Modeling method and device for broadband transient model of electromagnetic voltage transformer

Abstract

The invention discloses a modeling method and device for a broadband transient model of an electromagnetic voltage transformer, and relates to the technical field of voltage transformers, and the method comprises the following steps: carrying out the capacitance simplification of a target voltage transformer, replacing the magnetic hysteresis of an iron core of the target voltage transformer with nonlinear impedance, and carrying out the modeling of a broadband transient model of the target voltage transformer; processing to obtain a pi-type equivalent circuit of the target voltage transformer; and based on the pi-type equivalent circuit, a nonlinear excitation characteristic curve of the PT is calculated by using a piecewise linear method. According to the method, the influence of stray capacitance of the PT is effectively avoided, and the excitation inductance model is established by using the piecewise linearization method, so that an effective theoretical basis is provided for metrological characteristic analysis and online error evaluation of the electromagnetic voltage transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of voltage transformers, and in particular to a method and device for modeling a broadband transient model of an electromagnetic voltage transformer. Background Art

[0002] With the increase in nonlinear loads in new distribution networks, power systems will face the challenge of various high-frequency harmonic injections. Transformers, the most widely used metering devices, rely primarily on electromagnetic coils to transmit signals. High-order harmonic injection can easily saturate the PT core, significantly distorting the secondary waveform and causing significant measurement errors, impacting system reliability and stability. Furthermore, due to the limited operating range of PTs and the transient, wide-band, and high-frequency nature of harmonics, existing PT modeling methods focus on low-frequency applications and ignore their dynamic response characteristics over a wide frequency range. This significantly reduces PT measurement accuracy under high-frequency harmonic conditions, potentially leading to ineffective monitoring and control of the power system, potentially causing equipment damage or power outages. Therefore, broadband PT modeling is crucial for ensuring accurate PT measurement and the safe operation of the power grid.

[0003] Under broadband voltage coverage, due to the high voltage-to-winding ratio of the PT, the hysteresis of its core reflects the nonlinear inductance and energy loss of the core, affecting the PT's electromagnetic transients. Stray capacitance has a greater impact, making hysteresis curve measurement more difficult and more prone to ferromagnetic resonance in the system. This makes effective broadband simulation difficult when the capacitance value is uncertain. Currently, research on broadband equivalent models for PTs is incomplete and does not take into account the new high-frequency and broadband characteristics of harmonics in new distribution networks. Research on the impact of harmonics on metering characteristics is limited, and the quantitative laws are unclear.

[0004] Therefore, in order to meet actual needs, a broadband transient modeling technology for electromagnetic voltage transformer is provided. Summary of the Invention

[0005] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method and device for modeling a broadband transient model of an electromagnetic voltage transformer, effectively avoiding the influence of the stray capacitance of the PT, and establishing an excitation inductance model using a piecewise linearization method, thereby providing an effective theoretical basis for the measurement characteristics analysis and online error evaluation of the electromagnetic voltage transformer.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] In a first aspect, the present application provides a method for modeling a broadband transient model of an electromagnetic voltage transformer, the method comprising the following steps:

[0008] Simplifying the capacitance of a target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer;

[0009] Based on the π-type equivalent circuit, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method.

[0010] On the basis of the above technical solution, the nonlinear excitation characteristic curve of the PT is calculated using the piecewise linear method based on the π-type equivalent circuit, including the following steps:

[0011] Obtaining operating parameters of the target voltage transformer;

[0012] Based on the operating parameters of the target voltage transformer, the corresponding excitation characteristic function is processed by function segmentation to obtain an excitation current parameter expression;

[0013] Processing the current parameter function to obtain an expression for the effective value of the excitation current;

[0014] The current effective value expression is simplified by using a piecewise linear function to obtain the nonlinear excitation characteristic curve; wherein,

[0015] The operating parameters include maximum output power, rated voltage ratio and rated power.

[0016] On the basis of the above technical solution, the nonlinear excitation characteristic curve of the PT is calculated based on the π-type equivalent circuit using a piecewise linear method, including the following steps:

[0017] Based on the π-type equivalent circuit, the voltage-flux conversion relationship is obtained, and then the flux-voltage relationship is obtained, and the corresponding flux peak expression is obtained;

[0018] Perform piecewise linearization based on the curve corresponding to the magnetic flux peak expression to obtain an expression for the effective value of the excitation current;

[0019] Based on the effective value expression of the excitation current, a piecewise linear function is used to simplify the curve, thereby obtaining the nonlinear excitation characteristic curve.

[0020] Based on the above technical solution, the voltage and flux conversion relationship is: in,

[0021] u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer.

[0022] Based on the above technical solution, the relationship between voltage and magnetic flux is:

[0023] On the basis of the above technical solution, when sinωt=1, the peak value of magnetic flux is expressed as in,

[0024] j represents the jth point on the magnetizing inductance curve.

[0025] On the basis of the above technical solution, the nonlinear excitation characteristic curve of the PT is calculated based on the π-type equivalent circuit using a piecewise linear method, including the following steps:

[0026] Based on the π-type equivalent circuit, the voltage and magnetic flux conversion relationship is obtained, which is: u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer;

[0027] Based on the voltage and magnetic flux conversion relationship, the voltage and magnetic flux relationship is obtained, which is:

[0028] When sinωt=1, the peak value expression of the magnetic flux is obtained, which is: Where, j represents the jth point on the excitation inductance curve, ψ j Expressed as the peak value of the magnetic flux at the jth point of the excitation inductance;

[0029] Using piecewise linearization to l The solution requires the curve ψ-i l The first point on (ψ1,i l1 ) as the origin, set the second point (ψ2,i l2 ) is located on the linear segment, then the excitation current i at the second point is l2 and i r2 The effective value of the excitation current I2 at the second point satisfies

[0030] Step by step calculation, we can get i l2 ,i l3 ,...,i l(k-1) , for i lk To solve, the curve can be segmented from point 1 to point k, and the piecewise linear function equation can be obtained:

[0031]

[0032] Current effective value I k Need to meet: And simplify obtaining

[0033] Using piecewise linear function curve Segmentation yields:

[0034] where i rj is the right current at the jth point;

[0035] where i lj is the left current at the jth point;

[0036] Obtain each point i on the nonlinear excitation characteristic curve lk , and then obtain the nonlinear excitation characteristic curve.

[0037] On the basis of the above technical solution, the target voltage transformer is subjected to capacitance simplification, and the core hysteresis of the target voltage transformer is replaced by nonlinear impedance to obtain a π-type equivalent circuit of the target voltage transformer, including the following steps:

[0038] Simplifying the capacitance of a target voltage transformer to obtain a target voltage transformer circuit after capacitance simplification;

[0039] Based on the target voltage transformer circuit after capacitance simplification, using nonlinear impedance to replace the core hysteresis of the target voltage transformer to obtain a replaced target voltage transformer circuit;

[0040] Based on the replaced target voltage transformer circuit, a π-type equivalent circuit of the target voltage transformer is obtained.

[0041] In a second aspect, the present application further provides a device for modeling a broadband transient model of an electromagnetic voltage transformer, the device comprising:

[0042] A circuit equivalent module, which is used to simplify the capacitance of the target voltage transformer, use nonlinear impedance to replace the core hysteresis of the target voltage transformer, and obtain a π-type equivalent circuit of the target voltage transformer;

[0043] The excitation curve acquisition module is used to calculate and obtain the nonlinear excitation characteristic curve of the PT using a piecewise linear method based on the π-type equivalent circuit.

[0044] Compared with the prior art, the advantages of the present invention are:

[0045] The present invention effectively avoids the influence of stray capacitance of PT and establishes an excitation inductance model by using a piecewise linearization method, thereby providing an effective theoretical basis for the measurement characteristic analysis and online error evaluation of electromagnetic voltage transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0047] Figure 1 This is a simplified capacitance model diagram of a PT in a broadband transient modeling method of an electromagnetic voltage transformer according to an embodiment of the present invention;

[0048] Figure 2 This is a PT equivalent circuit diagram that takes into account broadband stray capacitance and core hysteresis in a broadband transient model modeling method for an electromagnetic voltage transformer according to an embodiment of the present invention;

[0049] Figure 3 This is a π-type equivalent circuit diagram calculated to the secondary side in the modeling method of the electromagnetic voltage transformer broadband transient model according to an embodiment of the present invention;

[0050] Figure 4 This is a broadband modeling simulation diagram established in the broadband transient modeling method of an electromagnetic voltage transformer according to an embodiment of the present invention;

[0051] Figure 5 This is a specific implementation flow chart of the method for modeling a broadband transient model of an electromagnetic voltage transformer according to an embodiment of the present invention;

[0052] Figure 6 This is a comparison chart between the modeling calculation results and the measured results in the electromagnetic voltage transformer broadband transient modeling method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0055] The embodiments of the present application provide a method and device for modeling a broadband transient model of an electromagnetic voltage transformer, which effectively avoids the influence of the stray capacitance of the PT and establishes an excitation inductance model using a piecewise linearization method, thereby providing an effective theoretical basis for the measurement characteristic analysis and online error evaluation of the electromagnetic voltage transformer.

[0056] To achieve the above technical effects, the overall idea of ​​this application is as follows:

[0057] A method for modeling a broadband transient model of an electromagnetic voltage transformer, the method comprising the following steps:

[0058] Simplifying the capacitance of a target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer;

[0059] Based on the π-type equivalent circuit, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method.

[0060] The embodiments of the present application are further described in detail below with reference to the accompanying drawings.

[0061] First, see Figures 1 to 6 As shown, an embodiment of the present application provides a method for modeling a broadband transient model of an electromagnetic voltage transformer, the method comprising the following steps:

[0062] Simplifying the capacitance of a target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer;

[0063] Based on the π-type equivalent circuit, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method.

[0064] It should be noted that new disturbance characteristics such as excessive harmonics and broadband oscillations have appeared in the new distribution network. In response to the above situation, the technical solution of the embodiment of the present application can consider the π-type broadband equivalent model of the PT under the action of broadband stray capacitance and magnetic core hysteresis, and study the influence of multiple types of harmonics on the metering characteristics of the electromagnetic voltage transformer, providing an effective theoretical basis for the analysis of the metering characteristics of the electromagnetic voltage transformer and the realization of online evaluation of the transformer error.

[0065] Compared to traditional low-frequency or single-harmonic modeling of their metrological characteristics, this study of the effects of broadband stray capacitance and the superposition of multiple broadband harmonic frequencies has achieved more accurate voltage measurement, providing an effective theoretical basis for analyzing the metrological characteristics of electromagnetic voltage transformers and implementing online transformer error evaluation. Broadband modeling methods include simplifying broadband stray capacitance, calculating secondary parameters, segmenting nonlinear excitation curves, and solving piecewise linear functions.

[0066] Simplifying the broadband stray capacitance in the PT requires simplifying the broadband stray capacitance C under the condition of selecting a good grounding. p1 、C p2 and C 12 , and use the substitution principle to convert all broadband capacitors into equivalent capacitors on the high-voltage side. The calculation process needs to take into account the band capacitance Cp1 The voltage across C p2 The voltage across the two ends, the current flowing through C 12 The current and the PT's transformation ratio k.

[0067] Solving the PT model with high-frequency stray capacitance requires replacing the hysteresis module in the model with a nonlinear excitation impedance under wide-band conditions. After all circuit parameters are converted to the PT's secondary side, the PT's nonlinear excitation characteristic curve is calculated. This requires considering the secondary and primary internal resistances, core hysteresis, equivalent internal excitation impedance, and leakage flux.

[0068] The segmented nonlinear excitation curve takes into account the flux and current peak values ​​under the test, and equates the PT to a flux-controlled nonlinear inductor. A nonlinear excitation inductance model is established, and the DC component is ignored during the calculation process. The points on the excitation characteristic curve are segmented, and each segment can be approximated by a linear equation.

[0069] The piecewise linear function for solving the linear equations divides the flux, current and voltage parameters in the linear equations into segments within the phase angle period, and simplifies them using the parity of the current within the period. At the same time, the flux peak corresponds to the current peak, and the PT excitation characteristic curve is obtained by solving the equation.

[0070] Compared with the existing PT broadband modeling, the embodiments of the present application have the following advantages:

[0071] 1. The influence of broadband stray capacitance is taken into account in the broadband modeling of PT;

[0072] 2. Establish a broadband hysteresis model and replace the hysteresis module with nonlinear excitation impedance under broadband conditions;

[0073] 3. Use the piecewise linearization method to establish a nonlinear excitation inductance model;

[0074] Furthermore, the step of calculating the nonlinear excitation characteristic curve of the PT using a piecewise linear method based on the π-type equivalent circuit includes the following steps:

[0075] Obtaining operating parameters of the target voltage transformer;

[0076] Based on the operating parameters of the target voltage transformer, the corresponding excitation characteristic function is processed by function segmentation to obtain an excitation current parameter expression;

[0077] Processing the current parameter function to obtain an expression for the effective value of the excitation current;

[0078] The current effective value expression is simplified by using a piecewise linear function to obtain the nonlinear excitation characteristic curve; wherein,

[0079] The operating parameters include maximum output power, rated voltage ratio and rated power.

[0080] Furthermore, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method based on the π-type equivalent circuit, including the following steps:

[0081] Based on the π-type equivalent circuit, the voltage-flux conversion relationship is obtained, and then the flux-voltage relationship is obtained, and the corresponding flux peak expression is obtained;

[0082] Perform piecewise linearization based on the curve corresponding to the magnetic flux peak expression to obtain an expression for the effective value of the excitation current;

[0083] Based on the effective value expression of the excitation current, a piecewise linear function is used to simplify the curve, thereby obtaining the nonlinear excitation characteristic curve.

[0084] Furthermore, the voltage and flux conversion relationship is: in,

[0085] u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer.

[0086] Furthermore, the relationship between voltage and magnetic flux is:

[0087] Furthermore, when sinωt=1, the peak value of the magnetic flux is expressed as

[0088] in,

[0089] j represents the jth point on the magnetizing inductance curve.

[0090] Furthermore, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method based on the π-type equivalent circuit, including the following steps:

[0091] Based on the π-type equivalent circuit, the voltage and magnetic flux conversion relationship is obtained, which is: u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer;

[0092] Based on the voltage and magnetic flux conversion relationship, the voltage and magnetic flux relationship is obtained, which is:

[0093] When sinωt=1, the peak value expression of the magnetic flux is obtained, which is: Where, j represents the jth point on the excitation inductance curve, ψ jExpressed as the peak value of the magnetic flux at the jth point of the excitation inductance;

[0094] Using piecewise linearization to l The solution requires the curve ψ-i l The first point on (ψ1,i l1 ) as the origin, set the second point (ψ2,i l2 ) is located on the linear segment, then the excitation current i at the second point is l2 and i r2 The effective value of the excitation current I2 at the second point satisfies

[0095] Step by step calculation, we can get i l2 ,i l3 ,...,i l(k-1) , for i lk To solve, the curve can be segmented from point 1 to point k, and the piecewise linear function equation can be obtained:

[0096]

[0097] Current effective value I k Need to meet: And simplify obtaining

[0098] Using piecewise linear function curve Segmentation yields:

[0099] where i rj is the right current at the jth point;

[0100] where i lj is the left current at the jth point;

[0101] Obtain each point i on the nonlinear excitation characteristic curve lk , and then obtain the nonlinear excitation characteristic curve.

[0102] Furthermore, the capacitor simplification of the target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer include the following steps:

[0103] Simplifying the capacitance of a target voltage transformer to obtain a target voltage transformer circuit after capacitance simplification;

[0104] Based on the target voltage transformer circuit after capacitance simplification, using nonlinear impedance to replace the core hysteresis of the target voltage transformer to obtain a replaced target voltage transformer circuit;

[0105] Based on the replaced target voltage transformer circuit, a π-type equivalent circuit of the target voltage transformer is obtained.

[0106] It should be noted that the technical solution of the embodiment of the present application has the following technical advantages:

[0107] First, the modeling method takes into account the stray capacitance of the electromagnetic voltage transformer, and the modeling work includes the high-voltage primary side, the hysteresis module, and the low-voltage secondary side.

[0108] Second, the modeling approach needs to account for the broadband stray capacitance of the PT.

[0109] Third, the modeling method uses PT to establish a broadband excitation inductance model, and replaces the hysteresis module in the broadband model with the nonlinear excitation impedance under broadband conditions.

[0110] Fourth, the modeling method utilizes the substitution principle to convert the high-frequency stray capacitance into the equivalent capacitance on the high-voltage side of the PT.

[0111] Fifth, the modeling method considers the nonlinear inductance of the excitation inductance and establishes a nonlinear excitation inductance model.

[0112] Sixth, the best modeling method can be obtained by using a piecewise linear function curve while considering the DC component.

[0113] The technical solution of the embodiment of the present application is specifically implemented as follows:

[0114] Step 1: Simplify the capacitance of the PT. When the PT is well grounded, the stray capacitance can be simplified to three capacitors, namely C p1 、C p2 and C 12 ,like Figure 1 As shown, we can get formula (1):

[0115]

[0116] Where u1, u2 and i1 represent the capacitance C p1 The voltage across C p2 The voltage across the terminals and the current flowing through C 12 The current of the capacitor C is 1 / 4 of the PT. 12 Can be equivalent to C 12a and C 12b , as shown in Announcement (2):

[0117]

[0118] By converting all capacitances to the equivalent capacitance C1 of the high voltage measurement, we can obtain the following by deducing equations (1) and (2):

[0119]

[0120] Therefore, the stray capacitance of the PT can be simplified to be equivalent to an equivalent capacitor C1 on the high voltage side.

[0121] Step 2: Use nonlinear impedance to replace the core hysteresis in the model, such as Figure 2 As shown, the (A, N) terminal is the primary side, and the corresponding voltage level is 110kV; the (1a, 1n) and (2a, 2n) terminals are the secondary side, and the corresponding voltage level is 100V;

[0122] R1, L1, R2, L2, R3 and L3 represent the resistance and leakage inductance of each winding respectively;

[0123] H1 represents the core hysteresis of the primary side, R m1 , L m1 is the equivalent internal excitation impedance of the PT primary side.

[0124] Step 3: Since the leakage impedance of PT is generally small, in order to facilitate calculation and measurement, Figure 2 All parameters are converted to the secondary side of PT, and the results are as follows Figure 3 The π-type equivalent circuit of the PT shown.

[0125] Among them, C1' represents the PT stray capacitance calculated to the secondary side; R1' represents the internal resistance of the primary winding calculated to the secondary side; H1' is the PT core hysteresis calculated to the secondary side, R' m1 and L' m1 is the equivalent internal excitation impedance of the primary side converted to the secondary side; R2 is the internal resistance of the secondary winding; H2 is the core hysteresis of the secondary side, R m2 , L m2 is the equivalent internal excitation impedance of the PT secondary side; L s It is expressed as the leakage flux generated by PT.

[0126] Step 4: Use the piecewise linear method to calculate the nonlinear excitation characteristic curve of the PT. It is necessary to consider the nonlinearity of the excitation inductance after adding stray capacitance. It divides the nonlinear characteristic curve into several segments, and uses a straight line segment to approximate the characteristic curve in each segment. This method makes the nonlinear system approximately equivalent to a linear system in each segment, so that the theory and method of the linear system can be used for analysis. Use the piecewise linear method to calculate the nonlinear excitation characteristic curve of the PT. It is necessary to consider the nonlinearity of the excitation inductance after adding stray capacitance. The volt-ampere characteristic curve measured by the transformer or voltage transformer is divided into infinitely short line segments. The points in each approximate straight line are represented by (U k ,I k ) is used to express it. In this way, the measured (U k ,Ik ) into corresponding points and then fit these points into the excitation characteristics ψ-i l Curve. Its excitation characteristic curve ψ-i l The values ​​above are the peak values ​​of magnetic flux and current under test. The implementation steps are as follows:

[0127] Step 1: For the excitation inductor, the relationship between its voltage and magnetic flux conversion can be expressed by formula (4), where u is the voltage on both sides of the excitation inductor and ψ is the magnetic flux passing through the excitation inductor.

[0128]

[0129] From formula (4), the relationship between magnetic flux and voltage can be obtained as follows:

[0130]

[0131] Therefore, under different experimental voltages, when sinωt=1, it is expressed as follows: (6), where j is the peak value of the magnetic flux at the jth point of the excitation inductance.

[0132]

[0133] Step 2: Use piecewise linearization to solve i l The solution requires the curve ψ-i l The first point on (ψ1,i l1 ) as the origin, set the second point (ψ2,i l2 ) is located on the linear segment, then the excitation current i at the second point is l2 and i r2 The effective value of the excitation current I2 at the second point satisfies formula (7):

[0134]

[0135] Similarly, we can get i by step-by-step calculation l2 ,i l3 ,...,i l(k-1) , and for i lk To solve the problem, the first point to the kth point on the curve can be segmented. According to the piecewise linear function equation, formula (8) can be obtained as follows:

[0136]

[0137] Step 3: Using the effective value of current I k satisfy:

[0138]

[0139] Considering the excitation right current i ris an even function about ωt=π / 2 in the range of 0≤ωt≤π, and the left excitation current i l is an odd function about ωt=π / 2 in the range of 0≤ωt≤π, and formula (9) can be simplified to:

[0140]

[0141] Step 4: Use piecewise linear function curve to Segmentation yields:

[0142]

[0143] Among them, i rj is the right current at the jth point. When the phase angle increases to the peak value π / 2, both ψ and i will increase to the maximum value. Similarly, using the piecewise linear function curve By segmenting and further deducing, we can get:

[0144]

[0145] where i lj is the left current at the jth point, ωt in equations (11) and (12) ij =arcsin(u j / u k ),j=1,2…k, Substituting formula (11) and formula (12) into formula (10) can obtain the equation containing only the unknown quantity i lk The quadratic equation of one variable, and by solving this equation, we can get the points i on the excitation characteristic curve lk . Then connect all the points in this way to obtain the PT excitation characteristic curve.

[0146] It should be noted that for a nonlinear inductor, the accuracy of the established broadband model needs to be verified, especially in the core saturation region, where the measurement error caused by the current effective value method is eliminated. After the current value is calculated using the broadband modeling method, the model parameters are optimized and adjusted using inverse calculation.

[0147] In a second aspect, an embodiment of the present application provides a device for modeling a broadband transient model of an electromagnetic voltage transformer, the device comprising:

[0148] A circuit equivalent module, which is used to simplify the capacitance of the target voltage transformer, use nonlinear impedance to replace the core hysteresis of the target voltage transformer, and obtain a π-type equivalent circuit of the target voltage transformer;

[0149] The excitation curve acquisition module is used to calculate and obtain the nonlinear excitation characteristic curve of the PT using a piecewise linear method based on the π-type equivalent circuit.

[0150] In the embodiment of the present application, the influence of the stray capacitance of the PT is effectively avoided, and the excitation inductance model is established by using the piecewise linearization method, thereby providing an effective theoretical basis for the measurement characteristic analysis and online error evaluation of the electromagnetic voltage transformer.

[0151] Furthermore, the excitation curve acquisition module is further configured to execute the following process:

[0152] Obtaining operating parameters of the target voltage transformer;

[0153] Based on the operating parameters of the target voltage transformer, the corresponding excitation characteristic function is processed by function segmentation to obtain an excitation current parameter expression;

[0154] Processing the current parameter function to obtain an expression for the effective value of the excitation current;

[0155] The current effective value expression is simplified by using a piecewise linear function to obtain the nonlinear excitation characteristic curve; wherein,

[0156] The operating parameters include maximum output power, rated voltage ratio and rated power.

[0157] Furthermore, the excitation curve acquisition module is further configured to execute the following process:

[0158] Based on the π-type equivalent circuit, the voltage-flux conversion relationship is obtained, and then the flux-voltage relationship is obtained, and the corresponding flux peak expression is obtained;

[0159] Perform piecewise linearization based on the curve corresponding to the magnetic flux peak expression to obtain an expression for the effective value of the excitation current;

[0160] Based on the effective value expression of the excitation current, a piecewise linear function is used to simplify the curve, thereby obtaining the nonlinear excitation characteristic curve.

[0161] Furthermore, the voltage and flux conversion relationship is: in,

[0162] u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer.

[0163] Furthermore, the relationship between voltage and magnetic flux is:

[0164] Furthermore, when sinωt=1, the peak value of the magnetic flux is expressed as

[0165] in,

[0166] j represents the jth point on the magnetizing inductance curve.

[0167] Furthermore, the excitation curve acquisition module is further configured to execute the following process:

[0168] Based on the π-type equivalent circuit, the voltage and magnetic flux conversion relationship is obtained, which is: u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer.

[0169] Based on the voltage and magnetic flux conversion relationship, the voltage and magnetic flux relationship is obtained, which is:

[0170] When sinωt=1, the peak value expression of the magnetic flux is obtained, which is: Where, j represents the jth point on the excitation inductance curve, ψ j Expressed as the peak value of the magnetic flux at the jth point of the excitation inductance;

[0171] Using piecewise linearization to l The solution requires the curve ψ-i l The first point on (ψ1,i l1 ) as the origin, set the second point (ψ2,i l2 ) is located on the linear segment, then the excitation current i at the second point is l2 and i r2 The effective value of the excitation current I2 at the second point satisfies

[0172] Step by step calculation, we can get i l2 ,i l3 ,...,i l(k-1) , for i lk To solve, the curve can be segmented from point 1 to point k, and the piecewise linear function equation can be obtained:

[0173]

[0174] Current effective value I k Need to meet: And simplify obtaining

[0175] Using piecewise linear function curve Segmentation yields:

[0176] where i rj is the right current at the jth point;

[0177] where i lj is the left current at the jth point;

[0178] Obtain each point i on the nonlinear excitation characteristic curve lk , and then obtain the nonlinear excitation characteristic curve.

[0179] Furthermore, the circuit equivalent module is also used to perform the following process:

[0180] Simplifying the capacitance of a target voltage transformer to obtain a target voltage transformer circuit after capacitance simplification;

[0181] Based on the target voltage transformer circuit after capacitance simplification, using nonlinear impedance to replace the core hysteresis of the target voltage transformer to obtain a replaced target voltage transformer circuit;

[0182] Based on the replaced target voltage transformer circuit, a π-type equivalent circuit of the target voltage transformer is obtained.

[0183] It should be noted that the electromagnetic voltage transformer wide-band transient model modeling device mentioned in the second aspect is similar to the technical principles of the electromagnetic voltage transformer wide-band transient model modeling method mentioned in the first aspect in terms of technical issues, technical means and technical effects, and will not be elaborated here.

[0184] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0185] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0186] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for modeling a broadband transient model of an electromagnetic voltage transformer, characterized in that: The method comprises the following steps: Simplifying the capacitance of a target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer; Based on the π-type equivalent circuit, the nonlinear excitation characteristic curve of the PT is calculated using a piecewise linear method.

2. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 1, wherein: The method of calculating the nonlinear excitation characteristic curve of the PT using a piecewise linear method based on the π-type equivalent circuit includes the following steps: Obtaining operating parameters of the target voltage transformer; Based on the operating parameters of the target voltage transformer, the corresponding excitation characteristic function is processed by function segmentation to obtain an excitation current parameter expression; Processing the current parameter function to obtain an expression for the effective value of the excitation current; The current effective value expression is simplified by using a piecewise linear function to obtain the nonlinear excitation characteristic curve; wherein, The operating parameters include maximum output power, rated voltage ratio and rated power.

3. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 1, wherein: The method of calculating the nonlinear excitation characteristic curve of the PT based on the π-type equivalent circuit using a piecewise linear method includes the following steps: Based on the π-type equivalent circuit, the voltage-flux conversion relationship is obtained, and then the flux-voltage relationship is obtained, and the corresponding flux peak expression is obtained; Perform piecewise linearization based on the curve corresponding to the magnetic flux peak expression to obtain an expression for the effective value of the excitation current; Based on the effective value expression of the excitation current, a piecewise linear function is used to simplify the curve, thereby obtaining the nonlinear excitation characteristic curve.

4. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 3, wherein: The voltage and flux conversion relationship is: in, u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer.

5. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 4, wherein: The relationship between voltage and magnetic flux is:

6. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 5, wherein: When sinωt=1, the peak value of magnetic flux is expressed as follows: in, j represents the jth point on the magnetizing inductance curve.

7. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 1, wherein: The method of calculating the nonlinear excitation characteristic curve of the PT based on the π-type equivalent circuit using a piecewise linear method includes the following steps: Based on the π-type equivalent circuit, the voltage and magnetic flux conversion relationship is obtained, which is: u is the voltage on both sides of the excitation inductor, ψ is the magnetic flux passing through the excitation inductor, and ω is the angular frequency of the voltage signal in the voltage transformer. Based on the voltage and magnetic flux conversion relationship, the voltage and magnetic flux relationship is obtained, which is: When sinωt=1, the peak value expression of the magnetic flux is obtained, which is: Where, j represents the jth point on the excitation inductance curve, ψ j Expressed as the peak value of the magnetic flux at the jth point of the excitation inductance; Using piecewise linearization to l The solution requires the curve ψ-i l The first point on (ψ1,i l1 ) as the origin, set the second point (ψ2,i l2 ) is located on the linear segment, then the excitation current i at the second point is l2 and i r2 The effective value of the excitation current I2 at the second point satisfies Step by step calculation, we can get i l2 ,i l3 ,...,i l(k-1) , for i lk To solve, the curve can be segmented from point 1 to point k, and the piecewise linear function equation can be obtained: Current effective value I k Need to meet: And simplify obtaining Using piecewise linear function curve Segmentation yields: where i rj is the right current at the jth point; where i lj is the left current at the jth point; Obtain each point i on the nonlinear excitation characteristic curve lk , and then obtain the nonlinear excitation characteristic curve.

8. The method for modeling a broadband transient model of an electromagnetic voltage transformer according to claim 1, wherein: The method of simplifying the capacitance of the target voltage transformer, replacing the core hysteresis of the target voltage transformer with a nonlinear impedance, and obtaining a π-type equivalent circuit of the target voltage transformer comprises the following steps: Simplifying the capacitance of a target voltage transformer to obtain a target voltage transformer circuit after capacitance simplification; Based on the target voltage transformer circuit after capacitance simplification, using nonlinear impedance to replace the core hysteresis of the target voltage transformer to obtain a replaced target voltage transformer circuit; Based on the replaced target voltage transformer circuit, a π-type equivalent circuit of the target voltage transformer is obtained through processing.

9. A broadband transient modeling device for an electromagnetic voltage transformer, characterized in that: The device comprises: A circuit equivalent module, which is used to simplify the capacitance of the target voltage transformer, use nonlinear impedance to replace the core hysteresis of the target voltage transformer, and obtain a π-type equivalent circuit of the target voltage transformer; The excitation curve acquisition module is used to calculate and obtain the nonlinear excitation characteristic curve of the PT using a piecewise linear method based on the π-type equivalent circuit.

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