CN112305475A - Method and device for detecting loss-of-field state of permanent magnet - Google Patents
Method and device for detecting loss-of-field state of permanent magnet Download PDFInfo
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- CN112305475A CN112305475A CN202011137043.6A CN202011137043A CN112305475A CN 112305475 A CN112305475 A CN 112305475A CN 202011137043 A CN202011137043 A CN 202011137043A CN 112305475 A CN112305475 A CN 112305475A
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- 238000000034 method Methods 0.000 title claims abstract description 25
- 230000005389 magnetism Effects 0.000 claims abstract description 17
- 230000004907 flux Effects 0.000 claims description 27
- 238000013178 mathematical model Methods 0.000 claims description 10
- 238000004364 calculation method Methods 0.000 claims description 9
- 230000001360 synchronised effect Effects 0.000 claims description 9
- 238000000418 atomic force spectrum Methods 0.000 claims description 6
- 238000000354 decomposition reaction Methods 0.000 claims description 6
- 238000001514 detection method Methods 0.000 claims description 4
- 230000005347 demagnetization Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 3
- 230000005284 excitation Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
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- Condensed Matter Physics & Semiconductors (AREA)
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- Control Of Electric Motors In General (AREA)
- Tests Of Circuit Breakers, Generators, And Electric Motors (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
The invention relates to a method and a device for detecting loss of magnetism of a permanent magnet, which are applied to a permanent magnet generator. According to the method and the device for detecting the loss of magnetism of the permanent magnet, the problem that the permanent magnet cannot be judged after loss of magnetism is solved.
Description
Technical Field
The invention belongs to the field of permanent magnet motors, and particularly relates to a method and a device for detecting loss of field of a permanent magnet.
Background
The permanent magnet motor is also called as a permanent magnet synchronous motor, along with the rapid development and continuous improvement of the performance of a permanent magnet material, the performance of the permanent magnet motor can be further improved, compared with the common motor, the permanent magnet motor has the advantages of high efficiency, energy conservation, low temperature rise, good starting performance, small size, light weight and the like, and is widely applied to the fields of aviation, electric vehicles, robots and the like. However, the permanent magnet material has a demagnetization characteristic, and when a high temperature of more than 150 ℃ occurs or the carrier frequency of the frequency converter is low, the permanent magnet is demagnetized, so that brake failure, control system overcurrent, further rapid expansion of the demagnetization and other problems occur.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a method and a device for detecting loss of magnetism of a permanent magnet, so that the problem of online loss of magnetism judgment of a permanent magnet motor is solved.
In order to realize the technical problem, the invention adopts the following technical scheme:
a method for detecting a loss-of-field state of a permanent magnet, the permanent magnet being applied to a permanent magnet motor, the method comprising:
calculating instantaneous back electromotive force and drawing a back electromotive force curve graph;
obtaining a flux linkage oscillogram by integrating the back electromotive force curve graph;
carrying out Fourier decomposition on the flux linkage oscillogram to obtain a harmonic amplitude and a harmonic frequency;
and judging the demagnetizing quantity of the permanent magnet according to the harmonic amplitude, and calculating the demagnetizing position of the permanent magnet according to the frequency of harmonic occurrence.
Optionally, the method of calculating the instantaneous back emf comprises:
establishing a mathematical model through the terminal voltage, the stator resistance, the current and the reactance of the motor;
and calculating the instantaneous back electromotive force through the established mathematical model.
Optionally, the calculation rule of the mathematical model is:
Usinθ＝IqXq+IdR1
Ucosθ＝E0-IdXd+IqR1
wherein U is a voltage, E0Is a counter electromotive force, R1Is a stator electric group, IdFor direct axis current, IqIs a quadrature current, XdIs a direct-axis synchronous reactance, XqIs quadrature axis synchronous reactance, theta is the angle with the direct axis.
Optionally, the calculation rule of the fourier transform is:
in a whole period, selecting equidistant N nodes, such as:
wherein aj and bj are coskx and coskx coefficients after Fourier decomposition.
Optionally, the method for judging the amount of demagnetization of the permanent magnet according to the amplitude of the fundamental wave includes:
and obtaining the flux linkage waveform of the permanent magnet demagnetizing quantity through the measured voltage and current values and known resistance and reactance values, and judging the demagnetizing quantity through the amplitude of the fundamental wave.
Optionally, the method for calculating the field loss position of the permanent magnet according to the number of times of harmonic occurrence includes:
and the magnetic pole is judged to be side-edge magnetic loss by the fifth harmonic, and the magnetic pole is judged to be center magnetic loss by the seventh harmonic.
Optionally, the online detection method further includes:
and when the loss of magnetism of the loss of magnetism position is larger than a set value, automatic alarm is realized.
Optionally, the permanent magnet is applied to a permanent magnet motor, and the device comprises:
an acquisition module: acquiring a flux linkage value of the permanent magnet;
a drawing module: drawing a corresponding flux linkage oscillogram through the flux linkage values;
a calculation module: obtaining harmonic amplitude and harmonic times by Fourier transform of the flux linkage oscillogram;
and judging the demagnetizing quantity of the permanent magnet according to the harmonic amplitude, and calculating the demagnetizing position of the permanent magnet according to the frequency of harmonic occurrence.
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
the permanent magnet field state can be detected in time, technical support is provided for the permanent magnet synchronous generator to take measures in the first time, and the safety risk of the loss of excitation fault to the loss of excitation overload operation of the permanent magnet synchronous generator is reduced.
Other features of the present invention and advantages thereof will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
FIG. 1 is a block flow diagram of a method for detecting a loss of field condition of a permanent magnet according to the present invention;
FIG. 2(a) is a waveform diagram of back electromotive force of the method for detecting a loss-of-field state of a permanent magnet according to the present invention;
FIG. 2(b) a diagram showing a flux linkage waveform after field loss in the method for detecting a field loss state of a permanent magnet according to the present invention
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus consistent with certain aspects of the invention, as detailed in the appended claims.
In order to make those skilled in the art better understand the technical solution of the present invention, the following detailed description of the present invention is provided with reference to the accompanying drawings and examples.
The method for detecting loss of field of the permanent magnet shown in fig. 1 is applied to a permanent magnet motor, and comprises the following steps:
s1, establishing a mathematical model through the motor end voltage, the stator resistance, the current and the reactance, wherein the calculation rule of the mathematical model is as follows:
Usinθ＝IqXq+IdR1
Ucosθ＝E0-IdXd+IqR1
wherein U is a voltage, E0Is a counter electromotive force, R1Is a stator electric group, IdFor direct axis current, IqIs a quadrature current, XdIs a direct-axis synchronous reactance, XqIs quadrature axis synchronous reactance; and obtaining the flux linkage waveform of the demagnetized quantity of the permanent magnet by the measured voltage and current values and the known resistance and reactance values.
And S2, calculating the instantaneous back electromotive force through the established mathematical model and drawing a back electromotive force curve graph.
S3, integrating the back electromotive force curve graph to obtain a flux linkage waveform graph;
s4, carrying out Fourier decomposition on the flux linkage oscillogram to obtain a harmonic amplitude and a harmonic number; the calculation rule of the Fourier transform is as follows:
in a whole period, selecting equidistant N nodes, such as:
wherein aj and bj are coskx and coskx coefficients after Fourier decomposition.
And judging the demagnetization quantity of the permanent magnet according to the harmonic amplitude, calculating the demagnetization position of the permanent magnet according to the occurrence frequency of the harmonic, judging that the magnetic pole is side demagnetization by fifth harmonic, and judging that the magnetic pole is magnetic pole center demagnetization by seventh harmonic. And when the loss of magnetism of the loss of magnetism position is larger than a set value, automatic alarm is realized.
A detection device for a loss-of-field state of a permanent magnet, the permanent magnet being applied to a permanent magnet motor, the device comprising:
an acquisition module: acquiring a flux linkage value of the permanent magnet;
a drawing module: drawing a corresponding flux linkage oscillogram through the flux linkage values;
a calculation module: obtaining fundamental wave amplitude and harmonic times by Fourier transform of the flux linkage oscillogram;
and judging the demagnetizing quantity of the permanent magnet according to the harmonic amplitude, and calculating the demagnetizing position of the permanent magnet according to the frequency of harmonic occurrence.
The specific working process is as follows: establishing a mathematical model, outputting the counter electromotive force waveform by detecting the voltage, the current and the rotating speed, and comparing the voltage, the current and the rotating speedThe back electromotive force oscillogram is subjected to Fourier transform to establish a flux linkage oscillogram, flux linkage amplitude and harmonic content are obtained through Fourier analysis, the current of a motor loop is increased after a permanent magnet is demagnetized, temperature rise is increased, and the back electromotive force of the system is greatly reduced, and by taking the figure 2 as an example, the magnetic field waveform can be obtained through the integral of the voltage waveform, and the demagnetized state can be obtained through the analysis of the flux linkage oscillogram. Testing flux linkage by measuring voltage U and current Id、Iq、Xd、Xq、R1Calculate E0Through E0And integrating to obtain a flux linkage waveform, judging the loss of magnetism of the permanent magnet according to the amplitude of the harmonic wave, calculating the loss of magnetism position of the permanent magnet according to the occurrence frequency of the harmonic wave when the amplitude is larger, judging that the magnetic pole is side loss of magnetism by fifth harmonic wave, and judging that the magnetic pole is center loss of magnetism by seventh harmonic wave. And when the loss of magnetism of the loss of magnetism position is larger than a set value, automatic alarm is realized.
The foregoing are merely exemplary embodiments of the present invention, which enable those skilled in the art to understand or practice the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention.
It is to be understood that the present invention is not limited to what has been described above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.
Claims (8)
1. A method for detecting the loss-of-field state of a permanent magnet, wherein the permanent magnet is applied to a permanent magnet motor, is characterized by comprising the following steps:
calculating instantaneous back electromotive force through a motor electrical parameter equation and drawing a back electromotive force curve graph;
obtaining a flux linkage oscillogram by integrating the back electromotive force curve graph;
carrying out Fourier decomposition on the flux linkage oscillogram to obtain a harmonic amplitude and a harmonic frequency;
and judging the demagnetizing quantity of the permanent magnet according to the harmonic amplitude, and calculating the demagnetizing position of the permanent magnet according to the frequency of harmonic occurrence.
2. The method for detecting the loss of field condition of a permanent magnet according to claim 1, wherein the method for calculating the instantaneous back electromotive force comprises:
establishing a mathematical model through the terminal voltage, the stator resistance, the current and the reactance of the motor;
and calculating the instantaneous back electromotive force through the established mathematical model.
3. The method for detecting the loss of field condition of the permanent magnet according to claim 2, wherein the mathematical model has the calculation rule that:
U sinθ＝IqXq+IdR1
U cosθ＝E0-IdXd+IqR1
wherein U is a voltage, E0Is a counter electromotive force, R1Is a stator electric group, IdFor direct axis current, IqIs a quadrature current, XdIs a direct-axis synchronous reactance, XqThe angle between theta and the straight axis is the quadrature axis synchronous reactance.
4. The method for detecting the loss of field of a permanent magnet according to claim 1, wherein the calculation rule of the fourier transform is as follows:
in a whole period, selecting equidistant N nodes, such as:
wherein aj and bj are coskx and coskx coefficients after Fourier decomposition.
5. The method for detecting the loss of field of the permanent magnet according to claim 1, wherein the method for judging the loss of field of the permanent magnet according to the harmonic amplitude comprises the following steps:
and obtaining the flux linkage waveform of the permanent magnet demagnetizing quantity through the measured voltage and current values and known resistance and reactance values, and judging the demagnetizing quantity through the amplitude of the fundamental wave.
6. The method for detecting the loss of field of a permanent magnet according to claim 1, wherein the method for calculating the loss of field of the permanent magnet according to the number of harmonic waves comprises:
and the magnetic pole is judged to be side-edge magnetic loss by the fifth harmonic, and the magnetic pole is judged to be center magnetic loss by the seventh harmonic.
7. The on-line detection method applied to permanent magnet field loss according to claim 1, further comprising:
and when the loss of magnetism of the loss of magnetism position is larger than a set value, automatic alarm is realized.
8. A detection device for a loss-of-field state of a permanent magnet, wherein the permanent magnet is applied to a permanent magnet motor, the device comprising:
an acquisition module: acquiring a flux linkage value of the permanent magnet;
a drawing module: drawing a corresponding flux linkage oscillogram through the flux linkage values;
a calculation module: obtaining harmonic amplitude and harmonic times by Fourier transform of the flux linkage oscillogram;
and judging the demagnetizing quantity of the permanent magnet according to the harmonic amplitude, and calculating the demagnetizing position of the permanent magnet according to the frequency of harmonic occurrence.
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