Insulation impedance detection method and device, photovoltaic system fault positioning method and system

Abstract

The application discloses an insulation impedance detection method and device, a photovoltaic system fault positioning method and system, and relates to the technical field of power generation. The insulation impedance detection method comprises the following steps: acquiring p sets of resistance disturbance parameters and q sets of voltage disturbance parameters of a photovoltaic system; determining p resistance disturbance equations corresponding to the p sets of resistance disturbance parameters and q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters by using Kirchhoff's law; combining the p resistance disturbance equations and the q voltage disturbance equations to obtain a (p+q) -element linear equation set; and solving the (p+q) -element linear equation set to obtain a negative electrode insulation impedance parallel and n positive electrode insulation impedances. According to the embodiment of the application, the positive electrode insulation impedance corresponding to each photovoltaic component in the photovoltaic system can be determined, which provides a reference for subsequent positioning of a photovoltaic component branch with a fault, and thus the efficiency of later manual operation and maintenance is improved.

Description

Technical Field

[0001] This application belongs to the field of power generation technology, specifically relating to an insulation impedance detection method, device, photovoltaic system fault location method and system. Background Technology

[0002] As a core carrier of clean energy, the safety and reliability of photovoltaic (PV) systems directly affect the stable operation of the power grid and the safety of people and property. Inverters, as key equipment connecting PV arrays to the power grid, undertake the core function of power conversion. However, in complex external environments (such as high temperature, high humidity, and salt spray) and during long-term operation, components such as PV modules, cables, and connectors may experience a decline in insulation performance due to aging, damage, or deterioration of insulation materials, leading to serious accidents such as leakage current, equipment short circuits, and even fires. From a safety perspective, it is clearly required that PV systems have insulation resistance detection capabilities. When the insulation resistance of the positive and negative busbars to ground is lower than the threshold (usually 50kΩ / kW), the inverter must immediately disconnect from the grid and issue an alarm to prevent leakage current from flowing into the power grid or equipment casing through the grounding loop, causing the risk of electric shock. Therefore, insulation resistance detection is a mandatory requirement for ensuring equipment safety and a key measure to improve the system's economy and sustainability.

[0003] Insulation impedance detection methods in related technologies are mainly based on the bridge balance principle or the injection of low-frequency AC signals. They calculate the equivalent insulation resistance value by measuring the imbalance of voltage or current between the positive and negative buses and ground. However, these methods have significant limitations, namely, they cannot achieve independent detection of multiple inputs. Photovoltaic inverters typically connect multiple photovoltaic strings on the DC side (such as string inverters), while traditional technologies can only obtain the overall insulation impedance value of the positive and negative buses to ground, and cannot determine the positive insulation impedance of a specific photovoltaic string. Summary of the Invention

[0004] The technical problem to be solved by this application is to address the above-mentioned shortcomings of the existing technology by providing an insulation impedance detection method, device, photovoltaic system fault location method and system. Using the insulation impedance detection method, the positive insulation impedance corresponding to each photovoltaic module in the photovoltaic system can be determined, providing a reference for subsequent location of the faulty photovoltaic module branch, thereby improving the efficiency of subsequent manual operation and maintenance.

[0005] In a first aspect, embodiments of this application provide an insulation impedance detection method applied to a photovoltaic system, the photovoltaic system comprising:

[0006] There are n insulation impedance groups, each consisting of a positive insulation impedance and a negative insulation impedance connected in series, with the positive and negative insulation impedances grounded between them, where n is a positive integer.

[0007] n photovoltaic strings, with each photovoltaic string and its corresponding insulation impedance group connected in parallel between the positive bus and the negative bus;

[0008] There are n maximum power point tracking units, and each maximum power point tracking unit is connected to its corresponding photovoltaic string.

[0009] An insulation impedance measurement unit is connected to n maximum power point tracking units respectively;

[0010] The inverter is connected to the insulation resistance measurement unit;

[0011] The methods include:

[0012] Obtain p sets of resistance perturbation parameters and q sets of voltage perturbation parameters for the photovoltaic system. The resistance perturbation parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, as well as n first type of photovoltaic string voltages. The first type of photovoltaic string voltage corresponds one-to-one with the photovoltaic string. The voltage perturbation parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type of photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages. The second type of photovoltaic string voltage is the first type of photovoltaic string voltage with the largest value among the n first type of photovoltaic string voltages. The (n-1) third type of photovoltaic string voltages correspond one-to-one with the other (n-1) photovoltaic strings except for the target photovoltaic string. p and q are both positive integers, and p+q=n+1.

[0013] Using Kirchhoff's laws, we determine p resistance perturbation equations corresponding to p sets of resistance perturbation parameters, and q voltage perturbation equations corresponding to q sets of voltage perturbation parameters. Both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances. The parallel sum of negative electrode insulation impedances is the sum of n parallel negative electrode insulation impedances.

[0014] By simultaneously solving p resistance perturbation equations and q voltage perturbation equations, we obtain a system of (p+q) linear equations.

[0015] Solve the system of (p+q) linear equations to obtain the parallel sum of the negative electrode insulation impedances and the n positive electrode insulation impedances.

[0016] In some embodiments of the first aspect, the insulation impedance measuring unit includes a grounded first resistor;

[0017] p = 1, q = n = 3;

[0018] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, the updated first photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltage, which includes both the second and third photovoltaic string voltages. The updated first photovoltaic string voltage is greater than both the second and third photovoltaic string voltages.

[0019] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages as the updated first and third photovoltaic string voltages. The updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage.

[0020] The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the fourth type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated third type of photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages included in the third set of voltage disturbance parameters, including the updated first type of photovoltaic string voltage and the updated second type of photovoltaic string voltage. The updated third type of photovoltaic string voltage is greater than the updated first type of photovoltaic string voltage and is also greater than the updated second type of photovoltaic string voltage.

[0021] In some embodiments of the first aspect, the p resistance perturbation equations include a first resistance perturbation equation.

[0022] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0023] Determine the p resistance perturbation equations corresponding to each of the p groups of resistance perturbation parameters, specifically including:

[0024] The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero;

[0025] The first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

[0026] In some embodiments of the first aspect, the q voltage perturbation equations include a first voltage perturbation equation, a second voltage perturbation equation, and a third voltage perturbation equation;

[0027] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0028] Determine the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters, specifically including:

[0029] The first voltage disturbance equation is determined to be that the sum of the sixth, seventh, eighth, ninth, and tenth currents is zero;

[0030] Among them, the sixth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic module to the insulation resistance of the first positive electrode; the seventh current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the second photovoltaic string to the insulation resistance of the second positive electrode; the eighth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the third photovoltaic string to the insulation resistance of the third positive electrode; the ninth current is the ratio of the voltage of the second negative busbar to ground to the parallel sum of the insulation resistance of the negative electrode; the tenth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic string to the first resistor.

[0031] The second voltage disturbance equation is determined to be that the sum of the eleventh, twelfth, thirteenth, fourteenth, and fifteenth currents is zero;

[0032] Among them, the eleventh current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the twelfth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the thirteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourteenth current is the ratio of the voltage of the third negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the fifteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the first resistance.

[0033] The third voltage disturbance equation is determined to be that the sum of the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth currents is zero;

[0034] Among them, the sixteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the seventeenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the eighteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the insulation impedance of the third positive terminal; the nineteenth current is the ratio of the voltage of the fourth negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the twentieth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the first resistance.

[0035] In some embodiments of the first aspect, the insulation impedance measuring unit includes a second resistor, a first switch, a second switch and a third resistor connected in sequence, with the first switch and the second switch grounded between them;

[0036] p = q = 2, n = 3;

[0037] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0038] The first type of negative busbar voltage to ground includes the fifth negative busbar voltage to ground and the sixth negative busbar voltage to ground; the fifth busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is on and the second switch is off; the sixth negative busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is off and the second switch is on.

[0039] The first type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the fifth negative busbar is the second resistance;

[0040] The second type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the sixth negative busbar is the third type of resistance;

[0041] The n type I photovoltaic string voltages include the fourth photovoltaic string voltage, the fifth photovoltaic string voltage, and the sixth photovoltaic string voltage;

[0042] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the seventh negative bus voltage to ground; the first set of voltage disturbance parameters includes the second type of resistance, which is the second resistance; the first set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated fourth photovoltaic string voltage; the first set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the fifth photovoltaic string voltage and the sixth photovoltaic string voltage; the updated fourth photovoltaic string voltage is greater than the fifth photovoltaic string voltage and greater than the sixth photovoltaic string voltage.

[0043] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the eighth negative bus voltage to ground; the second type of resistance, which is the second resistance; the second type of photovoltaic string voltage, which is the updated fifth photovoltaic string voltage; and the (n-1) third type of photovoltaic string voltage, which includes the updated fourth and sixth photovoltaic string voltages. The updated fifth photovoltaic string voltage is greater than the updated fourth photovoltaic string voltage and is also greater than the sixth photovoltaic string voltage.

[0044] In some embodiments of the first aspect, the p resistance perturbation equations include a second resistance perturbation equation and a third resistance perturbation equation;

[0045] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0046] Determine the p resistance perturbation equations corresponding to each of the p groups of resistance perturbation parameters, specifically including:

[0047] The second resistor perturbation equation is determined to be that the sum of the twenty-first, twenty-second, twenty-third, twenty-fourth, and twenty-fifth currents is zero;

[0048] Among them, the twenty-first current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-second current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-third current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-fourth current is the ratio of the voltage of the fifth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the twenty-fifth current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the second resistance.

[0049] The third resistor perturbation equation is determined to be that the sum of the twenty-sixth, twenty-seventh, twenty-eighth, twenty-ninth, and thirtieth currents is zero;

[0050] Among them, the twenty-sixth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-seventh current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-eighth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-ninth current is the ratio of the voltage of the sixth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; and the thirtieth current is the ratio of the voltage of the sixth negative busbar to ground to the third resistance.

[0051] In some embodiments of the first aspect, the q voltage perturbation equations include a fourth voltage perturbation equation and a fifth voltage perturbation equation;

[0052] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0053] Determine the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters, specifically including:

[0054] The fourth voltage disturbance equation is determined to be that the sum of the thirty-first, thirty-second, thirty-third, thirty-fourth, and thirty-fifth currents is zero;

[0055] Among them, the thirty-first current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive terminal; the thirty-second current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the thirty-third current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the thirty-fourth current is the ratio of the voltage of the seventh negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the thirty-fifth current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the second resistance.

[0056] The fifth voltage disturbance equation is determined to be that the sum of the thirty-sixth, thirty-seventh, thirty-eighth, thirty-ninth, and fortieth currents is zero;

[0057] Among them, the thirty-sixth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive pole; the thirty-seventh current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive pole; the thirty-eighth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive pole; the thirty-ninth current is the ratio of the voltage of the eighth negative busbar to ground to the parallel sum of the insulation impedance of the negative pole; and the fortieth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fifth photovoltaic string to the second resistance.

[0058] In some embodiments of the first aspect, solving a system of (p+q) linear equations yields the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances, specifically including:

[0059] The Gaussian elimination method is used to solve the (p+q)-element linear equation system to obtain the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances.

[0060] Based on the same inventive concept, in a second aspect, embodiments of this application also provide a photovoltaic system fault location method, comprising:

[0061] According to the insulation impedance detection method of any one of the first aspects, determine the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances of the photovoltaic system.

[0062] Based on the parallel connection of the negative electrode insulation impedance and the insulation impedance of n positive electrodes, locate the faulty photovoltaic module branch in the photovoltaic system.

[0063] Based on the same inventive concept, in a third aspect, embodiments of this application also provide an insulation resistance detection device applied to a photovoltaic system, the photovoltaic system comprising:

[0064] There are n insulation impedance groups, each consisting of a positive insulation impedance and a negative insulation impedance connected in series, with the positive and negative insulation impedances grounded between them, where n is a positive integer.

[0065] n photovoltaic strings, with each photovoltaic string and its corresponding insulation impedance group connected in parallel between the positive bus and the negative bus;

[0066] There are n maximum power point tracking units, and each maximum power point tracking unit is connected to its corresponding photovoltaic string.

[0067] An insulation impedance measurement unit is connected to n maximum power point tracking units respectively;

[0068] The inverter is connected to the insulation resistance measurement unit;

[0069] The device includes:

[0070] The acquisition module is used to acquire p groups of resistance disturbance parameters and q groups of voltage disturbance parameters of the photovoltaic system. The resistance disturbance parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, as well as n first type of photovoltaic string voltages. The first type of photovoltaic string voltage corresponds one-to-one with the photovoltaic string. The voltage disturbance parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type of photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages. p and q are both positive integers, and p+q=n+1.

[0071] The first determining module, connected to the acquisition module, is used to determine, using Kirchhoff's laws, p resistance perturbation equations corresponding to p sets of resistance perturbation parameters, and q voltage perturbation equations corresponding to q sets of voltage perturbation parameters; both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances; the parallel sum of negative electrode insulation impedances is the sum of n parallel negative electrode insulation impedances;

[0072] The simultaneous equation module, connected to the first determining module, is used to simultaneously solve p resistance perturbation equations and q voltage perturbation equations to obtain a system of (p+q) linear equations.

[0073] The solver module, connected to the simultaneous equations module, is used to solve a system of (p+q) linear equations to obtain the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances.

[0074] In some embodiments of the third aspect, the insulation impedance measuring unit includes a grounded first resistor;

[0075] p = 1, q = n = 3;

[0076] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0077] The first type of negative busbar voltage to ground includes the first negative busbar voltage to ground;

[0078] The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor;

[0079] The n type I photovoltaic string voltages include the first photovoltaic string voltage, the second photovoltaic string voltage, and the third photovoltaic string voltage;

[0080] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, the updated first photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltage, which includes both the second and third photovoltaic string voltages. The updated first photovoltaic string voltage is greater than both the second and third photovoltaic string voltages.

[0081] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages as the updated first and third photovoltaic string voltages. The updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage.

[0082] The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the fourth type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated third type of photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages included in the third set of voltage disturbance parameters, including the updated first type of photovoltaic string voltage and the updated second type of photovoltaic string voltage. The updated third type of photovoltaic string voltage is greater than the updated first type of photovoltaic string voltage and is also greater than the updated second type of photovoltaic string voltage.

[0083] In some embodiments of the third aspect, the p resistance perturbation equations include the first resistance perturbation equation.

[0084] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0085] The first determining module is specifically used for:

[0086] The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero;

[0087] The first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

[0088] Based on the same inventive concept, in a fourth aspect, embodiments of this application also provide a photovoltaic system fault location system, comprising:

[0089] According to any of the third aspects, the insulation impedance detection device is used to determine the parallel insulation impedance of the negative electrode of the photovoltaic system and the insulation impedance of the n positive electrodes.

[0090] The locating device, connected to the insulation impedance detection device, is used to locate the faulty photovoltaic module branch in the photovoltaic system based on the parallel connection of the negative electrode insulation impedance and the insulation impedance of n positive electrodes.

[0091] According to the insulation impedance detection method, device, photovoltaic system fault location method, and system provided in this application, p sets of resistance disturbance parameters and q sets of voltage disturbance parameters of the photovoltaic system are first obtained. Then, Kirchhoff's laws are used to determine p resistance disturbance equations corresponding to the p sets of resistance disturbance parameters and q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters. Next, the p resistance disturbance equations and q voltage disturbance equations are solved simultaneously to obtain a system of (p+q) linear equations. The system of (p+q) linear equations is then solved to obtain the parallel sum of negative insulation impedances and n positive insulation impedances. In other words, this application constructs multiple balanced bridge states through resistance disturbances and photovoltaic string disturbances, thereby constructing a system of (p+q) linear equations. Ultimately, the parallel sum of negative insulation impedances and the n positive insulation impedances corresponding to the n photovoltaic strings can be solved, providing a reference for locating faulty photovoltaic module branches and improving the efficiency of subsequent manual maintenance. Attached Figure Description

[0092] Figure 1 This diagram illustrates a structural schematic of a photovoltaic system in related technologies.

[0093] Figure 2 A schematic diagram of a maximum power point tracking unit in related technologies is shown.

[0094] Figure 3 This diagram illustrates another structural schematic of the maximum power point tracking unit in the related technology;

[0095] Figure 4 This diagram illustrates yet another structural schematic of a maximum power point tracking unit in the related technology;

[0096] Figure 5 A schematic diagram of an insulation impedance measurement unit in related technologies is shown.

[0097] Figure 6 This diagram illustrates another structural schematic of an insulation impedance measurement unit in related technologies;

[0098] Figure 7 This diagram illustrates yet another structural schematic of an insulation impedance measurement unit in the related technology;

[0099] Figure 8 This illustration shows a flowchart of an insulation resistance detection method provided in an embodiment of this application.

[0100] Figure 9 This diagram illustrates another structural schematic of a photovoltaic system in related technologies;

[0101] Figure 10 This diagram illustrates yet another structural schematic of a photovoltaic system in related technologies;

[0102] Figure 11 Show Figure 9 An equivalent circuit diagram of a photovoltaic system;

[0103] Figure 12 Show Figure 9 Another equivalent circuit diagram of a photovoltaic system;

[0104] Figure 13 Show Figure 9 Another equivalent circuit diagram of a photovoltaic system;

[0105] Figure 14 Show Figure 9 Another equivalent circuit diagram of a photovoltaic system;

[0106] Figure 15 Show Figure 10 An equivalent circuit diagram of a photovoltaic system;

[0107] Figure 16 Show Figure 10 Another equivalent circuit diagram of a photovoltaic system;

[0108] Figure 17 Show Figure 10 Another equivalent circuit diagram of a photovoltaic system;

[0109] Figure 18 Show Figure 10 Another equivalent circuit diagram of a photovoltaic system;

[0110] Figure 19 This is a schematic diagram of an insulation resistance detection device provided in an embodiment of this application. Detailed Implementation

[0111] To enable those skilled in the art to better understand the technical solutions of this application, the application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0112] The features and exemplary embodiments of various aspects of this application will now be described in detail. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain this application and are not configured to limit this application. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples of this application.

[0113] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0114] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0115] Example 1

[0116] The insulation impedance detection method provided in this application is applicable to the fault location process of photovoltaic systems. This insulation impedance detection method can be applied to photovoltaic systems and can be executed by an insulation impedance detection device, a controller in the photovoltaic system, and electronic equipment. The following description uses the execution of this insulation impedance detection method by electronic equipment as an example.

[0117] The photovoltaic system in the related technology includes: n insulation impedance groups, n photovoltaic strings, n maximum power point tracking units, insulation impedance measurement units, and inverters.

[0118] There are n insulation impedance groups, each consisting of a positive insulation impedance and a negative insulation impedance connected in series, with the positive and negative insulation impedances grounded between them, where n is a positive integer.

[0119] For example, the positive insulation resistance is the insulation resistance of the positive terminal to the ground; the negative insulation resistance is the insulation resistance of the negative terminal to the ground.

[0120] For example, such as Figure 1 As shown, the first insulation resistance group includes the first positive insulation resistance R. x1 And the first negative electrode insulation resistance R y1 The second insulation resistance group includes the second positive insulation resistance R. x2 And the insulation resistance of the second negative electrode R y2 Similarly, the nth insulation impedance group includes the third positive insulation impedance R. xnAnd the third negative electrode insulation resistance R yn The first positive electrode insulation resistance R x1 Insulation resistance R with the first negative terminal y1 The second positive terminal is grounded, and the insulation resistance is R. x2 Insulation resistance R with the second negative electrode y2 Grounded between, ..., the insulation resistance R of the nth positive terminal xn Insulation resistance R with the nth negative pole yn Grounding between them.

[0121] It should be noted that the value of n can be set according to the actual situation, and is not limited here.

[0122] n photovoltaic strings are connected in parallel between the positive busbar and the negative busbar, with each photovoltaic string and its corresponding insulation impedance group connected in parallel.

[0123] For example, such as Figure 1 As shown, the first photovoltaic string PV is connected in parallel with the first insulation impedance group between the positive bus BUS+ and the negative bus BUS-; the second photovoltaic string PV is connected in parallel with the second insulation impedance group between the positive bus BUS+ and the negative bus BUS-; and so on, the nth photovoltaic string PV is connected in parallel with the nth insulation impedance group between the positive bus BUS+ and the negative bus BUS-.

[0124] There are n maximum power point tracking units, and each maximum power point tracking unit is connected to its corresponding photovoltaic string.

[0125] For example, such as Figure 1 As shown, the first photovoltaic string PV is connected to the first maximum power point tracking unit MPPT1; the second photovoltaic string PV is connected to the second maximum power point tracking unit MPPT2; and the nth photovoltaic string PV is connected to the nth maximum power point tracking unit MPPTn.

[0126] For example, the first maximum power point tracking unit MPPT1 to the nth maximum power point tracking unit MPPTn are all boost converters.

[0127] For example, the maximum power point tracking unit may include, as shown below: Figure 2 The two-level Boost topology shown is as follows: Figure 3 The dual-symmetric Boost three-level topology shown, and as Figure 4 The flying capacitor Boost three-level topology is shown. Figures 2 to 4 In the diagram, S1 to S2 represent switches; L1 represents an inductor; D1 and D2 represent diodes; Cf represents a flying capacitor; and C1 and C2 represent capacitors. For detailed information on the components and connections within the maximum power point tracking unit, please refer to [link to documentation]. Figures 2 to 4 This will not be elaborated upon here.

[0128] An insulation impedance measurement unit is connected to n maximum power point tracking units respectively.

[0129] For example, such as Figure 1 As shown, the first maximum power point tracking unit MPPT1 to the nth maximum power point tracking unit MPPTn are all connected to the insulation resistance measurement unit.

[0130] For example, the insulation resistance measurement unit may be a variable resistor network including resistors and switches.

[0131] As an example, such as Figure 5 As shown, the insulation impedance measurement unit may include a first resistor R1, which is connected between the positive bus BUS+ and ground.

[0132] As another example, such as Figure 6 As shown, the insulation impedance measurement unit may include a second resistor R2, a third resistor R3, a first switch K1, and a second switch K2; wherein, the second resistor R2, the first switch K1, the second switch K2, and the third resistor R3 are connected in series between the positive busbar BUS+ and the negative busbar BUS-, and the first switch K1 and the second switch K2 are grounded.

[0133] As yet another example, such as Figure 7 As shown, the insulation impedance measurement unit may include a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a third switch K3, and a fourth switch K4; wherein, the fourth resistor R4, the third switch K3, the fourth switch K4, and the fifth resistor R5 are connected in series between the positive bus BUS+ and the negative bus BUS-, and the third switch K3 and the fourth switch K4 are grounded through the sixth resistor R6.

[0134] The inverter is connected to the insulation resistance measurement unit.

[0135] It should be added that, in Figure 1 In the middle, V P1 V is the positive voltage of the first photovoltaic string. N1 V is the negative voltage of the first photovoltaic string. PV1 V is the difference between the positive and negative voltages of the first photovoltaic string; P2 V is the positive voltage of the second photovoltaic string. N2 V is the negative voltage of the second photovoltaic string. PV2 V is the difference between the positive and negative voltages of the second photovoltaic string; and so on, V Pn V is the positive voltage of the nth photovoltaic string. Nn V is the negative voltage of the nth photovoltaic string. PVn It is the difference between the positive and negative voltages of the nth photovoltaic string.

[0136] like Figure 8 As shown, the insulation resistance detection method provided in this application embodiment may include steps S110 to S140.

[0137] S110. Obtain the p-group resistance disturbance parameters and q-group voltage disturbance parameters of the photovoltaic system; the resistance disturbance parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, as well as n first type photovoltaic string voltages; the first type photovoltaic string voltages correspond one-to-one with the photovoltaic strings; the voltage disturbance parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type photovoltaic string voltage, and (n-1) third type photovoltaic string voltages; p and q are both positive integers, and p+q=n+1.

[0138] S120. Using Kirchhoff's laws, determine the p resistance perturbation equations corresponding to the p sets of resistance perturbation parameters, and determine the q voltage perturbation equations corresponding to the q sets of voltage perturbation parameters. Both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances. The parallel sum of negative electrode insulation impedances is the sum of the parallel sum of n negative electrode insulation impedances.

[0139] S130. By simultaneously solving p resistance perturbation equations and q voltage perturbation equations, we obtain a system of (p+q) linear equations.

[0140] S140. Solve the system of linear equations in the (p+q) variables to obtain the parallel sum of the negative electrode insulation impedances and the n positive electrode insulation impedances.

[0141] According to the insulation impedance detection method provided in this application, p sets of resistance disturbance parameters and q sets of voltage disturbance parameters of the photovoltaic system are first obtained. Then, Kirchhoff's laws are used to determine p resistance disturbance equations corresponding to the p sets of resistance disturbance parameters and q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters. Next, the p resistance disturbance equations and q voltage disturbance equations are solved simultaneously to obtain a system of (p+q) linear equations. The system of (p+q) linear equations is then solved to obtain the parallel sum of negative insulation impedances and n positive insulation impedances. In other words, this application constructs multiple balanced bridge states through resistance disturbances and photovoltaic string disturbances, thereby constructing a system of (p+q) linear equations. Finally, the parallel sum of negative insulation impedances and the n positive insulation impedances corresponding to the n photovoltaic strings can be solved, providing a reference for locating faulty photovoltaic module branches and improving the efficiency of subsequent manual maintenance.

[0142] The specific implementation methods for each of the above steps are described below.

[0143] In step S110, for example, the p-group resistance perturbation parameters and q-group voltage perturbation parameters of the photovoltaic system can be obtained by measurement.

[0144] It should be noted that the values ​​of p and q can be set according to the actual situation and are not limited here. For example, p = 1, q = 3, or p = q = 2, etc.

[0145] In some implementations, the insulation impedance measuring unit includes a grounded first resistor;

[0146] p = 1, q = n = 3;

[0147] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0148] The first type of negative busbar voltage to ground includes the first negative busbar voltage to ground;

[0149] The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor;

[0150] The n type I photovoltaic string voltages include the first photovoltaic string voltage, the second photovoltaic string voltage, and the third photovoltaic string voltage;

[0151] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, the updated first photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltage, which includes both the second and third photovoltaic string voltages. The updated first photovoltaic string voltage is greater than both the second and third photovoltaic string voltages.

[0152] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages as the updated first and third photovoltaic string voltages. The updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage.

[0153] The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the fourth type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated third type of photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages included in the third set of voltage disturbance parameters, including the updated first type of photovoltaic string voltage and the updated second type of photovoltaic string voltage. The updated third type of photovoltaic string voltage is greater than the updated first type of photovoltaic string voltage and is also greater than the updated second type of photovoltaic string voltage.

[0154] For example, such as Figure 9 As shown, the insulation impedance measurement unit includes a grounded first resistor R1, and the photovoltaic system includes a first photovoltaic string, a second photovoltaic string, and a third photovoltaic string. Specifically, the first photovoltaic string is the first photovoltaic string PV in the photovoltaic system, the second photovoltaic string is the second photovoltaic string PV in the photovoltaic system, and the third photovoltaic string is the third photovoltaic string PV in the photovoltaic system.

[0155] For example, the voltage of the first negative busbar to ground is as follows: Figure 9 In the photovoltaic system shown, the measured voltage of the negative busbar (BUS-) to ground can be denoted as V. BUS11- .

[0156] For example, such as Figure 9 As shown, the first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor R1.

[0157] For example, the voltage of the first photovoltaic string can be Figure 9 The voltage of the first photovoltaic string in the middle, that is Figure 9 V in PV1 The voltage of the second photovoltaic string can be... Figure 9 The voltage of the second photovoltaic string in the middle, that is Figure 9 V in PV2 The voltage of the third photovoltaic string can be... Figure 9 The voltage of the third photovoltaic string in the middle, that is Figure 9 V in PV3 .

[0158] For example, the voltage to ground of the second negative busbar can be as follows: Figure 9 In the photovoltaic system shown, when the voltage of the first photovoltaic string is at its maximum value, the measured voltage of the negative busbar to ground can be denoted as V. BUS12-The updated voltage of the first photovoltaic string can be the maximum value among the voltages of the second, third, and updated photovoltaic strings. That is, increasing the voltage of the first photovoltaic string yields the updated voltage, which is greater than both the second and third photovoltaic string voltages. The updated voltage of the first photovoltaic string can be denoted as V. PV11 .

[0159] For example, the voltage to ground of the third negative busbar can be as follows: Figure 9 In the photovoltaic system shown, when the voltage of the second photovoltaic string is at its maximum value, the measured voltage of the negative busbar to ground can be denoted as V. BUS13- The updated second photovoltaic string voltage can be the maximum value among the updated first photovoltaic string voltage, the third photovoltaic string voltage, and the updated second photovoltaic string voltage. That is, increasing the second photovoltaic string voltage yields the updated second photovoltaic string voltage, ensuring that the updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and also greater than the third photovoltaic string voltage. The updated second photovoltaic string voltage can be denoted as V. PV21 .

[0160] For example, the voltage to ground of the fourth negative busbar can be as follows: Figure 9 In the photovoltaic system shown, when the voltage of the third photovoltaic string is at its maximum value, the measured voltage of the negative busbar to ground can be denoted as V. BUS14- The updated third photovoltaic string voltage can be the maximum value among the updated first photovoltaic string voltage, the updated second photovoltaic string voltage, and the updated third photovoltaic string voltage. That is, increasing the third photovoltaic string voltage to obtain the updated third photovoltaic string voltage results in a voltage greater than the updated first photovoltaic string voltage, and also greater than the updated third photovoltaic string voltage. The updated third photovoltaic string voltage can be denoted as V. PV31 .

[0161] In other embodiments, the insulation impedance measuring unit includes a second resistor, a first switch, a second switch, and a third resistor connected in sequence, with the first switch and the second switch grounded between them;

[0162] p = q = 2, n = 3;

[0163] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0164] The first type of negative busbar voltage to ground includes the fifth negative busbar voltage to ground and the sixth negative busbar voltage to ground; the fifth busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is on and the second switch is off; the sixth negative busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is off and the second switch is on.

[0165] The first type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the fifth negative busbar is the second resistance;

[0166] The second type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the sixth negative busbar is the third type of resistance;

[0167] The n type I photovoltaic string voltages include the fourth photovoltaic string voltage, the fifth photovoltaic string voltage, and the sixth photovoltaic string voltage;

[0168] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the seventh negative bus voltage to ground; the first set of voltage disturbance parameters includes the second type of resistance, which is the second resistance; the first set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated fourth photovoltaic string voltage; the first set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the fifth photovoltaic string voltage and the sixth photovoltaic string voltage; the updated fourth photovoltaic string voltage is greater than the fifth photovoltaic string voltage and greater than the sixth photovoltaic string voltage.

[0169] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the eighth negative bus voltage to ground; the second type of resistance, which is the second resistance; the second type of photovoltaic string voltage, which is the updated fifth photovoltaic string voltage; and the (n-1) third type of photovoltaic string voltage, which includes the updated fourth and sixth photovoltaic string voltages. The updated fifth photovoltaic string voltage is greater than the updated fourth photovoltaic string voltage and is also greater than the sixth photovoltaic string voltage.

[0170] For example, such as Figure 10 As shown, the insulation impedance measurement unit includes a second resistor R2, a first switch K1, a second switch K2 and a third resistor R3 connected in sequence, with the first switch K1 and the second switch K2 grounded together.

[0171] For example, the voltage of the fourth photovoltaic string can be Figure 10 The voltage of the first photovoltaic string; the voltage of the fifth photovoltaic string can be... Figure 10 The voltage of the second photovoltaic string; the voltage of the sixth photovoltaic string can be... Figure 10 The voltage of the third photovoltaic string in the middle. Figure 10 In the middle, V P4 V is the positive voltage of the first photovoltaic string. N4 V is the negative voltage of the first photovoltaic string. PV4 V is the difference between the positive and negative voltages of the first photovoltaic string, which is also the voltage of the fourth photovoltaic string; P5 V is the positive voltage of the second photovoltaic string. N5 V is the negative voltage of the second photovoltaic string.PV5 V is the difference between the positive and negative voltages of the second photovoltaic string, which is also the voltage of the fifth photovoltaic string; P6 V is the positive voltage of the third photovoltaic string. N6 V is the negative voltage of the third photovoltaic string. PV6 This is the difference between the positive and negative voltages of the third photovoltaic string, which is also the voltage of the sixth photovoltaic string.

[0172] For example, the voltage to ground of the fifth negative busbar can be as follows: Figure 10 In the photovoltaic system shown, the voltage of the negative busbar to ground when the first switch K1 is on and the second switch K2 is off can be denoted as V. BUS21- The voltage to ground of the sixth negative busbar can be as follows: Figure 10 In the photovoltaic system shown, the voltage of the negative busbar to ground when the first switch K1 is off and the second switch K2 is on can be denoted as V. BUS22- .

[0173] For example, such as Figure 10 As shown, the first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the fifth negative busbar is the second resistor R2; the second type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the sixth negative busbar is the third resistor R3.

[0174] For example, the voltage to ground of the seventh negative busbar can be as follows: Figure 10 In the photovoltaic system shown, when the voltage of the fourth photovoltaic string is updated, the voltage of the negative busbar to ground measured can be denoted as V. BUS23- Specifically, the updated voltage of the fourth photovoltaic string can be obtained by increasing the voltage of the fourth photovoltaic string. The updated voltage of the fourth photovoltaic string is greater than the voltage of the fifth photovoltaic string and also greater than the voltage of the sixth photovoltaic string.

[0175] For example, the voltage to ground of the eighth negative busbar can be as follows: Figure 10 In the photovoltaic system shown, when the voltage of the fifth photovoltaic string is updated, the voltage of the negative busbar to ground measured can be denoted as V. BUS24- Specifically, the updated voltage of the fifth photovoltaic string can be obtained by increasing the voltage of the fifth photovoltaic string. The updated voltage of the fifth photovoltaic string is greater than the updated voltage of the fourth photovoltaic string, and also greater than the voltage of the sixth photovoltaic string.

[0176] In step S120, the electronic device can obtain the sum of the p groups of resistance perturbation parameters and the q groups of voltage perturbation parameters of the photovoltaic system. It can also use Kirchhoff's laws to determine the p resistance perturbation equations corresponding to the p groups of resistance perturbation parameters and the q voltage perturbation equations corresponding to the q groups of voltage perturbation parameters.

[0177] In some implementations, the p resistance perturbation equations include a first resistance perturbation equation.

[0178] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0179] Determine the p resistance perturbation equations corresponding to each of the p groups of resistance perturbation parameters, specifically including:

[0180] The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero;

[0181] The first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

[0182] For example, the first positive electrode insulation resistance is the first positive electrode insulation resistance; the second positive electrode insulation resistance is the second positive electrode insulation resistance; and the third positive electrode insulation resistance is the third positive electrode insulation resistance.

[0183] For example, Figure 9 The corresponding first equivalent circuit diagram is as follows: Figure 11 As shown, according to Kirchhoff's laws, the first resistance perturbation equation can be obtained, which includes formula (1).

[0184] Formula (1) includes:

[0185]

[0186] Among them, V BUS11- This represents the voltage to ground of the first negative busbar; V PV1 V represents the voltage of the first photovoltaic string; PV2 V represents the voltage of the second photovoltaic string; PV3 R represents the voltage of the third photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R1 represents the first resistance. Indicates the first current; Indicates the second current; Indicates the third current; Indicates the fourth current; This represents the fifth current.

[0187] In other embodiments, the p resistance perturbation equations include a second resistance perturbation equation and a third resistance perturbation equation;

[0188] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0189] Determine the p resistance perturbation equations corresponding to each of the p groups of resistance perturbation parameters, specifically including:

[0190] The second resistor perturbation equation is determined to be that the sum of the twenty-first, twenty-second, twenty-third, twenty-fourth, and twenty-fifth currents is zero;

[0191] Among them, the twenty-first current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-second current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-third current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-fourth current is the ratio of the voltage of the fifth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the twenty-fifth current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the second resistance.

[0192] The third resistor perturbation equation is determined to be that the sum of the twenty-sixth, twenty-seventh, twenty-eighth, twenty-ninth, and thirtieth currents is zero;

[0193] Among them, the twenty-sixth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-seventh current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-eighth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-ninth current is the ratio of the voltage of the sixth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; and the thirtieth current is the ratio of the voltage of the sixth negative busbar to ground to the third resistance.

[0194] For example, Figure 11 The equivalent circuit diagram when the first switch K1 is on and the second switch K2 is off is as follows: Figure 15 As shown, according to Kirchhoff's laws, the second resistance perturbation equation can be obtained, which includes formula (2).

[0195] Formula (2) includes:

[0196]

[0197] Among them, V BUS21- This represents the voltage to ground of the fifth negative busbar; V PV4 V represents the voltage of the fourth photovoltaic string; PV5 V represents the voltage of the fifth photovoltaic string; PV6 R represents the voltage of the sixth photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R2 represents the second resistor. This represents the twenty-first current; This indicates the twenty-second current; This indicates the twenty-third current; This indicates the twenty-fourth current; This represents the twenty-fifth current.

[0198] For example, Figure 11 The equivalent circuit diagram when the first switch K1 is off and the second switch K2 is on is as follows: Figure 16 As shown, according to Kirchhoff's laws, the third resistance perturbation equation can be obtained, which includes formula (3).

[0199] Formula (3) includes:

[0200]

[0201] Among them, V BUS22- This represents the voltage to ground of the sixth negative busbar; V PV4 V represents the voltage of the fourth photovoltaic string; PV5 V represents the voltage of the fifth photovoltaic string; PV6 R represents the voltage of the sixth photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R3 represents the parallel sum of the negative electrode insulation resistances; R3 represents the third resistor. This indicates the twenty-sixth current; This indicates the twenty-seventh current; This indicates the twenty-eighth current; This indicates the twenty-ninth current; This indicates the thirtieth current.

[0202] In some implementations, the q voltage perturbation equations include a first voltage perturbation equation, a second voltage perturbation equation, and a third voltage perturbation equation;

[0203] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0204] Determine the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters, specifically including:

[0205] The first voltage disturbance equation is determined to be that the sum of the sixth, seventh, eighth, ninth, and tenth currents is zero;

[0206] Among them, the sixth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic module to the insulation resistance of the first positive electrode; the seventh current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the second photovoltaic string to the insulation resistance of the second positive electrode; the eighth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the third photovoltaic string to the insulation resistance of the third positive electrode; the ninth current is the ratio of the voltage of the second negative busbar to ground to the parallel sum of the insulation resistance of the negative electrode; the tenth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic string to the first resistor.

[0207] The second voltage disturbance equation is determined to be that the sum of the eleventh, twelfth, thirteenth, fourteenth, and fifteenth currents is zero;

[0208] Among them, the eleventh current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the twelfth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the thirteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourteenth current is the ratio of the voltage of the third negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the fifteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the first resistance.

[0209] The third voltage disturbance equation is determined to be that the sum of the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth currents is zero;

[0210] Among them, the sixteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the seventeenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the eighteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the insulation impedance of the third positive terminal; the nineteenth current is the ratio of the voltage of the fourth negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the twentieth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the first resistance.

[0211] For example, adjust Figure 9 The voltage of the first photovoltaic string in the photovoltaic system shown is such that the updated voltage of the first photovoltaic string is greater than the voltage of the second photovoltaic string and also greater than the voltage of the third photovoltaic string. The resulting equivalent circuit diagram is as follows. Figure 12 As shown. According to Kirchhoff's laws, the first voltage perturbation equation can be obtained, which includes formula (4).

[0212] Formula (4) includes:

[0213]

[0214] Among them, V BUS12- This represents the voltage to ground of the second negative busbar; V PV11 V represents the updated voltage of the first photovoltaic string; PV2 V represents the voltage of the second photovoltaic string; PV3 R represents the voltage of the third photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R1 represents the first resistance. Indicates the sixth current; Indicates the seventh current; Indicates the eighth current; Indicates the ninth current; This indicates the tenth current.

[0215] For example, based on the previous step, adjust Figure 9 The second photovoltaic string voltage of the photovoltaic system shown is updated to be greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage. The resulting equivalent circuit diagram is shown below. Figure 13 As shown. According to Kirchhoff's laws, the second voltage perturbation equation can be obtained, which includes formula (5).

[0216] Formula (5) includes:

[0217]

[0218] Among them, V BUS13- This represents the voltage to ground of the third negative busbar; V PV11 V represents the updated voltage of the first photovoltaic string; PV21 This indicates the updated voltage of the second photovoltaic string; V PV3 R represents the voltage of the third photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R1 represents the first resistance. Indicates the eleventh current; Indicates the twelfth current; Indicates the thirteenth current; Indicates the fourteenth current; This indicates the fifteenth current.

[0219] For example, based on the previous step, adjust Figure 9 The voltage of the third photovoltaic string in the photovoltaic system shown is updated to be greater than the updated voltage of the first photovoltaic string and also greater than the updated voltage of the second photovoltaic string. The resulting equivalent circuit diagram is shown below. Figure 14 As shown. According to Kirchhoff's laws, the second voltage perturbation equation can be obtained, which includes formula (6).

[0220] Formula (6) includes:

[0221]

[0222] Among them, V BUS14- This represents the voltage to ground of the fourth negative busbar; V PV11 V represents the updated voltage of the first photovoltaic string; PV21 This indicates the updated voltage of the second photovoltaic string; V PV31 Indicates the updated voltage of the third photovoltaic string; R x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R1 represents the first resistance. Indicates the sixteenth current; This indicates the seventeenth current; Indicates the eighteenth current; Indicates the nineteenth current; This indicates the twentieth current.

[0223] In other embodiments, the q voltage perturbation equations include a fourth voltage perturbation equation and a fifth voltage perturbation equation;

[0224] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0225] Determine the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters, specifically including:

[0226] The fourth voltage disturbance equation is determined to be that the sum of the thirty-first, thirty-second, thirty-third, thirty-fourth, and thirty-fifth currents is zero;

[0227] Among them, the thirty-first current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive terminal; the thirty-second current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the thirty-third current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the thirty-fourth current is the ratio of the voltage of the seventh negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the thirty-fifth current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the second resistance.

[0228] The fifth voltage disturbance equation is determined to be that the sum of the thirty-sixth, thirty-seventh, thirty-eighth, thirty-ninth, and fortieth currents is zero;

[0229] Among them, the thirty-sixth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive pole; the thirty-seventh current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive pole; the thirty-eighth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive pole; the thirty-ninth current is the ratio of the voltage of the eighth negative busbar to ground to the parallel sum of the insulation impedance of the negative pole; and the fortieth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fifth photovoltaic string to the second resistance.

[0230] For example, when the first switch K1 is on and the second switch K2 is off, adjust Figure 10 The voltage of the fourth photovoltaic string in the photovoltaic system shown is such that the updated voltage of the fourth photovoltaic string is greater than the voltage of the fifth photovoltaic string and also greater than the voltage of the sixth photovoltaic string. The resulting equivalent circuit diagram is as follows. Figure 17 As shown. According to Kirchhoff's laws, the fourth voltage perturbation equation can be obtained, which includes formula (7).

[0231] Formula (7) includes:

[0232]

[0233] Among them, V BUS23- This represents the voltage to ground of the seventh negative busbar; V PV41 This indicates the updated voltage of the fourth photovoltaic string; V PV5 V represents the voltage of the fifth photovoltaic string; PV6 R represents the voltage of the sixth photovoltaic string; x1R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R2 represents the second resistor. This represents the thirty-first current; This represents the thirty-second current; This represents the thirty-third current; This indicates the thirty-fourth current; This represents the thirty-fifth current.

[0234] For example, when the first switch K1 is on and the second switch K2 is off, the adjustment is made based on the previous step. Figure 10 The voltage of the fifth photovoltaic string in the photovoltaic system shown is such that the updated voltage of the fifth photovoltaic string is greater than the updated voltage of the fourth photovoltaic string, and also greater than the voltage of the sixth photovoltaic string. The resulting equivalent circuit diagram is as follows. Figure 18 As shown. According to Kirchhoff's laws, the fourth voltage perturbation equation can be obtained, which includes formula (8).

[0235] Formula (8) includes:

[0236]

[0237] Among them, V BUS24- This represents the voltage to ground of the eighth negative busbar; V PV41 This indicates the updated voltage of the fourth photovoltaic string; V PV51 This indicates the updated voltage of the fifth photovoltaic string; V PV6 R represents the voltage of the sixth photovoltaic string; x1 R represents the insulation resistance of the first positive electrode; x2 R represents the insulation resistance of the second positive electrode. x3 R represents the insulation resistance of the third positive electrode. y R1 represents the parallel sum of the negative electrode insulation resistances; R2 represents the second resistor. This represents the thirty-sixth current; This represents the thirty-seventh current; This indicates the thirty-eighth current; This represents the thirty-ninth current; This indicates the 40th current.

[0238] It should be noted that, since inductor L1 and switch S1 are in the open state, they are not shown in the equivalent circuit above.

[0239] It should be added that photovoltaic voltage disturbances can be achieved through power optimizers or by running the converter under no-load conditions. The updated photovoltaic module voltage can be determined by sampling the analog signals inside the converter.

[0240] In step S130, after the electronic device uses Kirchhoff's laws to determine the p resistance perturbation equations corresponding to the p sets of resistance perturbation parameters and the q voltage perturbation equations corresponding to the q sets of voltage perturbation parameters, it can also simultaneously solve the p resistance perturbation equations and the q voltage perturbation equations to obtain a system of (p+q) linear equations.

[0241] As an example, by combining equations (1), (4), (5), and (6), we obtain a system of four linear equations in four variables.

[0242] As another example, by combining equations (2), (3), (7), and (8), we obtain a system of four linear equations in four variables.

[0243] In step S140, after the electronic device solves the p resistance perturbation equations and q voltage perturbation equations to obtain a system of (p+q) linear equations, it can also solve the system of (p+q) linear equations to obtain the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances.

[0244] In some implementations, solving a system of (p+q) linear equations yields the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances, specifically including:

[0245] The Gaussian elimination method is used to solve the (p+q)-element linear equation system to obtain the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances.

[0246] In this embodiment, the Gaussian elimination method is used to solve the (p+q)-element linear equation system, which can quickly and accurately obtain the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances.

[0247] It should be noted that the above process is based on three sets of maximum power point tracking units as an example. If the number of maximum power point tracking units increases, the process of determining q voltage perturbation equations can be repeated. Equations (1) to (3) above are called resistance perturbations, and equations (4) to (8) above can be called voltage perturbations. Assuming that the number of resistance perturbations is p, the number of voltage perturbations is q, and the number of maximum power point tracking units is n, then p + q = n + 1 is required to solve for the parallel sum of n positive and negative insulation impedances.

[0248] It should be added that if the insulation resistance measurement unit is like Figure 7 As shown, when the third switch K3 is on and the fourth switch K4 is off, you only need to change R2 in formula (7) and formula (8) to (R4+R6); when the third switch K3 is off and the fourth switch K4 is on, you only need to change R3 in formula (2) and formula (3) to (R5+R6).

[0249] It should be noted that different combinations of resistor network forms, photovoltaic string voltage perturbation methods, resistor perturbation times, and PV voltage perturbation times are all possible variations of this technical solution.

[0250] Understandably, the embodiments of this application can solve for the ground insulation impedance value of each maximum power point tracking unit, applicable to any Boost topology and at low cost. This allows for precise location of faulty photovoltaic module branches, improving the efficiency of subsequent manual maintenance. In contrast, related technologies require at least two sets of resistors and two sets of relays to solve for the ground insulation impedance value of each maximum power point tracking unit, while the embodiments of this application require only a single resistor, thus offering a cost advantage.

[0251] Example 2

[0252] As described in the background section, related technologies cannot determine the positive insulation impedance of a specific photovoltaic (PV) string, thus making it impossible to locate the insulation fault in that particular PV string. For example, when the impedance of a PV string decreases due to insulation degradation, the system can only determine that the overall insulation is abnormal, but cannot identify the fault location, which greatly complicates maintenance and troubleshooting. Therefore, developing a high-precision, multi-channel independent detection technology with strong anti-interference capabilities for insulation impedance has become an urgent need to improve the safety and intelligent operation and maintenance level of PV systems.

[0253] Based on this, this application also provides a photovoltaic system fault location method, which is applicable to the fault location process of a photovoltaic system. This photovoltaic system fault location method can be applied to a photovoltaic system and can be executed by a photovoltaic system fault location device, a controller in the photovoltaic system, and electronic equipment. The following description uses the execution of this photovoltaic system fault location method by electronic equipment as an example.

[0254] The photovoltaic system fault location method provided in this application embodiment may include steps S210 to S220.

[0255] S210. According to the insulation impedance detection method of Example 1, determine the parallel connection of the negative electrode insulation impedance of the photovoltaic system with the n positive electrode insulation impedances.

[0256] S220. Based on the parallel connection of the negative electrode insulation impedance and the insulation impedance of n positive electrodes, locate the faulty photovoltaic module branch in the photovoltaic system.

[0257] According to the photovoltaic system fault location method provided in the embodiments of this application, the parallel sum of negative electrode insulation impedance and the n positive electrode insulation impedances corresponding to n photovoltaic strings can be solved, thereby locating the faulty photovoltaic module branch and improving the efficiency of subsequent manual operation and maintenance.

[0258] Example 3

[0259] This application provides an insulation impedance detection device that can be applied to a photovoltaic system. The photovoltaic system includes n insulation impedance groups, each including a positive insulation impedance and a negative insulation impedance connected in series. The positive insulation impedance and the negative insulation impedance are grounded, and n is a positive integer.

[0260] n photovoltaic strings, with each photovoltaic string and its corresponding insulation impedance group connected in parallel between the positive bus and the negative bus;

[0261] There are n maximum power point tracking units, and each maximum power point tracking unit is connected to its corresponding photovoltaic string.

[0262] An insulation impedance measurement unit is connected to n maximum power point tracking units respectively;

[0263] The inverter is connected to the insulation resistance measurement unit.

[0264] like Figure 19 As shown, the device includes an acquisition module 310, a first determination module 320, a simultaneous equation module 330, and a solution module 340.

[0265] The acquisition module 310 is used to acquire p groups of resistance disturbance parameters and q groups of voltage disturbance parameters of the photovoltaic system. The resistance disturbance parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, as well as n first type of photovoltaic string voltages. The first type of photovoltaic string voltage corresponds one-to-one with the photovoltaic string. The voltage disturbance parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type of photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages. p and q are both positive integers, and p+q=n+1.

[0266] The first determining module 320, connected to the acquiring module 310, is used to determine, using Kirchhoff's laws, p resistance perturbation equations corresponding to p sets of resistance perturbation parameters, and q voltage perturbation equations corresponding to q sets of voltage perturbation parameters; both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances; the parallel sum of negative electrode insulation impedances is the sum of n parallel negative electrode insulation impedances;

[0267] The simultaneous equation module 330 is connected to the first determining module 320 to simultaneously solve p resistance perturbation equations and q voltage perturbation equations to obtain a system of (p+q) linear equations.

[0268] Solver module 340, connected to simultaneous equation module 330, is used to solve a system of (p+q) linear equations to obtain the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances.

[0269] In some implementations, the insulation impedance measuring unit includes a grounded first resistor;

[0270] p = 1, q = n = 3;

[0271] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0272] The first type of negative busbar voltage to ground includes the first negative busbar voltage to ground;

[0273] The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor;

[0274] The n type I photovoltaic string voltages include the first photovoltaic string voltage, the second photovoltaic string voltage, and the third photovoltaic string voltage;

[0275] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, the updated first photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltage, which includes both the second and third photovoltaic string voltages. The updated first photovoltaic string voltage is greater than both the second and third photovoltaic string voltages.

[0276] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages as the updated first and third photovoltaic string voltages. The updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage.

[0277] The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the fourth type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated third type of photovoltaic string voltage, and the (n-1) third type of photovoltaic string voltages included in the third set of voltage disturbance parameters, including the updated first type of photovoltaic string voltage and the updated second type of photovoltaic string voltage. The updated third type of photovoltaic string voltage is greater than the updated first type of photovoltaic string voltage and is also greater than the updated second type of photovoltaic string voltage.

[0278] In some implementations, the p resistance perturbation equations include a first resistance perturbation equation.

[0279] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0280] The first determining module 320 is specifically used for:

[0281] The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero;

[0282] The first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

[0283] In some implementations, the q voltage perturbation equations include a first voltage perturbation equation, a second voltage perturbation equation, and a third voltage perturbation equation;

[0284] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0285] The first determining module 320 is specifically used for:

[0286] The first voltage disturbance equation is determined to be that the sum of the sixth, seventh, eighth, ninth, and tenth currents is zero;

[0287] Among them, the sixth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic module to the insulation resistance of the first positive electrode; the seventh current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the second photovoltaic string to the insulation resistance of the second positive electrode; the eighth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the third photovoltaic string to the insulation resistance of the third positive electrode; the ninth current is the ratio of the voltage of the second negative busbar to ground to the parallel sum of the insulation resistance of the negative electrode; the tenth current is the ratio of the sum of the voltage of the second negative busbar to ground and the voltage of the updated first photovoltaic string to the first resistor.

[0288] The second voltage disturbance equation is determined to be that the sum of the eleventh, twelfth, thirteenth, fourteenth, and fifteenth currents is zero;

[0289] Among them, the eleventh current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the twelfth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the thirteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourteenth current is the ratio of the voltage of the third negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the fifteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the first resistance.

[0290] The third voltage disturbance equation is determined to be that the sum of the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth currents is zero;

[0291] Among them, the sixteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive terminal; the seventeenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive terminal; the eighteenth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the insulation impedance of the third positive terminal; the nineteenth current is the ratio of the voltage of the fourth negative busbar to ground and the parallel sum of the insulation impedance of the negative terminal; the twentieth current is the ratio of the sum of the voltage of the fourth negative busbar to ground and the voltage of the updated third photovoltaic string to the first resistance.

[0292] In some embodiments, the insulation impedance measuring unit includes a second resistor, a first switch, a second switch, and a third resistor connected in sequence, with the first switch and the second switch grounded between them;

[0293] p = q = 2, n = 3;

[0294] The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string;

[0295] The first type of negative busbar voltage to ground includes the fifth negative busbar voltage to ground and the sixth negative busbar voltage to ground; the fifth busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is on and the second switch is off; the sixth negative busbar voltage to ground is the voltage of the negative busbar to ground when the first switch is off and the second switch is on.

[0296] The first type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the fifth negative busbar is the second resistance;

[0297] The second type of resistance of the insulation impedance measurement unit corresponding to the voltage to ground of the sixth negative busbar is the third type of resistance;

[0298] The n type I photovoltaic string voltages include the fourth photovoltaic string voltage, the fifth photovoltaic string voltage, and the sixth photovoltaic string voltage;

[0299] The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the seventh negative bus voltage to ground; the first set of voltage disturbance parameters includes the second type of resistance, which is the second resistance; the first set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated fourth photovoltaic string voltage; the first set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the fifth photovoltaic string voltage and the sixth photovoltaic string voltage; the updated fourth photovoltaic string voltage is greater than the fifth photovoltaic string voltage and greater than the sixth photovoltaic string voltage.

[0300] The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the eighth negative bus voltage to ground; the second type of resistance, which is the second resistance; the second type of photovoltaic string voltage, which is the updated fifth photovoltaic string voltage; and the (n-1) third type of photovoltaic string voltage, which includes the updated fourth and sixth photovoltaic string voltages. The updated fifth photovoltaic string voltage is greater than the updated fourth photovoltaic string voltage and is also greater than the sixth photovoltaic string voltage.

[0301] In some implementations, the p resistance perturbation equations include a second resistance perturbation equation and a third resistance perturbation equation;

[0302] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0303] The first determining module 320 is specifically used for:

[0304] The second resistor perturbation equation is determined to be that the sum of the twenty-first, twenty-second, twenty-third, twenty-fourth, and twenty-fifth currents is zero;

[0305] Among them, the twenty-first current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-second current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-third current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-fourth current is the ratio of the voltage of the fifth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the twenty-fifth current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the second resistance.

[0306] The third resistor perturbation equation is determined to be that the sum of the twenty-sixth, twenty-seventh, twenty-eighth, twenty-ninth, and thirtieth currents is zero;

[0307] Among them, the twenty-sixth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive terminal; the twenty-seventh current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the twenty-eighth current is the ratio of the sum of the voltage of the sixth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the twenty-ninth current is the ratio of the voltage of the sixth negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; and the thirtieth current is the ratio of the voltage of the sixth negative busbar to ground to the third resistance.

[0308] In some implementations, the q voltage perturbation equations include a fourth voltage perturbation equation and a fifth voltage perturbation equation;

[0309] The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance;

[0310] The first determining module 320 is specifically used for:

[0311] The fourth voltage disturbance equation is determined to be that the sum of the thirty-first, thirty-second, thirty-third, thirty-fourth, and thirty-fifth currents is zero;

[0312] Among them, the thirty-first current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive terminal; the thirty-second current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive terminal; the thirty-third current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive terminal; the thirty-fourth current is the ratio of the voltage of the seventh negative busbar to ground to the parallel sum of the insulation impedance of the negative terminal; the thirty-fifth current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the second resistance.

[0313] The fifth voltage disturbance equation is determined to be that the sum of the thirty-sixth, thirty-seventh, thirty-eighth, thirty-ninth, and fortieth currents is zero;

[0314] Among them, the thirty-sixth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive pole; the thirty-seventh current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive pole; the thirty-eighth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive pole; the thirty-ninth current is the ratio of the voltage of the eighth negative busbar to ground to the parallel sum of the insulation impedance of the negative pole; and the fortieth current is the ratio of the sum of the voltage of the eighth negative busbar to ground and the voltage of the updated fifth photovoltaic string to the second resistance.

[0315] In some implementations, the solver module 340 is specifically used for:

[0316] The Gaussian elimination method is used to solve the (p+q)-element linear equation system to obtain the parallel sum of the negative electrode insulation impedance.

[0317] The insulation impedance detection device provided in this application embodiment can execute the insulation impedance detection method in embodiment 1, that is, it has the beneficial effects and implementation method of the insulation impedance detection method provided in embodiment 1 of this application. For details, please refer to the specific description of the insulation impedance detection method in embodiment 1 above. This embodiment will not repeat it here.

[0318] Example 4

[0319] This application also provides a photovoltaic system fault location system, including the insulation impedance detection device in embodiment 3, used to determine the parallel connection of the negative electrode insulation impedance of the photovoltaic system with n positive electrode insulation impedances;

[0320] The locating device, connected to the photovoltaic module fault determination device, is used to locate the faulty photovoltaic module branch in the photovoltaic system based on the parallel negative insulation impedance and the insulation impedance of n positive electrodes.

[0321] The photovoltaic system fault location system provided in this application has the beneficial effects and implementation methods of the photovoltaic system fault location method provided in Embodiment 2 of this application. For details, please refer to the specific description of the photovoltaic system fault location method in Embodiment 2 above. This embodiment will not repeat the description here.

[0322] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this application, and this application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this application, and these modifications and improvements are also considered to be within the scope of protection of this application.

Claims

1. An insulation impedance detection method characterized by comprising: Applied to a photovoltaic system, the photovoltaic system comprising: There are n insulation impedance groups, each group consisting of a positive insulation impedance and a negative insulation impedance connected in series, with the positive and negative insulation impedances grounded between them, where n is a positive integer. n photovoltaic strings, wherein the photovoltaic strings and their corresponding insulation impedance groups are connected in parallel between the positive bus and the negative bus; n maximum power point tracking units, wherein each maximum power point tracking unit is connected to its corresponding photovoltaic string; An insulation impedance measurement unit is connected to n maximum power point tracking units respectively; The inverter is connected to the insulation impedance measurement unit; The method includes: Obtain p sets of resistance perturbation parameters and q sets of voltage perturbation parameters of the photovoltaic system; the resistance perturbation parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, and n first type of photovoltaic string voltages; the first type of photovoltaic string voltage corresponds one-to-one with the photovoltaic string; the voltage perturbation parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type of photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages; p and q are both positive integers, and p+q=n+1; Using Kirchhoff's laws, p resistance perturbation equations corresponding to p sets of resistance perturbation parameters and q voltage perturbation equations corresponding to q sets of voltage perturbation parameters are determined. Both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances. The parallel sum of negative electrode insulation impedances is the sum of n parallel negative electrode insulation impedances. By simultaneously solving p resistance perturbation equations and q voltage perturbation equations, we obtain a system of (p+q) linear equations. Solve the system of (p+q) linear equations to obtain the parallel sum of the negative electrode insulation impedances and the n positive electrode insulation impedances.

2. The method of claim 1, wherein, The insulation impedance measuring unit includes a grounded first resistor; p = 1, q = n = 3; The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string; The first type of negative busbar to ground voltage includes the first negative busbar to ground voltage; The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor; The n type I photovoltaic string voltages include the first photovoltaic string voltage, the second photovoltaic string voltage, and the third photovoltaic string voltage; The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, and the updated first photovoltaic string voltage. The (n-1) third type of photovoltaic string voltages in the first set of voltage disturbance parameters include the second photovoltaic string voltage and the third photovoltaic string voltage. The updated first photovoltaic string voltage is greater than the second photovoltaic string voltage and greater than the third photovoltaic string voltage. The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages as the second set of voltage disturbance parameters, including the updated first photovoltaic string voltage and the third photovoltaic string voltage; the updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage. The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the fourth type of negative bus voltage to ground; the third set of voltage disturbance parameters includes the second type of resistance, which is the first resistance; the third set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated third photovoltaic string voltage; the third set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the updated first photovoltaic string voltage and the updated second photovoltaic string voltage; the updated third photovoltaic string voltage is greater than the updated first photovoltaic string voltage and is also greater than the updated second photovoltaic string voltage.

3. The method of claim 2, wherein, The p resistance perturbation equations include the first resistance perturbation equation. The n positive electrode insulation resistances include the first positive electrode insulation resistance, the second positive electrode insulation resistance, and the third positive electrode insulation resistance; The determination of the p resistance perturbation equations corresponding to the p groups of resistance perturbation parameters specifically includes: The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero; Wherein, the first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

4. The method of claim 2, wherein, The q voltage perturbation equations include the first voltage perturbation equation, the second voltage perturbation equation, and the third voltage perturbation equation; The n positive electrode insulation resistances include the first positive electrode insulation resistance, the second positive electrode insulation resistance, and the third positive electrode insulation resistance; The determination of the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters specifically includes: The first voltage disturbance equation is determined to be that the sum of the sixth, seventh, eighth, ninth, and tenth currents is zero; Wherein, the sixth current is the ratio of the sum of the second negative bus voltage to ground and the updated first photovoltaic module voltage to the first positive electrode insulation impedance; the seventh current is the ratio of the sum of the second negative bus voltage to ground and the second photovoltaic string voltage to the second positive electrode insulation impedance; the eighth current is the ratio of the sum of the second negative bus voltage to ground and the third photovoltaic string voltage to the third positive electrode insulation impedance; the ninth current is the ratio of the second negative bus voltage to ground and the parallel sum of the negative electrode insulation impedance; and the tenth current is the ratio of the sum of the second negative bus voltage to ground and the updated first photovoltaic string voltage to the first resistor. The second voltage disturbance equation is determined to be that the sum of the eleventh, twelfth, thirteenth, fourteenth, and fifteenth currents is zero; Wherein, the eleventh current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated first photovoltaic string to the insulation impedance of the first positive electrode; the twelfth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the insulation impedance of the second positive electrode; the thirteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive electrode; the fourteenth current is the ratio of the voltage of the third negative busbar to ground to the parallel sum of the insulation impedance of the negative electrode; and the fifteenth current is the ratio of the sum of the voltage of the third negative busbar to ground and the voltage of the updated second photovoltaic string to the first resistance. The third voltage disturbance equation is determined to be the sum of the sixteenth, seventeenth, eighteenth, nineteenth, and twentieth currents being zero; Wherein, the sixteenth current is the ratio of the sum of the fourth negative bus voltage to ground and the updated first photovoltaic string voltage to the first positive insulation impedance; the seventeenth current is the ratio of the sum of the fourth negative bus voltage to ground and the updated second photovoltaic string voltage to the second positive insulation impedance; the eighteenth current is the ratio of the sum of the fourth negative bus voltage to ground and the updated third photovoltaic string voltage to the third positive insulation impedance; the nineteenth current is the ratio of the fourth negative bus voltage to ground and the parallel sum of the negative insulation impedance; and the twentieth current is the ratio of the sum of the fourth negative bus voltage to ground and the updated third photovoltaic string voltage to the first resistance.

5. The method of claim 1, wherein, The insulation impedance measurement unit includes a second resistor, a first switch, a second switch, and a third resistor connected in sequence, with the first switch and the second switch grounded between them; p = q = 2, n = 3; The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string; The first type of negative busbar to ground voltage includes the fifth negative busbar to ground voltage and the sixth negative busbar to ground voltage; the fifth negative busbar to ground voltage is the voltage of the negative busbar to ground when the first switch is on and the second switch is off; the sixth negative busbar to ground voltage is the voltage of the negative busbar to ground when the first switch is off and the second switch is on. The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the fifth negative busbar is the second type of resistor; The second type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the sixth negative busbar is the third resistor; The n type I photovoltaic string voltages include the fourth photovoltaic string voltage, the fifth photovoltaic string voltage, and the sixth photovoltaic string voltage; The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the seventh negative bus voltage to ground; the first set of voltage disturbance parameters includes the second type of resistance, which is the second resistance; the first set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated fourth photovoltaic string voltage; the first set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the fifth photovoltaic string voltage and the sixth photovoltaic string voltage; the updated fourth photovoltaic string voltage is greater than the fifth photovoltaic string voltage and greater than the sixth photovoltaic string voltage. The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the eighth negative bus voltage to ground; the second type of resistance, which is the second resistance; the second type of photovoltaic string voltage, which is the updated fifth photovoltaic string voltage; and the (n-1) third type of photovoltaic string voltage, which includes the updated fourth photovoltaic string voltage and the sixth photovoltaic string voltage. The updated fifth photovoltaic string voltage is greater than the updated fourth photovoltaic string voltage and is also greater than the sixth photovoltaic string voltage.

6. The method of claim 5, wherein, The p resistance perturbation equations include the second resistance perturbation equation and the third resistance perturbation equation; The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance; The determination of the p resistance perturbation equations corresponding to the p groups of resistance perturbation parameters specifically includes: The second resistor perturbation equation is determined to be that the sum of the twenty-first, twenty-second, twenty-third, twenty-fourth, and twenty-fifth currents is zero; Wherein, the 21st current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive electrode; the 22nd current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive electrode; the 23rd current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive electrode; the 24th current is the ratio of the voltage of the fifth negative busbar to ground to the parallel sum of the insulation impedances of the negative electrode; the 25th current is the ratio of the sum of the voltage of the fifth negative busbar to ground and the voltage of the fourth photovoltaic string to the second resistance; The third resistor perturbation equation is determined to be that the sum of the twenty-sixth, twenty-seventh, twenty-eighth, twenty-ninth, and thirtieth currents is zero; Wherein, the 26th current is the ratio of the sum of the voltage of the sixth negative bus to ground and the voltage of the fourth photovoltaic string to the insulation impedance of the first positive electrode; the 27th current is the ratio of the sum of the voltage of the sixth negative bus to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive electrode; the 28th current is the ratio of the sum of the voltage of the sixth negative bus to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive electrode; the 29th current is the ratio of the voltage of the sixth negative bus to ground to the parallel sum of the insulation impedances of the negative electrode; and the 30th current is the ratio of the voltage of the sixth negative bus to ground to the third resistance.

7. The method according to claim 5, characterized in that, The q voltage perturbation equations include the fourth voltage perturbation equation and the fifth voltage perturbation equation; The n positive insulation resistances include the first positive insulation resistance, the second positive insulation resistance, and the third positive insulation resistance; The determination of the q voltage disturbance equations corresponding to the q sets of voltage disturbance parameters specifically includes: The fourth voltage disturbance equation is determined to be that the sum of the thirty-first, thirty-second, thirty-third, thirty-fourth, and thirty-fifth currents is zero; Wherein, the thirty-first current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the insulation impedance of the first positive electrode; the thirty-second current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the fifth photovoltaic string to the insulation impedance of the second positive electrode; the thirty-third current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the sixth photovoltaic string to the insulation impedance of the third positive electrode; the thirty-fourth current is the ratio of the voltage of the seventh negative busbar to ground to the parallel sum of the insulation impedances of the negative electrode; and the thirty-fifth current is the ratio of the sum of the voltage of the seventh negative busbar to ground and the voltage of the updated fourth photovoltaic string to the second resistance. The fifth voltage disturbance equation is determined to be that the sum of the thirty-sixth, thirty-seventh, thirty-eighth, thirty-ninth, and fortieth currents is zero; Wherein, the thirty-sixth current is the ratio of the sum of the voltage of the eighth negative bus to ground and the voltage of the updated fourth photovoltaic string to the first positive insulation impedance; the thirty-seventh current is the ratio of the sum of the voltage of the eighth negative bus to ground and the voltage of the updated second photovoltaic string to the second positive insulation impedance; the thirty-eighth current is the ratio of the sum of the voltage of the eighth negative bus to ground and the voltage of the sixth photovoltaic string to the third positive insulation impedance; the thirty-ninth current is the ratio of the voltage of the eighth negative bus to ground to the parallel sum of the negative insulation impedance; and the fortieth current is the ratio of the sum of the voltage of the eighth negative bus to ground and the voltage of the updated fifth photovoltaic string to the second resistance.

8. The method according to any one of claims 1 to 7, characterized in that, Solving the system of (p+q) linear equations yields the parallel sum of the negative electrode insulation impedances and n positive electrode insulation impedances, specifically including: The Gaussian elimination method is used to solve the (p+q)-element linear equation system to obtain the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances.

9. A method of fault locating in a photovoltaic system, characterized by, include: According to any one of claims 1 to 8, the insulation impedance detection method determines the parallel sum of the negative electrode insulation impedance and the n positive electrode insulation impedances of the photovoltaic system. Based on the parallel connection of the negative electrode insulation impedance and the n positive electrode insulation impedances, the faulty photovoltaic module branch in the photovoltaic system is located.

10. An insulation impedance detecting apparatus characterized by comprising: Applied to a photovoltaic system, the photovoltaic system comprising: There are n insulation impedance groups, each group consisting of a positive insulation impedance and a negative insulation impedance connected in series, with the positive and negative insulation impedances grounded between them, where n is a positive integer. n photovoltaic strings, wherein the photovoltaic strings and their corresponding insulation impedance groups are connected in parallel between the positive bus and the negative bus; n maximum power point tracking units, wherein each maximum power point tracking unit is connected to its corresponding photovoltaic string; An insulation impedance measurement unit is connected to n maximum power point tracking units respectively; The inverter is connected to the insulation impedance measurement unit; The device includes: The acquisition module is used to acquire p groups of resistance disturbance parameters and q groups of voltage disturbance parameters of the photovoltaic system; the resistance disturbance parameters include the first type of negative bus voltage to ground and the first type of resistance of the corresponding insulation impedance measurement unit, and n first type of photovoltaic string voltages; the first type of photovoltaic string voltage corresponds one-to-one with the photovoltaic string; the voltage disturbance parameters include the second type of negative bus voltage to ground and the second type of resistance of the corresponding insulation impedance measurement unit, the second type of photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages; p and q are both positive integers, and p+q=n+1; The first determining module, connected to the acquiring module, is used to determine, using Kirchhoff's laws, p resistance perturbation equations corresponding to p sets of resistance perturbation parameters, and q voltage perturbation equations corresponding to q sets of voltage perturbation parameters; both the resistance perturbation equations and the voltage perturbation equations include the parallel sum of negative electrode insulation impedances and n positive electrode insulation impedances; the parallel sum of negative electrode insulation impedances is the sum of n parallel negative electrode insulation impedances; The simultaneous equation module, connected to the first determining module, is used to simultaneously solve p resistance perturbation equations and q voltage perturbation equations to obtain a system of (p+q) linear equations. The solution module, connected to the simultaneous equation module, is used to solve the (p+q)-element linear system of equations to obtain the parallel sum of the negative electrode insulation impedances and n positive electrode insulation impedances.

11. The apparatus of claim 10, wherein, The insulation impedance measuring unit includes a grounded first resistor; p = 1, q = n = 3; The n photovoltaic strings include the first photovoltaic string, the second photovoltaic string, and the third photovoltaic string; The first type of negative busbar to ground voltage includes the first negative busbar to ground voltage; The first type of resistor in the insulation impedance measurement unit corresponding to the voltage to ground of the first negative busbar is the first resistor; The n type I photovoltaic string voltages include the first photovoltaic string voltage, the second photovoltaic string voltage, and the third photovoltaic string voltage; The first set of voltage disturbance parameters includes the second type of negative bus voltage to ground, the second type of resistance, and the updated first photovoltaic string voltage. The (n-1) third type of photovoltaic string voltages in the first set of voltage disturbance parameters include the second photovoltaic string voltage and the third photovoltaic string voltage. The updated first photovoltaic string voltage is greater than the second photovoltaic string voltage and greater than the third photovoltaic string voltage. The second set of voltage disturbance parameters includes the second type of negative bus voltage to ground as the third type of negative bus voltage to ground, the second type of resistance as the first type of resistance, the second type of photovoltaic string voltage as the updated second photovoltaic string voltage, and (n-1) third type of photovoltaic string voltages as the second set of voltage disturbance parameters, including the updated first photovoltaic string voltage and the third photovoltaic string voltage; the updated second photovoltaic string voltage is greater than the updated first photovoltaic string voltage and greater than the third photovoltaic string voltage. The third set of voltage disturbance parameters includes the second type of negative bus voltage to ground, which is the fourth type of negative bus voltage to ground; the third set of voltage disturbance parameters includes the second type of resistance, which is the first resistance; the third set of voltage disturbance parameters includes the second type of photovoltaic string voltage, which is the updated third photovoltaic string voltage; the third set of voltage disturbance parameters includes (n-1) third type photovoltaic string voltages, which include the updated first photovoltaic string voltage and the updated second photovoltaic string voltage; the updated third photovoltaic string voltage is greater than the updated first photovoltaic string voltage and is also greater than the updated second photovoltaic string voltage.

12. The apparatus of claim 11, wherein, The p resistance perturbation equations include the first resistance perturbation equation. The n positive electrode insulation resistances include the first positive electrode insulation resistance, the second positive electrode insulation resistance, and the third positive electrode insulation resistance; The first determining module is specifically used for: The first resistor disturbance equation is determined to be that the sum of the first current, the second current, the third current, the fourth current, and the fifth current is zero; Wherein, the first current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the insulation impedance of the first positive terminal; the second current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the second photovoltaic string to the insulation impedance of the second positive terminal; the third current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the third photovoltaic string to the insulation impedance of the third positive terminal; the fourth current is the ratio of the parallel sum of the voltage of the first negative busbar to ground and the insulation impedance of the negative terminal; and the fifth current is the ratio of the sum of the voltage of the first negative busbar to ground and the voltage of the first photovoltaic string to the first resistance.

13. A photovoltaic system fault location system characterized by, include: The insulation impedance detection device according to any one of claims 10 to 12 is used to determine the parallel insulation impedance of the negative electrode of a photovoltaic system and the insulation impedance of n positive electrodes. The positioning device, connected to the insulation impedance detection device, is used to locate the faulty photovoltaic module branch in the photovoltaic system based on the parallel and n positive insulation impedances of the negative electrode insulation impedance.

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