Dual-rotor Flux-Switching Permanent Magnet Machine and Optimization Method

Abstract

The present invention belongs to the technical field of mechanical rotors, and discloses a dual-rotor flux-switching permanent magnet motor and an optimization method. The present invention determines the number of phase group modules of the dual-rotor flux-switching permanent magnet motor, obtains the grid harmonics according to the number of phase group modules, determines the internal torque of the inner rotor and the external torque of the outer rotor, obtains the fundamental frequency of the motor according to the rotor pole number and speed, obtains the electrical period according to the fundamental frequency of the motor, performs Fourier analysis on the grid harmonics in the electrical periods of the internal torque and the external torque, obtains the harmonic suppression, analyzes the harmonic suppression to obtain the target harmonic suppression, performs simulation analysis on the target harmonic suppression to obtain the effective shift angle, and decouples the effective shift angle to obtain the target shift angle, and optimizes the dual-rotor flux-switching permanent magnet motor according to the target shift angle, realizing the combination of the internal and external motors, improving the integration degree of the dual motors, and also improving the flux coupling rate of the dual motors.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical rotors, and particularly to a dual-rotor flux-switching permanent magnet motor and an optimization method thereof. Background Art

[0002] With the increasing depletion of oil energy and the pressure of a sharp increase in air pollutants, fuel vehicles with large pollutant emissions have gradually been replaced by new energy vehicles. Among them, new energy vehicles relying on hybrid and pure electric technologies have received extensive attention. Although fuel cell and pure electric vehicles have advantages such as cleanliness and quietness that traditional fuel vehicles do not have, the short battery life and the high price of hydrogen fuel severely limit their application and popularization. Therefore, hybrid vehicles, which combine the advantages of fuel and pure electric vehicles, can achieve driving goals such as reducing the fuel consumption of the whole vehicle, extending the service life of the battery, and minimizing exhaust emissions by combining advanced energy management strategies. However, the current mainstream motor configuration is the parallel connection of a generator P1 and a drive motor P3. However, this motor configuration has high requirements for the layout space of the whole vehicle, which is not conducive to the space layout of new energy vehicles.

[0003] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The main purpose of the present invention is to provide a dual-rotor flux-switching permanent magnet motor and an optimization method thereof, aiming to solve the technical problem in the prior art that the motor of a hybrid vehicle has a large amount of space waste, resulting in an inability to meet the tight space of new energy vehicles.

[0005] To achieve the above object, the present invention provides a dual-rotor flux-switching permanent magnet motor, characterized in that the dual-rotor flux-switching permanent magnet motor includes an inner rotor, an outer rotor, and an intermediate stator. The intermediate stator includes a stator core, and permanent magnets are disposed on both sides of the stator core. The stator core includes a plurality of tooth portions, and excitation windings are disposed between adjacent tooth portions. The electrical angle of the center line arc width of adjacent tooth portions is π.

[0006] Optionally, the inner rotor and the outer rotor are fixedly connected to the same motor shaft through a mechanical tooling, and the intermediate stator is fixed to the motor housing.

[0007] Optionally, the electronic core of the intermediate stator is an E-shaped stator core, and the permanent magnet is an I-shaped permanent magnet.

[0008] In addition, to achieve the above object, the present invention also proposes an optimization method for a dual-rotor flux-switching permanent magnet motor, characterized in that the dual-rotor flux-switching method is applied to the dual-rotor flux-switching permanent magnet motor according to any one of claims 1-3. The dual-rotor flux-switching motor optimization method includes:

[0009] Determine the number of phase group modules of the dual-rotor flux-switching permanent magnet machine, and obtain the grid harmonics according to the number of phase group modules;

[0010] Determine the inner torque of the inner rotor and the outer torque of the outer rotor;

[0011] Obtain the fundamental frequency of the motor according to the number of rotor poles and the rotational speed, and obtain the electrical period according to the fundamental frequency of the motor;

[0012] Perform Fourier analysis on the grid harmonics in the electrical periods of the inner torque and the outer torque to obtain the suppressed harmonics;

[0013] Analyze the suppressed harmonics to obtain the target suppressed harmonics;

[0014] Perform simulation analysis on the target suppressed harmonics to obtain the effective shift angle, and decouple the effective shift angle to obtain the target shift angle;

[0015] Optimize the dual-rotor flux-switching permanent magnet machine according to the target shift angle.

[0016] Optionally, the determining the inner torque of the inner rotor and the outer torque of the outer rotor includes:

[0017] Determine the number of type-I permanent magnets and the number of phase groups;

[0018] Obtain the mechanical angle according to the electrical angle and the number of rotor poles;

[0019] Obtain the inner torque of the inner rotor according to the mechanical angle and the number of rotor poles;

[0020] Obtain the outer torque of the outer rotor according to the mechanical angle, the number of rotor poles and the phase difference.

[0021] Optionally, before obtaining the mechanical angle according to the electrical angle and the number of rotor poles, it further includes:

[0022] Obtain the number of rotor poles according to the number of type-I permanent magnets and the number of phase groups.

[0023] Optionally, the performing Fourier analysis on the grid harmonics in the electrical periods of the inner torque and the outer torque to obtain the suppressed harmonics includes:

[0024] Determine the harmonic components of the grid harmonics;

[0025] Obtain the greatest common divisor of the number of stator slots and the number of rotor poles according to the number of stator slots and the number of rotor poles;

[0026] Obtain the order of the harmonic components according to the number of stator slots and the greatest common divisor of the number of stator slots and the number of rotor poles;

[0027] Obtain the cogging torque of the motor based on the harmonic component, the order of the harmonic component, the number of rotor poles, and the mechanical angle;

[0028] Suppress harmonics based on the cogging torque of the motor.

[0029] Optionally, the decoupling of the effective shift angle to obtain the target shift angle includes:

[0030] Analyze the effective shift angle to determine the flux harmonic content corresponding to each effective shift angle;

[0031] Obtain the total harmonic distortion value of the no-load back electromotive force based on the effective shift angle and the flux harmonic content;

[0032] Screen the total harmonic distortion value of the no-load back electromotive force to obtain the target shift angle.

[0033] Optionally, the screening of the total harmonic distortion value of the no-load back electromotive force to obtain the target shift angle includes:

[0034] Determine the no-load back electromotive force of the inner winding and the coupled induced back electromotive force of the inner winding according to the total harmonic distortion value of the no-load back electromotive force;

[0035] Obtain the back electromotive force coupling ratio according to the no-load back electromotive force of the inner winding and the coupled induced back electromotive force of the inner winding;

[0036] Determine the flux density distribution value of the inner rotor according to the total harmonic distortion value of the no-load back electromotive force;

[0037] Obtain the target shift angle according to the back electromotive force coupling ratio and the flux density distribution value of the inner rotor.

[0038] Optionally, the determining of the flux density distribution value of the inner rotor according to the total harmonic distortion value of the no-load back electromotive force includes:

[0039] Determine the unit magnetic density of the inner rotor within the electrical period according to the total harmonic distortion value of the no-load back electromotive force;

[0040] Obtain the armature magnetomotive force of the outer winding according to the unit magnetic density of the inner rotor to obtain the flux density distribution value of the inner rotor.

[0041] In addition, to achieve the above object, the present invention also proposes a dual-rotor flux-switching motor optimization device, the dual-rotor flux-switching motor optimization device includes: a memory, a processor, and a dual-rotor flux-switching motor optimization program stored on the memory and executable on the processor, the dual-rotor flux-switching motor optimization program is configured to implement the steps of the dual-rotor flux-switching motor optimization method as described above.

[0042] In addition, to achieve the above object, the present invention also provides a storage medium, on which an optimization program for a dual-rotor flux-switching motor is stored. When the optimization program for the dual-rotor flux-switching motor is executed by a processor, the steps of the optimization method for the dual-rotor flux-switching motor as described above are implemented.

[0043] The present invention determines the number of phase group modules of the dual-rotor flux-switching permanent magnet motor, obtains the power grid harmonics according to the number of phase group modules, determines the internal torque of the inner rotor and the external torque of the outer rotor, obtains the fundamental frequency of the motor according to the number of rotor poles and the rotational speed, obtains the electrical period according to the fundamental frequency of the motor, performs Fourier analysis on the power grid harmonics in the electrical periods of the internal torque and the external torque to obtain the harmonic suppression, analyzes the harmonic suppression to obtain the target harmonic suppression, performs simulation analysis on the target harmonic suppression to obtain the effective shift angle, and decouples the effective shift angle to obtain the target shift angle. The dual-rotor flux-switching permanent magnet motor is optimized according to the target shift angle, so as to realize the combination of the inner and outer motors, improve the integration degree of the dual motors, and also improve the flux coupling rate of the dual motors. Description of the Drawings

[0044] Figure 1 Schematic diagram of the parallel-axis configuration in the dual motors;

[0045] Figure 2 Schematic diagram of the concentric-axis configuration in the dual motors;

[0046] Figure 3 Schematic diagram of the structure of the stator permanent magnet motor;

[0047] Figure 4 Schematic diagram of the structure of the stator permanent magnet dual-rotor motor;

[0048] Figure 5 Schematic diagram of the structure of the improved iron-core FSPM motor;

[0049] Figure 6 Topological diagram of the dual-rotor type flux-switching motor when the shift angle is 0°;

[0050] Figure 7 Topological diagram of the dual-rotor type flux-switching motor when the shift angle is 90°;

[0051] Figure 8 Schematic diagram of the E-shaped iron core and the I-shaped permanent magnet;

[0052] Figure 9 Schematic diagram of the structure of the dual-rotor type flux-switching motor;

[0053] Figure 10 Flow chart of the first embodiment of the optimization method for the dual-rotor flux-switching motor of the present invention;

[0054] Figure 11 It is a schematic flow chart of the second embodiment of the optimization method for the dual-rotor flux-switching motor of the present invention;

[0055] Figure 12 It is a structural block diagram of the first embodiment of the optimization device for the dual-rotor flux-switching motor of the present invention.

[0056] The realization, functional characteristics and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Specific embodiments

[0057] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] As the battery capacity of hybrid vehicles is getting higher and higher, there are higher requirements for the miniaturization, integration and lightweight of the hybrid powertrain. Currently, hybrid vehicles are composed of a series-parallel configuration of an engine, a generator P1 and a drive motor P3, and form various driving modes such as pure electric drive, engine direct drive, parallel drive, series power generation, and energy recovery through mode switching, which can effectively avoid the range anxiety of pure electric vehicles and the emission anxiety of fuel vehicles. Currently, the mainstream hybrid mode is generally a P1+P3 dual-motor configuration, and an integration solution of a generator, a drive motor and a reduction gear set is realized through a parallel axis or a concentric axis. Refer to Figure 1 and Figure 2 , Figure 1 is a schematic diagram of the parallel-axis configuration in the dual-motor, Figure 2 is a schematic diagram of the concentric-axis configuration in the dual-motor.

[0059] However, the above solutions all have relatively high requirements for the layout space of the hybrid powertrain in the vehicle. Among them, the parallel-axis configuration increases the X and Z-direction spaces of the whole machine, while the concentric-axis configuration has higher requirements for the Y-direction space, which is contradictory to the tight layout space of new energy vehicles.

[0060] In addition, as the power source and moving parts of new energy vehicles, high-performance motors are the core and key to their development towards high-end. Currently, motors are mainly divided into three categories according to different excitation sources: induction motors, switched reluctance motors, and permanent magnet motors. Among them, induction motors have a simple structure, high reliability, and mature control technology, but have large eddy current losses, low power factors and efficiencies. Switched reluctance motors have mature manufacturing processes, but have large torque ripples, large system vibration and noise, especially poor low-speed and high-torque operating performance. Permanent magnet motors use permanent magnets as the excitation source, have a high power factor, and their efficiency, power and torque density are higher than those of the previous two types of motors, and have become the mainstream. Currently, permanent magnet synchronous motors are mainly rotor-type permanent magnet motors, including surface-mounted and embedded structures.

[0061] Surface-mounted type: Since the surface-mounted magnet is in direct contact with the air-gap magnetic field, under the action of the harmonic magnetic field, there is a large eddy current loss in the permanent magnet, which is likely to deteriorate the temperature rise of the permanent magnet. In addition, the surface-mounted permanent magnet motor needs to take protective measures for the permanent magnet, such as using a non-magnetic alloy sheath or carbon fiber lashing technology, which will lead to difficult heat dissipation, even irreversible demagnetization, and reduce the operation reliability. At the same time, the permanent magnet protective sleeve will increase the equivalent air-gap length and reduce the motor output torque and power density.

[0062] Embedded type: The permanent magnet is embedded in the rotor, and the rotational centrifugal compressive stress will have a certain impact on the rotor strength. The complex magnetic isolation structure also brings problems of magnetic leakage and saturation, which limits the improvement of power and torque density, and the structure design is relatively complex. Currently, most traditional permanent magnet motors use distributed windings, which have long ends, large winding resistance, and high mutual inductance among the three phases, resulting in problems such as large copper loss, low efficiency, and complex winding, and it is difficult to achieve modular fault-tolerant design of the motor.

[0063] At present, the stator permanent magnet motors mainly include doubly salient permanent magnet motors, flux reversal permanent magnet motors, and flux switching permanent magnet motors. Refer to Figure 3 , Figure 3 is the structural schematic diagram of the stator permanent magnet motor. Among them, the flux switching permanent magnet motor (Flux-Switching Permanent Magnet Motor, abbreviated as FSPM motor) has the following advantages: the stator shows a modular arrangement, with relatively small mutual inductance and high fault-tolerant ability; there is a magnetic concentration effect for the tangential relative permanent magnets, so the torque density is relatively high; the magnetomotive force of the permanent magnet is not directly in series with the armature main magnetic flux, and the demagnetization resistance ability is strong; the induced back electromotive force sinusoidality is very high, and the harmonic control degree is good.

[0064] For low-speed and high-torque working conditions, the requirement for the split ratio (the ratio of the inner and outer diameters of the motor stator) of the permanent magnet motor is relatively large, so the internal space of the motor cannot be effectively utilized. Refer to Figure 4 , Figure 4 is the structural schematic diagram of the stator permanent magnet double-rotor motor. The double-rotor permanent magnet motor with a double air-gap structure can make more flexible use of the excessive remaining space due to the addition of an air-gap layer. And the internal and external motor designs are also relatively flexible, which can be used as an auxiliary generator or a driving motor. The overall torque density of the motor is large and the anti-saturation performance is strong.

[0065] Due to the relatively large split ratio of the traditional motor, the number of stator teeth and slots is relatively large. The stator core with a split tooth structure design amplifies the number of cogging torque periods, making the harmonic amplitude of the cogging torque relatively reduced. Refer to Figure 5 , Figure 5It is a schematic structural diagram of an FSPM motor with an improved iron core. In terms of fault tolerance, the stator split-tooth structure and the E-type iron core structure have a high degree of modularity in the magnetic circuit. Therefore, compared with traditional FSPM motors, they both have higher self-inductance and lower mutual inductance, thus effectively limiting the amplitude of the short-circuit current.

[0066] The structure of the traditional dual-port FSPM motor is to design the inner and outer motors as two independent motors. After separating the permanent magnets, a magnetic isolation layer is added to the stator yoke to avoid the interference of the coupling between the inner and outer magnetic fields on the drive control as much as possible.

[0067] Combined with the above description, this embodiment proposes a high-performance dual-electron topological structure. Refer to Figure 6 Figure 7 , Figure 6 It is a topological diagram of a dual-rotor flux-switching motor when the shift angle is 0°. Figure 7 It is a topological diagram of a dual-rotor flux-switching motor when the shift angle is 90°. Combining the flux-switching principle with the dual-rotor and stator structures, this motor can be understood as a combination of an outer motor and an inner motor. By using the intermediate stator to provide a common magnetic flux circuit for the inner and outer permanent magnets respectively, the flux-switching principle is realized, thereby improving the integration degree inside the motor. Similar to the traditional flux-switching permanent magnet motor, in the topological structure of the dual-rotor flux-switching motor proposed in this embodiment, the N-pole and S-pole permanent magnets are both radially placed inside the two sides of the iron core to achieve the magnetic concentration effect. To further realize the alternating aggregation of magnetic flux and form a balanced three-phase back electromotive force, there are certain restrictions on the pole-slot coordination relationship, and there are also constraints on the circumferential geometric dimensions. To obtain the unit winding factor, the center line arc width of two adjacent tooth parts in the same iron core module is set to π electrical angle (rad). At the same time, the stator tooth width, the rotor pole width, and the inner slot width of the phase are all the same, and the unit angle θ = π / 2. From this, the phase angle difference between two adjacent coils can be obtained as 2π electrical angle. In the stator structure of the topological diagram of the dual-rotor flux-switching motor, the dual-rotor structure shares the common stator iron core and permanent magnets. Specifically, the E-type iron core and the I-type permanent magnet are used inside and between phases. Refer to Figure 8 , Figure 8 It is a schematic diagram of the E-type iron core and the I-type permanent magnet.

[0068] In the dual-rotor flux-switching motor, the two rotors need to maintain the same speed and the same direction of motion to achieve the alternating magnetic concentration effect. Therefore, during processing, they need to be fixedly connected to the same output shaft through a mechanical fixture (flange). Refer to Figure 9 , Figure 9 It is a simplified structural diagram of the dual-rotor flux-switching motor. The inner rotor and the outer rotor are fixedly connected to the same motor shaft through a mechanical fixture, and the intermediate stator is fixed to the motor housing. There is also an exciting winding between the inner and outer rotors.

[0069] The dual-rotor flux-switching permanent magnet motor proposed by the present invention is a concentric dual-rotor dual-motor configuration, which can significantly reduce the axial size and longitudinal height of the hybrid system, reserve more space for the vehicle layout, and at the same time design the permanent magnet and winding at the stator, which can make the thermal path of the motor system shorter, easier to dissipate heat, further improve the torque density, and the concentrated winding of the phase group provides a high winding factor and short end length, reduces the proportion of mutual inductance, improves the fault tolerance ability, realizes topological modularization, and the shift angle design realizes the flux alternating aggregation, which can effectively improve the utilization rate of permanent magnets and effectively suppress the cogging torque.

[0070] An embodiment of the present invention provides an optimization method for a dual-rotor flux-switching motor, referring to Figure 10 , Figure 10 which is a schematic flow chart of the first embodiment of an optimization method for a dual-rotor flux-switching motor of the present invention.

[0071] In this embodiment, the optimization method for the dual-rotor flux-switching motor includes the following steps:

[0072] Step S10: Determine the number of phase group modules of the dual-rotor flux-switching permanent magnet motor, and obtain the grid harmonics according to the number of phase group modules.

[0073] It should be noted that the execution subject of this embodiment is an optimization device for a dual-rotor flux-switching motor. Among them, the optimization device for a dual-rotor flux-switching motor has functions such as data processing, data communication, and program operation. The optimization device for a dual-rotor flux-switching motor can be an integrated controller, a control computer, etc. Of course, it can also be other devices with similar functions. This embodiment does not make any restrictions on this.

[0074] It can be understood that the number of phase group modules of the dual-rotor flux-switching permanent magnet motor refers to the number of groups of internal coils in the dual-rotor flux-switching permanent magnet motor. When the number of phase group modules of the dual-rotor flux-switching permanent magnet motor is three, that is, the dual-rotor flux-switching permanent magnet motor is a three-phase motor, and the step angle in the three-phase motor is 0.75° / 1.5°. Grid harmonics refer to the components greater than the fundamental frequency obtained by Fourier series decomposition of periodic sinusoidal alternating quantities. Grid harmonics will cause a decrease in power factor, power loss, etc., that is, it will cause waste of electric energy.

[0075] In specific implementation, according to the dual-rotor flux-switching permanent magnet motor, the number of coils in a phase group can be determined and the corresponding number of phase groups . Among them, the number of coils in a phase group is also the number of I-shaped permanent magnets. According to the characteristics of the modular phase group of the stator core structure, the number of stator slots can be corrected to the number of phase group modules, that is . Combining with the pole-slot matching formula, it can be obtained that:

[0076]

[0077] Among them, is the number of stator slots, is the number of rotor poles, is the number of stator slots and the number of rotor poles the greatest common divisor, is a natural number. Relative to the modular design structure of the concentrated winding of the phase group, the cogging torque of the motor is mainly the 6k - th harmonic, that is, there are 6k wave peaks in one electrical cycle.

[0078] Step S20: Determine the internal torque of the inner rotor and the external torque of the outer rotor.

[0079] It should be noted that the internal torque refers to the torque of the inner rotor, and the external torque refers to the torque of the outer rotor. When determining the torque of the rotor, the torque can be obtained by dividing the mechanical power output by the rotor by the mechanical angular velocity of the rotor.

[0080] Furthermore, the determination of the internal torque of the inner rotor and the external torque of the outer rotor includes:

[0081] Determine the number of type - I permanent magnets and the number of phase groups;

[0082] Obtain the mechanical angle according to the electrical angle and the number of rotor poles;

[0083] Obtain the internal torque of the inner rotor according to the mechanical angle and the number of rotor poles;

[0084] Obtain the external torque of the outer rotor according to the mechanical angle, the number of rotor poles and the phase difference.

[0085] In specific implementation, to obtain a balanced three - phase no - load back - electromotive force, the phase angle difference between two adjacent coils in the phase should be 2kπ + 4π / 3 (k is a natural number). To implement this scheme, there is a shift angle for the design of the inner and outer rotors of the dual - rotor motor. For the relationship between the unit angle, the number of coils in the phase and the number of phase groups, there are the following relational expressions:

[0086]

[0087] At the same time, in order to satisfy three - phase, the number of stator slots on either side needs to satisfy: = 3 . In the case of , For the pole - slot combination of the dual - rotor flux - switching permanent - magnet motor, the mechanical angle can be obtained according to the electrical angle and the number of rotor poles , and the specific calculation formula is:

[0088]

[0089] Since the rotor pole pitch is equal to , then the number of rotor poles .

[0090] Then, according to the mechanical angle and the number of rotor poles the internal torque of the internal rotor is obtained .

[0091] According to the mechanical angle, the number of rotor poles and the phase difference, the external torque of the external rotor is obtained:

[0092]

[0093] where is the phase difference brought by the shift angle.

[0094] Step S30: Obtain the fundamental frequency of the motor according to the number of rotor poles and the rotational speed, and obtain the electrical period according to the fundamental frequency of the motor.

[0095] In a specific implementation, obtaining the fundamental frequency of the motor according to the number of rotor poles and the rotational speed, and obtaining the electrical period according to the fundamental frequency of the motor can be achieved through the relationship between the fundamental frequency of the motor and the number of rotor poles and the rotational speed . The relationship expression is:

[0096]

[0097] Furthermore, the fundamental frequency of the motor at this time is obtained, and the current electrical period is obtained based on the fundamental frequency of the motor. The electrical period is the reciprocal of the product of twice the fundamental frequency of the motor and the number of pole pairs.

[0098] Step S40: Perform Fourier analysis on the grid harmonics in the electrical periods of the internal torque and the external torque to obtain the harmonic suppression.

[0099] It should be noted that the harmonic suppression refers to that when adjusting the mechanical energy of the relative angle between the internal and external rotors, the harmonics with larger amplitudes in the torques received by the two rotors can be superimposed with opposite peaks and valleys, and the harmonics that have a greater impact on the rotors are obtained.

[0100] In a specific implementation, the harmonic components of the grid harmonics are determined. The greatest common divisor of the stator slot number and the rotor pole number is obtained according to the stator slot number and the rotor pole number. The order of the harmonic components is obtained according to the stator slot number and the greatest common divisor of the stator slot number and the rotor pole number. The cogging torque of the motor is obtained according to the harmonic components, the order of the harmonic components, the rotor pole number, and the mechanical angle. The harmonic suppression according to the grid harmonics is obtained according to the motor cogging torque. Fourier analysis is performed on the electrical cycles of the internal torque and the external torque, and the cogging torque of the FSPM motor is Fourier-expanded. The Fourier expansion formula is:

[0101]

[0102]

[0103] where, is the mth harmonic component, represents the stator slot number and the rotor pole number greatest common divisor, represents the rotor position angle, i.e., the mechanical angle, and k is a natural number. In the topology structure proposed by the present invention, a phase-group concentrated winding is adopted, and the stator core structure presents the characteristics of modular phase groups. Therefore, in the above formula, the stator slot number is corrected to the number of phase-group modules, i.e., 3 , and combined with the pole-slot matching formula, it is obtained:

[0104]

[0105] By adjusting the relative angle between the inner and outer rotors, the harmonics with larger amplitudes in the torques received by the two rotors can be superimposed with opposite peaks and valleys, realizing the maximum suppression of the cogging torque.

[0106] For , pole-slot matching dual-rotor motors, through the Fourier analysis of the cogging torques of the inner and outer rotors in the electrical cycle, it can be obtained that the cogging torques of the inner and outer rotors mainly have larger proportions of 2nd, 5th, 6th, and 7th harmonics. Referring to Figure 11 , Figure 11 is the cogging torque frequency spectrum diagram of the dual-rotor flux-switching motor.

[0107] Step S50: Analyze the harmonic suppression to obtain the target harmonic suppression.

[0108] It should be noted that the target harmonic suppression refers to the harmonic suppression that plays a dominant role among many harmonic suppressions. According to the frequency spectrum diagram in Figure 11 , it can be seen that the cogging torque of the outer rotor mainly has larger proportions of 2nd, 5th, 6th, and 7th harmonics, and among them, the 6th harmonic is the most prominent. Therefore, the target harmonic suppression in this embodiment is the 6th harmonic.

[0109] Step S60: Perform simulation analysis on the target harmonic to be suppressed to obtain an effective shift angle, and decouple the effective shift angle to obtain a target shift angle.

[0110] In specific implementation, when performing simulation analysis on the target harmonic to be suppressed, it can be obtained that the synthetic cogging torque varies with the shift angle of the dual rotors, with a large degree of fluctuation and certain periodicity, that is, it varies with a period of 180°. When not misaligned, the phase angles of the harmonics of the cogging torques of the inner and outer rotors are the same, in a completely positive superposition state, and the synthetic cogging torque is the maximum value. At 90°, the peak-to-peak value of the synthetic cogging torque reaches the minimum value, and there is also a value close to it at 270°, which is because the second and sixth harmonics with the largest amplitudes are superimposed in antiphase with the corresponding harmonics of the outer rotor and cancel each other out. When the misalignment angle is 30°, 150°, 270°, 360°, the sixth harmonics are all in a reverse superposition state, so the synthetic cogging torque is also small. From this, it can be concluded that when the shift angle is 30°, 90°, 150°, 270°, 360°, the harmonics can be effectively suppressed to reduce the influence of the cogging torque. However, all of these are based on the fact that the amplitudes of the harmonics of the cogging torques on both sides are equal and fixed with the change of the shift angle. In fact, due to the change of the shift angle, the magnetic circuit of the motor will change, thereby affecting the coupling degree of the inner and outer air-gap magnetic fields, resulting in changes in the air-gap flux density and the amplitude of the cogging torque. Then analyze the effective shift angle, determine the flux harmonic content corresponding to each effective shift angle, obtain the total harmonic distortion value of the no-load back electromotive force according to the effective shift angle and the flux harmonic content, and screen the total harmonic distortion value of the no-load back electromotive force to obtain the target shift angle.

[0111] When the shift angle is 0°, the type-I permanent magnet is evenly utilized by the two-side air gaps, showing that the adjacent two permanent magnets generate almost completely symmetric and identical magnetic flux circuits, which are jointly superimposed by the permanent magnets participating in the magnetic flux concentration effect. At this time, only 50% of the permanent magnet usage in the stator yoke region effectively acts on any one-side air gap.

[0112] When the shift angle is 180°, the magnetic flux passing through the inner air gap is a series-type magnetic flux. This series-type magnetic flux simultaneously links the inner and outer windings. In this case, the utilization rate of the permanent magnet is the highest, but this series-type magnetic flux passes through 4 air-gap reluctances, so the fundamental magnetic flux generated is not much larger than that at a misalignment angle of 90°. Even the magnetic force lines have a large magnetic leakage due to the excessive magnetic resistance on the path, resulting in an increase in the harmonic content of the magnetic chain.

[0113] When the shift angle is 90°, the part of the I-shaped permanent magnet in the stator yoke area will all act on the inner air gap, and at the same time, the outer part of the permanent magnet yoke area will also participate in providing the effective magnetic flux. According to the principle of minimum reluctance, to a certain extent, increasing the outer rotor tooth height can increase the reluctance of the leakage magnetic path passed by the outer part of the I-shaped permanent magnet, making more permanent magnets tend to act on the other air gap. It can be seen that the middle part of the permanent magnet plays a "time-sharing multiplexing" effect, that is, at the moment of the maximum magnetic chain of each side winding, it can provide effective magnetic flux, forming an alternating magnetic flux concentrating circuit to improve the motor torque density. Therefore, when the shift angle is 90°, the main magnetic flux increases by an effective magnetic flux compared with 0°, and the reluctance of the yoke permanent magnet also decreases, resulting in a significant increase in the synthetic main magnetic flux compared with no shift. In addition, for the relationship between the shift angle and the total harmonic distortion (THD) value of the no-load back electromotive force, it can be found that the THD value of the no-load back electromotive force is the smallest when the shift angle is 90° or 270°.

[0114] Therefore, in order to evaluate the disturbance effect of the armature magnetomotive force of the outer winding on the inner winding, the back electromotive force coupling rate can be calculated. Determine the no-load back electromotive force of the inner winding and the coupled induced back electromotive force of the inner winding according to the total harmonic distortion value of the no-load back electromotive force, obtain the back electromotive force coupling rate according to the no-load back electromotive force of the inner winding and the coupled induced back electromotive force of the inner winding, determine the unit magnetic density of the inner rotor within the electrical cycle according to the total harmonic distortion value of the no-load back electromotive force, obtain the armature magnetomotive force of the outer winding according to the unit magnetic density of the inner rotor to obtain the magnetic flux density distribution value of the inner rotor, and obtain the target shift angle according to the back electromotive force coupling rate and the magnetic flux density distribution value of the inner rotor. Among them, the back electromotive force coupling rate can be expressed as:

[0115]

[0116] Among them, is the no-load back electromotive force of the inner winding, is the coupled induced back electromotive force of the inner winding, and the maximum point of the average value of the magnetic flux density distribution of the inner rotor iron core part can be expressed as:

[0117] Among them, is the unit magnetic density of the inner rotor iron core within the electrical cycle, is used to evaluate the contribution of the armature magnetomotive force of the outer winding to the magnetic flux density of the inner rotor iron core. The smaller its value, the more the armature magnetomotive force acts on the outer part of the motor, and the higher the utilization rate of the armature magnetomotive force. Refer to Figure 12 , Figure 12It is a schematic diagram of the relationship between the internal and external coupling degree of a dual-rotor motor and the change of the shift angle. When the back electromotive force coupling rate is less than 180° at the shift angle, it decreases as the shift angle increases, and shows an upward trend after exceeding 180°. Therefore, when the shift angle is 180°, the armature magnetomotive force of the outer winding has the least interference on the inner winding, and when the misalignment angle is 90° or 270°, the coupling rates are only 1.94% and 1.99% respectively, which is a low coupling degree. Although the coupling rates at 90° and 270° of the shift angle are roughly the same, due to the influence of the complementary magnetic circuit of the flux-switching motor, the value at 270° and 180° is much larger than that at 90°. For the dual-rotor flux-switching permanent magnet motor, the best ideal effect can be achieved when the shift angle is set to 90° electrical angle, that is, it can not only meet the lowest cogging torque (reduce the 6th harmonic content), but also form an alternating magnetic flux concentrating circuit to avoid the mutual interference of the magnetic fluxes of the inner and outer rotors, maximize the fundamental back electromotive force again, and ensure a low coupling degree between the double three-phase windings.

[0118] Step S70: Optimize the dual-rotor flux-switching permanent magnet motor according to the target shift angle.

[0119] In a specific implementation, after obtaining the target shift angle, the shift angle of the dual-rotor flux-switching permanent magnet motor can be set to 90° to achieve the alternating aggregation of magnetic fluxes, reduce the cogging torque, increase the fundamental content of the back electromotive force at the same time, ensure the weak coupling of the double three-phase windings and the double air gaps, and achieve the purpose of optimizing the dual-rotor flux-switching permanent magnet motor.

[0120] In this embodiment, by determining the number of phase group modules of the dual-rotor flux-switching permanent magnet motor, obtaining the grid harmonics according to the number of phase group modules, determining the internal torque of the inner rotor and the external torque of the outer rotor, obtaining the fundamental frequency of the motor according to the number of rotor poles and the rotational speed, obtaining the electrical period according to the fundamental frequency of the motor, performing Fourier analysis on the grid harmonics in the electrical periods of the internal torque and the external torque, obtaining the harmonic suppression, analyzing the harmonic suppression to obtain the target harmonic suppression, performing simulation analysis on the target harmonic suppression to obtain the effective shift angle, and decoupling the effective shift angle to obtain the target shift angle, and optimizing the dual-rotor flux-switching permanent magnet motor according to the target shift angle, the combination of the internal and external motors is realized, the integration degree of the dual motors is improved, and the flux coupling rate of the dual motors can also be improved.

[0121] It should be understood that the above is only an example, and does not constitute any limitation to the technical solution of the present invention. In specific applications, those skilled in the art can set according to needs, and the present invention does not limit this.

[0122] It should be understood that although the steps in the flowcharts in the embodiments of the present application are displayed sequentially according to the indications of the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless there is a clear indication in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders. Moreover, at least a part of the steps in the figure may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0123] It should be noted that the above-described work process is only illustrative and does not limit the protection scope of the present invention. In actual applications, those skilled in the art can select some or all of them according to actual needs to achieve the purpose of the solution of this embodiment, and no limitation is imposed here.

[0124] In addition, it should be noted that in this article, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or system. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or system including that element.

[0125] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

[0126] Through the description of the above embodiments, those skilled in the art can clearly understand that the above embodiment methods can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, in essence, or the part that makes a contribution to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as a read-only memory (ROM) / RAM, magnetic disk, optical disk), and includes several instructions for causing a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0127] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A dual-rotor flux switching permanent magnet motor, characterized in that: The dual-rotor flux switching permanent magnet motor includes an inner rotor, an outer rotor and an intermediate stator, the intermediate stator includes an E-type stator core and an I-type permanent magnet, the E-type stator core is placed on both sides of the permanent magnet, the E-type stator core includes a plurality of teeth, an excitation winding is arranged between the adjacent teeth on the same side, the winding direction of the excitation winding is perpendicular to the permanent magnet, the electrical angle of the centerline arc width of the adjacent teeth is π, and the electrical angle of the centerline arc width between the permanent magnets is 2kπ+4 / 3π.

2. The dual-rotor flux switching permanent magnet motor according to claim 1, characterized in that: The inner rotor is fixedly connected to the inner rotor motor shaft through a mechanical tool, the outer rotor is fixedly connected to the outer rotor motor shaft through a mechanical tool, and the intermediate stator is fixedly connected to the motor housing through a stator assembly.

3. A dual-rotor flux switching permanent magnet motor optimization method, characterized in that: The dual-rotor flux switching method is applied to the dual-rotor flux switching permanent magnet motor according to any one of claims 1 to 2, and the dual-rotor flux switching motor optimization method includes: Determining the number of phase group modules of the dual-rotor flux switching permanent magnet motor, and obtaining grid harmonics according to the number of phase group modules; Determine the internal torque of the inner rotor and the external torque of the outer rotor; Obtaining the motor fundamental frequency according to the number of rotor poles and the rotation speed, and obtaining the electrical period according to the motor fundamental frequency; Performing Fourier analysis on the power grid harmonics during the electrical cycles of the internal torque and the external torque to obtain suppressed harmonics; Analyzing the suppressed harmonics to obtain target suppressed harmonics; Performing simulation analysis on the target harmonic suppression to obtain an effective shift angle, and decoupling the effective shift angle to obtain a target shift angle; The dual-rotor flux switching permanent magnet motor is optimized according to the target shift angle.

4. The method according to claim 3, characterized in that The determining of the internal torque of the inner rotor and the external torque of the outer rotor comprises: Determine the number of I-type permanent magnets and the number of phase groups; According to the electrical angle and the number of rotor poles to obtain the mechanical angle ; According to the mechanical angle and the number of rotor poles Obtaining the internal torque of the inner rotor; According to the mechanical angle, the number of rotor poles and the phase difference The external torque of the outer rotor is obtained.

5. The method according to claim 4, characterized in that Before obtaining the mechanical angle according to the electrical angle and the number of rotor poles, the method further includes: The number of rotor poles is obtained according to the number of the I-type permanent magnets and the number of phase groups.

6. The method according to claim 3, characterized in that The Fourier analysis of the power grid harmonics during the electrical cycles of the internal torque and the external torque to obtain suppressed harmonics includes: determining harmonic components of the power grid harmonics; Obtaining the greatest common divisor of the number of stator slots and the number of rotor poles according to the number of stator slots and the number of rotor poles; Obtaining the order of the harmonic component according to the number of stator slots and the greatest common divisor of the number of stator slots and the number of rotor poles; Obtaining the motor cogging torque according to the harmonic component, the order of the harmonic component, the number of rotor poles and the mechanical angle; Harmonics are suppressed based on the motor cogging torque.

7. The method according to claim 3, characterized in that Decoupling the effective displacement angle to obtain a target displacement angle includes: Analyzing the effective shift angles to determine the magnetic flux harmonic content corresponding to each of the effective shift angles; Obtaining a no-load back electromotive force total harmonic distortion value according to the effective shift angle and the magnetic flux harmonic content; The total harmonic distortion value of the no-load back electromotive force is screened to obtain a target shift angle.

8. The method according to claim 7, characterized in that The screening of the total harmonic distortion value of the no-load back electromotive force to obtain the target shift angle includes: Determine the inner winding no-load back electromotive force and the inner winding coupled induced back electromotive force according to the no-load back electromotive force total harmonic distortion value; Obtaining a back electromotive force coupling ratio according to the no-load back electromotive force of the inner winding and the coupled induced back electromotive force of the inner winding; Determine the magnetic flux density distribution value of the inner rotor according to the no-load back electromotive force total harmonic distortion value; A target shift angle is obtained according to the back electromotive coupling ratio and the magnetic flux density distribution value of the inner rotor.

9. The method according to claim 8, characterized in that Determining the magnetic flux density distribution value of the inner rotor according to the total harmonic distortion value of the no-load back electromotive force includes: Determining the unit magnetic flux density of the inner rotor within the electrical cycle according to the total harmonic distortion value of the no-load back electromotive force; The armature magnetomotive force of the outer winding is obtained according to the unit magnetic density of the inner rotor, and the magnetic flux density distribution value of the inner rotor is obtained.

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