A structural optimization method for high saturation permanent magnet synchronous motor

Abstract

The present invention relates to the technical field of motor design, and specifically discloses a high-saturation permanent magnet synchronous motor structure optimization method, comprising the following steps: S01: preliminarily establishing a two-dimensional electromagnetic field finite element model according to motor design requirements, and calculating its electromagnetic scheme; S02: determining the motor optimization structure parameter space and optimization target according to the motor design requirements; S03: establishing an objective function equation and constraint conditions based on a high-saturation permanent magnet synchronous motor torque mathematical model; S04: analyzing the sensitivity of motor optimization variables, and screening suitable optimization variables for motor optimization according to the sensitivity; S05: calculating and selecting an appropriate target group in the Pareto solution set according to the target requirements; S06: selecting motor size parameters as the final solution according to actual production needs, and ending the optimization if the engineering design requirements are met; if not, repeating steps S01 to S05. The present invention aims to propose a more excellent motor structure optimization model.

Description

Technical Field

[0001] The present application relates to the technical field of motor design, and specifically discloses a method for optimizing the structure of a high-saturation permanent magnet synchronous motor. Background Art

[0002] With the development of current science and technology, modern industry has higher and higher requirements for motor design. In the occasions of short-term high-power operation such as electric rocket recovery, cutting machines, centrifuges, etc., in order to reduce the size of the motor and achieve lightweight design of the motor, high-saturation permanent magnet synchronous motors are increasingly favored by major manufacturers. High-saturation permanent magnet synchronous motors have the advantages of small size, strong short-term overload capacity, and recyclability. However, high-saturation permanent magnet synchronous motors are difficult to control, have a short-term temperature rise, and are expensive, and usually require the use of a large number of rare earth permanent magnets;

[0003] High-saturation permanent magnet synchronous motors (PMSMs) are characterized by high air-gap harmonics, rotor structural loads, large torque ripple, and rapid winding temperature rise. Their electromagnetic performance is significantly affected by factors such as rotor topology, stator-rotor split ratio, and motor length. To address these issues, engineers typically optimize the design of sensitive parameters such as the stator-rotor structure after roughly determining the motor's dimensions.

[0004] However, due to the strong coupling and nonlinearity between current and torque in highly saturated permanent magnet synchronous motors, traditional motor optimization theories have difficulty effectively estimating motor torque under highly saturated conditions, resulting in a large consumption of computing resources and unsatisfactory optimization results.

[0005] Currently, the Chinese invention patent CN117639609A discloses a motor optimization method and system based on an analytical-proxy-assisted dual-drive strategy. This method first uses an analytical coarse model to quickly search for a good subspace in the parameter space, then uses a small number of samples to establish a high-precision proxy in the subspace, balancing optimization speed and effectiveness. However, this optimization scheme cannot guarantee the quality of the subspace samples, and insufficient subspace sampling can lead to unreliable optimization results.

[0006] Patent publication number CN113420505B discloses a method for optimizing the design of a permanent magnet-assisted synchronous reluctance motor. This method reduces the motor optimization dimension by electromagnetically decoupling the stator and rotor, improving motor optimization speed. However, this method fails to establish an effective mathematical model for the decoupled stator and rotor flux linkage, making it prone to non-convergence of the optimization model and lacking universal applicability. Therefore, the inventors propose a method for optimizing the structure of a high-saturation permanent magnet synchronous motor. Summary of the Invention

[0007] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a method for optimizing the structure of a high-saturation permanent magnet synchronous motor.

[0008] In order to achieve the above object, the present invention provides the following basic scheme:

[0009] A method for optimizing the structure of a high-saturation permanent magnet synchronous motor comprises the following steps:

[0010] S01: Preliminary establishment of a two-dimensional electromagnetic field finite element model based on motor design requirements and calculation of its electromagnetic scheme;

[0011] S02: Determine the motor optimization structural parameter space and optimization target according to the motor design requirements;

[0012] S03: Based on the mathematical model of high saturation permanent magnet synchronous motor torque, establish the optimization objective function equation and constraint conditions;

[0013] S04: Select the Polynom+MLS+isotrop.Kriging data processing method to analyze the sensitivity of the motor optimization variables, and select appropriate optimization variables based on the sensitivity to further optimize the motor;

[0014] S05: Use a multi-objective optimization algorithm to calculate the Pareto solution set and select the appropriate target group in the Pareto solution set according to the target requirements;

[0015] S06: Select motor size parameters as the final solution based on actual production needs. If the engineering design requirements are met, the optimization is terminated. If not, steps S01 to S05 are repeated.

[0016] The principles and effects of this basic solution are:

[0017] 1. This method can be used to optimize the unstable permanent magnet flux and inductance caused by the magnetic saturation effect in saturated motors. This method uses the mathematical model of the saturated motor to set the optimization objectives and constraints. Compared with traditional optimization methods, it is more in line with the actual operation of saturated motors.

[0018] 2. This method incorporates the characteristics of saturated motor optimization when setting the objective function and constraints. Although the optimization dimensions increase, the optimization process is more systematic, and the optimization results can better meet the design requirements. The motor control optimized using this method is more stable and reliable.

[0019] 3. This method takes into account the influence of magnetic saturation and is more in line with the actual situation during the test process than traditional methods. Under this optimization design method, the motor volume can be effectively reduced, the system can be lightweight, the motor control process is robust and cost-effective, and the system can be guaranteed to operate stably and reliably.

[0020] 4. The technical solution provided by the present invention adopts the mathematical model of the saturated motor for optimization, which increases a certain amount of calculation compared to the traditional optimization process, but the optimization result is more suitable for engineering applications and is helpful for the design and manufacture of saturated motors that work for a short time.

[0021] Furthermore, in step S03, the high saturation permanent magnet synchronous motor torque mathematical model is:

[0022]

[0023] Where Te′ is the saturated motor output electromagnetic torque, p is the number of motor pole pairs, is the difference between the d-axis and q-axis inductances considering the magnetic saturation effect;

[0024] The electromagnetic torque Te′ is optimized to increase it.

[0025] Furthermore, in the process of establishing the mathematical model of high-saturation permanent magnet synchronous motor torque, the permanent magnet flux and inductance of the high-saturation permanent magnet synchronous motor torque will change significantly with the changes of the d-axis and q-axis currents at the same time, and the saturation inductance and permanent magnet offset flux need to be calculated based on their changing laws;

[0026] When the motor is running in high saturation state, the permanent magnet flux and inductance will change significantly with the change of d-axis and q-axis current. d ,i q ) represents the real-time values ​​of various parameters under different d-axis and q-axis currents;

[0027]

[0028] Where: and are the total magnetic flux of d-axis and q-axis respectively, and are the d-axis and q-axis inductances, i d and i q are the d-axis and q-axis currents, and are the magnetic flux components of the permanent magnet on the d-axis and q-axis respectively;

[0029] The voltage equations of the d-axis and q-axis of the saturated permanent magnet synchronous motor are:

[0030]

[0031] Where: v d and v q are the d-axis and q-axis voltages, R s is the stator resistance, ω e is the motor electrical angular velocity;

[0032] The d-axis and q-axis components of the permanent magnet flux can be expressed as:

[0033]

[0034] You can get: mathematical model of high saturation permanent magnet synchronous motor torque.

[0035] Furthermore, in step S02 , the optimization target includes at least the inductance difference between the d-axis and the q-axis considering the magnetic saturation effect, the volume of the permanent magnet, and the motor thermal load instead of the motor copper loss.

[0036] Furthermore, in step S03, the optimization objective function equation of the saturated permanent magnet synchronous motor is:

[0037]

[0038] Where f1, f2, f3, and f4 represent the optimization objective function expressions of torque, inductance difference, thermal load, and magnetic steel volume respectively;

[0039] The constraint function can be expressed as:

[0040]

[0041] Among them, constraint g1, constraint g2, constraint g3, and constraint g4 are expressions of the constraint conditions of motor structure, motor torque ripple, line voltage, and motor torque state respectively.

[0042] Furthermore, in step S04 , the algorithm Polynom+MLS+isotrop.Kriging is selected as the motor sensitivity analysis algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A permanent magnet synchronous motor optimization flow chart showing a high saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0045] Figure 2 A diagram showing the optimization parameters of a high saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0046] Figure 3 A sensitivity analysis diagram of optimization parameters of a high saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0047] Figure 4 A comparison diagram of electromagnetic torque before and after optimization of a high saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0048] Figure 5 A comparison diagram of permanent magnet flux before and after optimization of a high-saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0049] Figure 6 A comparison diagram of the d-axis and q-axis inductance differences before and after optimization of a high-saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0050] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0051] Implementation example Figure 1 、 Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 As shown:

[0052] A method for optimizing the structure of a high-saturation permanent magnet synchronous motor comprises the following steps:

[0053] S01: Preliminary establishment of a two-dimensional electromagnetic field finite element model based on motor design requirements and calculation of its electromagnetic scheme;

[0054] Specifically: To optimize the rotor structure of an internal permanent magnet synchronous motor, a two-dimensional finite element model of the initial design motor was first established.

[0055] A normal motor is a three-dimensional model with three dimensions: length, width and height. A two-dimensional model is a cross section of the motor. Figure 2 This is a two-dimensional schematic diagram of a motor's stator and rotor. However, using a three-dimensional model for finite element analysis (FEA) is computationally intensive and time-consuming. Motor FEA utilizes the finite element method to numerically simulate and analyze physical phenomena such as electromagnetic field distribution, electromagnetic forces, and thermal distribution. Motor performance directly depends on the distribution and response of the internal electromagnetic field. Therefore, FEA can provide a deeper understanding of motor operating principles, optimize design, and resolve potential issues.

[0056] S02: Determine the motor optimization structural parameter space and optimization target according to the motor design requirements;

[0057] Specifically:

[0058] Combine Figure 2 and Table 3, determine the initial design parameters of the optimized motor and the values ​​represented by each parameter.

[0059] Meaning. Determine the optimization parameter space array as:

[0060]

[0061] where x i represents the optimized array space of the motor designed for the i-th motor, the is the angle between the motor current d-axis and q-axis, and the optimized parameters and optimization range of each motor are shown in Table 1 below:

[0062] parameter Initial value Range of variation O1 / mm 2 [1,3] O2 / mm 4 [2.5,6.5] O3 / mm 17 [15,20] B1 / mm 5.2 [4,5.5] B2 / mm 27 [24,31] B3 / mm 4.2 [3.5,5] B4 / mm 28 [25,30] HRib / mm 5 [3,7.5] the 52 [50,60] Rib 35 [30,40]

[0063] Table 1

[0064] The d-axis and q-axis currents are calculated based on the angle the, and the magnetic flux considering the magnetic saturation effect of the motor is calculated based on the d-axis and q-axis currents. and inductance

[0065] S03: Based on the mathematical model of high saturation permanent magnet synchronous motor torque, establish the optimization objective function equation and constraint conditions;

[0066] Specifically, a motor model that considers magnetic saturation effect is used instead of a traditional motor optimization model to calculate and optimize the electromagnetic torque Te′.

[0067] Specifically:

[0068] In step S03, the mathematical model of the high saturation permanent magnet synchronous motor torque is:

[0069]

[0070] Where Te′ is the saturated motor output electromagnetic torque, p is the number of motor pole pairs, is the difference between the d-axis and q-axis inductances taking into account the magnetic saturation effect;

[0071] The electromagnetic torque Te′ is optimized to increase it.

[0072] In step S02 , the optimization target includes at least the difference between the d-axis and q-axis inductances considering the magnetic saturation effect, the volume of the permanent magnet being set as the optimization target, and the motor thermal load replacing the motor copper loss.

[0073] Specifically:

[0074] Generally, the greater the difference between the d-axis and q-axis inductances of a motor controlled by MTPA, the greater the output reluctance torque and the smaller the required current. Especially in high saturation state, the difference between the d-axis and q-axis inductances will change as the motor saturation operating state changes. It is also the optimization goal.

[0075] Saturated motors require a large number of rare earth permanent magnets to maintain output power in a high saturation state. However, high-performance permanent magnets are very expensive. To save design costs, the volume of the permanent magnets needs to be set as an optimization target to be reduced as much as possible.

[0076] Under saturated motor load, the temperature rise is severe and concentrated in the windings. To ensure safe motor operation, the motor's copper loss must be minimized. Since calculating the motor's AC copper loss consumes a lot of resources, the motor's thermal load is used instead of the motor's copper loss as the optimization target.

[0077] Regarding the establishment of a mathematical model for the torque of a high-saturation permanent magnet synchronous motor, the permanent magnet flux and inductance of the high-saturation permanent magnet synchronous motor will change significantly with the changes in the d-axis and q-axis currents. First, the saturation inductance and permanent magnet offset flux must be calculated based on their changing patterns.

[0078] When the motor is running in high saturation state, the permanent magnet flux and inductance will change significantly with the change of d-axis and q-axis current. d ,i q ) represents the real-time values ​​of various parameters under different d-axis and q-axis currents.

[0079]

[0080] and are the total magnetic flux of d-axis and q-axis respectively, and are the d-axis and q-axis inductances, i d and i q are the d-axis and q-axis currents, and are the magnetic flux components of the permanent magnet on the d-axis and q-axis respectively.

[0081] The voltage equations of the d-axis and q-axis of the saturated permanent magnet synchronous motor are:

[0082]

[0083] Where: v d and are the d-axis and q-axis voltages respectively, R s is the stator resistance, ω e is the motor electrical angular velocity.

[0084] The d-axis and q-axis components of the permanent magnet flux can be expressed as:

[0085]

[0086] You can get: mathematical model of high saturation permanent magnet synchronous motor torque.

[0087] To be more precise, the optimization objectives are set as the electromagnetic torque considering magnetic saturation, the permanent magnet area, the d-axis and q-axis inductance difference considering magnetic saturation, and the total motor flux considering magnetic saturation. The specific settings are as follows:

[0088]

[0089] Among them, the objective function f1 is the electromagnetic torque function, f2 is the inductance difference function, f3 is the total magnetic flux function of the permanent magnet, and f4 is the volume function of the permanent magnet. The larger the function values ​​of f1, f2, and f3 are, the maximum unit volume efficiency, power, and torque of the motor will be. The smaller the function value of f4 is, the smaller the volume required for the permanent magnet of the motor will be, and the lower the cost of the motor will be.

[0090] Set optimization constraints:

[0091]

[0092] The constraint g1 is the motor structure function. In order to constrain the motor structure to not exceed the set range, a series of constraint function sets need to be added, which are denoted as structure(x) here.

[0093] Constraint g2 is the torque ripple function. Since the torque ripple of a saturated motor is large, it can be set to 10% of the rated electromagnetic torque.

[0094] Where Te′ is the rated electromagnetic torque;

[0095] Constraint g3 is the motor back electromotive force. In order to prevent the motor from exceeding the DC bus voltage during operation, the maximum value of the motor line back electromotive force is constrained.

[0096] Constraint g4 is to keep the optimized motor in a high torque state.

[0097] S04: Select the Polynom+MLS+isotrop.Kriging data processing method to analyze the sensitivity of the motor optimization variables, and select appropriate optimization variables based on the sensitivity to further optimize the motor;

[0098] The algorithm Polynom+MLS+isotrop.Kriging is selected as the motor sensitivity analysis algorithm. Since each optimization parameter has different effects on the optimization target, the specific influence of each parameter on the optimization target can be obtained through sensitivity analysis, so as to carry out targeted optimization design of the motor. The optimization parameter sensitivity analysis is as follows: Figure 2 shown.

[0099] Specifically, sensitivity analysis methods are data processing methods, such as polynomial fitting, "MLS" (Moving Least Squares), and "isotrop.Kriging" (Isotropic Kriging). These methods are algorithms used for data fitting and interpolation.

[0100] S05: Use a multi-objective optimization algorithm to calculate the Pareto solution set and select the appropriate target group in the Pareto solution set according to the target requirements;

[0101] Regarding the above steps:

[0102] 1. Sensitivity analysis of variables is performed to determine the parameters that can be optimized. There are many parameters that can be optimized for the stator and rotor, but the degree of influence of each parameter on the objective function is different, so the parameters to be optimized must be selected through sensitivity analysis.

[0103] 2. Because after calculation, more than one optimal goal is obtained, all the results that meet the optimization conditions form a Pareto solution set. Obtaining this set is equivalent to obtaining all the optimized motor structural parameters, which is helpful for reference in the actual motor design.

[0104] 3. The optimization effect of this set on the motor depends on the set objective function. For the case in this article, the main objective functions adopted are maximizing the average torque and minimizing the permanent magnet volume. Therefore, the Pareto solution set is a series of motor structural parameters that can be selected while trying to meet these two conditions.

[0105] 4. This patent emphasizes that the selection of the objective function for saturated motors is different from that for ordinary motors, because the mathematical models of the magnetic flux, voltage, and torque of saturated motors are different from those of ordinary motors. If the objective function of ordinary motors is adopted, it is very likely that the actual production of the motor will not meet the optimization effect due to magnetic flux saturation. Therefore, this patent has improved the selection of the objective function during the optimization process, so that the optimization design results are more in line with the actual manufacturing results of high-saturation motors. S04 and S05 are two indispensable steps for the overall structural optimization process of the motor and are the prerequisite for the selection of the objective function. Specifically: perform optimization analysis on the motor and solve the Pareto solution set. The Pareto plane is the set of algebraic solutions of all individuals in the population with respect to the optimization objective. Combined with actual engineering experience, the optimal solution is selected in the appropriate subset. The solution selected here is:

[0106] x 5348 =[2,3,17,5,25.5,4.5,29,3,56,32]

[0107] Step 5: Compare and verify this solution with the original solution and observe the changes in motor performance after optimization. Figure 4 、 Figure 5 、 Figure 6 Judging from the data in , the optimized motor data is better than the original design.

[0108] The performance improvement of the optimization target can be seen from Table 2 below.

[0109]

[0110] Table 2

[0111] The basic parameter data of the motor can be obtained from Table 3.

[0112] (1) Rated data

[0113]

[0114] (2) Stator data

[0115]

[0116] (3) Rotor data

[0117]

[0118] Table 3

[0119] S06: Select motor size parameters as the final solution based on actual production needs. If the engineering design requirements are met, the optimization is terminated. If not, steps S01 to S05 are repeated.

[0120] Finally, the prototype can be manufactured by combining the optimized design data.

[0121] The saturated motor optimization method described in the embodiment of the present invention takes into account the influence of magnetic saturation and is more in line with the actual situation during the test process than the traditional method. Under this optimization design method, the motor volume can be effectively reduced, the system can be lightweight, the motor control process is robust and cost-effective, and the system can be guaranteed to operate stably and reliably.

[0122] The technical solution provided by the present invention adopts the mathematical model of the saturated motor for optimization, which increases a certain amount of calculation compared with the traditional optimization process, but the optimization result is more suitable for engineering applications and is helpful for the design and manufacture of saturated motors that work for short periods of time.

[0123] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for optimizing the structure of a high-saturation permanent magnet synchronous motor, characterized by: The following steps are involved: S01: Preliminary establishment of a two-dimensional electromagnetic field finite element model based on motor design requirements and calculation of its electromagnetic scheme; S02: Determine the motor optimization structural parameter space and optimization target according to the motor design requirements; The optimization objectives include at least the difference in inductance between the d-axis and the q-axis considering the magnetic saturation effect, the volume of the permanent magnet, and the motor thermal load instead of the motor copper loss; S03: Based on the high-saturation permanent magnet synchronous motor torque mathematical model, establish the optimization objective function equation and constraint conditions; in the process of establishing the high-saturation permanent magnet synchronous motor torque mathematical model, the permanent magnet flux and inductance of the high-saturation permanent magnet synchronous motor torque will change significantly with the changes in the d-axis and q-axis currents at the same time, and it is necessary to calculate the saturation inductance and permanent magnet offset flux according to their change rules; S04: Select data processing methods, analyze the sensitivity of motor optimization variables, and select appropriate optimization variables based on the sensitivity to further optimize the motor; S05: Use a multi-objective optimization algorithm to calculate the Pareto solution set and select the appropriate target group in the Pareto solution set according to the target requirements; S06: Select motor size parameters as the final solution based on actual production needs. If the engineering design requirements are met, the optimization is terminated. If not, steps S01 to S05 are repeated.

2. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 1, characterized in that: In step S03, the high saturation permanent magnet synchronous motor torque mathematical model is: Where Te′ is the motor output electromagnetic torque, p is the number of motor pole pairs, is the difference between the d-axis and q-axis inductances considering the magnetic saturation effect; The electromagnetic torque Te′ is optimized to increase it.

3. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 2, characterized in that: When the motor is running in high saturation state, the permanent magnet flux and inductance will change significantly with the change of d-axis and q-axis current. d ,i q ) represents the real-time values ​​of various parameters under different d-axis and q-axis currents; Where: and are the total magnetic flux of d-axis and q-axis respectively, and are the d-axis and q-axis inductances, i d and i q are the d-axis and q-axis currents, and are the magnetic flux components of the permanent magnet on the d-axis and q-axis respectively; The voltage equations of the d-axis and q-axis of the high saturation permanent magnet synchronous motor are: Where: v d and v q are the d-axis and q-axis voltages, R s is the stator resistance, ω e is the motor electrical angular velocity; The d-axis and q-axis components of the permanent magnet flux can be expressed as: You can get: mathematical model of high saturation permanent magnet synchronous motor.

4. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 1, wherein: In step S03, the optimization objective function equation is: Where f1, f2, f3, and f4 represent the optimization objective function expressions of torque, inductance difference, thermal load, and magnetic steel volume respectively; The constraint function can be expressed as: Among them, constraint g1, constraint g2, constraint g3, and constraint g4 are expressions of the constraint conditions of motor structure, motor torque ripple, line voltage, and motor torque state respectively.

5. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 1, wherein: In step S04 , polynomial fitting, moving least squares, and isotropic Kriging interpolation algorithms are selected as motor sensitivity analysis algorithms.

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