecting a first sub-detection circuit, and the second bus voltage and the second negative pole-to-ground voltage are obtained by detecting a second sub-detection circuit;

[0121] Step 404, determining first impedance detection information according to the first bus voltage and the first negative electrode-to-ground voltage, and determining second impedance detection information according to the second bus voltage and the second negative electrode-to-ground voltage;

[0122] Step 406: Determine the insulation impedance detection result of the DC bus based on the first impedance detection information and the second impedance detection information.

[0123] In this embodiment, the first sub-detection circuit is an asymmetric detection circuit, and the second sub-detection circuit is a symmetric detection circuit. Among them, for the second sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in the scenario other than the insulation impedance of the positive bus to the ground Rins+ and the insulation impedance of the negative bus to the ground Rins- changes simultaneously. For the first sub-detection circuit, it can accurately detect the insulation impedance of the DC bus to the ground in all scenarios except satisfying R1×Rins-=R2×Rins+.

[0124] The present application combines the first sub-detection circuit and the second sub-detection circuit, and detects the first bus voltage Vpv1 and the first negative electrode to ground voltage Vg1 through the first sub-detection circuit, and calculates Rins1+ and Rins1- using the above formula (1). Similarly, detects the second bus voltage Vpv2 and the second negative electrode to ground voltage Vg2 through the second sub-detection circuit, and calculates Rins2+ and Rins2- using the above formula (1).

[0125] Among them, Rins1+ and Rins1- are the above-mentioned first impedance detection information, and Rins2+ and Rins2- are the above-mentioned second impedance detection information.

[0126] The insulation impedance detection result of the DC bus is determined by comparing the first detection information and the second detection information to see whether both meet the ground insulation impedance threshold required for safe and stable operation of the system.

[0127] The present application combines a symmetrical detection circuit and an asymmetrical detection circuit, and can ensure that the detection result of the insulation impedance to ground is accurate and reliable under any circumstances.

[0128] In some embodiments of the present application, optionally, based on the first impedance detection information and the second impedance detection information, an insulation impedance detection result of the DC bus is determined, including: when the first impedance detection information and the second impedance detection information both meet the insulation detection conditions of the DC bus, determining that the insulation impedance detection result is through the insulation detection; or, when either the first impedance detection information or the second impedance detection information does not meet the insulation detection conditions of the DC bus, determining that the insulation impedance detection result is not through the insulation detection.

[0129] In this embodiment, assuming that the positive electrode detection resistor is R1 and the negative electrode detection resistor is R2, then for the symmetrical detection circuit, that is, in the second sub-detection circuit mentioned above, R1=R2, and for the asymmetrical detection circuit, that is, in the first sub-detection circuit mentioned above, R1≠R2. For the second sub-detection circuit, Rins+ and Rins- change at the same time, and the negative bus voltage to ground sampling value remains basically unchanged. For the first sub-detection circuit, under certain circumstances, if R1×Rins-=R2×Rins+ is just satisfied, the difference between the bus voltage and the negative bus voltage to ground sampling value remains basically unchanged.

[0130] In this regard, an asymmetric detection circuit and a symmetrical detection circuit are simultaneously provided in the present application, that is, the first sub-detection circuit and the second sub-detection circuit mentioned above, and insulation detection is performed on the bus circuit respectively through the two sub-detection circuits. When the insulation impedance to the ground detected by the two sub-detection circuits meets the requirements, it is confirmed that the insulation of the equipment to the ground is normal, otherwise it is considered that the insulation of the equipment to the ground is abnormal.

[0131] Exemplarily, when both the first detection information and the second detection information meet the above-mentioned ground insulation impedance threshold, it is determined whether the detection result meets the requirements. When any one of the first detection information and the second detection information does not meet the above-mentioned ground insulation impedance threshold, it is determined that the detection result does not meet the requirements. Specifically, as shown in Table 3:

[0132] Table 3

[0133]

[0134] The present application realizes accurate and reliable insulation impedance detection to ground by combining an asymmetric detection circuit and a symmetric detection circuit without setting a switching device and complex switch control logic.

[0135] In some embodiments of the present application, a control device for an insulation impedance detection circuit is provided. Figure 5 The structure block diagram of the control device of the insulation impedance detection circuit of some embodiments of the present application is shown as follows: Figure 5 As shown, the control device 500 of the insulation impedance detection circuit includes: a memory 502, which is used to store programs or instructions; a processor 504, which is used to implement the control method of the insulation impedance detection circuit in any of the above embodiments when executing the programs or instructions, and therefore also includes all the beneficial effects of the control method of the insulation impedance detection circuit in any of the above embodiments, which will not be repeated here to avoid repetition.

[0136] In some embodiments of the present application, a readable storage medium is provided, on which a program or instruction is stored. When the program or instruction is executed by a processor, a control method for an insulation impedance detection circuit as in any of the above embodiments is implemented. Therefore, all the beneficial effects of the control method for an insulation impedance detection circuit as in any of the above embodiments are also included. To avoid repetition, they are not repeated here.

[0137] The methods may be implemented in a variety of different ways depending on the specific features and / or example applications. For example, the methods may be implemented by a combination of hardware, firmware, and / or software. For example, in a hardware implementation, the processor may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), controllers, microcontrollers, microprocessors, electronic devices, other device units for performing the above functions, and / or combinations thereof.

[0138] A computer readable storage medium may be a tangible device that can retain and store instructions for use by an instruction execution device. A computer readable storage medium may be an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the above devices, but is not limited thereto. A non-exhaustive list of more specific examples of computer readable storage media includes: portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital versatile disk (DVD), memory card, floppy disk, encoding mechanical device (such as a punch card or a groove with a raised structure with instructions recorded) and any suitable combination of the above devices. The computer readable storage medium used herein should not be understood as a transmission signal itself, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium, or an electrical signal transmitted through a wire, etc.

[0139] In the description of this application, the term "plurality" refers to two or more than two. Unless otherwise clearly defined, the terms "upper" and "lower" indicate positions or positional relationships based on the positions or positional relationships described in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on this application. The terms "connect", "install", "fixed", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0140] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0141] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An insulation impedance detection circuit, characterized in that: The insulation impedance detection circuit is used to detect the impedance of the DC bus to ground, the DC bus includes a positive bus and a negative bus, and the insulation impedance detection circuit includes: A sub-detection circuit, the sub-detection circuit comprising a positive detection resistor and a negative detection resistor, the sub-detection circuit being used to detect a bus voltage between the positive bus and the negative bus through the positive detection resistor, and to detect a negative-pole-to-ground voltage of the negative bus through the negative detection resistor; Among them, the number of the sub-detection circuits is two, and the two sub-detection circuits include a first sub-detection circuit and a second sub-detection circuit. The resistance values ​​of the positive detection resistor and the negative detection resistor in the first sub-detection circuit are not equal, and the resistance values ​​of the positive detection resistor and the negative detection resistor in the second sub-detection circuit are equal.

2. The insulation impedance detection circuit according to claim 1, characterized in that: Also includes: A controller, the controller being electrically connected to the first sub-detection circuit and the second sub-detection circuit, the controller being used for: Determine first impedance detection information according to a first bus voltage and a first negative electrode-to-ground voltage; wherein the first bus voltage and the first negative electrode-to-ground voltage are obtained by detection by the first sub-detection circuit; Determine second impedance detection information according to the second bus voltage and the second negative electrode-to-ground voltage; wherein the second bus voltage and the second negative electrode-to-ground voltage are obtained by detection by the second sub-detection circuit; And, based on the first impedance detection information and the second impedance detection information, an insulation impedance detection result of the DC bus is determined.

3. The insulation impedance detection circuit according to claim 2, characterized in that: The controller is further used for: When both the first impedance detection information and the second impedance detection information satisfy the insulation detection condition of the DC bus, determining that the insulation impedance detection result is through the insulation detection; Alternatively, when any one of the first impedance detection information and the second impedance detection information does not satisfy the insulation detection condition of the DC bus, it is determined that the insulation impedance detection result fails the insulation detection.

4. The insulation impedance detection circuit according to claim 1, characterized in that: The sub-detection circuit comprises: The positive electrode detection resistor, wherein a first end of the positive electrode detection resistor is electrically connected to the positive electrode bus bar, and a second end of the positive electrode detection resistor is grounded; A first comparator, wherein a first input terminal of the first comparator is electrically connected to the negative bus, a second input terminal of the first comparator is electrically connected to a first terminal of the positive detection resistor, and an output terminal of the first comparator is used to output the bus voltage.

5. The insulation impedance detection circuit according to claim 4, characterized in that: The sub-detection circuit also includes: a first capacitor, wherein a first end of the first capacitor is electrically connected to the second input end of the first comparator, and a second end of the first capacitor is electrically connected to the negative bus; A first resistor is connected in parallel with the first capacitor.

6. The insulation impedance detection circuit according to claim 1, characterized in that: The sub-detection circuit also includes: The negative electrode detection resistor, wherein a first end of the negative electrode detection resistor is grounded; A second comparator, wherein a first input terminal of the second comparator is electrically connected to the negative electrode bus, a second input terminal of the second comparator is electrically connected to the second end of the negative electrode detection resistor, and an output terminal of the second comparator is used to output the negative electrode-to-ground voltage.

7. The insulation impedance detection circuit according to claim 6, characterized in that: The sub-detection circuit also includes: a second capacitor, wherein a first end of the second capacitor is electrically connected to the second input end of the second comparator, and a second end of the second capacitor is electrically connected to the negative bus; A second resistor is connected in parallel with the second capacitor.

8. A photovoltaic device, characterized in that: include: A photovoltaic power generation component, wherein the output end of the photovoltaic power generation component is electrically connected to a DC bus; The insulation impedance detection circuit according to any one of claims 1 to 7, wherein the insulation impedance detection circuit is electrically connected to the DC bus and is used to detect the impedance of the DC bus to ground.

9. A control method for an insulation impedance detection circuit, characterized in that: The insulation impedance detection circuit includes a first sub-detection circuit and a second sub-detection circuit, the resistance values ​​of the positive electrode detection resistor and the negative electrode detection resistor in the first sub-detection circuit are not equal, and the resistance values ​​of the positive electrode detection resistor and the negative electrode detection resistor in the second sub-detection circuit are equal; the control method includes: Obtaining a first bus voltage, a first negative pole-to-ground voltage, a second bus voltage, and a second negative pole-to-ground voltage of a DC bus; wherein the first bus voltage and the first negative pole-to-ground voltage are obtained by detecting the first sub-detection circuit, and the second bus voltage and the second negative pole-to-ground voltage are obtained by detecting the second sub-detection circuit; Determine first impedance detection information according to the first bus voltage and the first negative electrode-to-ground voltage, and determine second impedance detection information according to the second bus voltage and the second negative electrode-to-ground voltage; An insulation impedance detection result of the DC bus is determined based on the first impedance detection information and the second impedance detection information.

10. The control method of the insulation impedance detection circuit according to claim 9, characterized in that: The step of determining the insulation impedance detection result of the DC bus based on the first impedance detection information and the second impedance detection information includes: When both the first impedance detection information and the second impedance detection information satisfy the insulation detection condition of the DC bus, determining that the insulation impedance detection result is through the insulation detection; Alternatively, when any one of the first impedance detection information and the second impedance detection information does not satisfy the insulation detection condition of the DC bus, it is determined that the insulation impedance detection result fails the insulation detection.

11. A control device for an insulation impedance detection circuit, characterized in that: include: Memory, used to store programs or instructions; A processor is used to implement the control method of the insulation impedance detection circuit as claimed in claim 9 or 10 when executing the program or instruction.

12. A readable storage medium having a program or instruction stored thereon, characterized in that: When the program or instruction is executed by a processor, the control method of the insulation impedance detection circuit according to claim 9 or 10 is implemented.

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