A method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization intensity waveform

Abstract

The present invention proposes a method for measuring the alternating current magnetic properties of magnetic materials by improving the sinusoidality of the magnetic polarization intensity waveform, which belongs to the technical field of magnetic material magnetic property measurement. It can solve the technical problems that the method of improving the sinusoidality of the magnetic polarization intensity waveform through a programmable input power supply is difficult to ensure that a good measurement effect is maintained at different measurement points, the measurement process takes a long time, and it is difficult to achieve ideal measurement conditions. The technical scheme includes the following steps: measuring the current value of the primary coil, and obtaining the frequency, angle and third harmonic current angle of the fundamental current; measuring the induced voltage value of the secondary coil, and obtaining the virtual axis induced voltage value of the secondary coil; extracting the harmonic components in the induced voltage of the secondary coil; calculating the third harmonic voltage value that needs to be compensated in the primary coil input voltage, and outputting it through a programmable power supply. The present invention can be applied to improving the sinusoidality of the magnetic polarization intensity waveform in the measurement of the alternating current magnetic properties of magnetic materials.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic material magnetic property measurement, and in particular relates to a magnetic material AC magnetic property measurement method for improving the sinusoidality of magnetic polarization intensity waveform. Background Art

[0002] With the emergence of new magnetic materials, accurate magnetic property measurement is of great significance for the research and development of magnetic materials. The commonly used magnetic property measurement methods of magnetic materials are mainly implemented according to the requirements of the National Standard of the People's Republic of China GB / T3655-2022 "Method for measuring the magnetic properties of electrical steel strips (sheets) using Epstein square rings". This standard requires that the measurement of the AC magnetic properties of magnetic materials should be carried out at a given peak value of magnetic polarization intensity (or peak value of magnetic field intensity) and a given frequency and sinusoidal induced voltage, so as to obtain more accurate AC magnetic properties of magnetic materials.

[0003] As a magnetic material frequently used in electromagnetic devices, it has the characteristics of magnetic saturation (nonlinearity), hysteresis, and conductivity. When the Epstein square circle method is used for measurement, in order to improve the sinusoidality of the induced voltage, the sinusoidality of the magnetic polarization intensity waveform needs to be improved; however, due to the influence of magnetic saturation, in addition to the sine fundamental component, the primary coil current will generate a third harmonic current component (the amplitude of the third harmonic current is related to the peak value of the magnetic polarization intensity and the degree of magnetic saturation); when the primary coil input voltage is a standard sinusoidal voltage, due to the influence of the voltage drop of the input power supply internal resistance and the primary coil resistance and the leakage inductance voltage drop of the primary coil, the voltage drop generated by the third harmonic current in the primary coil current causes harmonic components to appear in the magnetic polarization intensity and the induced voltage, thereby causing deviations in the measurement of the AC magnetic properties of the magnetic material, affecting the accuracy of the magnetic properties of the magnetic material.

[0004] Therefore, it is necessary to seek a method for measuring the AC magnetic properties of magnetic materials that can improve the sinusoidality of the magnetic polarization intensity waveform, reduce the influence of the non-sinusoidal induced voltage on the measurement results, thereby improving the measurement accuracy of the AC magnetic properties of magnetic materials, and obtaining more accurate magnetic properties of magnetic materials, especially new magnetic materials, laying the foundation for the research and development of magnetic materials.

[0005] At present, the commonly used method for improving the sinusoidal degree of the magnetic polarization intensity waveform is mainly realized by programmable input power supply, and harmonic voltages of different orders and sizes are injected into the input voltage to compensate for the influence of the voltage drop of each part, so as to improve the sinusoidal degree of the magnetic polarization intensity waveform. The specific implementation method is as follows: according to the parameters of the designed Epstein square circle, such as the total resistance of the magnetizing circuit, the parameters of the primary and secondary coils, the theoretical calculation results of different magnetic field conditions are obtained to obtain the required input power waveform to improve the sinusoidal degree of the magnetic polarization intensity waveform. This method is an open-loop method, and its measurement accuracy is affected by the accuracy of the Epstein square circle parameters. The Epstein square circle parameters will change at different measurement points, so it is difficult to ensure that a good measurement effect is maintained at different measurement points; moreover, in order to improve the sinusoidal degree of the magnetic polarization intensity waveform at different measurement points, it is necessary to adjust the input voltage waveform multiple times, so that it takes a long time to complete the measurement, and it is also difficult to achieve a more ideal measurement condition.

[0006] In order to solve the above problems, the present invention proposes a method for measuring the AC magnetic properties of magnetic materials by improving the sinusoidality of the magnetic polarization intensity waveform. Summary of the invention

[0007] The present invention aims at the technical problems that the method for improving the sinusoidality of the magnetic polarization intensity waveform by using a programmable input power supply is difficult to ensure that a good measurement effect is maintained at different measurement points, the measurement process takes a long time, and it is also difficult to achieve ideal measurement conditions. A method for measuring the AC magnetic properties of magnetic materials by improving the sinusoidality of the magnetic polarization intensity waveform is proposed. The closed-loop method is formed by using the harmonic component in the secondary coil induced voltage as the feedback quantity to realize compensation for the third harmonic input voltage, effectively suppress the harmonic component of the secondary coil induced voltage, improve the magnetic polarization intensity and the sinusoidality of the secondary coil induced voltage, and automatically follow the compensation according to the changes in the measuring point, thereby effectively improving the measurement accuracy of the AC magnetic properties of the magnetic material. The method is particularly suitable for the application field of realizing the rapid and accurate measurement of the AC magnetic properties of magnetic materials at multiple operating points.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is: a method for measuring the magnetic properties of a magnetic material by improving the sinusoidality of a magnetic polarization intensity waveform, comprising the following steps:

[0009] Measure the primary coil current value and obtain the fundamental current frequency, angle and third harmonic current angle;

[0010] Measure the induced voltage value of the secondary coil and obtain the induced voltage value of the virtual axis of the secondary coil;

[0011] Extracting harmonic components from the induced voltage of the secondary coil;

[0012] The third harmonic voltage value that needs to be compensated in the primary coil input voltage is calculated and output through a programmable power supply.

[0013] In some of the embodiments, the measuring of the primary coil current value and obtaining the fundamental current angle and the third harmonic current angle specifically include the following steps: measuring the instantaneous value I1 of the primary coil current through a current sensor, and using a software phase-locked loop to obtain the frequency f1 and angle θ1 of the fundamental current and the third harmonic current angle θ3.

[0014] In some embodiments, the measuring of the secondary coil induced voltage value and obtaining the secondary coil virtual axis induced voltage value specifically include the following steps: measuring the secondary coil induced voltage instantaneous value U2 by a voltage sensor as U2 in the virtual αβ axis induced voltage α , the value of U2 after using the 1 / 4 cycle delay method is used as U in the virtual αβ axis induced voltage β .

[0015] In some embodiments, the extracting of the harmonic component in the induced voltage of the secondary coil specifically comprises the following steps:

[0016] Using U α , U β , θ1 are transformed to the fundamental wave dq synchronous axis system, and the secondary coil induced voltage U is obtained d , U q ;

[0017] U d , U q Perform low-pass filtering to obtain the component U of the secondary coil fundamental voltage in the fundamental dq synchronous axis system d_1 , U q_1 ;

[0018] Using U d_1 , U q_1 , θ1 are transformed to the virtual αβ axis, and the components U of the secondary coil fundamental voltage on the virtual αβ axis are obtained respectively. α_1 , U β_1 ;

[0019] Will U α and U α_1 Subtract, and through effective value calculation and low-pass filtering, the effective value U of the harmonic component in the secondary coil induced voltage is obtained. 2_3_RMS .

[0020] In some embodiments, the secondary coil induced voltage U d , U q Satisfy

[0021] U d =U α cosθ1+U β sinθ1,

[0022] U q =-U α sinθ1+U β cosθ1.

[0023] In some embodiments, the component U of the secondary coil fundamental voltage on the virtual αβ axis is α_1 , U β_1 Satisfy

[0024] U α_1 =U d_1 cosθ1-U q_1 sinθ1,

[0025] U β_1 =U d_1 sinθ1+U q_1 cosθ1.

[0026] In some embodiments, the calculation of the third harmonic voltage value that needs to be compensated in the primary coil input voltage and outputting it through a programmable power supply specifically includes the following steps:

[0027] Take U 2_3_RMS As the feedback quantity, the PI regulator is used to obtain the third harmonic voltage amplitude U that needs to be compensated in the primary coil input voltage. 1_3_AMP ,

[0028] Obtain the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage 1_3 ,

[0029] Through the programmable power supply 1_3 It is added to the fundamental component of the primary coil input voltage for output.

[0030] In some embodiments, the instantaneous value U of the third harmonic voltage to be compensated in the primary coil input voltage 1_3 Meet U 1_3 =U 1_3_AMP sinθ3,

[0031] Among them, U 1_3_AMP =(K p +K I / s)×(0-U 2_3_RMS ), where K p is the proportional coefficient of the PI regulator, K I is the integral coefficient of the PI regulator.

[0032] Compared with the prior art, the advantages and positive effects of the present invention are:

[0033] (1) The present invention provides a method for measuring the AC magnetic properties of magnetic materials that improves the sinusoidality of the magnetic polarization intensity waveform. The method uses the harmonic component in the secondary coil induced voltage as a feedback quantity to form a closed loop to achieve compensation for the third harmonic input voltage, effectively suppress the harmonic component of the secondary coil induced voltage, improve the magnetic polarization intensity and the sinusoidality of the secondary coil induced voltage, and automatically follow the compensation according to the changes in the measuring point, thereby effectively improving the measurement accuracy of the AC magnetic properties of the magnetic material.

[0034] (2) The method for measuring the AC magnetic properties of magnetic materials with improved sinusoidality of the magnetic polarization intensity waveform provided by the present invention can effectively and automatically generate compensation voltage according to the needs of different test points, thus solving the accuracy problem of compensation voltage calculation in traditional methods.

[0035] (3) The method for measuring the AC magnetic properties of magnetic materials with improved sinusoidality of the magnetic polarization intensity waveform provided by the present invention has the characteristic of fast following, which effectively reduces the time required for the measurement process and realizes fast measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A control block diagram of a method for measuring AC magnetic properties of magnetic materials for improving the sinusoidality of a magnetic polarization intensity waveform provided by an embodiment of the present invention;

[0037] Figure 2 This is a waveform diagram of the secondary coil induced voltage when the input voltage is 6.6V in amplitude and 60Hz in frequency as the fundamental voltage in Example 1;

[0038] Figure 3 This is a Fourier analysis result diagram of Example 1 when the input voltage is a fundamental voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0039] Figure 4 This is a primary coil current waveform diagram of Example 1 when the input voltage is 6.6V in amplitude and 60Hz in frequency;

[0040] Figure 5 This is a Fourier analysis result diagram of Example 1 when the input voltage is a fundamental voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0041] Figure 6 This is a waveform diagram of the third harmonic component of the compensated input voltage when the input voltage is a fundamental voltage with an amplitude of 6.6V and a frequency of 60Hz in Example 1;

[0042] Figure 7 This is a waveform diagram of the secondary coil induced voltage when the input voltage is 5V in amplitude and 60Hz in frequency as the fundamental voltage in Example 1;

[0043] Figure 8This is a Fourier analysis result diagram of Example 1 when the input voltage is a fundamental voltage with an amplitude of 5V and a frequency of 60Hz;

[0044] Fig. 9 This is a primary coil current waveform diagram of Example 1 when the input voltage is a fundamental voltage with an amplitude of 5V and a frequency of 60Hz;

[0045] Fig.10 This is a Fourier analysis result diagram of Example 1 when the input voltage is a fundamental voltage with an amplitude of 5V and a frequency of 60Hz;

[0046] Fig.11 This is a waveform diagram of the compensated third harmonic component of the input voltage when the input voltage is the fundamental voltage with an amplitude of 5V and a frequency of 60Hz in Example 1.

[0047] Fig.12 This is a waveform diagram of the secondary coil induced voltage when the input voltage of comparative example 1 is a standard sinusoidal voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0048] Fig.13 This is the Fourier analysis result diagram of comparative example 1 when the input voltage is a standard sinusoidal voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0049] Fig.14 This is the primary coil current waveform diagram when the input voltage of comparative example 1 is a standard sinusoidal voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0050] Fig.15 This is the Fourier analysis result diagram of comparative example 1 when the input voltage is a standard sinusoidal voltage with an amplitude of 6.6V and a frequency of 60Hz;

[0051] Fig.16 This is a waveform diagram of the secondary coil induced voltage when the input voltage of comparative example 1 is a standard sinusoidal voltage with an amplitude of 5V and a frequency of 60Hz;

[0052] Fig.17 This is the Fourier analysis result diagram of comparative example 1 when the input voltage is a standard sinusoidal voltage with an amplitude of 5V and a frequency of 60Hz;

[0053] Fig.18 This is the primary coil current waveform diagram when the input voltage of comparative example 1 is a standard sinusoidal voltage with an amplitude of 5V and a frequency of 60Hz;

[0054] Fig.19 This is the Fourier analysis result diagram of comparative example 1 when the input voltage is a standard sinusoidal voltage with an amplitude of 5V and a frequency of 60Hz. DETAILED DESCRIPTION

[0055] In order to be able to understand the characteristics and technical contents of the embodiments of the present invention in more detail, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the embodiments described below are only part of the embodiments of the present invention, rather than all the embodiments of the present invention. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection requested by the present invention.

[0056] The embodiment of the present invention provides a magnetic material magnetic property measurement method for improving the sinusoidality of the magnetic polarization intensity waveform, which realizes compensation of the third harmonic input voltage by using the harmonic component in the secondary coil induced voltage as feedback quantity to form a closed loop mode; measures the primary coil current, obtains the fundamental current angle and the third harmonic current angle through a software phase-locked loop; measures the secondary coil induced voltage, extracts the harmonic component in the secondary coil induced voltage; uses the harmonic component in the secondary coil induced voltage as feedback quantity to form a PI regulator to obtain the instantaneous value of the third harmonic input voltage, and outputs it through a programmable power supply. The magnetic material AC magnetic property measurement method for improving the sinusoidality of the magnetic polarization intensity waveform provided by the present invention realizes compensation of the third harmonic input voltage, effectively suppresses the harmonic component of the secondary coil induced voltage, improves the sinusoidality of the magnetic polarization intensity and the secondary coil induced voltage, and automatically follows the compensation according to the change of the measuring point, effectively improving the measurement accuracy of the AC magnetic property of the magnetic material, and is particularly suitable for the application field of realizing the AC magnetic property measurement of magnetic materials quickly and accurately at multiple operating points. The method specifically includes the following steps:

[0057] S1, measure the instantaneous value I1 of the primary coil current through the current sensor, and use the software phase-locked loop (PLL) to obtain the frequency f1 and angle θ1 of the fundamental current and the angle θ3 of the third harmonic current;

[0058] S2, measure the instantaneous value U2 of the secondary coil induced voltage through the voltage sensor, as U in the virtual αβ axis induced voltage α , delay U2 by 1 / 4f1 time (1 / 4 cycle delay method) as U in the virtual αβ axis induced voltage β ;

[0059] S3. Extract the harmonic component U in the secondary coil induced voltage 2_3 , the steps are as follows:

[0060] S31. Using U α , U β , θ1 are transformed to the fundamental wave dq synchronous axis system, and the secondary coil induced voltage U is obtained d , Uq ,in,

[0061] U d =U α cosθ1+U β sinθ1,

[0062] U q =-U α sinθ1+U β cosθ1;

[0063] S32. Since the fundamental wave component of the secondary coil induced voltage is a DC quantity in the fundamental wave dq synchronous axis system, U d , U q Perform low-pass filtering to obtain the component U of the secondary coil fundamental voltage in the fundamental dq synchronous axis system d_1 , U q_1 ;

[0064] S33. Use U d_1 , U q_1 , θ1 are transformed to the virtual αβ axis, and the components U of the secondary coil fundamental voltage on the virtual αβ axis are obtained respectively. α_1 , U β_1 ,in,

[0065] U α_1 =U d_1 cosθ1-U q_1 sinθ1,

[0066] U β_1 =U d_1 sinθ1+U q_1 cosθ1;

[0067] S34. Will U α and U α_1 Subtracting them, we can get the instantaneous value U of the harmonic component in the secondary coil induced voltage. 2_3 ,in,

[0068] U 2_3 =U α -U α_1 ;

[0069] S35, by U 2_3 Through effective value calculation and low-pass filtering, the effective value U of the harmonic component in the secondary coil induced voltage is obtained. 2_3_RMS ;

[0070] S4. Calculate the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage 1_3 , through the programmable power supply U 1_3It is added to the fundamental component of the primary coil input voltage for output to achieve the suppression of the harmonic voltage of the secondary coil induced voltage. The steps are as follows:

[0071] S41, with U 2_3_RMS As the feedback quantity, the PI regulator is used to obtain the third harmonic voltage amplitude U that needs to be compensated in the primary coil input voltage. 1_3_AMP ,

[0072] U 1_3_AMP =(K p +K I / s)ΔU,

[0073] In the formula, K p is the proportional coefficient of the PI regulator, K I is the integral coefficient of the PI regulator, ΔU=0-U 2_3_RMS ;

[0074] S42, by U 1_3_AMP The θ3 obtained in 1) is used to obtain the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage. 1_3 ;

[0075] U 1_3 =U 1_3_AMP sinθ3.

[0076] In order to more clearly and in detail introduce the magnetic material magnetic property measurement method for improving the sinusoidality of the magnetic polarization intensity waveform provided by the embodiment of the present invention, it will be described in conjunction with a specific embodiment below.

[0077] Example 1

[0078] Reference Figure 1 The present embodiment provides a method for measuring the magnetic properties of a magnetic material by improving the sinusoidality of a magnetic polarization intensity waveform, and specifically comprises the following steps:

[0079] S1, measure the instantaneous value I1 of the primary coil current, and use the software phase-locked loop to obtain the frequency f1 and angle θ1 of the fundamental current and the angle θ3 of the third harmonic current;

[0080] S2, measure the instantaneous value of the secondary coil induced voltage U2, as the U in the virtual αβ axis induced voltage α , the delay of 1 / 4f1 time (1 / 4 cycle delay method) is used as the U in the virtual αβ axis induced voltage β ;

[0081] S3. Extract the harmonic component U in the secondary coil induced voltage 2_3 :

[0082] S31. Using U α , U β, θ1 are transformed to the fundamental wave dq synchronous axis system, and the secondary coil induced voltage U is obtained dq ;

[0083] S32, U dq Perform low-pass filtering to obtain the component U of the secondary coil fundamental voltage in the fundamental dq synchronous axis system dq_1 ;

[0084] S33. Use U dq_1 , θ1 are transformed to the virtual αβ axis, and the component U of the secondary coil fundamental voltage on the virtual αβ axis is obtained. αβ_1 ;

[0085] S34. Will U α and U α_1 Subtracting them, we can get the instantaneous value U of the harmonic component in the secondary coil induced voltage. 2_3 ;

[0086] S35, by U 2_3 Through effective value calculation and low-pass filtering, the effective value U of the harmonic component in the secondary coil induced voltage is obtained. 2_3_RMS ;

[0087] S4. Calculate the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage 1_3 , through the programmable power supply U 1_3 Added to the fundamental component of the primary coil input voltage for output:

[0088] S41, with U 2_3_RMS As the feedback quantity, the PI regulator is used to obtain the third harmonic voltage amplitude U that needs to be compensated in the primary coil input voltage. 1_3_AMP ;

[0089] S42, by U 1_3_AMP The θ3 obtained in 1) is used to obtain the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage. 1_3 .

[0090] Reference Figures 2 to 11 As shown in the figure, it is the operation effect diagram of this embodiment, wherein, when the input voltage is 6.6V and the frequency is 60Hz, the secondary coil induced voltage waveform and Fourier analysis result are shown in the attached figure. Figure 2 and Figure 3 As shown, the primary coil current waveform and Fourier analysis results are shown in the attached figure. Figure 4 and Figure 5 The compensated input voltage third harmonic component waveform is shown in the attached figure. Figure 6 As shown;

[0091] When the input voltage is 5V and the frequency is 60Hz, the secondary coil induced voltage waveform and Fourier analysis results are shown in the attached figure. Figure 7 and Figure 8 As shown, the primary coil current waveform and Fourier analysis results are shown in the attached figure. Fig. 9 and Fig.10 The compensated input voltage third harmonic component waveform is shown in the attached figure. Fig.11 shown.

[0092] Comparative Example 1

[0093] This comparative example uses the parameters of the designed Epstein square ring to perform theoretical calculations under different magnetic field conditions to obtain the required input power waveform to improve the sinusoidality of the magnetic polarization intensity waveform.

[0094] Reference Figures 12 to 19 As shown in the figure, it is the operation effect diagram of this comparative example, where the input voltage is a standard sinusoidal voltage with an amplitude of 6.6V and a frequency of 60Hz, the secondary coil induced voltage waveform and Fourier analysis result are shown in the attached figure. Fig.12 and Fig.13 As shown, the primary coil current waveform and Fourier analysis results are shown in the attached figure. Fig.14 and Fig.15 As shown;

[0095] When the input voltage is a standard sinusoidal voltage with an amplitude of 5V and a frequency of 60Hz, the secondary coil induced voltage waveform and Fourier analysis results are shown in the attached figure. Fig.16 and Fig.17 As shown, the primary coil current waveform and Fourier analysis results are shown in the attached figure. Fig.18 and Fig.19 shown.

[0096] By comparing the operating effects of Example 1 with those of Comparative Example 1, it can be found that: Example 1 adopts the magnetic material magnetic property measurement method for improving the sinusoidality of the magnetic polarization intensity waveform of the present invention. After the third harmonic voltage required for changing with the measuring point is injected into the input voltage, the third harmonic voltage in the secondary coil induced voltage is significantly suppressed, the sinusoidality of the secondary coil induced voltage waveform is improved, the harmonic distortion rate is significantly reduced, and the measurement accuracy of the AC magnetic property of the magnetic material is improved; the third harmonic voltage that needs to be injected is also automatically compensated following the measuring point, thereby suppressing the harmonic component of the secondary coil induced voltage, improving the sinusoidality of the secondary coil induced voltage, and improving the measurement accuracy of the AC magnetic property of the magnetic material.

[0097] Finally, it should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only the preferred feasible embodiments of the present invention, and the above-mentioned embodiments are only used to illustrate the technical scheme of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations, modifications, evolutions and improvements made by ordinary technicians in this field to the technical scheme of the present invention should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization intensity waveform, characterized in that: The following steps are involved: Measure the primary coil current value and obtain the fundamental current frequency, angle and third harmonic current angle; Measure the induced voltage value of the secondary coil and obtain the induced voltage value of the virtual axis of the secondary coil; Extracting harmonic components from the induced voltage of the secondary coil; The third harmonic voltage value that needs to be compensated in the primary coil input voltage is calculated and output through a programmable power supply.

2. The magnetic material magnetic property measurement method for improving the sinusoidality of magnetic polarization intensity waveform according to claim 1 is characterized in that: The method of measuring the primary coil current value and obtaining the fundamental current angle and the third harmonic current angle specifically includes the following steps: The instantaneous value I1 of the primary coil current is measured by a current sensor, and the frequency f1 and angle θ1 of the fundamental current and the angle θ3 of the third harmonic current are obtained by a software phase-locked loop.

3. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 2, characterized in that: The measuring of the secondary coil induced voltage value and obtaining the secondary coil virtual axis induced voltage value specifically includes the following steps: The instantaneous value of the secondary coil induced voltage U2 is measured by the voltage sensor and used as the U in the virtual αβ axis induced voltage α , the value of U2 after using the 1 / 4 cycle delay method is used as U in the virtual αβ axis induced voltage β .

4. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 3, characterized in that: The extraction of the harmonic component in the secondary coil induced voltage specifically comprises the following steps: Using U α , U β , θ1 are transformed to the fundamental wave dq synchronous axis system, and the secondary coil induced voltage U is obtained d , U q ; U d , U q Perform low-pass filtering to obtain the component U of the secondary coil fundamental voltage in the fundamental dq synchronous axis system d_1 , U q_1 ; Using U d_1 , U q_1 , θ1 are transformed to the virtual αβ axis, and the components U of the secondary coil fundamental voltage on the virtual αβ axis are obtained respectively. α_1 , U β_1 ; Will U α and U α_1 Subtract, and through effective value calculation and low-pass filtering, the effective value U of the harmonic component in the secondary coil induced voltage is obtained. 2_3_RMS .

5. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 4, characterized in that: The secondary coil induced voltage U d , U q Satisfy IN d =U α cosθ1+U β sinθ1, IN q =-U α sinθ1+U β cosθ1.

6. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 4, characterized in that: The component U of the secondary coil fundamental voltage on the virtual αβ axis α_1 , U β_1 Satisfy IN α_1 =U d_1 cosθ1-U q_1 sinθ1, IN β_1 =U d_1 sinθ1+U q_1 cosθ1.

7. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 4, characterized in that: The calculation of the third harmonic voltage value to be compensated in the primary coil input voltage and outputting it through a programmable power supply specifically includes the following steps: Take U 2_3_RMS As the feedback quantity, the PI regulator is used to obtain the third harmonic voltage amplitude U that needs to be compensated in the primary coil input voltage. 1_3_AMP , Obtain the instantaneous value U of the third harmonic voltage that needs to be compensated in the primary coil input voltage 1_3 , Through the programmable power supply 1_3 It is added to the fundamental component of the primary coil input voltage for output.

8. The method for measuring magnetic properties of magnetic materials by improving the sinusoidality of magnetic polarization waveform according to claim 7, characterized in that: The instantaneous value U of the third harmonic voltage to be compensated in the primary coil input voltage 1_3 Meet U 1_3 =U 1_3_AMP sinθ3, Among them, U 1_3_AMP =(K p +K I / s)×(0-U 2_3_RMS ), where K p is the proportional coefficient of the PI regulator, K I is the integral coefficient of the PI regulator.

Images