An electromagnetic gearbox for a double-fed wind turbine generator and a control method thereof

Abstract

The present invention relates to an electromagnetic gearbox for a doubly-fed wind turbine generator and a control method thereof, and belongs to the field of wind power. The electromagnetic gearbox comprises a first-stage planetary electromagnetic gear, a second-stage coaxial magnetic gear, and a third-stage coaxial magnetic gear; the first-stage planetary electromagnetic gear comprises an electromagnetic gear ring, a planetary magnetic gear, a planet carrier, a sun magnetic gear, etc.; the electromagnetic gear ring consists of an iron core and a winding. The control method is: control the polarity of the electromagnetic gear ring winding so that the number of pole pairs of the electromagnetic gear ring at startup is half of its rated number of pole pairs, and the number of pole pairs of the electromagnetic gear ring after startup is its rated number of pole pairs; when the wind speed is greater than the rated wind speed, adjust the winding current of the electromagnetic gear ring to adjust the output torque of the first-stage planetary electromagnetic gear to achieve constant power control; when the wind speed is greater than the cut-out wind speed, cut off the winding power supply of the electromagnetic gear ring to achieve decoupling of the wind wheel and the generator, and reduce the braking force of the generator. The present invention can reduce the operation and maintenance cost; the speed increase ratio can be adjusted in real time, which can improve the flexibility of system operation.

Description

Technical Field

[0001] The invention relates to a gear box and a control method thereof, in particular to an electromagnetic gear box for a double-fed wind generator and a control method thereof, belonging to the technical field of wind power generation. Background Art

[0002] Doubly-fed wind power generation system is mainly composed of wind rotor, gearbox, doubly-fed wind turbine generator (DFIG), converter system, etc. DFIG is a high-speed, small-volume generator. Since the wind rotor runs at a low speed, a gearbox with a high speed increase ratio is usually used to increase the lower wind rotor speed to a high-speed generator rotor speed. However, the existing gearbox uses mechanical gear meshing, which requires a complex oil injection and lubrication system. It is large, heavy, costly, noisy, has a high failure rate, and requires regular maintenance. In addition, the main losses of the doubly-fed wind power generation system come from the gearbox and converter system, of which about 65% of the system losses come from the gearbox. Therefore, it is necessary to study the use of a new type of gearbox in order to reduce the cost and loss of the system and improve the reliability of the system operation.

[0003] Magnetic gears have the characteristics of physical isolation and no mechanical contact, so they have the advantages of no wear, maintenance-free, noise-free, no lubrication, and overload protection. In recent years, they have received more and more attention and application. However, existing magnetic gears cannot change the speed ratio in real time, which affects their application and promotion in wind power generation systems. Summary of the invention

[0004] The main purpose of the present invention is to propose an electromagnetic gearbox with no mechanical contact, no need for lubrication, small size, light weight, low energy consumption, and real-time adjustable speed ratio, thereby greatly reducing the operation and maintenance costs of doubly-fed wind turbine generator sets and improving system reliability and flexibility.

[0005] In order to achieve the above objectives, the present invention provides an electromagnetic gearbox for a doubly-fed wind turbine generator, comprising: a first-stage planetary electromagnetic gear, a second-stage coaxial magnetic gear, a third-stage coaxial magnetic gear, and a main control system.

[0006] The first-stage planetary electromagnetic gear includes: an electromagnetic gear ring, a planetary magnetic gear, a planetary carrier, a sun magnetic gear, a first-stage driving shaft, and a first-stage driven shaft; the electromagnetic gear ring is composed of a gear ring core and a winding; the first-stage driving shaft is integrated with the planetary carrier, and the planetary magnetic gear is installed on the planetary carrier, and at the same time, the torque is transmitted to the electromagnetic gear ring and the sun magnetic gear through electromagnetic force; the shaft of the sun magnetic gear drives the first-stage driven shaft to rotate through a spline.

[0007] The second-stage coaxial magnetic gear includes: a second-stage driving shaft, a second-stage driven shaft and a second coaxial magnetic gear; the second coaxial magnetic gear is composed of an outer rotor magnetic gear, an inner rotor magnetic gear and a magnetic adjustment ring; the outer rotor magnetic gear is composed of an outer rotor core and a Halbach permanent magnet array attached to the outer rotor core; the inner rotor magnetic gear is composed of an inner rotor core and a Halbach permanent magnet array attached to the inner rotor core; the magnetic adjustment ring includes a magnetic adjustment magnet block and a non-magnetic conductive material, and is fixedly installed between the outer rotor magnetic gear and the inner rotor magnetic gear.

[0008] The third-stage coaxial magnetic gear comprises: a third-stage driving shaft, a third-stage driven shaft and a third coaxial magnetic gear, and its structure is the same as that of the second-stage coaxial magnetic gear.

[0009] The first-stage driving shaft of the first-stage planetary electromagnetic gear is connected to the wind wheel main shaft by a shrink sleeve; the first-stage driven shaft of the first-stage planetary electromagnetic gear is connected to the second-stage driving shaft of the second-stage coaxial magnetic gear; the second-stage driven shaft of the second-stage coaxial magnetic gear is connected to the third-stage driving shaft of the third-stage coaxial magnetic gear, and the third-stage driven shaft of the third-stage coaxial magnetic gear is fixed to a coupling; the other end of the coupling is fixed to the rotating shaft of the doubly fed wind generator.

[0010] The windings of the electromagnetic gear ring of the first-stage planetary electromagnetic gear are connected in the following manner: the two ends of every two adjacent windings are connected to the busbar L1 and the busbar L2 respectively, and the two ends of the other two adjacent windings are connected to the busbar L3 and the busbar L4 respectively; and so on, all windings are connected to the busbars L1, L2, L3, and L4 respectively.

[0011] The control method of the electromagnetic gearbox for the doubly-fed wind turbine generator comprises the following steps:

[0012] Step 1, when the wind speed reaches the cut-in wind speed, the control power supply is turned on, so that the busbars L1 and L2 are connected to the positive and negative poles of the control power supply respectively; at the same time, the busbars L3 and L4 are connected to the negative and positive poles of the control power supply respectively; then at this time, the number of pole pairs of the electromagnetic gear ring is half of its rated number of pole pairs, so that the speed increase ratio of the first-stage planetary magnetic gear is reduced, and the equivalent rotational inertia is reduced, so that the starting torque of the wind turbine set becomes smaller, and low wind speed starting can be achieved.

[0013] Step 2, after starting, keep the busbars L1 and L2 connected to the positive and negative poles of the control power supply respectively; at the same time, connect the busbars L3 and L4 to the positive and negative poles of the control power supply respectively; then the number of pole pairs of the electromagnetic gear ring is equal to its rated number of pole pairs, achieving normal operation.

[0014] Step 3, when the wind speed is greater than or equal to the rated wind speed, adjust the winding current of the electromagnetic gear ring to reduce the magnetic flux density generated by the electromagnetic gear ring, thereby adjusting the output torque of the first-stage planetary electromagnetic gear to achieve constant power control.

[0015] Step 4, when the wind speed is greater than or equal to the cut-out wind speed, the control power supply is cut off, the winding of the electromagnetic gear ring is de-energized, and no electromagnetic force is generated, so that the first-stage planetary electromagnetic gear has no power output, and the wind wheel and the generator are decoupled, thereby greatly reducing the braking force of the generator.

[0016] The beneficial effects of the present invention are:

[0017] 1) No mechanical contact, mechanical isolation is achieved, the mechanical vibration of the wind wheel will not be transmitted to the subsequent stage, which can effectively solve the resonance problem;

[0018] 2) No lubrication is required, eliminating the need for a complex oil injection lubrication system. It is small in size, light in weight, and has low energy consumption, which can greatly reduce the operation and maintenance costs of doubly-fed wind turbines.

[0019] 3) The speed ratio can be adjusted in real time. On the one hand, it can reduce the equivalent rotational inertia and achieve low wind speed starting; on the other hand, it can assist constant power control and decouple the wind wheel from the generator, thereby greatly reducing the braking force of the generator and improving system reliability and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the topological structure of the doubly-fed wind power generation system adopted in the present invention.

[0021] Figure 2 This is a schematic diagram of the structure of the first-stage planetary electromagnetic gear of the present invention.

[0022] Figure 3 It is a schematic diagram of the planetary magnetic gear in the first-stage planetary electromagnetic gear of the present invention.

[0023] Figure 4 It is a schematic diagram of the second coaxial magnetic gear of the present invention.

[0024] Figure 5 It is a schematic diagram of the connection between the second-stage coaxial magnetic gear and the third-stage coaxial magnetic gear of the present invention.

[0025] Figure 6 It is a schematic diagram of the connection mode of the electromagnetic ring gear winding in the first-stage planetary electromagnetic gear of the present invention.

[0026] Figure 7 This is a circuit diagram of the polarity control of the electromagnetic ring gear winding in the first-stage planetary electromagnetic gear of the present invention.

[0027] Figure 8Schematic diagram of the second connection method of the electromagnetic ring gear winding in the first-stage planetary electromagnetic gear of the present invention.

[0028] Fig. 9 Schematic diagram of the third connection method of the electromagnetic ring gear winding in the first-stage planetary electromagnetic gear of the present invention.

[0029] Fig.10 Schematic diagram of the fourth wiring method of the electromagnetic ring gear winding in the first-stage planetary electromagnetic gear of the present invention.

[0030] Among them, 1-first-stage planetary electromagnetic gear; 2-second-stage coaxial magnetic gear; 3-third-stage coaxial magnetic gear; 4-first-stage driving shaft; 5-third-stage driven shaft; 6-wind wheel, 61-wind wheel main shaft; 7-coupling; 8-doubly fed wind turbine; 11-electromagnetic gear ring; 12-sun magnetic gear; 13-planetary magnetic gear; 14-planet carrier; 21-outer rotor magnetic gear of the second coaxial magnetic gear; 22-magnetic adjustment ring of the second coaxial magnetic gear; 23-inner rotor magnetic gear of the second coaxial magnetic gear; 111-iron core of the electromagnetic gear ring, 112-winding of the electromagnetic gear ring; 131-permanent magnet of the planetary magnetic gear; 132-iron core of the planetary magnetic gear; 211-Halbach permanent magnet array of the outer rotor of the second coaxial magnetic gear; 231-Halbach permanent magnet array of the inner rotor of the second coaxial magnetic gear. DETAILED DESCRIPTION

[0031] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0032] like Figure 1 As shown, the doubly-fed wind power generation system adopted by the present invention includes a wind wheel 6 and its main shaft 61, an electromagnetic gearbox of the present invention, a coupling 7 and a doubly-fed wind generator 8; the electromagnetic gearbox of the present invention includes: a first-stage planetary electromagnetic gear 1, a second-stage coaxial magnetic gear 2, a third-stage coaxial magnetic gear 3, and a main control system.

[0033] like Figure 1 , Figure 2 As shown, the first-stage planetary electromagnetic gear 1 includes: an electromagnetic ring gear 11, a planetary magnetic gear 13, a planetary carrier 14, a sun magnetic gear 12, a first-stage driving shaft 4, and a first-stage driven shaft; the electromagnetic ring gear 11 is composed of a ring gear core 111 and a DC winding 112; the first-stage driving shaft 4 is integrated with the planetary carrier 14, and the planetary magnetic gear 13 is installed on the planetary carrier 14, and the electromagnetic ring gear 11 and the sun magnetic gear 12 are used to transmit torque through electromagnetic force. The shaft of the sun magnetic gear 12 drives the first-stage driven shaft to rotate through a spline. The number of planetary magnetic gears 13 is 3 or more, and the specific number is determined by the required transmission torque.

[0034] The planetary magnetic gear 13 includes a permanent magnet 131 and an iron core 132. A straight groove or a groove may be used between adjacent permanent magnets 131. Figure 3 As shown, the inclined groove is adopted, so that the cogging torque can be effectively reduced.

[0035] like Figure 4 , Figure 5 As shown, the second-stage coaxial magnetic gear 2 includes: a second-stage driving shaft, a second-stage driven shaft and a second coaxial magnetic gear; the second coaxial magnetic gear is composed of an outer rotor magnetic gear 21, a magnetic adjustment ring 22 and an inner rotor magnetic gear 23, the outer rotor magnetic gear 21 is composed of an outer rotor core and a Halbach permanent magnet array 211 attached to the outer rotor core, and the number of pole pairs of the outer rotor magnetic gear 21 is P o , each pole is composed of a radially magnetized permanent magnet and a tangentially magnetized permanent magnet; the inner rotor magnetic gear 23 is composed of an inner rotor core and a Halbach permanent magnet array attached to the inner rotor core, and the number of pole pairs of the inner rotor magnetic gear 23 is P i Each pole is composed of a radially magnetized permanent magnet and two permanent magnets with magnetization angles of α and -α respectively distributed on both sides of the radially magnetized permanent magnet; the magnetic adjustment ring 22 includes N s A magnetic adjustment block and a non-magnetic conductive material are fixedly installed between the outer rotor magnetic gear 21 and the inner rotor magnetic gear 23. s Satisfies the following formula: N s =P o +P i .

[0036] The third-stage coaxial magnetic gear 3 comprises: a third-stage driving shaft, a third-stage driven shaft and a third coaxial magnetic gear, and its structure is the same as that of the second-stage coaxial magnetic gear 2 .

[0037] like Figure 1 , Figure 5 As shown, the driving shaft 4 of the first-stage planetary electromagnetic gear 1 is connected to the wind wheel main shaft 61 by a shrink sleeve; the driven shaft of the first-stage planetary electromagnetic gear 1 is connected to the driving shaft of the second-stage coaxial magnetic gear 2; the driven shaft of the second-stage coaxial magnetic gear 2 is connected to the driving shaft of the third-stage coaxial magnetic gear 3, and the driven shaft 5 of the third-stage coaxial magnetic gear 3 is fixed to the coupling 7; the other end of the coupling 7 is fixed to the rotating shaft of the doubly fed wind turbine 8.

[0038] like Figure 6 As shown, the connection method of the winding 111 of the electromagnetic ring gear 11 of the first-stage planetary electromagnetic gear is as follows: the two ends of two adjacent windings are connected to the busbars L1 and L2 respectively, and the two ends of the other two adjacent windings are connected to the busbars L3 and L4 respectively. Similarly, all windings are connected to the busbars L1, L2, L3, and L4 respectively. Terminals X1, X2, X3, and X4 are connected to the busbars L1, L2, L3, and L4 respectively.

[0039] like Figure 7 As shown, terminals X1 and X2 are respectively connected to the positive (+) and negative (-) poles of the control power supply; pins K1:1 and K1:2 of contactor K1 are respectively connected to the positive (+) and negative (-) poles of the control power supply, and pins K1:3 and K1:4 of contactor K1 are respectively connected to terminals X3 and X4; pins K2:1 and K2:2 of contactor K2 are respectively connected to the negative (-) and positive (+) poles of the control power supply, and pins K2:3 and K2:4 of contactor K2 are respectively connected to terminals X3 and X4.

[0040] The control method of the electromagnetic gearbox for the doubly-fed wind turbine generator comprises the following steps:

[0041] Step 1: When the wind speed reaches the cut-in wind speed, turn on the control power supply. Figure 7 , Figure 8 As shown, the terminals X1 and X2 are positive (+) and negative (-), respectively, and the busbars L1 and L2 are also positive and negative, respectively, so that all electromagnetic gear ring windings connected to the busbar L1 have their magnetic poles in the N pole, and all electromagnetic gear ring windings connected to the busbar L2 have their magnetic poles in the S pole. At the same time, Figure 7 As shown, the main control system keeps the contactor K1 open and controls the contactor K2 to close, then the terminals X3 and X4 are connected to the negative pole (-) and positive pole (+) of the control power supply respectively, and the busbars L3 and L4 are also negative and positive respectively, so that all the electromagnetic gear ring windings connected to the busbar L3 make their magnetic poles S poles, and all the electromagnetic gear ring windings connected to the busbar L4 make their magnetic poles N poles, so at this time the pole pair number P of the electromagnetic gear ring 11 b Its rated pole pair number P bN Half of (ie: P b =0.5P bN ), thereby reducing the speed increase ratio of the first-stage planetary electromagnetic gear 1 and reducing the equivalent rotational inertia converted to the low-speed shaft (i.e., the first-stage driving shaft 4 of the first-stage planetary electromagnetic gear 1), and the starting torque of the wind turbine set becomes smaller, which can achieve low wind speed starting.

[0042] The total speed increase ratio i of the electromagnetic gearbox of the present invention is:

[0043]

[0044] Where P b is the number of pole pairs of the electromagnetic gear ring 11, P a The number of pole pairs of the sun magnetic gear 13, P o is the number of pole pairs of the second coaxial magnetic gear outer rotor 21, P i is the number of pole pairs of the second coaxial magnetic gear inner rotor 23, P o2 is the number of pole pairs of the outer rotor of the third coaxial magnetic gear, P i2is the number of pole pairs of the inner rotor of the third coaxial magnetic gear.

[0045] It can be seen from formula (1) that the pole pair number P of the electromagnetic gear ring 11 is b The total speed ratio i decreases as the speed ratio decreases. The equivalent moment of inertia is related to the square of the speed ratios of each stage. Therefore, if the speed ratio of the first-stage planetary electromagnetic gear 1 decreases, the equivalent moment of inertia will decrease, which is beneficial for the wind turbine to start at low wind speeds.

[0046] Step 2: After startup, Figure 7 , Fig. 9 As shown, terminals X1 and X2 are still connected to the positive (+) and negative (-) poles of the control power supply respectively, all electromagnetic gear ring windings connected to bus L1 still have their magnetic poles in the N pole, and all electromagnetic gear ring windings connected to bus L2 still have their magnetic poles in the S pole. Figure 7 As shown, the main control system controls the contactor K2 to be disconnected and the contactor K1 to be closed, then the terminals X3 and X4 are respectively connected to the positive (+) and negative (-) poles of the control power supply, and the busbars L3 and L4 are also respectively positive and negative poles, so that all the electromagnetic gear ring windings connected to the busbar L3 have their magnetic poles in the N pole, and all the electromagnetic gear ring windings connected to the busbar L4 have their magnetic poles in the S pole. At this time, the pole pair number P of the electromagnetic gear ring 11 is b Equal to its rated pole pair number P bN (ie: P b =P bN ) to achieve normal operation.

[0047] Step 3, when the wind speed is greater than or equal to the rated wind speed, adjust the current of the electromagnetic gear ring winding 111 to reduce the magnetic flux density, thereby adjusting the output torque of the first-stage planetary electromagnetic gear 1 to achieve constant power control. Figure 7 , Fig.10 As shown, the main control system disconnects contactor K1 and contactor K2, then terminals X3 and X4 lose power, busbars L3 and L4 also lose power, and all electromagnetic gear ring windings connected to busbars L3 and L4 lose power, and their magnetic poles are not polar. At this time, the number of pole pairs of the electromagnetic gear ring 11 is half of the rated number of pole pairs, which reduces the total speed increase ratio i and the transmitted torque, thereby reducing the output power of the first-stage planetary electromagnetic gear 1 and realizing constant power control.

[0048] Step 4: When the wind speed is greater than or equal to the cut-out wind speed, Figure 6 As shown, when the main control system cuts off the control power supply, all windings 111 of the electromagnetic ring gear 11 lose power, and there is no electromagnetic force between the electromagnetic ring gear 11 and the planetary magnetic gear 13, so there is no torque transmission, so that the first-stage planetary electromagnetic gear 1 has no power output, and the wind wheel and the generator are decoupled, thereby greatly reducing the braking force of the generator.

Claims

1. An electromagnetic gearbox for a doubly-fed wind turbine generator, characterized in that: include: First-stage planetary electromagnetic gear, second-stage coaxial magnetic gear, third-stage coaxial magnetic gear; The first-stage planetary electromagnetic gear comprises: an electromagnetic gear ring, a planetary magnetic gear, a planet carrier, a sun magnetic gear, a first-stage driving shaft, and a first-stage driven shaft; the electromagnetic gear ring is composed of a gear ring iron core and a winding; the first-stage driving shaft is integrated with the planet carrier, and the planetary magnetic gear is installed on the planet carrier, and transmits torque to the electromagnetic gear ring and the sun magnetic gear through electromagnetic force; the shaft of the sun magnetic gear drives the first-stage driven shaft to rotate through a spline; The second-stage coaxial magnetic gear comprises: a second-stage driving shaft, a second-stage driven shaft and a second coaxial magnetic gear; the second coaxial magnetic gear is composed of an outer rotor magnetic gear, an inner rotor magnetic gear and a magnetic adjustment ring; the outer rotor magnetic gear is composed of an outer rotor core and a Halbach permanent magnet array attached to the outer rotor core; the inner rotor magnetic gear is composed of an inner rotor core and a Halbach permanent magnet array attached to the inner rotor core; the magnetic adjustment ring is fixedly installed between the outer rotor magnetic gear and the inner rotor magnetic gear; The third-stage coaxial magnetic gear comprises: a third-stage driving shaft, a third-stage driven shaft and a third coaxial magnetic gear, and its structure is the same as that of the second-stage coaxial magnetic gear; The first-stage driving shaft of the first-stage planetary electromagnetic gear is connected to the main shaft of the wind wheel by a shrink sleeve; the first-stage driven shaft of the first-stage planetary electromagnetic gear is connected to the second-stage driving shaft of the second-stage coaxial magnetic gear; the second-stage driven shaft of the second-stage coaxial magnetic gear is connected to the third-stage driving shaft of the third-stage coaxial magnetic gear, and the third-stage driven shaft of the third-stage coaxial magnetic gear is fixed to the coupling; the other end of the coupling is fixed to the rotating shaft of the doubly-fed wind turbine generator; The windings of the electromagnetic gear ring of the first-stage planetary electromagnetic gear are connected in the following manner: the two ends of every two adjacent windings are connected to the busbar L1 and the busbar L2 respectively, and the two ends of the other two adjacent windings are connected to the busbar L3 and the busbar L4 respectively; and so on, all windings are connected to the busbars L1, L2, L3, and L4 respectively.

2. A control method for an electromagnetic gearbox for a doubly-fed wind turbine generator as claimed in claim 1, characterized in that: Use the following steps: Step 1, when the wind speed reaches the cut-in wind speed, the control power supply is turned on, so that the busbars L1 and L2 are connected to the positive and negative poles of the control power supply respectively; at the same time, the busbars L3 and L4 are connected to the negative and positive poles of the control power supply respectively; then at this time, the number of pole pairs of the electromagnetic gear ring is half of its rated number of pole pairs, so that the speed increase ratio of the first-stage planetary magnetic gear is reduced, and the equivalent moment of inertia is reduced, so that the starting torque of the wind turbine set becomes smaller, and low wind speed starting can be achieved; Step 2, after starting, the busbars L1 and L2 are still connected to the positive and negative electrodes of the control power supply respectively; at the same time, the busbars L3 and L4 are connected to the positive and negative electrodes of the control power supply respectively; then at this time, the number of pole pairs of the electromagnetic gear ring is equal to its rated number of pole pairs, and normal operation is achieved; Step 3, when the wind speed is greater than or equal to the rated wind speed, adjusting the winding current of the electromagnetic gear ring to reduce the magnetic flux density generated by the electromagnetic gear ring, thereby adjusting the output torque of the first-stage planetary electromagnetic gear to achieve constant power control; Step 4, when the wind speed is greater than or equal to the cut-out wind speed, the control power supply is cut off, the winding of the electromagnetic gear ring is de-energized, and no electromagnetic force is generated, so that the first-stage planetary electromagnetic gear has no power output, and the wind wheel and the generator are decoupled, thereby greatly reducing the braking force of the generator.

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