A four-degree-of-freedom magnetic suspension bearing switch short circuit fault-tolerant topology circuit

Abstract

The application discloses a kind of four degrees of freedom magnetic suspension bearing short-circuit fault-tolerant topology circuit, belong to magnetic suspension bearing control field, this topology circuit uses two sets of reverse common bridge arm topology to control the A phase winding and C phase winding of four degrees of freedom magnetic suspension bearing respectively, and redundant design is carried out to bridge arm switch device.When short-circuit fault occurs to the switch device of one set of reverse common bridge arm topology, by adjusting the control direction of winding current of fault topology, it still has the ability to control bias current, another set of reverse common bridge arm topology controls bias current and control current simultaneously, so that the winding current of each degree of freedom of magnetic bearing can still generate stable electromagnetic force.The fault-tolerant topology and control method can effectively prevent the risk of high-speed rotor rubbing caused by winding current out of control due to switch short-circuit fault, and improve the fault-tolerant capability of magnetic suspension bearing system.

Description

Technical Field

[0001] This invention belongs to the field of magnetic levitation bearing control, and more specifically, relates to a switching short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing. Background Technology

[0002] Magnetic levitation bearings are bearing devices that use electromagnetic force to levitate the rotor, enabling contactless operation between the rotor and stator. They offer advantages such as no lubrication, no friction, and long service life, making them an excellent alternative to traditional mechanical bearings. Magnetic levitation bearings are widely used in centrifugal compressors, high-speed flywheels, vacuum molecular pumps, and other applications requiring high-speed rotor operation or a vacuum clean environment. An active magnetic levitation bearing system mainly includes a rotor, sensors, a controller, and a power amplifier. The power amplifier, as the core of electromechanical conversion, plays a crucial role in the entire system.

[0003] The power amplifier converts current commands into actual winding currents, thereby controlling the electromagnetic force of the magnetic bearing. If a short-circuit fault occurs in the switching device of the power amplifier topology, it will cause the voltage control of that arm to fail, resulting in the winding current deviating from the reference value. This can further lead to rotor instability, causing serious malfunctions such as rotor drop and system shutdown. A short-circuit fault refers to a faulty device remaining in a short-circuit state; in this case, the switching device remains in a conducting state, and the winding current will rise rapidly.

[0004] Existing fault-tolerant topologies used in power amplifiers for magnetic levitation bearings, such as Chinese patent application number CN202110305579.2, disclose a fault-tolerant control system for open-circuit faults in magnetic levitation bearing switches. This system can only solve the fault tolerance problem when the switching device experiences an open-circuit fault, but it cannot cope with short-circuit faults in the switching device. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a switching short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing. Its purpose is to utilize the redundant devices of the topology and switch the operating mode of the topology so that the winding current controlled by the faulty topology can quickly recover to a stable value. This enables the rotor to remain stably levitated when the switching devices of the power amplifier experience a short-circuit fault, thus avoiding serious faults such as rotor falling and system shutdown.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a switching short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing is provided, comprising:

[0007] The first fault-tolerant topology D1 includes windings A1-A4, the first and second non-common bridge arm groups B1 and B2, B3 and B4, and the common bridge arm B5;

[0008] The second fault-tolerant topology D2 includes windings C1-C4, the third and fourth non-common bridge arm groups B6 and B7, B8 and B9, and the common bridge arm B. 10 ;

[0009] In this configuration, the midpoints of B1-B4 are each connected to one end of A1-A4, and the other end of A1-A4 is connected to the midpoint of B5; the midpoints of B6-B9 are each connected to one end of C1-C4, and the other end of C1-C4 is connected to the midpoint of B5. 10 The midpoint; winding combinations A1 and C1, A2 and C2 are used to control the electromagnetic force of two degrees of freedom of the first magnetic levitation bearing, respectively; winding combinations A3 and C3, A4 and C4 are used to control the electromagnetic force of two degrees of freedom of the second magnetic levitation bearing, respectively; the upper and lower nodes of each bridge arm are respectively connected to the positive and negative terminals of the DC power supply, and both the upper and lower bridge arms include a controllable switch and a unidirectional conducting device connected in antiparallel to the controllable switch;

[0010] Both the first and second fault-tolerant topologies include normal mode and fault mode; in normal mode, for any non-common bridge arm B j The controllable switches of the upper and lower bridge arms alternately operate; the controllable switches of the upper bridge arms of each bridge arm in the first and third non-common bridge arm groups operate in the same state, while the controllable switches of the upper bridge arms of each bridge arm in the second and fourth non-common bridge arm groups operate in the same state and opposite to the controllable switches of the upper bridge arms of each bridge arm in the first and third non-common bridge arm groups. The reference current of the winding controlled by each fault-tolerant topology comes from the bias current and the control current; in any fault-tolerant topology D i Any non-public bridge arm B j When a short-circuit fault occurs in the controllable switch of the upper or lower bridge arm, D i Switch to fault mode, D i The controllable switches of the upper or lower arms of other non-common bridge arms remain in the open state, in conjunction with B. j The currents in the windings controlled by the non-common bridge arms in the same group are reversed, D i The reference current of the controlled winding is a constant bias current.

[0011] According to a second aspect of the present invention, a switching short-circuit fault-tolerant control method for a four-degree-of-freedom magnetic levitation bearing is provided, applied to the topology circuit as described in the first aspect, comprising:

[0012] S101, real-time detection of the current in A1-A4 and C1-C4, and calculation of the sum of the absolute values ​​of the current in the winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively;

[0013] S102, determine whether the sum of the absolute values ​​of the currents of any winding combination is greater than the first threshold T. If so, proceed to S103; otherwise, return to S101. Where T = 2I + k, I is the bias current of any winding, and k is the margin.

[0014] S103, locate the faulty bridge arm based on the change in modulation ratio of the current controller of each winding, wherein the faulty bridge arm is the bridge arm where the controllable switch that has experienced a short circuit fault is located.

[0015] S104, the fault-tolerant topology D where the faulty bridge arm is located i Switching from normal mode to fault mode enables D i The controllable switches of the upper or lower arms of other non-common bridge arms are all kept in the open state, so that B j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

[0016] According to a third aspect of the present invention, a switch short-circuit fault-tolerant control system for a four-degree-of-freedom magnetic levitation bearing is provided, characterized in that it includes: the topology circuit as described in the first aspect, a fault detection module, a PWM signal switching module, and a fault mode current controller.

[0017] The fault detection module is used to detect the current of A1-A4 and C1-C4 in real time, and calculate the sum of the absolute values ​​of the current of winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively. When the sum of the absolute values ​​of the current of any winding combination is greater than the first threshold T, the faulty bridge arm is located according to the modulation ratio change of the current controller of each winding, and is sent to the PWM signal switching module and the fault mode current controller through a fault-tolerant command. The faulty bridge arm is the bridge arm where the controllable switch that has a short-circuit fault is located, T = 2I + k, where I is the bias current of any winding and k is the margin.

[0018] The PWM signal switching module is used to determine the fault-tolerant topology D that needs to be switched to the fault mode according to the fault-tolerant command. i And through the drive signal, D i All controllable switches of the upper or lower arms of other non-common arms are kept in the off state;

[0019] The fault mode current controller is used to control the current with B according to the fault-tolerant command. j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

[0020] According to a fourth aspect of the invention, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing a processor to perform the method as described in the first aspect.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0022] 1. The short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing provided by this invention employs two sets of reverse common-arm topologies to control the A-phase and C-phase windings of the four-degree-of-freedom magnetic levitation bearing respectively, and redundancy is designed for the bridge arm switching devices. When a short-circuit fault occurs in the switching device of one set of reverse common-arm topologies, the winding current control direction of the faulty topology is adjusted so that it still has the ability to control the bias current. The other set of reverse common-arm topologies simultaneously controls the bias current and the control current, so that the winding current of each degree of freedom of the magnetic bearing can still generate a stable electromagnetic force. For the eight windings of a four-degree-of-freedom magnetic levitation bearing, only ten bridge arms are needed for control. Moreover, this fault-tolerant topology can simultaneously achieve fault tolerance for both short-circuit and open-circuit faults, and can be further extended to multiple degrees of freedom according to actual needs.

[0023] 2. The short-circuit fault-tolerant control method for a four-degree-of-freedom magnetic levitation bearing provided by this invention can promptly detect the occurrence of a short-circuit fault after the switching device experiences a short-circuit fault. By adjusting the winding current control direction of the faulty topology, it can still maintain the ability to control the bias current. Meanwhile, the fault-tolerant topology that has not experienced a fault simultaneously controls both the bias current and the control current, ensuring that the winding current of each degree of freedom of the magnetic bearing can still generate a stable electromagnetic force. This control method effectively prevents the winding current from running out of control when the switching device experiences a short-circuit fault, thereby reducing the risk of high-speed rotor rubbing. It also ensures stable rotor levitation even when the switching device experiences a short-circuit fault, improving the fault tolerance capability of the magnetic levitation bearing system and possessing high practical application value. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the short-circuit fault-tolerant topology of the four-degree-of-freedom magnetic levitation bearing switch provided in an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a four-degree-of-freedom magnetic levitation bearing structure provided in an embodiment of the present invention;

[0026] Figure 3A , 3B These are circuit topology diagrams of the four-degree-of-freedom magnetic levitation bearing switch short-circuit fault-tolerant topology 1 provided in the embodiments of the present invention in normal mode and fault mode.

[0027] Figure 4This is a flowchart of the fault-tolerant control method for short-circuit faults of a four-degree-of-freedom magnetic levitation bearing switch provided in an embodiment of the present invention;

[0028] Figure 5 This is a control block diagram of a switch short-circuit fault-tolerant system provided in an embodiment of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] This invention provides a switching short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing, such as... Figure 1 As shown, it includes:

[0031] First fault-tolerant topology D1, second fault-tolerant topology D2, and DC power supply V dc ;

[0032] The first fault-tolerant topology includes windings A1-A4, non-common bridge arms B1-B4 (B1 and B2, B3 and B4 are the first and second non-common bridge arm groups, respectively), and common bridge arm B5;

[0033] The first fault-tolerant topology includes windings C1-C4, non-common arms B6-B9 (B6 and B7, B8 and B9 are the third and fourth non-common arm groups, respectively), and common arm B. 10 ;

[0034] In this configuration, the midpoints of the non-common bridge arms B1-B4 are respectively connected to one end of windings A1-A4, and the other end of windings A1-A4 is connected to the midpoint of the common bridge arm B5; the midpoints of the non-common bridge arms B6-B9 are respectively connected to one end of windings C1-C4, and the other end of windings C1-C4 is connected to the common bridge arm B5. 10 The midpoint;

[0035] Windings A1 and C1 are used to control the electromagnetic force of one degree of freedom of the first magnetic levitation bearing; windings A2 and C2 are used to control the electromagnetic force of the other degree of freedom of the first magnetic levitation bearing.

[0036] Windings A3 and C3 are used to control the electromagnetic force of one degree of freedom of the second magnetic levitation bearing; windings A4 and C4 are used to control the electromagnetic force of the other degree of freedom of the second magnetic levitation bearing.

[0037] The non-public bridge arms B1-B4, B6-B9 and the public bridge arms B5, B10 The upper and lower nodes are respectively connected to the positive and negative terminals of the DC voltage source, and both the upper and lower bridge arms include a controllable switch and a unidirectional conducting device connected in antiparallel to the controllable switch.

[0038] That is, the topology circuit provided by the present invention includes 8 windings A1, A2, A3, A4, C1, C2, C3, C4, 8 non-common bridge arms B1, B2, B3, B4, B6, B7, B8, B9, 2 common bridge arms B5, B10 and 1 DC voltage source;

[0039] The midpoints of bridge arms B1, B2, B3, and B4 are connected to one end of windings A1, A2, A3, and A4, respectively, and the other ends of windings A1, A2, A3, and A4 are all connected to the midpoint of the common bridge arm B5; the midpoints of bridge arms B6, B7, B8, and B9 are connected to one end of windings C1, C2, C3, and C4, respectively, and the other ends of windings C1, C2, C3, and C4 are all connected to the midpoint of the common bridge arm B10; among them, windings A1 and C1 control the electromagnetic force of one degree of freedom of the four-degree-of-freedom magnetic bearing, and A2 and C2, A3 and C3, and A4 and C4 control the electromagnetic force of the other three degrees of freedom, respectively;

[0040] Specifically, such as Figure 2 As shown, the two radial magnetic levitation bearings are each controlled by eight windings, where windings A1 and C1 control the electromagnetic force F in the x-direction of the first radial magnetic levitation bearing. x Windings A2 and C2 control the electromagnetic force F in the y-direction of the first radial magnetic levitation bearing. y Windings A3 and C3 control the electromagnetic force F in the x-direction of the second radial magnetic levitation bearing. x Windings A4 and C4 control the electromagnetic force F in the y-direction of the second radial magnetic levitation bearing. y The electromagnetic force in each degree of freedom is determined by the current in both windings. After linearization, the electromagnetic force F generated by each winding is... mag The relationship between the winding control current and the rotor relative position x satisfies F mag =K i *i s -K s *x, where K i K is the electromagnetic force / current coefficient. x It represents the electromagnetic force / displacement coefficient.

[0041] The control method of magnetic levitation bearing control system usually adopts dual closed-loop control. The outer loop is the position loop, which compares the rotor relative position signal fed back by the position sensor with the given position. The inner loop group control current command signal is given by the position loop controller, and finally the current loop quickly tracks to achieve effective control of electromagnetic force.

[0042] Each of the bridge arms B1, B2, B3, B4, B5, B6, B7, B8, B9, and B10 includes an upper bridge arm and a lower bridge arm. Each upper and lower bridge arm includes a controllable switch and a unidirectional conducting device connected in antiparallel to the controllable switch. The upper and lower nodes of each of the bridge arms B1, B2, B3, B4, B5, B6, B7, B8, B9, and B10 are respectively connected to the positive and negative terminals of the DC voltage source.

[0043] The windings A1, A2, A3, A4 and bridge arms B1, B2, B3, B4, B5 form fault-tolerant topology 1; the windings C1, C2, C3, C4 and bridge arms B5, B6, B7, B8, B9, B10 form fault-tolerant topology 2; fault-tolerant topology 1 and fault-tolerant topology 2 share a DC power supply.

[0044] Both the first and second fault-tolerant topologies include normal mode and fault mode;

[0045] In normal mode, for any non-common bridge arm B j The upper and lower bridge arms alternately operate; the upper bridge arms of B1-B2 (i.e., the first non-common bridge arm group) and B6-B7 (i.e., the third non-common bridge arm group) have the same on / off state, while the controllable switches of the upper bridge arms of B3-B4 (i.e., the second non-common bridge arm group) and B8-B9 (i.e., the fourth non-common bridge arm group) operate in the same state as the controllable switches of the upper bridge arms of B1-B2 and B6-B7 (e.g., such as...). Figure 1 As shown, the upper controllable switches of non-common bridge arms B1-B2 and B6-B7 are operational, while the lower controllable switches are not operational; the opposite is true for non-common bridge arms B3-B4 and B8-B9. Furthermore, the reference current of each fault-tolerant topology control winding comes from the bias current and the control current. The reference current of winding A is usually the sum of the bias current and the control current, while the reference current of winding C is usually the difference between the sum of the bias current and the control current.

[0046] In any fault-tolerant topology D i Any non-public bridge arm B j When a short circuit fault occurs in the controllable switch, D i Switching from normal mode to fault mode:

[0047] When any fault-tolerant topology D i Any non-public bridge arm B j When a short-circuit fault occurs in the upper arm controllable switch of any non-common bridge arm, the upper arm controllable switches of all other non-common bridge arms remain open; when any fault-tolerant topology D... i Any non-public bridge arm B j When a short-circuit fault occurs in the controllable switch of the lower arm of the bridge, the controllable switches of the lower arms of other non-common bridge arms remain in the open state.

[0048] With B j The currents in the windings controlled by the non-common bridge arms in the same group are reversed, thus causing B to... j The direction of the current in the controlled winding is the same as that in D. i The current direction of the windings controlled by the other non-common bridge arms is opposite;

[0049] D i The reference current of the controlled winding is a constant bias current; the reference current of the controlled winding in the fault-tolerant topology that has not entered the fault mode still comes from the sum of the bias current and the control current.

[0050] Regardless of whether the fault-tolerant topology is in fault mode or normal mode, the common arms B5 and B 10 Both the upper and lower bridge arms are normal and controllable.

[0051] Specifically, fault-tolerant topologies 1 and 2 (i.e., the first and second fault-tolerant topologies) both have normal and fault modes, and the control methods are the same. Taking fault-tolerant topology 1 as an example, in normal mode, the upper bridge arm controllable switches of non-common bridge arms B1 and B2 are active, while the lower bridge arm controllable switches are inactive; the upper bridge arm controllable switches of non-common bridge arms B3 and B4 are inactive, while the lower bridge arm controllable switches are active. In fault mode, the controllable switches of the faulty non-common bridge arm are controlled in the opposite direction to those of the other three non-common bridge arms, and the winding current control directions are opposite. This means that if the upper bridge arm controllable switch of the faulty non-common bridge arm is active and the lower bridge arm controllable switch is inactive in normal mode, then the controllable switches of the other three non-common bridge arms will be changed to be inactive in the upper bridge arm and active in the lower bridge arm.

[0052] Specifically, Figure 3A This is the circuit topology diagram for fault-tolerant topology 1 in normal mode. Figure 3B This is the circuit topology diagram for fault-tolerant topology 1, showing the switching to fault mode after a short-circuit fault occurs in controllable switch S1. (Example:) Figure 3A As shown, in normal mode, the upper bridge arm controllable switches S1 and S2 of non-common bridge arms B1 and B2 are operational, while the lower bridge arm controllable switches S1' and S2' are inactive; the upper bridge arm controllable switches S3 and S4 of non-common bridge arms B3 and B4 are inactive, while the lower bridge arm controllable switches S3' and S4' are operational. In this mode, the upper and lower bridge arm controllable switches S5 and S5' of the common bridge arm are operational, while the lower bridge arm controllable switches S1' and S2' of bridge arms B1 and B2 and the upper bridge arm controllable switches S3 and S4 of bridge arms B3 and B4 remain open and do not participate in current control.

[0053] When a short-circuit fault occurs in a controllable switch of any fault-tolerant topology that is not in a common bridge arm (i.e., the faulty bridge arm exhibits a short-circuit fault in a closed controllable switch), it will affect the winding current control, causing the winding current to deviate significantly from the reference value, which in turn leads to the instability of the magnetic levitation bearing rotor. Specific phenomena when a short circuit occurs in a controllable switching device include:

[0054] When a short-circuit fault occurs in the upper controllable switch S1 of bridge arm B1, one end of winding A1 is directly connected to the positive terminal of the DC power supply, and the current in winding A1 rises rapidly. The modulation ratio of the current controller output of winding A1 decreases rapidly, and the current in A1 rises until it triggers the current protection, causing the system to shut down. Similarly, when a short-circuit fault occurs in the upper controllable switch S2 of bridge arm B2, the current in winding A2 rises rapidly. When a short-circuit fault occurs in the lower controllable switch S3' of bridge arm B3, one end of winding A3 is directly connected to the negative terminal of the DC power supply, and the current in winding A3 rises rapidly. When a short-circuit fault occurs in the lower controllable switch S4' of bridge arm B4, the current in winding A4 rises rapidly.

[0055] In normal mode, if any of the above controllable switches S1, S2, S3', and S4' experiences a short circuit fault, the system can switch to fault mode.

[0056] like Figure 3B As shown, when a short-circuit fault occurs in the controllable switch S1 of bridge arm B1, the fault-tolerant topology 1 changes. At this time, the upper bridge arm controllable switch S2 of bridge arm B2 is open, and the lower bridge arm controllable switch S2' is closed; the upper bridge arm controllable switches S3 and S4 of bridge arms B3 and B4 are open, and the lower bridge arm controllable switches S3' and S4' are closed; the lower bridge arm controllable switch S1' of bridge arm B1 and the upper bridge arm controllable switches S2, S3, and S4 of bridge arms B2, B3, and B4 remain open and do not participate in current control.

[0057] like Figure 3B As shown, in fault mode, the current direction of winding A2 is reversed compared to the normal mode (that is, if a short-circuit fault occurs in the controllable switch of B1, the winding A2 controlled by bridge arm B2 should have its current direction changed; because after a short-circuit fault occurs in S1 of B1, no operation can be performed on S1 and S1', otherwise it will cause the bridge arm to shoot through, resulting in more serious consequences; the reason for reversing the current direction of A2 is that after a short-circuit fault in S1, in order to keep the current of A1 controllable, the voltage of the common bridge arm must be kept near Vdc. If A2 is not reversed at this time, the current of A2 will drop uncontrollably and become uncontrollable). Since the magnitude of the electromagnetic force on the active magnetic bearing is proportional to the square of the current and is independent of the direction of the current flowing through the coil, the system can still work normally. Ultimately, the current direction of the windings controlled by the faulty bridge arm and the non-faulty bridge arm is opposite.

[0058] Preferably, the controllable switch is a power semiconductor switching device; the unidirectional conducting device is a diode.

[0059] Preferably, the controllable switch is a power semiconductor switching device, such as an insulated gate bipolar transistor or a field-effect transistor.

[0060] This invention provides a short-circuit fault-tolerant control method for a four-degree-of-freedom magnetic levitation bearing, applicable to the topology circuit described in any of the above embodiments, such as... Figure 4 As shown, it includes:

[0061] S101 detects the current in A1-A4 and C1-C4 in real time and calculates the sum of the absolute values ​​of the current in the winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively.

[0062] Specifically, the currents of windings A1, A2, A3, A4, C1, C2, C3, and C4 are detected in real time, and the sum of the absolute values ​​of the currents of windings A1 and C1, windings A2 and C2, windings A3 and C3, and windings A4 and C4 is calculated.

[0063] S102, determine whether the sum of the absolute values ​​of the currents of any winding combination is greater than the first threshold T. If so, proceed to S103; otherwise, return to S101. Where T = 2I + k, I is the bias current of any winding, and k is the margin.

[0064] Specifically, determine whether the sum of the absolute values ​​of the currents of any winding A1, C1, winding A2, C2, winding A3, C3 and winding A4, C4 is greater than a preset current threshold (i.e., the first threshold T). If yes, proceed to step S103; otherwise, return to step S101.

[0065] Preferably, the preset current threshold is obtained by adding a certain margin to twice the bias current of the winding.

[0066] It is understood that if the sum of the absolute values ​​of the currents in any of the windings A1, C1, A2, C2, A3, C3 and A4, C4 is greater than the preset current threshold, it means that a short circuit fault has occurred in any of the controllable switches S1, S2, S3' and S4'.

[0067] S103, locate the faulty bridge arm based on the modulation ratio change of the current controller of each winding, wherein the faulty bridge arm is the bridge arm where the controllable switch that has experienced a short circuit fault is located.

[0068] Preferably, the modulation ratio change of the current controller of the winding connected to the faulty bridge arm is lower than the second threshold within a preset time.

[0069] Preferably, the modulation ratio of the current controller output of each winding is monitored in real time and compared with the set threshold. When a short circuit fault occurs in the controllable switch, the modulation ratio of the current controller output of the corresponding winding will decrease rapidly within a preset time and be significantly lower than the set threshold, thereby locating the specific faulty bridge arm.

[0070] For example, under normal circumstances, the modulation ratio of the current controller output usually fluctuates around 0.4-0.6; if a fault occurs, the modulation ratio will rapidly (e.g., within 0.5ms) decrease to 0.

[0071] S104, the fault-tolerant topology D where the faulty bridge arm is located i Switching from normal mode to fault mode enables D i The controllable switches of the upper or lower arms of other non-common bridge arms are all kept in the open state, so that B j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

[0072] Specifically, the fault-tolerant topology where the switch short-circuit occurs is switched from normal mode to fault mode, and the current distribution strategy is changed. In the fault-tolerant topology where a controllable switch short-circuit fault occurs, the controlled winding reference current is set to a constant bias current; while in the fault-tolerant topology where a controllable switch short-circuit fault does not occur, the controlled winding reference current is set to both bias current and control current.

[0073] by Figure 3B For example, after a short-circuit fault occurs in controllable switch S1, one end of winding A1 is connected to the positive terminal of the DC power supply, and the current in winding A1 rises rapidly. To prevent the current in winding A1 from becoming uncontrollable, the upper arm controllable switch S5 of the common bridge arm B5 needs to remain closed for a long time to ensure that the voltage across winding A1 is controllable. With controllable switch S5 closed, the current control of windings A2, A3, and A4 only exists in rising and freewheeling modes; the current falling mode disappears, causing a decrease in the current control performance of windings A2, A3, and A4, but they can still control a constant current. Therefore, the current distribution strategy should be changed to fault-tolerant topology 1 controlling a constant current (i.e., dynamic current cannot be controlled; the reference current of windings A1-A4 becomes a constant value, and the reference current only comes from the constant bias current), while fault-tolerant topology 2, which has not experienced a short-circuit fault, controls both the bias current and the control current (i.e., the reference current of windings C1-C4 both come from the bias current and the command value of the displacement controller).

[0074] In summary, the short-circuit fault-tolerant control method for a four-degree-of-freedom magnetic levitation bearing provided by this invention can promptly detect short-circuit faults in switching devices. By adjusting the winding current control direction of the faulty topology, the fault-tolerant topology still possesses the ability to control a constant winding current. The faulty fault-tolerant topology drives the winding to generate a constant bias current, while the normal fault-tolerant topology drives the winding to generate both bias and control currents. This ensures that the winding current in each degree of freedom of the magnetic bearing can still generate a stable electromagnetic force, effectively preventing the risk of high-speed rotor collision caused by uncontrolled winding current due to a short-circuit fault. This fault-tolerant topology and control method achieves fault-tolerant operation of the magnetic levitation bearing system under short-circuit faults, ensuring stable rotor levitation even when a short-circuit fault occurs in the switching device, thus improving the system's fault tolerance capability.

[0075] The following describes a switching short-circuit fault-tolerant topology and control system for a four-degree-of-freedom magnetic levitation bearing provided by the present invention. The switching short-circuit fault-tolerant topology and control system for a four-degree-of-freedom magnetic levitation bearing described below can be referred to in correspondence with the switching short-circuit fault-tolerant topology and control method for a four-degree-of-freedom magnetic levitation bearing described above.

[0076] This invention provides a short-circuit fault-tolerant control system for a four-degree-of-freedom magnetic levitation bearing, such as... Figure 5 As shown, it includes: the topology circuit as described in any of the above embodiments, the fault detection module, the PWM signal switching module, and the fault mode current controller;

[0077] The fault detection module is used to detect the current of A1-A4 and C1-C4 in real time, and calculate the sum of the absolute values ​​of the current of winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively. When the sum of the absolute values ​​of the current of any winding combination is greater than the first threshold T, the faulty bridge arm is located according to the modulation ratio change of the current controller of each winding, and is sent to the PWM signal switching module and the fault mode current controller through the fault-tolerant command. The faulty bridge arm is the bridge arm where the controllable switch that has a short circuit fault is located, T = 2I + k, where I is the bias current of any winding and k is the margin.

[0078] Specifically, the control method of a magnetic levitation bearing system typically employs a dual closed-loop control. The outer loop is a position loop, where the difference between the rotor's relative position signal fed back by the displacement sensor and a given position is output to the displacement controller. The displacement controller then calculates and provides a reference current command for the inner winding assembly. Upon receiving this reference current command, the current controller calculates and outputs a suitable PWM signal to drive the topology to generate the actual winding current.

[0079] The fault detection module performs real-time detection of the current of windings A1, A2, A3, A4, C1, C2, C3, and C4 and the modulation ratio of the current controller output, and calculates the sum of the absolute values ​​of the current of windings A1 and C1, windings A2 and C2, windings A3 and C3, and windings A4 and C4. If the sum of the absolute values ​​of the current of any pair of windings is greater than a preset current threshold, a fault-tolerant command is sent to the PWM signal switching module to switch the fault-tolerant topology from normal mode to fault mode.

[0080] The preset current threshold is determined by the driven magnetic levitation bearing system to ensure timely and accurate detection of short-circuit faults in the controllable switching device. For example, it can be obtained by adding a certain margin to the sum of the bias currents of windings A1 and C1.

[0081] The PWM signal switching module is used to determine the fault-tolerant topology D that needs to be switched to the fault mode according to the fault-tolerant command. i And through the drive signal, D i All controllable switches of the upper or lower arms of other non-common bridge arms remain in the off state.

[0082] Specifically, the PWM signal switching module collects two sets of PWM signals generated by the normal mode current controller and the fault mode current controller, and then determines which mode of control to use based on the fault-tolerant instruction.

[0083] The fault mode current controller is used to control the current with B according to the fault-tolerant command. j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

[0084] Specifically, the fault mode current controller is used to change the reference current command of the fault-tolerant topology controlled by the short-circuit fault to a constant bias current, and to control the current of the non-common bridge arm controlled by the faulty bridge arm in the same group to reverse.

[0085] That is, a PWM signal switching module is used to switch the normal mode current controller of the magnetic levitation bearing to the fault mode current controller in order to control the fault-tolerant topology in the fault mode.

[0086] Furthermore, such as Figure 5 As shown, the system also includes a normal mode current controller for controlling the current of the controlled windings of each bridge arm in the fault-tolerant topology in normal mode.

[0087] This invention provides a computer-readable storage medium storing computer instructions that cause a processor to perform the method described in any of the above embodiments.

[0088] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A switching short-circuit fault-tolerant topology circuit for a four-degree-of-freedom magnetic levitation bearing, characterized in that, include: The first fault-tolerant topology D1 includes windings A1-A4, the first and second non-common bridge arm groups B1 and B2, B3 and B4, and the common bridge arm B5; The second fault-tolerant topology D2 includes windings C1-C4, the third and fourth non-common bridge arm groups B6 and B7, B8 and B9, and the common bridge arm B. 10 ; In this configuration, the midpoints of B1-B4 are each connected to one end of A1-A4, and the other end of A1-A4 is connected to the midpoint of B5; the midpoints of B6-B9 are each connected to one end of C1-C4, and the other end of C1-C4 is connected to the midpoint of B5. 10 The midpoint; winding combinations A1 and C1, A2 and C2 are used to control the electromagnetic force of two degrees of freedom of the first magnetic levitation bearing, respectively; winding combinations A3 and C3, A4 and C4 are used to control the electromagnetic force of two degrees of freedom of the second magnetic levitation bearing, respectively; the upper and lower nodes of each bridge arm are respectively connected to the positive and negative terminals of the DC power supply, and both the upper and lower bridge arms include a controllable switch and a unidirectional conducting device connected in antiparallel to the controllable switch; Both the first and second fault-tolerant topologies include normal mode and fault mode; in normal mode, for any non-common bridge arm B j The controllable switches of the upper and lower bridge arms alternately operate; the controllable switches of the upper bridge arms of each bridge arm in the first and third non-common bridge arm groups operate in the same state, while the controllable switches of the upper bridge arms of each bridge arm in the second and fourth non-common bridge arm groups operate in the same state and opposite to the controllable switches of the upper bridge arms of each bridge arm in the first and third non-common bridge arm groups. The reference current of the winding controlled by each fault-tolerant topology comes from the bias current and the control current; in any fault-tolerant topology D i Any non-public bridge arm B j When a short-circuit fault occurs in the controllable switch of the upper or lower bridge arm, D i Switch to fault mode, D i The controllable switches of the upper or lower arms of other non-common bridge arms remain in the open state, in conjunction with B. j The currents in the windings controlled by the non-common bridge arms in the same group are reversed, D i The reference current for the controlled winding is a constant bias current.

2. The topology circuit as described in claim 1, characterized in that, The controllable switch is a power semiconductor switching device; the unidirectional conducting device is a diode.

3. The topology circuit as described in claim 2, characterized in that, The controllable switch is a power semiconductor switching device, such as an insulated gate bipolar transistor or a field-effect transistor.

4. A switching short-circuit fault-tolerant control method for a four-degree-of-freedom magnetic levitation bearing, applied to the topology circuit as described in any one of claims 1-3, characterized in that, include: S101, real-time detection of the current in A1-A4 and C1-C4, and calculation of the sum of the absolute values ​​of the current in the winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively; S102, determine whether the sum of the absolute values ​​of the currents of any winding combination is greater than the first threshold T. If so, proceed to S103; otherwise, return to S101. Where T = 2I + k, I is the bias current of any winding, and k is the margin. S103, locate the faulty bridge arm based on the change in modulation ratio of the current controller of each winding, wherein the faulty bridge arm is the bridge arm where the controllable switch that has experienced a short circuit fault is located. S104, the fault-tolerant topology D where the faulty bridge arm is located i Switching from normal mode to fault mode enables D i The controllable switches of the upper or lower arms of other non-common bridge arms are all kept in the open state, so that B j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

5. The method as described in claim 4, characterized in that, The current controller of the winding connected to the faulty bridge arm changes its modulation ratio by less than the second threshold within a preset time.

6. A switch-short-circuit fault-tolerant control system for a four-degree-of-freedom magnetic levitation bearing, characterized in that, include: The topology circuit, fault detection module, PWM signal switching module, and fault mode current controller as described in any one of claims 1-3; The fault detection module is used to detect the current of A1-A4 and C1-C4 in real time, and calculate the sum of the absolute values ​​of the current of winding combinations A1 and C1, A2 and C2, A3 and C3, and A4 and C4 respectively. When the sum of the absolute values ​​of the current of any winding combination is greater than the first threshold T, the faulty bridge arm is located according to the modulation ratio change of the current controller of each winding, and is sent to the PWM signal switching module and the fault mode current controller through a fault-tolerant command. The faulty bridge arm is the bridge arm where the controllable switch that has a short-circuit fault is located, T = 2I + k, where I is the bias current of any winding and k is the margin. The PWM signal switching module is used to determine the fault-tolerant topology D that needs to be switched to the fault mode according to the fault-tolerant command. i And through the drive signal, D i All controllable switches of the upper or lower arms of other non-common bridge arms remain in the off state; The fault mode current controller is used to control the current with B according to the fault-tolerant command. j The current in the windings controlled by the non-common bridge arms in the same group is reversed, and D... i The reference current of the controlled winding is set to a constant bias current.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a processor to perform the method as described in any one of claims 4-5.

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