1. A converter transformer electric field digital twin model construction method is characterized by comprising the following steps:

constructing a full-size main insulation model of the converter transformer, and simplifying the insulating paper boards and the adjacent oil gaps based on the electric field invariance principle to form a simplified main insulation model;

applying three excitations of alternating voltage, direct current voltage and polarity reversal voltage to a valve side winding of the main insulation simplified model respectively, and solving a main insulation electric field correspondingly to obtain main insulation electric field distribution under the three excitations;

extracting three modes of main insulation electric field distribution under excitation based on an intrinsic orthogonal decomposition method, and constructing a main insulation electric field calculation reduced order model;

and verifying the main insulation electric field calculation order-reduced model, if the verification is passed, taking the main insulation electric field calculation order-reduced model as an electric field digital twin model, and if the verification is not passed, re-extracting three excited main insulation electric field distribution modes to re-construct the main insulation electric field calculation order-reduced model until the verification is passed.

2. The method for constructing the digital twin model of the converter transformer electric field according to claim 1, wherein the simplification of the insulating paper board and the adjacent oil gaps based on the principle of electric field invariance comprises the following steps:

the insulating paper boards and the oil gaps are widened by 1 time respectively, and after the same voltage is applied, the field intensity born by the widened insulating paper boards and the oil gaps is the same as that of the main insulating full-size model.

3. The method for constructing the digital twin model of the converter transformer electric field according to claim 1, wherein the alternating voltage is:

in the formula of U_dmThe highest direct current voltage of each valve bridge; n is the number of six pulse bridges connected in series from a neutral point of a direct current circuit to a rectifier bridge connected with a transformer; u shape_vmThe maximum phase voltage of a converter transformer valve side winding is obtained;

the direct-current voltage is as follows:

U_dc＝1.5[(N-0.5)U_dm+0.7U_pr] (2)

in the formula of U_prThe maximum alternate alternating current working voltage of the valve side winding is obtained;

the polarity inversion voltage is:

U_pr＝1.25[(N-0.5)U_dm+0.35U_vm] (3)

when the polarity inversion voltage is applied, the positive polarity voltage 5400s is applied for 60s, the negative polarity voltage 5400s is further applied, and polarity inversion is completed by 60 s.

4. The method for constructing a digital twin model of a converter transformer electric field according to claim 1, wherein the method for constructing a main insulation electric field calculation reduced model by extracting the distribution mode of the main insulation electric field under three types of excitation based on an intrinsic orthogonal decomposition method comprises the following steps:

selecting field threshold potentials of S time nodes as sample data according to main insulated electric field distribution under three excitations to obtain a sample set { Ψ₁,Ψ₂,.....,Ψ_sWhere the vector Ψ_iColumn vector composed of field node potentials at ith delta tn is the number of nodes after field subdivision;

let a set of orthonormal bases of sample data be { ξ₁,ξ₂,.....,ξ_sAnd then the field potential at any point in space can be expressed as:intercepting the first d items of the data, wherein the following items are:the minimum error before and after interception is taken as a target function, and the standard orthogonal basis is obtained according to the following formula

And reconstructing the field potential by using the standard orthogonal basis, and substituting the reconstructed field potential into a finite element discrete algebraic equation for solving the potential.

5. The method for constructing a digital twin model of a converter transformer electric field according to claim 1, wherein the method for constructing a main insulation electric field calculation reduced model by extracting the distribution mode of the main insulation electric field under three types of excitation based on an intrinsic orthogonal decomposition method comprises the following steps:

selecting field threshold potentials of a plurality of time nodes as sample data according to the distribution of main insulated electric fields under three types of excitation, obtaining a sample set, and integrating the sample set into a sample matrix;

sorting column vectors of a left singular value matrix of a sample matrix from large to small, and intercepting a preset number of characteristic values to form a standard orthogonal base of a sample set;

and reconstructing the field potential by using the standard orthogonal basis, and substituting the reconstructed field potential into a finite element discrete algebraic equation for solving the potential.

6. The method for constructing the digital twin model of the converter transformer electric field according to claim 1, wherein the verifying the calculation order reduction model of the main insulation electric field comprises:

and applying the actually measured valve side voltage to the main insulation electric field calculation order-reduction model, and verifying the model to be passed when the calculation time and the calculation error both meet the preset requirements.

7. The method of constructing a digital twin model of a converter transformer electric field according to claim 6, wherein the predetermined requirements corresponding to the calculation time are: calculating the distribution of a main insulation electric field within second-level time; the predetermined requirements corresponding to the calculation error are: the comparison error between the calculation result of the main insulation electric field calculation order-reducing model and the actual measurement result is less than 5%.

8. The method for constructing a digital twinning model of a converter transformer electric field according to claim 1, wherein the main insulation full-size model comprises a net side winding, a valve side winding, a tap winding, an electrostatic ring, an insulating paper board, an insulating oil gap, transverse and longitudinal oil ducts, an oil baffle and an iron core.

Background

The digital twin technology reduces the time of product design and manufacture and system planning through self-learning, rapid iteration and evolution based on products, realizes continuous optimization of product performance, and is also a core technology for enterprise product digital transformation. At present, the digital twins are successfully applied in the fields of aerospace, smart cities, medical treatment and the like, and the digital twins technology is rapidly developed in the industry. The digital twins are one of key technologies for intellectualization and digital transformation of the electric power equipment, and the digital twins in the field of the electric power equipment can serve for optimal design and predictive maintenance of high-price electric power equipment, so that the digital twins have important value. Direct current transmission is a key technical means for optimizing energy configuration in China, and a converter transformer is core equipment of direct current transmission. Different from a common transformer, the converter transformer has higher voltage level and worse working environment, and a valve side winding of the converter transformer not only bears mixed voltage of alternating current and direct current superposition, but also bears a large amount of harmonic voltage. The insulation fault caused by the electric field is obviously higher than that of the traditional alternating current transformer, and the electric field of the converter transformer is difficult to be directly monitored on site, so that the method has great significance for constructing a digital twin model of the converter transformer electric field and accurately mastering the distribution of the main insulation electric field of the converter transformer in real time.

Disclosure of Invention

The invention aims to: aiming at the existing problems, a converter transformer electric field digital twin model construction method is provided to construct an electric field calculation model with high calculation efficiency.

The technical scheme adopted by the invention is as follows:

a method for constructing a digital twin model of a converter transformer electric field comprises the following steps:

constructing a full-size main insulation model of the converter transformer, and simplifying the insulating paper boards and the adjacent oil gaps based on the electric field invariance principle to form a simplified main insulation model;

applying three excitations of alternating voltage, direct current voltage and polarity reversal voltage to a valve side winding of the main insulation simplified model respectively, and solving a main insulation electric field correspondingly to obtain main insulation electric field distribution under the three excitations;

extracting three modes of main insulation electric field distribution under excitation based on an intrinsic orthogonal decomposition method, and constructing a main insulation electric field calculation order-reduction model;

and verifying the main insulation electric field calculation order-reduced model, if the main insulation electric field calculation order-reduced model passes the verification, taking the main insulation electric field calculation order-reduced model as an electric field digital twin model, and if the main insulation electric field calculation order-reduced model does not pass the verification, re-extracting the distribution modes of the main insulation electric field under excitation to re-construct the main insulation electric field calculation order-reduced model until the main insulation electric field calculation order-reduced model passes the verification.

Further, the simplification of the insulating paper board and the adjacent oil gaps based on the principle of electric field invariance includes:

the insulating paper boards and the oil gaps are widened by 1 time respectively, and after the same voltage is applied, the field intensity born by the widened insulating paper boards and the oil gaps is the same as that of the main insulating full-size model.

Further, the alternating voltage is:

in the formula of U_dmThe highest direct current voltage of each valve bridge; n is the number of six pulse bridges connected in series from a neutral point of a direct current circuit to a rectifier bridge connected with a transformer; u shape_vmThe maximum phase voltage of a valve side winding of the converter transformer is obtained;

the direct-current voltage is as follows:

U_dc＝1.5[(N-0.5)U_dm+0.7U_pr] (2)

in the formula of U_prThe maximum alternate alternating current working voltage of the valve side winding is obtained;

the polarity inversion voltage is:

U_pr＝1.25[(N-0.5)U_dm+0.35U_vm] (3)

when the polarity inversion voltage is applied, the positive polarity voltage 5400s is applied for 60s, the negative polarity voltage 5400s is further applied, and polarity inversion is completed by 60 s.

Further, the method for extracting the distribution mode of the main insulation electric field under three types of excitation based on the intrinsic orthogonal decomposition method and constructing the main insulation electric field calculation order reduction model comprises the following steps:

selecting field threshold potentials of S time nodes as sample data according to main insulated electric field distribution under three excitations to obtain a sample set { Ψ₁,Ψ₂,.....,Ψ_sWhere the vector Ψ_iColumn vector composed of field node potentials for ith time atn is the number of nodes after field subdivision;

let a set of orthonormal bases of sample data be { ξ₁,ξ₂,.....,ξ_sAnd then the field potential at any point in space can be expressed as:intercepting the first d items of the data, wherein the following items are:the minimum error before and after interception is taken as a target function, and the standard orthogonal basis is obtained according to the following formula

And reconstructing the field potential by the orthonormal basis, and substituting the reconstructed field potential into a finite element discrete algebraic equation for solving the potential.

Further, the method for extracting the distribution mode of the main insulation electric field under three types of excitation based on the intrinsic orthogonal decomposition method and constructing the main insulation electric field calculation order reduction model comprises the following steps:

selecting field threshold potentials of a plurality of time nodes as sample data according to the distribution of main insulated electric fields under three types of excitation to obtain a sample set, and integrating the sample set into a sample matrix;

sorting column vectors of a left singular value matrix of a sample matrix from large to small, and intercepting a preset number of characteristic values to form a standard orthogonal base of a sample set;

and reconstructing the field potential by the orthonormal basis, and substituting the reconstructed field potential into a finite element discrete algebraic equation for solving the potential.

Further, the verifying the main insulation electric field calculation order reduction model includes:

and applying the actually measured valve side voltage to the main insulation electric field calculation order-reduction model, and verifying the model to be passed when the calculation time and the calculation error both meet the preset requirements.

Further, the predetermined requirements corresponding to the calculated time are: calculating the distribution of the main insulating electric field within second-level time; the predetermined requirements corresponding to the calculation error are: the comparison error between the calculation result of the main insulation electric field calculation order-reducing model and the actual measurement result is less than 5%.

Furthermore, the main insulation full-size model comprises a net side winding, a valve side winding, a tapping winding, an electrostatic ring, an insulation paper board, an insulation oil gap, transverse and longitudinal oil ducts, an oil baffle plate and an iron core.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. the invention utilizes the principle of keeping the electric field unchanged to carry out equivalence on the insulating paper board and the oil gap of the main insulating full-size model, thereby obviously reducing the grids during calculation and improving the calculation efficiency.

2. According to the method, after the alternating voltage, the direct voltage and the polarity inversion voltage are applied to the valve side winding of the converter transformer respectively to calculate the electric field distribution, the transient image extraction required by the intrinsic orthogonal decomposition algorithm is carried out, the comprehensiveness of the extracted mode is improved, and the problem that the extracted mode cannot represent all information of field distribution when model reduction is carried out based on the intrinsic orthogonal decomposition algorithm at present is solved.

3. The invention designs a verification link, gives out a criterion for considering whether the reduced-order model can be used as an electric field digital twin model from two directions of calculation timeliness and calculation precision, and can ensure the calculation timeliness and the calculation precision of the final generated model.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a flow chart of a converter transformer electric field digital twinning model construction method.

Fig. 2 is a schematic diagram of a simplified electric field model of the insulating paper board and the adjacent oil gaps based on a field strength equivalence method.

FIG. 3 is another embodiment of a converter transformer electric field digital twinning model construction method.

Detailed Description

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations where mutually exclusive features and/or steps are present.

Any feature disclosed in this specification (including any accompanying claims, abstract) may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.

Example one

The embodiment discloses a method for constructing a digital twin model of a converter transformer electric field, as shown in fig. 1, the method includes:

A. and constructing a full-size main insulation model of the converter transformer, and simplifying the insulating paper boards and the adjacent oil gaps based on the electric field invariance principle to form a simplified main insulation model.

The converter transformer main insulation full-size model comprises a net side winding, a valve side winding, a tapping winding, an electrostatic ring, an insulating paper board, an insulating oil gap, transverse and longitudinal oil ducts, an oil baffle plate and an iron core.

In some embodiments, as shown in fig. 2, the method of "simplifying the insulating paper board and the adjacent oil gaps based on the principle of constant electric field" includes: the insulating paper boards and the oil gaps are widened by 1 time respectively, and after the same voltage is applied, the field intensity born by the widened insulating paper boards and the oil gaps is the same as that of the main insulating full-size model.

B. And applying three excitations of alternating voltage, direct current voltage and polarity reversal voltage to a valve side winding of the main insulation simplified model respectively, and solving a main insulation electric field correspondingly to obtain main insulation electric field distribution under the three excitations.

In some embodiments, the applied ac voltage is:

in the formula of U_dmThe highest direct current voltage of each valve bridge; n is the number of six pulse bridges connected in series from a neutral point of a direct current circuit to a rectifier bridge connected with a transformer; u shape_vmThe maximum phase voltage of a valve side winding of the converter transformer is obtained;

the applied dc voltage is:

U_dc＝1.5[(N-0.5)U_dm+0.7U_pr] (2)

in the formula of U_prThe maximum alternate alternating current working voltage of the valve side winding is obtained;

the polarity inversion voltage applied is:

U_pr＝1.25[(N-0.5)U_dm+0.35U_vm] (3)

when the polarity inversion voltage is applied, the positive polarity voltage 5400s is applied for 60s, the negative polarity voltage 5400s is further applied, and polarity inversion is completed by 60 s.

C. And extracting the distribution modes of the main insulation electric field under three types of excitation based on an intrinsic orthogonal decomposition method, and constructing a main insulation electric field calculation order reduction model.

D. And verifying the main insulation electric field calculation reduced model, if the main insulation electric field calculation reduced model passes the verification, taking the main insulation electric field calculation reduced model as an electric field digital twin model, and if the main insulation electric field calculation reduced model does not pass the verification, re-extracting three excited modes of main insulation electric field distribution to re-construct the main insulation electric field calculation reduced model until the main insulation electric field calculation reduced model passes the verification.

In some embodiments, as shown in fig. 3, the verifying the main insulation electric field calculation reduced order model includes: and applying actually measured valve side voltage to the main insulation electric field calculation order-reduction model, and verifying to pass when the calculation time and the calculation error both meet the preset requirements. For verification of the main insulation electric field calculation order reduction model, in some embodiments, the timeliness and the calculation accuracy are considered in combination, and the predetermined requirements corresponding to the calculation time are as follows: calculating the distribution of a main insulation electric field within second-level time; the predetermined requirements corresponding to the calculation error are: the comparison error between the calculation result of the main insulation electric field calculation order-reducing model and the actual measurement result is less than 5%.

Example two

The embodiment discloses a method for implementing the step C in the first embodiment.

Selecting field threshold potentials of S time nodes as sample data according to main insulated electric field distribution under three excitations to obtain a sample set { Ψ₁,Ψ₂,.....,Ψ_sWhere the vector Ψ_iColumn vector composed of field node potentials for ith time atn is the number of nodes after field subdivision;

let a set of orthonormal bases of sample data be { ξ₁,ξ₂,.....,ξ_sAnd then the field potential at any point in space can be expressed as:intercepting the first d items of the data, wherein the following items are:the minimum error before and after interception is taken as a target function, and the standard orthogonal basis is obtained according to the following formula

And reconstructing the field potential by the orthonormal basis, and substituting the reconstructed field potential into a finite element discrete algebraic equation for solving the potential.

EXAMPLE III

This embodiment provides a method for solving the standard orthogonal basis in the second embodiment.

In this embodiment, the extreme value problem in equation (4) is converted into the following eigenvalue problem:

Aξ＝λξ (5)

wherein A is YY^T∈R^n×n；Y＝[Ψ₁,Ψ₂,.....,Ψ_s]∈R^n×sIs a sample matrix assembled by samples.

The matrix of samples is subjected to a singular value decomposition,

Y＝U∑_σV^T (6)

is provided with

Wherein U is [ U ]₁,u₂,.....,u_n]∈R^n×n，V＝[v₁,v₂,.....,v_n]∈R^s×s

Based on the formula (7), it can be seen that the orthonormal base to be obtained is YY^TI.e. the column vectors of the left singular value matrix U of the sample matrix.

Therefore, the column vectors of the left singular value matrix U of the sample matrix are sorted from large to small, and the feature values of a predetermined number d (d is a positive integer) are truncated to form an orthonormal basis of the sample set:

ξ_i＝u_i(i＝1、2、...d) (8)

that is, for the solution of the orthonormal basis, the column vectors of the left singular value matrix of the sample matrix may be directly sorted from large to small, and a predetermined number of eigenvalues before being truncated form the orthonormal basis of the sample set.

Further, the reconstructing the field potential by the orthonormal basis includes:

based on the intercepted orthogonal base P ═ xi₁,ξ₂,...,ξ_d]∈R^n×dReconstructing the field potential to obtain:

then the standard orthogonal base based on the truncation is as follows:

the truncation error after reconstruction of the sample data (i.e., reconstruction of the field potential) is:

the error needs to be controlled within 5%.

Further, willSubstituting psi into finite element discrete algebraic equation of solution potential to obtain reduced solution potential finite element discrete algebraic equation, changing original solution potential finite element discrete algebraic equation from n order to d order, and d < n to complete model reduction.

Example four

The embodiment discloses a method for implementing the step C in the first embodiment.

Selecting field threshold potentials of S time nodes as sample data according to main insulated electric field distribution under three excitations to obtain a sample set { Ψ₁,Ψ₂,.....,Ψ_sWhere the vector Ψ_iColumn vector composed of field node potentials for ith time atAnd n is the number of nodes after field subdivision. Sample set-to-sample matrix Y ═ Ψ₁,Ψ₂,.....,Ψ_s]∈R^n×s。

Sorting the column vectors of a left singular value matrix U of a sample matrix from large to small, wherein U is [ U ═ U₁,u₂,.....,u_n]∈R^n×nAnd intercepting the first d characteristic values to form an orthonormal basis vector xi of the sample set_i＝u_i(i＝1、2、...d)。

With truncated orthonormal base P ═ xi₁,ξ₂,...,ξ_d]∈R^n×dReconstructing the field potential to obtainWith reconstructed field potentials (instead of before reconstruction)Field potential) into a finite element discrete algebraic equation solving for the potential. The reduced finite element discrete algebraic equation of the solution potential can be obtained, the original finite element discrete algebraic equation of the solution potential is changed from n order to d order, and d is less than n, thereby completing the model reduction.

The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.