CN111435807A

CN111435807A - Flywheel energy storage device and radial magnetic bearing

Info

Publication number: CN111435807A
Application number: CN201910030107.3A
Authority: CN
Inventors: 刘成涛
Original assignee: Candela Shenzhen Technology Innovations Co Ltd
Current assignee: Candela Shenzhen Technology Innovations Co Ltd
Priority date: 2019-01-14
Filing date: 2019-01-14
Publication date: 2020-07-21

Abstract

The invention provides a flywheel energy storage device and a radial magnetic bearing, wherein the radial magnetic bearing comprises a rotor and a stator which are matched with each other; the stator includes a first group of magnets in which a plurality of first magnets are stacked in the axial direction, and the rotor includes a second group of magnets in which a plurality of second magnets are stacked in the axial direction; in the radial direction, the second group of magnets and the first group of magnets are aligned inside and outside and are arranged in pairs in a one-to-one correspondence mode to form a Halbach array. The rotor is positioned at the outer side, and the energy storage density of the flywheel energy storage device is improved.

Description

Flywheel energy storage device and radial magnetic bearing

Technical Field

The invention relates to a radial magnetic bearing, in particular to a radial magnetic bearing suitable for a flywheel energy storage device.

Background

Magnetic bearings suspend the rotor in the air by magnetic force, leaving no mechanical contact between the rotor and the stator. The flywheel energy storage device (also called flywheel energy storage battery) stores energy by utilizing a flywheel rotating at a super high speed, and realizes the mutual conversion of mechanical energy and electric energy through an electromechanical energy conversion device. The magnetic bearing has no mechanical contact, the rotor can run to a very high rotating speed, and the magnetic bearing has the advantages of small mechanical wear, low energy consumption, small noise, long service life, no lubrication, no oil pollution and the like, and is particularly suitable for special environments such as high speed, vacuum, ultra-clean and the like. The magnetic bearing is applied to the flywheel energy storage device, the energy storage density can be greatly improved, the larger the radius of the flywheel rotor is, the larger the rotational inertia of the flywheel rotor is, and the larger the rotational energy obtained at the same rotating speed is.

Most of the existing magnetic bearings are of an inner rotor structure, namely, a rotor is fixed on a shaft, and a stator is arranged on the periphery of the rotor. The design of the inner rotor cannot be suitable for a large-size flywheel rotor, and the energy storage density of the flywheel energy storage device is limited.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a radial magnetic bearing, which is beneficial to improving the energy storage density of a flywheel energy storage device, in view of the above-mentioned defects in the prior art.

The technical scheme adopted by the invention for solving the technical problem comprises the following steps: providing a radial magnetic bearing comprising a rotor and a stator cooperating with each other; the stator includes a first group of magnets in which a plurality of first magnets are stacked in the axial direction, and the rotor includes a second group of magnets in which a plurality of second magnets are stacked in the axial direction; in the radial direction, the second group of magnets and the first group of magnets are aligned inside and outside and are arranged in pairs in a one-to-one correspondence mode to form a Halbach array.

In some embodiments, the Halbach array is a four to eight pair structure.

In some embodiments, from top to bottom, in the first pair, the second magnet is magnetized downward and the first magnet is magnetized downward; in the second pair, the second magnet is magnetized inwards, and the first magnet is magnetized outwards; in the third pair, the direction of magnetization of the second magnet is upward, and the direction of magnetization of the first magnet is upward; in the fourth pair, the second magnet is magnetized outwardly and the first magnet is magnetized inwardly.

In some embodiments, the air gap between the first set of magnets and the second set of magnets is 2 mm.

In some embodiments, the first set of magnets is disposed in a first sleeve; the second set of magnets is disposed in the second sleeve.

In some embodiments, the first sleeve includes a cylindrical main body and a receiving groove provided on the main body and opened to the outside, and the first group of magnets are mounted in the receiving groove; the second sleeve comprises a cylindrical main body and a containing groove which is arranged on the main body and is opened towards the inner side, and the second group of magnets are arranged in the containing groove.

The technical scheme adopted by the invention for solving the technical problem also comprises the following steps: providing a flywheel energy storage device, which comprises a cylindrical flywheel rotor and two radial magnetic bearings which are arranged in the hollow part of the flywheel rotor and are respectively positioned at two ends; wherein, the rotor of the radial magnetic bearing is arranged on the flywheel rotor.

In some embodiments, the flywheel rotor is comprised of a metal cylinder and a carbon ring disposed at the periphery of the metal cylinder.

In some embodiments, two axial magnetic bearings are provided centrally mounted in the flywheel rotor.

In some embodiments, the axial magnetic bearing is composed of magnets, a stator core, silicon steel sheets and coils; wherein all coils are connected in series or in parallel.

Compared with the prior art, the radial magnetic bearing of the invention forms a Halbach array by skillfully enabling the first group of magnets formed by overlapping a plurality of first magnets in the axial direction in the stator and the second group of magnets formed by overlapping a plurality of second magnets in the axial direction in the rotor, and the rotor is positioned at the outer side, thereby being beneficial to improving the energy storage density of the flywheel energy storage device.

Drawings

Fig. 1 is a schematic cross-sectional view of a flywheel energy storage device of the present invention.

Fig. 2 is an exploded view of the flywheel energy storage device of the present invention.

Fig. 3 is a schematic cross-sectional structure of the radial magnetic bearing of the present invention.

FIG. 4 is a schematic diagram of the magnet arrangement of the radial magnetic bearing of the present invention.

FIG. 5 is a perspective view of a single magnet of the radial magnetic bearing of the present invention.

Fig. 6 is a perspective view illustrating a first sleeve in the radial magnetic bearing of the present invention.

Fig. 7 is a perspective view illustrating a rotor in the radial magnetic bearing of the present invention.

Fig. 8 is a schematic view of the distribution of magnetic induction lines in the radial magnetic bearing of the present invention.

Wherein the main reference numerals are as follows: 10. the flywheel energy storage device comprises a flywheel energy storage device 1, a flywheel rotor 11, a metal cylinder 12, a carbon ring 2, an axial magnetic bearing 7, a radial magnetic bearing 3, a first set of

magnets

31, 32, 33, 34, 35, 36, 37, 38, a first magnet 4, a first sleeve 41, a main body 45, a containing groove 5, a second set of

magnets

51, 52, 53, 54, 55, 56, 57, 58, a first magnet 6, a second sleeve 61, a main body 65 and a containing groove.

Detailed Description

The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Referring to fig. 1 and 2, fig. 1 is a schematic cross-sectional structure of a flywheel energy storage device of the present invention. Fig. 2 is an exploded view of the flywheel energy storage device of the present invention. The present invention provides a flywheel energy storage device 10, comprising: the magnetic flywheel comprises a cylindrical flywheel rotor 1, two axial magnetic bearings 2 which are arranged in the hollow position of the flywheel rotor 1 and are positioned in the middle, and two radial magnetic bearings 7 which are arranged in the hollow position of the flywheel rotor 1 and are respectively positioned at two ends. The flywheel rotor 1 is composed of a metal cylinder 11 and a carbon ring 12 arranged on the periphery of the metal cylinder 11. By means of the carbon ring 12 of the carbon fiber material wrapped at the outermost side, the metal cylinder 11 can be prevented from being greatly deformed or even cracked due to high-speed rotation, and the rotating speed and the rotating inertia of the flywheel rotor 1 can be improved.

Referring to fig. 3 to 8, fig. 3 is a schematic sectional structure of the radial magnetic bearing of the present invention. FIG. 4 is a schematic diagram of the magnet arrangement of the radial magnetic bearing of the present invention. FIG. 5 is a perspective view of a single magnet of the radial magnetic bearing of the present invention. Fig. 6 is a perspective view illustrating a first sleeve in the radial magnetic bearing of the present invention. Fig. 7 is a perspective view illustrating a rotor in the radial magnetic bearing of the present invention. Fig. 8 is a schematic view of the distribution of magnetic induction lines in the radial magnetic bearing of the present invention. The radial magnetic bearing 7 of the present invention is composed of a first set of magnets 3, a first sleeve 4, a second set of magnets 5 and a second sleeve 6. Wherein the second group of magnets 5 and the second sleeve 6 are combined to form a stator of the radial magnetic bearing 7, and the first group of magnets 3 and the first sleeve 4 are combined to form a rotor of the radial magnetic bearing 7.

Referring to fig. 1, the first sleeve 4 is combined with the flywheel rotor 1, and rotates with the flywheel rotor 1, so as to drive the first set of magnets 3 mounted on the first sleeve 4 to rotate.

Referring to fig. 4, eight

magnets

31, 32, 33, 34, 35, 36, 37, 38 are stacked in the axial extension of the flywheel rotor 1 to form a first set of magnets 3, and eight

magnets

51, 52, 53, 54, 55, 56, 57, 58 are stacked in the axial extension of the flywheel rotor 1 to form a second set of magnets 5. The second group of magnets 5 and the first group of magnets 3 are aligned inside and outside and are arranged in pairs in one-to-one correspondence to form a Halbach Array (Halbach Array).

From top to bottom, in the first pair, the second magnet 51 and the first magnet 31 are formed into a pair correspondingly along the radial direction of the flywheel rotor 1, the magnetizing direction of the second magnet 51 is downward, and the magnetizing direction of the first magnet 31 is downward. In the second pair, the second magnet 52 and the first magnet 32 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the second magnet 52 is magnetized inward, and the first magnet 32 is magnetized outward. In the third pair, the second magnet 53 and the first magnet 33 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the direction of magnetization of the second magnet 53 is upward, and the direction of magnetization of the first magnet 33 is upward. In the fourth pair, the second magnet 54 and the first magnet 34 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the second magnet 54 is magnetized outward, and the first magnet 34 is magnetized inward.

In the fifth pair, the second magnet 55 and the first magnet 35 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the second magnet 55 is magnetized downward, and the first magnet 35 is magnetized downward. In the sixth pair, the second magnet 56 and the first magnet 36 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the second magnet 56 is magnetized inward, and the first magnet 36 is magnetized outward. In the seventh pair, the second magnet 57 and the first magnet 37 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the direction of magnetization of the second magnet 57 is upward, and the direction of magnetization of the first magnet 37 is upward. In the eighth pair, the second magnet 58 and the first magnet 38 are paired in correspondence with each other in the radial direction of the flywheel rotor 1, the second magnet 58 is magnetized outward, and the first magnet 38 is magnetized inward.

It is worth mentioning that the arrangement of the magnetizing directions of the upper one to four pairs and the lower five to eight pairs are the same. In this embodiment, the Halbach array is illustrated with eight pairs as an example, and in other embodiments, the Halbach array may be flexibly selected from four pairs to eight pairs according to the requirement of practical application.

It will be appreciated that the first set of magnets 3 and the second set of magnets 5 form a Halbach array by virtue of the design in the direction of magnetisation described above. Referring to fig. 8 in combination, for an application where the air gap between the first set of magnets 3 and the second set of magnets 5 is 2mm, the polarities of the magnets on both sides of the air gap repel each other, so that the first set of magnets 3 on the outer side can be in a radially levitated state.

Referring to fig. 5, 6 and 7, a single magnet (e.g., the second magnet 51) of the first and second sets of

magnets

3 and 5 is a magnetic ring. The first sleeve 4 includes a cylindrical main body 41 and a housing groove 45 provided in the main body 41 and opened outward. The second sleeve 6 includes a cylindrical main body 61 and a housing groove 65 provided in the main body 61 and opened inward.

By performing parameter scanning on the radial thickness and the axial height of the magnet 3 of the rotor and the outer diameter of the magnet 5 of the stator, the combination with the maximum radial rigidity and the minimum axial rigidity is found through simulation: in the case of a radial thickness of 10mm for the magnets 3, an axial height of 10mm and an outer diameter of 95mm for the magnets 5 of the stator, the radial stiffness is negative, indicating that the rotor is subjected to a return force in the opposite direction when it undergoes a radial displacement, causing it to return to the equilibrium position, which is 3360N/mm; in the axial direction, however, as soon as the rotor and stator are displaced (assembly accuracy or disturbance during rotation), the magnet 3 of the rotor is subjected to a force that amplifies the displacement, the physical quantity describing the effect of this force being referred to as axial stiffness and having a magnitude of 7275N/mm. It can be seen that radial suspension is realized by the

permanent magnets

3 and 5, and meanwhile, the axial rigidity is increased, and the axial suspension needs an actively controlled electromagnet.

There are a variety of existing implementations of axial magnetic bearings 2 suitable for use in the flywheel energy storage device 10 of the present invention. For example, the axial magnetic bearing 2 is composed of magnets, a stator core, silicon steel sheets, and coils. The stator core is processed by electrician pure iron to form a main structure of a magnetic circuit; the upper stator and the lower stator clamp an axially magnetized annular magnet, and the material is preferably a rare earth permanent magnet-neodymium iron boron; the upper end surface and the lower end surface of the stator core are provided with slots, coils are wound in the middle of the slots, and each magnetic bearing is provided with 8 coils which are symmetrically arranged; the silicon steel sheet is formed by laminating electrical silicon steel with very thin thickness (amorphous alloy and other low iron loss materials can be replaced), and is fixed on the rotor, and an air gap of 0.5mm is arranged between the upper end surface and the lower end surface of the silicon steel sheet and electrical pure iron. The permanent magnets are axially magnetized to produce a bias field at the air gap of about 0.55T. When no current exists in the coil, the axial attractive forces of the pole shoes of the upper stator and the lower stator to the silicon steel sheet are the same. The change relation of the air gap magnetic field along with the ampere turns can be obtained by setting the product of the current I of the coil and the number of turns N as the ampere turns; and meanwhile, the change relation of the electromagnetic force applied to the silicon steel sheet along with ampere turns can be obtained. The stator coils can be connected in series or in parallel, and the wiring mode of the coils is reasonably selected, so that when current flows in the coils, the air gap magnetic field can be changed together, and the electromagnetic force borne by the silicon steel sheets is increased or reduced simultaneously. Due to the axial symmetry design of the structure, when the silicon steel sheet is coaxial with the stator, the resultant force of radial attractive force borne by the silicon steel sheet is zero no matter how the current of the coil changes. Through the design, the current stiffness is calculated to be 0.448N/A, and the axial displacement stiffness is calculated to be 850N/mm.

The flywheel energy storage device 10 actively controls axial displacement through the axial electromagnet, and passively controls radial displacement through the radial Halbach array, so that 5-degree-of-freedom suspension can be realized. The rotor of the radial magnetic bearing 7 is positioned at the outer side, so that the rotational inertia of the flywheel rotor 1 is increased, and the energy storage density of the flywheel energy storage device 10 is improved.

For example, the overall design of flywheel energy storage device 10 is indicated by: 370mm in diameter, 141.5kg in total weight, 370mm in height, 126.5kg in weight of the flywheel rotor, and 1 thickDegree 70mm, moment of inertia 2.6kg m²The thickness of the carbon ring 12 is 13mm and the radial air gap is 2 mm. Wherein, when the rotating speed of the flywheel rotor 1 is 10Krpm, the maximum energy storage is 0.4 KWH; when the rotating speed of the flywheel rotor 1 is 30Krpm, the maximum energy storage is 3.625 KWH; when the rotating speed of the flywheel rotor 1 is 60Krpm, the maximum stored energy is 14.5 KWH.

Compared with the prior art, the flywheel energy storage device 10 of the invention has the advantages that at least:

1. the Halbach array-based radial magnetic bearing 7 can use a small amount of magnets, generates a strong magnetic field in a large air gap (2 mm), realizes radial suspension, and has very large displacement rigidity (3360N/mm); the suspension mode does not need to be controlled, and because the electrical conductivity of the magnet is low, the eddy current loss generated in the high-speed rotation process is also low, which is beneficial to reducing the energy consumption of the flywheel energy storage device 10.

2. The axial magnetic bearing 2 realizes axial suspension through the electromagnet based on permanent magnet bias, all coils are in a serial or parallel connection mode, work together during magnetic suspension debugging, single-channel control is realized, and the magnetic suspension debugging device is simple and convenient.

3. The outer rotor design of the flywheel rotor 1, with the aid of the outermost carbon ring 12, allows further increases in rotational speed and rotational inertia.

It should be understood that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same, and those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some technical features; and such modifications and substitutions are intended to be included within the scope of the appended claims.

Claims

1. A radial magnetic bearing comprises a rotor and a stator which are matched with each other; the stator comprises a first group of magnets formed by stacking a plurality of first magnets in the axial direction, and the rotor comprises a second group of magnets formed by stacking a plurality of second magnets in the axial direction; in the radial direction, the second group of magnets and the first group of magnets are aligned inside and outside and are arranged in pairs in a one-to-one correspondence mode to form a Halbach array.

2. The radial magnetic bearing of claim 1 wherein the Halbach array is a four to eight pair configuration.

3. The radial magnetic bearing of claim 2 wherein, from top to bottom, in the first pair, the direction of magnetization of the second magnet is downward and the direction of magnetization of the first magnet is downward; in the second pair, the second magnet is magnetized inwards, and the first magnet is magnetized outwards; in the third pair, the direction of magnetization of the second magnet is upward, and the direction of magnetization of the first magnet is upward; in the fourth pair, the second magnet is magnetized outwardly and the first magnet is magnetized inwardly.

4. The radial magnetic bearing of claim 1 wherein the air gap between the first set of magnets and the second set of magnets is 2 mm.

5. The radial magnetic bearing of claim 1 wherein the first set of magnets are mounted in a first sleeve; the second set of magnets is disposed in the second sleeve.

6. The radial magnetic bearing of claim 5 wherein the first sleeve comprises a cylindrical body and a housing provided on the body and open to the outside, the first set of magnets being received in the housing; the second sleeve comprises a cylindrical main body and a containing groove which is arranged on the main body and is opened towards the inner side, and the second group of magnets are arranged in the containing groove.

7. A flywheel energy storage device, comprising a cylindrical flywheel rotor, characterized by further comprising two radial magnetic bearings according to any one of claims 1 to 6 installed in the hollow of the flywheel rotor and respectively located at both ends; wherein, the rotor of the radial magnetic bearing is arranged on the flywheel rotor.

8. The radial magnetic bearing of claim 7, wherein the flywheel rotor is comprised of a metal cylinder and a carbon ring disposed at the periphery of the metal cylinder.

9. The radial magnetic bearing of claim 7 further comprising two axial magnetic bearings mounted centrally within the hollow of the flywheel rotor.

10. The radial magnetic bearing of claim 9, wherein the axial magnetic bearing is comprised of magnets, stator cores, silicon steel sheets, and coils; wherein all coils are connected in series or in parallel.