CN115219782A - Correction method considering eddy current loss power frequency characteristic and electronic equipment - Google Patents
Correction method considering eddy current loss power frequency characteristic and electronic equipment Download PDFInfo
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- CN115219782A CN115219782A CN202210861057.5A CN202210861057A CN115219782A CN 115219782 A CN115219782 A CN 115219782A CN 202210861057 A CN202210861057 A CN 202210861057A CN 115219782 A CN115219782 A CN 115219782A
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Abstract
The invention provides a correction method and electronic equipment considering the frequency characteristic of eddy current loss power, which utilize the rule that the eddy current loss power generated by a copper winding lead in a Helmholtz coil magnetic field changes along with the frequency of an excitation current to equivalently obtain the correction quantity of the frequency characteristic of the eddy current loss power of a converter transformer caused by skin effect, and utilize the obtained correction factor to correct the extrapolation result calculated according to the current standard so as to reduce the error; numerical models of Helmholtz coils and winding leads are built; the geometric parameters of the model can be set according to the converter transformer winding wire parameters provided by the manufacturer; excitation currents with different frequencies are applied to the Helmholtz coil, and the change rule of the magnetic induction intensity and the eddy current loss power in the winding lead is analyzed.
Description
Technical Field
The invention relates to the field of power equipment energy efficiency evaluation, in particular to a correction method considering eddy current loss power frequency characteristics and electronic equipment.
Background
Compared with a high-voltage alternating-current transmission technology, the high-voltage direct-current transmission has the advantages of lower manufacturing cost of the same level, lower line loss, easier realization of grid-connected operation and the like, and is an important electric energy transmission mode. The converter transformer is used as a core device in a high-voltage direct-current transmission system, and the stability of the converter transformer is closely related to the safe operation of the system. If the converter transformer has excessive loss power, the economy of a power transmission system can be reduced, and serious accidents such as insulation failure and the like of the converter transformer can be caused due to the fact that the temperature rise of the converter transformer exceeds the standard. When power electronic equipment such as a rectifier and an inverter in a high-voltage direct-current transmission system operates, a large amount of harmonic components are generated, and therefore, when the loss power of a converter transformer is calculated, the influence of the harmonic components must be considered. However, it is difficult to measure the power loss of the converter transformer directly by using equipment and instruments such as a harmonic power supply. In view of this, it is necessary to study the variation law of the loss power of the converter transformer under different excitation frequencies.
At present, domestic converter transformer manufacturers mainly adopt fitting formulas recommended in IEC 61378-2 and GB/T18494.2 standards to calculate the loss power of each component of the converter transformer. However, the fitting formulas recommended in these standards are based on experimental tests of industrial transformers. However, the capacity of the converter transformer used at present greatly exceeds that of the industrial transformer, and the two transformers have different structures, so that a calculation result obtained according to a fitting formula recommended by the standard and an actual measurement result of the loss power of the converter transformer have a large error. In order to improve the calculation accuracy of the converter transformer loss power, a fitting formula recommended in the existing standard needs to be corrected. The results of experimental tests on the harmonic loss power of several different types of converter transformers by J.A.CForrest, yidriim, fuchs and the like under small current show that the harmonic loss power of the converter transformers is basically in direct proportion to the square of harmonic frequency. Some researchers have pointed out that the eddy current loss power of a converter transformer is not only related to the excitation frequency, but also needs to consider the shape and size of the winding wire. Aiming at the problem that the deviation is large when the fitting formula recommended in the standard is used for calculating the high-frequency eddy current loss power of the converter transformer, analysis shows that the A.E. Emanuel et al neglects the influence of the skin effect, and further provides a correction factor. Zhanliang county et al proposed a harmonic loss power correction factor based on finite element simulation results to correct the calculation results. The experimental result shows that after the harmonic loss power factor is used for correction, the calculation result is closer to the result of finite element simulation than the calculation according to the fitting formula recommended by the two standards, but the error is still larger under high frequency. And J.A.Ferreira proposes a mathematical model for representing the skin effect influence by using the effective flow area, but the mathematical model is only a one-dimensional model and is not suitable for calculating the loss power of the winding flat section wire of the converter transformer. The Liuasian blue deduces a calculation formula of the eddy current loss power of the converter transformer winding, and provides a correction factor for representing the skin effect, which is more consistent to the condition that the cross section width of the flat wire of the converter transformer winding is smaller, but is not suitable for calculating the eddy current loss power of the converter transformer winding when the flat wire is wider.
Disclosure of Invention
The present invention provides a correction method and an electronic device considering the frequency characteristic of the eddy current loss power, which can significantly improve the accuracy of the correction factor and simplify the problem, thereby increasing the calculation speed and reducing the consumption of the calculation resources.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a correction method considering the frequency characteristic of eddy current loss power, which comprises the following steps:
s1, building a numerical calculation model of a Helmholtz coil and a converter transformer winding lead;
s2, setting various parameters of the winding wire in the model according to the converter transformer data;
s3, applying excitation current to the Helmholtz coil from low frequency to high frequency;
s4, changing the width and the height of the cross section of the winding wire of the converter transformer;
and S5, integrating the S2, the S3 and the S4, drawing a characteristic curve of the change of the correction quantity of the eddy current loss power frequency characteristic of the converter transformer, and analyzing the correction precision.
Further, the numerical calculation model of the helmholtz coil is as follows: :
establishing two identical coils and keeping the two coils parallel; the distance between the circle centers of the two coils is set as the radius of the coils;
the numerical calculation model of the converter transformer winding wire is as follows: a copper block is placed in the center of both of the coil spaces.
Further, the current directions in the two coils are consistent and the current magnitude is the same.
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 frequency of the exciting current as follows:
when the width of the converter transformer winding lead is less than 5mm, the height of the converter transformer winding lead has no influence on a curve of eddy current loss power changing along with harmonic frequency;
when the width of the converter transformer winding wire is larger than 5mm, the eddy current loss power begins to generate difference on the height value of the converter transformer winding wire, and the difference of the obtained eddy current loss power reaches 20% under high-order harmonics.
Further, after values of the section eddy current loss power of the winding wire of the converter transformer under different excitation frequencies are obtained through simulation, the correction amount is as follows:
wherein, P WEh Power is lost for eddy currents; p WE1 Power is lost for eddy currents; f. of 1 Is the fundamental frequency, is 50Hz; f. of h At the frequency of the h harmonic.
Further, an electronic device comprising: one or more processors; a storage device to store one or more programs that, when executed by the one or more processors, cause the one or more processors to implement a correction method that takes into account eddy current loss power frequency characteristics.
Further, a computer program is stored thereon, wherein the computer program, when executed by a processor, implements a correction method that takes into account eddy current loss power frequency characteristics.
The invention has the beneficial effects that: according to the method for correcting the frequency characteristic of the eddy current loss power of the converter transformer, the correction quantity of the frequency characteristic of the eddy current loss power of the winding wire of the converter transformer caused by the skin effect is equivalently obtained by utilizing the rule that the eddy current loss power generated by a single winding conductor in a Helmholtz coil magnetic field changes along with the frequency of the excitation current, and the correction quantity is compared with the correction method in the literature. Theoretical and numerical analysis showed: the method provided by the invention is more in line with the physical characteristic that the leakage flux of the converter transformer generates 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 very wide application prospect.
Drawings
FIG. 1 is a block diagram of a correction method of the present invention that takes into account the frequency characteristics of the eddy current loss power;
FIG. 2 is a schematic diagram of the magnetic field distribution produced by a current-carrying Helmholtz coil in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a characteristic curve of the average eddy current loss power of a winding wire cross section of an embodiment as a function of excitation current frequency and winding wire size;
FIG. 4 is a schematic diagram of comparison of different converter transformer eddy current loss power model calculations;
FIG. 5 is a schematic diagram of a typical excitation current waveform and its frequency spectrum for a converter transformer;
fig. 6 is a schematic diagram showing comparison of harmonic eddy current loss power calculated by different methods under a typical excitation current waveform of a converter transformer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 to 6, a method for correcting a frequency characteristic considering an eddy current loss power includes the following steps:
s1, building a numerical calculation model of a Helmholtz coil and a converter transformer winding lead;
s2, setting various parameters of a winding wire in the model according to converter transformer data provided by a manufacturer;
s3, applying excitation current to the Helmholtz coil from low frequency to high frequency, and analyzing the frequency characteristic of the eddy current loss power of the lead in the generated magnetic field;
s4, changing the width and the height of the cross section of the winding wire of the converter transformer, and analyzing the influence of the geometric parameters of the winding wire on the eddy current loss power frequency characteristic of the converter transformer;
and S5, integrating the simulation calculation result, drawing a characteristic curve of the change of the eddy current loss power frequency characteristic correction quantity of the converter transformer, and analyzing the correction precision, specifically referring to FIG. 2.
The numerical calculation model of the Helmholtz coil is as follows:
establishing two identical coils and keeping the two coils parallel; the distance between the circle centers of the two coils is set as the radius of the coils;
the numerical calculation model of the converter transformer winding wire is as follows: a copper block is placed in the center of both of the coil spaces.
The current direction in the two coils is consistent and the current magnitude is the same.
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 follows:
when the width of the converter transformer winding lead is less than 5mm, the height of the converter transformer winding lead has little influence on a curve of the eddy current loss power changing along with the harmonic frequency;
when the width value of the converter transformer winding wire is larger than 5mm, the eddy current loss power is sensitive to the height value of the converter transformer winding wire, and the difference of the obtained eddy current loss power reaches 20% under higher harmonics.
After the values of the section eddy current loss power of the winding wire of the converter transformer under different excitation frequencies are obtained through simulation, the correction quantity is as follows:
wherein, P WEh Power is lost for eddy currents; p WE1 Power is lost for eddy currents; f. of 1 Is the fundamental frequency, is 50Hz; f. of h At the frequency of the h harmonic.
An electronic device, comprising: one or more processors; a storage device to store one or more programs that, when executed by the one or more processors, cause the one or more processors to implement a correction method that takes into account eddy current loss power frequency characteristics.
A computer-readable storage medium, on which a computer program is stored, wherein the computer program, when being executed by a processor, implements a correction method taking into account an eddy current loss power frequency characteristic. The first embodiment is as follows:
and (3) building a simulation model of the Helmholtz coil and the winding wire in electromagnetic field numerical calculation software, and setting a proper boundary condition.
The finite element simulation software used in the examples was Ansoft Maxwell.
The actual winding wire parameters may be set according to converter transformer parameters provided by the manufacturer.
According to the measurement standard IEC-61378-2 of the eddy current loss power of the converter transformer, the excitation current of the Helmholtz coil is set, and the frequency characteristic of the eddy current loss power of the winding lead is analyzed.
In the embodiment, the frequency of the single excitation current is 50Hz,100Hz, \8230;, 1250Hz sequentially, namely from the fundamental wave to the 25 th harmonic wave.
In an embodiment, the excitation current of the helmholtz coil may be set to a combined waveform of harmonic components 6h ± 1 (h =1,2,3, 4) according to a typical current carrying waveform of the converter transformer.
And (3) integrating numerical calculation results, drawing a change characteristic curve of the eddy current loss power frequency characteristic correction quantity of the converter transformer, comparing results of different methods, and analyzing the correction precision of the method.
The calculation models selected for mutual comparison in the embodiment comprise IEC 61378-2 model, GB/T18494.2 model and Emanuel correction model delta Emanuel And a correction model Delta proposed by Liu' an et al HUST 。
The calculation formula of the IEC 61378-2 model and the GB/T18494.2 model is as follows:
wherein, I 1 Is the rated current of the converter transformer; i is h The root mean square value of the h-th harmonic current; p WE1 Is the eddy current power loss of the winding wire at fundamental frequency; p WEh Eddy current power loss for h harmonic currents; f. of 1 Is fundamental frequency which is 50Hz in the power grid of China; f. of h At the frequency of the h harmonic.
Δ Emanuel And Δ HUST The calculation formulas of (A) and (B) are respectively as follows:
wherein a is the width of the cross section of the winding flat wire;
is the inverse of the skin depth (ω =2 π f is the harmonic frequency; ρ is the electrical conductivity of the winding wire material; μ is the magnetic permeability of the winding wire material).
And the correction quantity obtained by numerical calculation is used for correcting the result obtained by calculation according to the current standard. The correction factor of the present invention can be expressed as:
wherein, P WE1 Is the eddy current loss power of the converter transformer winding wire at the fundamental frequency; p WEh The power is the eddy current loss power of h-order harmonic current, and the power is the numerical simulation calculation result of a calculation model.
Considering the correction amount, the eddy current loss power generated by the single harmonic can be generally rewritten as
Comparing the obtained correction model with the measurement and calculation results of other correction methods under the condition of typical converter transformer current waveform, and according to the simulation calculation results, the correction method of the converter transformer eddy current loss power frequency characteristics based on the finite element model has higher accuracy compared with other correction models. For example, under the condition that the cross-section width a =10mm of the winding flat wire, the total eddy current loss power obtained by using IEC and GB/T models is 3.1445pu, the total eddy current loss power obtained by using the Emanuel method is 2.8628pu, and the total eddy current loss power obtained by using the HUST method is 1.6062pu, while the total eddy current loss power obtained by using the equivalent method proposed herein is 2.4428pu (b =6 mm) and 2.3291pu (b =8 mm).
Therefore, the proposed correction model can comprehensively consider the influence of the width and height of the cross section of the flat wire of the converter transformer winding on the eddy current loss power, overcomes the problem that the correction error is larger because only a one-dimensional model can be considered in an analytic method, and has guiding significance for more accurately evaluating the energy efficiency of the converter transformer.
The above-mentioned embodiments only express the implementation manner of the present invention, and the description thereof is specific and detailed, but not to be understood as the limitation of the patent scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent should be defined by the appended claims.
Claims (7)
1. A correction method taking into account an eddy current loss power frequency characteristic, characterized by comprising the steps of:
s1, building a numerical calculation model of a Helmholtz coil and a converter transformer winding lead;
s2, setting various parameters of the winding wire in the model according to the converter transformer data;
s3, applying excitation current to the Helmholtz coil from low frequency to high frequency;
s4, changing the width and the height of the cross section of the winding wire of the converter transformer;
and S5, integrating the S2, the S3 and the S4, and drawing the eddy current loss power frequency characteristic of the converter transformer.
2. The method of claim 1, wherein the helmholtz coil is numerically modeled to take into account eddy current loss power frequency characteristics as follows: :
establishing two identical coils and keeping the two coils parallel; the distance between the circle centers of the two coils is set as the radius of the coils;
the numerical calculation model of the converter transformer winding wire is as follows: a copper block is placed in the center of both of the coil spaces.
3. A correction method taking into account the frequency characteristic of eddy current loss power according to claim 2, characterized in that: the current direction in the two coils is consistent and the current magnitude is the same.
4. The method according to claim 1, wherein the average value of the eddy current loss power in the winding wire of the converter transformer is changed along with the excitation current frequency by changing the width and height of the cross section of the winding wire of the converter transformer according to the following formula:
when the width of the converter transformer winding lead is less than 5mm, the height of the converter transformer winding lead does not influence the curve of the eddy current loss power changing along with the harmonic frequency
When the width of the converter transformer winding wire is larger than 5mm, the eddy current loss power begins to generate difference on the height value of the converter transformer winding wire, and the difference of the obtained eddy current loss power reaches 20% under high-order harmonics.
5. The method according to claim 4, wherein the correction method takes into account a frequency characteristic of eddy current loss power: after the values of the section eddy current loss power of the winding wire of the converter transformer under different excitation frequencies are obtained through simulation, the correction quantity is as follows:
wherein, P WEh Power is lost for eddy currents; p WE1 Power is lost for eddy currents; f. of 1 Fundamental frequency, 50Hz; f. of h At the frequency of the h harmonic.
6. 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 the correction method taking into account eddy current loss power frequency characteristics as claimed in any one of claims 1 to 5.
7. A computer-readable storage medium, having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the correction method considering the frequency characteristic of the eddy current loss power according to any one of claims 1 to 5.
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| CN116929971A (en) * | 2023-09-15 | 2023-10-24 | 合肥工业大学 | Electromagnetic force load applying and impact current generating platform based on Helmholtz coil |
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| CN116929971A (en) * | 2023-09-15 | 2023-10-24 | 合肥工业大学 | Electromagnetic force load applying and impact current generating platform based on Helmholtz coil |
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