Hybrid excitation bearingless permanent magnet synchronous generator

Abstract

The invention discloses a hybrid excitation bearingless permanent magnet synchronous generator in the field of flywheel energy storage systems, which is characterized in that a stator core is coaxially sleeved outside a rotor fastener, two pairs of pole permanent magnets are radially magnetized and are surface-mounted on the rotor fastener, 36 stator slots are uniformly formed in the stator core along the circumferential direction, an inner winding and an outer winding are mounted in each stator slot, and the rotor fastener and the rotor fastener are fastened by a fastening bolt. The outer-layer winding is a power generation winding with three slots per pole per phase, every three slots are a wire inlet end or a wire outlet end of one phase, the inner-layer winding is a suspension force / excitation winding and is of a double-three-phase single-winding structure, and three adjacent slots are a wire inlet end or a wire outlet end of one phase; stable suspension and air-gap magnetic field adjustment can be realized only by introducing and changing suspension force current and excitation current into the two three-phase winding units at the same time, the defect that double windings occupy the limited space of a stator slot is overcome, the motor structure is further simplified, suspension force and excitation compensation are effectively utilized, and the service life of the motor is prolonged. And the reliability and the stability of the operation of the motor under different working conditions are improved.

Description

Technical Field

[0001] The invention belongs to the field of flywheel energy storage systems, specifically the permanent magnet synchronous generator and the bearingless motor therein, and particularly relates to a hybrid-excitation bearingless permanent magnet synchronous generator. Background Art

[0002] Flywheel energy storage has the advantages of high energy density, high power density, long cycle life, etc., and is very suitable for application scenarios such as electric vehicles, new energy grid frequency modulation, aerospace, etc. In a flywheel energy storage system, the mutual conversion between electrical energy and mechanical energy is realized by an electric / generator. Therefore, as the core functional component of the system, the motor directly affects the efficiency and reliability of the entire energy storage system. Due to the limitation of single excitation by permanent magnets in an ordinary permanent magnet synchronous motor, there is a defect that the air-gap magnetic field is difficult to adjust under the working condition of load change, resulting in poor dynamic response, low output efficiency, and affecting the stability of the power system. At the same time, under the high-speed operation state, the mechanical bearing part generates serious heat due to friction, and the viscosity of the lubricant increases, increasing the maintenance cost of the motor and shortening the service life of the motor. Therefore, a hybrid-excitation bearingless permanent magnet synchronous generator is proposed to address the above problems.

[0003] A document with the Chinese patent publication number CN207896846U discloses a structure of a bearingless permanent magnet synchronous motor. In this motor, the permanent magnets are located in the stator yoke, and the winding consists of a set of concentrated armature windings and a set of concentrated suspension windings, which are distributed on the teeth of the stator core, improving the air-gap magnetic density and the heat dissipation performance of the motor. However, the problems it has are as follows: Due to the disadvantage of only single excitation by permanent magnets inside the motor, there is a problem that the air-gap magnetic field is difficult to adjust under the condition of load change, seriously affecting the output power of the motor.

[0004] A document with the Chinese patent publication number CN105656269A discloses a bearingless permanent magnet synchronous generator. Since an excitation winding is added to the original suspension force winding, it can compensate or weaken the changing synthetic magnetic field under different working conditions of the motor to achieve stable operation. However, the problems it has are as follows: The excitation winding therein occupies the slot space that originally belongs to the suspension force winding, increasing the control difficulty and cost of the motor, reducing its dynamic performance. When the motor is operating normally, the density of the suspension force current is small, and the suspension force winding cannot be fully utilized, which will inevitably reduce the working efficiency of the motor. Summary of the Invention

[0005] In order to improve the above-mentioned deficiencies existing in the existing generators, the present invention proposes a hybrid-excitation bearingless permanent magnet synchronous generator, which can achieve better deep weak magnetic control, suspension performance, and power generation power under different working conditions.

[0006] The technical solution adopted by a hybrid-excitation bearingless permanent magnet synchronous generator of the present invention is as follows: It includes a rotor fastener and a stator core. The stator core is coaxially sleeved outside the rotor fastener. Two-pole permanent magnets are radially magnetized and surface-mounted on the rotor fastener. The stator core is evenly provided with 36 stator slots along the circumferential direction. Two sets of windings, an inner set and an outer set, are installed in each stator slot, adopting a distributed double-layer winding arrangement. The outer-layer winding is a power generation winding with 3 slots per pole per phase. Every three slots are the incoming or outgoing ends of one phase. The power generation winding has two poles and is arranged in the counterclockwise direction as GA1+, GB1-, GC1+, GA1-, GB1+, GC1-, GA2+, GB2-, GC2+, GA2-, GB2+, GC2-. The inner-layer winding is a suspension force / excitation winding, which is a double-three-phase single-winding structure. The incoming or outgoing ends of one phase are three adjacent slots. In the double-three-phase single-winding structure, the three phases A, B, and C of the first set of windings are spaced at a spatial angle of 2π / 3 from each other, and the three phases U, V, and W of the second set of windings are spaced at a spatial angle of 2π / 3 from each other. The corresponding phases A and U, B and V, C and W are mirror-symmetric in space.

[0007] Further, the wiring of the power generation winding is to feed in from the A1+ side, draw out from the adjacent A1- side, then wind around to feed in from the A2+ side, and draw out from the A2- side. The wiring principles of the B phase and the C phase are the same as that of the A phase. Then, A1+, B1+, and C1+ are connected together as the neutral point of the power generation winding, while the A2-, B2-, and C2- phases are respectively connected to the A, B, and C arms of a three-phase PWM rectifier bridge. The current induced by the generator flows into the PWM rectifier bridge from the neutral point of the power generation winding.

[0008] Further, for the suspension force / excitation winding, the windings of every three stator slots are the incoming or outgoing ends of one phase. The windings are arranged in the counterclockwise direction as A+, W-, V+, A-, C+, V-, U+, C-, B+, U-, W+, B-.

[0009] Further, the suspension force current and the excitation current are respectively controlled by one inverter. Each inverter is connected to a three-phase winding unit, and the currents of the two inverters are adjusted to generate the suspension force and the excitation.

[0010] The advantages of the present invention after adopting the above technical solution are as follows:

[0011] 1. There are two layers of windings, an inner layer and an outer layer, in the stator slots of the present invention. The inner-layer winding is optimized from the traditional double-winding structure of a bearingless motor to a single winding, solving the drawback that the double windings occupy the limited space of the stator slots, further simplifying the motor structure, making it more compact, reducing the difficulty of the stator structure design and manufacturing process of the motor, and effectively utilizing both the suspension force and the excitation compensation, thereby improving the reliability and stability of the motor operation under different working conditions.

[0012] 2. In the present invention, since the number of pole pairs of the permanent magnet is different from that of the equivalent winding of the suspension force, when the rotor is not eccentric, the changing magnetic field generated by the permanent magnet does not generate an induced current in the suspension force / excitation winding. Therefore, the generation of the suspension force and the power generation control of this hybrid-excitation bearingless permanent magnet synchronous generator do not interfere with each other.

[0013] 3. The suspension / excitation winding in the present invention makes full use of the inner winding structure. There are two independent three-phase winding units in the form of distributed windings embedded in the stator slots of the motor. By simply passing and changing the suspension force current and the excitation current simultaneously in the two three-phase winding units through an external drive controller, stable suspension and air-gap magnetic field regulation can be achieved. Description of the Drawings

[0014] Figure 1 It is a schematic axial sectional view of a hybrid-excitation bearingless permanent magnet synchronous generator of the present invention;

[0015] Figure 2 It is a schematic radial sectional view of a hybrid-excitation bearingless permanent magnet synchronous generator of the present invention;

[0016] Figure 3 It is a schematic diagram of the winding method of the stator winding of the present invention;

[0017] Figure 4 It is a topological structure diagram of the suspension force / excitation current of the present invention;

[0018] Figure 5 is Figure 3 a schematic connection diagram of the external circuit of the suspension force / excitation winding in;

[0019] Figure 6 is Figure 3 a schematic connection diagram of the external circuit of the power generation winding in;

[0020] Figure 7 It is a schematic diagram of the principle of generating the radial suspension force in the x direction and the magnetic field spatial distribution structure during the operation of the present invention;

[0021] Figure 8 It is a schematic diagram of the principle of generating the radial suspension force in the y direction and the magnetic field spatial distribution structure during the operation of the present invention;

[0022] Figure 9 It is a schematic diagram of the principle of generating the excitation and the magnetic field spatial distribution structure during the operation of the present invention. The magnetic field of the excitation equivalent winding is in the same direction as the synthetic magnetic field, and the magnetic field of the excitation current equivalent will compensate for the synthetic magnetic field;

[0023] Figure 10 It is a schematic diagram of the principle of generating the excitation and the magnetic field spatial distribution structure during the operation of the present invention. The magnetic field of the excitation current equivalent winding is in the opposite direction to the synthetic magnetic field, and the magnetic field of the excitation current equivalent will weaken the synthetic magnetic field.

[0024] In the figure: 1 - housing; 2 - rotor fastener; 3 - radially magnetized surface-mounted permanent magnet; 4 - stator core; 5 - generating winding; 6 - suspension force / excitation winding; 7 - front end cover; 8 - radial displacement sensor; 9 - self-aligning ball bearing; 10 - rotating shaft; 11 - photoelectric encoder; 12 - reference ring; 13 - auxiliary bearing for the rotating shaft; 14 - axial displacement sensor; 15 - rear end cover. Specific embodiments

[0025] The hybrid-excitation bearingless permanent magnet synchronous generator of the present invention will be further described below in conjunction with the accompanying drawings.

[0026] See Figure 1 , a hybrid-excitation bearingless permanent magnet synchronous generator of the present invention includes a housing 1, a rotor fastener 2, two-pole surface-mounted permanent magnets 3, a stator core 4, a generating winding 5 and a suspension force / excitation winding 6. A front end cover 7 is provided at the front end of the housing 1, and a rear end cover 15 is provided at the rear end. The housing 1 is fixedly connected to the front end cover 7 and the rear end cover 15 by screws; the rotating shaft 10 is coaxially connected to the housing 1. The housing 1 is used to stabilize the stator core of the generator and the front and rear end covers. The rotating shaft 10 extends out of the front end cover 7 and is connected to the photoelectric encoder 11; a rotor fastener 2 and a stator core 4 are provided inside the housing 1. The two-pole permanent magnets 3 are radially magnetized and surface-mounted on the rotor fastener 2. The rotor fastener 2 fixedly connects the permanent magnets 3 and the rotating shaft 10 to form a permanent magnet rotor. The stator core 4 is fixed on the inner wall of the housing 1. The permanent magnet rotor is coaxially sleeved outside the rotating shaft 10, and the stator core 4 is coaxially sleeved outside the permanent magnet rotor, belonging to an outer stator and inner rotor structure. Both the stator core 4 and the rotor are laminated from silicon steel sheets, and the rotating shaft 10 is made of a non-magnetic material. There is a radial air gap between the stator core 4 and the permanent magnet rotor. The air gap width is related to the power rating of the motor, the selected permanent magnet material, and the processing and assembly processes of the stator and rotor. Auxiliary bearings 13 and self-aligning ball bearings 9 are respectively installed and fixed at both ends of the rotating shaft 10. The self-aligning ball bearing 9 axially fixes one end of the rotating shaft 10 and allows it to move flexibly in two degrees of freedom in the radial direction. The auxiliary bearing 13 is used for supporting the motor in the non-working state. A photoelectric encoder 11 is installed on the rotating shaft 10 outside the front end cover 7 on one side of the self-aligning ball bearing 9 to detect the motor speed. A reference ring 12 is installed on the rotating shaft 10. The reference ring 12 is coaxially and fixedly sleeved on the rotating shaft 10. There are a total of 4 radial displacement sensors 8 in the spaces at the left and right ends of the stator core 4 inside the housing 1 to detect the radial displacement of the motor rotor. Both the stator core 4 and the rotor are laminated from silicon steel sheets with a thickness of 0.35 mm, and the lamination coefficient is 0.95. The rotating shaft 10 is composed of a non-magnetic material.

[0027] There are two sets of windings inside the stator core 4 in the housing 1. The outer layer winding is the generating winding 5 for induction power generation, and the inner layer winding is the suspension force / excitation winding 6 for generating radial suspension force and excitation compensation.

[0028] See Figure 2 , on the rotor fastener 2 of the hybrid-excited bearingless permanent magnet synchronous generator, four radially magnetized permanent magnets 3 are evenly surface-mounted, and the permanent magnets 3 are distributed in two pairs of poles. Along the circumferential direction of the stator core 4, 36 stator slots are evenly opened, and two sets of inner and outer windings are installed in each stator slot, adopting a distributed double-layer winding arrangement. The outer winding is a power generation winding 5 with 3 slots per pole per phase, arranged in the counterclockwise direction as GA1+, GB1-, GC1+, GA1-, GB1+, GC1-, GA2+, GB2-, GC2+, GA2-, GB2+, GC2-, with every three slots being the incoming or outgoing end of one phase. The power generation winding 5 has two pairs of poles, the same as the pole pairs of the permanent magnets 3. The inner winding is the suspension force / excitation winding 6, which is a double-three-phase single-winding structure, sharing the same slot with the outer power generation winding, and is controlled by two three-phase inverter circuits. Among them, the first set of three-phase windings consists of three phases A, B, and C, and the second set consists of three phases U, V, and W. The adjacent three slots are the incoming or outgoing end of one phase. In the first set of windings, the three phases A, B, and C are spaced at a spatial angle of 2π / 3 from each other, and in the second set of windings, the three phases U, V, and W are spaced at a spatial angle of 2π / 3 from each other. In the stator mechanical space, the corresponding phases A and U, B and V, C and W are mirror-image distributed in space.

[0029] See Figure 3 , the schematic diagram of the stator winding winding expansion of the hybrid-excited bearingless permanent magnet synchronous generator. Taking the power generation winding 5 as an example of phase A, the windings of every three stator slots are the incoming or outgoing end of one phase, and the windings are arranged in the counterclockwise direction as GB1-, GC1+, GA1-, GB1+, GC1-, GA2+, GB2-, GC2+, GA2-, GB2+, GC2-. The wiring of phase A is to enter from the A1+ side, exit from the adjacent A1- side, then wind to the A2+ side to enter, and exit from the A2- side. The wiring principles of phase B and phase C are the same as that of phase A. Then, A1+, B1+, and C1+ are connected together as the neutral point of the power generation winding 5, and phases A2-, B2-, and C2- are respectively connected to Figure 6 the three bridge arms A, B, and C of the three-phase PWM rectifier shown in. The current induced by the generator flows into the PWM rectifier from the neutral point of the power generation winding 5 to supply power to the load.

[0030] The suspension force / excitation winding 6 is distributed corresponding to the power generation winding slots. The windings of every three stator slots are the incoming or outgoing end of one phase, and the windings are arranged in the counterclockwise direction as A+, W-, V+, A-, C+, V-, U+, C-, B+, U-, W+, B-. Taking the three phases A, B, and C as an example, it needs to be connected as shown in Figure 5In the first inverter shown, power is input from the A+ side and output from the A- side. The wiring principles of phases B and C are the same as that of phase A. At the same time, the A-, B-, and C- sides are connected together as the neutral point of the first inverter. U, V, and W need to be connected as shown in Figure 5 In the second inverter shown, power is input from the U+ side and output from the U- side. The wiring principles of phases V and W are the same as that of phase U. At the same time, the U-, V-, and W- sides are connected together as the neutral point of the second inverter.

[0031] See Figure 4 , the topology diagram of the suspension force / excitation current input to the hybrid-excitation bearingless permanent magnet synchronous generator. In the Figure 2 shown radial cross-section of the motor, the positive of each phase (such as A+) indicates that the current flows in from the input end, and the negative of each phase (such as A-) indicates that the current flows out from the output end. The suspension force current and the excitation current are each controlled by a three-phase inverter, for a total of two three-phase inverters, and each three-phase inverter is connected to a three-phase winding unit. For the motor to operate normally and stably, the excitation current output by the controller has the following characteristics: ① The phase difference between the currents of adjacent phase windings in each group of three-phase winding units is 2π / 3, ② The phases of the corresponding phases in the two winding units are the same. The characteristics of the output suspension force current are: ① The phase difference between the currents of adjacent phase windings in each group of three-phase winding units is 2π / 3, ② The phases of the corresponding phases in the two three-phase winding units are opposite. To meet the other two necessary suspension conditions for the bearingless motor: ① The current frequencies of the windings are the same, ② The rotation directions of the two magnetic fields are the same. Let ω be the electrical angular frequency; t represent time; i SA , i SB , i SC , i SU , i SV , i SW respectively represent the suspension force currents of phases A, B, C, U, V, and W of the suspension force / excitation winding; I s represents the amplitude of the suspension force current per phase; i EA , i EB , i EC , i EU , i EV , i EW respectively represent the excitation currents of phases A, B, C, U, V, and W of the suspension force / excitation winding; I e represents the amplitude of the excitation current per phase. By controlling the inverter, a superimposed current combination of the corresponding phases is output. The currents finally input to phases A, B, C, U, V, and W are i SA + i EA , i SB + i EB , i SC + i EC , i SU + iEU 、 i SV + i EV 、 i SW + i EW 。 Among them, the current equations of each phase winding of the two inverters are as follows, Equation (1) is:

[0032]

[0033] See Figure 5 , the schematic diagram of the external circuit of the suspension force / excitation winding. It is composed of the first inverter and the second inverter. V1, V2, V3, V4, V5, and V6 in the two inverters are controllable switch tubes, VD1, VD2, VD3, VD4, VD5, and VD6 are freewheeling diodes, and U d is the bus voltage. In the circuit, the A, B, and C bridge arms are respectively connected to the A, B, and C phases in the suspension force / excitation winding, and the U, V, and W bridge arms are respectively connected to the U, V, and W phases in the suspension force / excitation winding. By adjusting the currents of the two inverter circuits, it can be used to generate suspension force and excitation.

[0034] See Figure 6 , the schematic diagram of the external circuit of the power generation winding. It is mainly composed of a PWM rectifier bridge. Among them, C represents a capacitor, R represents an inductor, Z represents an impedance, and V represents a circuit breaker. In the three-phase rectifier bridge, the GA, GB, and GC bridge arms are respectively connected to the GA, GB, and GC phases in the power generation winding. The power generation principle of the present invention is the same as that of an ordinary permanent magnet synchronous generator. The prime mover and the hybrid excitation bearingless permanent magnet synchronous generator of the present invention are coaxially connected. Driven by the prime mover, the rotor rotates to generate a changing magnetic induction field, and the power generation winding cuts the magnetic induction lines to generate three-phase induced current, which flows into the PWM rectifier bridge 6 from the neutral point and is output to the load for electrical energy storage.

[0035] See Figure 7 and Figure 8 , when the present invention enters no-load operation, the schematic diagram of the radial suspension force generated by the inner layer winding of the motor. During operation, the centering operation of the rotor is to adjust the given suspension force current signal by detecting the feedback signal of the radial displacement of the rotor. The generator rotates driven by the prime mover, and its air-gap magnetic field is composed of the superposition of the magnetic fields of the permanent magnet, the suspension force / excitation winding, and the power generation winding. Among them, it is assumed that the equivalent magnetic field of the permanent magnet and the equivalent magnetic field of the excitation current are generated by the excitation winding N t with the number of pole pairs P t = 2, the equivalent magnetic field of the suspension force is generated by the suspension force winding N s and the number of pole pairs P s = 1, satisfying one of the necessary suspension conditions for a bearingless motor: P t = P s ± 1. The interaction of the two kinds of pole-pair magnetic fields generates tangential Lorentz force and radial Lorentz force. As Figure 7As shown, when currents are injected into two equivalent windings as Figure 4 shown, assuming the exciting current equivalent winding N t and the levitation force current equivalent winding N s , according to the superposition principle, the exciting magnetic field Ψ t and the levitation force magnetic field Ψ s are respectively generated by the two equivalent windings. The interaction of the two magnetic fields makes the magnetic density in the air-gap 1-1 region increase, the magnetic density in the air-gap 3-1 region decrease, while the magnetic density changes in the air-gaps 2-1 and 4-1 are small. The asymmetric air-gap magnetic fluxes on both sides cause a single-direction radial levitation force F x to be generated on the motor rotor, and the direction points to the region where the magnetic field intensity increases (the positive x-axis direction). As Figure 8 shown, similarly, the interaction of the two magnetic fields makes the magnetic density in the air-gap 2 region increase and the magnetic density in the air-gap 4-1 region decrease. The Maxwell force received by the air-gap 2-1 is greater than that of the air-gap 4, so the resultant force generated is upward, that is, the radial levitation force generated on the motor rotor surface is in the direction of F y . It can be seen from this that when the current in N t is kept stable, by only controlling the magnitude and direction of the levitation force current in N s , a controllable levitation force can be generated.

[0036] See Figure 9 and Figure 10 , which are schematic diagrams of the exciting principle of the present invention. When Figure 4 only the exciting current i E is fed into the two inverters in t , the exciting current equivalent winding N Figure 9 has 2 pole pairs, and the generated exciting magnetic field divides the generator into four equal parts in space as the power generation winding 5. As g shown, when the combined magnetic field of the power generation winding N t and the levitation force winding weakens, the magnetic field Ψ t of the exciting equivalent winding N g is in the same direction as the combined magnetic field Ψ g and the exciting current equivalent magnetic field will compensate for the combined magnetic field. As shown in 10, when the combined magnetic field of the power generation winding N t and the levitation force current equivalent winding weakens, the magnetic field Ψ t of the exciting current equivalent winding N g is in the opposite direction to the combined magnetic field Ψ E and the exciting current equivalent magnetic field will weaken the combined magnetic field. Therefore, by detecting the angular position of the motor rotor and the given speed of the prime mover, only the exciting current i E fed into the levitation force / exciting winding 6 needs to be adjusted.It can stabilize the synthetic magnetic field inside the generator. By effectively combining electric excitation and permanent magnet excitation to form hybrid excitation, it has certain improvements and advantages in stabilizing the magnetic field inside the generator, enhancing the suspension performance and power generation quality of the bearingless generator of this invention.

[0037] For the hybrid excitation bearingless permanent magnet synchronous generator of this invention, structurally, since the inner layer winding optimizes the suspension force and excitation into a single winding structure, the motor structure is more compact, greatly reducing the difficulty of the motor stator structure design and manufacturing process. Not only is the suspension force effectively utilized, but also electric excitation and permanent magnet excitation form hybrid excitation, which improves the reliability and stability of the generator under different operating conditions by compensating or weakening the synthetic magnetic field.

Claims

1. A hybrid excitation bearingless permanent magnet synchronous generator, comprising a rotor fastener and a stator core, wherein the stator core is coaxially sleeved outside the rotor fastener, and two pairs of permanent magnets are radially magnetized and attached to the rotor fastener, characterized in that: The stator core is evenly opened with 36 stator slots along the circumferential direction. Two sets of inner and outer windings are installed in each stator slot, and a distributed double-layer winding arrangement is adopted; the outer winding is a power generation winding with 3 slots per pole and per phase, and every three slots are the incoming or outgoing terminals of one phase. The power generation winding is two pairs of poles, and the counterclockwise direction is GA1+, GB1-, GC1+, GA1-, GB1+, GC1-, GA2+, GB2-, GC2+, GA2-, G B2+ and GC2- are arranged in phase; the inner winding is the suspension force / excitation winding, which is a double three-phase single winding structure, and the three adjacent slots are the incoming or outgoing terminals of one phase. The A, B, and C phases of the first group of windings in the double three-phase single winding structure are spaced apart at a spatial angle of 2π / 3, and the U, V, and W phases of the second group of windings are spaced apart at a spatial angle of 2π / 3. The corresponding phases A phase and U phase, B phase and V phase, and C phase and W phase are mirror-distributed in space.

2. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 1, characterized in that: The connection of the generating winding is that the line enters from the A1+ side, exits from the adjacent A1- side, and then is wound to the A2+ side and enters from the A2- side. The connection principle of phase B and phase C is the same as that of phase A. Then the A1+, B1+, and C1+ phases are connected together as the neutral point of the generating winding, and the A2-, B2-, and C2- phases are respectively connected to the A, B, and C arms of the three-phase PWM rectifier bridge. The current induced by the generator flows from the neutral point of the generating winding into the PWM rectifier bridge.

3. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 1, characterized in that: The windings of every three stator slots of the suspension force / excitation winding are the incoming or outgoing ends of the phase, and the windings are arranged in a counterclockwise direction as A+, W-, V+, A-, C+, V-, U+, C-, B+, U-, W+, and B- phases.

4. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 1, characterized in that: The suspension force current and the excitation current are controlled by an inverter respectively. Each inverter is connected to a three-phase winding unit. The currents of the two inverters are adjusted to generate suspension force and excitation.

5. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 4, characterized in that: The first inverter has incoming wires from the A+ side and outgoing wires from the A- side. The wiring principle of the B and C phases is the same as that of the A phase. The A-, B-, and C- sides are connected together as the neutral point of the first inverter. U, V, and W are connected to the second inverter, with the line entering from the U+ side and the line exiting from the U- side. The wiring principle of V and W phases is the same as that of U phase. The U-, V-, and W- sides are connected together as the neutral point of the second inverter.

6. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 5, characterized in that: The phases of the winding currents of adjacent phases in each group of three-phase winding units of the excitation winding differ by 2π / 3, and the phases of the corresponding phases in the two groups of winding units are the same.

7. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 5, characterized in that: The phases of the adjacent phase winding currents in each three-phase winding unit of the suspension force winding differ by 2π / 3, and the phases of the corresponding phases of the windings in the two three-phase winding units are opposite.

8. A hybrid excitation bearingless permanent magnet synchronous generator according to claim 6 or 7, characterized in that: The current frequencies of the suspension force / excitation windings are consistent, and the rotation directions of the two magnetic fields are consistent.

9. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 1, characterized in that: The final currents flowing into phases A, B, C, U, V, and W are i SA +i EA 、i SB +i EB 、i SC +i EC 、i SU +i EU 、i SV +i EV 、i SW +i EW , where i SA 、i SB 、i SC 、i SU 、i SV 、i SW are the A-phase, B-phase, C-phase, U-phase, V-phase and W-phase suspension force currents of the suspension force / excitation winding respectively; I s is the current amplitude of the suspension force of each phase; i EA 、i EB 、i EC 、i EU 、i EV 、i EW They are the A-phase, B-phase, C-phase, U-phase, V-phase and W-phase excitation currents of the suspension force / excitation winding respectively.

10. The hybrid excitation bearingless permanent magnet synchronous generator according to claim 9, characterized in that: The current of each phase winding of the two inverters is: ω is the electrical angular frequency and t is the time.

Images