Magnetic bearing system and control method, device, equipment, storage medium and product thereof

Abstract

The application discloses a kind of control method, device, magnetic bearing system, equipment, storage medium and computer program product of magnetic bearing system, the method comprises: in the case where the magnetic bearing system operates, the displacement of rotor in the magnetic bearing system is acquired, and the rotational speed of the rotor is acquired;According to the displacement of the rotor, and the rotational speed of the rotor, it is determined whether the rotor collides with the protection bearing in the magnetic bearing system;If it is determined that the rotor has collided with the protection bearing, the magnetic bearing in the magnetic bearing system is controlled to increase the iron loss torque of the rotor, so that the rotational speed of the rotor is reduced.The scheme, by accelerating rotor stop when rotor collision occurs, protects rotor and protection bearing, improves the reliability of magnetic bearing system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of magnetic bearing system (i.e. magnetic levitation bearing system), and particularly relates to a control method and device of a magnetic bearing system, a magnetic bearing system, equipment (such as a magnetic levitation motor and a magnetic levitation compressor), a storage medium and a computer program product, and more particularly relates to a collision control method and device of a magnetic levitation bearing system, a magnetic levitation bearing system, equipment (such as a magnetic levitation motor and a magnetic levitation compressor), a storage medium and a computer program product. BACKGROUND

[0002] The magnetic levitation motor suspends a rotor at a given position by using an electromagnetic bearing, so as to realize frictionless operation, and has the advantages of high rotation speed, low loss and maintenance-free. However, if the magnetic bearing system (i.e. magnetic levitation bearing system or magnetic bearing control system) is abnormal during operation of the magnetic levitation motor, the rotor will be unstable, which will cause damage to the rotor and the protection bearing and even damage the motor.

[0003] The above content is only used to assist in understanding the technical solutions of the present application, and does not represent the acknowledgement of the above content as prior art. SUMMARY

[0004] The present application aims to provide a control method and device of a magnetic bearing system, a magnetic bearing system, equipment (such as a magnetic levitation motor and a magnetic levitation compressor), a storage medium and a computer program product, so as to solve the problem that if the magnetic bearing system is abnormal during operation of the magnetic levitation motor, the rotor will be unstable, which will cause damage to the rotor and the protection bearing and even damage the motor, and achieve the effect of protecting the rotor and the protection bearing by accelerating the rotor to stop when the rotor collides, and improving the reliability of the magnetic bearing system.

[0005] The present application provides a control method of a magnetic bearing system, the magnetic bearing system comprising a magnetic bearing, a rotor and a protection bearing; the control method of the magnetic bearing system comprising: acquiring the displacement of the rotor and the rotation speed of the rotor in the case that the magnetic bearing system is running; determining whether the rotor collides with the protection bearing according to the displacement of the rotor and the rotation speed of the rotor; and if it is determined that the rotor has collided with the protection bearing, controlling the magnetic bearing to increase the iron loss torque of the rotor, so as to reduce the rotation speed of the rotor.

[0006] In some embodiments, determining whether the rotor collides with the protection bearing according to the displacement of the rotor and the rotating speed of the rotor comprises: determining a rotating speed interval corresponding to the rotating speed of the rotor, denoted as a current rotating speed interval of the rotor; and determining a corresponding displacement protection number according to the current rotating speed interval of the rotor, denoted as a current displacement protection number of the rotor; wherein different rotating speed intervals correspond to different displacement protection numbers; determining whether the displacement of the rotor is greater than a preset threshold within a set time period; if yes, accumulating the number of times that the displacement of the rotor is greater than the preset threshold to obtain an accumulated number of times that the displacement of the rotor is greater than the preset threshold; determining whether the rotating speed of the rotor is zero; if it is determined that the rotating speed of the rotor is zero, controlling the rotor to float; if it is determined that the rotating speed of the rotor is not zero, determining whether the accumulated number of times that the displacement of the rotor is greater than the preset threshold is greater than or equal to the current displacement protection number of the rotor; if yes, it is determined that the rotor has collided with the protection bearing; otherwise, it is determined that the rotor has not collided with the protection bearing.

[0007] In some embodiments, the magnetic bearing has coils, and the number of coils in the magnetic bearing is more than one; and controlling the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotating speed of the rotor comprises: controlling the current of the more than one coils in the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotating speed of the rotor.

[0008] In some embodiments, controlling the current of the more than one coils in the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotating speed of the rotor comprises: controlling each of the more than one coils in the magnetic bearing to output a preset fixed current to increase the iron loss torque of the rotor to reduce the rotating speed of the rotor; wherein the preset fixed current is a maximum current that the magnetic bearing can carry at least for a certain length of time.

[0009] In some embodiments, controlling the current of the more than one coils in the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotating speed of the rotor further comprises: if the arrangement mode of the more than one coils in the magnetic bearing is an NSSN arrangement mode driven by a full-bridge power amplifier, controlling the output current direction of the full-bridge power amplifier of the more than one coils in the magnetic bearing to be a preset direction, so that the arrangement mode of the more than one coils in the magnetic bearing changes from the NSSN arrangement mode to the NSNS arrangement mode, to increase the remagnetization frequency of the magnetic bearing, increase the iron loss torque of the rotor, and reduce the rotating speed of the rotor.

[0010] In some embodiments, the method further comprises: after controlling the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor, until the rotation speed of the rotor is reduced to a preset rotation speed range, re-controlling the rotor to be suspended, and then returning to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor, and repeating the above steps.

[0011] According to the above method, the application provides a control device of a magnetic bearing system. The magnetic bearing system comprises a magnetic bearing, a rotor and a protective bearing. The control device of the magnetic bearing system comprises an acquisition unit configured to acquire the displacement of the rotor and the rotation speed of the rotor when the magnetic bearing system is running; and a control unit configured to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor. The control unit is further configured to control the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor if it is determined that the rotor collides with the protective bearing.

[0012] In some embodiments, the control unit determines whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor, which comprises: determining a rotation speed range corresponding to the rotation speed of the rotor, denoted as the current rotation speed range of the rotor; and determining a corresponding displacement protection number according to the current rotation speed range of the rotor, denoted as the current displacement protection number of the rotor. Different rotation speed ranges correspond to different displacement protection numbers. The control unit determines whether the displacement of the rotor is greater than a preset threshold within a set time period. If yes, the number of times that the displacement of the rotor is greater than the preset threshold is accumulated to obtain an accumulated number of times that the displacement of the rotor is greater than the preset threshold. The control unit determines whether the rotation speed of the rotor is zero. If yes, the rotor is controlled to be suspended. If no, the control unit determines whether the accumulated number of times that the displacement of the rotor is greater than the preset threshold is greater than or equal to the current displacement protection number of the rotor. If yes, it is determined that the rotor collides with the protective bearing. If no, it is determined that the rotor does not collide with the protective bearing.

[0013] In some embodiments, the magnetic bearing has a coil, and the number of coils in the magnetic bearing is more than one. The control unit controls the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor by controlling the current of more than one coil in the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor.

[0014] In some embodiments, the control unit controls the current of the one or more coils of the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor, including: controlling each of the one or more coils of the magnetic bearing to output a preset fixed current to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor; wherein the preset fixed current is the maximum current that the magnetic bearing can carry for at least a certain duration.

[0015] In some embodiments, the control unit controls the current of the one or more coils of the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor, further including: if the arrangement of the one or more coils of the magnetic bearing is an NSSN arrangement driven by a full-bridge power amplifier, controlling the output current direction of the full-bridge power amplifier of the one or more coils of the magnetic bearing to be a preset direction, so that the arrangement of the one or more coils of the magnetic bearing changes from the NSSN arrangement to the NSNS arrangement, to increase the remagnetization frequency of the magnetic bearing, increase the iron loss torque of the rotor, and reduce the rotation speed of the rotor.

[0016] In some embodiments, further including: the control unit is further configured to, after controlling the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor, until the rotation speed of the rotor is reduced to a preset rotation speed range, re-control the rotor to be suspended, and then return to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor, to form a cycle.

[0017] To match the above device, the present application further provides a magnetic bearing system, including: the control device of the magnetic bearing system described above.

[0018] To match the above device, the present application further provides a magnetic bearing device, including: the control device of the magnetic bearing system described above, or the magnetic bearing system described above; wherein the magnetic bearing device is a magnetic levitation motor or a magnetic levitation compressor.

[0019] To match the above method, the present application further provides a storage medium, including a stored program, wherein when the program runs, the device where the storage medium is located executes the steps of the control method of the magnetic bearing system described above.

[0020] To match the above method, the present application further provides a computer program product, including a computer program, which is executed by a processor to realize the steps of the control method of the magnetic bearing system described above.

[0021] Therefore, the scheme of the present application judges whether the rotor collides according to the displacement and rotating speed of the rotor by aiming at the magnetic suspension bearing system, and controls the coils of the magnetic bearing to output fixed current until the rotating speed of the rotor drops to a preset rotating speed interval and then controls the rotor to suspend again in the case of judging that the rotor collides; thus, the rotor and the bearing are protected by accelerating the rotor to stop when the rotor collides, and the reliability of the magnetic bearing system is improved.

[0022] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application.

[0023] The technical scheme of the present application will be described in detail below with the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The flow chart of an embodiment of the control method of the magnetic bearing system of the present application;

[0025] Figure 2 The flow chart of an embodiment of determining whether the rotor collides with the protection bearing in the method of the present application;

[0026] Figure 3 The structure diagram of an embodiment of the control device of the magnetic bearing system of the present application;

[0027] Figure 4 The structure diagram of the structure of the active radial magnetic bearing;

[0028] Figure 5 The structure diagram of the arrangement form of the magnetic pole of the radial magnetic bearing, wherein (a) is the structure diagram of the arrangement form of the NSSN, and (b) is the structure diagram of the arrangement form of the NSNS;

[0029] Figure 6 The curve diagram of the relationship between the magnetic flux density B and the magnetic motive force NI;

[0030] Figure 7 The structure diagram of the power amplifier, wherein (a) is the structure diagram of the half-bridge power amplifier, and (b) is the structure diagram of the full-bridge power amplifier;

[0031] Figure 8 The flow chart of the collision control method of the magnetic suspension bearing system.

[0032] In combination with the drawings, the reference signs in the embodiments of the present application are as follows:

[0033] 1-magnetic bearing; 2-rotor; 3-protection bearing; 102-acquisition unit; 104-control unit. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and corresponding drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] It should be taken into consideration that during the operation of the magnetic levitation motor, if there are abnormal conditions such as mismatch of magnetic bearing control system parameters, hardware circuit failure, or the rotor is suddenly subjected to an external disturbance force greater than the maximum bearing capacity of the magnetic bearing, the rotor will become unstable, resulting in violent collision and friction between the rotor and the protective bearing at high speed, causing loss of protective bearing life or even damage to the motor.

[0036] Therefore, the solution of the present invention proposes a control method for a magnetic bearing system, specifically a collision control method for a magnetic levitation bearing system, which controls the magnetic bearing to provide different control schemes according to the degree of rotor instability collision, accelerates the rotor deceleration when instability occurs, reduces the loss caused by rotor instability and collision friction with the protective bearing, increases the life of the protective bearing, and improves the reliability of the magnetic levitation motor and magnetic levitation compressor.

[0037] According to an embodiment of the present invention, a control method for a magnetic bearing system is provided, such as Figure 1 The flow chart of an embodiment of the method of the present invention is shown in FIG. The magnetic bearing system comprises: a magnetic bearing, a rotor and a protective bearing; the rotor is as follows Figure 4 The rotor 2 shown in FIG. Figure 4 The magnetic bearing 1 shown, protects the bearing as Figure 4 The protective bearing 3 shown; Figure 4 Figure 1 is a schematic diagram of the structure of an active radial magnetic bearing. Figure 4 The active radial magnetic bearing structure shown in FIG. 1 comprises a magnetic bearing 1, a rotor 2 and a protective bearing 3; Figure 4 In the active radial magnetic bearing structure shown, the air gap between the rotor (i.e., rotor 2) and the protective bearing (i.e., protective bearing 3) in the suspended state is δ. In the solution of the present invention, Figure 1 As shown, the control method of the magnetic bearing system includes: steps S110 to S130.

[0038] In step S110 , when the magnetic bearing system is in operation, the displacement of the rotor and the rotational speed of the rotor are obtained.

[0039] In step S120 , it is determined whether the rotor collides with the protection bearing according to the displacement of the rotor and the rotation speed of the rotor.Figure 8 A flowchart of a collision control method for a magnetic bearing system is shown. As shown in the figure, the collision control method for a magnetic bearing system comprises: step 1, judging whether the rotor has collided, and then performing step 2. Figure 8

[0040] At step S130, if it is determined that the rotor has collided with the protective bearing, the magnetic bearing is controlled to increase the iron loss torque of the rotor, so that the rotation speed of the rotor is reduced, specifically, the current of the coil in the magnetic bearing is controlled to reduce the rotation speed of the rotor. Of course, after determining whether the rotor has collided with the protective bearing, if it is determined that the rotor has not collided with the protective bearing, the magnetic bearing system is maintained to operate, and returns to determine whether the rotor has collided with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor. The scheme of the present application uses the braking torque caused by the iron loss to accelerate the rotor to stop. As shown in the figure, the collision control method for a magnetic bearing system further comprises: step 2, controlling the magnetic bearing to increase the iron loss of the rotor to accelerate the rotor to reduce the speed, and then performing step 3. Figure 8

[0041] The scheme of the present application proposes a collision control scheme for a magnetic bearing system. Different control schemes are given according to the degree of rotor instability collision to control the magnetic bearing, so as to reduce the loss caused by rotor instability and protective bearing collision. In this way, the rotor is accelerated to reduce the speed when instability occurs, the loss caused by rotor instability and protective bearing collision is reduced, the service life of the protective bearing is increased, and the reliability of the magnetic suspension motor is improved. In the case where the magnetic suspension compressor comprises the magnetic suspension motor, the reliability of the magnetic suspension motor and the magnetic suspension compressor is also improved.

[0042] In some embodiments, the specific process of determining whether the rotor has collided with the protective bearing according to the displacement of the rotor and the rotation speed of the rotor in step S120 is described in the following example.

[0043] The following describes an embodiment of the method for determining whether the rotor has collided with the protective bearing in the present application, and further describes the specific process of determining whether the rotor has collided with the protective bearing in step S120, comprising steps S210 to S250. Figure 2 Step S210, determining the rotation speed interval corresponding to the rotation speed of the rotor, denoted as the current rotation speed interval of the rotor, and determining the corresponding displacement protection times according to the current rotation speed interval of the rotor, denoted as the current displacement protection times of the rotor; wherein different rotation speed intervals correspond to different displacement protection times.

[0044]

[0045] ​​​Step S220, determining whether the displacement of the rotor is greater than the preset threshold value within a set time period: if yes, counting the number of times that the displacement of the rotor is greater than the preset threshold value to obtain the cumulative number of times that the displacement of the rotor is greater than the preset threshold value; otherwise, not counting the number of times that the displacement of the rotor is greater than the preset threshold value.

[0046] Step S230, determining whether the rotating speed of the rotor is zero.

[0047] Step S240, if it is determined that the rotating speed of the rotor is zero, controlling the rotor to stop floating.

[0048] Step S250, if it is determined that the rotating speed of the rotor is not zero, determining whether the cumulative number of times that the displacement of the rotor is greater than the preset threshold value is greater than or equal to the current displacement protection number of the rotor: if yes, determining that the rotor has collided with the protection bearing; otherwise, determining that the rotor has not collided with the protection bearing.

[0049] As shown in Figure 8 , the collision control method of the magnetic suspension bearing system further comprises: in step 1, measuring the rotor displacement x and the rotating speed R in real time, judging the rotating speed interval [R n , R n-1 ] and obtaining the preset displacement protection number P n of the rotating speed interval, as shown in Table 1. Determining whether the rotating speed of the rotor is not zero: if it is determined that the rotating speed of the rotor is zero, stopping the rotor from floating; if it is determined that the rotating speed of the rotor is not zero, when the number of times that the displacement value is greater than the protection threshold value δ1 is detected within a time period T is greater than or equal to the preset number P n , judging that the rotor collides with the protection bearing, at this time, the frequency converter will receive a stop command, the frequency converter will no longer drag the rotor to rotate, the rotor is in the state of free fall, and step 2 is entered. The protection threshold value δ1 is different from the air gap δ between the rotor 2 and the protection bearing (i.e. the protection bearing 3) in the floating state, because the protection bearing has a clearance, when the collision occurs, the rotor displacement value is likely to be greater than the bearing air gap δ, and the specific value needs to be considered considering the clearance size of the protection bearing. Therefore, in order to ensure the accuracy of the collision judgment, the value of the protection threshold value δ1 is slightly greater than or equal to the protection bearing air gap δ.

[0050] Table 1

[0051]

[0052] For example: the rotor runs at 500 Hz, the time period T is 10 ms, the displacement sampling frequency is 10k, and the rotating speed interval and the displacement protection number can be as follows:

[0053] Speed interval Displacement protection times [500，400] 8 [400，300] 6 [300，200] 4 [200，100] 2 [100，0] 1

[0054] The rotor displacement x is measured in real time, and specifically, a displacement sensor can be used for the measurement. When the rotor approaches or moves away from the displacement sensor, the output voltage of the displacement sensor changes, and the magnetic bearing control system measures the displacement by using the change of the output voltage of the displacement sensor.

[0055] In the scheme, the rotor displacement and the rotor speed are used to accurately determine whether the rotor collides with the protection bearing, and when it is determined that the rotor has collided with the protection bearing, the rotor speed is accelerated to reduce the loss caused by the rotor instability and the friction between the rotor and the protection bearing, increase the service life of the protection bearing, and improve the reliability of the magnetic suspension motor and the magnetic suspension compressor.

[0056] In some embodiments, the magnetic bearing has a coil, and the number of coils in the magnetic bearing is more than one. The step S130 of controlling the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotor speed includes: controlling the current of the more than one coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotor speed.

[0057] In the scheme, when it is determined that the rotor is unstable, the current I output by each coil of the magnetic bearing is controlled to generate a large magnetic flux density, the iron loss braking torque of the magnetic bearing is increased to accelerate the rotor to stop, and when the rotor speed drops to a given speed, the rotor suspension control is restored. Thus, the loss caused by the rotor instability and the friction between the rotor and the protection bearing is reduced, the service life of the protection bearing is increased, and the reliability of the magnetic suspension motor and the magnetic suspension compressor is improved.

[0058] In some embodiments, the step of controlling the current of the more than one coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotor speed includes: controlling each of the more than one coils in the magnetic bearing to output a preset fixed current to increase the iron loss torque of the rotor and reduce the rotor speed; wherein the preset fixed current is the maximum current that the magnetic bearing can carry at least for a certain period of time.

[0059] As Figure 8As shown, the collision control method of the magnetic bearing system also includes: in step 2, controlling each coil of the magnetic bearing to output a fixed current I to generate a large magnetic flux density. Since the rotor is still rotating, the rotor will pass through the magnetic field generated by each magnetic pole in turn, and the generated iron loss braking torque accelerates the rotor to stop. During normal suspension, the current generated by the magnetic bearing is less than the maximum current value I. Because the greater the magnetic flux density, the better the braking effect, I can be selected as the maximum current value that the magnetic bearing is designed to carry for a long time. Controlling each coil of the magnetic bearing to output a fixed current I is to simultaneously control each coil of the magnetic bearing to output a fixed current I, that is, to make each coil of the magnetic bearing output a fixed current I at the same time.

[0060] In the solution of the present invention, when the rotor becomes unstable, the output current I of each coil of the magnetic bearing is controlled to generate a large magnetic flux density, and the rotor will pass through the magnetic field generated by each magnetic pole in turn, and the generated iron loss braking torque accelerates the rotor to stop. In this way, by increasing the iron loss braking torque of the magnetic bearing to accelerate the rotor to stop, the loss caused by rotor instability to the protective bearing and the rotor is reduced, the service life of the protective bearing is increased, and the reliability of the magnetic levitation motor and the magnetic levitation compressor is improved.

[0061] In some embodiments, controlling the current of one or more coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the speed of the rotor also includes: if the arrangement of one or more coils in the magnetic bearing is an NSSN arrangement driven by a full-bridge power amplifier, then controlling the output current direction of the full-bridge power amplifier of the one or more coils in the magnetic bearing to a preset direction, so that the arrangement of the one or more coils in the magnetic bearing is changed from an NSSN arrangement to an NSNS arrangement, thereby increasing the remagnetization frequency of the magnetic bearing, increasing the iron loss torque of the rotor, and reducing the speed of the rotor.

[0062] Generally, magnetic bearings cannot change the direction of the magnetic poles. However, if the magnetic bearings are arranged in an NSSN arrangement where the magnetic poles can be changed, the direction of the current in the magnetic bearing coil can be controlled so that the magnetic poles become arranged in an NSNS arrangement, thereby increasing the remagnetization frequency and the iron loss torque.

[0063] like Figure 8 As shown, the collision control method of the magnetic bearing system further includes: in step 2, Figure 7 The following are the schematic diagrams of the power amplifier structure, where (a) is the schematic diagram of the half-bridge power amplifier structure, and (b) is the schematic diagram of the full-bridge power amplifier structure. Commonly used power amplifiers include half-bridge power amplifiers and full-bridge power amplifiers, such as Figure 7 As shown, a half-bridge amplifier can only output current in one direction, while a full-bridge amplifier can output current in both directions. If the NSSN magnetic bearings driven by a full-bridge amplifier are arranged, the output current direction of the amplifier can be controlled according to Figure 5In (b), the magnetic poles are changed to NSNS arrangement, thereby increasing the remagnetization frequency and increasing the iron loss torque. The current amplitude is selected as the maximum current value I that can be long-term carried in the magnetic bearing design, and step 3 is entered. The power amplifier output current direction is as shown in Figure 5 The current flow direction of the NS level marked in (b).

[0064] Figure 5 The structure schematic diagram of the radial magnetic bearing magnetic pole arrangement form is shown in (a) NSSN arrangement form and (b) NSNS arrangement form. Figure 5 The NSSN and NSNS magnetic pole arrangement forms of the radial magnetic bearing are shown in (a) and (b). The magnetic pole arrangement form is determined when the magnetic bearing is designed, and the magnetic bearings designed in the NSSN and NSNS magnetic pole arrangement forms are different in structure. For the actual magnetic pole arrangement form, the current direction flowing through the magnetic bearing coil is related, as shown in Figure 5 The · symbol indicates that the current direction is outflow, and the × symbol indicates that the current direction is inflow; the remagnetization frequency of the NSNS magnetic pole arrangement form is twice that of the NSSN magnetic pole arrangement form.

[0065] When the rotor rotates, the N and S magnetic poles will alternately excite, thereby generating iron loss. When the magnetic bearing and the rotor are completed, the main factors affecting the surface iron loss of the rotor are the frequency of the repeated magnetization of the rotor core material and the amplitude of the magnetic flux density B. The repeated magnetization frequency is related to the rotor speed, and the remagnetization frequency of the magnetic bearing in the NSNS magnetic pole arrangement form is twice that of the magnetic bearing in the NSSN magnetic pole arrangement form. Figure 6 The relationship curve between the magnetic flux density B and the magnetic motive force NI (NI is the symbol of the magnetic motive force) is shown in the schematic diagram. The magnetic flux density amplitude is related to the current I passing through the magnetic bearing, and N is the number of turns of the magnetic bearing coil.

[0066] When the rotor loses stability and collides with the protection bearing, the frequency converter will receive an instruction to immediately stop. In the most serious case, from the beginning of the rotor losing stability to the rotor stopping and receiving the stop floating instruction, the rotor and the protection bearing are always colliding and rubbing. Therefore, when the rotor suspension loses stability, accelerating the rotor to stop helps to reduce the wear of the protection bearing and the rotor.

[0067] In some embodiments, the control method of the magnetic bearing system according to the scheme of the present application further comprises: in step S130, controlling the magnetic bearing to increase the iron loss torque of the rotor, and after the speed of the rotor is reduced, re-controlling the rotor to float after the speed of the rotor is reduced to a preset speed interval, and then returning to determine whether the rotor collides with the protection bearing according to the displacement of the rotor and the speed of the rotor, and repeating the cycle. As shown in Figure 8As shown, the collision control method of the magnetic bearing system further includes: step 3, when the rotor speed decreases to a preset range [R n-1 ,R n-2 ], resuspend the rotor.

[0068] In step 3, when the rotor speed decreases to the preset range [R n-1 ,R n-2 ], the magnetic bearing controls the rotor suspension again and repeats step 1 to determine whether the rotor can be stably suspended. If the rotor can be stably suspended, the magnetic bearing continues to control the rotor suspension and rotates until the rotor stops.

[0069] If the rotor cannot be stably suspended, go to step 2 until the speed reaches the preset range [R n-2 ,R n-3 ], the magnetic bearing controls the rotor suspension again, and then repeats step 1 to determine whether the rotor can be stably suspended, until the rotor stops rotating and finally stops floating.

[0070] The solution of the present invention involves a solution for handling instability or collision of a magnetic bearing rotor. The magnetic bearing is used to generate eddy current torque to accelerate the rotor to stop when the rotor collides, thereby reducing the loss of the protective bearing caused by rotor instability, increasing the service life of the protective bearing, and improving the reliability of the magnetic levitation motor and magnetic levitation compressor.

[0071] By adopting the technical solution of this embodiment, the magnetic bearing system is used to determine whether the rotor has collided based on the rotor's displacement and speed. If it is determined that the rotor has collided, the magnetic bearing coils are controlled to output a fixed current until the rotor speed drops to a preset speed range and then the rotor suspension is controlled again. Therefore, by accelerating the rotor to stop when the rotor collides, the rotor and the protective bearing are protected, thereby improving the reliability of the magnetic bearing system.

[0072] According to an embodiment of the present invention, a control device for a magnetic bearing system corresponding to the control method for the magnetic bearing system is also provided. Figure 3 The structure diagram of an embodiment of the device of the present invention is shown in FIG. The magnetic bearing system includes: a magnetic bearing, a rotor and a protective bearing; the rotor is as shown in FIG. Figure 4 The rotor 2 shown in FIG. Figure 4 The magnetic bearing 1 shown, protects the bearing as Figure 4 The protective bearing 3 shown; Figure 4 Figure 1 is a schematic diagram of the structure of an active radial magnetic bearing. Figure 4 The active radial magnetic bearing structure shown in FIG. 1 comprises a magnetic bearing 1, a rotor 2 and a protective bearing 3; Figure 4The active radial magnetic bearing structure shown, the air gap between the rotor (i.e. rotor 2) and the protective bearing (i.e. protective bearing 3) in the suspended state is δ. In the scheme of the present application, as shown Figure 3 The control device of the magnetic bearing system includes an acquisition unit 102 and a control unit 104.

[0073] The acquisition unit 102 is configured to acquire the displacement of the rotor and the rotational speed of the rotor when the magnetic bearing system is running. For specific functions and processes of the acquisition unit 102, see step S110.

[0074] The control unit 104 is configured to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotational speed of the rotor. For specific functions and processes of the control unit 104, see step S120. Figure 8 A flowchart of a collision control method for a magnetic suspension bearing system is shown. As shown in Figure 8 The collision control method for a magnetic suspension bearing system includes step 1, determining whether the rotor collides, and then performing step 2.

[0075] The control unit 104 is further configured to control the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotational speed of the rotor if it is determined that the rotor has collided with the protective bearing. Specifically, the current of the coil in the magnetic bearing is controlled to reduce the rotational speed of the rotor. Of course, the control unit 104 is also configured to maintain the operation of the magnetic bearing system and return to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotational speed of the rotor if it is determined that the rotor does not collide with the protective bearing. For specific functions and processes of the control unit 104, see step S130. The scheme of the present application uses the braking torque caused by iron loss to accelerate the rotor to stop. As shown in Figure 8 The collision control method for a magnetic suspension bearing system also includes step 2, controlling the magnetic bearing to increase the iron loss of the rotor to accelerate the rotor to reduce speed, and then performing step 3.

[0076] The collision control scheme for a magnetic suspension bearing system proposed by the scheme of the present application controls the magnetic bearing to give different control schemes according to the degree of rotor instability collision, reduces the loss brought by rotor instability to the rotor and the protective bearing; in this way, the rotor is accelerated to reduce speed when it is unstable, the loss brought by rotor instability collision and friction of the protective bearing is reduced, the life of the protective bearing is increased, the reliability of the magnetic suspension motor is improved, and in the case of a magnetic suspension compressor including the magnetic suspension motor, the reliability of the magnetic suspension motor and the magnetic suspension compressor is also improved.

[0077] In some embodiments, the control unit 104 determines whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotational speed of the rotor, including:

[0078] The control unit 104 is further configured to determine a speed range corresponding to the rotor's speed, which is recorded as the rotor's current speed range; and determine a corresponding number of displacement protections based on the rotor's current speed range, which is recorded as the rotor's current displacement protection number; different speed ranges correspond to different displacement protection numbers. The specific functions and processing of the control unit 104 are further described in step S210.

[0079] The control unit 104 is further configured to determine whether the rotor displacement is greater than a preset threshold within a set time period. If so, the control unit 104 accumulates and counts the number of times the rotor displacement is greater than the preset threshold to obtain a cumulative number of times the rotor displacement is greater than the preset threshold. Otherwise, the control unit 104 does not accumulate and count the number of times the rotor displacement is greater than the preset threshold. The specific functions and processing of the control unit 104 are further described in step S220.

[0080] The control unit 104 is further configured to determine whether the rotational speed of the rotor is zero. The specific functions and processing of the control unit 104 are also described in step S230.

[0081] The control unit 104 is further configured to control the rotor to stop floating if it is determined that the rotation speed of the rotor is zero. The specific functions and processing of the control unit 104 are also shown in step S240.

[0082] The control unit 104 is further configured to, if it is determined that the rotor speed is not zero, determine whether the cumulative number of times the rotor displacement exceeds a preset threshold is greater than or equal to the rotor's current displacement protection count; if so, determine that the rotor has collided with the protection bearing; otherwise, determine that the rotor has not collided with the protection bearing. The specific functions and processing of the control unit 104 are further described in step S250.

[0083] like Figure 8 As shown, the collision control method of the magnetic bearing system further includes: in step 1, measuring the rotor displacement x and the speed R in real time, and determining the speed range [R n , R n-1 ], and obtain the displacement protection times P of the preset speed range n , as shown in Table 1. Determine whether the rotor speed is not zero: if the rotor speed is determined to be zero, then stop the rotor; if the rotor speed is determined to be non-zero, then the number of times the displacement value is greater than the protection threshold δ1 within the time period T is greater than or equal to the preset number P nWhen the rotor collides with the protective bearing, the frequency converter receives a stop command, and the frequency converter no longer drags the rotor to rotate, and the rotor is in a free-fall state, and step 2 is entered.

[0084] Table I

[0085]

[0086] In the formula, the rotor displacement x is measured in real time, and the displacement sensor can be used for measurement. When the rotor approaches or moves away from the displacement sensor, the output voltage of the displacement sensor changes, and the magnetic bearing control system measures the displacement by using the change of the output voltage of the displacement sensor.

[0087] In the scheme, whether the rotor collides with the protective bearing can be accurately determined according to the rotor displacement and the rotor speed, and when it is determined that the rotor has collided with the protective bearing, i.e., the rotor is unstable, the rotor speed is accelerated to reduce the loss caused by the rotor instability and the collision friction of the protective bearing, the service life of the protective bearing is increased, and the reliability of the magnetic suspension motor is improved. In the case where the magnetic suspension compressor comprises the magnetic suspension motor, the reliability of the magnetic suspension motor and the magnetic suspension compressor is also improved.

[0088] In some embodiments, the magnetic bearing has a coil, and the number of coils in the magnetic bearing is more than one. The control unit 104 controls the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotor speed, including: the control unit 104 is specifically further configured to control the current of the more than one coil in the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotor speed.

[0089] In the scheme, when it is determined that the rotor is unstable, the control unit 104 controls the coils of the magnetic bearing to output a large magnetic flux density, increases the iron loss braking torque of the magnetic bearing to accelerate the rotor to stop, and restores the rotor suspension control when the rotor speed drops to a given speed; thereby, the loss caused by the rotor instability and the protective bearing is reduced, the service life of the protective bearing is increased, and the reliability of the magnetic suspension motor and the magnetic suspension compressor is improved.

[0090] In some embodiments, the control unit 104 controls the current of the more than one coil in the magnetic bearing to increase the iron loss torque of the rotor to reduce the rotor speed, including: the control unit 104 is specifically further configured to control each of the more than one coil in the magnetic bearing to output a preset fixed current to increase the iron loss torque of the rotor to reduce the rotor speed; wherein the preset fixed current is the maximum current that the magnetic bearing can carry at least for a certain period of time.

[0091] As Figure 8As shown, the collision control method for a magnetic bearing system further includes: in step 2, controlling each coil of the magnetic bearing to output a fixed current I to generate a high magnetic flux density. Since the rotor is still rotating, the rotor will alternately pass through the magnetic field generated by each magnetic pole, and the resulting iron loss braking torque accelerates the rotor to a standstill. During normal suspension, the current generated by the magnetic bearing is less than the maximum current value I. Because a higher magnetic flux density improves the braking effect, I can be selected from the maximum current value that the magnetic bearing is designed to carry over a long period of time.

[0092] In the solution of the present invention, when the rotor becomes unstable, the output current I of each coil of the magnetic bearing is controlled to generate a large magnetic flux density, and the rotor will pass through the magnetic field generated by each magnetic pole in turn, and the generated iron loss braking torque accelerates the rotor to stop. In this way, by increasing the iron loss braking torque of the magnetic bearing to accelerate the rotor to stop, the loss caused by rotor instability to the protective bearing and the rotor is reduced, the service life of the protective bearing is increased, and the reliability of the magnetic levitation motor and the magnetic levitation compressor is improved.

[0093] In some embodiments, the control unit 104 controls the current of one or more coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the speed of the rotor, and also includes: the control unit 104 is specifically configured to control the output current direction of the full-bridge power amplifier of the one or more coils in the magnetic bearing to a preset direction if the arrangement of the one or more coils in the magnetic bearing is an NSSN arrangement driven by a full-bridge power amplifier, so that the arrangement of the one or more coils in the magnetic bearing is changed from an NSSN arrangement to an NSNS arrangement, so as to increase the remagnetization frequency of the magnetic bearing, increase the iron loss torque of the rotor, and reduce the speed of the rotor.

[0094] Generally, magnetic bearings cannot change the direction of the magnetic poles. However, if the magnetic bearings are arranged in an NSSN arrangement where the magnetic poles can be changed, the direction of the current in the magnetic bearing coil can be controlled so that the magnetic poles become arranged in an NSNS arrangement, thereby increasing the remagnetization frequency and the iron loss torque.

[0095] like Figure 8 As shown, the collision control method of the magnetic bearing system further includes: in step 2, Figure 7 The following are the schematic diagrams of the power amplifier structure, where (a) is the schematic diagram of the half-bridge power amplifier structure, and (b) is the schematic diagram of the full-bridge power amplifier structure. Commonly used power amplifiers include half-bridge power amplifiers and full-bridge power amplifiers, such as Figure 7 As shown, a half-bridge amplifier can only output current in one direction, while a full-bridge amplifier can output current in both directions. If the NSSN magnetic bearings driven by a full-bridge amplifier are arranged, the output current direction of the amplifier can be controlled according to Figure 5(b) is shown to change the magnetic pole into NSNS arrangement, thereby increasing the remagnetization frequency, increasing the iron loss torque, the current amplitude is selected as the maximum current value I that the magnetic bearing design can bear for a long time, and step 3 is entered.

[0096] Figure 5 The structure schematic diagram of the radial magnetic bearing magnetic pole arrangement form is shown in (a) NSSN arrangement form and (b) NSNS arrangement form. Figure 5 The NSSN and NSNS magnetic pole arrangement forms of the radial magnetic bearing are shown in (a) and (b). The magnetic pole arrangement form is determined when the magnetic bearing is designed, and the magnetic bearings designed in the NSSN and NSNS magnetic pole arrangement forms are different in structure. For the actual magnetic pole arrangement form, it is related to the current direction flowing through the magnetic bearing coil, as shown in (a), the · symbol indicates that the current direction is outflow, and the × symbol indicates that the current direction is inflow; the remagnetization frequency of the NSNS magnetic pole arrangement form is twice that of the NSSN magnetic pole arrangement form. Figure 5

[0097] When the rotor rotates, the N and S magnetic poles will alternately excite, thereby generating iron loss. When the magnetic bearing and the rotor are completed, the main factors affecting the surface iron loss of the rotor are the frequency of the remagnetization of the rotor core material and the amplitude of the magnetic flux density B. The repeated magnetization frequency is related to the rotor speed, and the remagnetization frequency of the magnetic bearing in the NSNS magnetic pole arrangement form is twice that of the magnetic bearing in the NSSN magnetic pole arrangement form. Figure 6 The relationship curve between the magnetic flux density B and the magnetomotive force NI is shown in (a), the magnetic flux density amplitude is related to the current I passing through the magnetic bearing, and N is the number of turns of the magnetic bearing coil.

[0098] When the rotor loses stability and collides with the protection bearing, the frequency converter will receive an instruction to immediately stop, and in the most serious case, from the beginning of the rotor losing stability to the rotor stopping and receiving the stop floating instruction, the rotor and the protection bearing are always colliding and rubbing, so when the rotor suspension loses stability, accelerating the rotor to stop helps to reduce the loss of the protection bearing and the rotor.

[0099] In some embodiments, the control method of the magnetic bearing system according to the scheme of the present application further comprises: the control unit 104 is further configured to, after controlling the magnetic bearing to increase the iron loss torque of the rotor and reduce the speed of the rotor, re-control the suspension of the rotor until the speed of the rotor is reduced to a preset speed range, and then return to determine whether the rotor collides with the protection bearing according to the displacement of the rotor and the speed of the rotor, and cycle in this way. As shown in (a), the collision control method of the magnetic suspension bearing system further comprises: step 3, when the speed of the rotor is reduced to the preset range [R Figure 8 n-1 ,R n-2 ​​When the rotor speed is reduced to the preset interval [R

[0100] In step 3, when the rotor speed is reduced to the preset interval [R n-1 ,R n-2 ], the magnetic bearing re-controls the rotor suspension, and step 1 is repeated to determine whether the rotor can be stably suspended. If the rotor can be stably suspended, the magnetic bearing continuously controls the rotor suspension and falls to stop floating when the rotor stops.

[0101] If the rotor cannot be stably suspended, step 2 is entered, and the rotor speed is reduced to the preset interval [R n-2 ,R n-3 ] until the magnetic bearing re-controls the rotor suspension. Step 1 is repeated to determine whether the rotor can be stably suspended until the rotor stops floating when the rotor stops.

[0102] In the scheme of the present application, when the magnetic suspension bearing rotor loses stability or collides, the eddy current torque generated by the magnetic bearing is used to accelerate the rotor to stop, reduce the loss of the protection bearing caused by the rotor losing stability, increase the service life of the protection bearing, and improve the reliability of the magnetic suspension motor and the magnetic suspension compressor.

[0103] Since the processing and functions realized by the device of the present embodiment basically correspond to the embodiments, principles and examples of the foregoing method, details not described in the description of the present embodiment can be referred to the related descriptions in the foregoing embodiments, which will not be repeated here.

[0104] According to the embodiments of the present application, a magnetic bearing system corresponding to the control device of the magnetic bearing system is also provided. The magnetic bearing system can include the control device of the magnetic bearing system described above.

[0105] Since the processing and functions realized by the magnetic bearing system of the present embodiment basically correspond to the embodiments, principles and examples of the foregoing device, details not described in the description of the present embodiment can be referred to the related descriptions in the foregoing embodiments, which will not be repeated here.

[0106] According to the embodiments of the present application, a magnetic bearing device corresponding to the control device of the magnetic bearing system is also provided. The magnetic bearing device can include the control device of the magnetic bearing system described above, or the magnetic bearing system described above. The magnetic bearing device is a magnetic suspension motor or a magnetic suspension compressor.

[0107] Since the processing and functions realized by the magnetic bearing device of the present embodiment basically correspond to the embodiments, principles and examples of the foregoing device, details not described in the description of the present embodiment can be referred to the related descriptions in the foregoing embodiments, which will not be repeated here.

[0108] According to an embodiment of the present application, a computer program product corresponding to the control method of the magnetic bearing system is also provided, comprising a computer program which, when executed by a processor, implements the steps of the control method of the magnetic bearing system as described above.

[0109] Since the processing and functions realized by the product of the present embodiment are basically corresponding to the above-mentioned embodiments, principles and examples of the magnetic bearing system and the motor, the descriptions of the present embodiment which are not elaborated can be referred to the related descriptions in the above-mentioned embodiments, which will not be repeated here.

[0110] According to an embodiment of the present application, a storage medium corresponding to the control method of the magnetic bearing system is also provided, comprising a stored program, wherein when the program is running, the device where the storage medium is located executes the steps of the control method of the magnetic bearing system as described above.

[0111] Since the processing and functions realized by the storage medium of the present embodiment are basically corresponding to the above-mentioned embodiments, principles and examples of the method, the descriptions of the present embodiment which are not elaborated can be referred to the related descriptions in the above-mentioned embodiments, which will not be repeated here.

[0112] In summary, those skilled in the art can easily understand that the above-mentioned advantageous modes can be freely combined and superimposed without conflict.

[0113] The above only describes the embodiments of the present application and is not used to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A control method for a magnetic bearing system, characterized in that: The magnetic bearing system includes: a magnetic bearing, a rotor and a protective bearing; the control method of the magnetic bearing system includes: When the magnetic bearing system is in operation, obtaining the displacement of the rotor and the rotational speed of the rotor; Determine the speed interval corresponding to the speed of the rotor, which is recorded as the current speed interval of the rotor; and determine the corresponding displacement protection number according to the current speed interval of the rotor, which is recorded as the current displacement protection number of the rotor; wherein different speed intervals correspond to different displacement protection numbers; determine whether the displacement of the rotor is greater than a preset threshold within a set time period: if so, accumulate and count the number of times the displacement of the rotor is greater than the preset threshold to obtain the cumulative number of times the displacement of the rotor is greater than the preset threshold; determine whether the speed of the rotor is zero; if it is determined that the speed of the rotor is zero, control the rotor to stop floating; if it is determined that the speed of the rotor is not zero, determine whether the cumulative number of times the displacement of the rotor is greater than the preset threshold is greater than or equal to the current displacement protection number of the rotor: if so, determine that the rotor has collided with the protection bearing; otherwise, determine that the rotor has not collided with the protection bearing; If it is determined that the rotor has collided with the protective bearing, the magnetic bearing is controlled to increase the iron loss torque of the rotor to reduce the rotation speed of the rotor.

2. The control method of the magnetic bearing system according to claim 1, characterized in that: The magnetic bearing has a coil, and the number of coils in the magnetic bearing is more than one; Controlling the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotational speed of the rotor includes: The current of one or more coils in the magnetic bearing is controlled to increase the iron loss torque of the rotor and reduce the rotational speed of the rotor.

3. The control method of the magnetic bearing system according to claim 2, characterized in that: Controlling the current of one or more coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotational speed of the rotor includes: Controlling each of the one or more coils in the magnetic bearing to output a preset fixed current to increase the iron loss torque of the rotor and reduce the rotational speed of the rotor; The preset fixed current is the maximum current that the magnetic bearing can carry at least for a certain period of time.

4. The control method of the magnetic bearing system according to claim 2 or 3, characterized in that: The method further comprises controlling the current of one or more coils in the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotational speed of the rotor. If the arrangement of one or more coils in the magnetic bearing is an NSSN arrangement driven by a full-bridge power amplifier, the output current direction of the full-bridge power amplifier of the one or more coils in the magnetic bearing is controlled to be a preset direction, so that the arrangement of the one or more coils in the magnetic bearing is changed from an NSSN arrangement to an NSNS arrangement, thereby increasing the remagnetization frequency of the magnetic bearing, increasing the iron loss torque of the rotor, and reducing the speed of the rotor.

5. The control method of the magnetic bearing system according to any one of claims 1 to 3, characterized in that: Also includes: After controlling the magnetic bearing to increase the iron loss torque of the rotor and reducing the speed of the rotor, the rotor suspension is controlled again until the speed of the rotor drops to a preset speed range. Then, the control returns to determine whether the rotor collides with the protective bearing based on the displacement of the rotor and the speed of the rotor, and the cycle continues.

6. The control method of the magnetic bearing system according to claim 4, characterized in that: Also includes: After controlling the magnetic bearing to increase the iron loss torque of the rotor and reducing the speed of the rotor, the rotor suspension is controlled again until the speed of the rotor drops to a preset speed range. Then, the control returns to determine whether the rotor collides with the protective bearing based on the displacement of the rotor and the speed of the rotor, and the cycle continues.

7. A control device for a magnetic bearing system corresponding to the control method for a magnetic bearing system according to claim 1, characterized in that: The magnetic bearing system includes: a magnetic bearing, a rotor and a protective bearing; the control device of the magnetic bearing system includes: an acquisition unit, configured to acquire the displacement of the rotor and the rotational speed of the rotor when the magnetic bearing system is in operation; a control unit configured to determine whether the rotor collides with the protective bearing according to the displacement of the rotor and the rotational speed of the rotor; The control unit is further configured to control the magnetic bearing to increase the iron loss torque of the rotor and reduce the rotation speed of the rotor if it is determined that the rotor has collided with the protective bearing.

8. A magnetic bearing system, characterized in that: include: The control device for the magnetic bearing system according to claim 7.

9. A magnetic bearing device, characterized in that: include: The control device of the magnetic bearing system according to claim 7, or the magnetic bearing system according to claim 8; wherein the magnetic bearing device is a magnetic levitation motor or a magnetic levitation compressor.

10. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is executed, the device where the storage medium is located is controlled to execute the control method of the magnetic bearing system according to any one of claims 1 to 6.

11. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for controlling a magnetic bearing system according to any one of claims 1 to 6 are implemented.

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