Speed-increasing type semi-direct-drive wind driven generator and control method thereof

Abstract

The invention relates to a speed-increasing type semi-direct-driven wind driven generator and a control method thereof, and belongs to the field of wind power. The speed-increasing type semi-direct-driven wind driven generator comprises a stator, an outer rotor and an inner rotor, the outer rotor comprises outer rotor iron blocks and permanent magnets and adopts a spoke type structure; the stator and the inner rotor form a synchronous motor; the outer rotor, the stator teeth and the inner rotor form a magnetic gear box; an inner rotor permanent magnet adopts an NE Halbach array; three blocks form a pair of poles; and the three blocks are respectively composed of permanent magnet blocks with magnetization angles of 135 degrees and-90 degrees, permanent magnet blocks with magnetization angles of-45 degrees and 45 degrees, and permanent magnet blocks with magnetization angles of 90 degrees and 135 degrees. When the wind speed is lower than the cut-in wind speed, working in a motor mode; and when the wind speed is greater than the cut-in wind speed, working in a generator mode. The invention integrates the functions of the gearbox and the motor, has the advantages of small volume, high efficiency, low cost and the like, can generate power at normal wind speed, and can assist in starting the wind wheel to rotate when the wind speed is lower than the cut-in wind speed, thereby realizing low-wind-speed power generation.

Description

Technical Field

[0001] The present invention relates to a wind turbine generator and a control method thereof, in particular to a speed-increasing semi-direct-drive wind turbine generator and a control method thereof, belonging to the technical field of wind power generation. Background Art

[0002] Semi-direct drive wind turbines have the advantages of both permanent magnet direct drive and doubly fed wind turbines and have become one of the mainstream models. At present, semi-direct drive wind turbines all use mechanical gearboxes to increase the speed, that is, they use a generator + mechanical gearbox structure. The mechanical gearbox uses mechanical gear meshing and requires a complex oil injection and lubrication system, resulting in large size, high mechanical wear, and high failure rate in the existing structure. Once a failure occurs, the maintenance cost is high and the downtime is long, resulting in huge economic losses.

[0003] As a new transmission mode, magnetic gears have the advantages of no wear, maintenance-free, noise-free, no lubrication, and overload protection due to no mechanical contact. In recent years, they have been paid more and more attention and applied. Magnetic gearboxes have the characteristics of physical isolation, no lubrication, small size, light weight, low energy consumption, and large transmission torque, which can greatly reduce the operation and maintenance costs of large wind turbines, especially semi-direct drive and doubly fed wind turbines, and improve system operation performance and reliability.

[0004] The permanent magnets of traditional permanent magnet motors are usually magnetized radially. Although the structure is simple and easy to implement, it has limitations in torque pulsation and cogging torque, which affects the stability and efficiency of the motor. The Halbach array can improve the magnetic field strength and reduce torque pulsation and cogging torque through a unique magnetic field distribution design, thereby optimizing the motor performance; but due to the single arrangement of the magnetization array, the magnetic field modulation efficiency is limited.

[0005] Therefore, there is an urgent need to develop a small-sized, high-efficiency, low-cost speed-increasing semi-direct-drive wind turbine that integrates a speed-increasing magnetic gearbox and a generator.

[0006] The present invention proposes a new type of efficient permanent magnet Halbach magnetization array (hereinafter referred to as NE Halbach), and based on this array, constructs a speed-increasing semi-direct drive wind turbine generator integrating a speed-increasing magnetic gearbox and a generator. The proposed NE Halbach magnetization array method breaks the traditional Halbach magnetization arrangement method of rotating the same angle in sequence. By adjusting the magnetization array angle, the goals of low energy consumption, high efficiency, low torque pulsation and low cogging torque can be achieved. Summary of the invention

[0007] The main purpose of the present invention is to: in view of the shortcomings and gaps in the prior art, the present invention provides a speed-increasing semi-direct-drive wind turbine and a control method thereof, which integrates the functions of a speed-increasing magnetic gearbox, a generator and a motor by combining magnetic field modulation and a new NE Halbach magnetizing array, and has the advantages of small size, high efficiency and low cost. It can not only efficiently convert wind energy into electrical energy under normal wind speed conditions, but also act as a motor when the wind speed is lower than the cut-in wind speed to assist in starting the wind wheel rotation, reduce the starting resistance torque, and realize low wind speed power generation.

[0008] In order to achieve the above objectives, the speed-increasing semi-direct-drive wind turbine generator of the present invention comprises: a stator, an outer rotor, an inner rotor, a rotating shaft, etc.; one end of the rotating shaft is fixed to the outer rotor, and the other end is connected to the wind wheel main shaft; the stator is connected to the machine-side converter.

[0009] The stator, the outer rotor and the inner rotor form a two-layer air gap radial structure, wherein the stator is on the outside, the outer rotor is in the middle, and the inner rotor is on the inside;

[0010] The outer rotor includes an outer rotor iron block and an outer rotor permanent magnet, which adopts a spoke structure. The outer rotor permanent magnet is pasted to the outer rotor iron block at intervals. The inner rotor includes an inner rotor iron core and an inner rotor permanent magnet. The inner rotor permanent magnet is pasted to the outside of the inner rotor iron core. The outer rotor iron block adopts an I-shaped structure to facilitate better fixation with the outer rotor permanent magnet.

[0011] The inner rotor permanent magnet adopts a NE Halbach array, and the NE Halbach array is composed of three blocks to form a pair of poles. The first block consists of a permanent magnet block with a magnetization angle of -135° and a magnetization angle of -90°, the second block consists of a permanent magnet block with a magnetization angle of -45° and a magnetization angle of 45°, and the third block consists of a permanent magnet block with a magnetization angle of 90° and a magnetization angle of 135°.

[0012] The stator includes a stator winding and a stator core. The stator teeth are straight teeth used for magnetic field modulation, similar to the magnetic modulation ring of a magnetic gear. The number of the stator teeth is equal to the sum of the number of pole pairs of the inner rotor and the number of pole pairs of the outer rotor.

[0013] The stator and the inner rotor form a synchronous motor; the outer rotor, stator teeth and inner rotor form a magnetic gearbox, and its speed ratio is the ratio of the number of pole pairs of the outer rotor to the number of pole pairs of the inner rotor.

[0014] The present invention provides a control method for a speed-increasing semi-direct-drive wind turbine generator, comprising the following steps:

[0015] Step 1: When the wind speed is lower than the cut-in wind speed, the speed-increasing semi-direct-drive wind turbine generator is operated in the motor + deceleration mode: the machine-side converter is in the inverter state, and the stator winding is energized. At this time, the stator and the inner rotor constitute a motor, and the inner rotor is rotated; the inner rotor, the outer rotor, and the stator teeth constitute a magnetic gearbox, and the inner rotor will drive the outer rotor to rotate, thereby driving the wind wheel main shaft to rotate; at this time, the magnetic gearbox is a reduction gearbox;

[0016] Step 2, when the wind speed is greater than the cut-in wind speed and the wind rotor speed reaches the grid-connected speed, the speed-increasing semi-direct-drive wind generator is operated in the speed-increasing + generator mode: the machine-side converter is in a rectifying state, and the speed-increasing semi-direct-drive wind generator is controlled to operate; at this time, the wind rotor main shaft drives the outer rotor to rotate, and the outer rotor and the stator teeth and the inner rotor form a magnetic gearbox, then the outer rotor drives the inner rotor to rotate, and the stator and the inner rotor form a generator, then the stator winding outputs current, and the speed-increasing semi-direct-drive wind generator starts to generate electricity; at this time, the magnetic gearbox is a speed-increasing gearbox.

[0017] The beneficial effects of the present invention are:

[0018] 1) The permanent magnet NE Halbach array proposed in the present invention can significantly improve the electromagnetic performance of the motor and the sinusoidal nature of the air gap flux by optimizing the arrangement of the permanent magnets, thereby improving the generator efficiency and reducing the torque pulsation.

[0019] 2) The speed-increasing wind turbine generator of the present invention integrates a speed-increasing magnetic gearbox and a generator, has a compact structure, and has the advantages of small size, high efficiency, low cost, light weight, low energy consumption, and high reliability.

[0020] 3) Because the magnetic gearbox has no mechanical engagement and is a non-contact transmission, mechanical isolation is achieved, and the mechanical vibration of the wind wheel will not be transmitted to the generator, which can effectively solve the resonance and noise problems inherent in mechanical wind power gearboxes; in addition, except for the bearings, no lubrication is required, eliminating the complex and bulky oil injection lubrication and cooling system, which can greatly reduce the operation and maintenance costs of wind turbines.

[0021] 4) It can not only efficiently convert wind energy into electrical energy under normal wind speed conditions, but also be used as a motor when the wind speed is lower than the cut-in wind speed to assist in starting the wind wheel, reduce the starting resistance torque, and achieve low wind speed power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The topological structure and power generation system schematic diagram of the speed-increasing semi-direct-drive wind turbine generator of the present invention are shown in FIG.

[0023] Figure 2 It is a cross-sectional view and a schematic diagram of the three-dimensional topological structure of the stator and rotor of the speed-increasing semi-direct-drive wind turbine of the present invention.

[0024] Figure 3 It is a schematic diagram of the I-shaped iron core structure of the outer rotor of the present invention.

[0025] Figure 4 It is a schematic diagram of the NE Halbach array of the inner rotor permanent magnet of the speed-increasing semi-direct-drive wind turbine of the present invention.

[0026] Figure 5 It is a schematic diagram of energy transmission of the speed-increasing semi-direct-drive wind turbine in the motor mode of the present invention.

[0027] Figure 6 It is a schematic diagram of energy transmission of the speed-increasing semi-direct-drive wind turbine in the generator mode of the present invention.

[0028] Figure 7 Schematic diagram of the traditional 30°, 45°, and 60° Halbach array.

[0029] Figure 8 The figure is a comparison diagram of the magnetic flux density and harmonic wave at the inner rotor core and the stator core when using the traditional Halbach array and the NE Halbach array of the present invention.

[0030] Fig. 9 This is a torque comparison diagram under different Halbach arrays.

[0031] Fig.10 The figure is a comparison of torque ripple under different Halbach arrays.

[0032] Among them, 1-stator; 2-outer rotor; 3-inner rotor; 4-rotating shaft; 5-housing; 6-wind wheel main shaft; 7-wind wheel; 8-machine-side converter; 11-stator core; 12-stator winding; 21-outer rotor iron block; 22-outer rotor permanent magnet; 31-inner rotor core; 32-inner rotor permanent magnet. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0034] like Figure 1 As shown, the speed-increasing semi-direct-drive wind turbine of the present invention comprises: a stator 1, an outer rotor 2, an inner rotor 3, a rotating shaft 4, a casing 5, etc.; one end of the rotating shaft 4 is fixed to the outer rotor 2, and the other end is connected to the wind wheel main shaft 6; the stator winding 11 of the stator 1 is connected to the machine-side converter 8 (MSC).

[0035] The stator 1, the outer rotor 2, and the inner rotor 3 form a two-layer air gap radial structure, wherein the stator 1 is on the outside, the outer rotor 2 is in the middle, and the inner rotor 3 is on the inside;

[0036] like Figure 2As shown, the outer rotor 2 includes an outer rotor iron block 21 and an outer rotor permanent magnet 22, which adopts a spoke structure, and the outer rotor permanent magnet 22 is pasted to the outer rotor iron block 21 at intervals; the inner rotor 3 includes an inner rotor core 31 and an inner rotor permanent magnet 32, and the inner rotor permanent magnet 32 ​​is pasted to the outer side of the inner rotor core 31; Figure 3 As shown, the outer rotor iron block 21 adopts an I-shaped structure so as to be better fixed to the outer rotor permanent magnet 22 .

[0037] Furthermore, if Figure 4 As shown, the inner rotor permanent magnet 31 adopts a new and efficient NE Halbach array. The NE Halbach array is composed of three blocks to form a pair of poles. The first block consists of a permanent magnet block with a magnetizing angle of -135° and a magnetizing angle of -90°, the second block consists of a permanent magnet block with a magnetizing angle of -45° and a magnetizing angle of 45°, and the third block consists of a permanent magnet block with a magnetizing angle of 90° and a magnetizing angle of 135°.

[0038] The stator 1 includes a stator winding 12 and a stator core 11; wherein the stator winding 12 is a three-phase AC winding; the stator teeth are straight teeth, which are used for magnetic field modulation, similar to the magnetic modulation ring of a magnetic gear, so the stator teeth are also called modulation teeth; the number of stator teeth N is s Equal to the number of outer rotor pole pairs p out The number of inner rotor pole pairs p in The sum of N s =p out +p in .

[0039] The stator 1 and the inner rotor 3 form a synchronous motor, and the number of pole pairs of the stator winding 12 is equal to the number of pole pairs of the inner rotor.

[0040] The outer rotor 2, stator teeth, and inner rotor 3 form a magnetic gearbox, whose speed ratio G is the number of pole pairs of the outer rotor p out The number of pole pairs of the inner rotor p in The ratio of G = p out / p in .

[0041] The control method of the above-mentioned speed-increasing semi-direct-drive wind turbine generator comprises the following steps:

[0042] Step 1: When the wind speed is lower than the cut-in wind speed, the speed-increasing semi-direct-drive wind turbine generator is operated in the motor + deceleration mode: the machine-side converter 8 is in the inverter state, and the stator winding 12 is energized. At this time, the stator 1 and the inner rotor 3 form a motor, and the inner rotor 3 rotates; the inner rotor 3 is decelerated by the magnetic gearbox composed of the inner rotor 3, the stator teeth, and the outer rotor 2, driving the outer rotor 2 to rotate, thereby driving the wind wheel main shaft 7 to rotate; at this time, the magnetic gearbox is a deceleration gearbox, and its reduction ratio is G d =pin / p out .

[0043] Figure 5 The energy transfer diagram for this mode is shown below. When the stator winding 12 is energized, its power is output from its port, and the magnetic field generated is coupled with the magnetic field of the inner and outer rotors. Part of the power is transmitted to the outer rotor 2; part of the power is transmitted to the inner rotor 3 and induces a magnetic torque, which is also transmitted to the outer rotor 2 after the magnetic field of the inner and outer rotors is coupled. The outer rotor 2 drives the wind rotor main shaft 6 to rotate through the rotating shaft 4, and the wind rotor main shaft 6 drives the wind rotor 7 to rotate; at the same time, the mechanical torque generated by the breeze also drives the wind rotor 7 to rotate. At this time, the power P output by the outer rotor 2 to the wind rotor 7 is o is the electromagnetic power P transmitted from the stator winding 12 to the outer rotor wo The magnetic power P output by the inner rotor 3 to the outer rotor 2 io The sum of , that is:

[0044] P o =P wo +P io (1)

[0045] Step 2, when the wind speed is greater than the cut-in wind speed and the wind rotor speed reaches the grid-connected speed, the speed-increasing semi-direct-drive wind turbine generator is operated in the speed-increasing + generator mode: the machine-side converter 8 is in a rectifying state, and the speed-increasing semi-direct-drive wind turbine generator is controlled to operate; at this time, the wind rotor main shaft 6 drives the outer rotor 2 to rotate, and the outer rotor 2 is accelerated by the magnetic gearbox composed of the outer rotor 2, the stator teeth, and the inner rotor 3, and drives the inner rotor 3 to rotate, and the stator 1 and the inner rotor 3 form a generator, then the stator winding 12 outputs current, and the speed-increasing semi-direct-drive wind turbine generator starts to generate electricity; at this time, the magnetic gearbox is a speed-increasing gearbox, and its speed-increasing ratio is G i =p out / p in .

[0046] After the wind wheel 7 rotates, it obtains a certain amount of kinetic energy and reaches a certain speed. According to Newton's second law, the wind wheel speed continues to increase. Because the acceleration is small, the required wind force can be small. Even a light breeze can maintain the rotation of the wind wheel, thereby achieving low wind speed power generation. The motion equation at this time is:

[0047]

[0048] Where, T W The wind wheel torque provided by the wind wheel 7, T e is the electromagnetic torque generated by the stator winding 12, J is the moment of inertia, and ω is the angular velocity of the wind wheel 7.

[0049] Figure 6The energy transfer diagram for this mode is shown below. The mechanical power generated by the wind wheel 7 flows into the outer rotor 2, part of which causes the stator winding 12 to induce electromagnetic torque; part of which is coupled through the magnetic fields of the inner and outer rotors, generating magnetic torque on the inner rotor 3, and then inducing electromagnetic torque on the stator winding 12. The stator winding 12 outputs power P w , which is equal to the electromagnetic power P induced by the outer rotor on the stator winding 12 ow The electromagnetic power P induced by the inner rotor 3 on the stator winding 12 iw The sum of , that is:

[0050] P w =P ow +P iw (3)

[0051] The speed-increasing semi-direct-drive wind turbine generator of the present invention is further described below using a preferred embodiment.

[0052] Take a 5kW speed-increasing semi-direct-drive wind turbine as an example.

[0053] Figure 7 Shows the traditional 30°( Figure 7 a) 45°( Figure 7 b) 60°( Figure 7 c) Halbach array pole pair design, wherein the number of permanent magnets per pole is 6, 4, and 3 respectively. Compared with the 30°, 45°, and 60° Halbach arrays, the NE Halbach array magnetization method of the present invention removes the two permanent magnets for transverse magnetization in the 45° magnetization array, making the magnetic field lines denser and more direct.

[0054] Figure 8 The inner rotor core 31 of the 30°, 45°, 60° Halbach array and the NE Halbach array of the present invention ( Figure 8 a) and stator core 11 ( Figure 8 b) Magnetic density comparison diagram. It can be seen from the figure that with the NE Halbach array of the present invention, the magnetic density at the inner rotor core 31 (away from the air gap side) is the lowest, which is 0.11 T; the magnetic density at the stator core 11 (air gap side) is the highest, which is 0.21 T. It can be seen that the NE Halbach array of the present invention can make the wind turbine have better performance.

[0055] Fig. 9 1 is a torque comparison diagram of different initial angles under each Halbach array. It can be clearly seen from the figure that under the same size, the wind turbine generator of the NE Halbach array of the present invention has the highest torque, which is close to the rated torque.

[0056] Fig.10The torque ripple under each Halbach array is compared. The analysis shows that large torque ripple will affect the stable operation of the motor. Figure 8 , the torque ripples under 30°, 45°, 60° and NE Halbach arrays are 1.31%, 1.15%, 4.21% and 2.46%, respectively, which are all small and have little difference.

[0057] In summary, the speed-increasing semi-direct-drive wind turbine generator and its control method of the present invention have the advantages of small size, high efficiency, low cost, light weight, and high reliability. It can not only efficiently convert wind energy into electrical energy under normal wind speed conditions, but also be used as a motor when the wind speed is lower than the cut-in wind speed, to assist in starting the wind wheel rotation, reduce the starting resistance torque, and realize low wind speed power generation.

Claims

1. A speed-increasing semi-direct-drive wind turbine, characterized in that: It includes a stator, an outer rotor, an inner rotor, and a rotating shaft; one end of the rotating shaft is fixed to the outer rotor, and the other end is connected to the wind wheel main shaft; the stator is connected to the machine-side converter; The stator, the outer rotor and the inner rotor form a two-layer air gap radial structure, wherein the stator is on the outside, the outer rotor is in the middle, and the inner rotor is on the inside; The outer rotor comprises an outer rotor iron block and an outer rotor permanent magnet, adopting a spoke structure, and the outer rotor permanent magnet is pasted to the outer rotor iron block at intervals; the inner rotor comprises an inner rotor iron core and an inner rotor permanent magnet, and the inner rotor permanent magnet is pasted to the outer side of the inner rotor iron core; the outer rotor iron block adopts an I-shaped structure to facilitate better fixation with the outer rotor permanent magnet; The stator includes a stator winding and a stator core. The stator teeth are straight teeth and are used for magnetic field modulation, similar to the magnetic modulation ring of a magnetic gear. The number of teeth of the stator teeth is equal to the sum of the number of pole pairs of the inner rotor and the number of pole pairs of the outer rotor. The stator and the inner rotor form a synchronous motor; the outer rotor, stator teeth and inner rotor form a magnetic gearbox, and its speed ratio is the ratio of the number of pole pairs of the outer rotor to the number of pole pairs of the inner rotor.

2. A speed-increasing semi-direct-drive wind turbine according to claim 1, characterized in that: The inner rotor permanent magnet adopts a NE Halbach array, and the NE Halbach array consists of three blocks to form a pair of poles. The first block consists of a permanent magnet block with a magnetization angle of -135° and a magnetization angle of -90°, the second block consists of a permanent magnet block with a magnetization angle of -45° and a magnetization angle of 45°, and the third block consists of a permanent magnet block with a magnetization angle of 90° and a magnetization angle of 135°.

3. A control method for a speed-increasing semi-direct-drive wind turbine as claimed in claim 1, characterized in that: Use the following steps: Step 1: When the wind speed is lower than the cut-in wind speed, the speed-increasing semi-direct-drive wind turbine generator is operated in the motor + deceleration mode: the machine-side converter is in the inverter state, and the stator winding is energized. At this time, the stator and the inner rotor constitute a motor, and the inner rotor is rotated; the inner rotor, the outer rotor, and the stator teeth constitute a magnetic gearbox, and the inner rotor will drive the outer rotor to rotate, thereby driving the wind wheel main shaft to rotate; at this time, the magnetic gearbox is a reduction gearbox; Step 2, when the wind speed is greater than the cut-in wind speed and the wind rotor speed reaches the grid-connected speed, the speed-increasing semi-direct-drive wind generator is operated in the speed-increasing + generator mode: the machine-side converter is in a rectifying state, and the speed-increasing semi-direct-drive wind generator is controlled to operate; at this time, the wind rotor main shaft drives the outer rotor to rotate, and the outer rotor and the stator teeth and the inner rotor form a magnetic gearbox, then the outer rotor drives the inner rotor to rotate, and the stator and the inner rotor form a generator, then the stator winding outputs current, and the speed-increasing semi-direct-drive wind generator starts to generate electricity; at this time, the magnetic gearbox is a speed-increasing gearbox.

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