Transformer internal short circuit multi-scale fault analysis model construction method and device

Abstract

The invention discloses a transformer internal short circuit multi-scale fault analysis model construction method and device, which are used for solving the technical problem of poor model circuit adaptability caused by the existing transformer internal short circuit multi-scale fault analysis technology. The method comprises the following steps: in response to a construction request, disassembling a transformer, and determining a plurality of sub-windings; performing parameter identification according to a transformer finite element model corresponding to the transformer by adopting a parameter scanning method and a Kirchhoff's current law, and determining a resistance matrix and an inductance correlation matrix; determining a coupling leakage inductance matrix based on the inductance correlation quantity matrix; constructing a multi-scale circuit model of the transformer according to the resistance matrix, the coupling leakage inductance matrix and the number of turns of each sub-winding; and connecting a plurality of sub-winding terminals in the transformer multi-scale circuit model based on the transformer electromagnetic connection relation and the internal short circuit physical process, and generating a transformer internal short circuit multi-scale fault analysis model.

Description

Technical Field

[0001] The present invention relates to the technical field of electric power equipment, and in particular to a method and device for constructing a transformer internal short circuit multi-scale fault analysis model. Background Art

[0002] Transformers (including converter transformers) are high-value core equipment of the power system, which is related to the safe and stable operation of the entire power grid. In recent years, there have been many internal short-circuit accidents of transformers at home and abroad, causing structural instability and explosion of equipment, and the safe operation of transformers and power grids faces major risks. According to statistics from the A2.33 working group of CIGRE (International Conference on Large Electric Systems), about 10% of internal faults of oil-immersed transformers will cause explosions and fires, which can easily lead to chain accidents, causing major economic losses and social impacts.

[0003] Internal short circuit is one of the most serious faults faced by transformers. The initial characteristics of this fault are not obvious, it develops rapidly and the fault current is extremely large. Due to these characteristics, the internal short circuit test of the transformer is a destructive test and it is difficult to carry out a real test. At present, most transformer equipment manufacturing companies use the field-circuit coupling analysis method to simulate this fault, thereby studying the electromagnetic transient characteristics of the internal short circuit fault of the transformer, thereby providing support for transformer design verification and accident analysis. In addition, in order to improve the simulation efficiency and improve the adaptability of the model to the external power grid connection, a transformer circuit model can also be established to analyze the internal short circuit fault.

[0004] Most of the existing transformer internal short-circuit multi-scale fault analysis technologies use the field-circuit coupling method, which establishes a finite element fault analysis model based on the physical size and material properties of the transformer. However, for large-capacity transformers with complex internal structures, due to the numerous potential short-circuit conditions, the field-circuit coupling method cannot traverse and simulate all conditions, and the transformer circuit model is difficult to jointly model with the external power grid, resulting in poor model circuit adaptability. Summary of the invention

[0005] The present invention provides a method for constructing a transformer internal short circuit multi-scale fault analysis model, which is used to solve the technical problem that the existing transformer internal short circuit multi-scale fault analysis technology causes poor model circuit adaptability.

[0006] A first aspect of the present invention provides a method for constructing a transformer internal short circuit multi-scale fault analysis model, comprising:

[0007] In response to a build request, the transformer is disassembled to identify a plurality of sub-windings;

[0008] Using parameter scanning method and Kirchhoff's current law to perform parameter identification according to the transformer finite element model corresponding to the transformer, and determine the resistance matrix and the inductance related quantity matrix;

[0009] Determining a coupled leakage inductance matrix based on the inductance-related quantity matrix;

[0010] Constructing a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding;

[0011] Based on the electromagnetic connection relationship and the internal short-circuit physical process of the transformer, multiple sub-winding terminals in the transformer multi-scale circuit model are connected to generate a transformer internal short-circuit multi-scale fault analysis model.

[0012] Optionally, the inductance-related quantity matrix includes a self-inductance and mutual inductance matrix, a reduced-order inductance matrix and a short-circuit inductance matrix; the parameter scanning method and Kirchhoff's current law are used to perform parameter identification according to a transformer finite element model corresponding to the transformer to determine a resistance matrix and an inductance-related quantity matrix, including:

[0013] Based on the parameter scanning method, a parameter scanning calculation is performed on the transformer finite element model corresponding to the transformer to determine the resistance matrix and the self-inductance and mutual inductance matrix;

[0014] Determine a reduced-order inductance matrix using Kirchhoff's current law according to a voltage drop equation caused by the inductance part corresponding to the self-inductance and mutual-inductance matrix;

[0015] Determining a plurality of short-circuit inductance matrix elements based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix;

[0016] A short-circuit inductance matrix is ​​constructed by using a plurality of the short-circuit inductance matrix elements.

[0017] Optionally, determining a coupled leakage inductance matrix based on the inductance-related quantity matrix includes:

[0018] Based on the self-inductance and mutual-inductance matrix, determining a coupled leakage inductance matrix;

[0019] or determining a coupled leakage inductance matrix based on the reduced-order inductance matrix;

[0020] Or based on the short-circuit inductance matrix, a coupled leakage inductance matrix is ​​determined.

[0021] Optionally, determining a coupled leakage inductance matrix based on the self-inductance and mutual inductance matrix includes:

[0022] Based on a plurality of self-inductance and mutual-inductance matrix elements in the self-inductance and mutual-inductance matrix, determining a plurality of coupling leakage inductance matrix main diagonal elements and a plurality of coupling leakage inductance matrix off-diagonal elements;

[0023] A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

[0024] Optionally, determining a coupled leakage inductance matrix based on the reduced-order inductance matrix includes:

[0025] Based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements;

[0026] A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

[0027] Optionally, determining a coupled leakage inductance matrix based on the short-circuit inductance matrix includes:

[0028] Based on a plurality of short-circuit inductance matrix elements in the short-circuit inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements;

[0029] A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

[0030] A second aspect of the present invention provides a device for constructing a transformer internal short circuit multi-scale fault analysis model, comprising:

[0031] A response module, used for responding to the construction request, disassembling the transformer, and determining a plurality of sub-windings;

[0032] A parameter identification module, used to perform parameter identification according to a transformer finite element model corresponding to the transformer by using a parameter scanning method and Kirchhoff's current law, and determine a resistance matrix and an inductance related quantity matrix;

[0033] A coupled leakage inductance matrix determination module is used to determine a coupled leakage inductance matrix based on the inductance-related quantity matrix;

[0034] A construction module, used to construct a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding;

[0035] A generation module is used to connect multiple sub-winding terminals in the transformer multi-scale circuit model based on the transformer electromagnetic connection relationship and the internal short-circuit physical process to generate a transformer internal short-circuit multi-scale fault analysis model.

[0036] A third aspect of the present invention provides a computer device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in any one of the above items.

[0037] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in any one of the above items.

[0038] A fifth aspect of the present invention provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in any one of the above items.

[0039] It can be seen from the above technical solutions that the present invention has the following advantages:

[0040] The above technical scheme of the present invention provides a method for constructing a multi-scale fault analysis model of internal short circuit of a transformer. When it is necessary to construct a multi-scale fault analysis model of internal short circuit of a transformer, the transformer is first disassembled to determine multiple sub-windings; then, parameter identification is performed according to the transformer finite element model corresponding to the transformer using the parameter scanning method and Kirchhoff's current law to determine the resistance matrix and the inductance related quantity matrix; based on the inductance related quantity matrix, the coupling leakage inductance matrix is ​​determined; a multi-scale circuit model of the transformer is constructed according to the resistance matrix, the coupling leakage inductance matrix and the number of turns of each sub-winding; finally, based on the electromagnetic connection relationship of the transformer and the internal short circuit physical process, multiple sub-winding terminals in the transformer multi-scale circuit model are connected to generate a multi-scale fault analysis model of internal short circuit of the transformer; based on the above scheme, the resistance matrix and the coupling leakage inductance matrix are obtained according to the transformer finite element model corresponding to the transformer using the parameter scanning method and Kirchhoff's current law, and the multi-scale fault analysis model of internal short circuit of the transformer is generated in combination with the electromagnetic connection relationship of the transformer and the internal short circuit physical process, which can be used to simulate and analyze different internal short circuit conditions of transformer equipment, facilitate joint modeling with the external power grid, thereby improving the adaptability of the model circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 paying creative labor.

[0042] Figure 1 A flowchart of a method for constructing a transformer internal short-circuit multi-scale fault analysis model provided in the first embodiment of the present invention;

[0043] Figure 2A schematic diagram of the structure of a single-phase double-winding transformer provided in Embodiment 1 of the present invention;

[0044] Figure 3 A schematic diagram of the structure of a transformer leakage inductance equivalent circuit provided in Embodiment 1 of the present invention;

[0045] Figure 4 A schematic diagram of the structure of a transformer leakage inductance equivalent circuit provided in Embodiment 1 of the present invention;

[0046] Figure 5 A schematic diagram of the structure of a transformer multi-scale circuit model provided in Embodiment 1 of the present invention;

[0047] Figure 6 This is a structural block diagram of a device for constructing a multi-scale fault analysis model for internal short circuit of a transformer provided in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0048] The embodiment of the present invention provides a method for constructing a transformer internal short circuit multi-scale fault analysis model, which is used to solve the technical problem that the existing transformer internal short circuit multi-scale fault analysis technology causes poor model circuit adaptability.

[0049] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] See also Figure 1 , Figure 1 A flowchart of the steps of a method for constructing a multi-scale fault analysis model for internal short circuit of a transformer provided in Example 1 of the present invention.

[0051] The present invention provides a method for constructing a transformer internal short circuit multi-scale fault analysis model, comprising:

[0052] Step 101: In response to a construction request, disassemble the transformer and determine a plurality of sub-windings.

[0053] It should be noted that in order to make the transformer model have the ability to characterize multi-scale magnetic coupling characteristics, each transformer winding is decomposed into n sub-windings for modeling. Each sub-winding can be a single-turn, multi-turn, single-cake, or multi-cake coil. Technical personnel in this field can determine it according to the short-circuit situation or fault analysis requirements. In theory, the finer the decomposition, the stronger the model characterization ability. Considering the impact of the short-circuit turns on the transient current of the port and the complexity of constructing the finite element model, the decomposition by cakes can better characterize various internal short-circuit situations.

[0054] For further information, see Figure 2 , taking a single-phase double-winding transformer as an example, its structure is as follows Figure 2 shown. Figure 2 Where: k represents the number of each sub-winding (k=1, 2, 3......, n), W k Indicates the top lead-out terminal of the kth sub-winding, W m+1 Indicates the terminal leading out of the top of the m+1th sub-winding, W m’ Indicates the terminal leading out of the top of the m'th sub-winding, W n’ Indicates the top lead-out terminal of the n'th sub-winding, N1 and N2 respectively represent the number of turns of the high-voltage and low-voltage windings, and U H , U L Respectively represent the high voltage and low voltage winding voltages, I H ,I L Represent the high voltage and low voltage winding currents respectively.

[0055] It is worth mentioning that for transformer equipment, including single-phase transformers, three-phase transformers, converter transformers, voltage transformers, current transformers and other coil equipment; for multi-scale segmentation of windings, it can be single-turn, single-die, multi-die, integral and other coils of any scale.

[0056] Step 102: Use parameter scanning method and Kirchhoff's current law to perform parameter identification according to the transformer finite element model corresponding to the transformer, and determine the resistance matrix and the inductance related quantity matrix.

[0057] The inductance related quantity matrix includes self-inductance mutual inductance matrix, reduced-order inductance matrix and short-circuit inductance matrix.

[0058] Specifically, the process of performing parameter identification according to the transformer finite element model corresponding to the transformer by using the parameter scanning method and Kirchhoff's current law to determine the resistance matrix and the inductance related quantity matrix can be achieved by executing the following steps S21 to S24:

[0059] Step S21, performing parameter scanning calculation on the transformer finite element model corresponding to the transformer based on the parameter scanning method to determine the resistance matrix and the self-inductance and mutual inductance matrix;

[0060] It should be noted that in order to obtain the self-inductance-mutual inductance matrix (self-inductance-mutual inductance matrix) and resistance matrix of each sub-winding of the transformer, the present invention performs parameter extraction based on the finite element model of the transformer and adopts parametric scanning calculation, that is, the magnetic field module based on the finite element model of the transformer is calculated by parametric scanning to obtain the resistance matrix and self-inductance-mutual inductance matrix of each sub-winding; wherein, the modeling accuracy of each winding can be any scale such as the entire winding, multi-pancake level, pancake level, turn level, etc., depending on the accuracy of the circuit model to be constructed.

[0061] Furthermore, when obtaining the self-inductance of the kth sub-winding and the mutual inductance parameters between it and other sub-windings, current excitation is applied to the kth sub-winding, and other sub-windings remain open (k= 1, 2, 3......, n). Disable the circuit interface, use parametric sweep for steady-state calculation, apply current excitation to each sub-winding in turn, and the sweep matrix is:

[0062] ;

[0063] in, is the first row matrix row phasor; is the row phasor of the second row matrix; is the row phasor of the nth row matrix; I is the current excitation.

[0064] Furthermore, the matrix row phasor I k It represents the current excitation applied to the corresponding sub-winding each time it is calculated in the scan, and the column phasor represents the current excitation applied to each sub-winding in this calculation.

[0065] Based on the above steps, the transformer sub-winding The self-inductance-mutual inductance matrix L and the resistance matrix R are of order, where the calculation result of each scan corresponds to the resistance of the excitation sub-winding in that scan.

[0066] It is worth mentioning that the transformer finite element model corresponding to the transformer can be obtained by referring to the process of constructing the transformer finite element model in the prior art, which will not be elaborated in detail in the present invention.

[0067] Step S22: using Kirchhoff's current law to determine the reduced-order inductance matrix according to the voltage drop equation caused by the inductance part corresponding to the self-inductance and mutual-inductance matrix.

[0068] It should be noted that when one side of the winding is connected to the excitation source, the electromagnetic induction will generate an induced voltage in the other windings. At this time, the voltage-current relationship of the transformer port with n sub-windings satisfies the mathematical expression of the voltage-current relationship of the transformer port, thereby obtaining the steady-state transformer port voltage-current relationship equation. The steady-state transformer port voltage-current relationship equation is the transformer port voltage-current relationship equation in the steady-state form, which can be expressed as:

[0069] ;

[0070] in, is the first component phasor in the port voltage phasor V'; is the second component phasor in the port voltage phasor V'; is the nth component phasor in the port voltage phasor V'; is the matrix element of the first row and first column in the impedance matrix Z; is the matrix element in the first row and second column of the impedance matrix Z; is the matrix element in the first row and nth column of the impedance matrix Z; is the matrix element in the second row and first column of the impedance matrix Z; is the matrix element of the second row and second column in the impedance matrix Z; is the matrix element in the second row and nth column of the impedance matrix Z; is the matrix element in the nth row and first column of the impedance matrix Z; is the matrix element in the nth row and second column of the impedance matrix Z; is the matrix element of the nth row and nth column in the impedance matrix Z; is the first component phasor in the port current phasor I; is the second component phasor in the port current phasor I; is the nth component phasor in the port current phasor I.

[0071] Furthermore, for transient calculation, the steady-state transformer port voltage-current relationship equation can be rewritten as the transient transformer port voltage-current relationship equation. The transient transformer port voltage-current relationship equation is the transformer port voltage-current relationship equation in the transient form. The equation can be expressed as:

[0072] ;

[0073] in, is the first component phasor in the port voltage phasor V'; is the second component phasor in the port voltage phasor V'; is the nth component phasor in the port voltage phasor V'; is the matrix element of the first row and first column in the resistance matrix R; is the matrix element of the second row and second column in the resistance matrix R; is the matrix element of the nth row and nth column in the resistance matrix R; is the first component phasor in the port current phasor I; is the second component phasor in the port current phasor I; is the nth component phasor in the port current phasor I; is the self-inductance-mutual inductance matrix element in the first row and first column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the first row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the first row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual-inductance matrix element in the second row and first column of the self-inductance-mutual-inductance matrix L; is the self-inductance-mutual-inductance matrix element in the second row and second column of the self-inductance-mutual-inductance matrix L; is the self-inductance-mutual inductance matrix element in the second row and nth column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and first column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and nth column in the self-inductance-mutual inductance matrix L.

[0074] Based on the above steps, it can be known that V' represents the port voltage phasor, I represents the port current phasor, the resistance matrix R represents the real part of the impedance matrix Z, and the self-inductance-mutual inductance matrix L (self-inductance-mutual inductance matrix) represents the imaginary part of the impedance matrix Z divided by the angular frequency ω (the angular frequency of the AC circuit where the transformer is located, that is, the angular frequency of the transformer).

[0075] Furthermore, the port voltage phasor V' can be expressed as a series connection of two parts (the voltage drop caused by the inductance part and the voltage drop caused by the resistance part). Therefore, based on the transient transformer port voltage-current relationship equation, the voltage drop equation caused by the inductance part corresponding to the self-inductance and mutual inductance matrix can be expressed as:

[0076] ;

[0077] in, It is the first component phase quantity of the voltage drop phase quantity V caused by the inductance part; It is the second component phase quantity of the voltage drop phase quantity V caused by the inductance part; is the nth component phasor of the voltage drop phasor V caused by the inductance part; is the self-inductance-mutual inductance matrix element in the first row and first column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the first row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the first row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual-inductance matrix element in the second row and first column of the self-inductance-mutual-inductance matrix L; is the self-inductance-mutual-inductance matrix element in the second row and second column of the self-inductance-mutual-inductance matrix L; is the self-inductance-mutual inductance matrix element in the second row and nth column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and first column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and second column of the self-inductance-mutual inductance matrix L; is the self-inductance-mutual inductance matrix element in the nth row and nth column of the self-inductance-mutual inductance matrix L; is the first component phasor in the port current phasor I; is the second component phasor in the port current phasor I; is the nth component phasor in the port current phasor I.

[0078] Furthermore, ignoring the excitation current, the corresponding expression can be obtained according to Kirchhoff's Current Law (KCL):

[0079] ;

[0080] in, is the current of the nth sub-winding; is the current of the kth sub-winding.

[0081] Furthermore, in order to facilitate the short-circuit circuit connection of the internal fault at any position, it is generally necessary to split the winding into sub-windings of equal size according to the actual single-phase transformer, but the element values ​​of the self-inductance-mutual inductance matrix are similar, with pathological characteristics, and generally cannot be directly calculated using Kirchhoff's current law. Therefore, the present invention proposes to combine Kirchhoff's current law and the voltage drop equation caused by the inductance part to obtain a reduced-order inductance matrix; specifically, the elements of the 1st to n-1th rows in the voltage drop equation caused by the inductance part are all subtracted from the elements of the nth row, and combined with Kirchhoff's current law, the expression of the voltage drop between the i-th sub-winding and the last sub-winding n can be obtained, and the n-1-order reduced-order inductance matrix L' (i, j=1, 2, 3......, n-1) about the original self-inductance-mutual inductance matrix is ​​obtained; wherein, the expression of the voltage drop between the i-th sub-winding and the last sub-winding n is specifically:

[0082] ;

[0083] in, It is the first component phase quantity of the voltage drop phase quantity V caused by the inductance part; It is the second component phase quantity of the voltage drop phase quantity V caused by the inductance part; is the nth component phasor of the voltage drop phasor V caused by the inductance part; is the n-1th component phasor of the voltage drop phasor V caused by the inductance part; is the reduced-order inductance matrix element of the first row and first column in the reduced-order inductance matrix L'; is the reduced-order inductance matrix element of the first row and second column in the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the first row and the n-1th column in the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the second row and first column of the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the second row and second column of the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the second row and the n-1th column in the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the n-1th row and the first column of the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the n-1th row and the second column in the reduced-order inductance matrix L'; is the reduced-order inductance matrix element in the n-1th row and the n-1th column in the reduced-order inductance matrix L'; is the first component phasor in the port current phasor I; is the second component phasor in the port current phasor I; is the nth component phasor in the port current phasor I.

[0084] Step S23, determining a plurality of short-circuit inductance matrix elements based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix;

[0085] The plurality of short-circuit inductance matrix elements include a plurality of short-circuit inductance matrix elements in the i-th row and the n-th column, representing the short-circuit inductance L between the i-th and the n-th sub-windings. s-i,n , a plurality of short-circuit inductance matrix elements of the i-th row and the j-th column, representing the short-circuit inductance L between the i-th and j-th sub-windings s-i,j .

[0086] It should be noted that, based on the above content, the correlation between the short-circuit inductance matrix elements and the reduced-order inductance matrix elements is further derived; specifically, please refer to Figure 3 , the i-th sub-winding is excited, and the n-th sub-winding is short-circuited. Figure 3 As shown, Figure 3 Middle: W i Indicates the sub-winding number, V i Indicates the excitation power supply voltage, I i Represents the excitation winding current, I n represents the short-circuited sub-winding current. Therefore, the current phasor in the expression for the voltage drop between the ith sub-winding and the last sub-winding n contains only I i is not zero, and Vn =0, then the short-circuit inductance matrix element in the i-th row and the n-th column, i.e., the short-circuit inductance L between the i-th and n-th sub-windings s-i,n The calculation process is:

[0087] ;

[0088] in, is the short-circuit inductance between the ith and nth sub-windings; is the excitation power supply voltage; is the short-circuit winding voltage; is the excitation sub-winding current; is the reduced-order inductor matrix element in the i-th row and i-th column of the reduced-order inductor matrix.

[0089] Similarly, the short-circuit inductance matrix element in the i-th row and j-th column, i.e., the short-circuit inductance L between the i-th and j-th sub-windings, is s-i,j The calculation process is:

[0090] ;

[0091] in, is the short-circuit inductance between the i-th and j-th sub-windings; is the reduced-order inductance matrix element of the i-th row and the i-th column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the j-th row and the j-th column in the reduced-order inductance matrix; is the reduced-order inductor matrix element in the i-th row and j-th column of the reduced-order inductor matrix.

[0092] Step S24: Use multiple short-circuit inductance matrix elements to construct a short-circuit inductance matrix.

[0093] It should be noted that all the short-circuit inductance matrix elements are used to construct the short-circuit inductance matrix, which can be expressed as:

[0094] ;

[0095] in, is the short-circuit inductance matrix; is the short-circuit inductance matrix element in the first row and second column of the short-circuit inductance matrix; is the short-circuit inductance matrix element in the 1st row and the nth column in the short-circuit inductance matrix; is the short-circuit inductance matrix element in the 2nd row and the 1st column of the short-circuit inductance matrix; is the short-circuit inductance matrix element in the 2nd row and the nth column in the short-circuit inductance matrix; is the short-circuit inductance matrix element in the nth row and the first column of the short-circuit inductance matrix; is the short-circuit inductance matrix element in the nth row and second column of the short-circuit inductance matrix.

[0096] Step 103: Determine a coupling leakage inductance matrix based on the inductance-related quantity matrix.

[0097] It should be noted that the main diagonal elements and non-main diagonal elements of the coupled leakage inductance matrix can be directly or indirectly calculated through the self-inductance mutual inductance matrix or the reduced-order inductance matrix or the short-circuit inductance matrix, and then the coupled leakage inductance matrix can be constructed based on the main diagonal elements and non-main diagonal elements of the coupled leakage inductance matrix.

[0098] Specifically, the process of determining the coupling leakage inductance matrix based on the inductance correlation matrix can be achieved by executing the following steps S31 to S33:

[0099] Step S31, determining a coupling leakage inductance matrix based on the self-inductance and mutual inductance matrix;

[0100] It should be noted that the key to constructing the transformer multi-scale circuit model and its fault analysis model is the core parameter identification, that is, the parameter identification of the coupled leakage inductance matrix.

[0101] Further, step S31 may include the following sub-steps S311-S312:

[0102] Step S311, determining a plurality of main diagonal elements of a coupled leakage inductance matrix and a plurality of off-diagonal elements of a coupled leakage inductance matrix based on a plurality of self-inductance and mutual-inductance matrix elements in a self-inductance and mutual-inductance matrix;

[0103] Step S312: construct a coupled leakage inductance matrix using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0104] Step S32, or determining a coupling leakage inductance matrix based on the reduced-order inductance matrix;

[0105] Further, step S32 may include the following sub-steps S321-S322:

[0106] Step S321, determining a plurality of main diagonal elements of a coupled leakage inductance matrix and a plurality of off-diagonal elements of a coupled leakage inductance matrix based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix;

[0107] Step S322: construct a coupled leakage inductance matrix using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0108] Step S33, or based on the short-circuit inductance matrix, determine the coupled leakage inductance matrix.

[0109] Further, step S33 may include the following sub-steps S331-S332:

[0110] Step S331, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements based on a plurality of short-circuit inductance matrix elements in the short-circuit inductance matrix;

[0111] Step S332: construct a coupled leakage inductance matrix using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0112] It should be noted that the magnetic coupling relationship between each sub-winding of the transformer can be represented by a group of mutually coupled inductors in series. Since the excitation impedance of each sub-winding port is much larger than the μH-level leakage inductance between the windings, and the mutual inductance between the leakage inductances is smaller, in order to simplify the model while ensuring the accuracy of the circuit model as much as possible, the excitation branch with little impact on the accuracy of the circuit simulation results is ignored, and only the influence of the core is considered when calculating the winding self-inductance-mutual inductance matrix (self-inductance mutual inductance matrix). Please refer to the following example. Figure 4 The transformer leakage inductance equivalent circuit shown is Figure 4 Medium:U i is the voltage drop caused by the i-th inductor; I i is the current flowing through the i-th inductor; L c-i,i is the self-inductance of the i-th inductor, indicating the leakage inductance between the i-th sub-winding and the i+1-th sub-winding; L c-i,j-1 is the mutual inductance between the i-th inductor and the j-1-th inductor (i, j-1=1, 2, 3......, n-1); the circuit model essentially uses the electromagnetic duality principle to represent the magnetic coupling characteristics of the sub-winding with an inductor circuit; where the voltage U between node i and node j i,j The calculation process can be expressed as:

[0113] ;

[0114] in, is the voltage between node i and node j; is the voltage drop produced by the kth inductor; is the coupled leakage inductance matrix element in the kth row and pth column, representing self-inductance or mutual inductance. When k=p, is the self-inductance of the kth inductor, indicating the leakage inductance between the kth sub-winding and the k+1th sub-winding. When k≠p, is the mutual inductance between the kth inductor and the pth inductor, indicating the correlation between the leakage inductances; is the current flowing through the pth inductor.

[0115] Furthermore, if an excitation is applied to node i and node j is short-circuited to the ground, in the short-circuit experiment between nodes i and j, only the inductor between nodes i and j has current flowing through it, and the corresponding expression is:

[0116] ;

[0117] in, is the current flowing through the i-th inductor; is the current flowing through the j-1th inductor; is the current flowing through the mth inductor; is the current flowing through the qth inductor; m is the node number between node i and node j; q is the node number other than the node between node i and node j.

[0118] Furthermore, the voltage U between node i and node j is i,j The calculation process of the inductor only includes the current between nodes i and j, and the corresponding expression is combined to obtain:

[0119] ;

[0120] in, is the voltage between node i and node j; is the coupled leakage inductance matrix element in the kth row and pth column, representing self-inductance or mutual inductance. When k=p, is the self-inductance of the kth inductor, indicating the leakage inductance between the kth sub-winding and the k+1th sub-winding. When k≠p, is the mutual inductance between the kth inductor and the pth inductor, indicating the correlation between the leakage inductances; is the excitation winding current.

[0121] Based on the above foundation, the short-circuit inductance between node i and node j can be expressed as:

[0122] ;

[0123] in, is the short-circuit inductance between node i and node j; is the voltage between node i and node j; is the excitation sub-winding current; is the coupled leakage inductance matrix element in the kth row and pth column, representing self-inductance or mutual inductance. When k=p, is the self-inductance of the kth inductor, indicating the leakage inductance between the kth sub-winding and the k+1th sub-winding. When k≠p, is the mutual inductance between the kth inductor and the pth inductor, indicating the correlation between the leakage inductances.

[0124] Furthermore, when j = i+1, the coupling leakage inductance matrix L cThe calculation process of the main diagonal elements in , that is, the process of determining the main diagonal elements of the multiple coupled leakage inductance matrices based on the multiple self-inductance and mutual inductance matrix elements in the self-inductance and mutual inductance matrix, or based on the multiple reduced-order inductance matrix elements in the reduced-order inductance matrix, or based on the multiple short-circuit inductance matrix elements in the short-circuit inductance matrix, can be expressed as:

[0125] ;

[0126] in, is the main diagonal element of the coupled leakage inductance matrix in the i-th row and i-th column, representing the self-inductance of the i-th inductor, that is, the leakage inductance between the i-th sub-winding and the i+1-th sub-winding; is the short-circuit inductance matrix element of the i-th row and the i+1-th column in the short-circuit inductance matrix; is the reduced-order inductance matrix element of the i-th row and the i-th column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the i+1th row and the i+1th column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the i-th row and the i+1-th column in the reduced-order inductance matrix; is the self-inductance-mutual inductance matrix element in the i-th row and i-th column of the self-inductance-mutual inductance matrix; is the self-inductance-mutual inductance matrix element in the i+1th row and i+1th column in the self-inductance-mutual inductance matrix; is the self-inductance-mutual-inductance matrix element in the i-th row and i+1-th column in the self-inductance-mutual-inductance matrix.

[0127] Furthermore, due to the coupled leakage inductance matrix L c The symmetry of , the calculation process of the non-diagonal elements in the matrix is ​​obtained, that is, the process of determining the non-diagonal elements of the multiple coupling leakage inductance matrices based on the multiple self-inductance and mutual inductance matrix elements in the self-inductance and mutual inductance matrix, or based on the multiple reduced-order inductance matrix elements in the reduced-order inductance matrix, or based on the multiple short-circuit inductance matrix elements in the short-circuit inductance matrix, can be expressed as:

[0128] ;

[0129] in, is the off-diagonal element of the coupled leakage inductance matrix in the i-th row and j-th column, representing the mutual inductance between the i-th inductor and the j-th inductor; is the off-diagonal element of the coupled leakage inductance matrix in the j-th row and the i-th column; is the coupled leakage inductance matrix element in the kth row and pth column, representing self-inductance or mutual inductance. When k=p, is the self-inductance of the kth inductor, indicating the leakage inductance between the kth sub-winding and the k+1th sub-winding. When k≠p, is the mutual inductance between the kth inductor and the pth inductor, indicating the correlation between the leakage inductances; is the short-circuit inductance matrix element in the i-th row and j+1-th column in the short-circuit inductance matrix; is the short-circuit inductance matrix element of the i+1th row and the jth column in the short-circuit inductance matrix; is the short-circuit inductance matrix element of the i-th row and j-th column in the short-circuit inductance matrix; is the short-circuit inductance matrix element of the i+1th row and j+1th column in the short-circuit inductance matrix; is the reduced-order inductance matrix element of the i-th row and j-th column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the i+1th row and the j+1th column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the i+1th row and the jth column in the reduced-order inductance matrix; is the reduced-order inductance matrix element of the i-th row and the j+1-th column in the reduced-order inductance matrix; is the self-inductance-mutual inductance matrix element in the i-th row and j-th column in the self-inductance-mutual inductance matrix; is the self-inductance-mutual inductance matrix element in the i+1th row and j+1th column in the self-inductance-mutual inductance matrix; is the self-inductance-mutual inductance matrix element in the i+1th row and jth column in the self-inductance-mutual inductance matrix; is the self-inductance-mutual-inductance matrix element in the i-th row and j+1-th column in the self-inductance-mutual-inductance matrix.

[0130] Based on the multiple main diagonal elements of the coupled leakage inductance matrix and the multiple off-diagonal elements of the coupled leakage inductance matrix obtained in the above steps, a coupled leakage inductance matrix is ​​constructed, thereby realizing direct or indirect conversion into a coupled leakage inductance matrix through a self-inductance / mutual inductance matrix or a reduced-order inductance matrix or a short-circuit inductance matrix, wherein the self-inductance-mutual inductance matrix can be quickly obtained through finite element simulation.

[0131] In this embodiment, for the parameter identification of the coupled leakage inductance matrix, the present invention discusses the parameter identification process of "self-inductance / mutual inductance matrix-reduced-order inductance matrix-short-circuit inductance matrix-coupled leakage inductance matrix", which can be replaced by directly or indirectly converting from any intermediate matrix to the final coupled leakage inductance matrix, such as directly calculating the short-circuit impedance matrix through on-site or finite element-based port short-circuit test, and then converting it into a coupled leakage inductance matrix. In addition, for the extraction of self-inductance and mutual inductance parameters, it is not necessary for the manufacturer to directly provide a finite element model, but only the manufacturer needs to provide a self-inductance and mutual inductance matrix, which can protect the manufacturer's trade secrets and facilitate engineering applications.

[0132] Step 104: construct a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding.

[0133] Please note that Figure 5 , the leakage inductance and mutual inductance representing the magnetic coupling relationship between each sub-winding are expressed as the coupled leakage inductance matrix L cCharacterize it, and encapsulate this part of the circuit to form module A. To facilitate calculation and external circuit connection, the elements in the coupled leakage inductance matrix are all reduced to the same number of turns. Therefore, it is necessary to insert an ideal transformer between each node and the common node of the equivalent circuit to realize the coupling of the internal magnetic characteristics and the external circuit, and at the same time represent the actual number of turns of each sub-winding. Then, the sub-winding resistance is connected to the ideal transformer, and then according to the electrical connection relationship of each sub-winding of the transformer, the high-voltage and low-voltage sub-windings are connected end to end, and each sub-winding terminal is brought out to realize the call of the internal nodes of the winding, which is convenient for subsequent fault wiring. Therefore, the established transformer multi-scale circuit model is as follows Figure 5 As shown (there is mutual inductance between any two inductors in module A, which is not shown in the figure), and an excitation power supply and a load are connected to facilitate model testing. Figure 5 Middle: R k Represents the resistance of each sub-winding, N k Indicates the number of turns of each sub-winding, U s Represents the power supply voltage, Z L Indicates the equivalent load on the low voltage side.

[0134] Further, using Figure 5 The circuit model shown is used for simulation; the model and its parameter identification method can be obtained without the need for port short-circuit tests, which solves the parameter identification problem of the existing multi-winding transformer model; at the same time, the model is a circuit model, the calculation efficiency is greatly improved, and it can be jointly simulated with an external circuit model, which solves the problems of low efficiency and poor circuit adaptability of the fault analysis model based on the field-circuit coupling method.

[0135] Step 105: Based on the electromagnetic connection relationship of the transformer and the physical process of the internal short circuit, multiple sub-winding terminals in the transformer multi-scale circuit model are connected to generate a transformer internal short circuit multi-scale fault analysis model.

[0136] It should be noted that, on the basis of the established multi-scale circuit model of the transformer, according to the electromagnetic connection relationship of the transformer and the physical process of the internal short circuit, the terminals of each sub-winding are connected, and the multi-scale fault analysis model of the transformer for different internal short circuit conditions such as turn-to-turn short circuit, developmental turn-to-turn short circuit, turn-to-ground short circuit, and winding-to-winding short circuit is obtained, that is, the multi-scale fault analysis model of the transformer internal short circuit; wherein, the electromagnetic connection relationship of the transformer and the physical process of the internal short circuit correspond to transformer-type equipment. For example, if the transformer is a single-phase transformer, based on the electromagnetic connection relationship and the physical process of the internal short circuit of the single-phase transformer, the terminals of each sub-winding are connected to obtain the multi-scale fault analysis model of the single-phase transformer internal short circuit.

[0137] It is worth mentioning that for the internal short-circuit fault condition, it can be any internal short-circuit fault of any transformer equipment, such as winding turn-to-turn short circuit, developmental turn-to-turn short circuit, turn-to-ground short circuit, winding short circuit, phase-to-phase short circuit, etc.

[0138] As a comparison of technical effects, it can be combined with existing technologies for reference. In recent years, it has been found that some accidents have developed internal short-circuit faults (i.e., the number of short-circuit turns increases rapidly in a short period of time), resulting in the proportion of the second harmonic of the fault differential current continuing to be greater than the setting value in DL / T684-2012 "Guidelines for Calculation of Relay Protection Setting for Large Generator Transformers" issued by the National Energy Administration, causing significant delays in protection exports, and the fault energy rises rapidly in a short period of time, causing major accidents such as explosions. Therefore, it is urgent to propose a transformer internal short-circuit fault analysis method to reveal the transient characteristics of the transformer fault current, fault energy, and their influence on protection, and provide basic support for the improvement of equipment manufacturing and relay protection performance.

[0139] Since the internal short-circuit test of the transformer is a destructive test and a real-type test cannot be carried out, transformer equipment manufacturing companies generally use the field-circuit coupling analysis method to simulate the fault to study the electromagnetic transient characteristics of the internal short-circuit fault of the transformer and support the transformer design verification and accident analysis. The field-circuit coupling method establishes a finite element model based on the physical size and material properties of the transformer, and sets the fault in the circuit according to the short-circuit type and location, which can better analyze the electromagnetic characteristics of the internal fault of the transformer. However, in transient calculation, this method needs to solve all grids in the solution area composed of the transformer and the surrounding field in each time step, and use the polynomial interpolation function of all vertex values ​​of each grid as the value of the physical quantity at any point in the grid; and the transformer has significant multi-scale characteristics. In actual short-circuit faults, coils of single turn, single cake, multi-cake and other scales may be involved at the same time. For example, the grid-side winding of the ±800kV converter transformer has hundreds of cakes and more than one thousand turns of coils, and there are many combinations of short-circuit conditions such as turn-to-turn, cake-to-cake, and turn-to-ground; therefore, for large-capacity transformers with complex internal structures, the field-circuit coupling analysis method consumes too much computing resources and takes too long to simulate, making it difficult to traverse and simulate all potential short-circuit conditions. More importantly, the field-circuit coupling simulation model of the transformer is difficult to jointly model with the external power grid, and the model has poor adaptability. For example, the internal short-circuit simulation of the converter transformer requires the converter transformer model to be coupled with the models of the converter valve, power supply, load, etc., which is difficult to achieve in finite element simulation software.

[0140] In order to improve the simulation efficiency and improve the compatibility of the model with the external power grid, a transformer circuit model can be established to carry out internal short-circuit fault analysis. Currently, the circuit models used for transformer internal short-circuit fault analysis mainly include the built-in model of electromagnetic transient simulation software, RLC model, grid circuit model, etc. The transformer model built into the electromagnetic transient simulation software has a small number of open ports. For example, there are only three winding models in EMTP-RV and four winding models in PSCAD. In addition, the component integration and packaging are high, and only a very small number of specific short-circuit conditions can be simulated. At the same time, the model parameters need to be reset for different short-circuit conditions, making it difficult to simulate the development process of complex short circuits. The multi-winding transformer module in MATLAB can only lead out the middle node of a single winding, and the taps are equidistantly distributed, and the winding resistance and leakage inductance are evenly distributed along the taps. The multi-winding transformer model in EMTP-RV is an ideal transformer, which can only reflect the winding ratio, but cannot characterize the coupling relationship between windings. In order to expand the number of ports to achieve multi-segmentation of the winding and call the internal nodes of the winding, multi-scale modeling can be achieved through a series transformer model, but the magnetic coupling relationship between the winding segments is still difficult to accurately characterize. The RLC model is a multi-stage network circuit. Usually, each stage is composed of the self-resistance, self-inductance, dielectric conductance, mutual inductance between windings, equivalent longitudinal capacitance, capacitance to ground and other parameters of the winding at that stage. Some parameters can be appropriately ignored to simplify the model according to different application scenarios. The models currently used for transformer internal short-circuit fault analysis in the RLC model mainly include the multi-conductor transmission line (MLT) model, the ladder network model (detailed model), and the leakage inductance factor model. Among them, the multi-conductor transmission line model is a distributed parameter model based on winding turn modeling, while the ladder network model is a lumped parameter model for pancake winding modeling. The multi-conductor transmission line model approximates each turn of the transformer winding as a transmission line, and the entire winding is simulated into multiple multi-conductor transmission lines that are mutually coupled and connected end to end. The model is implemented by programming or in electromagnetic transient software based on the frequency domain equation using the resistance, inductance, conductance, and capacitance matrix per unit length of the transformer. The ladder network model calculates the parameters of each pancake of the transformer through analytical formulas or electrostatic field and static magnetic field modules based on the finite element model, and connects them in series to form a multi-stage mutually coupled ladder network. The above two models are currently mostly used to study the high-frequency behaviors of transformers such as the traveling wave characteristics and frequency response characteristics of pulse input. Therefore, the influence of the core is usually ignored when solving the parameters, and the equivalent is an air-core coil.The transformer internal short-circuit fault model constructed based on the leakage inductance factor method takes the N-order resistance matrix R and inductance matrix L of the N-winding transformer before the fault as the original data, calculates the fault winding inductance by calculating the leakage inductance factor to solve the equation group, and obtains the R and L matrices after the fault, and then establishes the model according to the transient calculation equation of the voltage and current of the multi-winding transformer port; but it is necessary to recalculate the matrix according to the short-circuit type and short-circuit position, and the parameter solution is based on the estimation or calculation process. It is currently mainly used to analyze single turn-to-turn short-circuit faults or static short-circuit faults. The RLC model can usually omit the capacitance and resistance parameters that have little impact on the simulation accuracy in the transformer power frequency internal short-circuit calculation, that is, the model based on the winding self-inductance and mutual inductance matrix; but for the windings divided by equal size, the inductance matrix elements are close, and the accuracy of the parameter calculation results is required to be high, which may cause the matrix determinant to be 0. In transient simulation, the impedance matrix cannot be inverted in the time domain solution and cannot be run. Some scholars, based on the calculation of the post-fault parameter matrix using the leakage inductance factor method, transformed the port equation of the transformer based on the self-inductance and mutual inductance matrix into only two parts, fault and non-fault, and derived and calculated the equivalent circuit parameters, but this method still needs to re-derive and calculate the circuit parameters according to different short-circuit conditions. Some scholars also obtained a topology-based transformer turn-to-turn fault circuit model based on the duality principle through the magnetic circuit when the transformer turns to fault, but this method is not suitable for simulating turn-to-turn faults on the excitation side when the excitation is an ideal source. Other scholars proposed a new grid transformer modeling method to make the circuit-based model as similar to the finite element as possible to achieve accurate modeling of the transformer, but the calculation accuracy is still positively correlated with the complexity of the model. Therefore, the circuit models currently used for transformer internal short-circuit fault analysis all have the problem of difficulty in characterizing the multi-scale coupling of the windings, and are difficult to apply to the analysis of transformer internal short-circuit fault processes with multiple scales and multiple working conditions.

[0141] Among the existing transformer circuit models, the negative inductance model, BCTRAN model and TDM model (terminal-duality model) can characterize the magnetic coupling relationship between multiple windings and have the ability to be applied to internal short-circuit fault analysis. The negative inductance model uses a star-connected inductor to represent the leakage inductance between windings, but the equivalent leakage inductance of the middle winding of the concentric structure is usually negative, which has no physical meaning, and may cause simulation instability and divergence problems; and for transformers with more than three windings or transformers with different winding heights, there may be large errors, and it is mainly used to study the steady-state characteristics of three-winding transformers. The BCTRAN model uses a matrix to characterize the magnetic coupling relationship between transformer windings. It has high engineering simulation accuracy below 1kHz and excellent scalability for multi-winding transformers. Matrix elements are usually calculated using design formulas or short-circuit test results based on the finite element method and experimental method. However, since the design formula is only applicable to the case where the winding magnetic field is vertically linked, the parameter calculation error is large for windings that are far apart. The parameter solution method based on port short-circuit test is suitable for multi-winding transformers; however, if the winding is regarded as a cascade of multiple sub-windings, there is no tap inside the actual transformer winding, and port testing cannot be performed. Even if finite element simulation is used instead of testing, for small-scale models of transformer pancake level or even turn level, there are many permutations and combinations of short-circuit tests between windings. For a single-phase N-winding transformer, at least N(N-1) / 2 tests are required, which is extremely labor-intensive and computationally intensive, and it is difficult to obtain model matrix parameters. The TDM model unifies the port model and the electromagnetic dual model, and has the ability to characterize internal magnetic coupling, but it has the same parameter identification problem as the BCTRAN model.

[0142] Therefore, the existing transformer equipment internal short-circuit fault analysis model has the following shortcomings: (1) The field-circuit coupling method is based on the finite element model, but it consumes too much computing resources and takes too long to simulate, making it difficult to traverse and simulate all potential short-circuit conditions. It is also difficult to jointly model with the external power grid, and the model has poor adaptability. (2) The circuit model currently used for transformer turn-to-turn short-circuit fault analysis is difficult to apply to the analysis of multi-scale and multi-conditions due to problems such as multi-scale coupling representation of windings, inability to invert the impedance matrix, difficulty in parameter identification, limited applicable fault range, and complex model structure. (3) The existing multi-winding transformer circuit models all have the problem of difficult parameter identification. The design formula is only applicable to the case of vertical cross-linking of the winding magnetic field. Therefore, the parameter calculation error is large for windings that are far apart. In addition, there are no taps inside the actual transformer windings, and it is impossible to perform a port short-circuit test to solve the parameters. Even if finite element simulation is used instead of the test, for small-scale models of the transformer pancake level or even turn level, there are many combinations of short-circuit tests between windings, and the workload and calculation are extremely large, making it difficult to obtain the model parameters.

[0143] In summary, since the internal short-circuit test of the transformer is a destructive test, it is impossible to carry out a true-type test; the fault analysis model based on the field-circuit coupling method has the problems of low efficiency and poor circuit adaptability; the existing transformer circuit models are difficult to use to analyze the transient characteristics of electrical quantities of multi-scale and multi-condition internal short-circuit faults because they all have problems such as multi-scale coupling characterization of windings and difficulty in parameter identification.

[0144] In view of the above problems, the present invention proposes a method for constructing a multi-scale fault analysis model for internal short circuit of transformer, through the process of converting the self-inductance-mutual inductance matrix into a coupled leakage inductance matrix, wherein the self-inductance-mutual inductance matrix is ​​quickly obtained through finite element simulation, and the representation of the electromagnetic coupling relationship between the windings at multiple scales and multiple segments and the rapid identification of the model parameters are realized, without the need to carry out a large number of port tests, which reduces the workload of parameter identification. At the same time, the present invention proposes a transformer equipment circuit model suitable for multi-scale and multi-condition internal short circuit fault analysis, which can be used to simulate and analyze different internal short circuit conditions of transformer equipment, significantly improving the calculation efficiency and simulation efficiency, facilitating joint modeling with the external power grid, solving the problems of low efficiency and poor circuit adaptability, and having good circuit adaptability. In addition, the present invention uses a group of mutually coupled inductors in series to represent the coupling relationship between windings, wherein the self-inductance represents the leakage inductance between adjacent windings in the circuit, and the mutual inductance represents the correlation between the leakage inductances, solving the problem of difficulty in circuit representation of the electromagnetic coupling relationship of multi-scale and multi-segment windings.

[0145] In an embodiment of the present invention, the present invention provides a method for constructing a multi-scale fault analysis model for internal short circuit of a transformer. When it is necessary to construct a multi-scale fault analysis model for internal short circuit of a transformer, the transformer is first disassembled to determine multiple sub-windings; then, parameter identification is performed according to a transformer finite element model corresponding to the transformer using a parameter scanning method and Kirchhoff's current law to determine a resistance matrix and an inductance-related quantity matrix; based on the inductance-related quantity matrix, a coupling leakage inductance matrix is ​​determined; a transformer multi-scale circuit model is constructed according to the resistance matrix, the coupling leakage inductance matrix and the number of turns of each sub-winding; finally, based on the electromagnetic connection relationship of the transformer and the internal short circuit physical process, multiple sub-winding terminals in the transformer multi-scale circuit model are connected to generate a transformer internal short circuit multi-scale fault analysis model; based on the above scheme, a resistance matrix and a coupling leakage inductance matrix are obtained according to the transformer finite element model corresponding to the transformer using a parameter scanning method and Kirchhoff's current law, and the transformer internal short circuit multi-scale fault analysis model generated by combining the electromagnetic connection relationship of the transformer and the internal short circuit physical process can be used to simulate and analyze different internal short circuit conditions of transformer equipment, facilitate joint modeling with an external power grid, thereby improving the adaptability of the model circuit.

[0146] See also Figure 6 , Figure 6This is a structural block diagram of a device for constructing a multi-scale fault analysis model for internal short circuit of a transformer provided in Embodiment 2 of the present invention.

[0147] The present invention provides a device for constructing a transformer internal short circuit multi-scale fault analysis model, comprising:

[0148] A response module 601 is used to respond to the construction request, disassemble the transformer, and determine multiple sub-windings;

[0149] A parameter identification module 602 is used to perform parameter identification according to a transformer finite element model corresponding to the transformer by using a parameter scanning method and Kirchhoff's current law to determine a resistance matrix and an inductance related quantity matrix;

[0150] A coupled leakage inductance matrix determination module 603 is used to determine a coupled leakage inductance matrix based on an inductance related quantity matrix;

[0151] A construction module 604 is used to construct a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding;

[0152] The generation module 605 is used to connect multiple sub-winding terminals in the transformer multi-scale circuit model based on the electromagnetic connection relationship of the transformer and the internal short-circuit physical process, and generate a transformer internal short-circuit multi-scale fault analysis model.

[0153] Furthermore, the inductance related quantity matrix includes a self-inductance mutual inductance matrix, a reduced-order inductance matrix and a short-circuit inductance matrix; the parameter identification module 602 is specifically used for:

[0154] Based on the parameter scanning method, the transformer finite element model corresponding to the transformer is subjected to parametric scanning calculation to determine the resistance matrix and the self-inductance and mutual inductance matrix;

[0155] Kirchhoff's current law is used to determine the reduced-order inductance matrix according to the voltage drop equation caused by the inductance part corresponding to the self-inductance and mutual-inductance matrix;

[0156] Determining a plurality of short-circuit inductance matrix elements based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix;

[0157] A short-circuit inductance matrix is ​​constructed by using a plurality of short-circuit inductance matrix elements.

[0158] Further, determining the coupled leakage inductance matrix module 603 includes:

[0159] The first construction submodule is used to determine the coupling leakage inductance matrix based on the self-inductance and mutual inductance matrix;

[0160] A second construction submodule is used to determine a coupled leakage inductance matrix based on the reduced-order inductance matrix;

[0161] The third building submodule is used to determine the coupled leakage inductance matrix based on the short-circuit inductance matrix.

[0162] Furthermore, the first construction submodule is specifically used for:

[0163] Based on a plurality of self-inductance and mutual-inductance matrix elements in the self-inductance and mutual-inductance matrix, a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements are determined;

[0164] A coupled leakage inductance matrix is ​​constructed by using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0165] Furthermore, the second construction submodule is specifically used for:

[0166] Based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements;

[0167] A coupled leakage inductance matrix is ​​constructed by using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0168] Furthermore, the third construction submodule is specifically used for:

[0169] Based on a plurality of short-circuit inductance matrix elements in the short-circuit inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements;

[0170] A coupled leakage inductance matrix is ​​constructed by using a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements.

[0171] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described devices, modules and sub-modules can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0172] An embodiment of the present invention also provides a computer device, including a memory and a processor, wherein a computer program is stored in the memory; when the computer program is executed by the processor, the processor executes the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in the first embodiment above.

[0173] An embodiment of the present invention further provides a computer-readable storage medium on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in the first embodiment above are implemented.

[0174] An embodiment of the present invention further provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in the first embodiment above.

[0175] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0176] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0177] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a multi-scale fault analysis model for internal short circuit of a transformer, characterized in that: include: In response to a build request, the transformer is disassembled to identify a plurality of sub-windings; Using parameter scanning method and Kirchhoff's current law to perform parameter identification according to the transformer finite element model corresponding to the transformer, and determine the resistance matrix and the inductance related quantity matrix; Determining a coupled leakage inductance matrix based on the inductance-related quantity matrix; Constructing a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding; Based on the electromagnetic connection relationship and the internal short-circuit physical process of the transformer, multiple sub-winding terminals in the transformer multi-scale circuit model are connected to generate a transformer internal short-circuit multi-scale fault analysis model.

2. The method for constructing a transformer internal short circuit multi-scale fault analysis model according to claim 1, characterized in that: The inductance related quantity matrix includes a self-inductance mutual inductance matrix, a reduced-order inductance matrix and a short-circuit inductance matrix; The method of using the parameter scanning method and Kirchhoff's current law to perform parameter identification according to the transformer finite element model corresponding to the transformer to determine the resistance matrix and the inductance related quantity matrix includes: Based on the parameter scanning method, a parameter scanning calculation is performed on the transformer finite element model corresponding to the transformer to determine the resistance matrix and the self-inductance and mutual inductance matrix; Determine a reduced-order inductance matrix using Kirchhoff's current law according to a voltage drop equation caused by the inductance part corresponding to the self-inductance and mutual-inductance matrix; Determining a plurality of short-circuit inductance matrix elements based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix; A short-circuit inductance matrix is ​​constructed by using a plurality of the short-circuit inductance matrix elements.

3. The method for constructing a transformer internal short circuit multi-scale fault analysis model according to claim 2, characterized in that: The step of determining a coupled leakage inductance matrix based on the inductance-related quantity matrix includes: Based on the self-inductance and mutual-inductance matrix, determining a coupled leakage inductance matrix; or determining a coupled leakage inductance matrix based on the reduced-order inductance matrix; Or based on the short-circuit inductance matrix, a coupled leakage inductance matrix is ​​determined.

4. The method for constructing a transformer internal short circuit multi-scale fault analysis model according to claim 3, characterized in that: The determining of the coupling leakage inductance matrix based on the self-inductance and mutual inductance matrix includes: Based on a plurality of self-inductance and mutual-inductance matrix elements in the self-inductance and mutual-inductance matrix, determining a plurality of coupling leakage inductance matrix main diagonal elements and a plurality of coupling leakage inductance matrix off-diagonal elements; A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

5. The method for constructing a transformer internal short circuit multi-scale fault analysis model according to claim 3, characterized in that: The step of determining a coupled leakage inductance matrix based on the reduced-order inductance matrix includes: Based on a plurality of reduced-order inductance matrix elements in the reduced-order inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements; A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

6. The method for constructing a transformer internal short circuit multi-scale fault analysis model according to claim 3, characterized in that: The determining of the coupled leakage inductance matrix based on the short-circuit inductance matrix includes: Based on a plurality of short-circuit inductance matrix elements in the short-circuit inductance matrix, determining a plurality of coupled leakage inductance matrix main diagonal elements and a plurality of coupled leakage inductance matrix off-diagonal elements; A coupled leakage inductance matrix is ​​constructed by using a plurality of main diagonal elements of the coupled leakage inductance matrix and a plurality of off-diagonal elements of the coupled leakage inductance matrix.

7. A device for constructing a multi-scale fault analysis model for internal short circuit of a transformer, characterized in that: include: A response module, used for responding to the construction request, disassembling the transformer, and determining a plurality of sub-windings; A parameter identification module, used to perform parameter identification according to a transformer finite element model corresponding to the transformer by using a parameter scanning method and Kirchhoff's current law, and determine a resistance matrix and an inductance related quantity matrix; A coupled leakage inductance matrix determination module is used to determine a coupled leakage inductance matrix based on the inductance-related quantity matrix; A construction module, used to construct a transformer multi-scale circuit model according to the resistance matrix, the coupled leakage inductance matrix and the number of turns of each sub-winding; A generation module is used to connect multiple sub-winding terminals in the transformer multi-scale circuit model based on the transformer electromagnetic connection relationship and the internal short-circuit physical process to generate a transformer internal short-circuit multi-scale fault analysis model.

8. A computer device, characterized in that: It comprises a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the method for constructing a transformer internal short-circuit multi-scale fault analysis model as described in any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer executes the method for constructing a multi-scale fault analysis model for internal short circuit of a transformer as described in any one of claims 1 to 6.

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