A variable flux leakage permanent magnet synchronous motor considering multiple operating conditions and its low vibration and noise optimization design method

Abstract

The present invention discloses a variable-leakage permanent magnet synchronous motor and its low-vibration-noise optimization design method that considers multiple operating conditions. The method comprises the following steps: obtaining a variable permanent magnet leakage flux through the magnetic circuit distribution of the permanent magnet motor; adjusting the amount of permanent magnet leakage flux to meet the motor's requirements for torque, speed regulation range, and low vibration and noise when the motor is in different operating conditions; constructing a regional leakage flux structure to achieve controllable leakage flux and provide the motor's initial structure; analyzing the electromagnetic vibration characteristics of the variable-leakage permanent magnet synchronous motor under different operating conditions to obtain relevant data on performance such as the lowest non-zero-order electromagnetic force; evaluating the degree to which key motor parameters affect electromagnetic performance and the performance requirements of the motor under different operating conditions; and performing comprehensive optimization using a multi-objective genetic algorithm to determine the final size of the motor. The present invention enables the motor to achieve wide speed regulation and high torque performance while suppressing the motor's vibration and noise under different operating conditions.

Description

Technical Field

[0001] The invention belongs to the field of motor design and relates to a low vibration and noise optimization design method for a permanent magnet synchronous motor. Background Art

[0002] In recent years, with the rapid development of new energy vehicles, permanent magnet synchronous motors (PMSMs), owing to their high power density and efficiency, have been widely used in electric vehicles. However, the ever-changing driving environment and variable operating conditions of electric vehicles place higher performance demands on the motor and its drive system. Traditional PMSMs have a relatively constant permanent magnet potential, making the air gap magnetic field difficult to adjust. This makes field-weakening speed increases difficult, limiting the motor's speed regulation range. Consequently, variable-leakage permanent magnet synchronous motors (PMSMs), which can meet the needs of diverse operating conditions, are attracting increasing attention both domestically and internationally. Through the targeted design of the magnetic barrier and permanent magnet structure, PMSMs with variable-leakage magnetic flux exhibit zero leakage under heavy loads and high leakage under light loads. These motors can achieve high torque at low speeds and constant power at high speeds, meeting the diverse operating conditions of electric vehicles.

[0003] However, it is worth noting that as drive motors gradually develop towards high power density and lightweight, the vibration and noise problems of motors are becoming increasingly prominent, seriously affecting the driving experience of passengers. For this reason, the academic community has conducted a lot of research on the vibration and noise problems of motor systems. The research found that the electromagnetic vibration caused by the radial electromagnetic force in the air gap is the main factor of the vibration noise of permanent magnet motors. In order to suppress the vibration noise of the motor, the document "Investigation of Skewing Effects on the Vibration Reduction of Three-Phase Switched Reluctance Motors" (published in IEEE Transactions on Magnetics, 2015, 51(9):1-9) proposed to reduce the amplitude of the radial electromagnetic force by skewing the stator slots and skewing the rotor poles, thereby suppressing the vibration noise of the motor. However, this method ignores the axial unbalanced force generated by the single-step method. Later, Fu Lin et al. improved this method and proposed the step-by-step tilting method and the herringbone tilting method to solve the axial unbalanced force problem (reference paper "Reduction of vibration and acoustic noise in permanent magnet synchronous motor by optimizing magnetic forces," J. Sound Vibrat., vol. 429, pp. 193–205, Sep. 2018). In addition, some people have proposed methods such as injecting compensation current and PWM pulse width modulation technology to suppress motor vibration noise.

[0004] However, unlike conventional motors, variable-magnetic-leakage permanent-magnet synchronous motors primarily operate on magnetic field regulation. Electric vehicles operate under complex and variable conditions, and due to the large fluctuations in the magnetic field, vibration and noise are particularly prominent. Traditional methods for suppressing motor vibration and noise are not only limited in their applicability (for a single operating condition) but also often result in a reduction in the motor's output torque capacity, making them difficult to directly apply to variable-magnetic-leakage permanent-magnet synchronous motors.

[0005] Therefore, how to simultaneously achieve low vibration noise and high output torque of variable flux leakage permanent magnet synchronous motor under different working conditions is a hot and challenging issue. Summary of the Invention

[0006] The purpose of the present invention is to solve the above-mentioned series of problems existing in the traditional low-vibration and noise optimization design method that only considers a single working condition, and proposes a low-vibration and noise optimization design method for a variable-magnetic leakage permanent magnet synchronous motor that considers multiple working conditions. It can effectively suppress the vibration and noise of the motor while ensuring the wide speed regulation and high torque performance of the motor.

[0007] To achieve the above objectives, the present invention adopts a technical solution: a low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions, comprising the following steps:

[0008] Step 1) analyzing the magnetic circuit distribution of the permanent magnet motor under different working conditions to obtain the permanent magnet variable leakage flux, and adjusting the change of the permanent magnet leakage flux to achieve the torque, wide speed regulation range, and low vibration and noise requirements of the motor under different working conditions;

[0009] Step 2) introducing a variable leakage magnetic structure to achieve controllable leakage magnetic field and provide an initial structure of the motor;

[0010] Step 3) deriving the radial electromagnetic force function of the variable flux leakage permanent magnet synchronous motor, analyzing the electromagnetic vibration characteristics of the motor under different operating conditions, and obtaining relevant data on the lowest non-zero-order electromagnetic force and other performance;

[0011] Step 4) Evaluate the impact of key motor parameters on electromagnetic performance, determine the range of variation of key design variables, select typical operating conditions based on the actual operating mode of the electric vehicle, evaluate the performance requirements of the motor under different operating conditions, determine variable targets, and formulate constraints;

[0012] Step 5) The final design variable size of the motor is determined through a multi-objective genetic algorithm, so as to achieve a low-noise design of the motor under different working conditions while ensuring the basic electromagnetic torque performance of the motor.

[0013] Furthermore, in step 1), when analyzing the magnetic circuit distribution of the permanent magnet motor under different working conditions, a simplified d-axis and q-axis equivalent magnetic circuit and q-axis variable leakage magnetic reluctance R are given according to the magnetic circuit direction of the motor. σ and permanent magnet leakage flux Φ σ The relational expression can be expressed as follows:

[0014]

[0015] Where N is the number of turns of the armature winding, R g is the air gap reluctance, R r is the rotor reluctance, R s is the stator reluctance, R pm is the permanent magnet reluctance, i q is the q-axis armature current, Φ pm , Φ q are the permanent magnet flux and the flux generated by the q-axis current respectively.

[0016] When the motor is under heavy load, according to formula (2), it is necessary to obtain a larger q-axis leakage magnetic reluctance R while increasing the q-axis current. σ To block the permanent magnet leakage flux, improve the permanent magnet effective magnetic potential, and increase the torque output capacity of the motor; at high speed and light load, as the induced electromotive force increases, the armature current decreases. According to formula (2), a lower leakage magnetic reluctance R is required. σ , causing a large amount of magnetic flux leakage from the permanent magnet, weakening the effective magnetic potential of the permanent magnet and increasing the speed regulation range of the motor. At the same time, due to the weakening of the air gap magnetic field, the amplitude of the electromagnetic force will also decrease, which to a certain extent also improves the vibration and noise problem of the motor.

[0017] Furthermore, in the variable magnetic leakage structure in step 2), a rounded triangular magnetic barrier 6 and an arc-shaped magnetic barrier 7 are provided on the q-axis of the rotor to achieve controllable magnetic leakage, which form two magnetic leakage areas with the V-shaped permanent magnets to achieve self-leakage of the V-shaped permanent magnets and inter-pole leakage. At the same time, in order to avoid invalid magnetic leakage of the permanent magnets, an arc-shaped magnetic barrier 8 is added between the V-shaped permanent magnets on the d-axis.

[0018] Furthermore, in step 3), the influence of the leakage flux structure is introduced to derive the radial electromagnetic force function of the variable leakage flux permanent magnet synchronous motor under different working conditions.

[0019] Radial electromagnetic force function F considering the influence of leakage flux variation r (θ,t):

[0020]

[0021] Where, f PM (θ,t),f ARM(θ, t) are the permanent magnet magnetomotive force and the armature magnetomotive force, respectively. Λ(θ) is the air gap permeability considering the slotting effect. θ is the mechanical angle. t is the time. μ0=4π×10 -7 is the vacuum permeability, Φ pmi , Φ σi are the i-th permanent magnet flux and the i-th permanent magnet leakage flux, respectively, F k are the kth harmonic amplitudes of the armature magnetomotive force, i and k are the harmonic orders of the permanent magnet magnetomotive force and the armature magnetomotive force, p and a are the number of motor pole pairs and the number of motor units, respectively. Here, p = a = 4, ω1 and ω2 are the current angular frequencies under different working conditions, and c k is the direction of motor rotation.

[0022] Furthermore, in step 5), the key variables and optimization targets of the low vibration and noise optimization design are determined according to the working conditions. According to the actual driving cycle of the new European electric vehicle, the operating conditions of the electric vehicle can be divided into four operating areas: low-speed and heavy-load operating area, frequent starting operating area, normal driving operating area, and high-speed cruising operating area; combined with the working characteristics of the motor, through its speed and torque diagram, typical working conditions are selected, such as the working points of "rated load" and "high-speed and light load": A(1.0n rated ,1.0T rated ),B(3.3n rated ,0.4T rated ). Where n rated is the rated speed of the motor, T rated is the rated torque of the motor.

[0023] Furthermore, the low noise optimization design method flow determines the variables under rated working conditions according to the working principle and structural characteristics of the motor: x1, x2…x m , variables under high-speed conditions: x1, x2…x n (x is the design variable, m, n are positive integers), and the optimization objectives f1(x), f2(x)…f a (x) and f1(x),f2(x)…f b (x)(f(x) is the optimization target, a, b are positive integers), first perform the design variable disturbance analysis, and select the strong disturbance variable set (x1, x2…x i ), and the set of weak perturbation variables (x1, x2…x m-i ), the set of strong disturbance variables under high-speed conditions (x1, x2…x j ), and the set of weak perturbation variables (x1, x2…x n-j )(i, j are positive integers less than m and n respectively). Then, for the strong disturbance variables under different working conditions, the initial populations under different working conditions are obtained through inheritance and mutation, that is, the initial population H under the rated working condition rated_1[x1,x2…x i ],H rated_2 [x1,x2…x i ]…H rated_e [x1,x2…x i ]; The initial population H under high-speed conditions high_1 [x1,x2…x j ],H high_2 [x1,x2…x j ]…H high_e [x1,x2…x j ] (H is the initial population, e is the population size), where x1[f1(x1),f2(x1)…f a (x1)],x2[f1(x2),f2(x2)…f a (x2)]…x i [f1(x m ),f2(x m )…f a (x m )]; Under high-speed conditions, x1[f1(x1),f2(x1)…f b (x1)],x2[f1(x2),f2(x2)…f b (x2)]…x j [f1(x n ),f2(x n )…f b (x n )] represents an individual in the population. Then, through screening, optimal solutions are obtained under different operating conditions. The intersection of the optimal solution variable sets under two operating conditions is taken as the optimized size of the strong perturbation variable. For the remaining weak perturbation variables, a deterministic optimization design approach is then used to make trade-offs. Ultimately, the sizes of all design variables are determined.

[0024] The beneficial effects of the present invention after adopting the above technical solution are:

[0025] 1. The present invention introduces a variable leakage magnetic motor structure and designs a permanent magnet synchronous motor with controllable regional leakage magnetic flux. When the motor is in the "low-speed and heavy-load" working condition, the q-axis permanent magnet inter-pole magnetic bridge area and the self-leakage magnetic flux area are saturated, the permanent magnet inter-pole leakage magnetic flux and self-leakage magnetic flux are reduced, the d-axis effective magnetic flux is increased, and the torque output capacity is improved; when the motor is in the "high-speed cruising" working condition, the magnetic resistance of the q-axis permanent magnet inter-pole magnetic bridge area and the self-leakage magnetic flux area is reduced, the permanent magnet inter-pole leakage magnetic flux and self-leakage magnetic flux are increased, the effective magnetic flux is reduced, and the air gap magnetic field is weakened, which not only improves the motor speed regulation range, but also weakens the electromagnetic force amplitude, alleviating the vibration and noise problems of the motor.

[0026] 2. The present invention takes into account the vibration and noise problems of the motor under multiple operating conditions, and performs low-noise optimization design based on the operating requirements of the motor under different operating conditions. It solves the problems of traditional optimization methods such as lack of consideration (single operating condition), high time consumption, and unreliable optimization results, and provides a general method for low-noise design of motors with multiple operating modes.

[0027] 3. The present invention introduces a multi-variable and multi-objective genetic algorithm, which can directly and effectively suppress the vibration noise of the motor while ensuring basic electromagnetic performance, thereby improving the optimization efficiency of the overall motor design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be described in further detail below based on the accompanying drawings and specific embodiments;

[0029] Figure 1 This is a flow chart of a low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions according to the present invention;

[0030] Figure 2 Schematic diagram of the equivalent magnetic circuit of the motor's direct and quadrature axes;

[0031] Figure 3 This is a radial cross-sectional structural diagram of the variable flux leakage permanent magnet synchronous motor of the present invention and its magnetic circuit flow diagram. Figure 3 (a)-motor topology, Figure 3 (b)-Magnetic circuit flow direction under different working conditions;

[0032] Figure 4 It is the time-space distribution diagram of the radial electromagnetic force harmonics of the motor under different working conditions;

[0033] Figure 5 It is an enlarged schematic diagram of the local structure of the motor rotor and a speed and torque area diagram. Figure 5 (a) - Partial enlarged view of the rotor side, Figure 5 (b) - Speed ​​and torque operating area diagram;

[0034] Figure 6 It is a set of optimal solution parameters under typical working conditions obtained based on multi-objective optimization genetic algorithm. Figure 6 (a)-rated operating conditions, Figure 6 (b)-High speed and light load, Figure 6 (c) - parameter sets under different operating conditions;

[0035] Figure 7 This is a comparison chart of the performance effects before and after the low-noise optimization design. Figure 7 (a)-Output torque under rated working conditions, Figure 7 (b)-Output torque at high speed and light load, Figure 7 (c)-Vibration acceleration under rated working conditions, Figure 7(d) - vibration acceleration under high speed and light load;

[0036] In the attached figure: 1. stator; 2. rotor; 3. armature winding; 4. straight-line NdFeB permanent magnet; 5. V-shaped NdFeB permanent magnet; 6. rounded triangle magnetic barrier; 7. q-axis arc magnetic barrier; 8. d-axis arc magnetic barrier; 9. rotating shaft. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings.

[0038] See also Figure 1 , flow chart of the method for low-noise optimization design. Step 1: First, determine the design variable object to be optimized and its constraint range, then select typical working points based on the speed and torque diagram, and then determine the optimization objectives and constraints based on the operating requirements of different working conditions. Step 2: Perform disturbance analysis between design variables and performance, perform further genetic algorithms on high-disturbance variables, and use deterministic optimization design methods for low-disturbance variables, and finally obtain the optimal solution set under typical working conditions. Step 3: Intersect the optimal solution sets under the two working conditions, select candidate points, and then perform performance evaluation to finally determine the size of the optimized design variables.

[0039] An implementation example of the present invention is provided below:

[0040] Step 1: See Figure 2 , the d-axis and q-axis equivalent magnetic circuit diagram of the variable leakage permanent magnet synchronous motor, where the d-axis and q-axis magnetic flux paths are shown at different rotor positions. The equivalent magnetic circuit diagram of the traditional permanent magnet motor is analyzed by the equivalent magnetic circuit method, and the equivalent magnetic circuit of the permanent magnet synchronous motor considering variable leakage magnetic flux is given, and the q-axis variable leakage magnetic reluctance R σ and permanent magnet leakage flux Φ σ The relational expression can be expressed as follows:

[0041]

[0042] Where N is the number of turns of the armature winding, R g is the air gap reluctance, R r is the rotor reluctance, R s is the stator reluctance, R pm is the permanent magnet reluctance, i q is the q-axis armature current, Φ pm , Φ q are the permanent magnet flux and the flux generated by the q-axis current respectively.

[0043] When the motor is under heavy load, a large armature current and a high permanent magnet effective magnetic potential are required to ensure the torque output capacity of the motor. According to formula 2, it is necessary to obtain a larger q-axis leakage magnetic reluctance R while increasing the q-axis current. σTo block the permanent magnet leakage flux, improve the permanent magnet effective magnetic potential, and increase the torque output capacity of the motor; at high speed and light load, as the induced electromotive force increases, the armature current decreases. According to formula 2, a lower leakage magnetic reluctance R is required. σ , causing a large amount of magnetic flux leakage from the permanent magnet, weakening the effective magnetic potential of the permanent magnet and increasing the speed regulation range of the motor. At the same time, due to the weakening of the air gap magnetic field, the amplitude of the electromagnetic force will also decrease, which to a certain extent also improves the vibration and noise problem of the motor.

[0044] Step 2: See Figure 3 (a) Based on the variable magnetic leakage principle of step 1, the present invention provides a variable magnetic leakage permanent magnet synchronous motor, which mainly includes an outer stator 1, an inner rotor 2, and a rotating shaft 9. The outer stator is wound with an armature winding 3, and the inner rotor is embedded with four pairs of straight-pole NdFeB permanent magnets 4 and V-shaped NdFeB permanent magnets 5. The magnetization direction of each pole permanent magnet is consistent, and all adopt a tangential magnetization method. To achieve controllable magnetic leakage, a rounded triangular magnetic barrier 6 and an arc-shaped magnetic barrier 7 are opened on the q-axis of the rotor side. Together with the V-shaped permanent magnet, they form two magnetic leakage areas, achieving self-leakage of the V-shaped permanent magnet and inter-pole leakage. To ensure the basic torque performance of the motor, a straight-pole permanent magnet structure is added to the d-axis. It does not participate in magnetic leakage, and the permanent magnet flux completely enters the air gap to generate torque. At the same time, to prevent ineffective magnetic leakage of the permanent magnets, an arc-shaped magnetic barrier 8 is added between the V-shaped permanent magnets on the d-axis.

[0045] join Figure 3 (b) The magnetic path of the motor under typical operating conditions. It can be found that when unloaded, the q-axis leakage flux path is in a low saturation state, with low reluctance. The V-shaped permanent magnet forms two leakage flux regions on the q-axis: self-leakage and inter-pole leakage. Under heavy load, due to the large q-axis load current, the q-axis magnetic bridge is saturated, the reluctance is large, and the q-axis leakage flux path is blocked. The permanent magnet flux enters the air gap to generate torque, meeting the motor's high torque requirement under heavy load. Under light load, due to the small q-axis load current, the leakage flux path is in a low saturation state, with low reluctance. The V-shaped permanent magnet forms two leakage flux regions on the q-axis: self-leakage and inter-pole leakage. These two leakage flux regions jointly weaken the air gap magnetic field, increasing the motor's speed regulation range. Due to the weakened magnetic field, the electromagnetic force amplitude is also reduced, thereby improving the motor's vibration and noise problems. At the same time, under different operating conditions, the magnetic path of the d-axis straight permanent magnet enters the air gap and does not participate in the leakage flux, which to a certain extent ensures the basic torque performance of the motor.

[0046] Step 3: See Figure 4 , is the spatial and temporal distribution diagram of the radial electromagnetic force of the variable flux leakage permanent magnet synchronous motor under low speed and heavy load and high speed and light load conditions, and determines the lowest non-zero order electromagnetic force F r_4th .

[0047] According to Maxwell's stress tensor method, the radial electromagnetic force function F r (θ,t) can be changed into:

[0048]

[0049] Where B r is the radial air gap flux density, B t It is the tangential air gap flux density. Since the tangential air gap flux density B of the traditional built-in permanent magnet synchronous motor is t The amplitude is small, so it can generally be ignored; f PM (θ,t),f ARM (θ, t) are the permanent magnet magnetomotive force and the armature magnetomotive force, respectively. Λ(θ) is the air gap permeability considering the slotting effect. θ is the mechanical angle. t is the time. μ0=4π×10 -7 is the magnetic permeability of vacuum.

[0050] Furthermore, the permanent magnet magnetomotive force f PM (θ, t) and armature magnetomotive force f ARM (θ, t), and the air gap permeability Λ(θ) can be expressed as:

[0051]

[0052] Substituting formulas (4), (5), and (6) into formula (3), we can obtain the radial electromagnetic force function F r (θ,t) expansion:

[0053]

[0054] Where B r is the radial air gap flux density, f PM (θ,t),f ARM (θ, t) are the permanent magnet magnetomotive force and the armature magnetomotive force, respectively. Λ(θ) is the air gap permeability considering the slotting effect. θ is the mechanical angle. t is the time. μ0=4π×10 -7 is the vacuum permeability, i and k are the harmonic orders of permanent magnet magnetomotive force and armature magnetomotive force respectively, F i and F k are the amplitude of the i-th permanent magnet magnetomotive force harmonic and the k-th armature magnetomotive force harmonic, p and a are the number of motor pole pairs and the number of motor units, respectively, where p = a = 4; Λ0 is the average permeability of the air gap, Λ j is the jth permeability harmonic amplitude, j is a positive integer, ω is the current angular frequency, c k is the direction of motor rotation, N ST is the number of stator slots in the motor.

[0055] Considering the influence of the leakage flux structure, Equations (1) and (2) are substituted into the permanent magnet magnetomotive force (4) to obtain the permanent magnet magnetomotive force f of the variable leakage flux permanent magnet synchronous motor. PM (θ,t):

[0056]

[0057] Similarly, substitute (8) into the radial electromagnetic force function F r (θ,t), we get:

[0058]

[0059]

[0060] By deducing the formula, we can know that the radial electromagnetic force F r The main sources of (θ, t) can be divided into permanent magnetic field, armature magnetic field and air gap magnetic permeance. Due to the influence of the leakage magnetic structure, the radial electromagnetic force has no leakage magnetic flux under low speed and heavy load conditions. pm , the electromagnetic force amplitude is higher; and under high speed and light load conditions, there is a large amount of leakage magnetic flux Φ σ , so the electromagnetic force amplitude is lower. At the same time, due to the weakening of the magnetic field, the current angular velocity ω increases, and the frequency distribution of the electromagnetic force expands to medium and high frequencies, such as Figure 3 shown.

[0061] Since the electromagnetic vibration of the permanent magnet motor is inversely proportional to the fourth power of the order of the electromagnetic force, the lowest non-zero-order electromagnetic force of the radial electromagnetic force has the greatest impact on the electromagnetic vibration noise of the permanent magnet motor. It is necessary to determine the lowest non-zero-order (4th-order) radial electromagnetic force and use it as one of the optimization targets.

[0062] Step 4: See Figure 5 (a) is a local structural diagram of the motor rotor side. From step 1, it can be seen that the q-axis magnetic barrier is the key factor for the motor to realize the variable leakage magnetic principle. And from step 2, it is also known that the leakage magnetic structure has a great influence on the electromagnetic performance of the motor. Therefore, the length R1 from the q-axis rounded triangle magnetic barrier to the center O1, the height R2 of the q-axis rounded triangle magnetic barrier, the width R1tanθ1 of the q-axis rounded triangle, the inner radius R3 and outer radius R4 of the q-axis arc-shaped magnetic barrier, the inner half angle θ2 of the q-axis arc-shaped magnetic barrier, the distance R6 and length R7 from the d-axis straight permanent magnet to the center O2, and the distance R8 and length R9 from the V-shaped permanent magnet to the center O2 are selected as the design variables of the present invention. Then, based on the constraints between the structural parameters, the constraint range of the design variables is finally determined, such as 2mm≤R1≤6mm, 1.1mm≤R2≤2.7mm, 15deg≤θ1≤27deg, 11.2mm≤R3≤15.6mm, 12.2mm≤R4≤17.6mm, 25deg≤θ2≤30deg, and 2mm≤R6≤6mm.

[0063] join Figure 5(b), speed-torque range diagram of the motor. According to the New European Electric Driving Cycle (NEDC), the operating conditions of electric vehicles can be roughly divided into four operating areas, namely the low-speed and heavy-load operating area, the frequent starting operating area, the normal driving operating area, and the high-speed cruising operating area. Theoretically, each operating area has its own unique operating requirements, which is different from the traditional design method that only considers the rated operating conditions. Therefore, how to meet the basic electromagnetic performance requirements under different operating conditions while suppressing its electromagnetic vibration is of great significance. Each operating area is a collection of multiple operating points, and considering all operating points and performing low-noise optimization design on them is currently difficult to achieve. Therefore, according to the working principle of permanent magnet motors, the present invention finally selects two typical operating points of "rated load" and "high-speed light load" as further research objects, such as: A(1.0n rated ,1.0T rated ),B(3.3n rated ,0.4T rated ). Where n rated is the rated speed of the motor, T rated is the rated torque of the motor.

[0064] Then, according to step 2, based on the operating requirements of the typical working condition, select the lowest non-zero-order radial electromagnetic force F under the typical working condition r_4th , output torque T avg , torque ripple T ripple As the optimization goal, a multi-variable, multi-objective low vibration and noise optimization design method is constructed.

[0065] Step 5: Determine the design variables under different working conditions: variables x1, x2…x under rated working conditions m , variables x1, x2…x under high-speed conditions n (x is the design variable, m, n are positive integers), and the optimization objectives f1(x), f2(x)…f a (x) and f1(x),f2(x)…f b (x) (f(x) is the optimization target, a, b are positive integers), first perform the design variable disturbance analysis, screen out the strong disturbance variable set (R1, θ1, R6) and the weak disturbance variable set (R2, R3, R4, θ2) under the rated working condition, the strong disturbance variable set (R1, θ1, R6) and the weak disturbance variable set (R2, R3, R4, θ2) under the high-speed working condition. Then, for the strong disturbance variables under different working conditions, through genetics and mutation, the initial population under different working conditions is obtained, that is, H under the rated working condition. rated_1 [R1,θ1,R6],H rated_2 [R1,θ1,R6]…H rated_e [R1,θ1,R6]; H under high speed conditionhigh_1 [R1,θ1,R6],H high_2 [R1,θ1,R6]…H high_e [R1,θ1,R6] (H is the initial population, e is the population size, here it is 100), where l e [F r_4th ,T avg ,T ripple ],w e [F r_4th ,T avg ,T ripple ]…h c [F r_4th ,T avg ,T ripple ] is an individual in the population. The optimization model and constraints constructed based on the design variables and optimization objectives are as follows:

[0066]

[0067] refer to Figure 6 After screening, we obtained a set of optimal solutions under different operating conditions. The intersection of the optimal solution variable sets under two operating conditions was then taken as the final optimized size. We then used a deterministic optimization design approach to balance the remaining weak disturbance variables. The final optimized design variable sizes for the motor were: R1 = 5mm, R2 = 1.28mm, θ1 = 45deg, R3 = 14.2mm, R4 = 16.07mm, θ2 = 28deg, and R6 = 5.87mm.

[0068] refer to Figure 7 At this time, the torque of the motor under rated working conditions increases from 26.4Nm to 28.2Nm, the torque ripple decreases from 9.5% to 3.7%, and the vibration acceleration peak value decreases from 2.2×10 3 mm / s 2 Reduced to 0.6×10 3 mm / s 2 At the same time, the torque under high-speed and light-load conditions increased from 10.4Nm to 10.6Nm, the torque ripple decreased from 26% to 17%, and the vibration acceleration peak value decreased from 7.5×10 3 mm / s 2 Reduced to 5.8×10 3 mm / s 2 It can be seen that the optimized variable leakage magnetic motor can achieve the characteristics of low vibration noise and high reliability under different working conditions while ensuring the basic torque performance.

[0069] The series of detailed descriptions listed above are based on Figure 2 The present invention is not limited to the motor case in FIG. Figure 2The above is not only applicable to the case of permanent magnet motors, but also to permanent magnet motors with other structures.

Claims

1. A low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions, characterized in that: The steps include: Step 1) analyzing the magnetic circuit distribution of the permanent magnet motor under different working conditions to obtain the permanent magnet variable leakage flux, and adjusting the change of the permanent magnet leakage flux to achieve the torque, wide speed regulation range, and low vibration and noise requirements of the motor under different working conditions; Step 2) introducing a variable leakage magnetic structure to achieve controllable leakage magnetic field and provide an initial structure of the motor; Step 3) deriving the radial electromagnetic force function of the variable flux leakage permanent magnet synchronous motor, analyzing the electromagnetic vibration characteristics of the motor under different operating conditions, and obtaining relevant data on the lowest non-zero-order electromagnetic force performance; Step 4) Evaluate the impact of key motor parameters on electromagnetic performance, determine the range of variation of key design variables, select typical operating conditions based on the actual operating mode of the electric vehicle, evaluate the performance requirements of the motor under different operating conditions, determine variable targets, and formulate constraints; Step 5) Determine the final design variable size of the motor through a multi-objective genetic algorithm, while ensuring the basic electromagnetic torque performance of the motor and achieving low vibration and noise design of the motor under different working conditions; In step 1), when analyzing the magnetic circuit distribution of the permanent magnet motor under different working conditions, the simplified d and q axis equivalent magnetic circuits and the q axis variable leakage magnetic reluctance R are given according to the magnetic circuit direction of the motor. σ and permanent magnet leakage flux Φ σ The relational expression can be expressed as follows: Where N is the number of turns of the armature winding, R g is the air gap reluctance, R r is the rotor reluctance, R s is the stator reluctance, R pm is the permanent magnet reluctance, I q is the q-axis armature current, Φ pm , Φ q are the permanent magnet flux and the flux generated by the q-axis current respectively; When the motor is under heavy load, according to formula (2), it is necessary to obtain a larger q-axis leakage magnetic reluctance R while increasing the q-axis current. σ To block the permanent magnet leakage flux, improve the permanent magnet effective magnetic potential, and increase the torque output capacity of the motor; at high speed and light load, as the induced electromotive force increases, the armature current decreases. According to formula (2), a lower leakage magnetic reluctance R is required. σ , causing a large amount of magnetic flux leakage from the permanent magnet, weakening the effective magnetic potential of the permanent magnet and increasing the speed regulation range of the motor. At the same time, due to the weakening of the air gap magnetic field, the amplitude of the electromagnetic force will also decrease, which to a certain extent also improves the vibration and noise problem of the motor.

2. The low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions according to claim 1 is characterized by: In step 2), the variable magnetic leakage structure is provided with a rounded triangular magnetic barrier 6 and an arc-shaped magnetic barrier 7 on the q-axis of the rotor to achieve controllable magnetic leakage. These magnetic barriers 6 and the arc-shaped magnetic barrier 7 together with the V-shaped permanent magnets form two magnetic leakage areas, thereby achieving self-leakage of the V-shaped permanent magnets and inter-pole leakage. At the same time, to avoid invalid magnetic leakage of the permanent magnets, an arc-shaped magnetic barrier 8 is added between the V-shaped permanent magnets on the d-axis.

3. The low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions according to claim 1 is characterized by: In step 3), the influence of the leakage flux structure is introduced to derive the radial electromagnetic force function of the variable leakage flux permanent magnet synchronous motor under different working conditions. Radial electromagnetic force function F considering the influence of leakage flux variation r (θ,t): Where, f PM (θ,t),f ARM (θ, t) are the permanent magnet magnetomotive force and the armature magnetomotive force, respectively. Λ(θ) is the air gap permeability considering the slotting effect. θ is the mechanical angle. t is the time. μ0=4π×10 -7 is the vacuum permeability, Φ pmi , Φ σi are the i-th permanent magnet flux and the i-th permanent magnet leakage flux, respectively, F k are the kth harmonic amplitudes of the armature magnetomotive force, i and k are the harmonic orders of the permanent magnet magnetomotive force and the armature magnetomotive force, p and a are the number of motor pole pairs and the number of motor units, respectively. Here, p = a = 4, ω1 and ω2 are the current angular frequencies under different working conditions, and c k is the direction of motor rotation.

4. The low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions according to claim 1 is characterized by: In step 5), the key variables and optimization targets of the low vibration and noise optimization design are determined according to the working conditions. According to the actual driving cycle of the new European electric vehicle, the operating conditions of the electric vehicle can be divided into four operating areas: low-speed and heavy-load operating area, frequent starting operating area, normal driving operating area, and high-speed cruising operating area. Combined with the working characteristics of the motor, through its speed and torque diagram, typical working conditions such as "rated load" and "high-speed and light-load" are selected: A(1.0n rated ,1.0T rated ),B(3.3n rated ,0.4T rated ); where n rated is the rated speed of the motor, T rated is the rated torque of the motor.

5. The low-noise optimization design method for a variable-magnetic-leakage permanent-magnet synchronous motor considering multiple operating conditions according to claim 4 is characterized in that: The method flow of low noise optimization design is as follows: According to the working principle and structural characteristics of the motor, determine the variables under rated working conditions: x1, x2…x m , variables under high-speed conditions: x1, x2…x n , where x is the design variable, m, n are positive integers, and the optimization objectives f1(x), f2(x)…f a (x) and f1(x),f2(x)…f b (x)(f(x) is the optimization target, a, b are positive integers), first perform the design variable disturbance analysis, and select the strong disturbance variable set (x1, x2…x i ), and the set of weak perturbation variables (x1, x2…x m-i ), the set of strong disturbance variables under high-speed conditions (x1, x2…x j ), and the set of weak perturbation variables (x1, x2…x n-j )(i,j are positive integers less than m,n respectively); Then, for the strong disturbance variables under different working conditions, the initial populations under different working conditions are obtained through inheritance and mutation, that is, the initial population H under the rated working condition rated_1 [x1,x2…x i ],H rated_2 [x1,x2…x i ]…H rated_e [x1,x2…x i ]; The initial population H under high-speed conditions high_1 [x1,x2…x j ],H high_2 [x1,x2…x j ]…H high_e [x1,x2…x j ] (H is the initial population, e is the population size), where x1[f1(x1),f2(x1)…f a (x1)],x2[f1(x2),f2(x2)…f a (x2)]…x i [f1(x m ),f2(x m )…f a (x m )]; Under high-speed conditions, x1[f1(x1),f2(x1)…f b (x1)],x2[f1(x2),f2(x2)…f b (x2)]…x j [f1(x n ),f2(x n )…f b (x n )] are individuals in the population; Then, after screening, the optimal solution set under different working conditions is obtained, and the intersection of the optimal solution variable sets under the two working conditions is taken as the size of the optimized strong disturbance variable. Then, for the remaining weak disturbance variables, a deterministic optimization design method is adopted to make trade-offs and finally determine the size of all design variables.

6. A variable flux leakage permanent magnet synchronous motor considering multiple working conditions, characterized in that: The method according to any one of claims 1 to 5 mainly includes an outer stator 1, an inner rotor 2, and a rotating shaft 9, wherein the outer stator is wound with an armature winding 3, and the inner rotor is embedded with four pairs of inline NdFeB permanent magnets 4 and V-shaped NdFeB permanent magnets 5, the magnetization direction of each pole permanent magnet is consistent, and tangential magnetization is adopted; in order to achieve controllable leakage flux, a rounded triangular magnetic barrier 6 and an arc-shaped magnetic barrier 7 are opened on the q-axis on the rotor side, forming two leakage flux areas with the V-shaped permanent magnet, realizing self-leakage flux and inter-pole leakage flux of the V-shaped permanent magnet, and in order to ensure the basic torque performance of the motor, an inline permanent magnet structure is added to the d-axis, which does not participate in the leakage flux, and the permanent magnet flux completely enters the air gap to generate torque. At the same time, in order to avoid invalid leakage flux of the permanent magnet, an arc-shaped magnetic barrier 8 is added between the V-shaped permanent magnets on the d-axis.

Images