Torque decoupling permanent magnet biased bearingless switched reluctance motor and control method

Abstract

The invention discloses a torque decoupling permanent magnet biased bearingless switched reluctance motor and a control method. Permanent magnets are tightly arranged between a suspension stator and a torque stator of the motor to generate bias magnetic flux, the suspension stator is provided with four teeth, each tooth is wound with a suspension coil, every two suspension coils are connected in series to form two suspension windings, and the two suspension windings generate radial suspension force which is perpendicular to each other and naturally decoupled; included angles between U-shaped structures forming a torque stator and included angles between the U-shaped structures and suspension stator teeth are optimally designed, and matched rotor teeth are matched, so that a multi-phase working system motor can be formed, and the problems that an existing four-suspension stator tooth bearingless switched reluctance motor can only serve as a two-phase motor and is poor in starting performance are solved. The suspension power amplifier adopts a three-phase full-bridge circuit, a common bridge arm is set to be a constant value, suspension control is simple, and implementation is convenient; the motor torque is fully decoupled, the torque is short in magnetic circuit, the suspension force / current ratio is large, the permanent magnets can be made of ferrite permanent magnet materials, and the manufacturing cost is low.

Description

Technical Field

[0001] The invention relates to a torque-decoupled permanent magnet biased bearingless switched reluctance motor and a control method, belonging to the technical field of magnetic suspension motors. Background Art

[0002] The bearingless motor integrates the functions of a motor and a magnetic bearing, which can effectively reduce the axial length of the motor. It has a high critical speed and is expected to break through the speed constraints of the magnetic levitation motor system composed of traditional magnetic bearings and motors, thereby achieving ultra-high-speed operation. It has obvious advantages in the field of high-speed motors.

[0003] The traditional bearingless switched reluctance motors, such as 12 / 8, 6 / 4 and 8 / 6, have strong coupling between torque and suspension force due to the constraints of the operating mechanism, resulting in poor high-speed suspension performance of such motors. To this end, domestic and foreign scholars have proposed a number of new bearingless switched reluctance motor topologies with natural decoupling of torque and suspension force in the structure. The more typical ones are the 8 / 10 and 12 / 14 pole motors with wide and narrow stator teeth structures proposed by Korean scholars, both of which are decoupled. The suspension control of this type of bearingless motor is similar to that of magnetic bearings, while the rotation control is the same as that of the switched reluctance motor, and the two control channels of rotation and suspension are completely independent. In addition, since the suspension inductance is constant and does not change with the rotor angle, and thus does not generate motion electromotive force, it has better current chopping and tracking accuracy at high speeds, and better suspension characteristics.

[0004] However, 8 / 10 and 12 / 14 pole wide and narrow stator teeth bearingless switched reluctance motors can only operate as two-phase working motors, and there is a starting torque dead zone, which limits their popularization and application. Therefore, how to solve the problem of weak starting ability of such wide and narrow stator teeth bearingless switched reluctance motors is a research hotspot in this field. Summary of the invention

[0005] The purpose of the present invention is to address the defects and shortcomings of the above-mentioned prior art and to propose a torque-decoupled permanent magnet biased bearingless switched reluctance motor and a control method thereof. The torque control magnetic circuit and the suspension control magnetic circuit are isolated from each other, so that the torque and suspension force are naturally decoupled in the structure, and the two radial suspension forces are also decoupled from each other.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a torque decoupled permanent magnet biased bearingless switched reluctance motor, comprising a suspension stator 1, a torque stator 2, a suspension coil 4, a torque coil 5, a permanent magnet 3, a rotor 6 and a rotating shaft 7;

[0007] The torque stator 2 is arranged in the suspension stator 1, and the permanent magnet 3 is arranged between the torque stator 2 and the suspension stator 1; the rotor 6 is sleeved on the rotating shaft 7 and arranged in the torque stator 2 and the suspension stator 1;

[0008] The suspension stator 1 is a salient pole structure, the number of teeth is set to 4, the 4 teeth of the suspension stator 1 are evenly distributed on the circumference and the teeth are spaced 90 degrees apart; two teeth of the suspension stator 1 are in the horizontal direction, and the remaining two teeth are in the vertical direction;

[0009] The torque stator 2 is composed of 4m U-shaped structures, each of which has 2 teeth, wherein m represents the number of U-shaped structures arranged between two adjacent teeth in the suspension stator, and m=2 or 3; the rotor 6 is a salient pole structure;

[0010] m U-shaped structures are arranged between two adjacent teeth of the suspension stator 1, and a tile-shaped permanent magnet 3 is closely arranged between each U-shaped structure and the suspension stator 1, and a total of 4m permanent magnets 3 are arranged;

[0011] A suspension coil 4 is wound around each tooth of the suspension stator 1. There are four suspension coils 4 in total. Two suspension coils 4 wound around two teeth in the horizontal direction are connected in series to form a horizontal suspension winding, and two suspension coils 4 wound around two teeth in the vertical direction are connected in series to form a vertical suspension winding.

[0012] A torque coil 5 is wound around each tooth of the U-shaped structure, and a total of 8m torque coils 5 are provided;

[0013] The permanent magnets 3 are magnetized radially, and all the permanent magnets 3 are arranged with the same polarity.

[0014] Furthermore, when m=2, the number of teeth of the rotor 6 is 18, the angle between the two teeth in the U-shaped structure is 20°, and the pole arc angle of each tooth of the torque stator 2 is 20°; the center line of the U-shaped structure differs from the center line of the tooth of the adjacent suspension stator 1 by 27.5°, and the center lines of the two adjacent U-shaped structures differ by 35°; the four torque coils 5 on the teeth of the two U-shaped structures separated by 180° are connected in series to form a one-phase torque winding, which are A, B, C, and D phase torque windings in a clockwise direction, respectively. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a two-phase working motor.

[0015] Furthermore, when m=3, the number of teeth of the rotor 6 is 24, the angle between the two teeth in the U-shaped structure is 15°, and the pole arc angle of each tooth of the torque stator 2 is 15°; the center line of the U-shaped structure differs by 20° from the center line of the tooth of the adjacent suspension stator 1, and the center lines of the two adjacent U-shaped structures differ by 25°; the eight torque coils 5 on the four U-shaped structure teeth separated by 90° are connected in series to form a one-phase torque winding, which are A, B, and C phase torque windings in a clockwise direction, respectively. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a three-phase working motor.

[0016] The present invention also proposes a control method for a permanent magnet biased bearingless switched reluctance motor for torque decoupling, comprising: the permanent magnet biased bearingless switched reluctance motor being a three-phase working motor, wherein the two windings are respectively a three-phase torque winding (A, B, C phases) and two suspension windings (horizontal and vertical suspension windings), wherein the three-phase torque winding is driven by an asymmetric half-bridge power converter for rotational operation, and the two suspension windings are driven by a three-phase full-bridge power converter for suspension control; the three-phase full-bridge power converter includes three bridge arms, namely a common bridge arm, an X-axis suspension bridge arm and a Y-axis suspension bridge arm, wherein the common bridge arm is composed of an upper switch tube Q1 and a lower switch tube Q2, the X-axis suspension bridge arm is composed of an upper switch tube Q3 and a lower switch tube Q4, the X-axis suspension bridge arm is composed of an upper switch tube Q5 and a lower switch tube Q6, and the X-axis suspension One end of the winding is connected to the midpoint of the X-axis suspension bridge arm, one end of the Y-axis suspension winding is connected to the midpoint of the Y-axis suspension bridge arm, and the other ends of the X-axis suspension winding and the Y-axis suspension winding are connected together and then connected to the midpoint of the common bridge arm; assuming that the duty cycle of the upper switch tube Q1 is D0, the duty cycle of the upper switch tube Q3 is Dx, and the duty cycle of the upper switch tube Q5 is Dy, according to the principle of complementary conduction of the upper and lower switch tubes, it can be calculated that the duty cycle of the lower switch tube Q2 is 1-D0, the duty cycle of the lower switch tube Q4 is 1-Dx, and the duty cycle of the lower switch tube Q6 is 1-Dy; when D0, Dx or Dy is zero, it means that the upper switch tube Q1, Q3 or Q5 is turned off, conversely, when D0, Dx or Dy is 1, it means that the upper switch tube Q1, Q3 or Q5 is turned on, and m represents the number of U-shaped structures arranged between two adjacent teeth in the suspension stator;

[0017] When m=3, the control method comprises the following steps:

[0018] Step 1: Get the given values ​​of the X and Y axis suspension winding currents and The step 1 comprises:

[0019] Step 1-1: Use a displacement sensor to detect in real time to obtain real-time values ​​x and y of the rotor displacement in the X and Y axis directions, where the X axis is in the horizontal direction and the Y axis is in the vertical direction;

[0020] Step 1-2: Set the reference value x of the displacement in the X and Y axis directions * ,y * Subtract the real-time values ​​x and y, and then adjust them through the proportional integral differential regulator to obtain the given values ​​of the X and Y axis suspension winding currents. and

[0021] Step 2: Obtaining the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms, wherein step 2 includes:

[0022] Step 2-1: Use the current sensor to detect in real time and obtain the real-time value of the X and Y axis suspension winding current i x and i y ;

[0023] Step 2-2: Given value of the suspension winding current and Respectively with its real-time value i x and i y Subtracting them, and then adjusting them through the proportional integral differential regulator, the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms are obtained;

[0024] Step 3: adjusting the suspension force, said step 3 comprising:

[0025] Step 3-1: To simplify the control, directly set the duty cycle D0 of the upper switch tube Q1 of the common bridge arm to 0.5. At this time, the duty cycle of the lower switch tube Q2 of the bridge arm is (1-D0)=0.5;

[0026] Step 3-2: Real-time adjustment of the duty cycle Dx and Dy of the X-axis and Y-axis suspension bridge arms, and then dynamically control the conduction time of the upper and lower switch tubes of the X-axis and Y-axis suspension bridge arms, so that the real-time value of the X-axis and Y-axis suspension winding current i x and i y Track their given values ​​respectively and Thereby, the radial suspension force is adjusted in real time: the rotor 6 of the torque-decoupled permanent magnet biased bearingless switched reluctance motor can be stably suspended;

[0027] Step 4: Obtain the reference value of the three-phase torque winding current at low speed operation And the opening angle θ at high speed operation on ; Step 4 comprises:

[0028] Step 4-1: Use a position sensor to detect the position of the rotor in real time, obtain the rotor position angle θ, and obtain the real-time value n of the rotation speed by calculation;

[0029] Step 4-2: Set the critical speed of the low speed and high speed operating states to n0, whose value is determined by the motor operating condition;

[0030] Step 4-3: When n≤n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the reference value of the three-phase torque winding current. At this time, in order to simplify the control, the opening angle θ of each phase torque winding is directly set on and the turn-off angle θ off , and the values ​​of both are determined by the motor structure and working conditions;

[0031] Step 4-4: When n>n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the opening angle θ on ; At this time, directly set the cut-off angle θ off , whose value is determined by the motor structure and working conditions;

[0032] Step 5: adjusting the torque; said step 5 comprises:

[0033] Step 5-1: When n≤n0, use the current chopping control method to make the real-time value of the A, B, and C three-phase torque winding current i a 、i b 、i c Track their reference values ​​separately Then the three-phase torque winding current can be adjusted in real time to adjust the torque;

[0034] Step 5-2: When n>n0, use the angle position control method to adjust the opening angle θ in real time on value, thereby dynamically controlling the torque.

[0035] Further, the method includes: when m=2, the control method of the torque and suspension force of the permanent magnet biased bearingless switched reluctance motor is the same as the control method when m=3, except that the number of phases of the torque winding of the motor is changed from three to two.

[0036] Beneficial effects:

[0037] 1. The torque control magnetic circuit and the suspension control magnetic circuit of the present invention are isolated from each other, the torque and the suspension force are naturally decoupled in the structure, and the two radial suspension forces are also decoupled from each other.

[0038] 2. The permanent magnets of the present invention are arranged between the suspension stator and the torque stator, with high space utilization. Since multiple permanent magnet circuits are connected in parallel to provide bias flux for suspension, the flux density generated by a single permanent magnet is not required to be high, and cheaper rare earth-free permanent magnets such as ferrite can meet the needs, thereby effectively reducing the cost of the motor.

[0039] 3. The present invention uses permanent magnets to generate the bias magnetic flux required for suspension, and has a large suspension force / current ratio, which is beneficial to reducing the power loss of the suspension system and reducing the design difficulty of the suspension power system.

[0040] 4. Although the magnetic circuit of the bias magnetic flux generated by the permanent magnet of the present invention overlaps with the torque magnetic circuit, the cogging torque generated by the permanent magnet is small and can be ignored. At the same time, the permanent magnet magnetic flux has little effect on the torque output and promotes the torque output. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1It is a schematic diagram of the three-dimensional structure of a torque-decoupled permanent magnet biased bearingless switched reluctance motor according to the first embodiment of the present invention.

[0042] Label description: 1-suspension stator; 2-torque stator; 3-permanent magnet; 4-suspension coil; 5-torque coil; 6-rotor; 7-rotating shaft.

[0043] Figure 2 Schematic diagram of magnetic flux generated by permanent magnets and Y-axis suspension winding current in Embodiment 1 of the present invention.

[0044] Marking description: 8-bias flux one; 9-suspension control flux one.

[0045] Figure 3 Schematic diagram of magnetic flux generated by the A-phase torque winding current in the first embodiment of the present invention.

[0046] Marking Description: 10-Magnetic Flux One.

[0047] Figure 4 It is a schematic diagram of the three-dimensional structure of a torque-decoupled permanent magnet biased bearingless switched reluctance motor according to the second embodiment of the present invention.

[0048] Label description: 1-suspension stator; 2-torque stator; 3-permanent magnet; 4-suspension coil; 5-torque coil; 6-rotor; 7-rotating shaft.

[0049] Figure 5 Schematic diagram of magnetic flux generated by permanent magnets and Y-axis suspension winding current in Embodiment 2 of the present invention.

[0050] Label description: 11-Bias flux 2; 12-Suspension control flux 2.

[0051] Figure 6 Schematic diagram of magnetic flux generated by the A-phase torque winding current in the second embodiment of the present invention.

[0052] Logo Description: 13-Magnetic Flux 2.

[0053] Figure 7 This is a finite element simulation value diagram of the permanent magnet, the A-phase torque winding current, and the torque generated by the two in the second embodiment of the present invention.

[0054] Figure 8 It is a finite element simulation value diagram of the Y-axis radial suspension force in the second embodiment of the present invention.

[0055] Fig. 9 The present invention is a flow chart of a suspension power converter of a permanent magnet biased bearingless switched reluctance motor and a method for connecting suspension windings in two directions.

[0056] Fig.10 This is a control block diagram of Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0057] The invention will be further described in detail below in conjunction with the accompanying drawings.

[0058] Embodiment 1

[0059] like Figure 1 Shown is a three-dimensional schematic diagram of a torque-decoupled permanent magnet biased bearingless switched reluctance motor according to the first embodiment of the present invention;

[0060] The torque-decoupled permanent magnet biased bearingless switched reluctance motor in the first embodiment is composed of a suspension stator 1, a torque stator 2, a suspension coil 4, a torque coil 5, a permanent magnet 3, a rotor 6 and a rotating shaft 7;

[0061] The torque stator 2 is arranged in the suspension stator 1, and the permanent magnet 3 is arranged between the torque stator 2 and the suspension stator 1; the rotor 6 is sleeved on the rotating shaft 7 and arranged in the torque stator 2 and the suspension stator 1;

[0062] The suspension stator 1 is a salient pole structure, and the number of teeth is set to 4. The 4 teeth of the suspension stator 1 are evenly distributed on the circumference and the teeth are separated by 90°. Among them, two teeth of the suspension stator 1 are in the horizontal direction, and the remaining two teeth are in the vertical direction;

[0063] The torque stator 2 is composed of 8 U-shaped structures, each of which has 2 teeth, and the rotor 6 is a salient pole structure;

[0064] Two U-shaped structures are arranged between two adjacent teeth of the suspension stator 1, and a tile-shaped permanent magnet 3 is closely arranged between each U-shaped structure and the suspension stator 1, and a total of 8 tile-shaped permanent magnets 3 are arranged;

[0065] A suspension coil 4 is wound around each tooth of the suspension stator 1, and a total of four suspension coils 4 are provided. The two suspension coils 4 wound around two teeth in the horizontal direction are connected in series to form a horizontal suspension winding, and the two suspension coils 4 wound around two teeth in the vertical direction are connected in series to form a vertical suspension winding.

[0066] A torque coil 5 is wound around each tooth of the U-shaped structure, and a total of 16 torque coils 5 are provided;

[0067] The permanent magnets 3 are magnetized radially, and all the permanent magnets 3 are arranged with the same polarity;

[0068] The number of teeth of the rotor 6 is 18, the angle between the two teeth in the U-shaped structure is 20°, and the pole arc angle of each tooth of the torque stator 2 is 20°; the center line of the U-shaped structure differs from the center line of the tooth of the adjacent suspension stator 1 by 27.5°, and the center lines of the two adjacent U-shaped structures differ by 35°; the four torque coils 5 on the two U-shaped structure teeth separated by 180° are connected in series to form a one-phase torque winding, which are A, B, C, and D phase torque windings in a clockwise direction. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a four-phase working motor.

[0069] like Figure 2 The figure shows a schematic diagram of the magnetic flux generated by the permanent magnet 3 and the Y-axis suspension winding current in the first embodiment of the present invention; the bias magnetic flux 8 generated by the permanent magnet 3 passes through the permanent magnet 3, two teeth of the U-shaped structure, the air gap, the rotor 6, the air gap, the teeth of the suspension stator 1, the yoke of the suspension stator 1, and then to the permanent magnet 3 to form a closed magnetic circuit; the suspension control magnetic flux 9 generated by the Y-axis suspension winding current passes through the teeth of the suspension stator 1, the air gap, the rotor 6, the air gap, the relative teeth of the suspension stator 1, and then through the yoke of the suspension stator 1 to form a closed magnetic circuit; when the Y-axis suspension winding is passed into Figure 2 When the current shown is used, the suspension control magnetic flux 9 generated by it is in the same direction as the bias magnetic flux 8 generated by the permanent magnet 3 in the air gap at the suspension stator 1 in the positive direction of the Y axis, and in the opposite direction to the bias magnetic flux 8 generated by the permanent magnet 3 in the air gap at the suspension stator 1 in the negative direction of the Y axis, thereby generating a radial suspension force in the positive direction of the Y axis. When the direction of the Y-axis suspension winding current changes, a radial suspension force in the negative direction of the Y axis will be generated. Similarly, the X-axis suspension winding current can generate an X-axis radial suspension force. Therefore, by reasonably controlling the magnitude and direction of the two suspension winding currents of the X and Y axes, a radial suspension force of any magnitude and direction can be generated, thereby realizing radial suspension of the rotor 6.

[0070] like Figure 3 The figure shows a schematic diagram of the magnetic flux 10 generated by the A-phase winding current in the first embodiment of the present invention; the magnetic flux path of the A-phase winding current in each U-shaped structure is: one tooth of the U-shaped structure, the tooth of the rotor 6, the yoke of the rotor 6, the tooth of another rotor 6, the air gap, the other tooth of the U-shaped structure, the yoke of the U-shaped structure, and then back to the tooth of the U-shaped structure to form a closed loop. The torque magnetic circuit is a short magnetic circuit structure, which is beneficial to reduce the core loss. The magnetic flux generated by the B, C, and D phase winding currents is similar to that generated by the A phase winding current.

[0071] Embodiment 2

[0072] like Figure 4 Shown is a three-dimensional schematic diagram of a torque-decoupled permanent magnet biased bearingless switched reluctance motor according to a second embodiment of the present invention;

[0073] The torque-decoupled permanent magnet biased bearingless switched reluctance motor in the second embodiment is composed of a suspension stator 1, a torque stator 2, a suspension coil 4, a torque coil 5, a permanent magnet 3, a rotor 6 and a rotating shaft 7;

[0074] The torque stator 2 is arranged in the suspension stator 1, and the permanent magnet 3 is arranged between the torque stator 2 and the suspension stator 1; the rotor 6 is sleeved on the rotating shaft 7 and arranged in the torque stator 2 and the suspension stator 1;

[0075] The suspension stator 1 is a salient pole structure, and the number of teeth is set to 4. The 4 teeth of the suspension stator 1 are evenly distributed on the circumference and the teeth are separated by 90°. Among them, two teeth of the suspension stator 1 are in the horizontal direction, and the remaining two teeth are in the vertical direction;

[0076] The torque stator 2 is composed of 12 U-shaped structures, and the number of teeth of each U-shaped structure is set to 2;

[0077] Three U-shaped structures are arranged between two adjacent teeth of the suspension stator 1, and a tile-shaped permanent magnet 3 is closely arranged between each U-shaped structure and the suspension stator 1, and a total of 12 tile-shaped permanent magnets 3 are arranged;

[0078] A suspension coil 4 is wound around each tooth of the suspension stator 1, and a total of four suspension coils 4 are provided. The two suspension coils 4 wound around two teeth in the horizontal direction are connected in series to form a horizontal suspension winding, and the two suspension coils 4 wound around two teeth in the vertical direction are connected in series to form a vertical suspension winding.

[0079] A torque coil 5 is wound around each tooth of the U-shaped structure, and a total of 24 torque coils 5 are provided;

[0080] The permanent magnets 3 are magnetized radially, and all the permanent magnets 3 are arranged with the same polarity;

[0081] The rotor 6 is a salient pole structure with 24 teeth. The angle between the two teeth in the U-shaped structure is 15°, and the pole arc angle of each tooth of the torque stator 2 is 15°. The center line of the U-shaped structure differs by 20° from the center line of the tooth of the adjacent suspension stator 1, and the center lines of the two adjacent U-shaped structures differ by 25°. The eight torque coils 5 on the four U-shaped structure teeth separated by 90° are connected in series to form a single-phase torque winding, which are A, B, and C phase torque windings in a clockwise direction. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a three-phase working motor.

[0082] like Figure 5The figure shows a schematic diagram of the magnetic flux generated by the permanent magnet 3 and the Y-axis suspension winding current in the second embodiment of the present invention; the bias magnetic flux 11 generated by the permanent magnet 3 passes through the permanent magnet 3, two teeth of the U-shaped structure, the air gap, the rotor 6, the air gap, the teeth of the suspension stator 1, the yoke of the suspension stator 1, and then to the permanent magnet 3 to form a closed magnetic circuit; the suspension control magnetic flux 12 generated by the Y-axis suspension winding current passes through the teeth of the suspension stator 1, the air gap, the rotor 6, the air gap, the relative teeth of the suspension stator 1, and then through the yoke of the suspension stator 1 to form a closed magnetic circuit; when the Y-axis suspension winding is passed into Figure 2 When the current shown is, the suspension control magnetic flux 12 generated by it is in the same direction as the bias magnetic flux 11 generated by the permanent magnet 3 in the air gap at the suspension stator 1 in the positive direction of the Y axis, and in the opposite direction to the bias magnetic flux 11 generated by the permanent magnet 3 in the air gap at the suspension stator 1 in the negative direction of the Y axis, thereby generating a radial suspension force in the positive direction of the Y axis. When the direction of the Y-axis suspension winding current changes, a radial suspension force in the negative direction of the Y axis will be generated. Similarly, the X-axis suspension winding current can generate an X-axis radial suspension force. Therefore, by reasonably controlling the size and direction of the two suspension winding currents of the X and Y axes, a radial suspension force of any size and direction can be generated, thereby realizing radial suspension of the rotor 6.

[0083] like Figure 6 The figure shows a schematic diagram of the magnetic flux 13 generated by the A-phase winding current in the second embodiment of the present invention; the magnetic flux path of the A-phase winding current in each U-shaped structure is: one tooth of the U-shaped structure, the tooth of the rotor 6, the yoke of the rotor 6, the tooth of another rotor 6, the air gap, the other tooth of the U-shaped structure, the yoke of the U-shaped structure, and then back to the tooth of the U-shaped structure to form a closed loop. The torque magnetic circuit is a short magnetic circuit structure, which is beneficial to reduce the core loss. The magnetic flux generated by the B, C, and D phase winding currents is similar to that generated by the A phase winding current.

[0084] like Figures 7 and 8The figure shows the finite element simulation value diagram of torque and radial suspension force in the second embodiment of the present invention. The curves of reference numbers 14 and 17 are respectively the torque (cogging torque) and radial suspension force generated by the permanent magnet 3 alone. The smaller the two values, the better. The simulation results show that the permanent magnet 3 does not generate radial suspension force, and the cogging torque is very small, which shows that the arrangement and magnetization direction of the permanent magnet 3 of the motor of the present invention are correct. Reference number 15 is the torque finite element simulation value generated by the A-phase torque current, which is the same as the torque characteristics of the traditional switched reluctance motor; reference number 16 is the torque finite element simulation value generated by the A-phase torque winding current and the permanent magnet. Compared with reference number 15, under the action of the permanent magnet 3, the output torque is slightly improved, which shows that the permanent magnet 3 can not only generate the bias flux required for suspension, but also help to improve the output quality of the torque. Reference number 18 is the radial suspension force finite element simulation value generated by the Y-axis suspension winding current under the bias flux generated by the permanent magnet 3. The simulation results show that the radial suspension force has a large value in the entire rotor 6 position cycle and has good stability.

[0085] like Fig. 9 As shown, the present invention discloses a suspension power converter of a permanent magnet biased bearingless switched reluctance motor and a method for connecting suspension windings in two directions. In general, two suspension windings of the X and Y axes require two H-bridge power circuits, with a total of four bridge arms. In order to reduce the cost of the suspension power system, the present invention adopts a three-phase full-bridge power converter. The three-phase full-bridge power converter includes three bridge arms, namely a common bridge arm, an X-axis suspension bridge arm and a Y-axis suspension bridge arm, wherein the common bridge arm is composed of an upper switch tube Q1 and a lower switch tube Q2, the X-axis suspension bridge arm is composed of an upper switch tube Q3 and a lower switch tube Q4, and the X-axis suspension bridge arm is composed of an upper switch tube Q5 and a lower switch tube Q6. One end of the X-axis suspension winding is connected to the midpoint of the X-axis suspension bridge arm, and one end of the Y-axis suspension winding is connected to the midpoint of the Y-axis suspension bridge arm. After the other ends of the X-axis suspension winding and the Y-axis suspension winding are connected together, they are connected to the common bridge arm. The midpoint of the common bridge arm; assuming that the duty cycle of the upper switch tube Q1 is D0, the duty cycle of the upper switch tube Q3 is Dx, and the duty cycle of the upper switch tube Q5 is Dy, according to the principle of complementary conduction of the upper and lower switch tubes, it can be calculated that the duty cycle of the lower switch tube Q2 is 1-D0, the duty cycle of the lower switch tube Q4 is 1-Dx, and the duty cycle of the lower switch tube Q6 is 1-Dy; when D0, Dx or Dy is zero, it means that the upper switch tube Q1, Q3 or Q5 is turned off, conversely, when D0, Dx or Dy is 1, it means that the upper switch tube Q1, Q3 or Q5 is turned on.

[0086] The present invention also proposes a control method for a permanent magnet biased bearingless switched reluctance motor for torque decoupling, such as Fig.10 The control block diagram of the second embodiment of the present invention is shown. At this time, the torque decoupled permanent magnet biased bearingless switched reluctance motor is a three-phase working motor, wherein i a + is the inflow current of the A-phase torque winding, ia - is the outflow current of the A-phase torque winding, i x +、i y + are the inflow currents of the X-axis and Y-axis suspension windings, i x -、i y - are the outflow currents of the suspension windings on the X and Y axes, respectively. X, Y, and Z are the three coordinate axes of the rectangular coordinate system, and U dc is the voltage of the DC power supply, m represents the number of U-shaped structures arranged between two adjacent teeth in the suspension stator, when m=3, the control method includes the following steps:

[0087] Step 1: Get the given values ​​of the X and Y axis suspension winding currents and The specific steps are:

[0088] Step 1-1: Use a displacement sensor to detect in real time to obtain real-time values ​​x and y of the rotor displacement in the X and Y axis directions, where the X axis is in the horizontal direction and the Y axis is in the vertical direction;

[0089] Step 1-2: Set the reference value x of the displacement in the X and Y axis directions * ,y * Subtract the real-time values ​​x and y, and then adjust them through the proportional integral differential regulator to obtain the given values ​​of the X and Y axis suspension winding currents. and

[0090] Step 2: Get the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms. The specific steps are as follows:

[0091] Step 2-1: Use the current sensor to detect in real time and obtain the real-time value of the X and Y axis suspension winding current i x and i y ;

[0092] Step 2-2: Given value of suspension winding current and Respectively with its real-time value i x and i y Subtracting them, and then adjusting them through the proportional integral differential regulator, the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms are obtained;

[0093] Step 3: Adjust the suspension force. The specific steps are as follows:

[0094] Step 3-1: To simplify the control, directly set the duty cycle D0 of the upper switch tube Q1 of the common bridge arm to 0.5. At this time, the duty cycle of the lower switch tube Q2 of the bridge arm is (1-D0)=0.5;

[0095] Step 3-2: Real-time adjustment of the duty cycle Dx and Dy of the X-axis and Y-axis suspension bridge arms, and then dynamically control the conduction time of the upper and lower switch tubes of the X-axis and Y-axis suspension bridge arms, so that the real-time value of the X-axis and Y-axis suspension winding current i x and i y Track their given values ​​respectively and Thus, the radial suspension force is adjusted in real time, and finally the stable suspension of the rotor 6 of the torque-decoupled permanent magnet biased bearingless switched reluctance motor is achieved;

[0096] Step 4: Obtain the reference value of the three-phase torque winding current at low speed operation And the opening angle θ at high speed operation on ; The specific steps are as follows:

[0097] Step 4-1: Use a position sensor to detect the position of the rotor 6 in real time, obtain the position angle θ of the rotor 6, and obtain the real-time value n of the rotation speed by calculation;

[0098] Step 4-2: Set the critical speed of the low speed and high speed operating states to n0, whose value is determined by the motor operating condition;

[0099] Step 4-3: When n≤n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the reference value of the three-phase torque winding current. At this time, in order to simplify the control, the opening angle θ of each phase torque winding is directly set on and the turn-off angle θ off , and the values ​​of both are determined by the motor structure and working conditions;

[0100] Step 4-4: When n>n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the opening angle θ on ; At this time, directly set the cut-off angle θ off , its value is determined by the motor structure and working conditions;

[0101] Step 5: Adjust the torque; the specific steps are as follows:

[0102] Step 5-1: When n≤n0, use the current chopping control method to make the real-time value of the A, B, and C three-phase torque winding current i a 、i b 、i c Track their reference values ​​separately Then the three-phase torque winding current can be adjusted in real time to achieve the purpose of adjusting the torque;

[0103] Step 5-2: When n>n0, use the angle position control method to adjust the opening angle θ in real timeon value, thereby dynamically controlling the torque.

[0104] In addition, when m=2, the control method of the torque and suspension force of the permanent magnet biased bearingless switched reluctance motor is the same as the control method when m=3, except that the number of phases of the torque winding of the motor is changed from three to two.

[0105] The present invention proposes a torque-decoupled permanent magnet biased bearingless switched reluctance motor and a control method. By adopting the technical solution of the present invention, the following technical effects can be achieved: (1) the torque control magnetic circuit and the suspension control magnetic circuit are isolated from each other, the torque and the suspension force are naturally decoupled in the structure, and the two radial suspension forces are also decoupled from each other; (2) the permanent magnet 3 is arranged between the suspension stator 1 and the torque stator 2, and the space utilization rate is high. Since multiple permanent magnet magnetic circuits are connected in parallel to provide bias magnetic flux for suspension, the magnetic flux density generated by a single permanent magnet 3 is not required to be high, and cheaper rare earth-free permanent magnets such as ferrite can meet the requirements, thereby effectively reducing the cost of the motor; (3) the permanent magnet 3 is used to generate the bias magnetic flux required for suspension, and the suspension force / current ratio is large, which is conducive to reducing the power loss of the suspension system and reducing the design difficulty of the suspension power system; (4) although the magnetic circuit for generating the bias magnetic flux by the permanent magnet 3 overlaps with the torque magnetic circuit, the cogging torque generated by the permanent magnet is small and can be ignored. At the same time, the permanent magnet magnetic flux has little effect on the torque output and promotes the torque output.

[0106] For those skilled in the art, other advantages and variations can be easily associated with the above implementation types. Therefore, the present invention is not limited to the above specific examples, which are merely used as examples to provide a detailed and exemplary description of one form of the present invention. Without departing from the scope of the present invention, the technical solutions obtained by those skilled in the art through various equivalent substitutions based on the above specific examples should be included in the scope of the claims of the present invention and their equivalents.

Claims

1. A torque decoupled permanent magnet biased bearingless switched reluctance motor, characterized in that: It comprises a suspension stator (1), a torque stator (2), a suspension coil (4), a torque coil (5), a permanent magnet (3), a rotor (6) and a rotating shaft (7); The torque stator (2) is arranged inside the suspension stator (1), and the permanent magnet (3) is arranged between the torque stator (2) and the suspension stator (1); the rotor (6) is sleeved on the rotating shaft (7) and arranged inside the torque stator (2) and the suspension stator (1); The suspension stator (1) is a salient pole structure, the number of teeth is set to 4, the 4 teeth of the suspension stator (1) are evenly distributed on the circumference and the teeth are spaced 90 degrees apart; two teeth of the suspension stator (1) are in the horizontal direction, and the remaining two teeth are in the vertical direction; The torque stator (2) is composed of 4m U-shaped structures, each of which has 2 teeth, wherein m represents the number of U-shaped structures arranged between two adjacent teeth in the suspension stator, and m=2 or 3; the rotor (6) is a salient pole structure; m U-shaped structures are arranged between two adjacent teeth of the suspension stator (1), and a tile-shaped permanent magnet (3) is closely arranged between each U-shaped structure and the suspension stator (1), and a total of 4m permanent magnets (3) are arranged; A suspension coil (4) is wound around each tooth of the suspension stator (1), and a total of four suspension coils (4) are provided. The two suspension coils (4) wound around two teeth in the horizontal direction are connected in series to form a horizontal suspension winding, and the two suspension coils (4) wound around two teeth in the vertical direction are connected in series to form a vertical suspension winding. A torque coil (5) is wound around each tooth of the U-shaped structure, and a total of 8m torque coils (5) are provided; The permanent magnets (3) are magnetized radially, and all the permanent magnets (3) are arranged with the same polarity.

2. A torque-decoupled permanent magnet biased bearingless switched reluctance motor according to claim 1, characterized in that: The invention comprises that when m=2, the number of teeth of the rotor (6) is 18, the angle between the two teeth in the U-shaped structure is 20°, and the pole arc angle of each tooth of the torque stator (2) is 20°; the center line of the U-shaped structure differs from the center line of the tooth of the adjacent suspension stator (1) by 27.5°, and the center lines of the two adjacent U-shaped structures differ by 35°; the four torque coils (5) on the teeth of the two U-shaped structures separated by 180° are connected in series to form a one-phase torque winding, which are A, B, C, and D phase torque windings in a clockwise direction, respectively. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a two-phase working motor.

3. A torque-decoupled permanent magnet biased bearingless switched reluctance motor according to claim 1, characterized in that: The invention comprises that when m=3, the number of teeth of the rotor (6) is 24, the angle between two teeth in the U-shaped structure is 15°, and the pole arc angle of each tooth of the torque stator (2) is 15°; the center line of the U-shaped structure differs by 20° from the center line of the tooth of the adjacent suspension stator (1), and the center lines of two adjacent U-shaped structures differ by 25°; eight torque coils (5) on four U-shaped structure teeth spaced 90° apart are connected in series to form a one-phase torque winding, which are A, B, and C phase torque windings in a clockwise direction, respectively. At this time, the torque-decoupled permanent magnet biased bearingless switched reluctance motor is a three-phase working motor.

4. A control method for a permanent magnet biased bearingless switched reluctance motor for torque decoupling, characterized in that: The permanent magnet biased bearingless switched reluctance motor comprises a three-phase torque winding (A, B, C phases) and two suspension windings (horizontal and vertical suspension windings), wherein the three-phase torque winding is driven by an asymmetric half-bridge power converter for rotational operation, and the two suspension windings are driven by a three-phase full-bridge power converter for suspension control; the three-phase full-bridge power converter comprises three bridge arms, namely a common bridge arm, an X-axis suspension bridge arm and a Y-axis suspension bridge arm, wherein the common bridge arm is composed of an upper switch tube Q1 and a lower switch tube Q2, the X-axis suspension bridge arm is composed of an upper switch tube Q3 and a lower switch tube Q4, the X-axis suspension bridge arm is composed of an upper switch tube Q5 and a lower switch tube Q6, one end of the X-axis suspension winding is connected to the midpoint of the X-axis suspension bridge arm, and one end of the Y-axis suspension winding is connected to the midpoint of the X-axis suspension bridge arm. The end is connected to the midpoint of the Y-axis suspension bridge arm, and the other ends of the X-axis suspension winding and the Y-axis suspension winding are connected together, and then connected to the midpoint of the common bridge arm; assuming that the duty cycle of the upper switch tube Q1 is D0, the duty cycle of the upper switch tube Q3 is Dx, and the duty cycle of the upper switch tube Q5 is Dy, according to the principle of complementary conduction of the upper and lower switch tubes, it can be calculated that the duty cycle of the lower switch tube Q2 is 1-D0, the duty cycle of the lower switch tube Q4 is 1-Dx, and the duty cycle of the lower switch tube Q6 is 1-Dy; when D0, Dx or Dy is zero, it means that the upper switch tube Q1, Q3 or Q5 is turned off, conversely, when D0, Dx or Dy is 1, it means that the upper switch tube Q1, Q3 or Q5 is turned on, and m represents the number of U-shaped structures arranged between two adjacent teeth in the suspension stator; When m=3, the method comprises the following steps: Step 1: Get the given value i of the X and Y axis suspension winding current x * and i y * , the step 1 comprises: Step 1-1: Use a displacement sensor to detect in real time to obtain real-time values ​​x and y of the rotor displacement in the X and Y axis directions, where the X axis is in the horizontal direction and the Y axis is in the vertical direction; Step 1-2: Set the reference value x of the displacement in the X and Y axis directions * ,y * Subtract the real-time value x and y, and then adjust them through the proportional integral differential regulator to obtain the given value i of the X-axis and Y-axis suspension winding current x * and i y * ; Step 2: Obtaining the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms, wherein step 2 includes: Step 2-1: Use the current sensor to detect in real time and obtain the real-time value of the X and Y axis suspension winding current i x and i y ; Step 2-2: The given value i of the suspension winding current x * and i y * Respectively with its real-time value i x and i y Subtracting them, and then adjusting them through the proportional integral differential regulator, the duty ratios Dx and Dy of the X-axis and Y-axis suspension bridge arms are obtained; Step 3: adjusting the suspension force, said step 3 comprising: Step 3-1: To simplify the control, directly set the duty cycle D0 of the upper switch tube Q1 of the common bridge arm to 0.

5. At this time, the duty cycle of the lower switch tube Q2 of the bridge arm is (1-D0)=0.5; Step 3-2: Real-time adjustment of the duty cycle Dx and Dy of the X-axis and Y-axis suspension bridge arms, and then dynamically control the conduction time of the upper and lower switch tubes of the X-axis and Y-axis suspension bridge arms, so that the real-time value of the X-axis and Y-axis suspension winding current i x and i y Track its given value i respectively x * and i y * , thereby adjusting the radial suspension force in real time, the rotor (6) of the torque-decoupled permanent magnet biased bearingless switched reluctance motor can be stably suspended; Step 4: Obtain the reference value i of the three-phase torque winding current at low speed operation T * , and the opening angle θ at high speed operation on ; Step 4 comprises: Step 4-1: Using a position sensor to detect the position of the rotor (6) in real time, obtaining the position angle θ of the rotor (6), and obtaining the real-time value n of the rotation speed by calculation; Step 4-2: Set the critical speed of the low speed and high speed operating states to n0, whose value is determined by the motor operating condition; Step 4-3: When n≤n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the reference value i of the three-phase torque winding current T * ; At this time, in order to simplify the control, directly set the opening angle θ of each phase torque winding on and the turn-off angle θ off , and the values ​​of both are determined by the motor structure and working conditions; Step 4-4: When n>n0, the given value of the speed n * Subtract the real-time value n from it, and adjust it through the proportional integral controller to obtain the opening angle θ on ; At this time, directly set the cut-off angle θ off , whose value is determined by the motor structure and working conditions; Step 5: adjusting the torque; said step 5 comprises: Step 5-1: When n≤n0, use the current chopping control method to make the real-time value of the A, B, and C three-phase torque winding current i a 、i b 、i c Track their reference values ​​i respectively T * , and then adjust the three-phase torque winding current in real time, so as to: adjust the torque; Step 5-2: When n>n0, use the angle position control method to adjust the opening angle θ in real time on value, thereby dynamically controlling the torque.

5. The control method of a permanent magnet biased bearingless switched reluctance motor for torque decoupling according to claim 4, characterized in that: The method includes: when m=2, the number of phases of the torque winding of the motor changes from three to two.

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