Method and system for calculating lightning overvoltage of wind power plant networking grounding system

Abstract

The invention provides a wind power plant networking grounding system lightning stroke overvoltage calculation method and system, and the method comprises the steps: calculating the impact grounding impedance and mutual impedance of a grounding device group based on a calculation model of the grounding device group; inputting parameters, and obtaining impact grounding impedance values of all networked fans on the wind power plant through a calculation model; inputting the impact grounding impedance value of the fan at each position of the wind power plant into electromagnetic transient simulation software as a parameter to form a wind power plant networking grounding system; building a multi-wave impedance model of a fan tower in electromagnetic transient simulation software, and forming a lightning stroke overvoltage calculation model of the wind power plant networking grounding system with the wind power plant networking grounding system; and injecting lightning impulse current into the lightning arrester end of the fan blade in the calculation model to obtain lightning stroke voltage values at different positions of the fan. The method is suitable for the complex working condition of actual lightning stroke of the wind power system of the wind network, the lightning stroke overvoltage value can be accurately calculated, and the safety and reliability of a wind power plant unit are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wind turbine lightning protection and grounding, and in particular relates to a method and system for calculating lightning overvoltage of a wind farm networking grounding system. Background Art

[0002] With the rapid development of wind power generation, the proportion of wind power generation in energy supply continues to grow, and people are increasingly concerned about the stability and reliability of wind turbine operation. In recent years, the capacity of wind turbines has continued to increase, the height of wind turbines has increased, and the height of the blade tip to the ground has increased significantly. The overall height of large-capacity megawatt-class wind turbines exceeds 100m, which increases the probability of wind turbines being struck by lightning. Lightning strikes are a natural disaster with extremely high energy. When lightning strikes wind turbines, it may cause electromagnetic, mechanical, thermal and other hazards to wind turbines. On the one hand, the strong transient lightning current is dispersed into the earth through the paths of blades, moving parts, towers and grounding structures, which will produce a transient electromagnetic field with drastic changes inside the wind turbine, thereby inducing overvoltage on various electronic and electrical equipment and cables. At the same time, the transient ground potential rise caused by it will lead to the safety threat of weak current system counterattack; on the other hand, due to the strong electromagnetic force and the local high heat generated by the leakage of metal conductors, structures such as blades will suffer significant mechanical effects and face the threat of structural damage. As the construction of new energy increases year by year, wind resource projects with good geographical locations are gradually decreasing. The geology of many wind turbines is mostly composed of rocks, with a small soil content and high soil resistivity. The grounding resistance is likely to exceed the safety limit, which makes it easier for wind turbines to be damaged by lightning, resulting in equipment damage and even casualties. Therefore, it is very necessary for wind farms to carry out lightning protection overvoltage calculations for wind turbines.

[0003] As an improvement, there are some calculation methods for lightning overvoltage of wind turbines. However, on the one hand, the current calculation of wind turbine grounding resistance often only considers the circular grounding body of the wind turbine, ignoring the dispersion effect of the wind turbine foundation as a natural grounding body. At this time, it is only suitable for the calculation of power frequency grounding resistance, and the calculation of lightning impulse impedance is inaccurate. On the other hand, since the wind turbine grounding system in high soil resistivity areas may use networking to reduce resistance, the wind turbine grounding device, box transformer grounding device and tower grounding device form a multi-conductor system. When the power frequency is short-circuited, the interconnected grounding devices can be considered to be equipotential bodies. However, the impact current is different from the power frequency dispersion. In this conductor system, the high-frequency electromagnetic coupling of the lightning impulse will cause the potential distribution of the grounding device to change. The power frequency equipotential body model is not suitable for the complex lightning conditions after multiple grounding devices are interconnected. Furthermore, at present, the calculation of lightning overvoltage of wind turbines can generally only be done for a single wind turbine. In areas with high soil resistivity, after the grounding systems of multiple wind turbines are connected to each other, it is impossible to calculate the lightning overvoltage value after the interconnection. The current calculation model or method of lightning overvoltage of a single wind turbine is not suitable for the complex working conditions of lightning after the grounding systems of multiple wind turbines are connected to each other. Therefore, in summary, the current calculation method of lightning overvoltage of wind turbine grounding has limited factors considered in the calculation, the calculation of lightning impulse impedance is not accurate enough, and it is not suitable for the complex working conditions of lightning after multiple grounding devices are connected to each other and the complex working conditions of lightning after the grounding systems of multiple wind turbines are connected to each other. Summary of the invention

[0004] The present invention provides a method and system for calculating lightning overvoltage of a wind farm networked grounding system, aiming to solve the problem that the current method for calculating lightning overvoltage of wind turbine grounding has limited factors considered in the calculation, the calculation of lightning impulse impedance is not accurate enough, and it is not suitable for complex lightning conditions after multiple grounding devices are interconnected and the complex lightning conditions after multiple wind turbine grounding systems are interconnected.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: The present invention provides a method for calculating lightning overvoltage of a wind farm network grounding system, comprising the following steps: S1. Based on the calculation model of the grounding device group, calculate the impact grounding impedance of the grounding device group and the mutual impedance between several grounding devices in the grounding device group under transient impact; S2, using the different soil resistivities of wind turbines at different locations measured on site at the wind farm and the spatial distances of grounding devices at various locations as calculation input parameters, and then calculating the impulse grounding impedance values ​​of all networked wind turbines in the wind farm through the calculation model; S3, the calculated impulse grounding impedance values ​​of wind turbines at various locations in the wind farm are used as parameters and input into electromagnetic transient simulation software, and connected through tower ground wires to form a wind farm network grounding system; S4. In the electromagnetic transient simulation software, a multi-wave impedance model of the wind turbine tower is constructed and combined with the wind farm network grounding system to form a lightning overvoltage calculation model for the wind farm network grounding system; S5. Inject lightning impulse current into the lightning arrester end of the wind turbine blade in the lightning overvoltage calculation model of the wind farm network grounding system to obtain the voltage value of lightning strikes at different positions of the wind turbine.

[0006] In some embodiments, in S1, a calculation model of the grounding device group is built in electromagnetic field grounding calculation software.

[0007] Further, in S1, the grounding device group includes a wind turbine grounding device, a box transformer grounding device and a tower grounding device.

[0008] Furthermore, S1 is specifically: S11. Establishing a three-dimensional model of the grounding device group in the electromagnetic field grounding calculation software; S12, injecting impulse transient current into each device model of the grounding device group respectively, and calculating the impulse grounding impedance value when each grounding device in the grounding device group is independently grounded; S13, arranging the spatial relationship of each grounding device in the grounding device group in the electromagnetic field grounding calculation software, and calculating the mutual impedance value between each grounding device.

[0009] Furthermore, in S11, a three-dimensional model of the grounding device group is established in the electromagnetic field grounding calculation software according to the structural dimensions of the grounding device group of the wind turbine in the wind farm and the diameter dimensions of the grounding conductor.

[0010] Furthermore, in S13, the mutual impedance value is calculated specifically as follows: an impact current is injected into any one of the grounding devices to obtain the ground potential rise of other grounding devices, and then the mutual impedance value between each grounding device in the grounding device group is calculated; the mutual impedance value between each grounding device in the grounding device group is the coefficient of the current-controlled voltage source in the electromagnetic field grounding calculation software.

[0011] In some embodiments, in S4, the wind turbine tower is divided into several sections along the vertical direction, the wave impedance value of each section is calculated, and the wave impedance values ​​of the several sections are used as parameters of the lightning overvoltage calculation model of the wind farm interconnected grounding system; specifically, the following formula (1) is used: (1); in, is the wave impedance, is the vertical cylinder height of the partition segment, is the average radius of the vertical cylinder of the separation segment.

[0012] The present invention also provides a calculation system for lightning overvoltage of a wind farm networked grounding system. The calculation system is built on electromagnetic field grounding calculation software. The calculation system includes a wind farm data acquisition module and a lightning overvoltage calculation module of a wind farm networked grounding system, wherein: The wind farm data acquisition module is used to collect data from the wind farm; The lightning overvoltage calculation module of the wind farm interconnected grounding system is used to calculate the voltage value of lightning strikes at various positions of the wind turbine after injecting lightning impulse current at the lightning receptor end of the wind turbine blade.

[0013] The present invention also provides a computer device, including a memory, a processor and a computer program stored and running on the memory, and when the processor executes the computer program, the steps of the method for calculating the lightning overvoltage of the grid-connected grounding system of a wind farm are implemented.

[0014] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the steps of the method for calculating the lightning overvoltage of the grid-connected grounding system of a wind farm are implemented.

[0015] Compared with the prior art, the method and system for calculating lightning overvoltage of a wind farm network grounding system of the present invention have the following beneficial effects: The present invention provides a method for calculating lightning overvoltage of a wind farm networked grounding system, comprising the following steps: S1, based on a calculation model of a grounding device group, calculating the impact grounding impedance of the grounding device group and the mutual impedance under transient impact between a plurality of grounding devices in the grounding device group; S2, using different soil resistivities of wind turbines at different positions measured on site in the wind farm and the spatial distances of grounding devices at various positions as calculation input parameters, and then calculating the impact grounding impedance values ​​of all networked wind turbines in the wind farm through the calculation model; S3, using the calculated impact grounding impedance values ​​of wind turbines at various positions in the wind farm as parameters, inputting them into electromagnetic transient simulation software, and connecting them through tower ground wires to form a wind farm networked grounding system; S4, in the electromagnetic transient simulation software, building a multi-wave impedance model of a wind turbine tower and combining it with the wind farm networked grounding system to form a lightning overvoltage calculation model for the wind farm networked grounding system; S5, injecting lightning impulse current into the lightning receptor end of a wind turbine blade in the lightning overvoltage calculation model for the wind farm networked grounding system, so as to obtain the voltage values ​​of the wind turbine at different positions after being struck by lightning. Based on the above, the present invention establishes a three-dimensional grounding device model for wind turbines, taking into account the scattered current factor of the wind turbine foundation as a natural grounding body, so that the calculated wind turbine impact grounding impedance value is more accurate; the present invention uses the calculated mutual impedance under transient impact between each grounding device as a model parameter of the wind farm networking grounding system, so that the calculation result of the wind turbine lightning overvoltage is more accurate. The present invention establishes a lightning overvoltage calculation model for the wind farm networking grounding system, which is suitable for the actual complex lightning strike conditions on site of the wind farm networking wind power system. The present invention improves the safety and reliability of wind farm units by reasonably designing the model and accurately simulating and calculating the predicted value of lightning overvoltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0017] Figure 1 A method for calculating lightning overvoltage in a wind farm network grounding system and a schematic diagram of a model of a wind turbine grounding device in the system according to the present invention; Figure 2 A calculation method for lightning overvoltage in a wind farm network grounding system and a schematic diagram of a wind turbine lightning overvoltage circuit in the system according to the present invention Figure 3 A method for calculating lightning overvoltage in a wind farm interconnected grounding system according to the present invention and a schematic diagram of a wind farm interconnected grounding system in the system; Figure 4 A method for calculating lightning overvoltage in a wind farm network grounding system according to the present invention and a schematic diagram of wind turbine tower segmentation in the system; Figure 5 A method for calculating lightning overvoltage in a wind farm network grounding system according to the present invention, a lightning overvoltage in the ground grid and a wind turbine ZRC-YJY23-0.6 / 1KV cable overvoltage in the system, and a schematic diagram of a lightning overvoltage calculation model for an H-line wind farm network grounding system; Figure 6 The present invention provides a method for calculating lightning overvoltage in a wind farm networking grounding system and an overvoltage on the high-voltage side of a box transformer and an overvoltage on a pole cable on a collector line in the system, and a schematic diagram of a lightning overvoltage calculation model for an H-line wind farm networking grounding system. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0021] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0022] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] How to provide a calculation model suitable for the actual complex working conditions of lightning strikes in wind power system sites, so that the calculated wind turbine impact grounding impedance value is more accurate, thereby making the overvoltage calculation result of wind turbine lightning strike more accurate.

[0025] like Figure 1 and Figure 2 As shown, the present invention provides a method for calculating the lightning overvoltage of a wind farm network grounding system, comprising the following steps: S1. Based on the calculation model of the grounding device group, calculate the impact grounding impedance of the grounding device group and the mutual impedance between several grounding devices in the grounding device group under transient impact; S2, using the different soil resistivities of wind turbines at different locations measured on site at the wind farm and the spatial distances of grounding devices at various locations as calculation input parameters, and then calculating the impulse grounding impedance values ​​of all networked wind turbines in the wind farm through the calculation model; S3, the calculated impulse grounding impedance values ​​of wind turbines at various locations in the wind farm are used as parameters and input into electromagnetic transient simulation software, and connected through tower ground wires to form a wind farm network grounding system; S4. In the electromagnetic transient simulation software, a multi-wave impedance model of the wind turbine tower is constructed and combined with the wind farm network grounding system to form a lightning overvoltage calculation model for the wind farm network grounding system; S5. Inject lightning impulse current into the lightning arrester end of the wind turbine blade in the lightning overvoltage calculation model of the wind farm network grounding system to obtain the voltage values ​​of lightning strikes at different positions of the wind turbine.

[0026] The present invention calculates the impulse grounding impedance of the grounding device group and the transient mutual impedance between each grounding device through modeling. The impact grounding impedance value of each wind turbine is obtained through the calculation model by using the soil resistivity and the spatial distance of the grounding device measured on site in the wind farm, thereby ensuring the accuracy and pertinence of the calculation result. The calculated impedance value is input into the electromagnetic transient simulation software, and the system model is formed through the tower ground wire connection, thereby simulating the electrical characteristics of the entire wind farm under lightning impulse. A multi-wave impedance model of the wind turbine tower is built, and combined with the wind farm network grounding system to form a complete lightning overvoltage calculation model, which more accurately simulates the propagation and reflection process of lightning in the tower. Lightning impulse current is injected into the lightning receptor end of the wind turbine blade of the model to simulate the actual lightning strike situation, and the lightning overvoltage values ​​at different positions of the wind turbine are calculated, thereby evaluating the effectiveness of the lightning protection design of the wind farm. The present invention improves the accuracy and reliability of the design through precise calculation and simulation, effectively predicts and evaluates lightning overvoltage, helps to take protective measures in time, ensures the safe and stable operation of the wind farm, and provides data support for the operation and maintenance management of the wind farm.

[0027] As an embodiment, the present invention builds a calculation model of a grounding device group in electromagnetic field grounding calculation software. The grounding device group of the present invention includes a wind turbine grounding device, a box transformer grounding device and a tower grounding device. The present invention ensures the integrity and representativeness of the calculation model. Using professional electromagnetic field grounding calculation software, the electrical characteristics of the grounding device group can be simulated more accurately, which is convenient for application in actual engineering.

[0028] Furthermore, the present invention also defines in detail the specific establishment process of the calculation model of the grounding device group and the calculation method of the mutual impedance value. By establishing a three-dimensional model, injecting impulse transient current, calculating independent grounding impedance and mutual impedance, etc., the calculation process is made clearer and more operable. Through scientific calculation methods and models, accurate and reliable grounding impedance and mutual impedance values ​​are obtained. By calculating the wave impedance value of each section and using it as a parameter of the calculation model, the propagation process of lightning in the tower can be more accurately simulated.

[0029] The present invention also provides a calculation system for lightning overvoltage of a wind farm networked grounding system. The calculation system is built on electromagnetic field grounding calculation software. The calculation system includes a wind farm data acquisition module and a wind farm networked grounding system lightning overvoltage calculation module, wherein: the wind farm data acquisition module is used to collect data of the wind farm; the wind farm networked grounding system lightning overvoltage calculation module is used to calculate the voltage value of lightning strikes at various positions of the wind turbine after injecting lightning impulse current at the lightning receptor end of the wind turbine blade. The system can complete the calculation process by inputting necessary parameters and instructions through the input end. The operation is simple and fast. The calculation system is suitable for wind farms of various sizes and has high practicality.

[0030] In the method and system for calculating lightning overvoltage in the wind farm network grounding system of the present invention: First, the calculation model of the wind turbine grounding device, box transformer grounding device and tower grounding device is built through electromagnetic field grounding calculation software (such as CDEGS), and the impact grounding impedance of each grounding device and the mutual impedance under transient impact between them are calculated. The specific steps are as follows: 1) Establish a three-dimensional model of the grounding device in the software through the grounding device of the wind turbine in the wind farm, the grounding device of the box transformer, and the structural dimensions of the grounding device of the collector line tower and the diameter of the grounding conductor; 2) Inject impulse transient current into the grounding device of the wind turbine, the box transformer grounding device, and the collector line tower grounding device model respectively, and calculate the impulse grounding impedance value when each grounding device is independently grounded, that is, the grounding impulse impedance R of the wind turbine a , Box-type transformer grounding impulse impedance R b , and the impulse impedance R of the collector line tower grounding device c ; 3) Arrange the models of the wind turbine grounding device, the box transformer grounding device, and the collector line tower grounding device in the grounding calculation software according to the actual spatial position relationship of the three at the wind power site, and then inject impulse current into each grounding device respectively. The ground potential rise of the other two grounding devices can be obtained through the impulse current of one of them, that is, the wind turbine injection current I a When the bottom potential rises U at the box-type transformer and the tower ab , U ac , inject current I at the transformer b When the ground potential rises to U at the wind turbine and tower ba , U bc , inject current I at the tower c When the ground potential rises to U at the fan and transformer ca , U cb , thus finding the mutual impedance value between the three, that is, R ab =U ab / I a、 R ac =U ac / I a , R ba =U ba / I b、 R bc =U bc / I b、 R ca =U ca / I c、 R cb =U cb / I c The mutual impedance in the present invention is finally reflected in the model as the coefficient of the current-controlled voltage source.

[0031] The different soil resistivities of wind turbines at different locations measured on site at the wind farm and the spatial distances of grounding devices at various locations are used as calculation input parameters, and then the impact grounding impedance values ​​of all networked wind turbines in the wind farm are calculated through the calculation model.

[0032] The calculated impact grounding impedance values ​​of wind turbines at various locations in the wind farm are used as parameters and input into the electromagnetic transient simulation software, and are connected through the tower ground wire to form a wind farm network grounding system.

[0033] like Figure 4 As shown, in the electromagnetic transient simulation software, a complete lightning overvoltage calculation model for the wind farm network grounding system is formed by building a multi-wave impedance model of the wind turbine tower and combining it with the wind farm network grounding system obtained above. Among them: 1) The wind turbine tower is regarded as a vertical conductor and divided into several sections. A wave impedance can be calculated for each section. The smaller the length of the divided section, the more accurate the result. The specific calculation is performed according to the following formula (1): (1); among which, is the wave impedance, is the vertical cylinder height of the partition segment, is the average radius of the vertical cylinder of the separation segment.

[0034] 2) Calculate the wave impedance Z of the fan blade using formula (1): a1 , Z a2 , Z a3 ,Then the wind turbine tower is divided into four sections according to its length, and the wave impedance of each section is calculated. Then it is connected with the lightning overvoltage calculation model of the wind farm network grounding system, such as Figure 2 shown.

[0035] Step 5: Inject lightning impulse current into the lightning receptor end of the wind turbine blade in the lightning overvoltage calculation model of the wind farm network grounding system to obtain the lightning overvoltage value at each position of the wind turbine.

[0036] The calculation method and system of lightning overvoltage of the wind farm network grounding system of the present invention are further described in detail below through specific embodiments.

[0037] like Figure 3-Figure 6 As shown in the figure, after a certain wind farm was connected to the grid, 15 wind turbines along the collector line H were selected for lightning overvoltage calculation. First, the grounding resistance values ​​of the wind turbines under different working conditions were calculated by using the soil resistivity of each wind turbine and the calculation model of the method of the present invention. As shown in Table 1 below, it can be seen from Table 1 that after the interconnection, the impact grounding resistance value of the wind turbine is significantly reduced due to the shunting of the lightning current.

[0038] Table 1 Fan impact grounding impedance

[0039] The calculation shows that the No. 1 wind turbine has its own grounding resistance of 13.32Ω, the box transformer grounding resistance of 20.47Ω, the tower grounding resistance of 14.49Ω, and the mutual impedance coefficient R ab =7.16 、 R ac =6.45, R ba =7.18 、 R bc =7.33 、 R ca =6.46 、 R cb =7.2, and put the parameter input as the grounding system parameter into the model to carry out calculation and obtain the wind turbine lightning overvoltage value as shown in the figure.

[0040] The wind turbine tower is 77.5m high, as shown in the figure. The blade length is 40m, and the wind turbine blade lightning receptor is a copper conductor with a radius of 4mm. The assumption is that the blade is at the highest point when lightning strikes the wind turbine blade. The multi-wave impedance value of the tower can be obtained based on the tower segment size and formula, and the calculation results are shown in Table 2.

[0041] Table 2 Calculation results of wind turbine tower using multi-wave impedance

[0042] In summary, the present invention accurately calculates and predicts the overvoltage of a wind farm under lightning strikes. The system integrates data acquisition and calculation modules to achieve automated, high-precision lightning overvoltage assessment. The present invention not only improves the accuracy of lightning protection design for wind farms, but also provides a strong guarantee for their safe and stable operation. It can more effectively evaluate and optimize lightning protection measures, thereby improving the safety of wind farms.

[0043] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the specification and described above. However, any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, makes slight changes, modifications and equivalent changes made by using the technical content disclosed above, which still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for calculating lightning overvoltage in a wind farm interconnected grounding system, characterized in that: The steps include: S1. Based on the calculation model of the grounding device group, calculate the impact grounding impedance of the grounding device group and the mutual impedance between several grounding devices in the grounding device group under transient impact; S2, using the different soil resistivities of wind turbines at different locations measured on site at the wind farm and the spatial distances of grounding devices at various locations as calculation input parameters, and then calculating the impulse grounding impedance values ​​of all networked wind turbines in the wind farm through the calculation model; S3, the calculated impulse grounding impedance values ​​of wind turbines at various locations in the wind farm are used as parameters and input into electromagnetic transient simulation software, and connected through tower ground wires to form a wind farm network grounding system; S4. In the electromagnetic transient simulation software, a multi-wave impedance model of the wind turbine tower is constructed and combined with the wind farm network grounding system to form a lightning overvoltage calculation model for the wind farm network grounding system; S5. Inject lightning impulse current into the lightning arrester end of the wind turbine blade in the lightning overvoltage calculation model of the wind farm network grounding system to obtain the voltage value of lightning strikes at different positions of the wind turbine.

2. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 1 is characterized in that: In S1, a calculation model of the grounding device group is built in the electromagnetic field grounding calculation software.

3. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 2 is characterized in that: In S1, the grounding device group includes a wind turbine grounding device, a box transformer grounding device and a tower grounding device.

4. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 2, characterized in that: The S1 is specifically: S11. Establishing a three-dimensional model of the grounding device group in the electromagnetic field grounding calculation software; S12, injecting impulse transient current into each device model of the grounding device group respectively, and calculating the impulse grounding impedance value when each grounding device in the grounding device group is independently grounded; S13, arranging the spatial relationship of each grounding device in the grounding device group in the electromagnetic field grounding calculation software, and calculating the mutual impedance value between each grounding device.

5. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 4 is characterized in that: In the S11, a three-dimensional model of the grounding device group is established in the electromagnetic field grounding calculation software according to the structural dimensions of the grounding device group of the wind turbine in the wind farm and the diameter dimensions of the grounding conductor.

6. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 4, characterized in that: In S13, the mutual impedance value is calculated specifically as follows: an impact current is injected into any one of the grounding devices to obtain the ground potential rise of other grounding devices, and then the mutual impedance value between each grounding device in the grounding device group is calculated; the mutual impedance value between each grounding device in the grounding device group is the coefficient of the current-controlled voltage source in the electromagnetic field grounding calculation software.

7. The method for calculating lightning overvoltage of a wind farm interconnected grounding system according to claim 1, characterized in that: In the above S4, the wind turbine tower is divided into several sections along the vertical direction, the wave impedance value of each section is calculated, and the wave impedance values ​​of the several sections are used as parameters of the lightning overvoltage calculation model of the wind farm interconnected grounding system; specifically, the following formula (1) is used: （1）； in, is the wave impedance, is the vertical cylinder height of the partition segment, is the average radius of the vertical cylinder of the separation segment.

8. A computing system based on the method for calculating the lightning overvoltage of the wind farm network grounding system according to any one of claims 1 to 7, characterized in that: The computing system is built on the electromagnetic field grounding computing software, and the computing system includes a wind farm data acquisition module and a wind farm network grounding system lightning overvoltage computing module, wherein: The wind farm data acquisition module is used to collect data of the wind farm; The lightning overvoltage calculation module of the wind farm network grounding system is used to calculate the voltage value of lightning strikes at various positions of the wind turbine after injecting lightning impulse current into the lightning receptor end of the wind turbine blade.

9. A computer device comprising a memory, a processor and a computer program stored and executed on the memory, characterized in that: When the processor executes the computer program, the steps of the method for calculating the lightning overvoltage of the wind farm network grounding system as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for calculating the lightning overvoltage of a wind farm interconnected grounding system as claimed in any one of claims 1 to 7 are implemented.

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