Novel bearingless permanent magnet synchronous motor and control method thereof

Abstract

The invention discloses a novel bearingless permanent magnet synchronous motor and a control method thereof, the novel bearingless permanent magnet synchronous motor comprises a stator iron core, windings, permanent magnets, a rotor iron core and a rotating shaft, the four permanent magnets are attached to the surface of the rotor iron core to form a quadrupole air-gap magnetic field, the rotor iron core is fixed on the rotating shaft, 24 grooves are formed in the stator iron core, the grooves are divided into three layers, a three-phase quadrupole torque winding is embedded in the outermost layer, and the three-phase quadrupole torque winding is embedded in the outer layer. A three-phase suspension winding is embedded in the middle layer and the inner layer, and the torque winding and the suspension winding are driven by two three-phase inverters respectively. A displacement sensor is mounted on a stator; radial displacement of the rotor is detected; a displacement and rotating speed closed-loop control system is established; meanwhile, amplitudes and phases of currents of a torque winding and a suspension winding are controlled; compared with the prior art, the rotor suspension device has the advantages of being good in rotor suspension dynamic characteristic and good in suspension stability.

Description

Technical Field

[0001] The present invention relates to the field of motor structure and control, and in particular to a novel bearingless permanent magnet synchronous motor and a control method thereof. Background Art

[0002] The bearingless permanent magnet synchronous motor is a new type of motor that combines the motor with magnetic suspension technology. It eliminates the traditional mechanical bearings and allows the motor rotor to suspend in the air, which has higher efficiency, lower noise, longer service life and lower maintenance costs.

[0003] In a bearingless permanent magnet synchronous motor, the design of the winding distribution and the design of the motor control method have an important impact on the performance and stability of the motor. In the prior art, it is difficult to accurately control the suspension force with the traditional winding design and control method, which easily leads to unstable rotor suspension; the suspended rotor itself has poor anti-interference ability, and the motor is easily affected by external interference during operation, such as load changes, magnetic field interference, etc., which will also affect the speed and stability of the rotor; in order to achieve stable operation of the bearingless permanent magnet synchronous motor, conventional control methods are difficult to maintain for a long time, so the motor life is reduced and the production cost investment will also increase. Summary of the invention

[0004] Purpose of the invention: To solve the problems mentioned in the background technology, the present invention provides a new type of bearingless permanent magnet synchronous motor and its control method, which generates multiple Maxwell forces in different directions by improving the stator setting and winding method, and realizes precise suspension and speed control of the bearingless permanent magnet synchronous motor rotor with the help of sensors and modular design control, thereby improving the motor efficiency and extending its life.

[0005] Technical solution:

[0006] The invention discloses a novel bearingless permanent magnet synchronous motor, comprising a stator, a rotor and a rotating shaft, wherein a plurality of permanent magnets are evenly arranged along the circumference of the outer side of the rotor, and 24 stator slots are evenly arranged along the circumference of the inner side of the stator, and the stator slots are divided into three layers.

[0007] The outermost layer is the torque winding, which is arranged with two pairs of poles. Two adjacent outer torque winding units are one phase. The three-phase windings are wound in the same way, and the current phases are distributed in a clockwise order of X positive phase, Y negative phase, Z positive phase, X negative phase, Y positive phase, and Z negative phase.

[0008] The middle layer and the inner layer are suspended windings. The middle layer suspended winding adopts a three-pole arrangement. Each slot is a separate phase. An empty slot is left between every three phases. The three-phase windings are wound in the same way. The current phases are distributed in a clockwise order as A2 positive phase, B2 negative phase, C2 positive phase, empty slot, A2 negative phase, B2 positive phase, and C2 negative phase.

[0009] The inner suspension winding is arranged in a pair of poles, four adjacent inner suspension winding units are one phase, the three-phase winding is wound in the same way, and the current phases are distributed in a clockwise order of A1 positive phase, B1 negative phase, C1 positive phase, A1 negative phase, B1 positive phase, and C1 negative phase; an air gap is provided between the stator and the permanent magnet.

[0010] Furthermore, the stator is provided with a displacement sensor, and the rotating shaft is provided with an encoder.

[0011] Furthermore, there is a difference in the number of pole pairs between the middle layer suspension winding and the inner layer suspension winding. When the number of pole pairs is different, Maxwell unbalanced magnetic pull can be generated. The generated unbalanced magnetic pull can decompose the suspension winding current into the d-axis and the q-axis to achieve precise suspension of the motor. The radial suspension force of the bearingless motor is:

[0012]

[0013] Among them, F x is the suspension force in the x-axis direction, F y is the suspension force in the y-axis direction; M0 and M1 are the two inductance coefficients of the suspension winding; i d is the torque winding d-axis current; i q is the q-axis current of the torque winding; i x is the d-axis current of the suspension winding; i y is the q-axis current of the suspension winding.

[0014] Furthermore, in order for the motor to generate a stable and controllable suspension force, current of the same frequency needs to be passed through the torque winding and the double-layer suspension winding, so as to keep the direction of the force unchanged during operation.

[0015] Furthermore, the novel bearingless permanent magnet synchronous motor is controlled by a specific control method, and the method comprises the following steps:

[0016] S1: The displacement sensor detects the offset in the x-axis and y-axis directions, and generates the suspension force F based on the offset α and F β The suspension force is transmitted to the force / magnetic conversion module.

[0017] S2: The angular velocity ω is generated by combining the suspension force with the signal collected by the encoder, and the suspension winding flux amplitude Δψ is generated through the force / magnetic conversion module. α and Δψ β , the required suspension control current i is obtained through the space vector modulation module and the inverter a 、i b and i c .

[0018] S3: pair i a 、i band i c Perform Clark transformation to obtain i α 、i β , change i α 、i β The input suspension force winding flux observer is compared with the observed flux to obtain the flux correction value ψ s And phase λ, the conversion formula is as follows:

[0019]

[0020] λ=arctan(∫(u β -R s i β )dt / ∫(u α -R s i α )dt)

[0021] Among them, R s is the stator resistance; u α is the α-axis voltage of the suspension winding; u β is the β-axis voltage of the suspension winding, and dt is the integral.

[0022] S4: Through the flux correction value ψ s And phase λ to get the suspension force reference value and And generate the required current to suspend the bearingless permanent magnet synchronous motor, the formula is as follows:

[0023]

[0024]

[0025] Among them, k M is the current stiffness coefficient of the suspension winding, and μ is the angle between the radial suspension force and the axis of the A-phase winding.

[0026] Furthermore, the control method can further regulate the motor speed, and the specific operations are as follows:

[0027] The torque winding flux amplitude ψ is calculated using the torque winding flux and torque observer s1 and phase θ and motor torque T e , speed command ω * The difference between the actual speed and the actual speed ω is modulated by the controller to generate the torque command value T e * , T e * With the actual torque value T eThe comparison difference is modulated by the controller to generate the torque winding flux phase angle increment Δδ. According to Δδ, the torque winding flux amplitude command value, and the real-time flux amplitude ψ s1 The voltage command value U is generated by the reference flux generation module and the phase θ α and U β , the three-phase torque control current i is obtained through the space vector pulse modulation module and the inverter module a1 、i b1 and i c1 , for i a1 、i b1 and i c1 Perform Clrak transformation to obtain i α1 、i β1 , and finally i α1 、i β1 The feedback into the torque winding flux and torque observer forms a closed loop to control the motor speed.

[0028] Beneficial effects:

[0029] 1. The present invention proposes a new winding arrangement structure of a bearingless permanent magnet synchronous motor, in which the magnetic field generated by the torque winding is two pairs of poles, and the magnetic field generated by the suspension winding is one pair of poles and three pairs of poles, so that the number of pole pairs of the torque winding and the suspension winding always differs by one pair of poles, thereby generating multiple Maxwell forces in different directions on the rotor, making the motor suspension control more stable.

[0030] 2. The present invention designs a novel bearingless permanent magnet synchronous motor control method, which can obtain data through encoders and displacement sensors, and can adjust the suspension rotor deviation for a long time to further maintain the stable operation of the motor. This method can further adjust the motor speed and can meet different production needs and cost requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application;

[0032] Figure 2 Schematic diagram of the winding of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application;

[0033] Figure 3 It is a magnetic line diagram of a middle winding of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application;

[0034] Figure 4 It is a magnetic field line diagram of the inner winding of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application;

[0035] Figure 5 It is a force and current curve diagram of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application;

[0036] Figure 6 This is a suspension control block diagram of a novel bearingless permanent magnet synchronous motor provided in an embodiment of the present application; DETAILED DESCRIPTION

[0037] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0038] like Figure 1 As shown, this embodiment discloses a novel bearingless permanent magnet synchronous motor, comprising a stator 1, a torque winding 2, a suspension winding 3, a permanent magnet 4 and a rotor 5, wherein an air gap 6 exists between the permanent magnet 4 and the stator 1. The permanent magnet 4 is evenly arranged on the outside of the rotor 5, and 24 stator slots are arranged circumferentially on the inner side of the stator 1, and the stator slots are divided into three layers, wherein the outermost layer is the torque winding 2, and the middle and inner layers are the suspension winding 3.

[0039] like Figure 2 As shown, in order to meet the requirements of different pole pairs of the torque winding and the suspension winding and seek the most stable rotor suspension effect, the winding arrangement designed in this embodiment is as follows:

[0040] Torque winding:

[0041] The torque winding is arranged with two pairs of poles. The two adjacent outer torque winding units are one phase. The three-phase winding is wound in the same way. The current phases are distributed in a clockwise order as X positive phase, Y negative phase, Z positive phase, X negative phase, Y positive phase, and Z negative phase.

[0042] Middle layer suspension winding:

[0043] The middle-layer suspension winding adopts a three-pole arrangement, each slot is a separate phase, and an empty slot is left between every three phases to ensure the three-pole arrangement structure. The three-phase windings are wound in the same way, and the current phases are distributed in a clockwise order: A2 positive phase, B2 negative phase, C2 positive phase, empty slot, A2 negative phase, B2 positive phase, C2 negative phase. The magnetic field line diagram of the middle-layer suspension winding is as follows: Figure 3 shown.

[0044] Inner suspension winding:

[0045] The inner suspension winding adopts a pair of poles. The four adjacent inner suspension winding units are one phase. The three-phase winding is wound in the same way. The current phase is distributed in a clockwise order: A1 positive phase, B1 negative phase, C1 positive phase, A1 negative phase, B1 positive phase, C1 negative phase. The magnetic field line diagram of the inner suspension winding is as follows: Figure 4shown.

[0046] The pole pairs of the middle suspension winding, the inner suspension winding and the torque winding must be kept inconsistent, so that the rotor generates Maxwell unbalanced magnetic pull in multiple directions. The unbalanced magnetic pull is used to decompose the suspension winding current into the d-axis and q-axis, thereby achieving precise suspension of the motor. The radial suspension force calculation formula of the bearingless motor is as follows:

[0047]

[0048] Among them, F x is the suspension force in the x-axis direction, F y is the suspension force in the y-axis direction; M0 and M1 are the two inductance coefficients of the suspension winding; i d is the torque winding d-axis current; i q is the q-axis current of the torque winding; i x is the d-axis current of the suspension winding; i y is the q-axis current of the suspension winding.

[0049] In order to make the motor further generate stable and controllable suspension force, the torque winding and the double-layer suspension winding need to be supplied with current of the same frequency, so as to keep the direction of the force unchanged during operation. Figure 5 shown.

[0050] like Figure 6 As shown, this embodiment also provides a novel control method for a bearingless permanent magnet synchronous motor, the steps are as follows:

[0051] S1: The displacement sensor detects the offset in the x-axis and y-axis directions, and generates the suspension force F based on the offset α and F β The suspension force is transmitted to the force-magnetic conversion module;

[0052] S2: The suspension force is combined with the signal collected by the encoder to calculate the angular velocity ω, and the suspension winding flux amplitude Δψ is generated. α and Δψ β , the required suspension control current i is obtained through the space vector modulation module and the inverter a 、i b and i c ;

[0053] S3: current i a 、i b and i c The input suspension force winding flux observer is compared with the observed flux to obtain the flux correction value ψ s and phase λ, as follows:

[0054] to i a、i b and i c Perform Clark transformation to obtain i α 、i β , change i α 、i β The input suspension force winding flux observer is compared with the observed flux to obtain the flux correction value ψ s And phase λ, the conversion formula is as follows:

[0055]

[0056] Among them, R s is the stator resistance; u α is the α-axis voltage of the suspension winding; u β is the β-axis voltage of the suspension winding, and dt is the integral.

[0057] S4: Through the flux correction value ψ s And phase λ to get the suspension force reference value and And generate the required current to suspend the bearingless permanent magnet synchronous motor, the formula is as follows:

[0058]

[0059]

[0060] In the above formula, k M is the current stiffness coefficient of the suspension winding, and μ is the angle between the radial suspension force and the axis of the A-phase winding.

[0061] In order to realize the speed control of the novel bearingless permanent magnet synchronous motor, the present embodiment provides the following method:

[0062] The torque winding flux amplitude ψ is calculated using the torque winding flux and torque observer s1 and phase θ and motor torque T e , speed command ω * The difference between the actual speed and the actual speed ω is modulated by the controller to generate the torque command value T e * , T e * With the actual torque value T e The comparison difference is modulated by the controller to generate the torque winding flux phase angle increment Δδ. According to Δδ, the torque winding flux amplitude command value, and the real-time flux amplitude ψ s1 The voltage command value U is generated by the reference flux generation module and the phase θ α and U β , the three-phase torque control current i is obtained through the space vector pulse modulation module and the inverter module a1 、ib1 and i c1 , for i a1 、i b1 and i c1 Perform Clrak transformation to obtain i α1 、i β1 Finally, i α1 、i β1 The feedback into the torque winding flux and torque observer forms a closed loop to control the motor speed.

[0063] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel bearingless permanent magnet synchronous motor, comprising a stator, a rotor and a rotating shaft, characterized in that: Multiple permanent magnets are evenly arranged along the circumference of the outer side of the rotor, and 24 stator slots are evenly arranged along the circumference of the inner side of the stator. The stator slots are divided into three layers: The outermost layer is the torque winding, which is arranged in two pairs of poles. Two adjacent outer torque winding units are one phase. The three-phase windings are wound in the same way, and the current phases are distributed in a clockwise order of X positive phase, Y negative phase, Z positive phase, X negative phase, Y positive phase, and Z negative phase; The middle and inner layers are suspended windings. The middle suspended winding adopts a three-pole arrangement. Each slot is a separate phase. There is an empty slot between every three phases. The three-phase windings are wound in the same way. The current phases are distributed in a clockwise order: A2 positive phase, B2 negative phase, C2 positive phase, empty slot, A2 negative phase, B2 positive phase, C2 negative phase. The inner suspension winding is arranged in a pair of poles. The four adjacent inner suspension winding units are one phase. The three-phase windings are wound in the same way. The current phases are distributed in a clockwise order: A1 positive phase, B1 negative phase, C1 positive phase, A1 negative phase, B1 positive phase, C1 negative phase; An air gap is provided between the stator and the permanent magnet.

2. A novel bearingless permanent magnet synchronous motor according to claim 1, characterized in that: The stator is provided with a displacement sensor, and the rotating shaft is provided with an encoder.

3. A novel bearingless permanent magnet synchronous motor according to claim 1, characterized in that: The pole pairs of the middle layer suspension winding and the inner layer suspension winding are different. When the pole pairs are different, Maxwell unbalanced magnetic pull can be generated. The unbalanced magnetic pull generated can decompose the suspension winding current into the d-axis and the q-axis to achieve precise suspension of the motor. The radial suspension force of the bearingless motor is: Among them, F x is the suspension force in the x-axis direction, F y is the suspension force in the y-axis direction; M0 and M1 are the two inductance coefficients of the suspension winding; i d is the torque winding d-axis current; i q is the q-axis current of the torque winding; i x is the d-axis current of the suspension winding; i y is the q-axis current of the suspension winding.

4. A novel bearingless permanent magnet synchronous motor according to claim 3, characterized in that: The current of the same frequency is passed through the torque winding and the double-layer suspension winding, so that the motor generates a stable and controllable suspension force, so as to keep the direction of the force unchanged during operation.

5. A novel bearingless permanent magnet synchronous motor control method according to any one of claims 1 to 4, characterized in that: The novel bearingless permanent magnet synchronous motor is controlled by a specific control method, which comprises the following steps: S1: The displacement sensor detects the offset in the x-axis and y-axis directions, and generates the suspension force F based on the offset α and F β Transmitting the suspension force into the force / magnetic conversion module; S2: The angular velocity ω is generated by combining the suspension force with the signal collected by the encoder, and the suspension winding flux amplitude Δψ is generated through the force / magnetic conversion module. α and Δψ β , the required suspension control current i is obtained through the space vector modulation module and the inverter a 、i b and i c ; S3: pair i a 、i b and i c Perform Clark transformation to obtain i α 、i β , change i α 、i β The input suspension force winding flux observer is compared with the observed flux to obtain the flux correction value ψ s And phase λ, the conversion formula is as follows: λ=arctan(∫(u β -R s i β )dt / ∫(u α -R s i α )dt) Among them, R s is the stator resistance; u α is the α-axis voltage of the suspension winding; u β is the β-axis voltage of the suspension winding, dt is the integral; S4: Through the flux correction value ψ s And phase λ to get the suspension force reference value and And generate the required current to suspend the bearingless permanent magnet synchronous motor, the formula is as follows: Among them, k M is the current stiffness coefficient of the suspension winding, and μ is the angle between the radial suspension force and the axis of the A-phase winding.

6. A novel bearingless permanent magnet synchronous motor control method according to claim 5, characterized in that: The control method can further adjust the motor speed, and the specific operations are as follows: The torque winding flux amplitude ψ is calculated using the torque winding flux and torque observer s1 and phase θ and motor torque T e , speed command ω * The difference between the actual speed and the actual speed ω is modulated by the controller to generate the torque command value T e * , T e * With the actual torque value T e The comparison difference is modulated by the controller to generate the torque winding flux phase angle increment Δδ. According to Δδ, the torque winding flux amplitude command value, and the real-time flux amplitude ψ s1 The voltage command value U is generated by the reference flux generation module and the phase θ α and U β , the three-phase torque control current i is obtained through the space vector pulse modulation module and the inverter module a1 、i b1 and i c1 , for i a1 、i b1 and i c1 Perform Clrak transformation to obtain i α1 、i β1 , and finally i α1 、i β1 The feedback into the torque winding flux and torque observer forms a closed loop to control the motor speed.

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