High-saturation permanent magnet synchronous motor structure optimization method

Abstract

The invention relates to the technical field of motor design, and particularly discloses a high-saturation permanent magnet synchronous motor structure optimization method which comprises the following steps: S01, preliminarily establishing a two-dimensional electromagnetic field finite element model according to motor design requirements, and calculating an electromagnetic scheme of the two-dimensional electromagnetic field finite element model; s02, according to motor design requirements, determining a motor optimization structure parameter space and an optimization target; s03, based on the torque mathematical model of the high-saturation permanent magnet synchronous motor, establishing an objective function equation and constraint conditions; s04, analyzing the sensitivity of the optimization variables of the motor, and screening proper optimization variables according to the sensitivity to optimize the motor; s05, calculating and selecting a proper target group in the Pareto solution set according to target requirements; and S06, motor size parameters are selected as a final scheme according to actual production requirements, optimization is ended when the engineering design requirements are met, and the steps S01 to S05 are carried out again when the engineering design requirements are not met.

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 situations where short-term high-power operation is required, 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 have high air gap harmonic content, rotor structure load, large torque pulsation, and fast winding temperature rise. Its electromagnetic performance is greatly affected by factors such as rotor topology, motor stator-rotor split ratio, and motor length. To address the above issues, engineering and technical personnel usually optimize the design of sensitive parameters such as the motor stator-rotor structure after determining the approximate size of the motor;

[0004] However, due to the strong coupling and nonlinear characteristics of current and torque under high saturation permanent magnet synchronous motor load, traditional motor optimization theory is difficult to effectively estimate the motor torque under high saturation operation, resulting in a large amount of computing resources being used and the optimization effect is not ideal;

[0005] At present, the invention patent with the Chinese publication number CN117639609A discloses a motor optimization method and system based on the analytical-proxy-assisted dual-drive strategy. This method first quickly searches for a better subspace in the parameter space through an analytical coarse model, and then uses a small number of samples to establish a high-precision proxy for the subspace to take into account both the optimization speed and the optimization effect. However, this optimization scheme cannot guarantee the quality of the subspace samples, and insufficient subspace sampling will lead to unreliable optimization results;

[0006] The invention patent with the Chinese publication number CN113420505B discloses a method for optimizing the design of a permanent magnet assisted synchronous reluctance motor. The motor optimization speed is improved by electromagnetically decoupling the stator and rotor of the motor to reduce the optimization dimension of the motor. However, this method cannot establish an effective mathematical model of the stator and rotor flux after decoupling, and it is very easy for the optimization model to not converge, and it is not universal. In view of this, the inventor proposes 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: Preliminarily establish a two-dimensional electromagnetic field finite element model according to the motor design requirements and calculate 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 according to 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 permanent magnet flux and inductance instability problems caused by the magnetic saturation effect of the saturated motor. This method uses the mathematical model of the saturated motor to set the optimization objectives and constraints, which is more in line with the actual operation of the saturated motor than traditional optimization methods.

[0018] 2. This method combines the characteristics of saturated motor optimization when setting the objective function and constraints. Although the optimization dimensions are more, the optimization process is more systematic and the optimization results can better meet the design requirements. The motor control optimized by 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 than the traditional method in the test process. 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-saving, 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] Further, in step S03, the mathematical model of the high saturation permanent magnet synchronous motor torque is:

[0022]

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

[0024] The electromagnetic torque Te' is taken as the optimization target to increase it.

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

[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 currents. d ,i q ) represents the real-time value of each parameter under different d-axis and q-axis currents;

[0027]

[0028] Where: and are the total flux linkages on the 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, respectively. and are the 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, respectively, and 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] Further, 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] Further, in step S03, the optimization objective function equation of the saturated permanent magnet synchronous motor is:

[0037]

[0038] where f 1 、f 2 、f 3 、f 4 They represent the optimization objective function expressions of torque, inductance difference, heat load, and magnetic steel volume respectively;

[0039] The constraint function can be expressed as:

[0040]

[0041] The constraint g 1 , constraint g 2 , constraint g 3 , constraint g 4 They are the expressions of the constraints of motor structure, motor torque ripple, line voltage, and motor torque state.

[0042] Further, 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 drawings required for use in the description of the embodiments will be briefly introduced below. 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 of a high saturation permanent magnet synchronous motor structure optimization method proposed in an embodiment of the present application is shown;

[0045] Figure 2An optimization parameter representation diagram 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 explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination 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: Preliminarily establish a two-dimensional electromagnetic field finite element model according to the motor design requirements and calculate its electromagnetic scheme;

[0054] Specifically: The rotor structure of an internal permanent magnet synchronous motor is optimized. First, a two-dimensional finite element model of the initial design motor is 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 2This is a two-dimensional schematic diagram of the stator and rotor of a motor. However, the amount of calculation required for finite element calculation using a three-dimensional model is too large and the optimization time is long. Motor finite element analysis is a technology that uses the finite element method to numerically simulate and analyze physical phenomena such as electromagnetic field distribution, electromagnetic force, and heat distribution of the motor. The performance of the motor directly depends on the distribution and response of the internal electromagnetic field. Therefore, finite element analysis can provide a deep understanding of the working principle of the motor, optimize the design, and solve potential problems.

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

[0057] Specific:

[0058] Combination Figure 2 and Table 3, determine the initial design parameters of the optimized motor and the parameters 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:

[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 motor magnetic saturation effect 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 taking into account magnetic saturation effect is used instead of a traditional motor optimization model to calculate and optimize the electromagnetic torque Te′.

[0067] Specific:

[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 in inductance between the d-axis and q-axis considering the magnetic saturation effect;

[0071] The electromagnetic torque Te' is taken as the optimization target to increase it.

[0072] In step S02, the optimization target includes 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 is set as the optimization target, and the motor thermal load replaces the motor copper loss.

[0073] Specific:

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

[0075] Saturated motors require a large number of rare earth permanent magnets to maintain output power at a high saturation state. However, high-performance permanent magnets are very expensive. In order 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] The temperature rise of the saturated motor under load is serious and concentrated in the winding part. To ensure the safe operation of the motor, the motor copper loss needs to be reduced as much as possible. Since the calculation of the motor AC copper loss consumes a lot of resources, the motor thermal load is used instead of the motor copper loss as the optimization target.

[0077] Regarding the establishment of a 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. First, the saturation inductance and permanent magnet offset flux must be calculated according to their changing rules;

[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 currents. d ,i q ) represents the real-time value of each parameter under different d-axis and q-axis currents.

[0079]

[0080] and are the total 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, respectively. 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 precise: the optimization targets are set as electromagnetic torque considering magnetic saturation, permanent magnet area, d-axis and q-axis inductance difference considering magnetic saturation, and total motor flux considering magnetic saturation. The specific settings are as follows:

[0088]

[0089] The objective function f 1 is the electromagnetic torque function, f 2 is the inductance difference function, f 3 is the total flux linkage function of the permanent magnet, f 4 is the volume function of the permanent magnet, f 1 、f 2 、f 3 The larger the function value, the greater the unit volume efficiency, power and torque of the motor will reach the maximum. 4 The smaller the function value is, the smaller the volume of the permanent magnet of the motor is required and the lower the cost of the motor is.

[0090] Set optimization constraints:

[0091]

[0092] The constraint g 1 is the motor structure function. In order to constrain the motor structure not to exceed the set range, a series of constraint function sets need to be added, which are recorded as structure(x) here.

[0093] Constraint g 2 It is the torque pulsation function. Since the torque pulsation of the 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 g 3 is the motor back electromotive force. In order to prevent the motor from exceeding the DC bus voltage when running, the maximum value of the motor line back electromotive force is constrained;

[0096] Constraint g 4 The purpose is to put 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 according to 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 a different influence 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 sensitivity analysis of optimization parameters is as follows: Figure 2 shown.

[0099] Specifically: The corresponding sensitivity analysis method is a data processing method, such as polynomial fitting, while "MLS" is Moving Least Squares, and "isotrop.Kriging" refers to isotropic Kriging. These methods are algorithms 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. The purpose of performing sensitivity analysis on variables is 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, so all the results that meet the optimization conditions form a Pareto solution set. Obtaining this set is equivalent to obtaining all the optimized motor structure parameters, which is helpful for reference in the actual design of the motor.

[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 function adopted is the maximum average torque and the minimum 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 produced motors will not meet the optimization effect due to magnetic flux saturation. Therefore, in the optimization process, this patent improves the selection of the objective function to make the optimization design results 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 population individuals for 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-saving, 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 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 short periods of time.

[0123] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. 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 in that: The following steps are involved: S01: Preliminarily establish a two-dimensional electromagnetic field finite element model according to the motor design requirements and calculate its electromagnetic scheme; S02: Determine the motor optimization structural parameter space and optimization target according to the motor design requirements; S03: Based on the mathematical model of high saturation permanent magnet synchronous motor torque, establish the optimization objective function equation and constraint conditions; S04: Select the Polynom+MLS+isotrop.Kriging data processing method to analyze the sensitivity of the motor optimization variables, and select appropriate optimization variables according to 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 mathematical model of the high saturation permanent magnet synchronous motor torque is: Where Te′ is the saturated motor output electromagnetic torque, p is the number of motor pole pairs, is the difference in inductance between the d-axis and q-axis considering the magnetic saturation effect; The electromagnetic torque Te' is taken as the optimization target to increase it.

3. A high saturation permanent magnet synchronous motor structure optimization method according to claim 2, characterized in that: 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 change of d-axis and q-axis current at the same time, and the saturation inductance and permanent magnet offset flux need to be calculated according to their change law; 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 currents. d ,i q ) represents the real-time value of each parameter under different d-axis and q-axis currents; Where: and are the total 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, respectively. and are the 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 saturated permanent magnet synchronous motor are: Where: v d and v q are the d-axis and q-axis voltages, respectively, and 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. A high saturation permanent magnet synchronous motor structure optimization method according to claim 3, characterized in that: 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.

5. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 4, characterized in that: In step S03, the optimization objective function equation of the saturated permanent magnet synchronous motor is: Where f1, f2, f3, and f4 represent the optimization objective function expressions of torque, inductance difference, heat 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 pulsation, line voltage, and motor torque state respectively.

6. The method for optimizing the structure of a high saturation permanent magnet synchronous motor according to claim 4, characterized in that: In step S04, the algorithm Polynom+MLS+isotrop.Kriging is selected as the motor sensitivity analysis algorithm.

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