A correction method considering eddy current loss power frequency characteristics and electronic equipment

Abstract

The application provides a correction method and electronic equipment considering eddy current loss power frequency characteristics, utilizes the rule that the copper winding wire generates eddy current loss power in the Helmholtz coil magnetic field with the change of excitation current frequency, equivalently obtains the correction amount of the frequency characteristics of the converter transformer eddy current loss power caused by the skin effect, and utilizes the obtained correction factor to correct the extrapolation result obtained according to the current standard, so that the error is smaller; a numerical model of the Helmholtz coil and the winding wire is built; the geometric parameters of the model can be set according to the winding wire parameters of the converter transformer provided by the manufacturer; the excitation current with different frequencies is applied to the Helmholtz coil, and the change rule of the magnetic induction intensity and the eddy current loss power in the winding wire is analyzed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power equipment energy efficiency evaluation, and particularly relates to a correction method considering eddy current loss power frequency characteristics and an electronic device. BACKGROUND

[0002] Compared with high-voltage alternating current transmission technology, high-voltage direct current transmission has lower cost, smaller line loss, and easier grid operation, and is an important power transmission mode. As a core device in the high-voltage direct current transmission system, the stability of the converter transformer is closely related to the safe operation of the system. Loss power is one of the important electrical indicators of the converter transformer. If the loss power of the converter transformer is too large, the economy of the power transmission system will be reduced, and the converter transformer will be overheated, resulting in insulation failure and other serious accidents. When the rectifier, inverter and other power electronic devices in the high-voltage direct current transmission system are running, a large amount of harmonic components will be generated. Therefore, when calculating the loss power of the converter transformer, the influence of the harmonic components must be considered. However, it is difficult to implement the scheme of directly measuring the loss power of the converter transformer by using harmonic power sources and other devices and instruments on the site of the converter transformer. Therefore, it is necessary to study the variation law of the loss power of the converter transformer under different excitation frequencies.

[0003] At present, the domestic converter transformer manufacturers mainly use the fitting formula recommended in IEC 61378-2 and GB / T 18494.2 standards to calculate the loss power of each component of the converter transformer. However, the fitting formula recommended in these standards is based on the experimental test of industrial transformers. However, the capacity of the converter transformer used now has greatly exceeded that of the industrial transformer, and the structures of the two are also different, resulting in a large error between the calculation results obtained by the fitting formula recommended in the above standards and the actual measurement results of the loss power of the converter transformer. In order to improve the calculation accuracy of the loss power of the converter transformer, it is necessary to modify the fitting formula recommended in the existing standards. J.A.C Forrest, Yidirim, Fuchs and others tested the harmonic loss power of several different types of converter transformers at low current, and the results showed that the harmonic loss power of the converter transformer is basically proportional to the square of the harmonic frequency. Some scholars pointed out that the eddy current loss power of the converter transformer is not only related to the frequency of excitation, but also needs to consider the shape and size of the winding wire. In view of the large deviation of the fitting formula recommended in the above standards in calculating the high-frequency eddy current loss power of the converter transformer, A.E.Emanuel and others pointed out through analysis that it is because the influence of the skin effect is ignored, and then put forward a correction factor. Zhang Liangxian and others put forward a harmonic loss power correction factor based on the finite element simulation results, which is used to correct the calculation results. The experimental results show that after the harmonic loss power factor is corrected, the calculation results are closer to the results of the finite element simulation than the calculation results obtained by the fitting formula recommended in the above two standards, but there is still a large error at high frequency. J.A.Ferreira proposed a mathematical model to characterize the influence of the skin effect with the effective flow area, but it is a one-dimensional model and is not suitable for calculating the loss power of the winding flat cross-section wire of the converter transformer. Liu Yaqing deduced the calculation formula of the eddy current loss power of the winding of the converter transformer, and put forward a correction factor to characterize the skin effect, which is still relatively consistent for the case that the cross-sectional width of the winding flat wire of the converter transformer is small, but it is not suitable for calculating the eddy current loss power of the winding flat wire of the converter transformer when the cross-sectional width is large. SUMMARY

[0004] The present application aims at the deficiencies of the prior art, and provides a correction method considering the frequency characteristics of eddy current loss power and electronic equipment, which obviously improves the accuracy of the correction factor, simplifies the problem, speeds up the calculation, and reduces the consumption of computing resources.

[0005] To achieve the above object, the present application adopts the following technical scheme:

[0006] The present application provides a correction method considering the frequency characteristics of eddy current loss power, comprising the following steps:

[0007] S1, build a numerical calculation model of the Helmholtz coil and the winding wire of the converter transformer;

[0008] S2, set the parameters of the winding wire in the model according to the data of the converter transformer;

[0009] S3, apply excitation current to the Helmholtz coil from low to high frequency;

[0010] S4, change the width and height of the cross section of the winding wire of the converter transformer;

[0011] S5, synthesize S2, S3 and S4, draw the characteristic curve of the correction amount change of the eddy current loss power frequency characteristic of the converter transformer, and analyze the correction accuracy.

[0012] Further, the numerical calculation model of the Helmholtz coil is:

[0013] Two identical coils are established, and the two coils are kept parallel; the distance between the centers of the two coils is set as the radius of the coil;

[0014] The numerical calculation model of the winding wire of the converter transformer is to place a copper block at the center of the space of the two coils.

[0015] Further, the current direction in the two coils is consistent and the current size is the same.

[0016] Further, by changing the width and height of the cross section of the winding wire of the converter transformer, the average value of the eddy current loss power in the winding wire of the converter transformer changes with the excitation current frequency as:

[0017] When the width of the winding wire of the converter transformer is less than 5mm, the height of the winding wire of the converter transformer has no effect on the curve of the change of the eddy current loss power with the harmonic number;

[0018] When the width of the winding wire of the converter transformer is greater than 5mm, the eddy current loss power begins to differ from the height value of the winding wire of the converter transformer, and under high harmonic, the difference of the obtained eddy current loss power reaches 20%.

[0019] Further, after simulating the numerical value of the eddy current loss power of the cross section of the winding wire of the converter transformer under different excitation frequencies, the correction amount is:

[0020]

[0021] Where, P WEh is the eddy current loss power; P WE1 is the eddy current loss power; f1 is the fundamental frequency, which is 50Hz; f h is the frequency of hth harmonic.

[0022] Further, an electronic device includes one or more processors; and a storage storing one or more programs, when the one or more programs are executed by the one or more processors, the one or more processors implement the correction method considering the eddy current loss power frequency characteristic.

[0023] Further, a computer program is stored thereon, when the computer program is executed by a processor, the correction method considering the eddy current loss power frequency characteristic is implemented.

[0024] The correction method of the eddy current loss power frequency characteristic of the converter transformer according to the embodiment of the present application utilizes the rule that the eddy current loss power generated by the single conductor of the winding in the magnetic field of the Helmholtz coil varies with the frequency of the excitation current, equivalently obtains the correction amount of the eddy current loss power frequency characteristic of the winding wire of the converter transformer caused by the skin effect, and is compared with the existing correction method in the literature. The theoretical and numerical analysis shows that the method proposed in the present application is more in line with the physical characteristics that the leakage magnetic field of the converter transformer generates the eddy current loss power in the winding wire on the magnetic circuit, has guiding significance for more accurately evaluating the harmonic eddy current loss power of the converter transformer, and has a very wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The block diagram of the correction method of the eddy current loss power frequency characteristic according to the present application;

[0026] Figure 2 The schematic diagram of the magnetic field distribution generated by the current-carrying Helmholtz coil according to the embodiment of the present application;

[0027] Figure 3 The schematic diagram of the characteristic curve of the average eddy current loss power of the winding wire cross section varying with the excitation current frequency and the winding wire size according to the embodiment;

[0028] Figure 4 The schematic diagram of the comparison of the calculation results of different converter transformer eddy current loss power models;

[0029] Figure 5 The schematic diagram of the typical excitation current waveform of the converter transformer and the frequency spectrum thereof;

[0030] Figure 6 The schematic diagram of the comparison of the harmonic eddy current loss power calculated by different methods under the typical excitation current waveform of the converter transformer. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0032] Please refer to Figures 1 to 6 A correction method considering the frequency characteristics of eddy current loss power, comprising the following steps:

[0033] S1, a numerical calculation model of a Helmholtz coil and a winding wire of a converter transformer is built;

[0034] S2, according to the winding wire parameters provided by the manufacturer, the winding wire parameters in the model are set;

[0035] S3, the excitation current is applied to the Helmholtz coil from low to high according to the frequency, and the frequency characteristics of the eddy current loss power in the generated magnetic field are analyzed;

[0036] S4, the width and height of the cross section of the winding wire of the converter transformer are changed, and the influence of the geometric parameters of the winding wire on the frequency characteristics of the eddy current loss power of the converter transformer is analyzed;

[0037] S5, the simulation calculation results are integrated, the characteristic curve of the correction amount change of the eddy current loss power frequency characteristics of the converter transformer is drawn, and the correction accuracy is analyzed, please refer to Figure 2 .

[0038] The numerical calculation model of the Helmholtz coil is:

[0039] Two identical coils are established, and the two coils are kept parallel; the distance between the centers of the two coils is set as the radius of the coil;

[0040] The numerical calculation model of the winding wire of the converter transformer is that a copper block is placed at the center of the space of the two coils.

[0041] The current directions in the two coils are consistent and the current sizes are the same.

[0042] By changing the width and height of the cross section of the winding wire of the converter transformer, the average value of the eddy current loss power in the winding wire of the converter transformer changes with the frequency of the excitation current as follows:

[0043] When the width of the winding wire of the converter transformer is less than 5mm, the height of the winding wire of the converter transformer has little effect on the curve of the change of the eddy current loss power with the harmonic number;

[0044] When the width of the converter transformer winding wire is greater than 5mm, the eddy current loss power starts to be sensitive to the height of the converter transformer winding wire, and the difference of the obtained eddy current loss power reaches 20% under high-order harmonics.

[0045] After the simulation obtains the values of the cross-section eddy current loss power of the converter transformer winding wire under different excitation frequencies, the correction amount is:

[0046]

[0047] wherein, P WEh is the eddy current loss power; P WE1 is the eddy current loss power; f1 is the fundamental frequency, which is 50Hz; f h is the frequency of the h-th harmonic.

[0048] An electronic device comprising: one or more processors; a storage device for storing one or more programs, which when executed by the one or more processors, cause the one or more processors to implement a correction method considering the frequency characteristics of eddy current loss power.

[0049] A computer-readable storage medium having stored thereon a computer program, wherein the computer program, when executed by a processor, implements a correction method considering the frequency characteristics of eddy current loss power. Embodiment One:

[0050] In the electromagnetic field numerical calculation software, a simulation model of the Helmholtz coil and the winding wire is built, and appropriate boundary conditions are set.

[0051] The finite element simulation software used in the embodiment is Ansoft Maxwell.

[0052] The winding wire parameters can be set according to the actual parameters of the converter transformer provided by the manufacturer.

[0053] According to the measurement standard IEC-61378-2 of the converter transformer eddy current loss power, the excitation current of the Helmholtz coil is set, and the frequency characteristics of the winding wire eddy current loss power are analyzed.

[0054] In the embodiment, the frequency of the single excitation current is 50Hz, 100Hz, …, 1250Hz in turn, i.e., from the fundamental wave to the 25th harmonic.

[0055] In the embodiment, according to the typical current-carrying waveform of the converter transformer, the excitation current of the Helmholtz coil can be set as a combined waveform of harmonic components 6h±1(h=1,2,3,4).

[0056] The correction amount of the power-frequency characteristic curve of the eddy current loss of the converter transformer is drawn according to the numerical calculation results, the results of different methods are compared, and the correction accuracy of the method discussed in the application is analyzed.

[0057] The calculation models selected for comparison in the embodiment include IEC 61378-2, GB / T 18494.2 model, Emanuel correction model Δ Emanuel , and the correction model Δ HUST proposed by Liu Yaqing et al.

[0058] The calculation formula of the IEC 61378-2 and GB / T 18494.2 model is:

[0059]

[0060] wherein, I1 is the rated current of the converter transformer; I h is the root mean square value of the hth harmonic current; P WE1 is the eddy current loss power of the winding wire at the fundamental frequency; P WEh is the eddy current loss power of the hth harmonic current; f1 is the fundamental frequency, which is 50 Hz in the power grid in China; f h is the frequency of the hth harmonic.

[0061] Δ Emanuel and Δ HUST The calculation formulae are respectively:

[0062]

[0063]

[0064] wherein, a is the width of the cross section of the winding flat wire; is the inverse of the skin depth (ω = 2πf is the harmonic frequency; ρ is the conductivity of the winding wire material; μ is the magnetic permeability of the winding wire material).

[0065] The correction amount obtained by numerical calculation is used to correct the results obtained by calculation according to the existing standard. The correction factor of the application can be expressed as:

[0066]

[0067] wherein, P WE1 is the eddy current loss power of the winding wire of the converter transformer at the fundamental frequency; P WEh is the eddy current loss power of the hth harmonic current, which are both numerical simulation calculation results of the calculation model.

[0068] After considering the correction amount, the eddy current loss power generated by the single harmonic can be rewritten as

[0069]

[0070] The obtained correction model is compared with the calculation results of other correction methods under a typical converter transformer current waveform, and according to the simulation calculation results, it can be seen that the correction method of the frequency characteristic of the eddy current loss power of the converter transformer based on the finite element model has higher accuracy compared with other correction models. For example, under the condition that the cross-section width of the winding flat conductor is a = 10 mm, the total eddy current loss power obtained by using the IEC and GB / T models is 3.1445 pu, the total eddy current loss power obtained by using the Emanuel method is 2.8628 pu, the total eddy current loss power obtained by using the HUST method is 1.6062 pu, and the total eddy current loss power obtained by using the equivalent method proposed in the present application is 2.4428 pu (b = 6 mm) and 2.3291 pu (b = 8 mm).

[0071] Therefore, the proposed correction model can comprehensively consider the influence of the width and height of the cross-section of the winding flat conductor of the converter transformer on the eddy current loss power, overcome the problem that the analytical method can only consider a one-dimensional model, thereby leading to a larger correction error, and has guiding significance for more accurately evaluating the energy efficiency of the converter transformer.

[0072] The above-described embodiments only express the implementation of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application.

Claims

1. A correction method considering the power frequency characteristics of eddy current losses, characterized in that, Includes the following steps: S1. Construct a numerical calculation model of the Helmholtz coil and the winding conductor of the converter transformer. The numerical calculation model is a simulation model. S2. Set the parameters of the winding conductors in the model according to the converter transformer data; S3. Apply excitation current to the Helmholtz coil in ascending frequency order; S4. Change the width and height of the cross-section of the converter transformer winding conductor; S5. Based on the comprehensive simulation results, plot the characteristic curve of the change in the eddy current loss power frequency characteristic correction of the converter transformer. After obtaining the eddy current loss power of the converter transformer winding conductor cross-section under different excitation frequencies through simulation, the correction amount is: ； in, This refers to eddy current loss power; This refers to eddy current loss power; The fundamental frequency is 50Hz. The frequency of the h-th harmonic; Eddy current loss power: ； By changing the width and height of the cross-section of the converter transformer winding conductor, the influence of the winding conductor geometric parameters on the eddy current loss power frequency characteristics of the converter transformer is analyzed. When the width of the converter transformer winding conductor is less than 5mm, the height of the converter transformer winding conductor has no effect on the curve of eddy current loss power changing with harmonic order. When the width of the converter transformer winding conductor is greater than 5mm, the eddy current loss power begins to affect the height of the converter transformer winding conductor. Under higher harmonics, the difference in eddy current loss power reaches 20%.

2. The correction method considering eddy current loss power frequency characteristics according to claim 1, characterized in that, The numerical calculation model of the Helmholtz coil is as follows: Create two identical coils, keeping them parallel; the distance between the centers of the two coils is set as the radius of the coils. The numerical calculation model for the converter transformer winding conductor is as follows: place the copper block at the center of the space between the two coils.

3. The correction method considering eddy current loss power frequency characteristics according to claim 2, characterized in that: The current in both coils is in the same direction and has the same magnitude.

4. An electronic device, characterized in that, include: One or more processors; A storage device for storing one or more programs, which, when executed by one or more processors, cause the one or more processors to implement the correction method for power frequency characteristics taking into account eddy current loss as described in any one of claims 1 to 3.

5. A computer-readable storage medium, characterized in that, It stores a computer program, wherein the computer program, when executed by a processor, implements the correction method for power frequency characteristics considering eddy current loss as described in any one of claims 1 to 3.

Images