Insulation impedance detection method, device, system, and storage medium

Abstract

The application provides an insulation impedance detection method, device, system and storage medium. The insulation impedance detection method comprises the following steps: determining the initial detection insulation impedance of each power supply unit; determining the initial detection insulation impedance meeting a preset condition as a target insulation impedance according to the initial detection insulation impedance of each power supply unit; determining an insulation detection compensation coefficient according to the target insulation impedance and the initial impedance of the power supply unit; and determining the re-detection insulation impedance of the target power supply unit according to the insulation detection compensation coefficient. The application determines the initial detection insulation impedance of each power supply unit by using the same bridge. After the abnormal initial detection insulation impedance is screened out, the re-detection insulation impedance corresponding to the target power supply unit is determined by using the insulation detection compensation coefficient. Therefore, the problem of complex insulation impedance detection circuit can be avoided, and the measurement accuracy of the insulation impedance can be ensured.

Description

Technical Field

[0001] This application relates to the field of power supply technology, specifically to an insulation impedance detection method, device, system, and storage medium. Background Technology

[0002] Currently, photovoltaic (PV) power generation systems can convert solar radiation energy into electrical energy using solar cell modules. An inverter then converts the direct current (DC) into sinusoidal alternating current (AC) that is in phase and frequency with the grid voltage, ultimately reducing the grid load after being connected to the grid. However, to prevent the risk of electric shock from contact with PV arrays, current standards require that the PV arrays have good insulation performance to ground. Therefore, it is usually necessary to measure the DC insulation resistance between the PV arrays and ground before starting the PV power generation system. The system is only allowed to start operating when the insulation resistance of all PV arrays to ground meets the requirements; otherwise, a fault should be indicated and grid connection should be restricted.

[0003] In related technologies, insulation impedance measurement generally employs the Bridge balancing method. A Bridge branch consisting of a known-value resistor and a controllable switch is constructed between the positive output terminal and ground or the negative output terminal and ground of the photovoltaic array. By controlling the switching on and off, the insulation impedance distribution of the photovoltaic array to ground is altered, and the insulation impedance to ground of the positive and negative output terminals of the photovoltaic array can be calculated by solving a system of two equations. However, since photovoltaic power generation systems typically include n photovoltaic arrays, and the conventional Bridge balancing method can only measure the insulation impedance value of a single photovoltaic array, the hardware requires constructing n Bridge branches, each connected between the output terminals of the n photovoltaic arrays and ground. This results in an exceptionally complex insulation impedance detection circuit. Summary of the Invention

[0004] This application provides an insulation impedance detection method, apparatus, system, and storage medium, aiming to solve the above-mentioned technical problems.

[0005] In a first aspect, this application provides an insulation impedance detection method, which is applied to a power supply system. The power supply system includes multiple power supply units connected in parallel between a positive DC bus and a negative DC bus. The method includes:

[0006] Determine the initial insulation impedance of each power supply unit;

[0007] Based on the initial insulation impedance of each power supply unit, the initial insulation impedance that meets the preset conditions is determined as the target insulation impedance.

[0008] The insulation detection compensation coefficient is determined based on the target insulation impedance and the initial impedance of the power supply unit.

[0009] Determine the re-inspection insulation impedance of the target power supply unit based on the insulation test compensation coefficient;

[0010] The initial insulation impedance of any power supply unit is the impedance value determined by assuming that the voltage between the negative DC bus and the grounding terminal is only affected by that power supply unit. The re-inspection insulation impedance is the impedance value determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units on the voltage between the negative DC bus and the grounding terminal.

[0011] In some embodiments, the power supply system further includes a first bridge connected between the positive DC bus and the ground terminal, and a second bridge connected between the negative DC bus and the ground terminal.

[0012] The steps for determining the initial insulation impedance of each power supply unit include:

[0013] The first and second bridges are controlled to operate in the first working state, and the first detection voltage between the negative DC bus and the ground terminal is acquired in the first working state.

[0014] The first and second bridges are controlled to operate in the second working state, and the second detection voltage between the negative DC bus and the ground terminal is obtained in the second working state;

[0015] Based on the first detection voltage, the second detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of each power supply unit, determine the initial insulation impedance of each power supply unit.

[0016] Among them, at least one of the first bridge and the second bridge has different impedance values ​​in the first operating state and the second operating state.

[0017] In some embodiments, the step of determining the re-inspection insulation impedance corresponding to the target insulation impedance based on the insulation test compensation coefficient includes:

[0018] Based on the insulation detection compensation coefficient and the output voltage of each power supply unit, determine the voltage influence of other power supply units besides the target power supply unit on the negative DC bus and the grounding terminal.

[0019] Based on the voltage influence, the first detection voltage, the second detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of the target power supply unit, determine the re-inspection insulation impedance corresponding to the target power supply unit.

[0020] In some embodiments, the first bridge includes a first resistor and a second resistor connected in series between the positive DC bus and the ground terminal, and a first switch connected in parallel with the second resistor;

[0021] The second bridge includes a third resistor and a fourth resistor connected in series between the negative DC bus and the ground terminal, and a second switch connected in parallel with the fourth resistor;

[0022] Among them, at least one of the first switch and the second switch has a different switch state in the first working state and the second working state.

[0023] In some embodiments, when the first bridge and the second bridge are controlled to operate in the first operating state, the switching states of the first switch and the second switch are the same.

[0024] When the first and second bridges are controlled to operate in the second working state, the switching states of the first and second switches are different.

[0025] In some embodiments, when the first bridge and the second bridge are controlled to operate in the first working state, the first switch and the second switch are in the closed state;

[0026] When the first detected voltage is greater than half the bus voltage, and the first and second bridges are controlled to operate in the second working state, the first switch remains closed and the second switch is changed to open.

[0027] When the first detected voltage is less than half the bus voltage, and the first and second bridges are operating in the second working state, the first switch is changed to the open state, while the second switch remains in the closed state.

[0028] In some embodiments, when the first bridge and the second bridge are controlled to operate in the first working state, the first switch and the second switch are in the off state;

[0029] When the first detected voltage is greater than half the bus voltage, and the first and second bridges are controlled to operate in the second working state, the first switch remains in the open state and the second switch changes to the closed state.

[0030] When the first detected voltage is less than half the bus voltage, and the first and second bridges are operating in the second working state, the first switch changes to the closed state, while the second switch remains in the open state.

[0031] In some embodiments, prior to the step of determining the initial insulation impedance of each power supply unit, the method further includes:

[0032] Control the first and second bridges to operate in the third operating state, and acquire the third detection voltage between the negative DC bus and the ground terminal in the first operating state;

[0033] Control the first and second bridges to operate in the fourth operating state, and acquire the fourth detection voltage between the negative DC bus and the ground terminal in the second operating state;

[0034] Based on the third detection voltage, the fourth detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of each power supply unit, the initial impedance of the power supply unit after the power supply system is installed is determined.

[0035] In some embodiments, the step of determining the initial insulation impedance that meets preset conditions as the target insulation impedance based on the initial insulation impedance of each power supply unit includes:

[0036] The minimum initial insulation impedance among multiple power supply units is determined as the target insulation impedance.

[0037] Secondly, this application provides an insulation resistance detection device, characterized in that it comprises:

[0038] The initial inspection module is used to determine the initial insulation impedance of each power supply unit.

[0039] The abnormal impedance determination module is used to determine the initial insulation impedance that meets the preset conditions as the target insulation impedance of the target power supply unit based on the initial insulation impedance of each power supply unit.

[0040] The compensation determination module is used to determine the insulation detection compensation coefficient based on the target insulation impedance and the initial impedance of the power supply unit.

[0041] The re-inspection module is used to determine the re-inspection insulation impedance corresponding to the target power supply unit based on the insulation detection compensation coefficient.

[0042] The initial insulation impedance of any power supply unit is the impedance value determined by assuming that the voltage between the negative DC bus and the grounding terminal is only affected by that power supply unit. The re-inspection insulation impedance is the impedance value determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units on the voltage between the negative DC bus and the grounding terminal.

[0043] Thirdly, this application provides an insulation impedance detection system, characterized in that it includes a memory and a processor, the memory storing a computer program, and the processor running the computer program in the memory to perform the steps in the insulation impedance detection method described in the first aspect.

[0044] Fourthly, this application provides a storage medium, characterized in that the storage medium stores a plurality of instructions adapted for loading by a processor to execute the steps in the insulation impedance detection method of the first aspect.

[0045] After determining the initial insulation impedance of each power supply unit, this application can screen and determine the initial insulation impedance that meets the preset conditions as the target insulation impedance of the target power supply unit, and use the insulation detection compensation coefficient to compensate the target insulation impedance, thereby determining the re-inspection insulation impedance corresponding to the target power supply unit.

[0046] Since the initial insulation impedance of any power supply unit is determined by assuming that the voltage between the negative DC bus and the grounding terminal is only affected by that power supply unit, the same bridge circuit can be used to measure the initial insulation impedance of each power supply unit. This avoids the problem of having to construct n bridge circuits between the output terminals of n photovoltaic arrays and ground, which would make the insulation impedance detection circuit extremely complex.

[0047] Meanwhile, since the retested insulation impedance is the impedance value determined by the insulation test compensation coefficient to compensate for the influence of other power supply units on the voltage between the negative DC bus and the grounding terminal, the retested insulation impedance is the actual impedance value determined under the influence of all power supply units on the voltage between the negative DC bus and the grounding terminal. Therefore, the accuracy of the insulation impedance measurement can be guaranteed.

[0048] In other words, this application measures the initial insulation impedance of each power supply unit using the same bridge circuit. After screening out abnormal initial insulation impedances, the insulation impedance corresponding to the target power supply unit is re-determined using the insulation detection compensation coefficient. This not only avoids the problem of constructing n bridge branches between the output terminals of n photovoltaic arrays and ground, which would make the insulation impedance detection circuit extremely complex, but also ensures the accuracy of the insulation impedance measurement. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 A schematic diagram of a power supply system according to an embodiment of this application is shown;

[0051] Figure 2 Another schematic diagram of the power supply system in an embodiment of this application is shown;

[0052] Figure 3 Another schematic diagram of the power supply system in an embodiment of this application is shown;

[0053] Figure 4 Another schematic diagram of the power supply system in an embodiment of this application is shown;

[0054] Figure 5 A schematic flowchart of an insulation impedance detection method according to an embodiment of this application is shown;

[0055] Figure 6 This invention illustrates an ideal equivalent circuit diagram for detecting initial insulation impedance in an embodiment of this application.

[0056] Figure 7 This paper shows a schematic diagram of an actual equivalent circuit for detecting insulation impedance in an embodiment of this application;

[0057] Figure 8 This paper illustrates a flowchart of a process for determining the initial insulation impedance in an embodiment of this application.

[0058] Figure 9 This document illustrates a flowchart of a process for determining the insulation impedance for re-inspection in an embodiment of this application.

[0059] Figure 10 This paper illustrates a flowchart of a process for determining the initial impedance in an embodiment of this application.

[0060] Figure 11 This paper shows an equivalent circuit diagram for detecting initial impedance in an embodiment of this application;

[0061] Figure 12 A schematic diagram of an insulation resistance detection device according to an embodiment of this application is shown.

[0062] The system includes 10 power supply units, 20 first bridge, 30 second bridge, first switch S1, second switch S2, positive DC bus BUS+, negative DC bus BUS-, and grounding terminal PE. Detailed Implementation

[0063] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] In the description of this invention, the term "exemplary" is used to mean "serving as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use the invention. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be made without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0065] This application provides an insulation impedance detection method, apparatus, system, and storage medium, which will be described in detail below.

[0066] Before introducing the insulation impedance testing method of this application, let's first introduce the power supply system used for insulation impedance testing. (See attached document.) Figure 1 , Figure 1 A schematic diagram of a power supply system in an embodiment of this application is shown. The power supply system includes multiple power supply units 10 connected in parallel between the positive DC bus BUS+ and the negative DC bus BUS-, a first bridge 20 connected between the positive DC bus BUS+ and the grounding terminal PE, and a second bridge 30 connected between the negative DC bus BUS- and the grounding terminal PE.

[0067] Specifically, the power supply unit 10 can output a DC voltage. After the inverter converts the DC voltage of the power supply unit 10 into a sinusoidal AC current with the same frequency and phase as the grid voltage, the power supply unit 10 can be connected to the grid to reduce the grid load. For example, the power supply unit 10 can be, but is not limited to, energy storage batteries such as lead-acid batteries, lithium-ion batteries, sodium-sulfur batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and lithium iron phosphate batteries.

[0068] In some embodiments of this application, the power supply unit 10 may further include a DC-DC converter, for example in Figure 1 In this circuit, each power supply unit 10 includes a BOOST boost circuit composed of an inductor L, a switching transistor Q, a diode D, and a capacitor C. The BOOST boost circuit increases the output DC voltage of the energy storage battery before outputting it, ensuring that the output voltage of the power supply unit 10 meets the requirements. It is understood that the power supply unit 10 may also include a BUCK step-down circuit or a BOOST-BUCK circuit to control the magnitude of the DC voltage output by the power supply unit 10.

[0069] It should be noted that the insulation impedance of the multiple power supply units 10 includes the impedance between the positive output terminal of each power supply unit 10 and the ground terminal PE, as well as the impedance between the negative output terminal of the multiple power supply units 10 and the ground terminal PE. Figure 1 For example, the insulation resistance between the positive output terminal of the energy storage battery PV1 and the ground terminal PE is equivalent to the resistance R. x1 The insulation resistance between the positive output terminal of the energy storage battery PV2 and the ground terminal PE is equivalent to the resistance R. x2 Similarly, the insulation impedance between the positive output terminal of the energy storage battery PV6 and the ground terminal PE is equivalent to the resistance R. x6 Meanwhile, the insulation impedance between the negative output terminals of energy storage batteries PV1 to PV6 and the ground terminal PE is equivalent to a resistance R. y .

[0070] The impedance of the first bridge 20 and / or the second bridge 30 can be changed by control during the measurement process. When the impedance of the first bridge 20 and / or the second bridge 30 is changed, the voltage between the negative DC bus BUS- and the grounding terminal PE will change. Therefore, by measuring the voltage between the negative DC bus BUS- and the grounding terminal PE, an equation related to the insulation impedance can be constructed, so that the insulation impedance of the power supply unit 10 can be calculated by solving the equation.

[0071] by Figure 1 For example, the first bridge 20 includes a first resistor and a second resistor connected in series between the positive DC bus BUS+ and the ground terminal PE, and a first switch S1 connected in parallel with the second resistor. The resistance values ​​of the first resistor and the second resistor are known. When the first switch S1 changes its operating state, the impedance of the first bridge 20 can be changed. For example, when the first switch S1 changes from a closed state to an open state, the impedance of the first bridge 20 changes from the sum of the resistance values ​​of the first resistor and the second resistor to the resistance value of the first resistor. As another example, when the first switch S1 changes from an open state to a closed state, the impedance of the first bridge 20 changes from the resistance value of the first resistor to the sum of the resistance values ​​of the first resistor and the second resistor.

[0072] The second bridge 30 includes a third resistor and a fourth resistor connected in series between the negative DC bus BUS- and the ground terminal PE, and a second switch S2 connected in parallel with the fourth resistor. Changing the operating state of the second switch S2 changes the impedance of the first bridge 20. For example, when the second switch S2 changes from a closed state to an open state, the impedance of the second bridge 30 changes from the sum of the resistance values ​​of the third and fourth resistors to the resistance value of the third resistor. Similarly, when the second switch S2 changes from an open state to a closed state, the impedance of the second bridge 30 changes from the resistance value of the third resistor to the sum of the resistance values ​​of the third and fourth resistors.

[0073] It should be noted that, for ease of calculating insulation resistance, in Figure 1 The first and third resistors in the middle are both resistors R. a Both the second and fourth resistors use resistor R. b In some possible embodiments, the resistance values ​​of the first resistor and the third resistor may not be equal, and the resistance values ​​of the second resistor and the fourth resistor may also not be equal. Meanwhile, when a high-precision measuring device is used to measure the voltage between the negative DC bus BUS- and the grounding terminal PE, the power supply system may only include the first bridge 20 or the second bridge 30, for example, see [reference needed]. Figure 2 , Figure 2 This paper shows another schematic diagram of the power supply system in an embodiment of the present application, wherein the power supply system includes only a first bridge 20 composed of a first resistor, a second resistor, and a first switch S1; for example, see [reference needed]. Figure 3, Figure 3 Another schematic diagram of the power supply system in an embodiment of this application is shown, wherein the power supply system includes only a second bridge 30 composed of a third resistor, a fourth resistor, and a second switch S2.

[0074] It should be noted that the above description of the power supply system is intended to clearly illustrate the implementation of this application. Those skilled in the art can make equivalent modifications to the power supply system under the guidance of this application; for example, refer to [reference needed]. Figure 4 , Figure 4 Another schematic diagram of the power supply system in an embodiment of this application is shown, wherein the first bridge 20 includes a first resistor and a first switch S1 connected in series between the positive DC bus BUS+ and the ground terminal PE, and the second bridge 30 includes a second resistor and a second switch S2 connected in series between the negative DC bus BUS- and the ground terminal PE.

[0075] The following describes the insulation impedance detection method of this application. This insulation impedance detection method can be applied to the power supply system described in any of the above embodiments. See [link / reference]. Figure 5 , Figure 5 This paper illustrates a flowchart of an insulation impedance detection method according to an embodiment of the present application, wherein the insulation impedance detection method includes:

[0076] Step S501: Determine the initial insulation impedance of each power supply unit 10;

[0077] Specifically, the initial insulation impedance of each power supply unit 10 is an impedance value determined by assuming that the voltage between the negative DC bus BUS- and the grounding terminal PE is only affected by that power supply unit 10. In other words, when determining the initial insulation impedance of each power supply unit 10, it is assumed that the positive output terminal of other power supply units 10 and the grounding terminal PE are open circuits. Therefore, the initial insulation impedance is an ideal measurement value rather than an actual insulation impedance value.

[0078] For example, with Figure 1 For example, during the measurement of insulation resistance, the switching transistor Q is in the off state. Assuming that the positive output terminal of other power supply unit 10 is open-circuited to the ground terminal PE, according to Thevenin's theorem, it can be concluded that... Figure 1 Simplified to Figure 6 The circuit diagram mentioned above, in Figure 6 In the middle, PV i R is the output voltage of the corresponding power supply unit 10. xi R is the insulation resistance between the positive output terminal and the ground terminal PE of the power supply unit 10. yi V is the insulation resistance between the negative output terminal and the ground terminal PE of the power supply unit 10. bus This is the bus voltage between the positive DC bus BUS+ and the negative DC bus BUS-.

[0079] As can be seen, when the positive output terminal and the ground terminal PE of other power supply units 10 are open circuits, the first bridge 20 and the second bridge 30 can be considered as bridges corresponding to the measurement of the insulation impedance of the power supply unit 10. Therefore, the initial insulation impedance of the power supply unit 10 can be determined by using the bridge balance method. The measurement process of other power supply units 10 is the same. Assuming that the positive output terminal and the ground terminal PE of the remaining power supply units 10 are open circuits, the initial insulation impedance of the corresponding power supply unit 10 can be calculated. This will not be elaborated further here.

[0080] Step S502: Based on the initial insulation impedance of each power supply unit 10, determine the initial insulation impedance that meets the preset conditions as the target insulation impedance.

[0081] After determining the initial insulation impedance of each power supply unit 10, the initial insulation impedances that meet preset conditions can be selected as the target insulation impedances of the target power supply unit 10. The target power supply unit 10 is the power supply unit 10 corresponding to the initial insulation impedance that meets the preset conditions. For example, taking... Figure 1 For example, suppose the initial insulation impedance that meets the preset conditions corresponds to the resistance R. x1 If the initial impedance value is obtained, then the power supply unit 10 of the output voltage PV1 is the target power supply unit 10.

[0082] In some embodiments of this application, the initial insulation impedance of multiple power supply units 10 can be determined as the target insulation impedance. For example, the initial insulation impedance of multiple power supply units 10 whose impedance values ​​are within a certain impedance range can be used as the target insulation impedance. In other embodiments of this application, the step of determining the initial insulation impedance that meets preset conditions as the target insulation impedance based on the initial insulation impedance of each power supply unit 10 includes: determining the initial insulation impedance of one power supply unit 10 as the target insulation impedance. For example, the smallest initial insulation impedance among multiple power supply units 10 can be determined as the target insulation impedance.

[0083] Understandably, those skilled in the art can set preset conditions according to actual needs to measure the insulation impedance of the power supply unit 10 that meets the conditions, and this application does not make specific limitations.

[0084] Step S503: Determine the insulation detection compensation coefficient of the target power supply unit 10 based on the target insulation impedance and the initial impedance of the power supply unit 10.

[0085] After determining the target insulation impedance, the insulation detection compensation coefficient can be determined based on the target insulation impedance and the initial impedance of the power supply unit 10, so as to compensate for the voltage influence of other power supply units 10 on the negative DC bus BUS- and the grounding terminal PE based on the insulation detection compensation coefficient.

[0086] It should be noted that, in practice, the voltage between the negative DC bus BUS- and the grounding terminal PE is affected by each power supply unit 10. That is, the positive output terminal of other power supply units 10 is not open-circuited with the grounding terminal PE. Therefore, according to Thevenin's theorem, the voltage can be... Figure 1 The simplified actual circuit diagram is as follows Figure 7 As shown, for Figure 7 In this regard, according to the voltage superposition theorem (i.e., the response (voltage or current) of any branch of a bilateral linear circuit containing multiple independent sources is equal to the algebraic sum of the responses of each independent source acting alone), assuming that the insulation impedance of other power supply units 10 is normal (i.e., the insulation impedance of other power supply units 10 is the known initial impedance measured after system installation), the insulation detection compensation coefficient can be calculated using the following formula:

[0087]

[0088] Among them, R x0 R is the initial impedance of power supply unit 10. xi R yi R is the target insulation resistance. a These are the resistance values ​​of the first and third resistors.

[0089] Step S504: Determine the re-inspection insulation impedance corresponding to the target power supply unit 10 based on the insulation detection compensation coefficient;

[0090] After determining the insulation test compensation coefficient, the insulation test compensation coefficient can be used to compensate for the voltage influence of other power supply units 10 on the negative DC bus BUS- and the grounding terminal PE, so as to correct the voltage component of other power supply units 10 between the negative DC bus BUS- and the grounding terminal PE, thereby determining the retest insulation impedance of the target power supply unit 10 that conforms to the actual situation.

[0091] In this embodiment, since the initial insulation impedance of any power supply unit 10 is determined by the voltage between the negative DC bus BUS- and the grounding terminal PE, which is assumed to be affected only by the power supply unit 10, the same bridge circuit can be used to measure the initial insulation impedance of each power supply unit 10. This avoids the problem of needing to construct n bridge branches between the output terminals of n photovoltaic arrays and ground, which would make the insulation impedance detection circuit extremely complex.

[0092] Meanwhile, since the retested insulation impedance is the impedance value determined by the insulation test compensation coefficient to compensate for the influence of other power supply units 10 on the voltage between the negative DC bus BUS- and the grounding terminal PE, the retested insulation impedance is the actual impedance value determined under the influence of all power supply units 10 on the voltage between the negative DC bus BUS- and the grounding terminal PE, which can ultimately ensure the accuracy of the insulation impedance measurement.

[0093] In other words, this application measures the initial insulation impedance of each power supply unit 10 using the same bridge circuit. After screening out abnormal initial insulation impedances, the insulation impedance corresponding to the target power supply unit 10 is re-determined by using the insulation detection compensation coefficient. This not only avoids the problem of constructing n bridge branches between the output terminals of n photovoltaic arrays and ground, which would make the insulation impedance detection circuit extremely complex, but also ensures the accuracy of the insulation impedance measurement.

[0094] In some embodiments of this application, for example, the power supply system further includes a first bridge 20 connected between the positive DC bus BUS+ and the ground terminal PE, and a second bridge 30 connected between the negative DC bus BUS- and the ground terminal PE, see the embodiments described above. Figure 8 , Figure 8 This paper illustrates a flowchart of an embodiment of the present application for determining the initial insulation impedance, wherein the steps for determining the initial insulation impedance of each power supply unit 10 include:

[0095] Step S801: Control the first bridge 20 and the second bridge 30 to work in the first working state, and obtain the first detection voltage between the negative DC bus BUS- and the ground terminal PE in the first working state;

[0096] Step S802: Control the first bridge 20 and the second bridge 30 to work in the second working state, and obtain the second detection voltage between the negative DC bus BUS- and the ground terminal PE in the second working state;

[0097] Step S803: Determine the initial insulation impedance of each power supply unit 10 based on the first detection voltage, the second detection voltage, the impedance value of the first bridge 20, the impedance value of the second bridge 30, and the output voltage of each power supply unit 10.

[0098] It should be noted that at least one of the first bridge 20 and the second bridge 30 has different impedance values ​​in the first operating state and the second operating state. Therefore, the first detection voltage and the second detection voltage are also different. Thus, two equations can be constructed and the insulation impedance can be solved for each power supply unit 10.

[0099] For example, with Figure 1For example, the first bridge 20 includes a first resistor and a second resistor connected in series between the positive DC bus BUS+ and the ground terminal PE, and a first switch S1 connected in parallel with the second resistor. The second bridge 30 includes a third resistor and a fourth resistor connected in series between the negative DC bus BUS- and the ground terminal PE, and a second switch S2 connected in parallel with the fourth resistor. If at least one of the first switch S1 and the second switch S2 has a different switching state in the first operating state and the second operating state, then at least one of the first bridge 20 and the second bridge 30 can have different impedance values ​​in the first operating state and the second operating state.

[0100] For example, assuming that in the first operating state the first switch S1 of the first bridge 20 is closed and the second switch S2 of the second bridge 30 is closed, then the measured first detection voltage can be calculated according to the following formula:

[0101]

[0102] Among them, V E10 R is the first detection voltage. xi R yi For any power supply unit 10, the initial insulation resistance is PV. i V is the output voltage of any power supply unit 10. bus R is the bus voltage. a These are the resistance values ​​of the first and third resistors.

[0103] For example, assuming that in the second operating state the first switch S1 of the first bridge 20 is closed and the second switch S2 of the second bridge 30 is open, then the measured second detection voltage can be calculated according to the following formula:

[0104]

[0105] Among them, V E11 For the second detection voltage, R b These are the resistance values ​​of the second and fourth resistors.

[0106] For example, assuming that in the second operating state, the first switch S1 of the first bridge 20 is open and the second switch S2 of the second bridge 30 is closed, then the measured second detection voltage can be calculated according to the following formula:

[0107]

[0108] Among them, V E12 This is the second detection voltage.

[0109] It can be seen that during the above process of measuring the first and second detection voltages, the impedance value of the first bridge 20 remains unchanged, but the impedance value of the second bridge 30 changes (or the impedance value of the first bridge 20 changes, but the impedance value of the second bridge 30 remains unchanged). Therefore, at least one of the first bridge 20 and the second bridge 30 has different impedance values ​​in the first and second operating states. Furthermore, combining the calculation formulas for the first and second detection voltages, the calculation formulas for the first and second detection voltages (formula f) are... 11 With formula f 12 Or formula f 11 With formula f 13 There are only two unknowns, Rxi and Ryi, on the left side. Therefore, for different power supply units 10, after measuring the first detection voltage and the second detection voltage, it is only necessary to substitute their output voltage PV. i The insulation resistance R of the power supply unit 10 can then be calculated using both formulas. xi R yi This allows for the final determination of the initial insulation impedance of each power supply unit 10.

[0110] In some embodiments of this application, see Figure 9 , Figure 9 This paper illustrates a flowchart of an embodiment of the present application for determining the re-inspection insulation impedance, wherein the step of determining the re-inspection insulation impedance corresponding to the target insulation impedance based on the insulation testing compensation coefficient includes:

[0111] Step S901: Based on the insulation detection compensation coefficient and the output voltage of each power supply unit 10, determine the voltage influence of other power supply units 10 (excluding the target power supply unit 10) on the negative DC bus BUS- and the grounding terminal PE.

[0112] Step S902: Determine the re-inspection insulation impedance corresponding to the target power supply unit 10 based on the voltage influence, the first detection voltage, the second detection voltage, the impedance value of the first bridge 20, the impedance value of the second bridge 30, and the output voltage of the target power supply unit 10.

[0113] It should be noted that, according to the voltage superposition theorem, the voltage influence of other power supply units 10 besides the target power supply unit 10 on the negative DC bus BUS- and the grounding terminal PE can be calculated as the algebraic sum of the responses of the other power supply units 10 on the negative DC bus BUS- and the grounding terminal PE. Therefore, the voltage influence of other power supply units 10 besides the target power supply unit 10 on the negative DC bus BUS- and the grounding terminal PE can be:

[0114]

[0115] Wherein, PV0 is the output voltage of the target power supply unit 10.

[0116] After determining the voltage impact between the negative DC bus BUS- and the grounding terminal PE of other power supply units 10, the voltage impact can be substituted into the above f. 11 f 12 (or f) 11 f 13 The formula is used to determine the re-inspection insulation impedance of the target power supply unit 10 in combination with the output voltage of the target power supply unit 10.

[0117] For example, if we substitute f above 11 f 12 From the formula, we can obtain two equations:

[0118]

[0119] Among them, R x0 R y0 The insulation impedance of the target power supply unit 10.

[0120] It can be seen that, except for the target power supply unit 10, the voltage influence of other power supply units 10 on the negative DC bus BUS- and the grounding terminal PE is related to the above formula f. 11 f 12 f 13 The formulas were modified, and all of them also have two unknowns R. x0 R y0 Therefore, by combining the above two formulas, the re-inspection insulation impedance R corresponding to the target power supply unit 10 can be calculated. x0 R y0 Meanwhile, since the insulation impedance of the retest is the impedance value determined by the insulation test compensation coefficient to compensate for the voltage influence between the negative DC bus BUS- and the grounding terminal PE of other power supply units 10, the measurement accuracy of the insulation impedance of the target power supply unit 10 can ultimately be guaranteed.

[0121] In some embodiments of this application, such as the embodiment where the first bridge 20 includes a first resistor, a second resistor, and a first switch S1, and the second bridge 30 includes a third resistor, a fourth resistor, and a second switch S2, when the first bridge 20 and the second bridge 30 are controlled to operate in the first operating state, the first switch S1 and the second switch S2 have the same switching state; when the first bridge 20 and the second bridge 30 are controlled to operate in the second operating state, the first switch S1 and the second switch S2 have different switching states.

[0122] For example, when the first bridge 20 and the second bridge 30 are operating in the first working state, both the first switch S1 and the second switch S2 are in the closed state. However, when the first bridge 20 and the second bridge 30 are operating in the second working state, one of the first switch S1 and the second switch S2 is in the closed state, while the other is in the open state. Alternatively, when the first bridge 20 and the second bridge 30 are operating in the first working state, both the first switch S1 and the second switch S2 are in the open state. However, when the first bridge 20 and the second bridge 30 are operating in the second working state, one of the first switch S1 and the second switch S2 is in the closed state, while the other is in the open state.

[0123] In some embodiments of this application, when the first bridge 20 and the second bridge 30 are operating in the first working state, the first switch S1 and the second switch S2 are closed; when the first detected voltage is greater than half the bus voltage, when the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 remains closed, and the second switch S2 is opened; when the first detected voltage is less than half the bus voltage (0.5V)... bus When the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 changes to the open state, and the second switch S2 remains in the closed state.

[0124] It should be noted that when the first detected voltage is greater than half the bus voltage, and the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 remains closed, and the second switch S2 is opened. The impedance of the second bridge 30 connected between the negative DC bus BUS- and the grounding terminal PE increases, which can cause a significant difference between the second measured voltage and the first measured voltage. Similarly, when the first detected voltage is less than half the bus voltage, and the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 is opened, and the second switch S2 remains closed. The impedance of the second bridge 30 connected between the positive DC bus BUS+ and the grounding terminal PE increases, which can also cause a significant difference between the second measured voltage and the first measured voltage.

[0125] As can be seen, in the above embodiments, regardless of whether the first detection voltage is greater than or less than half the bus voltage, the control logic of the above embodiments can make the second measurement voltage significantly different from the first measurement voltage, thereby helping to reduce the impact of voltage sampling accuracy on the detection result and ultimately ensuring the accuracy of insulation impedance detection.

[0126] In some embodiments of this application, when the first bridge 20 and the second bridge 30 are operating in the first working state, the first switch S1 and the second switch S2 are in the open state; when the first detected voltage is greater than half the bus voltage of 0.5V...bus When the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 remains in the open state, and the second switch S2 changes to the closed state; when the first detected voltage is less than half the bus voltage of 0.5V... bus When the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 changes to the closed state, and the second switch S2 remains in the open state.

[0127] Similarly, when the first detection voltage is greater than half the bus voltage by 0.5V... bus When the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 remains open, and the second switch S2 changes to closed. The impedance of the second bridge 30, connected between the negative DC bus BUS- and the ground terminal PE, decreases, thus causing a significant difference between the second measured voltage and the first measured voltage. Similarly, when the first detected voltage is less than half the bus voltage (0.5V)... bus When the first bridge 20 and the second bridge 30 are operating in the second working state, the first switch S1 changes to the closed state and the second switch S2 remains in the open state. The impedance of the second bridge 30 connected between the positive DC bus BUS+ and the ground terminal PE decreases, which can also make the second measured voltage significantly different from the first measured voltage.

[0128] Therefore, regardless of whether the first detection voltage is greater than or less than half the bus voltage, the control logic of the above embodiment can make the second measurement voltage significantly different from the first measurement voltage, thereby helping to reduce the impact of voltage sampling accuracy on the detection result and ensuring the accuracy of insulation impedance detection.

[0129] In some embodiments of this application, before the step of determining the initial insulation impedance of each power supply unit 10, refer to... Figure 10 , Figure 10 This paper illustrates a flowchart of an embodiment of the present application for determining the initial impedance. The insulation impedance detection method of the present application further includes:

[0130] Step S1001: Control the first bridge 20 and the second bridge 30 to work in the third working state, and obtain the third detection voltage between the negative DC bus BUS- and the ground terminal PE in the first working state.

[0131] Step S1002: Control the first bridge 20 and the second bridge 30 to work in the fourth working state, and obtain the fourth detection voltage between the negative DC bus BUS- and the ground terminal PE in the second working state.

[0132] Step S1003: Determine the initial impedance of the power supply unit 10 after installation based on the third detection voltage, the fourth detection voltage, the impedance value of the first bridge 20, the impedance value of the second bridge 30, and the output voltage of each power supply unit 10.

[0133] It should be noted that the initial impedance of power supply unit 10 refers to the insulation impedance measured after the power supply unit 10 is installed on site. After installation, the insulation impedance of power supply unit 10 is normal and the impedance of each power supply unit 10 is equal. Under the condition that the switching transistor is not operating during the initial impedance measurement, according to Thevenin's theorem, it can be... Figure 1 Convert to Figure 11 The equivalent circuit diagram is shown. Meanwhile, since at least one of the first bridge 20 and the second bridge 30 has different impedance values ​​in the third and fourth operating states, the third detection voltage and the fourth detection voltage are also different. Therefore, for each power supply unit 10, two equations can be constructed and the initial impedance after machine installation can be solved.

[0134] For example, with Figure 11 For example, assuming the first switch S1 of the first bridge 20 is closed and the second switch S2 of the second bridge 30 is open in the third operating state, the measured third detection voltage can be calculated using the following formula:

[0135]

[0136] In the above formula, V E01 For the third detection voltage, R x0 R y0 This is the initial impedance.

[0137] Assuming that in the fourth operating state, the first switch S1 of the first bridge 20 is closed and the second switch S2 of the second bridge 30 is closed, then the measured second detection voltage can be calculated using the following formula:

[0138]

[0139] In the above formula, V E02 This is the fourth detection voltage.

[0140] It can be seen that the above formula f 01 and f 02 Only R exists x0 R y0 Since there are two unknowns, after measuring the third and fourth detection voltages, the initial impedance of the power supply unit 10 after installation can be determined by solving the simultaneous equations.

[0141] It should be noted that any calculation formulas in this application are merely exemplary calculation methods and do not constitute a limitation of the claims of this application. Those skilled in the art can make equivalent modifications to the above calculation formulas under the guidance of this application. For example, if both the first switch S1 and the second switch S2 are open when measuring the third detection voltage, and the first switch S1 is open and the second switch S2 is closed when measuring the fourth detection voltage, then the above formula f... 01 and f 02 It can be modified to:

[0142]

[0143] For example, the insulation testing compensation factor of this application can also be calculated using one of the following two formulas:

[0144]

[0145] Furthermore, to better implement the insulation resistance detection method in the embodiments of this application, this application also provides an insulation resistance detection device, in addition to the insulation resistance detection method. (See attached document.) Figure 12 , Figure 12 This illustration shows a schematic diagram of an insulation resistance detection device according to an embodiment of this application, wherein the insulation resistance detection device includes:

[0146] The initial inspection module 1201 is used to determine the initial insulation impedance of each power supply unit 10.

[0147] Abnormal impedance determination module 1202 is used to determine the initial insulation impedance that meets the preset conditions as the target insulation impedance of the target power supply unit 10 based on the initial insulation impedance of each power supply unit 10.

[0148] The compensation determination module 1203 is used to determine the insulation detection compensation coefficient based on the target insulation impedance and the initial impedance of the power supply unit 10.

[0149] The re-inspection module 1204 is used to determine the re-inspection insulation impedance corresponding to the target power supply unit 10 based on the insulation detection compensation coefficient.

[0150] The initial insulation impedance of any power supply unit 10 is determined by assuming that the voltage between the negative DC bus BUS- and the grounding terminal PE is only affected by the power supply unit 10. The re-inspection insulation impedance is determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units 10 on the voltage between the negative DC bus BUS- and the grounding terminal PE.

[0151] It should be understood that Figure 12The apparatus and modules shown can be implemented in various ways. For example, in some embodiments, the apparatus and modules can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the methods and systems described above can be implemented using computer-executable instructions and / or included in processor control code, for example, on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The systems and modules of this application can be implemented not only with hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., but also with software, for example, executed by various types of processors, or with a combination of the aforementioned hardware circuits and software (e.g., firmware).

[0152] It should be noted that the above description of the device and its modules is for convenience only and should not be construed as limiting this application to the scope of the embodiments described. It is understood that those skilled in the art, after understanding the principle of the system, may arbitrarily combine the various modules or construct subsystems connected to other modules without departing from this principle. For example, Figure 12 The initial inspection module 1201, abnormal impedance determination module 1202, compensation determination module 1203, and re-inspection module 1204 disclosed herein can be different modules in one system, or a single module can perform the functions of two or more of the above modules. For example, the initial inspection module 1201 and the re-inspection module 1204 can be two modules that have initial insulation impedance inspection and re-inspection functions respectively, or they can be a single module that has both initial insulation impedance inspection and re-inspection functions.

[0153] Furthermore, this application embodiment also provides an insulation resistance detection system, which includes a memory and a processor. Those skilled in the art will understand that the insulation resistance detection system may include more or fewer components, or combine certain components, or have different component arrangements. Wherein:

[0154] The processor is the control center of the system, connecting various parts of the system through various interfaces and lines. It performs various system functions and processes data by running or executing software programs and / or modules stored in memory, and by calling data stored in memory, thereby providing overall system monitoring. Optionally, the processor may include one or more processing cores; the processor can be a Central Processing Unit (CPU), or other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. Preferably, the processor can integrate an application processor and a modem processor, where the application processor mainly handles the operating system, user interface, and applications, and the modem processor mainly handles wireless communication. It is understood that the modem processor may not be integrated into the processor.

[0155] Memory can be used to store software programs and modules. The processor executes various functional applications and data processing by running the software programs and modules stored in memory. Memory can primarily include a program storage area and a data storage area. The program storage area can store the operating system, application programs required for at least one function (such as sound playback, image playback, etc.), etc.; the data storage area can store data created based on the use of the target detection system. Furthermore, memory can include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other volatile solid-state storage device. Accordingly, memory can also include a memory controller to provide the processor with access to the memory.

[0156] Furthermore, embodiments of the present invention also provide a computer-readable storage medium, which may include: read-only memory (ROM), random access memory (RAM), a magnetic disk, or an optical disk, etc. A computer program is stored thereon, which is loaded by a processor to execute the steps in any of the insulation impedance detection methods provided in the embodiments of the present invention. For example, the computer program loaded by the processor can execute the following steps:

[0157] Determine the initial insulation impedance of each power supply unit 10;

[0158] Based on the initial insulation impedance of each power supply unit 10, the initial insulation impedance that meets the preset conditions is determined as the target insulation impedance.

[0159] The insulation detection compensation coefficient is determined based on the target insulation impedance and the initial impedance of the power supply unit 10.

[0160] The re-inspection insulation impedance of the target power supply unit 10 is determined based on the insulation test compensation coefficient.

[0161] The initial insulation impedance of any power supply unit 10 is determined by assuming that the voltage between the negative DC bus BUS- and the grounding terminal PE is only affected by the power supply unit 10. The re-inspection insulation impedance is determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units 10 on the voltage between the negative DC bus BUS- and the grounding terminal PE.

[0162] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the detailed descriptions of other embodiments above, which will not be repeated here.

[0163] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application, and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0164] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0165] The above provides a detailed description of an insulation impedance detection method, apparatus, system, and storage medium provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. An insulation impedance detection method characterized by comprising: The insulation impedance detection method is applied to a power supply system, which includes multiple power supply units connected in parallel between a positive DC bus and a negative DC bus. The method includes: Determine the initial insulation impedance of each of the power supply units; Based on the initial insulation impedance of each power supply unit, the initial insulation impedance that meets the preset conditions is determined as the target insulation impedance. The insulation detection compensation coefficient is determined based on the target insulation impedance and the initial impedance of the power supply unit. Based on the insulation detection compensation coefficient, determine the re-inspection insulation impedance of the target power supply unit; Wherein, the initial insulation impedance of any of the power supply units is the impedance value determined by assuming that the voltage between the negative DC bus and the grounding terminal is only affected by the power supply unit. The re-inspection insulation impedance is the impedance value determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units on the voltage between the negative DC bus and the grounding terminal; The step of determining the initial insulation impedance that meets the preset conditions as the target insulation impedance based on the initial insulation impedance of each power supply unit includes: The target insulation impedance is determined as the smallest among the initial insulation impedances of the plurality of power supply units.

2. The insulation impedance detection method according to claim 1, wherein The power supply system also includes a first bridge connected between the positive DC bus and the grounding terminal, and a second bridge connected between the negative DC bus and the grounding terminal; The step of determining the initial insulation impedance of each power supply unit includes: The first bridge and the second bridge are controlled to operate in a first working state, and a first detection voltage between the negative DC bus and the ground terminal is obtained in the first working state; The first bridge and the second bridge are controlled to operate in a second working state, and a second detection voltage between the negative DC bus and the grounding terminal is obtained in the second working state; The initial insulation impedance of each power supply unit is determined based on the first detection voltage, the second detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of each power supply unit. Wherein, at least one of the first bridge and the second bridge has different impedance values ​​in the first operating state and the second operating state.

3. The insulation resistance detection method as described in claim 2, characterized in that, The step of determining the re-inspection insulation impedance corresponding to the target insulation impedance based on the insulation detection compensation coefficient includes: Based on the insulation detection compensation coefficient and the output voltage of each power supply unit, determine the voltage influence of the other power supply units besides the target power supply unit on the voltage between the negative DC bus and the grounding terminal. Based on the voltage influence, the first detection voltage, the second detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of the target power supply unit, the re-inspection insulation impedance corresponding to the target power supply unit is determined.

4. The insulation resistance detection method as described in claim 2, characterized in that, The first bridge includes a first resistor and a second resistor connected in series between the positive DC bus and the ground terminal, and a first switch connected in parallel with the second resistor; The second bridge includes a third resistor and a fourth resistor connected in series between the negative DC bus and the ground terminal, and a second switch connected in parallel with the fourth resistor; Wherein, at least one of the first switch and the second switch has a different switch state in the first working state than in the second working state.

5. The insulation resistance detection method as described in claim 4, characterized in that, When the first bridge and the second bridge are controlled to operate in the first working state, the switching states of the first switch and the second switch are the same. When the first bridge and the second bridge are controlled to operate in the second working state, the switching states of the first switch and the second switch are different.

6. The insulation resistance detection method as described in claim 5, characterized in that, When the first bridge and the second bridge are operating in the first working state, the first switch and the second switch are in the closed state. When the first detected voltage is greater than half the bus voltage, when controlling the first bridge and the second bridge to work in the second working state, the first switch remains closed and the second switch is changed to open. When the first detected voltage is less than half the bus voltage, when controlling the first bridge and the second bridge to work in the second working state, the first switch changes to the open state, and the second switch remains in the closed state.

7. The insulation resistance detection method as described in claim 5, characterized in that, When the first bridge and the second bridge are operating in the first working state, the first switch and the second switch are in the off state. When the first detected voltage is greater than half the bus voltage, when controlling the first bridge and the second bridge to work in the second working state, the first switch remains in the open state and the second switch changes to the closed state. When the first detected voltage is less than half the bus voltage, and the first bridge and the second bridge are controlled to operate in the second working state, the first switch changes to the closed state, and the second switch remains in the open state.

8. The insulation resistance detection method as described in claim 7, characterized in that, Prior to the step of determining the initial insulation impedance of each of the power supply units, the method further includes: The first bridge and the second bridge are controlled to operate in a third operating state, and a third detection voltage between the negative DC bus and the grounding terminal is obtained in the first operating state; The first bridge and the second bridge are controlled to operate in a fourth operating state, and a fourth detection voltage between the negative DC bus and the grounding terminal is obtained in the second operating state; The initial impedance of the power supply unit after the power supply system is installed is determined based on the third detection voltage, the fourth detection voltage, the impedance value of the first bridge, the impedance value of the second bridge, and the output voltage of each power supply unit.

9. An insulation resistance detection device, characterized in that, include: The initial inspection module is used to determine the initial insulation impedance of each power supply unit; An abnormal impedance determination module is used to determine the initial insulation impedance that meets preset conditions as the target insulation impedance of the target power supply unit based on the initial insulation impedance of each power supply unit. A compensation determination module is used to determine an insulation detection compensation coefficient based on the target insulation impedance and the initial impedance of the power supply unit. A re-inspection module is used to determine the re-inspection insulation impedance corresponding to the target power supply unit based on the insulation detection compensation coefficient. Wherein, the initial insulation impedance of any of the power supply units is the impedance value determined by assuming that the voltage between the negative DC bus and the grounding terminal is only affected by the power supply unit, and the re-inspection insulation impedance is the impedance value determined by the insulation detection compensation coefficient to compensate for the influence of other power supply units on the voltage between the negative DC bus and the grounding terminal; The step of determining the initial insulation impedance that meets the preset conditions as the target insulation impedance based on the initial insulation impedance of each power supply unit specifically includes: The target insulation impedance is determined as the smallest among the initial insulation impedances of the plurality of power supply units.

10. An insulation resistance detection system, characterized in that, The method includes a memory and a processor, the memory storing a computer program and the processor running the computer program in the memory to perform the steps of the insulation impedance detection method according to any one of claims 1 to 8.

11. A storage medium, characterized in that, The storage medium stores a plurality of instructions adapted for loading by a processor to execute the steps of the insulation impedance detection method according to any one of claims 1 to 8.

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