A permanent magnet wind turbine with dual axial flux modulation

Abstract

The present invention belongs to the technical field of wind turbine generators, and in particular, relates to an axial flux double-modulation permanent magnet wind turbine generator, comprising a stator, a rotor and a wind wheel, wherein the stator is fixed in a motor housing, the stator is provided with large teeth and parallel slots, the parallel slots are embedded with stator windings, a plurality of split teeth are distributed on the large teeth, a stator permanent magnet is embedded on the surface of the stator, the rotor is rotatably connected in the motor housing, the rotor is coaxially arranged with the stator, an air gap is provided between the rotor and the stator, a rotor permanent magnet is embedded on the surface of the rotor, and a driven wheel is fixed on the rotor. The present invention has a flux modulation effect, suppresses the magnetic resistance and thrust fluctuation of the motor, improves the output performance of the motor, can effectively improve the utilization efficiency of wind energy, the rotor and the wind wheel are connected by a driving wheel and a driven wheel, avoids the rotor from being offset relative to the stator, and ensures the uniformity of the air gap width of the generator.

Description

Technical Field

[0001] The invention belongs to the technical field of wind generators, and in particular relates to an axial magnetic flux double-modulation permanent magnet wind generator. Background Art

[0002] A wind turbine is a device that converts wind energy into electrical energy. It is mainly composed of three parts: a wind rotor, a generator and a tower. When the wind blows the wind rotor blades, the blades will rotate. This rotation drives the rotor of the generator to rotate, and then drives the generator to generate electricity. Wind turbines can be divided into direct-drive wind turbines and doubly-fed wind turbines according to their transmission method. Direct-drive wind turbines do not require transmission devices such as gearboxes. The generator is directly connected to the wind rotor, which reduces the loss in the energy transfer process and therefore has a higher wind energy conversion efficiency.

[0003] Existing direct-drive wind turbines still have shortcomings. The wind wheel of a direct-drive wind turbine is directly connected to the rotor of the generator. The gravity of the wind wheel itself and the thrust applied to the wind wheel by the wind load will cause a relative offset between the rotor and the stator, resulting in an uneven air gap width of the generator, which ultimately affects the power generation of the generator. In addition, since the wind force changes all the time and is uncontrolled, the speed of the wind wheel is also constantly changing. When the speed of the wind wheel changes significantly, the wear at the connection between the wind wheel and the rotor will be aggravated, affecting the service life of the generator. Summary of the invention

[0004] The purpose of the present invention is to provide an axial flux double-modulation permanent magnet wind turbine generator in view of the problems raised in the above background technology.

[0005] To achieve the above object, the present invention adopts the following technical solution: an axial flux double-modulation permanent magnet wind turbine generator, comprising:

[0006] The stator is fixed in the motor housing, and is provided with large teeth and parallel slots, in which stator windings are embedded, and a plurality of split teeth are distributed on the large teeth. A stator permanent magnet is embedded on the surface of the stator, and the stator permanent magnet and the split teeth meet the following conditions:

[0007]

[0008] Where: P S represents the number of stator permanent magnets, kZ S Indicates the total number of split teeth;

[0009] The rotor is rotatably connected to the motor housing, the rotor is coaxially arranged with the stator, an air gap is arranged between the rotor and the stator, a rotor permanent magnet is embedded on the surface of the rotor, a driven wheel is fixed on the rotor, and the stator winding, large teeth, split teeth, stator permanent magnets and rotor permanent magnets meet the following conditions:

[0010]

[0011] Where: P represents the number of pole pairs of the stator winding, Z r kZ is the number of pole pairs of the rotor permanent magnet. S represents the total number of split teeth, P S Indicates the number of stator permanent magnets;

[0012] A wind wheel is fixed with a rotating shaft coaxially arranged with the wind wheel, and a driving wheel is fixed on the rotating shaft.

[0013] Furthermore, the stator permanent magnet and the rotor permanent magnet have the same magnetizing direction.

[0014] Furthermore, driven blades are fixed on the driven wheel disc, the driven blades are fan-shaped, and the driven blades are concentrically arranged with the driven wheel disc.

[0015] Furthermore, a driving blade is fixed on the driving wheel disc, the shape of the driving blade is the same as the shape of the driven blade, and the driving blade is concentrically arranged with the driving wheel disc.

[0016] Furthermore, a buffer assembly is provided between the driving blade and the driven blade, and the buffer assembly includes an arc-shaped slide groove opened on the driven blade, an arc-shaped slide rod adapted to the arc-shaped slide groove is fixed on the driving blade, a spring is sleeved on the arc-shaped slide rod, and two ends of the spring are respectively fixed on the driven blade and the driving blade.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] The present invention provides a driving wheel and a driven wheel. The driving wheel is connected to the wind wheel, and the driven wheel is connected to the rotor. The gravity of the wind wheel itself and the thrust applied to the wind wheel by the wind load will not affect the change of the rotor position, which effectively avoids the rotor from being offset relative to the stator and ensures the uniformity of the air gap width of the generator. A buffer spring is provided between the driving wheel and the driven wheel. When the rotation speed of the wind wheel changes, the rotation speed of the driven wheel changes slowly under the action of the buffer spring until it is consistent with the rotation speed of the driving wheel. The rotation speed of the driven wheel will not fluctuate violently, thereby reducing the wear of the rotor and extending the service life of the generator.

[0019] The number of stator permanent magnet pole pairs P in the present invention is S and the total number of split teeth kZ S Equal, that is

[0020] , stator side winding pole number P, large teeth number Z S , total number of split teeth kZ S , stator permanent magnet pole pair number PS and the number of rotor permanent magnet pole pairs (rotor teeth) Z r Between:

[0021] It is a "fundamental wave" axial flux double-modulation permanent magnet wind turbine generator with flux modulation effect, which suppresses the magnetic resistance and thrust fluctuation of the motor, improves the output performance of the motor, thereby effectively improving the wind energy utilization efficiency and enhancing the overload capacity of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of an axial magnetic flux double-modulation permanent magnet wind turbine provided by the present invention;

[0023] Figure 2 It is a schematic diagram of the stator structure of an axial magnetic flux double-modulation permanent magnet wind turbine provided by the present invention;

[0024] Figure 3 It is a schematic diagram of the rotor structure of an axial magnetic flux double-modulation permanent magnet wind generator provided by the present invention;

[0025] Figure 4 It is a schematic diagram of the matching structure of a driving wheel and a driven wheel of an axial magnetic flux double-modulation permanent magnet wind generator provided by the present invention;

[0026] Figure 5 This is a comparison chart of no-load induced electromotive force of three motors: PMVM, TH-DEMPMSM and FH-DEMPMSM;

[0027] Figure 6 An axial flux dual modulation permanent magnet wind turbine provided by the present invention has an air gap radial flux density waveform when it is unloaded and a corresponding Fourier harmonic analysis diagram;

[0028] Figure 7 A graph showing the variation of the average electromagnetic torque outputted by an axial flux dual-modulation permanent magnet wind generator provided by the present invention with the effective value of the phase current when an excitation current having the same phase as the induced electromotive force is supplied;

[0029] Figure 8 These are the same basic parameters of the three motors: PMVM, TH-DEMPMSM and FH-DEMPMSM.

[0030] In the figure, 1 is a stator, 11 is a large tooth, 12 is a parallel slot, 13 is a stator winding, 14 is a stator permanent magnet, and 111 is a split tooth;

[0031] 2 rotor, 21 rotor permanent magnet, 22 driven wheel disc, 221 driven blade, 222 arc chute;

[0032] 3 wind wheel, 31 rotating shaft, 32 driving wheel disc, 321 driving blade, 322 arc-shaped sliding rod, 323 spring. DETAILED DESCRIPTION

[0033] The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0034] like Figure 1-Figure 4 As shown, an axial flux double modulation permanent magnet wind turbine generator includes a stator 1, a rotor 2 and a wind wheel 3. The stator 1 is fixed in a motor housing. The motor housing adopts the existing technology and is not described here. The stator 1 is provided with large teeth 11 and parallel slots 12. The number of large teeth 11 and parallel slots 12 is Z. S , a stator winding 13 is embedded in the parallel slot 12, the number of pole pairs of the stator winding 13 is P, k split teeth 111 are distributed on the large tooth 11, and the total number of the split teeth 111 is kZ S , stator permanent magnets 14 are embedded on the surface of stator 1, and the number of stator permanent magnets 14 is P S , the number P of stator permanent magnets 14 S The total number kZ of the split teeth 111 S Equal, that is ;

[0035] The rotor 2 is rotatably connected to the motor housing. The rotor 2 is coaxially arranged with the stator 1. An air gap is arranged between the rotor 2 and the stator 1. The surface of the rotor 2 is embedded with rotor permanent magnets 21. The number of the rotor permanent magnets 21 is Z. r , the magnetization direction of the stator permanent magnet 14 and the rotor permanent magnet 21 is the same, the number of pole pairs of the stator winding 13 P, the total number of large teeth 11 Z S 、Split teeth 111 number kZ S 、Stator permanent magnet 14 pole pairs P S and the number of rotor permanent magnet pole pairs (rotor teeth) Z r Between: A driven wheel disc 22 is fixed on the rotor 2 , and a driven blade 221 is fixed on the driven wheel disc 22 . The driven blade 221 is fan-shaped, and the driven blade 221 is concentrically arranged with the driven wheel disc 22 .

[0036] The magnetic field double modulation permanent magnet motor is divided into two types according to whether the number of stator split teeth and the number of stator permanent magnet pole pairs are equal. When the number of split teeth is not equal to the number of stator permanent magnet pole pairs, it can be called a "tooth harmonic" magnetic field double modulation permanent magnet motor, otherwise it can be called a "fundamental wave" magnetic field double modulation permanent magnet motor. In this application, the number of stator permanent magnets 14 P S The total number kZ of the split teeth 111 S Equal, that is The motor can be called a "fundamental wave" axial flux double modulation permanent magnet wind turbine generator, which generates a rotating torque through the interaction of the magnetic fields of the stator permanent magnets 14 and the rotor permanent magnets 21, and plays a role in flux modulation.S The total number kZ of the split teeth 111 S Equality can ensure that each stator permanent magnet 14 corresponds to a split tooth 111, thereby optimizing the distribution of the magnetic field, reducing the leakage and interference of the magnetic field, thereby reducing the magnetic resistance caused by the uneven magnetic field and reducing the thrust fluctuation caused by the change of the magnetic field, improving the output performance of the motor, and effectively improving the efficiency of wind energy utilization.

[0037] The generator is simulated based on the three-dimensional finite element analysis method. In the study, the no-load induced electromotive force of three motors, namely the split-tooth permanent magnet vernier motor (PMVM), the "tooth harmonic" magnetic field double modulation permanent magnet motor (TH-DEMPMSM) and the "fundamental wave" magnetic field double modulation permanent magnet motor (FH-DEMPMSM), is compared (the results are shown in Figure 2). Figure 5 As shown in the figure), the basic parameters of the three motors are as follows Figure 8 As shown in the figure, the number of stator permanent magnets of the three are 0, 9, and 18 respectively, and the number of pole pairs of rotor permanent magnets is the same as the number of rotor teeth, which is 16. The rotor structure of the two magnetic field dual modulation permanent magnet motors is the same as that of the split tooth permanent magnet vernier motor. Both use 16 permanent magnets with the same magnetizing direction embedded on the rotor side. The stator uses 9 slots and the 9 teeth all use split tooth structure. The polarity of all permanent magnets on the stator and rotor of the two magnetic field dual modulation permanent magnet motors is the same. The comparison results show that the amplitudes of the no-load induced electromotive force of PMVM, TH-DEMPMSM and FH-DEMPMSM are approximately 171V, 220V and 249V respectively, and the induced electromotive force of the "fundamental wave" magnetic field dual modulation permanent magnet motor (FH-DEMPMSM) is the largest.

[0038] The radial magnetic flux density waveform of the air gap when FH-DEMPMSM is running without load and the corresponding Fourier harmonic analysis results (such as Figure 6 As shown in the figure, the air gap flux density contains rich spatial harmonic content. In addition to the 16-pole and 18-pole fundamental components, the 2-pole components in the low-order harmonic content have the largest amplitude and are used as effective harmonics.

[0039] When the stator winding is fed with an excitation current of the same phase as the induced electromotive force, the average electromagnetic torque output by FH-DEMPMSM changes with the effective value of the phase current (e.g. Figure 7 As shown in the figure, theoretical value: theoretical value, simulation value: Simulation value), it can be seen that when the current flowing through the stator winding is less than 1.5 times the rated value, the electromagnetic torque output by the motor increases almost linearly with the current. When the current is too large, the saturation of the motor core increases, and the increase in the electromagnetic torque decreases, which has a certain deviation from the theoretical value. The difference is not large below 2.5 times the rated current, indicating that the motor has a strong overload capacity.

[0040] A rotating shaft 31 coaxially arranged with the wind wheel 3 is fixed on the wind wheel 3, a driving wheel 32 is fixed on the rotating shaft 31, a driving blade 321 is fixed on the driving wheel 32, the shape of the driving blade 321 is the same as that of the driven blade 221, and the driving blade 321 is concentrically arranged with the driving wheel 32.

[0041] During operation, the wind force drives the wind wheel 3 to rotate, and the rotation of the wind wheel 3 drives the rotating shaft 31 and the driving wheel disc 32 to rotate, thereby driving the driving blades 321 to rotate, and the rotation of the driving blades 321 drives the driven blades 221 to rotate, thereby driving the driven wheel disc 22 to rotate, and the rotation of the driven wheel disc 22 drives the rotor 2 to rotate, so that the generator starts to generate electricity. The wind wheel 3 is not directly connected to the rotor 2, and the gravity of the wind wheel 3 itself and the thrust applied to the wind wheel 3 by the wind load will not affect the position change of the rotor 2. This effectively avoids the displacement of the rotor 2 relative to the stator 1, ensures the uniformity of the air gap width of the generator, and thus ensures the normal operation of the generator.

[0042] A buffer assembly is provided between the driving blade 321 and the driven blade 221, and the buffer assembly includes an arc-shaped slide groove 222 opened on the driven blade 221, and an arc-shaped slide rod 322 adapted to the arc-shaped slide groove 222 is fixed on the driving blade 321, and a spring 323 is sleeved on the arc-shaped slide rod 322, and the two ends of the spring 323 are respectively fixed on the driven blade 221 and the driving blade 321.

[0043] When the rotation speed of the wind wheel 3 changes, the buffer component can play a buffering role. When the rotation speed of the wind wheel 3 increases, the rotation speed of the driving blade 321 increases synchronously and at this time the rotation speed of the driving blade 321 is greater than the rotation speed of the driven blade 221. The driving blade 321 will squeeze the spring 323 and apply thrust to the driven blade 221 through the spring 323 to gradually increase the rotation speed of the driven blade 221. As the rotation speed of the driven blade 221 gradually increases until it is the same as the rotation speed of the driving blade 321, the spring 323 gradually returns to its natural state. On the contrary, when the rotation speed of the wind wheel 3 decreases, the rotation speed of the wind wheel 3 decreases synchronously, and the rotation speed of the driving blade 321 also decreases accordingly. At this time, the rotation speed of the driving blade 321 is lower than the rotation speed of the driven blade 221. The driving blade 321 generates a pulling force on the spring 323 to stretch the spring 323, and the spring 323 pulls the driven blade 221 to reduce the rotation speed of the driven blade 221 until the rotation speed of the driven blade 221 is the same as the rotation speed of the driving blade 321, and as the rotation speed of the driven blade 221 decreases, the spring 323 gradually returns to its natural state, thereby achieving that when the rotation speed of the wind wheel 3 increases or decreases, the rotation speed of the driven wheel disc 22 gradually increases or decreases, and the rotation speed of the driven wheel disc 22 will not fluctuate violently, thereby reducing the wear of the rotor 2 and extending the service life of the generator.

[0044] The working principle of the present invention is as follows:

[0045] When the wind turbine generator of the present invention is working, the wind wheel 3 is driven to rotate by the wind force, and the rotation of the wind wheel 3 drives the rotating shaft 31 and the driving wheel disc 32 to rotate. When the driving wheel disc 32 rotates, the spring 323 is squeezed by the driving blade 321 and the driven blade 221 is pushed to rotate by the spring 323. When the rotation speed of the driven blade 221 is the same as the rotation speed of the driving blade 321, the spring 323 returns to the natural state, and the driven blade 221 drives the driven wheel disc 22 and the rotor 2 to rotate while rotating, so that the generator starts to generate electricity. The driving wheel disc 32 and the driven wheel disc 22 are provided. The driving wheel disc 32 is connected to the wind wheel 3 through the rotating shaft 31, and the driven wheel disc 22 is connected to the rotor 2. The gravity of the wind wheel 3 itself and the thrust applied to the wind wheel 3 by the wind load will not affect the position change of the rotor 2, which effectively avoids the displacement of the rotor 2 relative to the stator 1, ensures the uniformity of the air gap width of the generator, and thus ensures the normal operation of the generator;

[0046] A buffer spring 323 is provided between the driving wheel disc 32 and the driven wheel disc 22. When the speed of the wind wheel 3 increases, the speed of the driving blade 321 increases synchronously and at this time the speed of the driving blade 321 is greater than the speed of the driven blade 221. The driving blade 321 will squeeze the spring 323 and apply a thrust to the driven blade 221 through the spring 323 to gradually increase the speed of the driven blade 221. As the speed of the driven blade 221 gradually increases until it is the same as the speed of the driving blade 321, the spring 323 gradually returns to a natural state. On the contrary, when the speed of the wind wheel 3 decreases, the speed of the wind wheel 3 decreases synchronously, and the speed of the driving blade 321 also decreases accordingly. At this time, the rotation speed of the driving blade 321 is lower than the rotation speed of the driven blade 221, and the driving blade 321 generates a pulling force on the spring 323 to stretch the spring 323, and the spring 323 pulls the driven blade 221 to reduce the rotation speed of the driven blade 221 until the rotation speed of the driven blade 221 is the same as the rotation speed of the driving blade 321, and as the rotation speed of the driven blade 221 decreases, the spring 323 gradually returns to a natural state, and when the rotation speed of the wind wheel 3 increases or decreases, the rotation speed of the driven wheel disc 22 gradually increases or decreases, and the rotation speed of the driven wheel disc 22 does not fluctuate violently, thereby reducing the wear of the rotor 2 and extending the service life of the generator;

[0047] The magnetic field double modulation permanent magnet motor is divided into two types according to whether the number of stator split teeth and the number of stator permanent magnet pole pairs are equal. When the number of split teeth is not equal to the number of stator permanent magnet pole pairs, it can be called a "tooth harmonic" magnetic field double modulation permanent magnet motor, otherwise it can be called a "fundamental wave" magnetic field double modulation permanent magnet motor. In this application, the number of stator permanent magnets 14 P S The total number kZ of the split teeth 111 S Equal, that is The motor can be called a "fundamental wave" axial flux double modulation permanent magnet wind turbine generator, which generates a rotating torque through the interaction of the magnetic fields of the stator permanent magnets 14 and the rotor permanent magnets 21, and plays a role in flux modulation. S The total number kZ of the split teeth 111 S Equal, it can ensure that each stator permanent magnet 14 corresponds to a split tooth 111, thereby optimizing the distribution of the magnetic field, reducing the leakage and interference of the magnetic field, thereby reducing the magnetic resistance caused by the uneven magnetic field and reducing the thrust fluctuation caused by the change of the magnetic field, improving the output performance of the motor, and effectively improving the utilization efficiency of wind energy;

[0048] The generator is simulated based on the three-dimensional finite element analysis method. In the study, the no-load induced electromotive force of three motors, namely the split-tooth permanent magnet vernier motor (PMVM), the "tooth harmonic" magnetic field double modulation permanent magnet motor (TH-DEMPMSM) and the "fundamental wave" magnetic field double modulation permanent magnet motor (FH-DEMPMSM), is compared (the results are shown in Figure 2). Figure 5 As shown in the figure), the basic parameters of the three motors are as follows Figure 8 As shown in the figure, the number of permanent magnets on the stator side of the three are 0, 9, and 18 respectively, the number of pole pairs of the rotor permanent magnet is the same as the number of rotor teeth and is 16. The rotor structure of the two magnetic field dual modulation permanent magnet motors is the same as that of the split tooth permanent magnet vernier motor. Both use 16 permanent magnets with the same magnetizing direction embedded on the rotor side. The stator uses 9 slots and the 9 teeth all use split tooth structure. The polarity of all permanent magnets on the stator and rotor of the two magnetic field dual modulation permanent magnet motors is the same. The comparison results show that the amplitudes of the no-load induced electromotive force of PMVM, TH-DEMPMSM and FH-DEMPMSM are approximately 171V, 220V and 249V respectively, and the induced electromotive force of the "fundamental wave" magnetic field dual modulation permanent magnet motor (FH-DEMPMSM) is the largest.

[0049] The radial magnetic flux density waveform of the air gap when FH-DEMPMSM is running without load and the corresponding Fourier harmonic analysis results (such as Figure 6 As shown in the figure, the air gap flux density contains rich spatial harmonic content. In addition to the 16-pole and 18-pole fundamental components, the 2-pole components in the low-order harmonic content have the largest amplitude and are used as effective harmonics.

[0050] When the stator winding is fed with an excitation current of the same phase as the induced electromotive force, the average electromagnetic torque output by FH-DEMPMSM changes with the effective value of the phase current (e.g. Figure 7As shown in the figure, theoretical value: theoretical value, simulation value: Simulation value), it can be seen that when the current passed through the stator winding is less than 1.5 times the rated value, the electromagnetic torque output by the motor increases almost linearly with the current. When the current is too large, the saturation degree of the motor core increases accordingly, and the increase in the electromagnetic torque decreases, which has a certain deviation from the theoretical value. The difference is not large below 2.5 times the rated current, indicating that the motor has a strong overload capacity.

[0051] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An axial flux dual-modulation permanent magnet wind turbine, characterized in that: include: A stator (1), the stator (1) being fixed in a motor housing, the stator (1) being provided with large teeth (11) and parallel slots (12), the parallel slots (12) being embedded with stator windings (13), the large teeth (11) being distributed with a plurality of split teeth (111), the surface of the stator (1) being embedded with stator permanent magnets (14), the stator permanent magnets (14) and the split teeth (111) satisfying the following conditions: Where: P S represents the number of stator permanent magnets (14), kZ S represents the total number of split teeth (111); A rotor (2), the rotor (2) being rotatably connected to a motor housing, the rotor (2) being coaxially arranged with a stator (1), an air gap being provided between the rotor (2) and the stator (1), a rotor permanent magnet (21) being embedded on the surface of the rotor (2), a driven wheel disc (22) being fixed to the rotor (2), a driven blade (221) being fixed to the driven wheel disc (22), the driven blade (221) being fan-shaped, the driven blade (221) being concentrically arranged with the driven wheel disc (22), and the stator winding (13), the large teeth (11), the split teeth (111), the stator permanent magnet (14) and the rotor permanent magnet (21) satisfying the following conditions: , where P represents the number of pole pairs of the stator winding (13), Z r represents the number of pole pairs of the rotor permanent magnet (21), kZ S represents the total number of split teeth (111), P S represents the number of stator permanent magnets (14); A wind wheel (3), wherein a rotating shaft (31) coaxially arranged with the wind wheel (3) is fixed on the wind wheel (3), a driving wheel disc (32) is fixed on the rotating shaft (31), a driving blade (321) is fixed on the driving wheel disc (32), the driving blade (321) has the same shape as a driven blade (221), the driving blade (321) and the driving wheel disc (32) are coaxially arranged, a buffer component is provided between the driving blade (321) and the driven blade (221), the buffer component comprises an arc-shaped slide groove (222) provided on the driven blade (221), an arc-shaped slide rod (322) adapted to the arc-shaped slide groove (222) is fixed on the driving blade (321), a spring (323) is sleeved on the arc-shaped slide rod (322), and two ends of the spring (323) are respectively fixed on the driven blade (221) and the driving blade (321).

2. The axial flux dual modulation permanent magnet wind turbine according to claim 1, characterized in that: The stator permanent magnet (14) and the rotor permanent magnet (21) have the same magnetizing direction.

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