CN112727923A - Switch open circuit fault tolerance system and method for magnetic bearing series winding controller - Google Patents

Switch open circuit fault tolerance system and method for magnetic bearing series winding controller Download PDF

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Publication number
CN112727923A
CN112727923A CN202011605006.3A CN202011605006A CN112727923A CN 112727923 A CN112727923 A CN 112727923A CN 202011605006 A CN202011605006 A CN 202011605006A CN 112727923 A CN112727923 A CN 112727923A
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bridge arm
winding
current
fault
preset
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CN112727923B (en
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蒋栋
杨佶昌
孙宏博
李安
刘自程
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0444—Details of devices to control the actuation of the electromagnets
    • F16C32/0451—Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/044—Active magnetic bearings
    • F16C32/0442—Active magnetic bearings with devices affected by abnormal, undesired or non-standard conditions such as shock-load, power outage, start-up or touchdown
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Magnetic Bearings And Hydrostatic Bearings (AREA)

Abstract

The invention discloses a switch open circuit fault tolerance system and a method of a magnetic bearing series winding controller, comprising 2N series windings, 2N +1 bridge arms and 1 direct current voltage source; the upper end of each bridge arm is connected with the anode of a direct current voltage source, and the lower end of each bridge arm is connected with the cathode of the direct current voltage source; in the fault-tolerant system, when a single switch element fails, the other residual switch elements can still be used for realizing the stable control of the magnetic suspension bearing system, and the smooth switching is carried out in a normal working mode and a fault-tolerant working mode, so that the rotor is ensured not to fall; when the open circuit fault of the switching element occurs, the system can be ensured to operate without stopping in a fault-tolerant working mode, and the fault redundancy capability of the magnetic suspension bearing system is effectively improved.

Description

Switch open circuit fault tolerance system and method for magnetic bearing series winding controller
Technical Field
The invention belongs to the field of magnetic suspension bearing control, and particularly relates to a switch open circuit fault tolerance system and method for a magnetic bearing series winding controller.
Background
The magnetic suspension bearing is a bearing device for suspending a rotor by using electromagnetic force, and can replace the traditional mechanical bearing to realize the non-contact operation of the rotor and a stator. The rotor and the stator are not in mechanical contact, and the motor has the characteristics of no need of lubrication, no friction, long service life and the like. The magnetic suspension bearing is widely applied to application occasions where the rotor needs to rotate at a high speed or the requirement on the working environment is high. For an active magnetic suspension bearing system, the active magnetic suspension bearing system mainly comprises a rotor, a sensor, a controller, an electromagnetic actuator and the like, and the design of a control system of the active magnetic suspension bearing system has great influence on the performance of the whole device. The power amplifier converts the control signal into a current in the winding to control the electromagnetic force of the magnetic bearing, which is an important component in the magnetic bearing system.
Open circuit failure means that the fault device maintains an open circuit state, and the magnitude of the circulating current of the device is always zero. In the magnetic suspension power amplifier, if a switching device has an open circuit fault, the bridge arm voltage control fails, so that the winding current deviates from a reference value, the position of a rotor is further unstable, and serious faults such as rotor drop, system halt and the like are caused.
The existing series controller applied to the magnetic suspension bearing reduces the number of devices and ensures the voltage utilization rate. Wherein each bridge arm only uses half of the devices, and the number of the devices has no redundancy, so that the fault-tolerant operation can not be realized.
Disclosure of Invention
In view of the above-mentioned drawbacks and needs of the prior art, the present invention provides a switch open fault tolerant system and method for a magnetic bearing series winding controller, which aims to solve the problem that the existing series winding controller does not have the capability of fault tolerant operation when a switch open fault occurs.
To achieve the above object, in a first aspect, the present invention provides a switch-off fault tolerant system for a magnetic bearing series winding controller, comprising: 2N windings, 2N +1 bridge arms and 1 direct-current voltage source; wherein, the windings are connected in series; the upper end of each bridge arm is connected with the anode of a direct current voltage source, and the lower end of each bridge arm is connected with the cathode of the direct current voltage source;
the first bridge arm and the 2N +1 bridge arm are non-public bridge arms, the ith bridge arm is a public bridge arm, and i is 2,3, … or 2N; specifically, an output node of a first bridge arm is connected with a first end of a first winding; the output node of the ith bridge arm is connected with the second end of the (i-1) th winding; the output node of the ith bridge arm is connected with the first end of the ith winding; the output node of the 2N +1 th bridge arm is connected with the second end of the 2N winding;
each bridge arm comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively comprise a switch device and a one-way conduction device connected with the switch device in an anti-parallel mode.
Further preferably, the switching device is a fully-controlled switching device including an insulated gate bipolar transistor; the one-way conduction device is a diode.
Further preferably, the magnetic bearing series winding controller is used for realizing N-axis magnetic suspension; wherein, every two of the 2N windings are divided into one group, and N groups are provided in total; one group of windings corresponds to the control shaft magnetic suspension bearing; the control variables are the common mode current and the differential mode current of each set of windings.
In a second aspect, the present invention provides a fault tolerance method of the above switch open-circuit fault tolerance system, including the following steps:
s1, detecting the current on each winding in real time, judging each bridge arm based on the detected winding current, and determining a fault bridge arm;
s2, judging the open circuit fault of each switching device in the fault bridge arm based on the direction change of the common mode current by detecting the direction of the common mode current in the winding, and determining the position of the fault switching device;
s3, if the upper bridge arm switching device of the first bridge arm is open-circuit, the upper or lower bridge arm switching device of the jth bridge arm is open-circuit or the lower bridge arm switching device of the 2N +1 bridge arm is open-circuit, switching the current direction of each winding to enable the fault switching device not to work, and utilizing other normal devices to realize the control of each winding current to enable the system to continue to operate under the fault-tolerant working condition, so as to ensure that the magnetic suspension bearing rotor can still normally suspend; j ∈ {2,3, …,2N }.
Further preferably, the method for determining each bridge arm based on the detected winding current includes:
if the current on the first winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the first bridge arm breaks down;
if the difference between the current on the i-1 th winding and the current on the i-th winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the i-th bridge arm has a fault; 2,3, …, 2N;
and if the current on the 2N winding is larger than the preset first current threshold and the holding time smaller than the preset second current threshold is larger than the preset holding time, judging that the 2N +1 bridge arm has a fault.
Further preferably, the preset first current threshold is smaller than 0, and the preset second current threshold is larger than 0; the preset first current threshold and the preset second current threshold are determined according to a magnetic suspension bearing control system in which the magnetic bearing series winding controller is located.
Further preferably, the preset first current threshold I is set as aboveL∈[-0.5,0]The preset second current threshold IH∈[0,0.5]。
Further preferably, the preset holding time is ksT, wherein ksIs a constant greater than zero, and T is the sampling period of the current sensing.
Further preferably, the method for switching the current direction of each winding comprises the following steps:
if the upper bridge arm switching device of the first bridge arm is open-circuited, reversing the current directions of all the windings;
if the upper bridge arm switching device of the jth bridge arm is open-circuit, reversing the current from the jth winding to the 2N winding;
if the lower bridge arm switching device of the jth bridge arm is open-circuited, reversing the current from the first winding to the jth winding;
and if the lower bridge arm switching devices of the 2N +1 th bridge arm are disconnected, reversing the current directions of all the windings.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
1. the invention provides a switch open-circuit fault-tolerant system of a magnetic bearing series winding controller, wherein because the magnetic bearing series winding controller, the winding current can obviously deviate from a reference value when the open-circuit fault of a switch device occurs, the current control fails, and a magnetic bearing rotor falls off and cannot work normally. The invention adopts the series winding topology as the winding topology of the magnetic suspension bearing controller, each switching element has an independent block, the failure of a single switching element does not affect other elements, and simultaneously, the single diode which is independently placed has no great influence, therefore, in the fault-tolerant system provided by the invention, when the single switching element fails, the stable control of the magnetic suspension bearing system can be realized by using other residual switching elements, the smooth switching is realized in a normal working mode and a fault-tolerant working mode, and the rotor is ensured not to fall; when the open circuit fault of the switching element occurs, the system can be ensured to operate without stopping in a fault-tolerant working mode, and the fault redundancy capability of the magnetic suspension bearing system is effectively improved.
2. The switch open circuit fault-tolerant system of the magnetic bearing series winding controller provided by the invention only needs 2N +1 bridge arms to control 2N windings of an N-axis magnetic suspension bearing, and can realize fault tolerance of switch open circuit of the multi-freedom-degree series winding controller.
3. The invention provides a fault-tolerant method of a switch open-circuit fault-tolerant system of a magnetic bearing series winding controller, which measures the current of each winding in real time when the system is in normal operation, and identifies a fault phase and a switch device with an open-circuit fault by judging the value of the current of each winding when the switch device is in the open-circuit fault. By adjusting the direction of the winding current, the system is not influenced on the control of the amplitude of the winding current, and the fault-tolerant control of the switch open circuit fault is realized. When the switching devices at different positions are broken, the system can adopt different fault-tolerant topologies to ensure that the current of the winding is still controllable, the normal suspension of the rotor is kept, and the serious fault that the magnetic suspension bearing system is stopped due to the falling of the rotor is avoided. The method can effectively prevent the magnetic bearing system from losing stability when the switch is in open circuit fault, avoid the rotor from falling, realize the fault-tolerant operation of the magnetic bearing system and has good practical application value.
4. The fault-tolerant method of the switch open-circuit fault-tolerant system of the magnetic bearing series winding controller is based on the characteristic that the winding current in the active magnetic suspension bearing flows in a single direction and the redundancy of devices in the topology of the series winding, when an open-circuit fault occurs in a certain switching device, the fault switch can be prevented from participating in current control in a mode of changing the current direction of the winding, so that the series winding controller can continue to operate in a fault-tolerant working mode, the current control effect in the fault-tolerant working mode is consistent with that in a normal working mode, and the robustness of the current controller in the magnetic suspension bearing is effectively improved by the scheme.
Drawings
FIG. 1 is a schematic diagram of an eight-pole radial magnetic bearing according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a switch-off fault tolerance system of a magnetic bearing series winding controller according to embodiment 1 of the present invention;
fig. 3 is a flowchart of a fault tolerance method of the switch open fault tolerance system according to embodiment 2 of the present invention;
fig. 4 is a topological diagram of various operation modes of a magnetic bearing series winding controller provided in embodiment 2 of the present invention; wherein, (a) is a circuit topological diagram under the normal working mode of the magnetic bearing series winding controller; (b) a topological graph under the fault-tolerant working mode of the magnetic bearing series winding controller after the upper bridge arm switch tube of the third bridge arm has an open circuit fault; (c) a topological graph under the fault-tolerant working mode of the magnetic bearing series winding controller after the upper bridge arm switch tube of the second bridge arm has an open circuit fault; (d) a topological graph under the fault-tolerant working mode of the magnetic bearing series winding controller after an upper bridge arm switch tube of a first bridge arm or a lower bridge arm switch tube of a fifth bridge arm has an open circuit fault;
FIG. 5 is a block diagram of a magnetic bearing series winding controller switch-off fault tolerant system provided in embodiment 2 of the present invention;
fig. 6 is a waveform diagram of the rotor position when the magnetic bearing fault tolerant system provided by embodiment 2 of the present invention switches from the normal mode of operation to the fault tolerant mode of operation.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In order to achieve the above object, in a first aspect, the present invention provides a switch-off fault tolerant system of a magnetic bearing series winding controller, comprising: 2N windings, 2N +1 bridge arms and 1 direct-current voltage source; wherein, the windings are connected in series; the upper end of each bridge arm is connected with the anode of a direct current voltage source, and the lower end of each bridge arm is connected with the cathode of the direct current voltage source;
the first bridge arm and the 2N +1 bridge arm are non-public bridge arms, the ith bridge arm is a public bridge arm, and i is 2,3, … or 2N; specifically, an output node of a first bridge arm is connected with a first end of a first winding; the output node of the ith bridge arm is connected with the second end of the (i-1) th winding; the output node of the ith bridge arm is connected with the first end of the ith winding; the output node of the 2N +1 th bridge arm is connected with the second end of the 2N winding;
each bridge arm comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively comprise a switch device and a one-way conduction device connected with the switch device in an anti-parallel mode. Preferably, the switching device is a fully-controlled switching device, and comprises an insulated gate bipolar transistor; the one-way conduction device is a diode.
The magnetic bearing series winding controller is used for realizing N-axis magnetic suspension; wherein, every two of the 2N windings are divided into one group, and N groups are provided in total; one group of windings corresponds to the control shaft magnetic suspension bearing; the control variables are the common mode current and the differential mode current of each set of windings. When the magnetic bearing is connected with the winding controller in series to work normally, the current direction in each winding is from the first end of the winding to the second end of the winding. When the switch device has an open circuit fault, the control of the winding current is affected, and the position of the magnetic suspension bearing rotor is further unstable.
In a second aspect, the present invention provides a fault tolerance method of the above switch open-circuit fault tolerance system, including the following steps:
s1, detecting the current on each winding in real time, judging each bridge arm based on the detected winding current, and determining a fault bridge arm; the method specifically comprises the following steps:
if the current on the first winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the first bridge arm breaks down;
if the difference between the current on the i-1 th winding and the current on the i-th winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the i-th bridge arm has a fault;
if the current on the 2N winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the 2N +1 bridge arm has a fault;
s2, judging the open circuit fault of each switching device in the fault bridge arm based on the direction change of the common mode current by detecting the direction of the common mode current in the winding, and determining the position of the fault switching device;
s3, if the upper bridge arm switching device of the first bridge arm is open-circuit, the upper or lower bridge arm switching device of the jth bridge arm is open-circuit or the lower bridge arm switching device of the 2N +1 bridge arm is open-circuit, switching the current direction of each winding to enable the fault switching device not to work, and utilizing other normal devices to realize the control of each winding current to enable the system to continue to operate under the fault-tolerant working condition, so as to ensure that the magnetic suspension bearing rotor can still normally suspend; j ∈ {2,3, …,2N }. The method for switching the current direction of each winding comprises the following steps:
if the upper bridge arm switching device of the first bridge arm is open-circuited, reversing the current directions of all the windings;
if the upper bridge arm switching device of the jth bridge arm is open-circuit, reversing the current from the jth winding to the 2N winding;
if the lower bridge arm switching device of the jth bridge arm is open-circuited, reversing the current from the first winding to the jth winding;
and if the lower bridge arm switching devices of the 2N +1 th bridge arm are disconnected, reversing the current directions of all the windings.
The current between the first current threshold and the second current threshold is a current whose value is around 0. Specifically, the preset first current threshold is slightly smaller than 0, and the preset second current threshold is slightly larger than 0; the specific values of the preset first current threshold and the preset second current threshold are determined according to a magnetic suspension bearing control system in which the magnetic bearing series winding controller is located. Preferably, the preset first current threshold I isL∈[-0.5,0]The preset second current threshold IH∈[0,0.5]. Further, the preset holding time is ksT, wherein ksIs a constant greater than zero, and T is the sampling period of the current sensing.
In order to further explain the open-circuit fault-tolerant system and method for the magnetic bearing series winding controller provided by the present invention, the following detailed description will be given by taking a biaxial magnetic suspension bearing for suspension (N ═ 2) as an example:
FIG. 1 is a block diagram of a single radial magnetic bearing structure having two electromagnetic forces F in orthogonal directions xxAnd electromagnetic force F in the y directionyControl is required. Wherein, the electromagnetic force F in the x directionxThe electromagnetic force F in the y direction is determined by the electromagnetic force generated by the winding A1 and the electromagnetic force generated by the winding A3yThe electromagnetic force generated by the winding A2 and the electromagnetic force generated by the winding A4 are determined together. Electromagnetic force F generated by each windingmagAnd a winding exciting current isAnd the relative position s of the rotor satisfies Fmag＝Ki*is-KsS, wherein KiIs the electromagnetic force/current coefficient; ksIs the electromagnetic force/displacement coefficient; kiAnd KsAll related to radial bearing structure. The control usually adopts double-loop control, the outer loop is a position loop, a relative position signal of the rotor fed back by a position sensor is compared with a given position, and an exciting current instruction signal of an inner loop winding is given by a series winding controller and is finally quickly tracked by a current loop to realize the effective control of electromagnetic force.
Examples 1,
A switch open fault tolerant system for a magnetic bearing series winding controller, as shown in fig. 2, comprising: 5 bridge arms, 4 windings and 1 direct-current voltage source;
the 5 bridge arms comprise a first bridge arm, a second bridge arm, a third bridge arm, a fourth bridge arm and a fifth bridge arm;
the 4 windings comprise a winding A1, a winding A2, a winding A3 and a winding A4;
the output node of the first bridge arm is connected with the first end of the winding A1, and the output node of the second bridge arm is connected with the second end of the winding A1; the output node of the second bridge arm is connected with the first end of the winding A2, and the output node of the third bridge arm is connected with the second end of the winding A2; the output node of the third bridge arm is connected with the first end of the winding A3, and the output node of the fourth bridge arm is connected with the second end of the winding A3; the output node of the fourth bridge arm is connected with the first end of the winding A4, and the output node of the fifth bridge arm is connected with the second end of the winding A4;
each bridge arm comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively comprise a switch device and a one-way conduction device which is connected with the switch device in an anti-parallel mode; in this embodiment, the switching device is a fully-controlled switching device, and includes an Insulated Gate Bipolar Transistor (IGBT); the one-way conduction device is a diode;
the upper ends of the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm and the fifth bridge arm are all connected with the positive electrode of a direct current voltage source, and the lower ends of the first bridge arm, the second bridge arm, the third bridge arm, the fourth bridge arm and the fifth bridge arm are all connected with the negative electrode of the direct current voltage source.
The magnetic bearing series winding controller can realize the biaxial suspension of the magnetic suspension bearing, wherein the winding A1 and the winding A3 control one shaft, the winding A2 and the winding A4 control the other shaft, and the control variables comprise common-mode current of the winding A1 and the winding A3, differential-mode current of the winding A1 and the winding A3, common-mode current of the winding A2 and the winding A4, and differential-mode current of the winding A2 and the winding A4; wherein, the differential mode current of the winding A1 and the winding A3 controls the position of one shaft in the magnetic suspension bearing; the differential mode current of the winding A2 and the winding A4 controls the position of the other shaft in the magnetic bearing.
Specifically, when the magnetic bearing series winding controller works normally, the current directions in the winding a1, the winding a2, the winding A3 and the winding a4 all flow from the first end of the winding to the second end of the winding;
5 bridge arms in the magnetic bearing series winding controller comprise 2 unshared bridge arms and 3 shared bridge arms; the first bridge arm and the fifth bridge arm are non-common bridge arms; the second bridge arm, the third bridge arm and the fourth bridge arm are a common bridge arm.
Examples 2,
A fault tolerance method of the switch open fault tolerance system according to embodiment 1 is shown in fig. 3, and includes:
s1, detecting the current on each winding in real time, judging each bridge arm based on the detected winding current, and determining a fault bridge arm;
it should be noted that, when an open circuit fault occurs in each switching device in the switch open circuit fault tolerant system in embodiment 1, the control of the winding current is affected, so that the position of the magnetic bearing rotor is unstable; specific phenomena when the switching device is open include:
(1) after the upper bridge arm switch of the first bridge arm is disconnected, the current of the winding A1 cannot rise, so that the current of the winding A1 is reduced to 0, and the currents of other windings are not influenced; after the lower bridge arm switch of the first bridge arm is disconnected, the current of each winding is not influenced under the normal working condition;
(2) after an upper bridge arm switch of any one of 3 public bridge arms (a second bridge arm, a third bridge arm and a fourth bridge arm) is disconnected, the current of a right side winding is smaller than or equal to the current of a left side winding, when the current of the right side winding is required to be larger than the current of the left side winding in control, the currents of the two windings are kept equal, and the currents of other windings are not influenced; after a lower bridge arm switch of any one of the 3 public bridge arms is switched off, the current of the right winding is larger than or equal to the current of the left winding, and when the current of the right winding is required to be smaller than the current of the left winding in control, the currents of the two windings are kept equal, and the currents of other windings are not influenced;
(3) after the upper bridge arm switch of the fifth bridge arm is disconnected, the current of each winding is not influenced under the normal working condition; after the lower bridge arm switch of the fifth bridge arm is disconnected, the current of the winding A4 cannot rise, so that the current of the winding A5 is reduced to 0, and the currents of other windings are not influenced;
according to different winding current changes generated when the switch devices generate open circuit faults, the fault switch devices can be identified.
Therefore, the method for judging each bridge arm based on the detected winding current specifically comprises the following steps:
if the current on the winding A1 is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the first bridge arm breaks down;
if the difference between the current of the winding A1 and the current of the winding A2 is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the second bridge arm has a fault;
if the difference between the current of the winding A2 and the current of the winding A3 is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the third bridge arm has a fault;
if the difference between the current of the winding A3 and the current of the winding A4 is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the fourth bridge arm has a fault;
if the current of the winding A4 is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the fifth bridge arm has a fault;
in this embodiment, the value of the preset first current threshold is-0.5A, and the value of the preset second current threshold is 0.5A. The preset holding time is ksT; wherein k issA constant greater than zero, taking the value of 10; and T is the sampling period of current detection, and the value is 0.05 ms.
S2, judging the open circuit fault of each switching device in the fault bridge arm based on the direction change of the common mode current by detecting the direction of the common mode current in the winding, and determining the position of the fault switching device;
specifically, when the magnetic suspension bearing controller works normally, the common-mode current of the winding A1 and the winding A3 and the common-mode current of the winding A2 and the winding A4 are kept unchanged; when the switch open-circuit fault occurs, the common-mode current can change due to control failure, the change directions of the common-mode current can be different when the upper bridge arm switching device and the lower bridge arm switching device in each bridge arm have open-circuit faults, and the fault switching devices in the fault bridge arms can be judged according to the change directions of the common-mode current.
And S3, if the upper bridge arm switching device of the first bridge arm is broken, the upper or lower bridge arm switching device of any common bridge arm (the second bridge arm, the third bridge arm and the fourth bridge arm) is broken or the lower bridge arm switching device of the fifth bridge arm is broken, switching the current direction of each winding to enable the fault switching device not to work, and utilizing other normal devices to realize the control of each winding current to enable the system to continue to operate under the fault-tolerant working condition, so that the magnetic suspension bearing rotor can still normally suspend.
Specifically, fig. 4 shows a topological diagram of various operating modes of the magnetic bearing series winding controller. The diagram (a) shows a circuit topology of the magnetic bearing series winding controller in a normal working mode, the current directions of the four windings are all from left to right, and the lower bridge arm switching tube of the first bridge arm and the upper bridge arm switching tube of the fifth bridge arm keep a disconnected state under the condition that the four windings do not participate in current control. FIGS. (b) - (d) are topological diagrams of fault-tolerant modes of operation when 3 exemplary open circuit faults occur; specifically, the diagram (b) is a topological diagram in a fault-tolerant working mode of the magnetic bearing series winding controller after the upper bridge arm switching tube of the third bridge arm has an open circuit fault, at this time, the current directions of the winding a1 and the winding a2 are from left to right, the current directions of the winding A3 and the winding a4 are from right to left, and at this time, the upper bridge arm switching tube of the third bridge arm does not participate in current control, so that fault-tolerant operation can be realized. And (c) is a topological diagram in the fault-tolerant working mode of the magnetic bearing series winding controller after the upper bridge arm switch tube of the second bridge arm has an open circuit fault, at the moment, the current direction of the winding A1 is from left to right, the current directions of the winding A2, the winding A3 and the winding A4 are from right to left, and at the moment, the upper bridge arm switch tube of the second bridge arm does not participate in current control, so that fault-tolerant operation can be realized. And (d) is a topological diagram under the fault-tolerant working mode of the magnetic bearing series winding controller after the upper bridge arm switching tube of the first bridge arm or the lower bridge arm switching tube of the fifth bridge arm has an open circuit fault, the current directions of the four windings are all from right to left, and the fault switching tube does not participate in current control, so that fault-tolerant operation can be realized.
Based on the analysis, the method for switching the winding current direction comprises the following steps:
(1) when the upper bridge arm switching device of the first bridge arm is detected to be open-circuit, the current directions of all windings are reversed;
(2) when the upper bridge arm switching devices of any common bridge arm (a second bridge arm, a third bridge arm and a fourth bridge arm) are detected to be open-circuited, all winding currents on the right side of the bridge arm are reversed;
(3) when the lower bridge arm switching devices of any common bridge arm (a second bridge arm, a third bridge arm and a fourth bridge arm) are detected to be open-circuit, all winding currents on the left side of the bridge arm are reversed;
(4) when the lower bridge arm switching device of the fifth bridge arm is detected to be open-circuit, the current directions of all the windings are reversed;
it should be noted that, after the switch open circuit fault occurs, the current direction of the output end of the faulty bridge arm is limited, when the upper bridge arm switch has a fault, the output end of the current bridge arm can only control the normal inflow of current, and when the lower bridge arm switch has a fault, the output end of the current bridge arm can only control the normal outflow of current, so that after the current direction is switched, the property that the faulty bridge arm can still normally control the unidirectional current can be utilized to ensure that the winding current control does not fail. Therefore, according to the winding current direction adjusting method, the system can continue to operate under the fault-tolerant working condition, and the magnetic suspension bearing rotor can still normally suspend.
In summary, in the present embodiment, the current is detected in real time when the system operates normally, and the detected current includes the current of the winding a1, the difference between the current of the winding a1 and the current of the winding a2, the difference between the current of the winding a2 and the current of the winding A3, the difference between the current of the winding A3 and the current of the winding a4, and the current of the winding a 5. When the current is detected to be kept near 0 within a certain time, the current control is abnormal, the fault bridge arm is judged according to the abnormal current, and then the fault switching tube is judged by detecting the change of the common-mode current in the winding. After the fault switch tube is determined, the fault switch tube is switched to a fault-tolerant working mode without participating in current control by changing the current direction of the winding, and the suspension of a rotor in the magnetic suspension bearing system is continuously maintained.
Specifically, the average voltage at the output end of the first bridge arm is recorded as u1The average voltage of the output end of the second bridge arm is u2The average voltage at the output end of the third bridge arm is u3The average voltage at the output end of the fourth bridge arm is u4The average voltage at the output end of the fifth bridge arm is u5The average voltage u at the node can be corrected by controlling the duty ratio of the PWM signal of each switching device control signal1、u2、u3、u4And u5Controlling;
the impedances of winding A1, winding A2, winding A3 and winding A4 are all ZL；
Let i denote the current flowing through winding A11The current flowing through the winding A2 is i2The current flowing through the winding A3 is i3The current flowing through the winding A4 is i4；
When the controller works normally, the current directions in the winding A1, the winding A2, the winding A3 and the winding A4 all flow from the first end of the winding to the second end of the winding;
the magnitude of the current in winding a1, winding a2, winding A3, and winding a4 can be expressed as:
Figure BDA0002872947940000131
for a magnetic suspension bearing, two windings are needed to control in the x direction and the y direction respectively, and the control is performed in the x direction and the y direction respectively by one group of winding A1 and winding A3 and one group of winding A2 and winding A4 in the controller.
Fig. 5 shows a block diagram of a switch breaking fault tolerant system of a magnetic bearing series winding controller. The current control flow of the magnetic suspension bearing is that after a system receives a reference current instruction, the reference current value is compared with an actual current value, an error value is input into a current regulator (PI regulator), the current regulator gives out a reference voltage instruction of each shaft, the reference voltage instruction is converted into a duty ratio signal of each bridge arm through a transformation matrix, an actual PWM signal is generated by a carrier comparison method and input into each switch device, the actual current of each winding is controlled, and therefore the electromagnetic force of each direction of the magnetic suspension bearing is adjusted, and the suspension of a rotor is achieved. The current detection module detects the current of each winding, feeds the actual current back to the controller, detects the working state of the series winding controller in real time through a fault identification algorithm, and changes the direction of the current in the winding by adjusting a transformation matrix mode in the controller when the open circuit fault of the switch is detected, so that the system can continuously run in a fault-tolerant working mode.
FIG. 6 is a waveform illustrating rotor position when the magnetic bearing fault tolerant system is switched from a normal mode of operation to a fault tolerant mode of operation. The rotor is firstly dropped on the protective bearing, the rotor is floated in a normal working mode, and after a transient process of a certain time, the rotor is kept in stable suspension. And when the upper bridge arm switching tube of the third bridge arm has an open circuit fault at the moment of 0.2s, the winding current control fails, the rotor position changes, the system switches to a fault-tolerant working mode immediately after monitoring the fault current, and the rotor position continues to keep stable suspension after a transient process of a certain time.
The invention utilizes the characteristic of unidirectional flow of winding current in the active magnetic suspension bearing and the redundancy of devices in the topology of the series winding, when a certain switching device has an open circuit fault, the fault switching tube can not participate in current control in a mode of changing the current direction of the winding, and further the series winding controller can continuously run in a fault-tolerant working mode, and the current control effect in the fault-tolerant working mode is consistent with that in a normal working mode.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (9)

1. A switch open fault tolerant system for a magnetic bearing series winding controller, comprising: 2N windings, 2N +1 bridge arms and 1 direct-current voltage source; the windings are mutually connected in series; the upper end of each bridge arm is connected with the positive electrode of the direct current voltage source, and the lower end of each bridge arm is connected with the negative electrode of the direct current voltage source;
the first bridge arm and the 2N +1 th bridge arm are non-common bridge arms, the ith bridge arm is a common bridge arm, and i is 2,3, … or 2N; the output node of the first bridge arm is connected with the first end of the first winding; the output node of the ith bridge arm is connected with the second end of the (i-1) th winding; the output node of the ith bridge arm is connected with the first end of the ith winding; the output node of the 2N +1 th bridge arm is connected with the second end of the 2N-th winding;
each bridge arm comprises an upper bridge arm and a lower bridge arm, and the upper bridge arm and the lower bridge arm respectively comprise a switch device and a one-way conduction device connected with the switch device in an anti-parallel mode.
2. The switch open fault tolerant system of claim 1 wherein said switching device is a fully controlled switching device comprising an insulated gate bipolar transistor; the unidirectional conducting device is a diode.
3. The switch trip fault tolerant system of claim 1 or 2, wherein the magnetic bearing series winding controller is used to achieve N-axis magnetic levitation; wherein, every two of the 2N windings are divided into one group, and N groups are provided in total; one group of windings corresponds to one shaft for controlling the magnetic suspension bearing; the control variables are the common mode current and the differential mode current of each set of windings.
4. A fault-tolerant method of the switch open fault tolerant system of any one of claims 1 to 3, comprising the steps of:
s1, detecting the current on each winding in real time, judging each bridge arm based on the detected winding current, and determining a fault bridge arm;
s2, judging the open circuit fault of each switching element in the fault bridge arm based on the direction change of the common mode current by detecting the direction of the common mode current in the winding;
s3, if the upper bridge arm switching device of the first bridge arm is open-circuit, the upper or lower bridge arm switching device of the jth bridge arm is open-circuit or the lower bridge arm switching device of the 2N +1 bridge arm is open-circuit, switching the current direction of each winding to enable the fault switching device not to work, and utilizing other normal devices to realize the control of each winding current to enable the system to continue to operate under the fault-tolerant working condition, so as to ensure that the magnetic suspension bearing rotor can still normally suspend; j ∈ {2,3, …,2N }.
5. The fault tolerant method of claim 4 wherein the method of determining each leg based on the detected winding current comprises:
if the current on the first winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the first bridge arm breaks down;
if the difference between the current on the i-1 th winding and the current on the i-th winding is larger than a preset first current threshold and the holding time smaller than a preset second current threshold is larger than a preset holding time, judging that the i-th bridge arm has a fault; 2,3, …, 2N;
and if the current on the 2N winding is larger than the preset first current threshold and the holding time smaller than the preset second current threshold is larger than the preset holding time, judging that the 2N +1 bridge arm has a fault.
6. The fault tolerant method according to claim 5 wherein the preset first current threshold is less than 0 and the preset second current threshold is greater than 0; the preset first current threshold and the preset second current threshold are determined according to a magnetic suspension bearing control system in which the magnetic bearing series winding controller is located.
7. Fault tolerant method according to claim 6, characterized in that the preset first current threshold IL∈[-0.5,0]The preset second current threshold IH∈[0,0.5]。
8. Fault tolerant method according to claim 5, characterized in that the preset hold time is ksT, wherein ksIs a constant greater than zero, and T is the sampling period of the current sensing.
9. The fault tolerant method of claim 4 wherein the method of switching the direction of current flow in each winding comprises:
if the upper bridge arm switching device of the first bridge arm is open-circuited, reversing the current directions of all the windings;
if the upper bridge arm switching device of the jth bridge arm is open-circuit, reversing the current from the jth winding to the 2N winding;
if the lower bridge arm switching device of the jth bridge arm is open-circuited, reversing the current from the first winding to the jth winding;
and if the lower bridge arm switching devices of the 2N +1 th bridge arm are disconnected, reversing the current directions of all the windings.
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