A fast calculation method of magnetic circuit parameters of low-coercivity nonlinear permanent magnet

Abstract

This invention belongs to the field of motor technology and discloses a rapid calculation method for magnetic circuit parameters of a low-coercivity nonlinear permanent magnet, including: performing finite element simulation calculation and analysis on the low-coercivity nonlinear permanent magnet; obtaining B-H data of the low-coercivity permanent magnet material based on the finite element analysis results; and based on the permanent magnet... Bm and Hm Data is used to obtain a simplified hysteresis model. Based on the recovery line and hysteresis loop in the simplified hysteresis model, the permanent magnet of the memory motor is fitted to obtain a piecewise linear fitted hysteresis model. Based on the principle of conservation of magnetic energy product, the piecewise linear fitted hysteresis model is corrected to obtain an equivalent linear B-H line. The results are verified by the magnetic circuit method and compared with the finite element method results. If the error is large, iterative correction is performed to obtain the predicted magnetic circuit parameters of the permanent magnet of the memory motor. This invention is simple to calculate, highly accurate, and can be applied to the precise prediction of online adjustment magnetomotive force in memory motors.

Description

Technical Field

[0001] This invention belongs to the field of motor technology, specifically relating to a rapid calculation method for magnetic circuit parameters of a low-coercivity nonlinear permanent magnet. Background Technology

[0002] The variable flux memory motor utilizes the high remanence and low coercivity of AlNiCo permanent magnets. By applying charging and demagnetizing current pulses, it changes the magnetization level of the permanent magnet to achieve efficient online magnetization adjustment. This solves the technical bottleneck of traditional permanent magnet motors that can only achieve high efficiency at a single operating point. It is considered a truly efficient flux-controllable permanent magnet motor with full-range magnetization.

[0003] In order to accurately control the magnetization state of the permanent magnet in the variable flux memory motor, it is necessary to conduct in-depth analysis of the equivalent model and characteristics of the nonlinear permanent magnet material and predict the nonlinear magnetic circuit parameters of the permanent magnet. Therefore, it is necessary to remove the nonlinear permanent magnet material from the motor and conduct nonlinear modeling analysis separately to explore the nonlinear magnetic circuit parameter model of the magnet. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a rapid calculation method for the magnetic circuit parameters of low-coercivity nonlinear permanent magnets. To verify the applicability of the "nonlinear permanent magnet model" in the field of memory motors and to explore the optimal permanent magnet design scheme, this project conducts research on the nonlinear modeling of low-coercivity variable flux permanent magnet materials for memory motors based on magnetic circuit methods and finite element analysis. Furthermore, the proposed nonlinear model is imported into the entire motor model for global modeling and analysis to deeply analyze the design parameters and corresponding magnetization characteristics of memory motors under different magnetization states, thereby quickly selecting the optimal permanent magnet design for the motor.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A rapid calculation method for magnetic circuit parameters of a low-coercivity nonlinear permanent magnet includes the following steps:

[0007] Finite element simulation method analysis of low coercivity materials;

[0008] Based on the finite element analysis results, the magnetic circuit parameters of the feature points are extracted to obtain the BH data of the low coercivity permanent magnet material.

[0009] B based on permanent magnets m and H m Data, yielding B m -H m The curve is obtained, and then a simplified hysteresis model is obtained. Based on the recovery line and hysteresis loop in the simplified hysteresis model, the permanent magnet of the memory motor is fitted to obtain a piecewise linear fitting hysteresis model.

[0010] Based on the principle of conservation of magnetic energy product, the piecewise linear fitting hysteresis model is modified to linearize the BH curve of the nonlinear permanent magnet to obtain an equivalent linear BH line. The magnetomotive force of the permanent magnet of the memory motor under different magnetization states is calculated by the magnetic circuit method and compared with the results of the finite element method (magnetomotive force obtained by extracting the magnetic circuit parameters of the feature points). If the comparison results are close, the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics. If the error of the comparison results is large, the piecewise linear fitting hysteresis model is iteratively modified until the comparison results are close, and the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics.

[0011] Furthermore, the method for fitting the permanent magnet of the memory motor based on the recovery line and hysteresis loop in the simplified hysteresis model is as follows: First, divide the recovery line and hysteresis loop in the simplified hysteresis model into four regions. Based on the magnitude of the current flowing through the permanent magnet, calculate 11 points in each region. Calculate the slope of adjacent points, and then calculate the average of the adjacent slopes of the 11 points. Then, use the coordinate point (B) m(avg) H m(avg) The y-intercept is obtained by finding the slope, and the curve is fitted for each segment. Similarly, the remaining three curve segments are fitted to obtain the piecewise linear fitting hysteresis model.

[0012] Furthermore, the fitting formula used when fitting the hysteresis loop of the permanent magnet in the memory motor is as follows:

[0013]

[0014]

[0015]

[0016] Among them, B m(i) H is the magnetic flux density at the selected point. m(i) Let B be the magnetic field strength at the selected point, and K be the slope of the line to be calculated; m(avg) H is the average magnetic flux density of the permanent magnet; m(avg) This represents the average magnetic field strength of the permanent magnet.

[0017] According to equations (1), (2), and (3), the y-intercept B can be obtained. ri for:

[0018] B ri =B m(avg) -k×H m(avg) ,i=1,2,3… (4)

[0019] Among them, B ri Let B be the y-intercept, K be the slope of the line to be found, and B be the y-intercept. m(avg)H is the average magnetic flux density of the permanent magnet. m(avg) This represents the average magnetic field strength of the permanent magnet.

[0020] Furthermore, the fitting formula used when fitting the recovery line of the permanent magnet of the memory motor is as follows:

[0021] B = K * H + B ri ,i=1,2,3… (5)

[0022] Where B is the magnetic flux density, H is the magnetic field strength, and K is the slope of the line being sought. ri This is the y-intercept.

[0023] Furthermore, the method for modifying the piecewise linear fitting hysteresis model based on the principle of conservation of magnetic energy product, and linearizing the BH curve of the nonlinear permanent magnet to obtain an equivalent linear BH line, is as follows:

[0024] The principle of conservation of magnetic energy product yields the relative permeability μ in the equivalent linear BH line. r After finite element analysis, the magnetic circuit parameters of the characteristic points were extracted based on the results. The relative permeability μ under different current conditions was calculated by dividing the current flowing through the permanent magnet into 10 points. r The average value is calculated using the following formula:

[0025]

[0026] Where, μ r(avg) μ is the average relative permeability of the permanent magnet. r(i) is the relative permeability of the selected point;

[0027] The average permeability of a nonlinear permanent magnet is given by the following formula:

[0028] μ (avg) =μ r(avg) ×μ0 (7)

[0029] Where, μ (avg) denoted as the mean permeability of the nonlinear permanent magnet, and μ0 as the free permeability.

[0030] Based on the piecewise linear fitting hysteresis model, and according to the law of conservation of magnetic energy product, the coercivity of the equivalent linear BH line is derived, as shown in the following formula:

[0031]

[0032] Among them, H c1 The coercivity is the equivalent linear BH line, S is the area of ​​the magnetic energy product of the piecewise linearly fitted hysteresis model, and μ is the area of ​​the magnetic energy product. (avg) The permeability of a nonlinear permanent magnet;

[0033] The equivalent linear BH line is finally obtained as follows:

[0034] B r =μ (avg) ×(H+H c1 (9)

[0035] Where H is the magnetic field strength, μ (avg) H is the mean permeability of a nonlinear permanent magnet. c1 It represents the coercivity of the equivalent linear BH line.

[0036] Furthermore, the method for calculating the magnetomotive force (MTF) of the permanent magnet in the memory motor under different magnetization states using the magnetic circuit method is as follows: The MMF is calculated using the formulas for calculating magnetic flux and magnetic reluctance, and the magnitudes of the MMF and magnetic reluctance of the permanent magnet in the memory motor under different magnetization states are predicted. The formulas are as follows:

[0037] Φ m =B m ×S m (10)

[0038]

[0039] F m =R m ×Φ m (12)

[0040] Where, Φ m For permanent magnet flux, S m R is the cross-sectional area of ​​the permanent magnet; m For permanent magnet reluctance, S m l is the cross-sectional area of ​​the permanent magnet. m F is the length of the nonlinear permanent magnet, μ is the permeability of the nonlinear permanent magnet; m R is the magnetomotive force of the permanent magnet. m For permanent magnet reluctance, Φ m It is the magnetic flux of a permanent magnet.

[0041] The beneficial effects of this invention are:

[0042] The online estimation method for the magnetization state of permanent magnets in memory motors proposed in this invention, based on piecewise linear fitting, can quickly and accurately obtain magnetic circuit parameters, which is of great significance for systems like memory motors where parameters change drastically within the operating range. Furthermore, the online estimation method for the magnetization state of permanent magnets proposed in this invention has a simple structure and does not require additional signal injection to avoid affecting the control system. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a block diagram illustrating the mathematical method for determining the magnetic circuit parameters of a low-coercivity nonlinear permanent magnet according to an embodiment of the present invention.

[0045] Figure 2 This is a fitting effect diagram of the hysteresis model based on piecewise linear fitting according to an embodiment of the present invention;

[0046] Figure 3 This is a magnetic circuit diagram of a numerical model of the magnetic circuit parameters of a low coercivity nonlinear permanent magnet according to an embodiment of the present invention. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] like Figure 1 As shown, a rapid calculation method for magnetic circuit parameters of a low-coercivity nonlinear permanent magnet includes the following steps:

[0049] Finite element simulation method analysis of low coercivity materials;

[0050] Based on the finite element analysis results, the magnetic circuit parameters of the feature points are extracted to obtain the BH data of the low coercivity permanent magnet material.

[0051] B based on permanent magnets m and H m Data, yielding B m -H m The curve is obtained, and then a simplified hysteresis model is obtained. Based on the recovery line and hysteresis loop in the simplified hysteresis model, the permanent magnet of the memory motor is fitted to obtain a piecewise linear fitting hysteresis model.

[0052] Based on the principle of conservation of magnetic energy product, the piecewise linear fitting hysteresis model is modified to linearize the BH curve of the nonlinear permanent magnet to obtain an equivalent linear BH line. The magnetomotive force of the permanent magnet of the memory motor under different magnetization states is calculated by the magnetic circuit method and compared with the results of the finite element method (magnetomotive force obtained by extracting the magnetic circuit parameters of the feature points). If the comparison results are close, the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics. If the error of the comparison results is large, the piecewise linear fitting hysteresis model is iteratively modified until the comparison results are close, and the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics.

[0053] Specifically, the finite element simulation method for analyzing low coercivity materials is as follows: the solution domain is considered to be composed of many small interconnected subdomains called finite elements. A suitable approximate solution is assumed for each element, and then the overall satisfying conditions of this domain are derived.

[0054] Specifically, the method for fitting the permanent magnet of the memory motor based on the recovery line and hysteresis loop in the simplified hysteresis model is as follows: First, divide the recovery line and hysteresis loop in the simplified hysteresis model into four regions. Based on the magnitude of the current flowing through the permanent magnet, calculate 11 points in each region. Calculate the slope of adjacent points, and then calculate the average of the adjacent slopes of the 11 points. Then, use the coordinate point (B) m(avg) H m(avg) The y-intercept is obtained by finding the slope, and the curve is fitted for each segment. Similarly, the remaining three curve segments are fitted to obtain the piecewise linear fitting hysteresis model.

[0055] Specifically, the fitting formula used when fitting the hysteresis loop of the permanent magnet in the memory motor is as follows:

[0056]

[0057]

[0058]

[0059] In equation (1), B m(i) H is the magnetic flux density at the selected point. m(i) Let be the magnetic field strength at the selected point, and K be the slope of the line to be calculated.

[0060] In equation (2), B m(avg) The average magnetic flux density of the permanent magnet;

[0061] In equation (3), H m(avg) This represents the average magnetic field strength of the permanent magnet.

[0062] According to equations (1), (2), and (3), the y-intercept B can be obtained. ri for:

[0063] B ri =B m(avg) -k×H m(avg) ,i=1,2,3… (4)

[0064] In equation (4), B ri Let B be the y-intercept, K be the slope of the line to be found, and B be the y-intercept. m(avg) H is the average magnetic flux density of the permanent magnet. m(avg) This represents the average magnetic field strength of the permanent magnet.

[0065] Specifically, the fitting formula used when fitting the recovery line of the permanent magnet in the memory motor is as follows:

[0066] B = K * H + B ri ,i=1,2,3… (5)

[0067] In equation (5), B is the magnetic flux density, H is the magnetic field strength, and K is the slope of the line to be calculated. ri This is the y-intercept.

[0068] Specifically, the principle of conservation of magnetic energy product yields the relative permeability μ in the equivalent linear BH line. r After finite element analysis, the magnetic circuit parameters of the characteristic points were extracted based on the results. The relative permeability μ under different current conditions was calculated by dividing the current flowing through the permanent magnet into 10 points. r The average value is calculated using the following formula:

[0069]

[0070] In equation (6), μ r(avg) μ is the average relative permeability of the permanent magnet. r(i) denoted as where is the relative permeability of the selected point.

[0071] The average permeability of a nonlinear permanent magnet is given by the following formula:

[0072] μ (avg) =μ r(avg) ×μ0 (7)

[0073] In equation (7), μ (avg) denoted as the mean permeability of the nonlinear permanent magnet, and μ0 as the permeability of free space.

[0074] Based on the piecewise linear fitting hysteresis model and the law of conservation of magnetic energy product, the coercivity of the equivalent linear BH line is derived, as shown in the following formula:

[0075]

[0076] In equation (8), H c1 The coercivity is the equivalent linear BH line, S is the area of ​​the magnetic energy product of the piecewise linearly fitted hysteresis model, and μ is the area of ​​the magnetic energy product.(avg) is the permeability of a nonlinear permanent magnet.

[0077] The equivalent linear BH line is finally obtained as follows:

[0078] B r =μ (avg) ×(H+H c1 (9)

[0079] In equation (9), H is the magnetic field strength, μ (avg) H is the mean permeability of a nonlinear permanent magnet. c1 It represents the coercivity of the equivalent linear BH line.

[0080] The magnetic circuit method is used, which calculates the magnetomotive force using formulas for magnetic flux and magnetic reluctance, to predict the magnetization state B of the permanent magnet in the memory motor under different conditions. m The magnitudes of the magnetomotive force and magnetic reluctance at that time are given by the following formulas:

[0081] Φ m =B m ×S m (10)

[0082]

[0083] F m =R m ×Φ m (12)

[0084] In equation (10), Φ m For permanent magnet flux, S m The cross-sectional area of ​​the permanent magnet;

[0085] In equation (11), R m For permanent magnet reluctance, S m l is the cross-sectional area of ​​the permanent magnet. m denoted as the length of the nonlinear permanent magnet, and μ as the permeability of the nonlinear permanent magnet.

[0086] In equation (12), F m R is the magnetomotive force of the permanent magnet. m For permanent magnet reluctance, Φ m It is the magnetic flux of a permanent magnet.

[0087] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A rapid calculation method for magnetic circuit parameters of a low-coercivity nonlinear permanent magnet, characterized in that, Includes the following steps: Finite element simulation method analysis of low coercivity materials; Based on the finite element analysis results, the magnetic circuit parameters of the feature points were extracted to obtain low coercivity permanent magnet materials. BH data; Based on permanent magnets B m and H m Data, derived B m -H m The curve is obtained, and then a simplified hysteresis model is obtained. Based on the recovery line and hysteresis loop in the simplified hysteresis model, the permanent magnet of the memory motor is fitted to obtain a piecewise linear fitting hysteresis model. The piecewise linear fitting hysteresis model is modified based on the principle of conservation of magnetic energy product, and the nonlinear permanent magnet is... BH Curve linearization yields equivalent linearity BH The magnetomotive force of the permanent magnet of the memory motor under different magnetization states is calculated by the magnetic circuit method and compared with the results of the finite element method. If the comparison results are close, the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics. If the error of the comparison results is large, the piecewise linear fitting hysteresis model is iteratively corrected until the comparison results are close, and the equivalent magnetic circuit parameters are obtained to achieve accurate prediction of online magnetic adjustment characteristics. The aforementioned correction of the piecewise linear fitting hysteresis model based on the principle of conservation of magnetic energy product, and the nonlinear permanent magnet... B- H Curve linearization yields equivalent linearity BH The method for using a straight line is as follows: The principle of conservation of magnetic energy product yields the equivalent linearity BH Relative permeability in a straight line μ r After finite element analysis, the magnetic circuit parameters of the characteristic points were extracted based on the results. The relative permeability under different current conditions was calculated by dividing the current flowing through the permanent magnet into 10 points. μ r The average value is calculated using the following formula: (6) in, μ r(avg) This represents the average relative permeability of the permanent magnet. μ r(i) The relative permeability of the selected point; The average permeability of a nonlinear permanent magnet is given by the following formula: (7) in, μ (avg) The mean permeability of the nonlinear permanent magnet. μ 0 Permeability of free space; Based on the piecewise linear fitting hysteresis model, and according to the law of conservation of magnetic energy product, the equivalent linear model is obtained. BH The coercivity of a straight line is given by the following formula: (8) in, H c1 For equivalent linear BH Coercivity of a straight line S The magnetic energy product area is the piecewise linear fitting area of ​​the hysteresis model. μ (avg) The permeability of a nonlinear permanent magnet; Finally, the equivalent linearity is obtained. BH The straight line is: (9) in, H The magnetic field strength, μ (avg) The mean permeability of the nonlinear permanent magnet. H c1 For equivalent linear BH Coercivity of a straight line.

2. The method for rapid calculation of magnetic circuit parameters of a low-coercivity nonlinear permanent magnet according to claim 1, characterized in that, The method for fitting the permanent magnet of the memory motor based on the recovery line and hysteresis loop in the simplified hysteresis model is as follows: First, divide the recovery line and hysteresis loop in the simplified hysteresis model into four regions. Based on the magnitude of the current flowing through the permanent magnet, calculate 11 points in each region. Calculate the slope of adjacent points, and then calculate the average of the adjacent slopes of the 11 points. Then, use the coordinate points ( B m(avg) ,H m(avg) The y-intercept is obtained by finding the slope, and the curve is fitted for each segment. Similarly, the remaining three curve segments are fitted to obtain the piecewise linear fitting hysteresis model.

3. The method for rapid calculation of magnetic circuit parameters of a low-coercivity nonlinear permanent magnet according to claim 2, characterized in that, The fitting formula used when fitting the hysteresis loop of the permanent magnet in the memory motor is as follows: （2） （3） in, B m(i) The magnetic flux density at the selected point is... H m(i) The magnetic field strength at the selected point is... K Let be the slope of the line in question; B m(avg) The average magnetic flux density of the permanent magnet; H m(avg) This represents the average magnetic field strength of the permanent magnet. The y-intercept can be obtained from equations (1), (2), and (3). B ri for: （4） in, B ri The y-intercept. K Let be the slope of the line in question. B m(avg) This represents the average magnetic flux density of the permanent magnet. H m(avg) This represents the average magnetic field strength of the permanent magnet.

4. The method for rapid calculation of magnetic circuit parameters of a low-coercivity nonlinear permanent magnet according to claim 3, characterized in that, The fitting formula used when fitting the recovery line of the permanent magnet in the memory motor is as follows: （5） in, B For magnetic density, H The magnetic field strength, K Let be the slope of the line in question. B ri This is the y-intercept.

5. The method for rapid calculation of magnetic circuit parameters of a low-coercivity nonlinear permanent magnet according to claim 4, characterized in that, The method for calculating the magnetomotive force (MTF) of the permanent magnet in a memory motor under different magnetization states using the magnetic circuit method is as follows: The MMF is calculated using the formulas for calculating magnetic flux and magnetic reluctance, and the magnitudes of the MMF and magnetic reluctance of the permanent magnet in the memory motor under different magnetization states are predicted. The formulas are as follows: （10） （11） （12） in, Φ m For permanent magnet flux, S m The cross-sectional area of ​​the permanent magnet; R m It is a permanent magnet reluctance. l m The length of the nonlinear permanent magnet. The permeability of a nonlinear permanent magnet; F m It is the magnetomotive force of the permanent magnet.

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