Method for simulating magnetizing inrush current of high-impedance transformer based on hysteresis characteristic of iron core

Abstract

The invention relates to the technical field of transformers, in particular to a high-impedance transformer magnetizing inrush current simulation method based on the hysteresis characteristic of an iron core, and the method comprises the steps: building a finite element model of a high-impedance transformer in simulation software; establishing a hysteresis model based on the hysteresis characteristics of the iron core to describe the hysteresis characteristics of the iron core; parameters corresponding to the actual parameters in the simulation model are set according to the actual parameters of the high-impedance transformer; hysteresis characteristic parameters of the iron core are set; calculating magnetic flux density and magnetization intensity in the iron core based on the established hysteresis model and a solving algorithm; the hysteresis characteristic of the iron core is considered, the change of the magnetic flux density along with time is calculated, and the state variable in the hysteresis model is updated; according to the Faraday's law of electromagnetic induction and the Ohm's law, induced electromotive force and current in the transformer winding are calculated; comparing the calculated current with a rated current to determine whether excitation inrush current exists or not; parameters for analyzing the magnetizing inrush current comprise the waveform, the size and the attenuation speed.

Description

Technical Field

[0001] The invention relates to the technical field of transformers, in particular to a method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics. Background Art

[0002] my country is a manufacturing country. With the rapid development of economy and society, the demand for electricity and the scale of power grid are constantly expanding. In order to solve the problem of uneven geographical distribution of power resources and load centers in my country, my country's power grid has gradually formed an AC / DC cross-regional interconnection pattern with large transmission capacity and long transmission distance. In addition, in order to alleviate the problems of traditional energy depletion and ecological environment deterioration, my country's power grid has also connected a large number of renewable clean energy in various forms. Renewable energy often has the characteristics of volatility, intermittency, low system inertia and low anti-interference ability. A small accident in the power grid may cause a chain failure, evolve into a local or even larger-scale blackout accident, and endanger the safe operation of the entire interconnected power grid. As the first line of defense for the safety protection of the power system, the reliability of relay protection is crucial to curb the development and expansion of accidents and maintain the stable operation of the system.

[0003] With the development of economy and society, the main grids of large power grids and urban power grids with concentrated loads have generally seen the problem of decreasing system impedance and serious over-limit of short-circuit current. The cost of circuit breakers will rise sharply with the increase of interruption capacity demand. In order to limit the short-circuit current on the low-voltage side of the transformer, the traditional solution is to connect a reactor in series on the low-voltage side of the transformer, but this adds a primary device. High-impedance transformers can increase short-circuit impedance to reduce short-circuit current without adding primary equipment, and have been increasingly widely used. For 220kV / 240MVA three-winding transformers, the high and medium impedance of the high-impedance transformer connected to the distribution network on the low-voltage side is the standard impedance (the same as that of ordinary transformers), and the high and low impedance and medium and low impedance are high impedance. The short-circuit impedance of ordinary transformers (referred to as "ordinary transformers") is generally about "high and medium 14%, high and low 23%, medium and low 9%, and the short-circuit impedance of high-impedance transformers is generally about "high and medium 14%, high and low 36%, medium and low 22%".

[0004] However, in recent years, the power grid has frequently seen the situation where the surge current when high-impedance transformers are put into operation causes the bus tie switch and even the upper-level line zero-sequence overcurrent protection to malfunction. The reliability of power supply of the power grid is seriously affected, and the safe operation of the system faces severe challenges. However, with the continuous increase in the market share of high-impedance transformers, due to the problem of large no-load closing excitation surge current, the zero-sequence overcurrent protection malfunction of the bus (section) switch caused by no-load often occurs. Especially in some developed areas, there are great difficulties in the coordination between high-impedance transformers and the backup protection setting value, which seriously threatens the stable operation of the power grid.

[0005] Therefore, how to systematically study and simulate the excitation inrush current phenomenon of high-impedance transformers, and select appropriate methods to suppress the excitation inrush current phenomenon based on the simulation results, is of great practical significance to the safe and stable operation of the power grid. Summary of the invention

[0006] The present invention is proposed in view of the above-mentioned background problems.

[0007] Therefore, the problem to be solved by the present invention is how to establish a model to express the hysteresis characteristics and the characteristics of the magnetizing inrush current in the high impedance transformer.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics, comprising the following specific steps:

[0010] S1. Establish a finite element model of a high impedance transformer in the simulation software;

[0011] S2. Establishing a hysteresis model based on the iron core to describe the hysteresis characteristics of the iron core;

[0012] S3, setting corresponding parameters in the simulation model according to the actual parameters of the high impedance transformer;

[0013] S4, setting the hysteresis characteristic parameters of the core;

[0014] S5. Calculate the magnetic flux density and magnetization intensity in the core based on the hysteresis model and solution algorithm;

[0015] S6. Considering the hysteresis characteristics of the iron core, calculate the change of magnetic flux density over time, and update the state variables in the hysteresis model;

[0016] S7. Calculate the induced electromotive force and current in the transformer winding according to Faraday's law of electromagnetic induction and Ohm's law;

[0017] S8, comparing the calculated current with the rated current to determine whether there is an excitation inrush current;

[0018] S9. Analyze the various parameters of the excitation inrush current, including waveform, size, and decay speed;

[0019] S10. Compare the simulation results with the actual high-impedance transformer test data to verify the accuracy of the simulation model and continue to optimize the model.

[0020] In step S1, a finite element model of a high impedance transformer is established using MATLAB / Simulink software;

[0021] The established high impedance transformer finite element model includes a variety of core structures, specifically:

[0022] a) Winding high impedance transformer;

[0023] b) Medium voltage split high impedance transformer;

[0024] c) Low voltage series reactance high impedance transformer;

[0025] d) High voltage built-in high impedance transformer.

[0026] In step S2, a hysteresis model is established according to each different core structure;

[0027] Among them: a) The hysteresis model of the winding high impedance transformer is:

[0028] B(H)=μ0(H+M(H))

[0029] in:

[0030]

[0031] Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field intensity; H0 is the material characteristic constant;

[0032] b) The hysteresis model of the medium voltage split high impedance transformer is:

[0033]

[0034] Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ r is the relative magnetic permeability; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field strength;

[0035] c) The hysteresis model of low voltage series reactance high impedance transformer is:

[0036]

[0037] Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H0 is the material characteristic constant;

[0038] d) The hysteresis model of the high-voltage built-in high-impedance transformer is:

[0039]

[0040] Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H cThe coercive force is the magnetic field strength required for the material to return to a non-magnetic state after the external magnetic field is removed.

[0041] The parameters input in step S3 include transformer geometric electrical parameters, core material properties, winding parameters, and operating frequency and voltage;

[0042] The geometric electrical parameters of the transformer include the structure of the core, the structure of the winding, and the parameters of size and weight that affect the heat dissipation performance; they also include rated current, nominal frequency, voltage ratio, current ratio, efficiency and loss, insulation performance, and temperature rise performance;

[0043] Core material properties include: density, magnetic permeability, and saturation magnetic induction intensity;

[0044] Winding parameters include: number of turns, coil material, winding resistance;

[0045] And set boundary conditions according to the actual nameplate parameters of the transformer; specifically including magnetic field boundary, current boundary and voltage boundary.

[0046] In step S7, the induced electromotive force is calculated according to Faraday's law of electromagnetic induction:

[0047]

[0048] Where E is the induced electromotive force, Φ is the magnetic flux;

[0049] Calculate the current in the winding using Ohm's law:

[0050]

[0051] Where R is the total resistance of the winding.

[0052] In step S8, the rated current value of the transformer is obtained; the calculated current is compared with the rated current to determine whether there is an excitation inrush current; if the calculated current exceeds the rated current, the amplitude of the inrush current is recorded and analyzed.

[0053] In step S10, the simulation result is compared with the test data of the actual high impedance transformer to confirm the accuracy of the model; according to the comparison result, the adjustment coefficient in the model is adjusted to improve the accuracy of the model.

[0054] A second aspect of the present invention provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the high-impedance transformer excitation inrush current simulation method based on the core hysteresis characteristics are implemented.

[0055] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-mentioned method for simulating magnetizing inrush current of a high-impedance transformer based on core hysteresis characteristics.

[0056] The beneficial effects of the present invention are:

[0057] The present invention establishes a plurality of different types of high impedance transformer models and reserves a plurality of input parameters to simulate the actual transformer structure, and then constructs a hysteresis model for each high impedance transformer model based on this to describe the hysteresis characteristics of the iron core; then, various parameters of the actual transformer are input into the established hysteresis model, and the magnetic induction intensity saturation value B is determined according to experimental data. s , coercive force H c The value is substituted into the image of the output hysteresis loop in the model and compared with the hysteresis loop obtained in the actual experiment to verify the model; after verification, the induced electromotive force and current in the transformer winding are calculated according to Faraday's law of electromagnetic induction and Ohm's law to determine whether there is an excitation inrush current, and the various parameters of the excitation inrush current are analyzed, including: waveform, size, and decay rate; the waveform of the excitation inrush current is analyzed using time domain data, and the time-current diagram is drawn; the maximum value and decay rate of the excitation inrush current are calculated, and its impact on the performance of the transformer is analyzed; the factors affecting the excitation inrush current, including core material, winding design, and access power characteristics, are evaluated; and the final simulation results are obtained. The excitation inrush current phenomenon during the operation of the transformer is analyzed by model simulation to explore its relationship with the transformer type structure and temperature and other related parameters, which is conducive to targeted suppression of the excitation inrush current and improve the safety of power grid operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 A model diagram of a high impedance transformer for simulation of magnetizing inrush current of a high impedance transformer based on the hysteresis characteristics of the iron core.

[0060] Figure 2 Flowchart of the multi-dimensional positioning and safety detection method based on the helmet for the simulation of the magnetizing inrush current of the high impedance transformer based on the hysteresis characteristics of the iron core. DETAILED DESCRIPTION

[0061] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0062] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0063] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0064] Example 1

[0065] The present invention provides a method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics, comprising the following specific steps:

[0066] S1, establishing a finite element model of a high impedance transformer in a simulation software; In step S1, a finite element model of a high impedance transformer is established using MATLAB / Simulink software;

[0067] The established high impedance transformer finite element model includes a variety of core structures, specifically:

[0068] a) Winding high impedance transformer;

[0069] b) Medium voltage split high impedance transformer;

[0070] c) Low voltage series reactance high impedance transformer;

[0071] d) High voltage built-in high impedance transformer.

[0072] In this embodiment, if Figure 1 As shown in the figure, models of various types of high impedance transformers are established, and the simulation methods of magnetizing inrush current for high impedance transformers are introduced one by one as examples;

[0073] Among them, Figure 1 As shown in a, the winding type high impedance transformer includes an iron core, a low voltage winding, a medium voltage winding, a high voltage winding and a voltage regulating winding. The impedance is increased by increasing the number of winding turns on the existing conventional ordinary transformer structure; different numbers of turns can be added to the low voltage winding, the medium voltage winding, the high voltage winding and the voltage regulating winding as needed to meet actual needs.

[0074] like Figure 1As shown in b, it is a medium voltage split high impedance transformer, which includes an iron core, a low voltage winding, a voltage regulating winding, a medium voltage split winding, a high voltage winding and a medium voltage split winding; by splitting the medium voltage side winding into two parts, the impedance of the transformer is increased by increasing the leakage reactance of the winding.

[0075] like Figure 1 As shown in c, it is a low-voltage series reactor transformer, which includes an iron core, a low-voltage winding, a medium-voltage winding, a high-voltage winding, a voltage regulating winding and a series reactor; by connecting a series reactor through a lead at the end of the low-voltage winding of the transformer, the leakage reactance of the winding is also increased.

[0076] like Figure 1 d shows a high-voltage built-in transformer, which includes an iron core, a high-voltage winding, a medium-voltage winding, a voltage regulating winding and a low-voltage winding; a reactor is set inside the transformer oil tank, and the impedance is increased by increasing the reactance at the transformer inlet; the key to this method is to effectively shield the leakage magnetic field generated by the reactor to reduce the stray loss generated in the structural parts and prevent local overheating. In this embodiment, a simulation model is constructed by simulating the above four high-impedance transformers.

[0077] S2. Establishing a hysteresis model based on the iron core to describe the hysteresis characteristics of the iron core;

[0078] In step S2, a hysteresis model is established according to each different core structure;

[0079] Among them: a) The hysteresis model of the winding high impedance transformer is:

[0080] B(H)=μ0(H+M(H))

[0081] in:

[0082]

[0083] Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field intensity; H0 is the material characteristic constant;

[0084] b) The hysteresis model of the medium voltage split high impedance transformer is:

[0085]

[0086] Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ r is the relative magnetic permeability; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field strength;

[0087] c) The hysteresis model of low voltage series reactance high impedance transformer is:

[0088]

[0089] Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H0 is the material characteristic constant;

[0090] d) The hysteresis model of the high-voltage built-in high-impedance transformer is:

[0091]

[0092] Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H c is the coercive force, which represents the magnetic field strength required for the material to return to a non-magnetic state after the external magnetic field is removed. In the above formula, H0 is a material characteristic constant, which is used to adjust the relationship between magnetic induction intensity and magnetic field intensity in the equation; generally, the material characteristic constant H0 is not the same for different types of materials such as silicon steel and ferrite. The value of H0 can be directly obtained by querying the database or textbook to select data matching the transformer material in the embodiment. Calibration can also be performed by experimental measurement; for example, the relationship between the magnetic induction intensity B and the magnetic field intensity H under different magnetic field intensities can be recorded by measuring the hysteresis loop of the material, and a control experiment can be performed to simultaneously collect the relationship between the magnetic induction intensity B and the magnetic field intensity H under different temperatures, different frequencies and different material uniformities; a specific magnetic field intensity value H1 is extracted from the experimental data as a preliminary estimate of the H0 value; the experimental data is fitted using nonlinear regression to calculate the magnetic field intensity value H2 that best fits the experimental data. An adjustment model is constructed with K as the adjustment coefficient, as follows:

[0093] B′(H)=KB(H)

[0094] Among them, B′(H) is the adjusted hysteresis model, K is the adjustment coefficient;

[0095]

[0096]

[0097] k1≤K≤k2;

[0098] For instances where the material characteristic constant H0 cannot be obtained by querying a database or textbook, verification is performed only by experiment;

[0099]

[0100] k1≤K≤k2;

[0101] In this embodiment, hysteresis models are established respectively according to four different types of high impedance transformer models, and simulations are carried out specifically to analyze the excitation inrush currents generated by the different types of high impedance transformers.

[0102] S3, setting corresponding parameters in the simulation model according to the actual parameters of the high impedance transformer;

[0103] The parameters input in step S3 include transformer geometric electrical parameters, core material properties, winding parameters, and operating frequency and voltage;

[0104] The geometric electrical parameters of the transformer include the structure of the core, the structure of the winding, and the parameters of size and weight that affect the heat dissipation performance; they also include rated current, nominal frequency, voltage ratio, current ratio, efficiency and loss, insulation performance, and temperature rise performance;

[0105] The core material properties include: density, magnetic permeability, saturation magnetic induction intensity, and various parameters of the core under different temperatures and magnetic field rings;

[0106] Winding parameters include: number of turns, coil material, winding resistance;

[0107] And set boundary conditions according to the actual nameplate parameters of the transformer; specifically including magnetic field boundary, current boundary and voltage boundary; the above parameters can be obtained through the parameters on the transformer nameplate or by visiting the transformer manufacturer's website or related database query, or can be determined through experiments.

[0108] S4, setting the hysteresis characteristic parameters of the core;

[0109] Enter the magnetic induction intensity saturation value B in the constructed simulation model s , coercive force H c , obtain the image of the hysteresis loop; compare the established model with the shape or characteristics of the actual hysteresis loop of the high impedance transformer to verify the performance of the model; by adjusting the adjustment coefficient K and the induction intensity saturation value B s , coercive force H c , until the curve fitting degree is greater than or equal to 0.9; the subsequent steps are carried out based on the parameters at this time.

[0110] S5. Calculate the magnetic flux density and magnetization intensity in the iron core based on the established hysteresis model and solution algorithm;

[0111] Use the software's solver settings, select an appropriate solution method (such as steady-state or transient solution) to obtain the calculation results, run the simulation to obtain the distribution of the magnetic flux density and magnetization intensity in the core; and perform data processing as needed and use visualization tools to further analyze the various parameters.

[0112] S6. Considering the hysteresis characteristics of the iron core, calculate the change of magnetic flux density over time, and update the state variables in the hysteresis model;

[0113] Simulation is performed in the time domain, taking into account the effect of hysteresis characteristics on magnetic flux density. The state variables in the hysteresis model are updated according to the simulation results to ensure that the model reflects the changes in the magnetic field in real time. The magnetic flux density and magnetic field intensity at different time steps are recorded to form a data set for subsequent analysis.

[0114] S7. Calculate the induced electromotive force and current in the transformer winding according to Faraday's law of electromagnetic induction and Ohm's law;

[0115] In step S7, the induced electromotive force is calculated according to Faraday's law of electromagnetic induction:

[0116]

[0117] Where E is the induced electromotive force, Φ is the magnetic flux; Φ=B*A, B is the magnetic induction intensity, and A is the magnetic field area.

[0118] Calculate the current in the winding using Ohm's law:

[0119]

[0120] Where R is the total resistance of the winding.

[0121] S8, comparing the calculated current with the rated current to determine whether there is an excitation inrush current;

[0122] In step S8, the rated current value of the transformer is obtained; the calculated current is compared with the rated current to determine whether there is an excitation inrush current; if the calculated current exceeds the rated current, the amplitude of the inrush current is recorded and analyzed.

[0123] S9. Analyze various parameters of the excitation inrush current including: waveform, size, and decay speed;

[0124] Use time domain data to analyze the waveform of the excitation inrush current and draw a time-current diagram; calculate the maximum value and decay rate of the excitation inrush current and analyze its impact on transformer performance; evaluate factors affecting the excitation inrush current, including core material, winding design, and access power characteristics.

[0125] From the above examples, it can be seen that this scheme first establishes four high-impedance transformer models with different core structures in the simulation software; based on this, a hysteresis model is constructed for each high-impedance transformer model to describe the hysteresis characteristics of the core; then the various parameters of the actual transformer are input into the established hysteresis model, and the magnetic induction intensity saturation value B is determined according to the experimental data. s , coercive force H cThe value is substituted into the model to output the image of the hysteresis loop and compared with the hysteresis loop obtained from the actual experiment, so as to verify the model;

[0126] Then, the magnetic flux density and magnetization intensity in the iron core are calculated based on the hysteresis model and solution algorithm; the magnetic flux density b = μH, μ is the magnetic permeability of the iron core material, and H is the magnetic field intensity; the simulation model is run to obtain the distribution of the magnetic flux density and magnetization intensity in the iron core; the change of the magnetic flux density over time is calculated considering the hysteresis characteristics of the iron core, and the state quantity in the hysteresis model (magnetic induction intensity saturation value B s , coercive force H c value)

[0127] And continue to optimize the adjustment coefficient K, so that the image of the hysteresis loop output by the model and the hysteresis loop obtained by the actual experiment of the transformer have a fitting degree greater than 0.9 to obtain the final model B′(H); after verification, according to Faraday's law of electromagnetic induction and Ohm's law, calculate the induced electromotive force and current in the transformer winding to determine whether there is an excitation inrush current, and analyze the various parameters of the excitation inrush current, including: waveform, size, and decay rate; use time domain data to analyze the waveform of the excitation inrush current and draw a time-current diagram; calculate the maximum value and decay rate of the excitation inrush current, and analyze its impact on the performance of the transformer; evaluate the factors affecting the excitation inrush current, including core material, winding design, and access power supply characteristics; and obtain the final simulation results. According to the simulation results, analyze the characteristics of the excitation inrush current of high-impedance transformers with different structures under different parameter conditions (such as temperature and voltage), and adopt different schemes to suppress the excitation inrush current in a targeted manner, alleviate the probability of false operation of zero-sequence overcurrent protection during power grid operation, and improve the stability and safety of power grid operation.

[0128] Example 2

[0129] This embodiment provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the high-impedance transformer excitation inrush current simulation method based on core hysteresis characteristics in Embodiment 1 are implemented.

[0130] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0131] Example 3

[0132] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the high-impedance transformer excitation inrush current simulation method based on the core hysteresis characteristics in Embodiment 1 are implemented.

[0133] The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination of them, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable red-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, disk or optical disk.

[0134] In summary, the present invention establishes a variety of different types of high-impedance transformer models and reserves a plurality of input parameters to simulate the actual transformer structure, and then constructs a hysteresis model for each high-impedance transformer model based on this to describe the hysteresis characteristics of the iron core; then, various parameters of the actual transformer are input into the established hysteresis model, and the magnetic induction intensity saturation value B is determined according to experimental data. s , coercive force H cThe value is substituted into the image of the output hysteresis loop in the model and compared with the hysteresis loop obtained in the actual experiment to verify the model; after the verification, the induced electromotive force and current in the transformer winding are calculated according to Faraday's law of electromagnetic induction and Ohm's law to determine whether there is an excitation inrush current, and the various parameters of the excitation inrush current are analyzed, including: waveform, size, and decay rate; the waveform of the excitation inrush current is analyzed using time domain data, and a time-current diagram is drawn; the maximum value and decay rate of the excitation inrush current are calculated, and their impact on the performance of the transformer is analyzed; the factors affecting the excitation inrush current, including core material, winding design, and access power supply characteristics, are evaluated; the final simulation results are obtained, and the characteristics of the excitation inrush current of high-impedance transformers with different structures under different parameter conditions (such as temperature and voltage) are analyzed based on the simulation results, and different schemes are used to suppress the excitation inrush current in a targeted manner, thereby alleviating the probability of false operation of zero-sequence overcurrent protection during power grid operation and improving the stability and safety of power grid operation.

[0135] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics, characterized in that: The specific steps include: S1. Establish a finite element model of a high impedance transformer in the simulation software; S2. A hysteresis model is established based on the hysteresis characteristics of the iron core to describe the hysteresis characteristics of the iron core; S3, setting corresponding parameters in the simulation model according to the actual parameters of the high impedance transformer; S4, setting the hysteresis characteristic parameters of the iron core; S5. Calculate the magnetic flux density and magnetization intensity in the iron core based on the established hysteresis model and solution algorithm; S6. Considering the hysteresis characteristics of the iron core, calculate the change of magnetic flux density over time, and update the state variables in the hysteresis model; S7. Calculate the induced electromotive force and current in the transformer winding according to Faraday's law of electromagnetic induction and Ohm's law; S8, comparing the calculated current with the rated current to determine whether there is an excitation inrush current; S9. Analyze the various parameters of the excitation surge current including: waveform, size, and decay speed.

2. The method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to claim 1, characterized in that: In step S1, a finite element model of a high impedance transformer is established using MATLAB / Simulink software.

3. The method for simulating high impedance transformer excitation inrush current based on core hysteresis characteristics according to claim 2, characterized in that: The established high impedance transformer finite element model includes a variety of core structures, specifically: a) Winding high impedance transformer; b) Medium voltage split high impedance transformer; c) Low voltage series reactance high impedance transformer; d) High voltage built-in high impedance transformer.

4. The method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to claim 3, characterized in that: In step S2, a hysteresis model is established according to each different core structure; Among them: a) The hysteresis model of the winding high impedance transformer is: B(H)=μ0(H+M(H)) in: Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field intensity; H0 is the material characteristic constant; b) The hysteresis model of the medium voltage split high impedance transformer is: Where: B is the magnetic induction intensity; H is the magnetic field intensity; μ r is the relative magnetic permeability; μ0 is the vacuum magnetic permeability; H s is the saturation magnetic field strength; c) The hysteresis model of low voltage series reactance high impedance transformer is: Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H0 is the material characteristic constant; d) The hysteresis model of the high-voltage built-in high-impedance transformer is: Where: B is the magnetic induction intensity; H is the magnetic field intensity; B s is the saturation magnetic induction intensity; H c The coercive force is the magnetic field strength required for the material to return to a non-magnetic state after the external magnetic field is removed.

5. The method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to claim 1, characterized in that: The parameters input in step S3 include transformer geometric electrical parameters, core material properties, winding parameters, and operating frequency and voltage; The geometric electrical parameters of the transformer include the structure of the core, the structure of the winding, and the parameters of size and weight that affect the heat dissipation performance; they also include rated current, nominal frequency, voltage ratio, current ratio, efficiency and loss, insulation performance, and temperature rise performance; Core material properties include: density, magnetic permeability, and saturation magnetic induction intensity; Winding parameters include: number of turns, coil material, winding resistance; And set boundary conditions according to the actual nameplate parameters of the transformer; specifically including magnetic field boundary, current boundary and voltage boundary.

6. The method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to claim 1, characterized in that: In step S7, the induced electromotive force is calculated according to Faraday's law of electromagnetic induction: Where E is the induced electromotive force, Φ is the magnetic flux; Calculate the current in the winding using Ohm's law: Where R is the total resistance of the winding.

7. The method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to claim 1, characterized in that: In step S8, the rated current value of the transformer is obtained; the calculated current is compared with the rated current to determine whether there is an excitation inrush current; if the calculated current exceeds the rated current, the amplitude of the inrush current is recorded and analyzed.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the high impedance transformer excitation inrush current simulation method based on the core hysteresis characteristics according to any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for simulating magnetizing inrush current of a high impedance transformer based on core hysteresis characteristics according to any one of claims 1 to 7 are implemented.

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