Method, device and equipment for determining stress enhancement factor of transformer winding, and medium

Abstract

The application discloses a stress enhancement factor determination method, device and equipment of a transformer winding and a medium, relates to the field of power transformer stress winding vibration stress analysis, and comprises the following steps: determining the winding current corresponding to the transformer with a target material and a target shape, determining the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency harmonic current based on the winding current; determining the first stress generated by the power frequency current according to the power frequency current component, and determining the total stress generated by the winding current by using a total stress calculation model; the total stress calculation model indicates that the total stress is the sum of the first stress and the third stress; the third stress is the sum of the second stresses generated by different frequency harmonic currents; the second stress is the product of the stress enhancement coefficient and the harmonic current component; the stress enhancement coefficient is a coefficient representing the change of the second stress; and the stress enhancement factor is obtained by calculating the ratio of the total stress to the first stress. The influence of the harmonic current on the winding stress can be effectively analyzed.

Description

Technical Field

[0001] This invention relates to the field of vibration stress analysis technology for power transformer windings, and particularly to a method, apparatus, equipment, and medium for determining the stress enhancement factor of transformer windings. Background Technology

[0002] Currently, with the proposal of the "carbon peak and carbon neutrality" goals and the implementation of the green and low-carbon energy development strategy, a large number of power electronic equipment and renewable energy sources are being connected to the power grid, resulting in a significant increase in harmonic components, unpredictable flow directions, and complex propagation mechanisms. Harmonic currents lead to a significant increase in transformer winding harmonic losses and temperature rise, causing varying degrees of vibration in internal components, resulting in increased noise, seriously endangering mechanical stability, and affecting the reliability of power grid operation. Therefore, studying the impact of harmonic currents on transformer vibration characteristics (stress on transformer windings) is of great significance.

[0003] Regarding methods for calculating transformer winding stress, firstly, Zhang Xuejuan et al. from Shenyang University of Technology, based on the coupled field theory of electromagnetic and mechanical fields, conducted electromagnetic and modal harmonious response analysis on the vibration characteristics of transformer windings under power frequency current. The results showed that the transformer winding exhibits overall symmetrical vibration characteristics under power frequency current, without any singularities. As the preload increases, the winding structure becomes tighter, the stiffness of the spacers increases, and the natural frequency increases accordingly. Secondly, Jin Mingkai et al. from Xi'an Jiaotong University proposed an axial vibration calculation model considering both bidirectional and unidirectional coupling between the magnetic field and structural field. They calculated the axial vibration process of the transformer winding under power frequency current, considering both bidirectional coupling and non-bidirectional coupling, and obtained the variation curves of the maximum vibration parameters of each coil. The results showed that due to the bidirectional coupling between the magnetic field and structural field, the coil vibration intensity increased by 1.1 to 1.55 times, and the maximum electromagnetic force of the middle coil increased by 3.5 times. Furthermore, the maximum electromagnetic force of the middle coil did not occur at the first peak, but rather shifted to the second or third peak. Third, by establishing a two-dimensional winding model of the transformer, the equivalent stiffness matrix of the transformer winding and the correlation coefficient in the dynamic equation are obtained based on the dynamic model of the degree of freedom and the geometric parameter information of the transformer winding. The alternating electrodynamic force is obtained based on the magnetic field distribution of the winding under the action of power frequency current. Then, the vibration response characteristics of the transformer winding under transient conditions are obtained based on the distribution of alternating electrodynamic force.

[0004] However, since harmonic currents contain power frequency and multiple frequency harmonic current components, the resulting electromagnetic force will induce greater stress, which is significantly different from that of power frequency current. Existing research methods cannot be applied to analyze the stress distribution characteristics of windings under the action of harmonic currents.

[0005] In summary, how to analyze the impact of harmonic current on winding stress is an urgent problem to be solved. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method, apparatus, equipment, and medium for determining the stress enhancement factor of transformer windings, which can effectively analyze the influence of harmonic currents on winding stress. The specific solution is as follows:

[0007] In a first aspect, this application discloses a method for determining the stress enhancement factor of a transformer winding, including:

[0008] Determine the winding current corresponding to the target transformer with the target material and target shape, and determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency based on the winding current.

[0009] The target first stress generated by the power frequency current is determined based on the power frequency current component, and the target total stress generated by the winding current is determined using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each harmonic current frequency and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies;

[0010] The stress enhancement factor is obtained by calculating the ratio of the target total stress to the target first stress; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress.

[0011] The step of determining the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current based on the winding current includes:

[0012] Fourier analysis was performed on the winding current to obtain the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current.

[0013] Before determining the target first stress generated by the power frequency current based on the power frequency current component and determining the target total stress generated by the winding current using the target total stress calculation model, the method further includes:

[0014] A transformer simulation model corresponding to the target transformer is constructed, and simulation results are obtained based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies.

[0015] Based on the simulation results, an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current is obtained, and a common stress enhancement coefficient value for the harmonic current at each frequency is determined; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress;

[0016] The target total stress calculation model is determined based on the initial stress calculation model.

[0017] The step of constructing a transformer simulation model corresponding to the target transformer and obtaining simulation results based on the transformer simulation model includes:

[0018] An electromagnetic field model of a transformer is constructed to determine the magnetic induction intensity at various locations of the transformer winding corresponding to different harmonic current components at different frequencies.

[0019] An electromagnetic force calculation model is constructed, and the magnetic induction intensity is substituted into the electromagnetic force calculation model to obtain simulation results.

[0020] The step of obtaining the initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and determining the general stress enhancement coefficient value for the harmonic current at each frequency, includes:

[0021] The simulation results are analyzed using regression analysis to obtain an initial stress calculation model for the single harmonic current, which includes the stress enhancement coefficient, and the stress enhancement coefficient value for the harmonic current at each frequency is determined.

[0022] The step of using regression analysis to analyze the simulation results to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and determining the stress enhancement coefficient value of the harmonic current at each frequency, includes:

[0023] Determine the harmonic current components for each frequency of the harmonic current and calculate the simulated first stress;

[0024] Using regression analysis and based on the simulated total stress, the harmonic current components, and the simulated first stress, an initial stress calculation model containing the stress enhancement coefficient corresponding to a single harmonic current is obtained, and the stress enhancement coefficient value of the harmonic current at each frequency is determined.

[0025] Wherein, determining the harmonic current component of the harmonic current at each frequency includes:

[0026] The effective value of the fundamental current and the effective value of the harmonic current for each frequency are determined, and the harmonic current components are determined based on the effective value of the fundamental current and the effective value of the harmonic current while keeping the effective value of the harmonic current constant.

[0027] Secondly, this application discloses a device for determining the stress enhancement factor of a transformer winding, comprising:

[0028] The current component determination module is used to determine the winding current corresponding to the target transformer of the target material and target shape, and to determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of the harmonic current based on the winding current.

[0029] The target total stress determination module is used to determine the target first stress generated by the power frequency current based on the power frequency current component, and to determine the target total stress generated by the winding current using a target total stress calculation model. The target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress. The target third stress is the sum of the target second stress generated by harmonic currents of different frequencies. The target second stress is the product of the stress enhancement coefficient corresponding to each harmonic current frequency and the harmonic current component. The stress enhancement coefficient is a pre-obtained coefficient representing the variation of the target second stress under harmonic currents of different frequencies.

[0030] The stress enhancement factor calculation module is used to calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress.

[0031] The device for determining the stress enhancement factor of the transformer winding further includes:

[0032] The simulation module is used to construct a transformer simulation model corresponding to the target transformer and obtain simulation results based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies.

[0033] The first model determination module is used to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and to determine the stress enhancement coefficient value common to the harmonic current at each frequency; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress;

[0034] The second model determination module is used to determine the target total stress calculation model based on the initial stress calculation model.

[0035] Thirdly, this application discloses an electronic device, including:

[0036] Memory, used to store computer programs;

[0037] A processor is used to execute the computer program to implement the aforementioned method for determining the stress enhancement factor of transformer windings.

[0038] Fourthly, this application discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the aforementioned method for determining the stress enhancement factor of transformer windings.

[0039] As can be seen, the winding current corresponding to the target transformer with the target material and target shape is determined, and the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current are determined based on the winding current; the target first stress generated by the power frequency current is determined according to the power frequency current component, and the target total stress generated by the winding current is determined using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by the harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each frequency of harmonic current and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies; the ratio of the target total stress to the target first stress is calculated to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress. Therefore, this application proposes a stress enhancement coefficient to represent the change of the second stress under harmonic currents of different frequencies, and based on this coefficient, a new target total stress calculation model is determined, thereby providing a new method for calculating the target total stress. This application also proposes to quantify the influence of harmonic currents of different frequencies on the target total stress using a stress enhancement factor, and proposes a method for calculating the stress enhancement factor, that is, to calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor, thereby effectively analyzing the influence of harmonic currents on winding stress. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0041] Figure 1This is a flowchart of a method for determining the stress enhancement factor of a transformer winding disclosed in this application;

[0042] Figure 2 This is a flowchart of a specific method for determining the stress enhancement factor of a transformer winding disclosed in this application;

[0043] Figure 3 This is a schematic diagram of a stress enhancement factor calculation process disclosed in this application;

[0044] Figure 4 This is a schematic diagram of the main body model of a transformer disclosed in this application;

[0045] Figure 5 This is a three-dimensional transformer model diagram disclosed in this application;

[0046] Figure 6 This is a schematic diagram of a circuit model for a multi-characteristic harmonic disclosed in this application;

[0047] Figure 7 This is a schematic diagram of stress distribution disclosed in this application;

[0048] Figure 8 This is a schematic diagram of the stress on a low-voltage winding under different harmonic current frequencies disclosed in this application.

[0049] Figure 9 This is a schematic diagram of a device for determining the stress enhancement factor of a transformer winding disclosed in this application.

[0050] Figure 10 This is a structural diagram of an electronic device disclosed in this application. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Because harmonic currents contain power frequency and multiple frequency harmonic current components, the resulting electromagnetic force will induce greater stress, which is significantly different from that of power frequency current. Existing research methods are not applicable to analyzing the stress distribution characteristics of windings under the action of harmonic currents.

[0053] Therefore, this application proposes a scheme for determining the stress enhancement factor of transformer windings, which can effectively analyze the influence of harmonic current on winding stress.

[0054] This application discloses a method for determining the stress enhancement factor of a transformer winding. (See also...) Figure 1 As shown, the method includes:

[0055] Step S11: Determine the winding current corresponding to the target transformer of the target material and target shape, and determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency based on the winding current.

[0056] In this embodiment, the winding currents corresponding to transformers of different materials and shapes may be different, and the calculated stress enhancement coefficients may also be different. Therefore, it is necessary to simulate transformers of different materials and shapes in advance to obtain the corresponding stress enhancement coefficients, which will facilitate the subsequent calculation of the stress enhancement factor.

[0057] In this embodiment, when the transformer is under harmonic load, the winding current becomes the superposition of the fundamental component (power frequency current) and the harmonic component (harmonic current). Therefore, it is necessary to separate the two. Specifically, determining the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of the harmonic current based on the winding current includes: performing Fourier analysis on the winding current to obtain the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of the harmonic current.

[0058] In one specific embodiment, Fourier separation is performed on the transformer winding current waveform to extract the power frequency current component. and harmonic current components of different frequencies. The formula is shown below:

[0059] ;

[0060] in, This is the current waveform at time t, in amperes (A). This represents the power frequency current component, measured in amperes (A). The harmonic current component is the nth harmonic current. This is the fundamental frequency of the power frequency, measured in Hz. The frequency of the nth harmonic current is expressed in Hz; n is the harmonic order being considered, which has no unit. It is the phase angle, and the unit is rad.

[0061] Step S12: Determine the target first stress generated by the power frequency current based on the power frequency current component, and determine the target total stress generated by the winding current using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each harmonic current frequency and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies.

[0062] In this embodiment, when calculating the stress borne by the winding, the traditional model usually only considers the stress borne by the transformer winding under the action of pure power frequency current (the first stress). The first stress can be calculated by considering only the pure power frequency current, as shown in the following formula:

[0063] ;

[0064] in, This refers to the electromagnetic force generated by power frequency current; This is the power frequency current, measured in amperes (A). It is the magnetic flux density under power frequency current, and the unit is T; This refers to the length of the transformer's conductors, measured in meters (m). Units are not specified for different load rates; The area under stress is expressed in units of 1000 mm. .

[0065] In this embodiment, the formula for calculating the stress on the winding under harmonic currents of different frequencies is as follows:

[0066] ;

[0067] in, The target second stress generated by the nth harmonic current is expressed in Pa. The electromagnetic force generated by the nth harmonic current, measured in N; This represents the stress enhancement factor corresponding to the nth harmonic current, and has no unit. The harmonic current component is the nth harmonic current, and its unit is A. The magnetic flux density is given by the nth harmonic current, and the unit is T.

[0068] In this embodiment, the target total stress calculation model is as follows:

[0069] ;

[0070] in, This represents the third stress on the target.

[0071] Step S13: Calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress.

[0072] In this embodiment, the stress (target first stress) caused by the electromagnetic force generated by the fundamental current is calculated. For each nth harmonic frequency Calculate the corresponding target third stress Substitute this into the following formula for calculating the stress enhancement factor:

[0073] ;

[0074] in, This represents the stress enhancement factor, indicating the degree to which different combinations of harmonic currents enhance the vibration stress of the winding; it has no unit.

[0075] It should be noted that this application uses the ratio of the stress value of the winding under power frequency current to the stress value of the winding under harmonic current as the stress enhancement factor.

[0076] As can be seen, the winding current corresponding to the target transformer with the target material and target shape is determined, and the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current are determined based on the winding current; the target first stress generated by the power frequency current is determined according to the power frequency current component, and the target total stress generated by the winding current is determined using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by the harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each frequency of harmonic current and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies; the ratio of the target total stress to the target first stress is calculated to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress. Therefore, this application proposes a stress enhancement coefficient to represent the change of the second stress under harmonic currents of different frequencies, and based on this coefficient, a new target total stress calculation model is determined, thereby providing a new method for calculating the target total stress. This application also proposes to quantify the influence of harmonic currents of different frequencies on the target total stress using a stress enhancement factor, and proposes a method for calculating the stress enhancement factor, that is, to calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor, thereby effectively analyzing the influence of harmonic currents on winding stress.

[0077] This application discloses a specific method for determining the stress enhancement factor of a transformer winding. Compared to the previous embodiment, this embodiment further explains and optimizes the technical solution. See also... Figure 2 As shown, it specifically includes:

[0078] Step S21: Construct a transformer simulation model corresponding to the target transformer, and obtain simulation results based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies.

[0079] In this embodiment, the step of constructing a transformer simulation model corresponding to the target transformer and obtaining simulation results based on the transformer simulation model includes: constructing a transformer electromagnetic field model to determine the magnetic induction intensity at each position of the transformer winding corresponding to different harmonic current components at different frequencies; constructing an electromagnetic force calculation model and substituting the magnetic induction intensity into the electromagnetic force calculation model to obtain simulation results.

[0080] Specifically, a refined geometric model of the transformer winding is established, and corresponding material properties and boundary conditions are defined according to the specific type and parameters of the transformer. Based on this, a multiphysics coupling simulation model is constructed. First, an electromagnetic field model is built, and the magnetic field of the converter transformer under harmonic current is calculated using the finite element method. Harmonic current excitation is added by constructing a field-circuit coupling model, and the magnetic induction intensity at each point of the winding is obtained according to the classical Maxwell's equations. The electromagnetic field calculation model of the converter transformer is shown in the following equation:

[0081] ;

[0082] Where B is the magnetic flux density, in tons (T); and J is the winding current density, in cubic meters (m³). D is the electric displacement vector, which has no unit; E is the electric field strength, with units of V / m; H is the magnetic field strength, with units of A / m.

[0083] Then, the electromagnetic force calculation model is constructed as follows:

[0084] ;

[0085] in, This is the winding current-leakage flux ratio coefficient; For harmonic order; for The magnetic flux density at the subharmonic frequency, measured in tons, can be obtained from an electromagnetic field model. ω is the angular frequency.

[0086] In this embodiment, the boundary conditions are set as shown in the following formula:

[0087] ;

[0088] in, This represents the quantity of the coils, without unit. This is the damping coefficient, which has no unit. , These are the stiffness coefficients of the first and last gaskets, respectively, without units; This is the stiffness coefficient, which has no unit. , , These are the axial vibration acceleration, velocity, and displacement vector of the transformer winding, respectively, with units of ; , These are the electromagnetic force and gravity of the transformer windings, respectively.

[0089] It should be noted that this application couples the magnetic induction intensity obtained from the electromagnetic field model to the electromagnetic force calculation model, and uses the time stepping method to solve the coupled equation set (electromagnetic field model and electromagnetic force calculation model) to analyze the dynamic response of the winding under the action of various harmonic currents (simulation results).

[0090] Step S22: Based on the simulation results, obtain the initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and determine the stress enhancement coefficient value common to the harmonic current at each frequency; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress.

[0091] In this embodiment, obtaining the initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and determining the general stress enhancement coefficient value for the harmonic current at each frequency, includes: analyzing the simulation results using regression analysis to obtain the initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and determining the stress enhancement coefficient value for the harmonic current at each frequency.

[0092] In this embodiment, the step of analyzing the simulation results using regression analysis to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and determining the stress enhancement coefficient value of the harmonic current at each frequency, includes: determining the harmonic current component of the harmonic current at each frequency, and calculating the simulated first stress; using regression analysis based on the simulated total stress, the harmonic current component, and the simulated first stress to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and determining the stress enhancement coefficient value of the harmonic current at each frequency.

[0093] In this embodiment, determining the harmonic current component of the harmonic current at each frequency includes: determining the effective value of the fundamental current and the effective value of the harmonic current at each frequency, and determining the harmonic current component based on the effective value of the fundamental current and the effective value of the harmonic current while keeping the effective value of the harmonic current unchanged.

[0094] It should be noted that this application uses regression analysis to process the simulation data and extracts the stress enhancement coefficient, which can describe the stress variation law of the winding under different frequency harmonic currents. Frequency is established through function fitting. Total stress on the lower winding With stress enhancement factor Harmonic current components The relationship is as follows:

[0095] ;

[0096] Harmonic current components The ratio of the effective value of the harmonic current to the effective value of the fundamental current, under the condition that the effective value of the winding current remains constant, is shown in the following formula:

[0097] ;

[0098] in, It represents the harmonic current content of the nth harmonic, and has no unit. This is the effective value of the total winding current, in amperes (A). The nth harmonic is the effective value of the total winding current; It is the effective value of the fundamental current, in amperes (A).

[0099] Step S23: Determine the target total stress calculation model based on the initial stress calculation model.

[0100] In this embodiment, since there are harmonics of different frequencies in the winding current, that is, multiple harmonics, the target total stress calculation model includes the stress caused by the power frequency current and the sum of the stress caused by the harmonic currents of all frequencies.

[0101] As can be seen, this application constructs a transformer simulation model corresponding to the target transformer and obtains simulation results based on the transformer simulation model. The simulation results are the simulated total stress of the transformer windings corresponding to different harmonic current components at different frequencies. Based on the simulation results, an initial stress calculation model containing the stress enhancement coefficient corresponding to a single harmonic current is obtained, and a common stress enhancement coefficient value for the harmonic current at each frequency is determined. The initial stress calculation model indicates that the simulated total stress is the sum of the simulated first stress and the simulated second stress. Based on the initial stress calculation model, the target total stress calculation model is determined. In summary, this application proposes a new method for calculating the stress caused by harmonic currents, that is, using the stress enhancement coefficient to calculate the stress caused by harmonic currents, and thereby proposes a method for calculating the total stress.

[0102] See Figure 3 The diagram shows a flowchart for calculating the stress enhancement factor, which mainly includes four steps: First, a calculation model for the vibration stress enhancement factor considering the influence of harmonics is proposed; second, a multi-physics coupling simulation model of electromagnetic-vibration of the transformer is constructed; third, vibration stress data under the combined action of power frequency and harmonic currents is calculated; and fourth, the value of the winding vibration stress enhancement factor is calculated.

[0103] First, in step one, the calculation method for the stress enhancement factor is determined. Specifically, the total stress is obtained based on the stress generated by the power frequency current and the stress generated by the harmonic current. Then, the calculation formula for the stress enhancement factor is obtained based on the total stress and the stress generated by the power frequency current. In step two, a transformer coupling circuit model and an electromagnetic force model are constructed, and simulation solutions and mathematical fitting are performed to obtain the stress enhancement coefficient. In step three, the power frequency current component and the harmonic current component are obtained, and the stress caused by the power frequency current and the stress caused by the harmonic current are calculated using the stress enhancement coefficient, the power frequency current component, and the harmonic current component to obtain the total stress. In step four, the stress caused by the power frequency current and the total stress are determined, and the stress enhancement factor is calculated.

[0104] In one specific embodiment, taking the SFSZ25000 / 110kV transformer as an example, a detailed implementation method and specific operation process are given. However, the scope of protection of this invention is not limited to the following embodiment.

[0105] 1. Construction of multiphysics model and setting of boundary conditions.

[0106] The main model of the SFSZ25000 / 110kV transformer is as follows: Figure 4 As shown, a three-dimensional transformer model is built using COMSOL. Figure 5As shown in Table 1, the main parameters of the transformer are as follows. The transformer core structure is a three-phase, three-limb type, with the low-voltage winding, medium-voltage winding, and high-voltage winding of each phase all mounted on the same core column. Furthermore, due to the complex main structure of the transformer, to facilitate grid division, small components such as core clamps and winding supports are simplified, and the clamps provide fixed support and shaft support by setting structural mechanical constraints.

[0107] Table 1

[0108]

[0109] A rated excitation current is applied to the low-voltage winding, and harmonic current excitation is added through the field-circuit coupling module. A circuit model containing multiple characteristic harmonics is constructed through the circuit coupling module, such as... Figure 6 As shown, simulation calculations and analyses of electromagnetic fields and structural force fields are carried out based on this. Figure 6 The document discloses the voltages and currents of phases A, B, and C in a transformer, specifically:

[0110] ;

[0111] ;

[0112] ;

[0113] ;

[0114] ;

[0115] ;

[0116] ;

[0117] ;

[0118] .

[0119] in, , , , , , Subscripts with "k" indicate harmonic current sources, while those without "k" refer to fundamental sinusoidal current sources. "s" indicates the harmonic current content, and "A" is the unit of current, ampere. This refers to the current phase angle, measured in rad. This refers to the load rate.

[0120] The transformer winding current is set to 0A, and a voltage excitation is applied to the high-voltage winding. The excitation current expression for the three-phase low-voltage winding of the transformer model is shown below (at rated load, no load factor):

[0121] ;

[0122] ;

[0123] ;

[0124] Under the condition that the effective value of the rated current remains constant, the influence of different harmonic frequencies on the vibration characteristics of the low-voltage winding of an AC transformer is studied. Taking a harmonic content of 5% and harmonic frequencies of 250Hz, 450Hz, 650Hz, 950Hz, 1250Hz, and 1550Hz as examples, the stress on the low-voltage winding of the transformer at time t = 0.03s is compared and analyzed. With the harmonic current content remaining constant, increasing only the harmonic frequency causes the average stress on the low-voltage winding of the transformer to fluctuate according to the frequency of the harmonic current. Under the influence of harmonic frequencies of 350Hz, 550Hz, 950Hz, and 1550Hz, the average stress on the low-voltage winding of the transformer increases; under the influence of harmonic frequencies of 250Hz, 450Hz, 650Hz, and 1250Hz, the average stress on the low-voltage winding of the transformer decreases. See details... Figure 7 The figure shows a stress distribution diagram, illustrating the stress distribution of the low-voltage winding of a transformer under the influence of harmonics at different frequencies when the effective value of the rated current remains unchanged and the harmonic content is 5%.

[0125] To ensure the effective value of the rated current remains constant, taking a 250Hz harmonic current as an example, the maximum stress on the transformer's low-voltage winding increases linearly as the proportion of the superimposed harmonic current increases. When the harmonic current content increases from 0% to 30%, the maximum stress on the transformer's low-voltage winding increases by 8720.6 N / m². Using statistical methods such as regression analysis, the simulation data is processed to extract the stress enhancement coefficient kn, which describes the quantitative law of the change in stress value of the winding with the harmonic current content under different frequency harmonic currents. The distribution law of the maximum stress point on the transformer's low-voltage winding is fitted as shown in the following formula. From the fitting formula, the stress enhancement coefficient kn is 2197.58859.

[0126] ;

[0127] Fitting the stress values ​​of AC transformer windings under different frequency harmonic currents reveals that, with increasing harmonic current content, the stress on the low-voltage windings under different harmonic current frequencies exhibits different trends, such as... Figure 8As shown, under the influence of harmonic frequencies of 250Hz, 350Hz, 550Hz, 950Hz, and 1550Hz, the maximum stress on the low-voltage winding of the transformer increases. Under the influence of harmonic frequencies of 450Hz and 1250Hz, the maximum stress on the low-voltage winding of the transformer decreases. Under the influence of harmonic frequencies of 650Hz and 1250Hz, the maximum stress on the low-voltage winding of the transformer does not change much. The distribution law of the maximum stress on the low-voltage winding of the transformer under the influence of different harmonic frequencies is linearly fitted, as shown in Table 2, which is the fitting formula of the maximum stress on the low-voltage winding of the AC transformer and the harmonic current content.

[0128] Table 2

[0129]

[0130] Statistical methods such as regression analysis were used to process simulation data under the action of harmonic currents of different frequencies, and the stress enhancement coefficients kn of different frequency harmonic currents were extracted. As shown in the table above, the stress enhancement coefficient k5 of the 250Hz harmonic current is 2197.58859, the stress enhancement coefficient k7 of the 350Hz harmonic current is 19636.5156, the stress enhancement coefficient k9 of the 450Hz harmonic current is -4992.6885, the stress enhancement coefficient k11 of the 550Hz harmonic current is 7186.1251, the stress enhancement coefficient k13 of the 650Hz harmonic current is 3833.2985, the stress enhancement coefficient k19 of the 950Hz harmonic current is 16774.5979, the stress enhancement coefficient k25 of the 1250Hz harmonic current is -465.845, and the stress enhancement coefficient k31 of the 1550Hz harmonic current is 7186.1251. It should be noted that the higher the degree of fit optimization, the better the optimization effect.

[0131] 2. Subsequently, the stress on the same transformer can be calculated using the corresponding stress enhancement coefficient. Based on the current waveform of the transformer winding, Fourier analysis is performed to separate and analyze the power frequency current component I1, extract the harmonic current components In of different frequencies, and use them as the circuit excitation source of the electromagnetic-vibration multiphysics model for simulation calculation. In this example, with the load rate unchanged at the rated load, the 250Hz harmonic current content is 20%, the 350Hz harmonic content is 15%, the 450Hz harmonic content is 10%, the 550Hz harmonic content is 5%, the 650Hz harmonic content is 5%, the 950Hz harmonic content is 3%, the 1250Hz harmonic content is 3%, and the 1550Hz harmonic content is 1%. The magnitude of the vibration stress on the AC transformer winding under the action of different harmonic current components is calculated.

[0132] First, the vibration stress data under the action of power frequency and harmonic currents are obtained. Based on this model, the stress at power frequency can be expressed as: ;

[0133] Next, the stress components caused by harmonic currents of different frequencies are calculated as follows:

[0134] ;

[0135] Finally, the fundamental stress and the stress components generated by all harmonics are summed to obtain the total stress of the winding vibration:

[0136] ;

[0137] 3. Based on the calculation model of winding vibration stress enhancement factor considering the influence of harmonic currents, the vibration stress enhancement factor of AC transformer windings under the combined action of different harmonic current components is calculated as follows: 250Hz harmonic current content is 20%, 350Hz harmonic content is 15%, 450Hz harmonic content is 10%, 550Hz harmonic content is 5%, 650Hz harmonic content is 5%, 950Hz harmonic content is 3%, 1250Hz harmonic content is 3%, and 1550Hz harmonic content is 1%.

[0138] .

[0139] Accordingly, this application also discloses a device for determining the stress enhancement factor of a transformer winding, see [link to relevant documentation]. Figure 9 As shown, the device includes:

[0140] The current component determination module 11 is used to determine the winding current corresponding to the target transformer of the target material and the target shape, and to determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of the harmonic current based on the winding current.

[0141] The target total stress determination module 12 is used to determine the target first stress generated by the power frequency current based on the power frequency current component, and to determine the target total stress generated by the winding current using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each frequency of harmonic current and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies;

[0142] The stress enhancement factor calculation module 13 is used to calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress.

[0143] In one embodiment, the stress enhancement factor determination device for the transformer winding further includes:

[0144] The simulation module is used to construct a transformer simulation model corresponding to the target transformer and obtain simulation results based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies.

[0145] The first model determination module is used to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and to determine the stress enhancement coefficient value common to the harmonic current at each frequency; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress;

[0146] The second model determination module is used to determine the target total stress calculation model based on the initial stress calculation model.

[0147] The more specific working process of each of the above modules can be found in the corresponding content disclosed in the foregoing embodiments, and will not be repeated here.

[0148] As can be seen, the winding current corresponding to the target transformer with the target material and target shape is determined, and the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current are determined based on the winding current; the target first stress generated by the power frequency current is determined according to the power frequency current component, and the target total stress generated by the winding current is determined using the target total stress calculation model; the target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; the target third stress is the sum of the target second stress generated by the harmonic currents of different frequencies; the target second stress is the product of the stress enhancement coefficient corresponding to each frequency of harmonic current and the harmonic current component; the stress enhancement coefficient is a pre-obtained coefficient representing the change of the target second stress under harmonic currents of different frequencies; the ratio of the target total stress to the target first stress is calculated to obtain the stress enhancement factor; the stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress. Therefore, this application proposes a stress enhancement coefficient to represent the change of the second stress under harmonic currents of different frequencies, and based on this coefficient, a new target total stress calculation model is determined, thereby providing a new method for calculating the target total stress. This application also proposes to quantify the influence of harmonic currents of different frequencies on the target total stress using a stress enhancement factor, and proposes a method for calculating the stress enhancement factor, that is, to calculate the ratio of the target total stress to the target first stress to obtain the stress enhancement factor, thereby effectively analyzing the influence of harmonic currents on winding stress.

[0149] Furthermore, embodiments of this application also provide an electronic device. Figure 10 This is a structural diagram of an electronic device 20 according to an exemplary embodiment. The content of the diagram should not be construed as limiting the scope of this application.

[0150] Figure 10 This is a schematic diagram of the structure of an electronic device 20 provided in an embodiment of this application. Specifically, the electronic device 20 may include: at least one processor 21, at least one memory 22, a display screen 23, an input / output interface 24, a communication interface 25, a power supply 26, and a communication bus 27. The memory 22 stores a computer program, which is loaded and executed by the processor 21 to implement the relevant steps in the method for determining the stress enhancement factor of transformer windings disclosed in any of the foregoing embodiments. Alternatively, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0151] In this embodiment, the power supply 26 is used to provide operating voltage for each hardware device on the electronic device 20; the communication interface 25 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and is not specifically limited here; the input / output interface 24 is used to acquire external input data or output data to the outside world, and its specific interface type can be selected according to specific application needs, and is not specifically limited here.

[0152] Furthermore, the memory 22, as a carrier for resource storage, can be a read-only memory, random access memory, disk, or optical disk, etc. The resources stored thereon may include computer programs 221, and the storage method may be temporary storage or permanent storage. In addition to including computer programs capable of performing the method for determining the stress enhancement factor of transformer windings executed by electronic device 20 as disclosed in any of the foregoing embodiments, the computer program 221 may further include computer programs capable of performing other specific tasks.

[0153] Furthermore, embodiments of this application also disclose a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, it implements the aforementioned method for determining the stress enhancement factor of transformer windings.

[0154] The specific steps of this method can be found in the corresponding content disclosed in the foregoing embodiments, and will not be repeated here.

[0155] The various embodiments in this application are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. For the same or similar parts between the various embodiments, refer to each other. As for the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and relevant parts can be referred to in the method section.

[0156] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0157] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0158] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only 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 one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0159] The above provides a detailed description of the method, apparatus, equipment, and storage medium for determining the stress enhancement factor of a transformer winding provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for determining the stress enhancement factor of a transformer winding, characterized in that, include: Determine the winding current corresponding to the target transformer with the target material and target shape, and determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency based on the winding current. The target first stress generated by the power frequency current is determined based on the power frequency current component, and the target total stress generated by the winding current is determined using the target total stress calculation model; The target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; The target third stress is the sum of the target second stresses generated by harmonic currents of different frequencies; The target second stress is the product of the stress enhancement coefficient corresponding to the harmonic current at each frequency and the harmonic current component. The stress enhancement coefficient is a pre-obtained coefficient representing the change in the second stress of the target under harmonic currents of different frequencies; The stress enhancement factor is obtained by calculating the ratio of the total target stress to the first target stress. The stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress; Before determining the target first stress generated by the power frequency current based on the power frequency current component and determining the target total stress generated by the winding current using the target total stress calculation model, the method further includes: A transformer simulation model corresponding to the target transformer is constructed, and simulation results are obtained based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies. Based on the simulation results, an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current is obtained, and a common stress enhancement coefficient value for the harmonic current at each frequency is determined; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress; The target total stress calculation model is determined based on the initial stress calculation model; The step of constructing a transformer simulation model corresponding to the target transformer and obtaining simulation results based on the transformer simulation model includes: An electromagnetic field model of a transformer is constructed to determine the magnetic induction intensity at various locations of the transformer winding corresponding to different harmonic current components at different frequencies. An electromagnetic force calculation model is constructed, and the magnetic induction intensity is substituted into the electromagnetic force calculation model to obtain simulation results; The step of obtaining the initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and determining the general stress enhancement coefficient value for the harmonic current at each frequency, includes: The simulation results are analyzed using regression analysis to obtain an initial stress calculation model for the single harmonic current, which includes the stress enhancement coefficient, and the stress enhancement coefficient value for the harmonic current at each frequency is determined.

2. The method for determining the stress enhancement factor of a transformer winding according to claim 1, characterized in that, The determination of the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current based on the winding current includes: Fourier analysis was performed on the winding current to obtain the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of harmonic current.

3. The method for determining the stress enhancement factor of a transformer winding according to claim 1, characterized in that, The simulation results are analyzed using regression analysis to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and the stress enhancement coefficient value of the harmonic current at each frequency is determined, including: Determine the harmonic current components for each frequency of the harmonic current and calculate the simulated first stress; Using regression analysis and based on the simulated total stress, the harmonic current components, and the simulated first stress, an initial stress calculation model containing the stress enhancement coefficient corresponding to a single harmonic current is obtained, and the stress enhancement coefficient value of the harmonic current at each frequency is determined.

4. The method for determining the stress enhancement factor of a transformer winding according to claim 3, characterized in that, Determining the harmonic current components for each frequency of the harmonic current includes: The effective value of the fundamental current and the effective value of the harmonic current for each frequency are determined, and the harmonic current components are determined based on the effective value of the fundamental current and the effective value of the harmonic current while keeping the effective value of the harmonic current constant.

5. A device for determining the stress enhancement factor of a transformer winding, characterized in that, include: The current component determination module is used to determine the winding current corresponding to the target transformer of the target material and target shape, and to determine the power frequency current component corresponding to the power frequency current and the harmonic current component corresponding to each frequency of the harmonic current based on the winding current. The target total stress determination module is used to determine the target first stress generated by the power frequency current based on the power frequency current component, and to determine the target total stress generated by the winding current using the target total stress calculation model; The target total stress calculation model indicates that the target total stress is the sum of the target first stress and the target third stress; The target third stress is the sum of the target second stresses generated by harmonic currents of different frequencies; The target second stress is the product of the stress enhancement coefficient corresponding to the harmonic current at each frequency and the harmonic current component. The stress enhancement coefficient is a pre-obtained coefficient representing the change in the second stress of the target under harmonic currents of different frequencies; The stress enhancement factor calculation module is used to calculate the ratio of the total target stress to the first target stress to obtain the stress enhancement factor; The stress enhancement factor is used to quantify the influence of harmonic currents of different frequencies on the target total stress; The device for determining the stress enhancement factor of the transformer winding further includes: The simulation module is used to construct a transformer simulation model corresponding to the target transformer and obtain simulation results based on the transformer simulation model; the simulation results are the simulated total stress of the transformer winding corresponding to different harmonic current components at different frequencies. The first model determination module is used to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current based on the simulation results, and to determine the stress enhancement coefficient value common to the harmonic current at each frequency; the initial stress calculation model indicates that the total simulated stress is the sum of the simulated first stress and the simulated second stress; The second model determination module is used to determine the target total stress calculation model based on the initial stress calculation model. Specifically, the simulation module is used to construct a transformer electromagnetic field model to determine the magnetic induction intensity at each position of the transformer winding corresponding to different harmonic current components at different frequencies. An electromagnetic force calculation model is constructed, and the magnetic induction intensity is substituted into the electromagnetic force calculation model to obtain simulation results; Specifically, the first model determination module is used to analyze the simulation results using regression analysis to obtain an initial stress calculation model containing the stress enhancement coefficient corresponding to the single harmonic current, and to determine the stress enhancement coefficient value of the harmonic current at each frequency.

6. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor for executing the computer program to implement the method for determining the stress enhancement factor of a transformer winding as described in any one of claims 1 to 4.

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