Insulation fault detection system and method

Abstract

The invention provides an insulation fault detection system and method. The insulation fault detection system comprises a detection unit, a grounding subsystem, a leakage current detection subsystem and a controller. The detection unit is a maximum power point tracking circuit formed by photovoltaic group strings or parallel connection of the photovoltaic group strings. And the grounding subsystem is connected with the positive and negative electrodes of the direct-current bus and the ground and executes positive electrode or negative electrode grounding switching operation. The leakage current detection subsystems are correspondingly arranged on the detection units and used for collecting leakage current. The insulation fault detection system is configured to be capable of forming an independent measurement loop dominated by a current detected unit when executing leakage current collection, the controller receives leakage current values of all the units in sequence based on the independent loop, and through preset numerical value processing, a specific detection unit with an insulation fault can be positioned, and the leakage current values of all the units can be detected. And the approximate position range of the fault photovoltaic module in the detection unit can be further calculated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic power generation, and particularly relates to an insulation fault detection system and method. BACKGROUND

[0002] In the photovoltaic power generation technology, a string type photovoltaic system forms photovoltaic strings by connecting multiple photovoltaic components in series, and connects multiple photovoltaic strings in parallel to an inverter for power conversion. Since photovoltaic panels are placed outdoors for a long time, environmental factors such as dust, rain, snow, and fog can cause changes in the insulation performance of the positive and negative electrodes of the photovoltaic cells. If the insulation impedance value is lower than the safety specified value, the photovoltaic components have a large leakage current to the ground, and human contact with the live parts can cause fatal accidents. In addition, it can also cause local short circuit to cause fire, causing damage to the photovoltaic system and significant property loss. Therefore, insulation fault detection is a core link for safe operation of the photovoltaic system.

[0003] The traditional insulation fault detection method for photovoltaic strings usually only detects the overall ground insulation impedance at the DC bus of the inverter. When the insulation impedance of the entire photovoltaic array (including multiple photovoltaic strings) is detected to be lower than the safety threshold, an alarm is triggered and the circuit is cut off. However, this method can only determine whether there is an insulation problem in the entire photovoltaic array, and cannot accurately locate the specific fault photovoltaic string, nor can it locate the faulty photovoltaic component in the fault photovoltaic string, so the fault troubleshooting efficiency is low. SUMMARY

[0004] The present application provides an insulation fault detection system and method to solve the problem of low fault troubleshooting efficiency of the insulation fault detection scheme in the prior art.

[0005] In a first aspect, an insulation fault detection system is provided, which comprises at least one detection unit, a grounding subsystem, at least one set of leakage current detection subsystems, and a controller. The detection unit is a photovoltaic string or a maximum power point tracking circuit formed by at least two photovoltaic strings connected in parallel, and the photovoltaic string comprises at least two photovoltaic components. The grounding subsystem is connected to the positive pole, the negative pole of a DC bus formed by all the detection units, the controller, and the ground, respectively, and is configured to perform a grounding switching operation under the control of the controller to connect the positive pole or the negative pole of the DC bus to the ground. Each set of leakage current detection subsystems is arranged between one detection unit and the grounding subsystem and is connected to the controller, and is configured to collect a leakage current value flowing through the detection unit when the DC bus is connected to the ground through the grounding subsystem, and send the leakage current value to the controller. The insulation fault detection system is configured to form an independent measurement loop dominated by a currently measured detection unit when collecting the leakage current of any currently measured detection unit. The controller is connected to the grounding subsystem and the leakage current detection subsystems, respectively, and is configured to control the grounding subsystem to perform the grounding switching operation, receive the leakage current values of the leakage current detection subsystems in sequence based on the independent measurement loop, perform preset numerical processing on the leakage current values, and determine the location range of a target photovoltaic component having an insulation fault based on the processing result.

[0006] The insulation fault detection system is configured to form an independent measurement loop dominated by a currently measured detection unit when collecting the leakage current of any currently measured detection unit. The controller is connected to the grounding subsystem and the leakage current detection subsystems, respectively, and is configured to control the grounding subsystem to perform the grounding switching operation, receive the leakage current values of the leakage current detection subsystems in sequence based on the independent measurement loop, perform preset numerical processing on the leakage current values, and determine the location range of a target photovoltaic component having an insulation fault based on the processing result.

[0007] In combination with the first aspect, in a possible implementation, the grounding subsystem comprises a switching device configured to perform the grounding switching operation.

[0008] In combination with the first aspect, in a possible implementation, the insulation fault detection system further comprises a first current-limiting resistor connected to the grounding subsystem and the ground, and configured to limit the current in the grounding loop.

[0009] In combination with the first aspect, in a possible implementation, the insulation fault detection system further comprises a second current-limiting resistor and a third current-limiting resistor. The second current-limiting resistor is connected between the positive pole of the DC bus and the grounding subsystem, and is configured to limit the current in the grounding loop when the positive pole of the DC bus is grounded. The third current-limiting resistor is connected between the negative pole of the DC bus and the grounding subsystem, and is configured to limit the current in the grounding loop when the negative pole of the DC bus is grounded.

[0010] In a possible implementation of the first aspect, the leakage current value includes a positive electrode leakage current value and a negative electrode leakage current value; and the controller is configured to, when performing the preset numerical processing on the leakage current value, specifically configured to: compare the positive electrode leakage current value with a positive electrode leakage current threshold value, and / or compare the negative electrode leakage current value with a negative electrode leakage current threshold value; or, calculate an absolute difference value of the positive electrode leakage current value and the negative electrode leakage current value, and compare the absolute difference value with a preset difference threshold value.

[0011] In a possible implementation of the first aspect, the controller is configured to control the grounding subsystem to perform the grounding switching operation, and receive the leakage current value of each leakage current detection subsystem, perform the preset numerical processing on the leakage current value, and determine the position range of the target photovoltaic module with insulation failure according to the processing result, specifically configured to: when the detection unit is a photovoltaic module string, control the grounding subsystem to sequentially connect the negative electrode and the positive electrode of the Mth photovoltaic module string to the ground, respectively, and through the corresponding Mth leakage current detection subsystem, collect the negative electrode leakage current value IMK- of the Mth photovoltaic module string when the negative electrode is grounded and the positive electrode leakage current value IMK+ of the Mth photovoltaic module string when the positive electrode is grounded in the independent measurement loop, M is a positive integer greater than or equal to 1; if the positive electrode leakage current value IMK+ is greater than a first positive electrode leakage current threshold value, and / or the negative electrode leakage current value IMK- is greater than a first negative electrode leakage current threshold value, or, if the absolute difference value of the positive electrode leakage current value IMK+ and the negative electrode leakage current value IMK- is greater than a first preset difference threshold value, the Mth photovoltaic module string is determined as the photovoltaic module string with insulation failure; calculate the fault position percentage a of the Mth photovoltaic module string according to the formula a = |IMK-| / (|IMK-| + |IMK+|); and locate the position range of the target photovoltaic module with insulation failure according to the fault position percentage a and the number N of photovoltaic modules included in the Mth photovoltaic module string.

[0012] In combination with the first aspect, in a possible implementation, the controller is configured to control the grounding subsystem to perform the grounding switching operation, and receive the leakage current values of the respective leakage current detection subsystems, perform preset numerical processing on the leakage current values, and determine the position range of the target photovoltaic module with insulation failure according to the processing result. Specifically, when the detection unit is a maximum power point tracking circuit, the controller is configured to control the grounding subsystem to sequentially connect the negative electrode and the positive electrode of the Nth maximum power point tracking circuit to the ground, and collect the negative electrode leakage current value INK- of the Nth maximum power point tracking circuit when the negative electrode is grounded and the positive electrode leakage current value INK+ of the Nth maximum power point tracking circuit when the positive electrode is grounded in the independent measurement loop through the corresponding Nth leakage current detection subsystem, where N is a positive integer greater than or equal to 1. If the positive electrode leakage current value INK+ is greater than a second positive electrode leakage current threshold value, and / or the negative electrode leakage current value INK- is greater than a second negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value INK+ and the negative electrode leakage current value INK- is greater than a second preset difference threshold value, the Nth maximum power point tracking circuit is determined to be the target circuit with insulation failure. After the faulty photovoltaic module string is determined from the target circuit, the fault position percentage b in the faulty photovoltaic module string is determined according to the formula b = |INK-| / (|INK-| + |INK+|). The position range of the target photovoltaic module with insulation failure is determined according to the fault position percentage b and the number of photovoltaic modules in the photovoltaic module string.

[0013] In a second aspect, an insulation fault detection method is provided, which is applied to an insulation fault detection system. The insulation fault detection system includes at least one detection unit, a grounding subsystem, at least one set of leakage current detection subsystems, and a controller. The detection unit is a photovoltaic module string or a maximum power point tracking circuit formed by at least two photovoltaic module strings in parallel. The photovoltaic module string includes at least two photovoltaic modules. The grounding subsystem is connected to the positive electrode and the negative electrode of a direct current bus formed by all the detection units, the controller, and the ground. Each detection unit corresponds to a set of leakage current detection subsystems. The leakage current detection subsystems are arranged between the corresponding detection unit and the grounding subsystem and are connected to the controller. The controller is connected to the grounding subsystem and the leakage current detection subsystems. The method is performed by the controller and includes the following steps. The grounding subsystem is controlled to perform a grounding switching operation to connect the positive electrode or the negative electrode of the direct current bus to the ground. The insulation fault detection system forms an independent measurement loop for the currently measured detection unit. The leakage current value flowing through the currently measured detection unit is collected by the leakage current detection subsystem arranged between the currently measured detection unit and the grounding subsystem. The leakage current value collected by the leakage current detection subsystem is received. The leakage current value is subjected to preset numerical processing, and the position range of the target photovoltaic module with insulation failure is determined according to the processing result.

[0014] In combination with the second aspect, in a possible implementation, the leakage current values include positive electrode leakage current values and negative electrode leakage current values, and each detection unit corresponds to a positive electrode leakage current value and a negative electrode leakage current value; the preset numerical processing on the leakage current values and the determination of the location range of the target photovoltaic component with insulation failure according to the processing result include: when the detection unit is a photovoltaic string, under the independent measurement loop of the Mth photovoltaic string, if the positive electrode leakage current value IMK+ of the Mth photovoltaic string is greater than a first positive electrode leakage current threshold value, and / or the negative electrode leakage current value IMK- is greater than a first negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value IMK+ and the negative electrode leakage current value IMK- is greater than a first preset difference threshold value, it is determined that the Mth photovoltaic string is a photovoltaic string with insulation failure, and M is a positive integer greater than or equal to 1; the fault location percentage a of the Mth photovoltaic string is calculated according to the formula a = |IMK-| / (|IMK-| + |IMK+|); and the location range of the target photovoltaic component with insulation failure is located according to the fault location percentage a and the number N of photovoltaic components included in the Mth photovoltaic string.

[0015] In combination with the second aspect, in a possible implementation, the leakage current values include positive electrode leakage current values and negative electrode leakage current values, and each detection unit corresponds to a positive electrode leakage current value and a negative electrode leakage current value; the preset numerical processing on the leakage current values and the determination of the location range of the target photovoltaic component with insulation failure according to the processing result include: when the detection unit is the maximum power point tracking circuit, under the independent measurement loop of the Nth maximum power point tracking circuit, if the positive electrode leakage current value INK+ is greater than a second positive electrode leakage current threshold value, and / or the negative electrode leakage current value INK- is greater than a second negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value INK+ and the negative electrode leakage current value INK- is greater than a second preset difference threshold value, it is determined that the Nth maximum power point tracking circuit is a target circuit with insulation failure, and N is a positive integer greater than or equal to 1; after the fault photovoltaic string is determined from the target circuit, the fault location percentage b in the fault photovoltaic string is determined according to the formula b = |INK-| / (|INK-| + |INK+|); and the location range of the target photovoltaic component with insulation failure is determined according to the fault location percentage b and the number of photovoltaic components in the photovoltaic string.

[0016] The application can achieve the following technical effects: the insulation fault detection system configures an independent leakage current detection subsystem for each detection unit, and performs grounding switching operation by using a grounding subsystem to alternately ground the positive or negative pole of the DC bus. According to the leakage current values of the detection unit in different grounding states collected by the leakage current detection subsystem, the controller can quickly lock the detection unit with insulation fault, and further estimate the approximate position of the target photovoltaic module in the detection unit according to the leakage current values, thereby reducing the fault range from the string level to at least several photovoltaic modules, greatly improving the fault troubleshooting efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A structural schematic diagram of an insulation fault detection system provided by an embodiment of the application is shown in the figure. Figure 2 A structural schematic diagram of another insulation fault detection system provided by an embodiment of the application is shown in the figure. Figure 3 A structural schematic diagram of another insulation fault detection system provided by an embodiment of the application is shown in the figure. Figure 4 A structural schematic diagram of another insulation fault detection system provided by an embodiment of the application is shown in the figure. Figure 5 A flowchart of an insulation fault detection method provided by an embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0019] It should be noted that the features in the embodiments of the application can be combined with each other without conflict, and are within the protection scope of the application. In addition, although the functional modules are divided in the device schematic diagram, and the logical order is shown in the flowchart, in some cases, the steps shown or described can be different from the module division in the device or the order of execution in the flowchart. Furthermore, the "first", "second", "third" and the like used in the application do not limit the data and execution order, but only distinguish the same items or similar items with basically the same function and effect.

[0020] The application is applicable to photovoltaic power generation scenarios, and is particularly applicable to scenarios that require insulation fault detection of photovoltaic strings. In order to better understand the application, the existing insulation fault detection scheme for photovoltaic strings is introduced as follows.

[0021] A photovoltaic (PV) string typically consists of multiple PV modules connected in series. Insulation fault detection of the PV string is a core component in ensuring the safe, compliant operation, and reliability of the PV system. If the insulation impedance value is lower than the safety limit, there will be a significant leakage current from the PV modules to ground. Contact with live parts can cause fatal accidents, and may also lead to partial short circuits and fires, resulting in serious consequences such as damage to the string PV system and significant property loss. Currently, insulation fault detection solutions for PV strings typically only measure the overall insulation impedance to ground at the inverter's DC bus. This method can only determine whether there is an insulation fault at the positive or negative terminal of the overall PV array after the strings are connected, and requires solving multiple sets of equations, resulting in a large computational load. In practice, PV systems typically have multiple PV strings operating in parallel. Detecting only the insulation fault at the positive or negative terminal of the overall PV array after the strings are connected cannot pinpoint which specific PV string is faulty, hindering rapid fault location and troubleshooting, affecting the power generation efficiency of the PV system, and causing economic losses.

[0022] In some embodiments, current acquisition devices can be used to collect the leakage current values ​​of the positive and negative terminals of each photovoltaic string to detect the ground impedance of the corresponding photovoltaic string. If the number of strings connected in parallel in the photovoltaic system is N, then at least 2N current acquisition devices are required. Although this approach can more accurately locate photovoltaic strings with insulation faults, it requires a large number of current acquisition devices, resulting in high costs. Furthermore, it cannot pinpoint the approximate location of the faulty component within the faulty photovoltaic string, leading to relatively low fault diagnosis efficiency.

[0023] In view of this, this application provides an insulation fault detection system and method to solve the problem that current insulation fault detection schemes cannot quickly locate the faulty photovoltaic modules, resulting in low fault diagnosis efficiency. The insulation fault detection system provided in this application is described below.

[0024] Please see Figure 1 This is a structural schematic diagram of an insulation fault detection system provided in this application. Figure 1 The insulation fault detection system 10 shown includes: at least one detection unit ( Figure 1 Two detection units are illustrated, namely detection unit a 101 and detection unit b 102. These detection units can be photovoltaic strings or maximum power point tracking (MPPT) circuits composed of at least two photovoltaic strings connected in parallel. A photovoltaic string includes at least two photovoltaic modules and at least one leakage current detection subsystem. Figure 1Exemplarily, two groups of leakage current detection subsystems are shown, namely, a leakage current detection subsystem 103 and a leakage current detection subsystem 104, a grounding subsystem 105, and a controller 106.

[0025] It should be noted that the at least two photovoltaic modules can be connected in series to form a power generation unit with a specific direct current output voltage. In an embodiment, the photovoltaic modules can be connected by interconnecting strips (thin copper sheets) and encapsulated in a multilayer structure composed of low-iron tempered glass, EVA film, and back plate (such as TPT composite material), and externally fastened with an aluminum alloy frame. The core function of the photovoltaic module string is to convert solar radiation energy into direct current electrical energy.

[0026] The grounding subsystem 105 is connected to the positive and negative poles of the direct current bus formed by all the detection units, the controller, and the ground, respectively, for performing a grounding switching operation under the control of the controller 106 to connect the positive or negative pole of the direct current bus to the ground.

[0027] In an embodiment, the grounding subsystem 105 includes a switching device for performing the grounding switching operation. As a possible implementation, the switching device can include an electromechanical switch (such as a relay), a semiconductor switch such as an Insulated Gate Bipolar Transistor (IGBT), a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), and other devices that can realize circuit state conversion. The switching device is connected to the positive and negative poles of the direct current bus, respectively.

[0028] For example, the grounding subsystem 105 performs a grounding switching operation under the instruction of the controller 106 by means of the switching device, specifically, by alternately connecting the positive or negative pole of the direct current bus to the ground to form a controllable grounding loop. The grounding switching operation can provide a path for leakage current detection, so that the leakage current detection subsystem can collect the leakage current values of each photovoltaic module string.

[0029] The leakage current detection subsystem 103 is provided between a detection unit and the grounding subsystem 105 for each group, and is connected to the controller 106, for collecting the leakage current value flowing through the detection unit when the direct current bus is connected to the ground by the grounding subsystem 105, and sending the leakage current value to the controller 106.

[0030] As a possible implementation, the leakage current detection subsystem can include at least one group of leakage current detection circuits.

[0031] Optionally, the leakage current detection circuit may include a leakage current detection device and a signal filtering and amplification circuit.

[0032] Optionally, the leakage current detection device includes sensors or transformers made using fluxgate or Hall effect methods.

[0033] Optionally, the sensor or transformer may be a series type that can be connected in series in the main circuit, or a through type that connects the positive and negative wires of the string together.

[0034] Optionally, the signal filtering and amplification circuit includes one or more low-pass filtering and amplification circuits to ensure the accuracy of leakage current value sampling.

[0035] It should be noted that each photovoltaic string or each maximum power point tracking circuit is equipped with an independent leakage current detection subsystem.

[0036] For example, when the detection unit connected to it is connected to the ground through the grounding subsystem 105, the leakage current detection subsystem collects the leakage current value flowing through the detection unit in real time. It captures the leakage current of the insulation fault through a sensor or transformer, and removes noise and amplifies the effective signal through a signal filtering and amplification circuit, converting it into standardized data that can be processed by the controller 106.

[0037] The insulation fault detection system 10 is configured to form an independent measurement loop dominated by the current test unit when performing leakage current acquisition for any currently tested test unit.

[0038] It should be noted that the independent measurement circuit refers to the method of ensuring, through electrical or logic control, that the leakage current measurement value of the current test unit is mainly or only determined by the insulation state of the current test unit itself, and is basically unaffected by other parallel test units when collecting leakage current data for a test unit.

[0039] In one feasible implementation, the method of implementing an independent measurement loop may include, but is not limited to, using a selection switch (such as a switch array). Figure 1 (Not shown in the diagram) Only one leakage current detection subsystem is connected to the effective measurement circuit at any given time; or other non-measured units are controlled to be in a high impedance state during measurement.

[0040] Controller 106 is connected to grounding subsystem 105 and leakage current detection subsystem respectively. Figure 1 It is connected to the leakage current detection subsystem 103 (a) and the leakage current detection subsystem 104 (b) to control the grounding subsystem 105 to perform grounding switching operations. It receives the leakage current values ​​of the leakage current detection subsystems in sequence based on independent measurement circuits, performs preset value processing based on the leakage current values, and determines the location range of the target photovoltaic module where the insulation fault occurs based on the processing results.

[0041] In one embodiment, the leakage current values include positive electrode leakage current values and negative electrode leakage current values. The positive electrode leakage current values refer to the leakage current values collected by each leakage current detection subsystem when the positive electrode of the DC bus is grounded. The negative electrode leakage current values refer to the leakage current values collected by each leakage current detection subsystem when the negative electrode of the DC bus is grounded.

[0042] In one embodiment, the controller 106 is configured to control the grounding subsystem 105 to perform the grounding switching operation, receive the leakage current values of each leakage current detection subsystem, perform preset numerical processing on the leakage current values, and determine the position range of the target photovoltaic module with insulation failure according to the processing result. Specifically, when the detection unit is a photovoltaic string, the controller 106 is configured to control the grounding subsystem 105 to sequentially connect the negative electrode and the positive electrode of the Mth photovoltaic string to the ground, and collect the negative electrode leakage current value IMK- of the Mth photovoltaic string when the negative electrode is grounded and the positive electrode leakage current value IMK+ of the Mth photovoltaic string when the positive electrode is grounded through the corresponding Mth leakage current detection subsystem, where M is a positive integer greater than or equal to 1. If the positive electrode leakage current value IMK+ is greater than a first positive electrode leakage current threshold value, and / or the negative electrode leakage current value IMK- is greater than a first negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value IMK+ and the negative electrode leakage current value IMK- is greater than a first preset difference threshold value, the Mth photovoltaic string is determined to be the photovoltaic string with insulation failure. The failure position percentage a of the Mth photovoltaic string is calculated according to the formula a = |IMK-| / (|IMK- | + |IMK+|). The position range of the target photovoltaic module with insulation failure is located according to the failure position percentage a and the number N of photovoltaic modules included in the Mth photovoltaic string.

[0043] For example, the controller 106 can send an insulation fault detection instruction to the grounding subsystem 105. The grounding subsystem 105 receives the insulation fault detection instruction, controls the positive electrode of each photovoltaic string to be connected to the ground, each leakage current detection subsystem sequentially records the positive electrode leakage current value InK+ between the positive electrode of the photovoltaic string connected thereto and the ground, and uploads the positive electrode leakage current value to the controller 106. Then, the controller 106 sends a grounding switching instruction to control the grounding subsystem 105 to perform the grounding switching operation. The grounding subsystem 105 controls the negative electrode of each photovoltaic string to be connected to the ground, sequentially records the negative electrode leakage current value InK- between the negative electrode of each photovoltaic string and the ground, and uploads the negative electrode leakage current value to the controller 106.

[0044] Further, if the controller 106 determines that the Mth group of leakage current detection subsystems collects a positive electrode leakage current value IMK+ of the Mth group of photovoltaic strings greater than the first positive electrode leakage current threshold value, and / or a negative electrode leakage current value IMK- greater than the first negative electrode leakage current threshold value, or an absolute difference between the positive electrode leakage current value IMK+ and the negative electrode leakage current value IMK- greater than the first preset difference threshold value, the controller 106 can determine that the Mth group of photovoltaic strings is a photovoltaic string with insulation failure. Assuming that the negative electrode in the position of the photovoltaic string with insulation failure is marked as 0% and the positive electrode is marked as 100%, the controller 106 can calculate the fault position percentage a by the calculation formula: a = |IMK-| / (|IMK-| + |IMK+|), and if there are N photovoltaic components in the photovoltaic string with insulation failure, the position range of the target photovoltaic component with insulation failure can be located by multiplying the number of photovoltaic components N in the photovoltaic string with insulation failure by the fault percentage a.

[0045] Optionally, the controller 106 judges whether InK+, InK- exceeds the corresponding leakage current threshold value, if at least one leakage current value exceeds the corresponding leakage current threshold value, the controller 106 reports insulation failure, if it does not exceed the leakage current threshold value, the controller 106 reports that the insulation failure detection is normal. Alternatively, the controller 106 can also judge whether insulation failure occurs by judging the absolute value difference between InK+ and InK- of each group of photovoltaic strings or maximum power point tracking circuit, or by other numerical processing methods.

[0046] In one embodiment, the insulation fault detection system 10 further comprises a first current limiting resistor connected between the grounding subsystem and the ground for limiting the current in the grounding loop.

[0047] For example, the first current limiting resistor can be connected near the ground end, and the positive or negative electrode of the DC bus is connected to the same first current limiting resistor when connected to the ground.

[0048] In one embodiment, the insulation fault detection system 10 further comprises a second current limiting resistor and a third current limiting resistor; the second current limiting resistor is connected between the positive electrode of the DC bus and the grounding subsystem, for limiting the current in the grounding loop when the positive electrode of the DC bus is grounded; the third current limiting resistor is connected between the negative electrode of the DC bus and the grounding subsystem, for limiting the current in the grounding loop when the negative electrode of the DC bus is grounded.

[0049] For example, the current limiting resistor of the insulation fault detection system 10 can be divided into two groups, namely the second current limiting resistor and the third current limiting resistor, which are respectively connected between the positive electrode of the DC bus and the grounding subsystem, and between the negative electrode of the DC bus and the grounding subsystem, and can limit the leakage current through different current limiting resistors when the positive or negative electrode of the DC bus is connected to the ground.

[0050] Please refer to the following Figure 2 , another structure diagram of insulation fault detection system provided in the present application. Figure 2 The structure of the insulation fault detection system 20 shown is based on Figure 1 The specific example of the insulation fault detection system 10 shown, wherein, Figure 2 The detection unit of the insulation fault detection system 20 shown is a photovoltaic string.

[0051] In this example, the insulation fault detection system 20 includes: a photovoltaic string 2, a plurality of photovoltaic components 1 are connected in series to form the photovoltaic string 2. The positive poles PV+ of the plurality of photovoltaic strings are collected as the positive pole of the DC bus (i.e. bus +), and the negative poles PV- of the plurality of photovoltaic strings are collected as the negative pole of the DC bus (i.e. bus -). The switch S1 connected to the bus + and the switch S2 connected to the bus - together form a grounding subsystem. 4 is a first current limiting resistor R, and 5 is the ground. There can be n leakage current detection subsystems, each of which is connected to a photovoltaic string, and each of which can include a leakage current detection circuit and a sensor (for example, the leakage current detection subsystem corresponding to the photovoltaic string 2 includes a leakage current detection circuit 1 and a sensor 3). The controller 6 is connected to each leakage current detection subsystem and the grounding subsystem. The sensor 3 sends the collected leakage current signal to the leakage current detection circuit 1, and the leakage current detection circuit 1 sends the collected leakage current to the controller 6, which can control the grounding subsystem (switches S1 and S2) to be connected to the first current limiting resistor 4 and to the ground 5.

[0052] The working mode of the insulation fault detection system 20 will be described below. The controller 6 issues an insulation fault detection instruction, the grounding subsystem controls the switch S1 to be turned on and the switch S2 to be turned off, and the bus + of the photovoltaic string after being collected is connected to the ground 5 through the first current limiting resistor 4. The photovoltaic string 1 collects the leakage current value on the photovoltaic string through the sensor 3 and the leakage current detection circuit 1, uploads the leakage current value between the positive pole PV+ of the photovoltaic string 1 and the ground to the controller 6, and marks it as I1K+. Further, the leakage current values between the positive poles of the nth photovoltaic string and the ground are sequentially collected and uploaded to the controller 6, and marked as InK+.

[0053] The controller 6 issues a switching instruction, the grounding subsystem controls the switch S1 to be turned off and the switch S2 to be turned on, and the bus - of the string after being collected is connected to the ground 5 through the first current limiting resistor 4. The photovoltaic string 1 collects the leakage current value on the photovoltaic string 1 through the sensor 3 and the string leakage current detection circuit 1, uploads the leakage current value between the negative pole PV- of the photovoltaic string 1 and the ground to the controller, and marks it as I1K-. Further, the leakage current values between the negative poles PV- of the nth photovoltaic string and the ground are sequentially collected and uploaded to the controller 6, and marked as InK-.

[0054] Then, the controller can determine whether InK+, InK- is in the set corresponding leakage current threshold range, or other numerical processing, to determine whether an insulation fault occurs, if the fault, report insulation fault, if normal, report insulation fault detection.

[0055] With the insulation fault of the photovoltaic string 1, the controller determines that I1K+ is greater than the set first positive leakage current threshold, or I1K- is greater than the set first negative leakage current threshold, and the controller 6 reports insulation fault detection fault.

[0056] Further, the controller 6 retrieves the leakage current values I1K+ and I1K- when the positive and negative of the photovoltaic string 1 with insulation fault are connected to the ground, calculates the fault position percentage a of the faulty photovoltaic component in the photovoltaic string 1 position by the formula a = |I1K-| / (|I1K-| + |I1K+|) (optionally, the position of the string negative PV- in the string can be marked as 0%, and the position of the string positive PV+ in the string can be marked as 100%), and then the approximate position range of the target photovoltaic component with insulation fault can be located by multiplying the total number of components N in the photovoltaic string 1 by the fault position percentage a. For example, if the photovoltaic string 1 contains 36 components, N = 36, the calculated percentage a = 90%, and the faulty component is 36 x 90% = 32.4 blocks. After the controller 6 uploads the insulation fault, it prompts that the faulty photovoltaic component is the 32th ± 1 block in the photovoltaic string.

[0057] As can be seen, the insulation fault system shown in the embodiments of the present application configures an independent leakage current detection subsystem for each photovoltaic string, and uses the grounding subsystem to perform grounding switching operation to alternately ground the positive or negative of the DC bus. The controller can quickly lock the specific photovoltaic string with insulation fault according to the leakage current values collected by the leakage current detection subsystem under different grounding states, and further estimate the approximate position of the target photovoltaic component with fault in the photovoltaic string, so as to reduce the fault range to at least several photovoltaic components from the whole string, greatly improving the fault troubleshooting efficiency.

[0058] Please refer to Figure 3 Another insulation fault detection system structure diagram provided by the embodiments of the present application. Figure 3 The detection unit of the insulation fault detection system 30 shown is a maximum power point tracking circuit, and the insulation fault detection system 30 comprises: at least one maximum power point tracking circuit (MPPT circuit) Figure 3 Exemplarily, two maximum power point tracking circuits are shown, which are maximum power point tracking circuit c301 and maximum power point tracking circuit d302, respectively, grounding subsystem 305, at least one leakage current detection subsystem (Leakage current detection subsystem a 306, Leakage current detection subsystem b 307) Figure 3Exemplarily, two groups of leakage current detection subsystems are shown, which are leakage current detection subsystem c 303 and leakage current detection subsystem d 304, respectively, and a controller 306.

[0059] The maximum power point tracking circuit is composed of at least two groups of photovoltaic strings in parallel. Figure 3 Exemplarily, two maximum power point tracking circuits are shown, which are maximum power point tracking circuit c 301 and maximum power point tracking circuit d 302. Each maximum power point tracking circuit can include at least two groups of photovoltaic strings in parallel, and the photovoltaic strings include at least two photovoltaic components in series.

[0060] In some embodiments, the insulation fault detection system 30 can also include at least one group of photovoltaic strings, and the photovoltaic strings correspond to the leakage current detection subsystem.

[0061] It should be noted that in the photovoltaic system, multiple independent maximum power point tracking circuits are configured, which can independently and finely track the maximum power point of different photovoltaic strings, and are more suitable for photovoltaic power stations in complex environments, and can effectively improve the power generation.

[0062] The grounding subsystem 305 is connected with the positive electrode and the negative electrode of each maximum power point tracking circuit, the controller 306 and the ground, respectively, and is used to perform grounding switching operation under the control of the controller 306, so as to connect the positive electrode or the negative electrode of each maximum power point tracking circuit with the ground.

[0063] The leakage current detection subsystem is correspondingly arranged between each maximum power point tracking circuit and the grounding subsystem, and is connected with the controller 306, and is used to collect the leakage current value flowing through the corresponding maximum power point tracking circuit when the corresponding maximum power point tracking circuit is connected with the ground through the grounding subsystem 305.

[0064] The controller 306 is connected with the grounding subsystem 305 and each leakage current detection subsystem, respectively, and is used to control the grounding subsystem 305 to perform grounding switching operation, receive the leakage current value of each leakage current detection subsystem, perform preset numerical processing according to the leakage current value, and determine the position range of the target photovoltaic component with insulation fault according to the processing result.

[0065] In one embodiment, the leakage current values include positive electrode leakage current values and negative electrode leakage current values; the controller 306 is configured to control the grounding subsystem 305 to perform a grounding switching operation, and receive leakage current values of each leakage current detection subsystem, and perform a preset numerical processing on the leakage current values, and determine a position range of a target photovoltaic module with insulation failure according to a processing result; and when the detection unit is a maximum power point tracking circuit, the controller 306 is specifically configured to control the grounding subsystem 305 to sequentially connect the negative electrode and the positive electrode of the Nth maximum power point tracking circuit to the ground, and collect a negative electrode leakage current value INK- of the Nth maximum power point tracking circuit when the negative electrode is grounded and a positive electrode leakage current value INK+ of the Nth maximum power point tracking circuit when the positive electrode is grounded through the Nth leakage current detection subsystem, where N is a positive integer greater than or equal to 1; if the positive electrode leakage current value INK+ is greater than a second positive electrode leakage current threshold value and / or the negative electrode leakage current value INK- is greater than a second negative electrode leakage current threshold value, or if an absolute difference between the positive electrode leakage current value INK+ and the negative electrode leakage current value INK- is greater than a second preset difference threshold value, the Nth maximum power point tracking circuit is determined as the target circuit with insulation failure; after the faulty photovoltaic module string is determined from the target circuit, a fault position percentage b in the faulty photovoltaic module string is determined according to the formula b = |INK-| / (|INK-| + |INK+|); and the position range of the target photovoltaic module with insulation failure is determined according to the fault position percentage b and the number of photovoltaic modules in the photovoltaic module string.

[0066] Please refer to the following Figure 4 , which is a structural schematic diagram of another insulation fault detection system provided in the present application. Figure 4 The structure of the insulation fault detection system 40 shown is based on Figure 3 The specific example of the insulation fault detection system 30 shown can be applied to photovoltaic devices such as photovoltaic inverters, photovoltaic storage inverters, etc. In this example, the insulation fault detection system 40 includes M maximum power point tracking circuits (i.e. MPPTs) in Figure 4 Each maximum power point tracking circuit is composed of n photovoltaic module strings in parallel. The positive electrodes of the multiple maximum power point tracking circuits are connected to the positive electrode of the DC bus (i.e. BUS+ in Figure 4 The negative electrodes of the multiple maximum power point tracking circuits are connected to the negative electrode of the DC bus (i.e. BUS- in Figure 4 The leakage current detection subsystem (which can include a leakage current detection circuit and a sensor) detects the leakage current at the MPPT level. The grounding subsystem includes a changeover switch S1 and a changeover switch S2. After the changeover switch S1 is closed, BUS+ is connected to the ground through a second current limiting resistor (i.e. the current limiting resistor R1 in Figure 4 After the changeover switch S2 is closed, BUS- is connected to the ground through a third current limiting resistor (i.e. the current limiting resistor R2 in Figure 4 .

[0067] Figure 4 The working mode of the insulation fault detection system 40 shown is that: after the controller issues an insulation fault detection instruction, the grounding subsystem controls switch S1 to be turned on and switch S2 to be turned off, and the BUS+ collected by MPPT-1 is connected to the ground G through current-limiting resistor 1; the first path maximum power point tracking circuit MPPT-1 collects the leakage current signal on the maximum power point tracking circuit through sensor 1 and leakage current detection circuit 1, uploads the leakage current value between the positive pole PV+ of the first path MPPT and the ground to the controller, and is recorded as I1K+; further, the leakage current value between the positive pole of the Mth path maximum power point tracking circuit and the ground is sequentially collected and uploaded to the controller, and is recorded as IMK+.

[0068] The controller determines whether IMK+ and IMK- are within the set corresponding leakage current threshold range. Taking the insulation fault of the MPPT-1 circuit as an example, if I1K+ or I1K- is greater than the set corresponding leakage current threshold, the controller determines that the MPPT-1 circuit is the target circuit that has failed, and can report an insulation fault detection failure.

[0069] Alternatively, the controller can also compare the absolute value difference of IMK+ and IMK- or perform other numerical processing to determine whether an insulation fault has occurred. If a fault occurs, the insulation fault is reported, and if it is normal, the insulation fault detection is reported to be passed.

[0070] Further, by artificially unplugging the photovoltaic module string connected to the faulty MPPT-1, 1-PV1, 1-PV2, …, 1-PVn are sequentially connected to MPPT-1 alone. When a certain photovoltaic module string is unplugged, the positive pole leakage current value and / or the negative pole leakage current value of MPPT-1 is within the set corresponding leakage current threshold, indicating that the unplugged photovoltaic module string is the faulty photovoltaic module string.

[0071] Further, the controller retrieves the leakage current values I1K+ and I1K- when the positive pole and the negative pole of the faulty MPPT-1 are connected to the ground, and calculates the fault position percentage b of the faulty component in the faulty photovoltaic module string by the formula b = |I1K-| / (|I1K-| + |I1K+|).

[0072] Optionally, the location of the faulty photovoltaic string negative PV in the photovoltaic string can be recorded as 0%, and the location of the positive PV in the photovoltaic string can be recorded as 100%. By multiplying the total number of photovoltaic components N in the photovoltaic string and the fault location percentage b, the approximate photovoltaic component location can be located. For example, if the photovoltaic string contains 36 components, N = 36, and the calculated percentage b = 90%, then the location range p of the photovoltaic component with insulation failure is N * a = 36 * 90% = 32.4 components. After the controller detects the insulation failure, the target photovoltaic component with insulation failure is prompted to be the 32th ± 1 component in the faulty photovoltaic string.

[0073] As can be seen, by using the insulation fault detection system shown in the embodiments of the present application, the MPPT level insulation fault of the photovoltaic string can be accurately located. By artificially unplugging the photovoltaic string connected to the faulty MPPT, the photovoltaic string with insulation failure can be quickly located. By analyzing the MPPT level leakage current value collected by the leakage current collection subsystem, the approximate location of the target photovoltaic component with insulation failure in the photovoltaic string with insulation failure can be determined. This can improve the fault troubleshooting efficiency, further reduce system cost and equipment space, and is more suitable for practical application.

[0074] Please refer to Figure 5 , a flowchart of an insulation fault detection method provided by the embodiments of the present application. Figure 5 The method shown can be applied to the insulation fault detection system described above. For the description of the insulation fault detection system, please refer to the introduction of the system embodiments described above, which will not be repeated here.

[0075] Figure 5 The insulation fault detection method shown is executed by the controller in the insulation fault detection system, and includes the following steps: S501, controlling the grounding subsystem to perform a grounding switching operation to connect the positive or negative of the DC bus to the ground.

[0076] Optionally, the controller can issue a grounding switching instruction to control the grounding subsystem to perform the grounding switching operation.

[0077] S502, controlling the insulation fault detection system to form an independent measurement loop for the current measured detection unit.

[0078] S503, collecting the leakage current value flowing through the current measured detection unit by the leakage current detection subsystem correspondingly arranged between the current measured detection unit and the grounding subsystem.

[0079] S504, receiving the leakage current value collected by the leakage current detection subsystem.

[0080] S505, performing preset numerical processing on the leakage current value, and determining a position range of the target photovoltaic module with insulation failure according to a processing result.

[0081] In one embodiment, the leakage current value includes a positive electrode leakage current value and a negative electrode leakage current value, and each detection unit corresponds to a positive electrode leakage current value and a negative electrode leakage current value respectively; the preset numerical processing on the leakage current value, and the determination of the position range of the target photovoltaic module with insulation failure according to the processing result, includes: when the detection unit is a photovoltaic string, in the independent measurement loop for the Mth photovoltaic string, if the positive electrode leakage current value IMK+ of the Mth photovoltaic string is greater than a first positive electrode leakage current threshold value, and / or the negative electrode leakage current value IMK- is greater than a first negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value IMK+ and the negative electrode leakage current value IMK- is greater than a first preset difference threshold value, the Mth photovoltaic string is determined to be the photovoltaic string with insulation failure, M is a positive integer greater than or equal to 1; the fault position percentage a of the Mth photovoltaic string is calculated according to the formula a = |IMK-| / (|IMK-| + |IMK+|); and the position range of the target photovoltaic module with insulation failure is located according to the fault position percentage a and the number N of photovoltaic modules contained in the Mth photovoltaic string.

[0082] In one embodiment, the leakage current value includes a positive electrode leakage current value and a negative electrode leakage current value, and each detection unit corresponds to a positive electrode leakage current value and a negative electrode leakage current value respectively; the preset numerical processing on the leakage current value, and the determination of the position range of the target photovoltaic module with insulation failure according to the processing result, includes: when the detection unit is a maximum power point tracking circuit, in the independent measurement loop for the Nth maximum power point tracking circuit, if the positive electrode leakage current value INK+ is greater than a second positive electrode leakage current threshold value, and / or the negative electrode leakage current value INK- is greater than a second negative electrode leakage current threshold value, or if the absolute difference between the positive electrode leakage current value INK+ and the negative electrode leakage current value INK- is greater than a second preset difference threshold value, the Nth maximum power point tracking circuit is determined to be the target circuit with insulation failure, N is a positive integer greater than or equal to 1; after the fault photovoltaic string is determined from the target circuit, the fault position percentage b in the fault photovoltaic string is determined according to the formula b = |INK-| / (|INK-| + |INK+|); and the position range of the target photovoltaic module with insulation failure is determined according to the fault position percentage b and the number of photovoltaic modules in the photovoltaic string.

[0083] Optionally, the controller can determine whether the positive electrode leakage current value and the negative electrode leakage current value exceed the respective leakage current threshold values, and if at least one leakage current value exceeds the corresponding leakage current threshold value, the controller reports an insulation fault, and if the leakage current threshold values are not exceeded, the controller reports that the insulation fault detection is normal. Alternatively, the controller can also compare the absolute value difference between the positive electrode leakage current value and the negative electrode leakage current value of the same photovoltaic string or the same maximum power point tracking circuit or perform other numerical processing, to determine whether an insulation fault has occurred, and if a fault has occurred, report an insulation fault, and if normal, report that the insulation fault detection is passed.

[0084] It can be seen that the insulation fault detection method shown in the present application can perform preset numerical processing on the leakage current values of the positive electrode and the negative electrode of the detection unit to the ground after collecting the leakage current values, and can quickly lock the detection unit that has an insulation fault. In addition, the leakage current values can be used to further estimate the approximate position of the target photovoltaic module in the detection unit, thereby reducing the fault range from the string level to the position range of the photovoltaic module, and greatly improving the troubleshooting efficiency.

[0085] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiments can be completed by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above-mentioned embodiments. The storage medium can be a magnetic disc, an optical disc, a read-only memory (ROM), a random access memory (RAM), or the like.

[0086] The above only describes the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, so equivalent changes made according to the claims of the present application are still within the scope of the present application.

Claims

1. An insulation fault detection system, characterized in that, The insulation fault detection system includes: at least one detection unit, a grounding subsystem, at least one set of leakage current detection subsystems, and a controller; The detection unit is a photovoltaic string, or a maximum power point tracking circuit composed of at least two sets of photovoltaic strings connected in parallel, wherein the photovoltaic string includes at least two photovoltaic modules; The grounding subsystem is connected to the positive and negative poles of the DC bus formed by all the detection units, the controller, and the earth, respectively, and is used to perform grounding switching operations under the control of the controller to connect the positive or negative pole of the DC bus to the earth. Each of the leakage current detection subsystems is set between one of the detection units and the grounding subsystem, and is connected to the controller. It is used to collect the leakage current value flowing through the detection unit when the DC bus is connected to the ground through the grounding subsystem, and send the leakage current value to the controller. The insulation fault detection system is configured to form an independent measurement loop dominated by the current test unit when performing leakage current acquisition for any currently tested test unit. The controller is connected to the grounding subsystem and the leakage current detection subsystem respectively. It is used to control the grounding subsystem to perform the grounding switching operation, and to receive the leakage current values ​​of each leakage current detection subsystem in sequence based on the independent measurement circuit. It performs preset value processing on the leakage current values ​​and determines the location range of the target photovoltaic module where the insulation fault occurs based on the processing results.

2. The insulation fault detection system as described in claim 1, characterized in that, The grounding subsystem includes a switching device for performing the grounding switching operation.

3. The insulation fault detection system as described in claim 2, characterized in that, The insulation fault detection system further includes a first current-limiting resistor, which is connected to the grounding subsystem and the earth, and is used to limit the current in the grounding circuit.

4. The insulation fault detection system as described in claim 2, characterized in that, The insulation fault detection system also includes a second current-limiting resistor and a third current-limiting resistor; The second current-limiting resistor is connected between the positive terminal of the DC bus and the grounding subsystem to limit the current in the grounding loop when the positive terminal of the DC bus is grounded. The third current-limiting resistor is connected between the negative terminal of the DC bus and the grounding subsystem, and is used to limit the current in the grounding circuit when the negative terminal of the DC bus is grounded.

5. The insulation fault detection system as described in claim 1, characterized in that, The leakage current value includes the positive leakage current value and the negative leakage current value; When the controller is used to perform preset value processing based on the leakage current value, it is specifically used for: Compare the positive leakage current value with a positive leakage current threshold, and / or compare the negative leakage current value with a negative leakage current threshold; or, Calculate the absolute difference between the positive leakage current value and the negative leakage current value, and compare the absolute difference with a preset difference threshold.

6. The insulation fault detection system as described in claim 5, characterized in that, The controller is used to control the grounding subsystem to perform the grounding switching operation, and to receive the leakage current values ​​of each leakage current detection subsystem, perform preset value processing based on the leakage current values, and determine the location range of the target photovoltaic module where the insulation fault occurs based on the processing results. Specifically, it is used for: When the detection unit is the photovoltaic string, the grounding subsystem is controlled to connect the negative and positive terminals of the Mth photovoltaic string to the ground in sequence, and the corresponding leakage current detection subsystem of the Mth group collects the negative leakage current value IMK- when the negative terminal is grounded and the positive leakage current value IMK+ when the positive terminal is grounded in the independent measurement circuit, where M is a positive integer greater than or equal to 1; If the positive leakage current value IMK+ is greater than the first positive leakage current threshold, and / or the negative leakage current value IMK- is greater than the first negative leakage current threshold, or if the absolute difference between the positive leakage current value IMK+ and the negative leakage current value IMK- is greater than the first preset difference threshold, then the Mth photovoltaic string is determined to be a photovoltaic string with an insulation fault. The percentage of fault locations, a, of the Mth photovoltaic string is calculated using the formula a = |IMK-| / (|IMK-| + |IMK+|). Based on the percentage of fault location 'a' and the number of photovoltaic modules 'N' contained in the Mth photovoltaic string, the location range of the target photovoltaic module with insulation fault is determined.

7. The insulation fault detection system as described in claim 5, characterized in that, The controller is used to control the grounding subsystem to perform the grounding switching operation, and to receive the leakage current values ​​of each leakage current detection subsystem, perform preset value processing based on the leakage current values, and determine the location range of the target photovoltaic module where the insulation fault occurs based on the processing results. Specifically, it is used for: When the detection unit is the maximum power point tracking circuit, the grounding subsystem is controlled to connect the negative and positive terminals of the Nth maximum power point tracking circuit to the ground in sequence, and the corresponding Nth leakage current detection subsystem collects the negative leakage current value INK- when the Nth maximum power point tracking circuit is grounded and the positive leakage current value INK+ when the Nth maximum power point tracking circuit is grounded in the independent measurement circuit, where N is a positive integer greater than or equal to 1; If the positive leakage current value INK+ is greater than the second positive leakage current threshold, and / or the negative leakage current value INK- is greater than the second negative leakage current threshold, or if the absolute difference between the positive leakage current value INK+ and the negative leakage current value INK- is greater than the second preset difference threshold, then the Nth maximum power point tracking circuit is determined to be the target circuit with an insulation fault. After identifying the faulty photovoltaic string from the target circuit, the percentage of faulty locations b in the faulty photovoltaic string is determined according to the formula b = |INK-| / (|INK-| + |INK+|). Based on the percentage of fault locations b and the number of photovoltaic modules in the photovoltaic string, the location range of the target photovoltaic module where the insulation fault occurred is determined.

8. A method for detecting insulation faults, characterized in that, The invention is applied to an insulation fault detection system, which includes at least one detection unit, a grounding subsystem, at least one set of leakage current detection subsystems, and a controller; the detection unit is a photovoltaic string, or a maximum power point tracking circuit composed of at least two sets of photovoltaic strings connected in parallel, and the photovoltaic string includes at least two photovoltaic modules. The grounding subsystem is connected to the positive and negative poles of the DC bus formed by all the detection units, the controller, and the ground. Each detection unit corresponds to a set of leakage current detection subsystems. The leakage current detection subsystem is set between the corresponding detection unit and the grounding subsystem and is connected to the controller. The controller is connected to both the grounding subsystem and the leakage current detection subsystem. The method is executed by the controller and includes: Control the grounding subsystem to perform a grounding switching operation to connect the positive or negative terminal of the DC bus to the ground; The insulation fault detection system is controlled to form an independent measurement loop for the currently tested detection unit; The leakage current value flowing through the current test unit is collected by a leakage current detection subsystem that is set between the current test unit and the grounding subsystem. Receive the leakage current value collected by the leakage current detection subsystem; The leakage current value is processed using a preset value, and the location range of the target photovoltaic module where the insulation fault occurs is determined based on the processing result.

9. The insulation fault detection method as described in claim 8, characterized in that, The leakage current value includes a positive leakage current value and a negative leakage current value, and each detection unit corresponds to a positive leakage current value and a negative leakage current value. The step of processing the leakage current value using a preset value and determining the location range of the target photovoltaic module where the insulation fault occurs based on the processing result includes: When the detection unit is the photovoltaic string, under the independent measurement circuit for the Mth photovoltaic string, if the positive leakage current value IMK+ of the Mth photovoltaic string is greater than the first positive leakage current threshold, and / or the negative leakage current value IMK- is greater than the first negative leakage current threshold, or if the absolute difference between the positive leakage current value IMK+ and the negative leakage current value IMK- is greater than the first preset difference threshold, then the Mth photovoltaic string is determined to be a photovoltaic string with an insulation fault, where M is a positive integer greater than or equal to 1; The percentage of fault locations, a, of the Mth photovoltaic string is calculated using the formula a = |IMK-| / (|IMK-| + |IMK+|). Based on the percentage of fault location 'a' and the number of photovoltaic modules 'N' contained in the Mth photovoltaic string, the location range of the target photovoltaic module with insulation fault is determined.

10. The insulation fault detection method as described in claim 8, characterized in that, The leakage current value includes a positive leakage current value and a negative leakage current value, and each detection unit corresponds to a positive leakage current value and a negative leakage current value. The step of processing the leakage current value using a preset value and determining the location range of the target photovoltaic module where the insulation fault occurs based on the processing result includes: When the detection unit is the maximum power point tracking circuit, under an independent measurement loop for the Nth maximum power point tracking circuit, if the positive leakage current value INK+ is greater than the second positive leakage current threshold, and / or the negative leakage current value INK- is greater than the second negative leakage current threshold, or if the absolute difference between the positive leakage current value INK+ and the negative leakage current value INK- is greater than the second preset difference threshold, then the Nth maximum power point tracking circuit is determined to be the target circuit with an insulation fault, where N is a positive integer greater than or equal to 1; After identifying the faulty photovoltaic string from the target circuit, the percentage of faulty locations b in the faulty photovoltaic string is determined according to the formula b = |INK-| / (|INK-| + |INK+|). Based on the percentage of fault locations b and the number of photovoltaic modules in the photovoltaic string, the location range of the target photovoltaic module where the insulation fault occurred is determined.

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