Direct-driven double-rotor tidal current energy permanent magnet generator

Abstract

The invention discloses a direct drive type double-rotor tidal current energy permanent magnet generator. An inner rotor, a stator and an outer rotor of the generator are coaxially sleeved and installed on a chassis from inside to outside, a rotating shaft is coaxially sleeved at the center of the inner rotor and welded at the center of the chassis, and a plurality of V-shaped magnetism gathering type permanent magnets used for generating a magnetic field and reducing energy consumption are evenly installed in the inner rotor at intervals in the circumferential direction. A plurality of stator winding frames are evenly installed in the stator at intervals in the circumferential direction, a stator modulation block used for adjusting air gap magnetic field distribution is installed in each stator winding frame, and a plurality of outer rotor permanent magnet steel with surface pole cutting structures are evenly installed in the outer rotor at intervals in the circumferential direction. The direct-driven double-rotor tidal current energy permanent magnet generator can solve the problems of low power generation transmission efficiency, torque pulsation of the generator and the like, has the characteristics of high efficiency, high power density and the like, and can meet the performance requirements of related power generation occasions in the ocean energy field.

Description

Technical Field

[0001] The invention relates to a permanent magnet generator, in particular to a direct-drive dual-rotor tidal current energy permanent magnet generator. Background Art

[0002] The massive consumption of traditional fossil energy such as coal, oil and natural gas has not only led to the depletion of resources, but also brought serious environmental pollution and climate change problems. New energy is clean and renewable, and is the key to achieving energy structure transformation. The development and utilization of new energy is of great significance for ensuring energy security and reducing dependence on fossil energy. As a renewable energy with great potential, tidal energy is of great significance for reducing environmental pollution, responding to climate change, ensuring energy security and promoting sustainable economic development. With the advancement of technology and the reduction of costs, tidal energy is expected to occupy a more important position in the future energy structure.

[0003] Tidal energy power generation is the main way to utilize tidal energy. Traditional tidal energy generators include vertical axis turbine generators. Due to the influence of tidal flow velocity, the turbine speed is different from that of traditional generators. A speed increaser must be used between traditional generators and turbines, which increases the maintenance workload. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a direct-drive dual-rotor tidal current energy permanent magnet generator. The present invention adopts a permanent magnet generator to save the use of a speed increaser, directly connects to a water turbine, optimizes the space volume of the tidal current energy power generation device, optimizes the device structure, does not require an external excitation device for excitation, and generates a magnetic field through the internal permanent magnet material rotor structure, thereby realizing tidal current energy generation.

[0005] The technical solution adopted by the present invention is:

[0006] The direct-drive dual-rotor tidal energy permanent magnet generator of the present invention comprises an inner rotor, a stator, an outer rotor, a rotating shaft and a chassis. The inner rotor, the stator and the outer rotor are coaxially mounted from the inside to the outside and the ends are mounted on the chassis. The rotating shaft is coaxially mounted in the center of the inner rotor and welded to the center of the chassis. A plurality of V-shaped magnetic concentrating permanent magnets for generating a magnetic field and reducing energy consumption are evenly installed along the circumferential direction in the inner rotor. A plurality of stator winding frames are evenly installed along the circumferential direction in the stator. A stator modulation block for adjusting the air gap magnetic field distribution is installed in each stator winding frame. A plurality of outer rotor permanent magnets with surface clipping structures are evenly installed along the circumferential direction in the outer rotor.

[0007] The stator also includes a stator inner shell, a plurality of stator winding frames, a plurality of three-phase centralized armature windings and a stator outer shell. The stator winding frames are I-shaped and have arc-shaped sides. Each stator winding frame is evenly spaced and installed between the stator inner shell and the stator outer shell along the circumferential direction, and the two end surfaces are close to the inner side surfaces of the stator inner shell and the stator outer shell; each stator modulation block is placed in the center of the winding frame middle column of each stator winding frame along the length direction of the winding frame middle column of the stator winding frame, and the stator modulation block can optimize the electromagnetic performance of the motor after adjusting the distribution of the air gap magnetic field; each three-phase centralized armature winding is wound on the winding frame middle column of each stator winding frame, and each three-phase centralized armature winding is evenly spaced and arranged along the circumferential direction. The winding frame middle column supports the three-phase centralized armature winding to ensure the neatness and accuracy of the three-phase centralized armature winding; the inner rotor and the outer rotor are respectively sleeved in the stator inner shell and outside the stator outer shell.

[0008] The three-phase centralized armature winding is arranged according to the three-phase alternating current operation. Each stator slot of the stator contains two three-phase centralized armature windings and each is independent of three groups, namely, phase A, phase B and phase C. The number of coil turns and resistance of each phase of the three-phase centralized armature winding are equal. The phase difference between two adjacent three-phase centralized armature windings is 120 degrees and is symmetrically distributed. When the three-phase centralized armature winding is in a rotating magnetic field, a back electromotive force with a phase difference of 120 degrees is induced.

[0009] The inner rotor also includes an inner rotor inner shell, an inner rotor iron frame, an inner rotor permanent magnet sleeve and an inner rotor outer shell. The inner rotor inner shell is sequentially mounted with the inner rotor iron frame, the inner rotor permanent magnet sleeve and the inner rotor outer shell. The inner rotor permanent magnet sleeve is evenly spaced along the circumferential direction with V-shaped permanent magnet holes. Each V-shaped magnetic concentrating permanent magnet is installed in a respective V-shaped permanent magnet hole. The rotating shaft is coaxially located at the center of the inner rotor inner shell, and the V-shaped tip of each V-shaped magnetic concentrating permanent magnet faces the central rotating shaft. The inner rotor plays a role of fixed support and protection. The V-shaped magnetic concentrating permanent magnet is in the inner rotor permanent magnet sleeve. The V-shaped magnetic concentrating permanent magnet is used to generate a magnetic field to reduce the consumption of electric energy and improve the efficiency of the motor.

[0010] The inner rotor permanent magnet sleeve is made of aluminum material, and the V-shaped magnetic concentrating permanent magnet is made of neodymium iron boron material.

[0011] The outer rotor also includes an outer rotor inner shell, an outer rotor permanent magnet sleeve, an outer rotor iron frame and an outer rotor outer shell. The outer rotor inner shell is sequentially mounted with the outer rotor permanent magnet sleeve, the outer rotor iron frame and the outer rotor outer shell. The outer rotor permanent magnet sleeve is evenly spaced along the circumferential direction with magnetic steel holes. Each outer rotor permanent magnet is installed in a respective magnetic steel hole and faces a V-shaped magnetic concentrating permanent magnet. Each outer rotor permanent magnet is alternately magnetized radially along the circumferential direction of the air gap of the outer rotor. The inner rotor and the outer rotor can be operated simultaneously or separately to generate torque to improve the power density and efficiency of the motor.

[0012] The surface of the outer rotor permanent magnet steel on one side facing the inner shell of the outer rotor adopts a surface clipping structure.

[0013] The beneficial effects of the present invention are:

[0014] The direct-drive dual-rotor tidal energy permanent magnet generator of the present invention can solve the problems of low power generation transmission efficiency and generator torque pulsation, and has the characteristics of high efficiency and high power density to meet the performance requirements of relevant power generation occasions in the field of marine energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the radial overall design diagram of the motor of the present invention;

[0016] Figure 2 Three versions of permanent magnet steel simulation diagrams designed for the motor of the present invention, wherein: Figure 2 (a) is a simulation diagram of the permanent magnet steel of the initial generator M1 of the motor design of the present invention, Figure 2 (b) is a simulation diagram of the permanent magnet steel of the intermediate generator M2 of the motor design of the present invention, Figure 2 (c) is a simulation diagram of the permanent magnet steel of the final generator M3 of the motor design of the present invention;

[0017] Figure 3 Schematic diagram of the influence of the main air gap harmonics of the initial generator M1 of the present invention on the torque and torque ripple;

[0018] Figure 4 It is a schematic diagram comparing the no-load induced electromotive force of the initial generator M1, the intermediate generator M2 and the final generator M3 of the present invention;

[0019] Figure 5 It is a schematic diagram for comparing the load torques of the initial generator M1, the intermediate generator M2 and the final generator M3 of the present invention;

[0020] Figure 6 It is a schematic diagram of the before and after comparison of the no-load induced electromotive force of the initial generator M1 and the final generator M3 of the present invention;

[0021] Figure 7 Schematic diagram of the before and after comparison of the air gap magnetic density harmonic amplitudes in the initial generator M1 and the final generator M3 of the present invention;

[0022] Figure 8 Schematic diagram of the before and after comparison of the external air gap magnetic flux harmonic amplitude of the initial generator M1 and the final generator M3 of the present invention;

[0023] In the figure: 1, inner rotor, 2, inner rotor inner shell, 3, inner rotor iron frame, 4, V-shaped magnetic concentrating permanent magnet, 5, inner rotor permanent magnet sleeve, 6, inner rotor outer shell, 7, stator, 8, stator inner shell, 9, stator winding frame, 10, winding frame center column, 11, stator modulation block, 12, three-phase concentrated armature winding, 13, stator outer shell, 14, outer rotor, 15, outer rotor inner shell, 16, outer rotor permanent magnet sleeve, 17, outer rotor permanent magnet steel, 18, outer rotor iron frame, 19, outer rotor outer shell, 20, rotating shaft, 21, chassis. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] like Figure 1 As shown, the direct-drive dual-rotor tidal energy permanent magnet generator of the present invention includes an inner rotor 1, a stator 7, an outer rotor 14, a rotating shaft 20 and a chassis 21. The inner rotor 1, the stator 7 and the outer rotor 14 are coaxially mounted from the inside to the outside and the ends are installed on the chassis 21. The rotating shaft 20 is coaxially mounted in the center of the inner rotor 1 and welded to the center of the chassis 21. A plurality of V-shaped magnetic concentrating permanent magnets 4 for generating a magnetic field and reducing energy consumption are evenly installed in the inner rotor 1 along the circumferential direction. A plurality of stator winding frames 9 are evenly installed in the stator 7 along the circumferential direction. A stator modulation block 11 for adjusting the air gap magnetic field distribution is installed in each stator winding frame 9. A plurality of outer rotor permanent magnets 17 with surface clipping structures are evenly installed in the outer rotor 14 along the circumferential direction.

[0026] The stator 7 also includes a stator inner shell 8, a plurality of stator winding frames 9, a plurality of three-phase centralized armature windings 12 and a stator outer shell 13. The stator winding frame 9 is I-shaped and has arc-shaped sides. Each stator winding frame 9 is evenly spaced and installed between the stator inner shell 8 and the stator outer shell 13 along the circumferential direction, and the two end surfaces are close to the inner side surfaces of the stator inner shell 8 and the stator outer shell 13; each stator modulation block 11 is placed at the center of the winding frame middle column 10 along the length direction of each stator winding frame 9. Inside, the stator modulation block 11 adjusts the distribution of the air gap magnetic field to optimize the electromagnetic performance of the motor; each three-phase centralized armature winding 12 is wound on the winding frame center column 10 of its own stator winding frame 9, and each three-phase centralized armature winding 12 is evenly spaced along the circumferential direction. The winding frame center column 10 supports the three-phase centralized armature winding 12 to ensure the neatness and accuracy of the three-phase centralized armature winding 12; the inner rotor 1 and the outer rotor 14 are respectively mounted in the stator inner shell 8 and the stator outer shell 13.

[0027] The three-phase centralized armature winding 12 is arranged according to the operation of three-phase alternating current. Each stator slot of the stator 7 contains two three-phase centralized armature windings 12 and each is independent of three groups, namely, phase A, phase B and phase C. The number of coil turns and resistance of each phase of the three-phase centralized armature winding 12 are equal. The phase difference between two adjacent three-phase centralized armature windings 12 is 120 degrees and they are symmetrically distributed. When the three-phase centralized armature winding 12 is in a rotating magnetic field, a back electromotive force with a phase difference of 120 degrees is induced.

[0028] The inner rotor 1 also includes an inner rotor inner shell 2, an inner rotor iron frame 3, an inner rotor permanent magnet sleeve 5 and an inner rotor outer shell 6. The inner rotor inner shell 2 is sequentially mounted with the inner rotor iron frame 3, the inner rotor permanent magnet sleeve 5 and the inner rotor outer shell 6. The inner rotor permanent magnet sleeve 5 is evenly spaced along the circumferential direction with V-shaped permanent magnet holes. Each V-shaped magnetic concentrating permanent magnet 4 is installed in a respective V-shaped permanent magnet hole. The rotating shaft 20 is coaxially located at the center of the inner rotor inner shell 2, and the V-shaped tip of each V-shaped magnetic concentrating permanent magnet 4 faces the central rotating shaft 20. The inner rotor 1 plays a role of fixed support and protection. The V-shaped magnetic concentrating permanent magnet 4 is in the inner rotor permanent magnet sleeve 5. The V-shaped magnetic concentrating permanent magnet 4 is used to generate a magnetic field to reduce the consumption of electric energy and improve the efficiency of the motor.

[0029] The inner rotor permanent magnet sleeve 5 is made of aluminum material, and the V-shaped magnetic concentrator permanent magnet 4 is made of neodymium iron boron material. The generator uses a V-shaped magnetic concentrator permanent magnet 4 to generate a magnetic field to reduce the consumption of electric energy and improve the efficiency of the motor. The use of the V-shaped magnetic concentrator permanent magnet 4 also helps to reduce the volume and weight of the motor. Compared with other permanent magnet materials such as ferrite, neodymium iron boron material has a higher magnetic energy product, that is, neodymium iron boron permanent magnet material is more suitable for modular motor devices and is conducive to storing magnetic energy. Neodymium iron boron material has a higher coercive force, which enables the embedded permanent magnet material to maintain its magnetic induction intensity under the action of an external magnetic field, so that the power density and stability of the generator are stronger.

[0030] The outer rotor 14 also includes an outer rotor inner shell 15, an outer rotor permanent magnet sleeve 16, an outer rotor iron frame 18 and an outer rotor outer shell 19. The outer rotor inner shell 15 is sequentially mounted with the outer rotor permanent magnet sleeve 16, the outer rotor iron frame 18 and the outer rotor outer shell 19. The outer rotor permanent magnet sleeve 16 is provided with magnetic steel holes evenly spaced along the circumferential direction. Each outer rotor permanent magnet 17 is installed in a respective magnetic steel hole and faces a V-shaped magnetic concentrating permanent magnet 4. Each outer rotor permanent magnet 17 is alternately magnetized radially along the circumferential direction of the air gap of the outer rotor 14. The inner rotor 1 and the outer rotor 14 can be operated simultaneously or separately to generate torque to improve the power density and efficiency of the motor. The outer rotor permanent magnet 17 has a surface clipping structure on one side facing the outer rotor inner shell 15.

[0031] The present invention uses electromagnetic simulation software ANSYS Electronics Desktop to solve the dual-rotor permanent magnet synchronous motor model, and designs the initial generator M1, the intermediate generator M2 and the final generator M3 for design research. Figure 2 (a) Figure 2 (b) and Figure 2 As shown in (c), conventional permanent magnets and permanent magnet steel, V-shaped magnetic concentrator permanent magnet 4 and conventional permanent magnet steel, and V-shaped magnetic concentrator permanent magnet 4 and outer rotor permanent magnet steel 17 with surface clipping structure are respectively used. Through current source excitation, there is a phase difference of 120 degrees (2*pi / 3) between two adjacent three-phase concentrated armature windings 12, which are symmetrically distributed. The loading current of the three-phase concentrated armature winding 12 is set to: Im*sin(position+D / 180*pi), where Im is the loading current source amplitude, position is the position information, and D is the current phase angle, indicating the initial phase of the current. At the same time, a specific harmonic component is injected into the control current of the direct-drive dual-rotor tidal energy permanent magnet generator to improve the performance of the motor, reduce the harmonic current in the motor, thereby reducing the electromagnetic torque pulsation and speed fluctuation, and improving the efficiency and performance of the motor, and a surface clipping structure is used. The radial and tangential air gap harmonics of the initial generator M1 whose outer rotor permanent magnet steel 17 is rectangular are decomposed and their waveforms are analyzed, and the relevant data of each harmonic in the air gap harmonic on the torque and torque pulsation are calculated and the harmonics that can be set are selected, such as Figure 3 As shown, the harmonics that generate the main torque pulsation in the motor are the fundamental wave, the third harmonic and the fifth harmonic, and the fundamental wave is also the main harmonic that generates torque. Harmonics are injected into the surface of the rectangular outer rotor permanent magnet steel 17, and the outer rotor permanent magnet steel 17 is changed to the curve represented by the pole clipping function. The weight of each of the three harmonics in the sum of the amplitudes of the three harmonics is calculated as the initial value of k1, k2 and k3, and the parameters of the intermediate generator M2 topology are screened. The objective function is defined as a function of air gap harmonics, and the constraints are the harmonic injection ratio in the pole clipping function, the V-shaped magnetic concentrator permanent magnet 4, the length and width of the outer rotor permanent magnet steel 17, and the position of the outer rotor permanent magnet steel 17. The sensitivity of the harmonic injection ratio in the pole clipping function and the position of the outer rotor permanent magnet steel 17 to the function is calculated, and the sensitivity of each parameter to each harmonic is calculated and three sets are screened. The harmonic injection ratio and the length and width of the stator modulation block 11 are analyzed for sensitivity to the objective function.

[0032] On the basis of the initial generator M1, after the permanent magnets and permanent magnet steels are both subjected to the surface pole clipping function, the inner rotor 1 is subjected to the square permanent magnet function, and the outer rotor 4 is subjected to the surface shaping function. On the basis of the intermediate generator M2, a stator modulation block 11 is placed in the winding frame center column 10 of the stator winding frame 9, which will form a modulation pole in the stator 7. Each stator modulation block 11 is rectangular, with a length of l1 and a width of h1, which will respectively affect the peak height and waveform width of each order of the modulated magnetic permeability. Due to the introduction of the stator modulation block 11, the stator magnetic permeability is changed, and the change in the stator magnetic permeability will change the modulation behavior of the permanent magnetic field and then change the air gap harmonics, so that the harmonic change can be achieved in a targeted manner, and the final generator M3 is formed on this basis. Figure 4 As shown, due to the introduction of the stator modulation flux permeance, the harmonic order and amplitude in the air gap will be changed. Then, according to the modulation mechanism of the magnetic field modulation motor, the harmonics injected by the rotor permanent magnet will also be modulated. Therefore, changing the injection ratio of each harmonic in the permanent magnet pole-cutting function will change the air gap magnetic density harmonics. Changing the length and width of the stator modulation block 11 will also change the air gap magnetic density harmonics. The overall design process and performance comparison of the initial generator M1, the intermediate generator M2 and the final generator M3 are shown in Figure 1. Figure 4 and Figure 5 As shown in Figure 2, after two-step multi-modulation design, the generator M3 can finally obtain higher no-load induced electromotive force and load torque, as well as smaller torque pulsation. Figure 7 and Figure 8 As shown, before and after the motor design, the motor air gap still has the highest proportion of the air gap magnetic flux with 18 permanent magnet pole pairs as the fundamental wave. However, due to the introduction of the stator modulation block 11, a harmonic component with 9 pole pairs as the fundamental wave of the winding pole pairs is generated in the motor. In addition, after the introduction and optimization design of the V-type magnetic concentrating permanent magnet 4 pole clipping and the stator modulation block 11, the third and fifth harmonics that generate torque pulsation in the internal and external air gap magnetic flux are weakened to a certain extent, especially the amplitude of the fifth harmonic is greatly reduced. In addition, the increase of the fundamental wave brings about an increase in the load torque, and since the modulation of the stator modulation block participates in the asynchronous modulation of the permanent magnet magnetic field, rich working harmonics are generated. Although some harmonics will also generate torque pulsation, the positive impact they bring is greater than the negative impact.

[0033] The V-shaped magnetic concentrating permanent magnet 4 structure in the permanent magnet synchronous motor generates a rotating magnetic field in the three-phase centralized armature winding 12. The rotating magnetic field of the dual-rotor structure interacts with the three-phase centralized armature winding 12 on the motor disk. According to Faraday's law of electromagnetic induction, an electromotive force that resists the trend of current change will be generated in the three-phase centralized armature winding 12. The line back electromotive force is the induced electromotive force generated by the coil between any two phases in the three-phase synchronous motor. Both reflect the operating characteristics and energy conversion efficiency of the motor. Through finite element simulation, the no-load back electromotive force and load induced electromotive force of the motor are solved, and relevant data are obtained through simulation. The overall waveform of the graph is close to a triangular sine distribution. From its waveform, it can be seen that the established direct-drive dual-rotor tidal current generation model basically meets the design operating conditions. At the same time, the load torque and no-load reaction electromotive force designed by the present invention are solved and compared, and both can meet the relevant standards recommended for motor design, such as Figure 6 As shown, the final generator M3 has a no-load induced electromotive force with a very high sinusoidality. The motor adopts a single-stator single-winding dual-rotor design structure. Therefore, the induced electromotive force on the stator winding is generated by the combined action of the inner rotor air gap permanent magnetic flux density and the outer rotor air gap permanent magnetic flux density. However, due to the radial alternating magnetization adopted by the inner and outer rotors 1 and 4, there will be a magnetic potential offset in the radial permanent magnetic potential. The no-load induced electromotive force on the three-phase centralized armature winding 12 is equivalent to the superposition of the two no-load induced electromotive forces generated by the inner and outer rotors 1 and 4 respectively.

[0034] The present invention adopts the design method of the inner and outer air gap double-layer rotor to improve the utilization rate of the outer rotor permanent magnet steel 17, that is, to improve the energy conversion efficiency, meet the needs of tidal energy power generation, and eliminate the transmission system, such as the speed change gear box, etc. The structure of the motor is simpler, and the mechanical loss and maintenance cost are reduced. In addition, the inner and outer surfaces of the inner and outer rotor permanent magnet steel 17 of the generator are subjected to harmonic injection design to optimize the magnetic field distribution inside the motor, reduce energy loss, and thus improve the energy conversion efficiency of the motor. The harmonic injection design reduces the torque pulsation in the motor, making the motor run more smoothly and improving the stability of the output torque. At the same time, it helps to improve the power density of the motor, so that the motor can provide more output power in a smaller volume, which is very beneficial for applications with limited space.

[0035] The present invention improves the applicability and reliability of the direct-driven tidal current energy generator, simplifies the spatial structure of the device, reduces the number of parts, reduces maintenance costs, and improves the efficiency of the direct-driven tidal current energy generator.

Claims

1. A direct-drive dual-rotor tidal current permanent magnet generator, characterized in that: The invention comprises an inner rotor (1), a stator (7), an outer rotor (14), a rotating shaft (20) and a chassis (21); the inner rotor (1), the stator (7) and the outer rotor (14) are coaxially mounted from the inside to the outside and the ends are mounted on the chassis (21); the rotating shaft (20) is coaxially mounted in the center of the inner rotor (1) and welded to the center of the chassis (21); a plurality of V-shaped magnetic concentrating permanent magnets (4) for generating a magnetic field and reducing energy consumption are evenly spaced in the circumferential direction in the inner rotor (1); a plurality of stator winding frames (9) are evenly spaced in the circumferential direction in the stator (7); a stator modulation block (11) for adjusting the air gap magnetic field distribution is mounted in each stator winding frame (9); a plurality of outer rotor permanent magnets (17) with surface pole clipping structures are evenly spaced in the circumferential direction in the outer rotor (14).

2. The direct-drive dual-rotor tidal current permanent magnet generator according to claim 1, characterized in that: The stator (7) further comprises a stator inner shell (8), a plurality of stator winding frames (9), a plurality of three-phase concentrated armature windings (12) and a stator outer shell (13); the stator winding frame (9) is in an I-shape and has arc-shaped sides; each stator winding frame (9) is evenly spaced along the circumferential direction and installed between the stator inner shell (8) and the stator outer shell (13) and has its two end surfaces close to the inner side surfaces of the stator inner shell (8) and the stator outer shell (13); each stator modulation block (11) is arranged along The length direction of the winding frame center column (10) of each stator winding frame (9) is placed in the center of the winding frame center column (10), each three-phase concentrated armature winding (12) is wound on the winding frame center column (10) of each stator winding frame (9), and each three-phase concentrated armature winding (12) is evenly spaced along the circumferential direction; the inner rotor (1) and the outer rotor (14) are respectively mounted inside the stator inner shell (8) and outside the stator outer shell (13).

3. The direct-drive dual-rotor tidal current permanent magnet generator according to claim 2 is characterized in that: The three-phase concentrated armature winding (12) is arranged according to the operation of three-phase alternating current. Each stator slot of the stator (7) contains two three-phase concentrated armature windings (12) and each of the three-phase concentrated armature windings (12) is independent. The number of coil turns and resistance of each phase of the three-phase concentrated armature winding (12) are equal. The phase difference between two adjacent three-phase concentrated armature windings (12) is 120 degrees and they are symmetrically distributed. When the three-phase concentrated armature winding (12) is in a rotating magnetic field, a back electromotive force with a phase difference of 120 degrees is induced.

4. The direct-drive dual-rotor tidal current permanent magnet generator according to claim 2, characterized in that: The inner rotor (1) further comprises an inner rotor inner shell (2), an inner rotor iron frame (3), an inner rotor permanent magnet sleeve (5) and an inner rotor outer shell (6); the inner rotor iron frame (3), the inner rotor permanent magnet sleeve (5) and the inner rotor outer shell (6) are sequentially mounted on the inner rotor inner shell (2); V-shaped permanent magnet channels are evenly spaced along the circumferential direction on the inner rotor permanent magnet sleeve (5); each V-shaped magnetic concentrating permanent magnet (4) is installed in a respective V-shaped permanent magnet channel; the rotating shaft (20) is coaxially located at the center of the inner rotor inner shell (2); and the V-shaped tip of each V-shaped magnetic concentrating permanent magnet (4) faces the central rotating shaft (20).

5. The direct-drive dual-rotor tidal current permanent magnet generator according to claim 4 is characterized in that: The inner rotor permanent magnet sleeve (5) is made of aluminum material, and the V-shaped magnetic field-concentrating permanent magnet (4) is made of neodymium iron boron material.

6. The direct-drive dual-rotor tidal current permanent magnet generator according to claim 2, characterized in that: The outer rotor (14) further comprises an outer rotor inner shell (15), an outer rotor permanent magnet sleeve (16), an outer rotor iron frame (18) and an outer rotor outer shell (19); the outer rotor inner shell (15) is sequentially mounted with the outer rotor permanent magnet sleeve (16), the outer rotor iron frame (18) and the outer rotor outer shell (19); the outer rotor permanent magnet sleeve (16) is provided with magnetic steel holes evenly spaced in the circumferential direction; each outer rotor permanent magnet (17) is installed in a respective magnetic steel hole and faces a V-shaped magnetic concentrating permanent magnet (4); each outer rotor permanent magnet (17) is radially alternately magnetized along the circumferential direction of the air gap of the outer rotor (14).

7. The direct-drive dual-rotor tidal current energy permanent magnet generator according to claim 6, characterized in that: The surface of the outer rotor permanent magnet steel (17) on one side facing the outer rotor inner shell (15) adopts a surface clipping structure.

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