CN112815008A - Magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit - Google Patents

Abstract

The invention discloses a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit, and a switch open circuit fault tolerance system and method of the magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit. The four-phase full-bridge topology is adopted as the winding topology of the magnetic suspension bearing controller, the switch device is designed in a redundancy mode based on the characteristic that the winding current in the active magnetic suspension bearing flows in a single direction, the normal mode and the fault-tolerant mode are provided, when the switch device breaks down, the fault switch tube does not participate in current control, the stable control of the magnetic suspension bearing system is realized by utilizing the redundant switch element, the system can be kept to run without stopping under the fault-tolerant working condition, the rotor is ensured not to fall off, and the fault tolerance capability of the magnetic suspension bearing system is effectively improved.

Description

Magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit

Technical Field

The invention belongs to the field of magnetic suspension bearing control, and particularly relates to a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit, a switch open circuit fault tolerance system of the magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit, and a switch open circuit fault tolerance method of the magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit.

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. For example, chinese patent application No. CN201910153327.5 discloses a method for power electronic control based on magnetic bearings.

The power amplifier converts the current command into the actual current in the winding to control the electromagnetic force of the magnetic bearing, which is an important component in the magnetic suspension 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 four-phase four-bridge arm topology applied to the magnetic suspension power amplifier reduces the number of devices, but bridge arms of the topology are unipolar bridge arms, namely, each bridge arm only uses half of the devices, and the number of the devices has no redundancy, so that fault-tolerant operation cannot be realized.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit, a switch open-circuit fault tolerance system of the magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit and a switch open-circuit fault tolerance method of the magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit, and aims to solve the problem that the existing four-phase four-bridge arm topology does not have fault-tolerant operation capability when a switch open-circuit fault occurs.

To achieve the above object, according to a first aspect of the present invention, there is provided a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit, comprising:

4 windings A₁、A₂、A₃、A ₄4 bridge arms B₁、B₂、B₃、B₄And 1 DC voltage source;

bridge arm B₁、B₂、B₃、B₄Respectively with winding A₁、A₃、A₂、A₄Is connected to one end of winding A₁、A₃、A₂、A₄The other ends of the two are connected together to form a neutral point; wherein, winding A₁And A₃Electromagnetic force for controlling one degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing, winding A₂And A₄Controlling the electromagnetic force of the other degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing;

the bridge arm B₁、B₂、B₃、B₄The bridge comprises an upper bridge arm and a lower bridge arm, wherein the upper bridge arm and the lower bridge arm respectively comprise a controllable switch and a one-way conducting device which is connected with the controllable switch in an anti-parallel mode; the bridge arm B₁、B₂、B₃、B₄The upper node and the lower node are respectively connected with the anode and the cathode of the direct current voltage source;

the four-phase full-bridge topology circuit has a normal mode and a fault-tolerant mode, and in the normal mode, the bridge arm B₁、B₂The upper bridge arm controllable switch is closed, and the lower bridge arm controllable switch is opened; bridge armB₃、B₄The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; in fault-tolerant mode, bridge arm B₁、B₂The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; bridge arm B₃、B₄The upper bridge arm controllable switch is closed and the lower bridge arm controllable switch is open.

Preferably, the winding A₁And A₃The common mode current and the differential mode current of the magnetic suspension radial bearing control the electromagnetic force of one degree of freedom in the magnetic suspension radial bearing with two degrees of freedom, and the winding A₂And A₄The common mode current and the differential mode current of the magnetic suspension two-freedom-degree radial bearing control the electromagnetic force of the other freedom degree in the magnetic suspension two-freedom-degree radial bearing.

Preferably, the controllable switch is an insulated gate bipolar transistor; the unidirectional conducting device is a diode.

Preferably, winding A is in normal mode₁、A₂、A₃、A₄Current direction and fault-tolerant mode of winding a₁、A₂、A₃、A₄The current direction of (2) is opposite.

Preferably, winding a in the normal mode₁、A₂、A₃、A₄Current direction and fault-tolerant mode of winding a₁、A₂、A₃、A₄Comprises the following steps:

in normal mode, winding A₁、A₃Has a current direction of bridge arm B₁、B₂Flows to the neutral point; winding A₂、A₄The current direction of the bridge arm B is from the neutral point₃、B₄A midpoint of (a);

in fault-tolerant mode, winding A₁、A₃The current direction of the bridge arm B is from the neutral point₁、B₂A midpoint of (a); winding A₂、A₄Has a current direction of bridge arm B₃、B₄Towards the neutral point.

According to a second aspect of the present invention, there is provided a switch open circuit fault tolerant system of a magnetic suspension two-degree-of-freedom radial bearing four-phase full bridge topology circuit, comprising: a fault detection and mode switching module and a four-phase full bridge topology circuit as described in the first aspect;

the fault detection and mode switching module is used for winding A₁、A₃、A₂、A₄Is detected in real time, and the winding A is calculated₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a); if the winding A is₁、A₃、A₂、A₄If the sum of the absolute values of the currents is smaller than a preset current threshold value, the four-phase full-bridge topology circuit is switched from a normal mode to a fault-tolerant mode.

According to a third aspect of the present invention, there is provided a switch open-circuit fault tolerance method for a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit, applied to the four-phase full-bridge topology circuit according to the first aspect, comprising:

s101: real-time detection of winding A₁、A₃、A₂、A₄Calculating the current of said winding A₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a);

s102: judging the winding A₁、A₃、A₂、A₄If the sum of the absolute values of (a) is less than the preset current threshold, if yes, go to step S103; if not, returning to the step S101;

s103: and switching the four-phase full-bridge topology circuit from a normal mode to a fault-tolerant mode.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1. the four-phase full-bridge topology is adopted as the winding topology of the magnetic suspension bearing controller, the switch device is designed in a redundancy mode based on the characteristic that the winding current in the active magnetic suspension bearing flows in a single direction, the normal mode and the fault-tolerant mode are provided, when the switch device breaks down, the fault switch tube does not participate in current control, the stable control of the magnetic suspension bearing system is realized by utilizing the redundant switch element, the system can be kept to run without stopping under the fault-tolerant working condition, the rotor is ensured not to fall off, and the fault tolerance capability of the magnetic suspension bearing system is effectively improved.

2. For 4 windings of a two-degree-of-freedom radial magnetic suspension bearing, control can be performed only by 4 bridge arms, open circuit fault tolerance of a two-degree-of-freedom four-phase full-bridge topological switch can be achieved, and the two-degree-of-freedom four-phase full-bridge topological switch can be further expanded to multiple degrees of freedom.

3. The method comprises the steps of measuring the current of each winding in real time, judging whether the open-circuit fault of a switching device occurs according to the sum of the absolute values of the current of each winding, switching from a normal mode to a fault-tolerant mode when the open-circuit fault of the switching device occurs, enabling a fault switch to be free from participating in current control by adjusting the direction of the current of the winding, enabling the control of the system on the amplitude of the current of the winding to be unaffected, further enabling a four-phase full-bridge topology to continue to operate in the fault-tolerant mode, effectively preventing the magnetic bearing system from losing stability due to the open-circuit fault of the switch, avoiding the falling of a rotor, realizing the fault-tolerant; and the current control effect in the fault-tolerant mode is consistent with that in the normal mode, so that the robustness of the current controller in the magnetic suspension bearing is effectively improved.

Drawings

Fig. 1 is a schematic structural diagram of a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit provided by an embodiment of the invention;

fig. 2 is a schematic structural diagram of a magnetic suspension two-degree-of-freedom radial bearing provided by an embodiment of the invention.

Fig. 3(a) and fig. 3(b) are circuit topology diagrams of a magnetic suspension two-degree-of-freedom radial bearing four-phase full bridge topology circuit in a normal mode and a fault-tolerant mode, respectively, according to an embodiment of the present invention;

fig. 4 is a structural diagram of a switch open-circuit fault tolerance system of a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit when double closed-loop control is adopted according to an embodiment of the present invention;

fig. 5(a), fig. 5(b), fig. 5(c), and fig. 5(d) are respectively a normal mode of the switch open fault tolerant system of the magnetic suspension two-degree-of-freedom radial bearing four-phase full bridge topology circuit provided by the embodiment of the inventionRadial displacement oscillogram of rotor x and y axes when the formula is switched to the fault-tolerant mode, and radial displacement oscillogram flowing through a winding A₁、A₃Current i of_a1、i_a3A current waveform diagram of (a);

fig. 6 is a flowchart of a switch open-circuit fault tolerance method of a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit according to an embodiment of the present invention.

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.

The embodiment of the invention provides a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit, as shown in figure 1, comprising:

4 windings A₁、A₂、A₃、A ₄4 bridge arms B₁、B₂、B₃、B₄And 1 DC voltage source;

bridge arm B₁、B₂、B₃、B₄Respectively with winding A₁、A₃、A₂、A₄Is connected to one end of winding A₁、A₃、A₂、A₄The other ends of the two are connected together to form a neutral point; wherein, winding A₁And A₃Electromagnetic force for controlling one degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing, winding A₂And A₄And controlling the electromagnetic force of the other degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing.

Specifically, as shown in fig. 2, the magnetic suspension two-degree-of-freedom radial bearing has two orthogonal directions of electromagnetic force to be controlled, namely, x-direction electromagnetic force F_xAnd electromagnetic force F in the y direction_y. Wherein, the electromagnetic force F in the x direction_xIs formed by passing through winding A₁Current i of_a1Generated electromagnetic force and through winding A₃Current i of_a3The generated electromagnetic forces jointly determine the electromagnetic force F in the y direction_yBy passing through winding A₂Current i of_a2Generated electromagnetic force and through winding A₄Current i of_a4The electromagnetic forces generated are determined jointly. After linearization, the electromagnetic force F generated by each winding_magAnd a winding exciting current i_sAnd the relative position x of the rotor satisfies F_mag＝K_i*i_s-K_xX, wherein, K_iIs the electromagnetic force/current coefficient; k_xIs the electromagnetic force/displacement coefficient.

The control mode of the magnetic suspension bearing control system usually adopts double closed-loop control, the outer ring is a position ring, the relative position signal of the rotor fed back by a position sensor is compared with a given position, and the exciting current instruction signal of the inner ring winding given by a position ring controller is finally quickly tracked by a current ring, so that the effective control of the electromagnetic force is realized.

The bridge arm B₁、B₂、B₃、B₄The bridge comprises an upper bridge arm and a lower bridge arm, wherein the upper bridge arm and the lower bridge arm respectively comprise a controllable switch and a one-way conducting device which is connected with the controllable switch in an anti-parallel mode; the bridge arm B₁、B₂、B₃、B₄The upper node and the lower node are respectively connected with the anode and the cathode of the direct current voltage source;

the four-phase full-bridge topology circuit has a normal mode and a fault-tolerant mode, and in the normal mode, the bridge arm B₁、B₂The upper bridge arm controllable switch is closed, and the lower bridge arm controllable switch is opened; bridge arm B₃、B₄The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; in fault-tolerant mode, bridge arm B₁、B₂The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; bridge arm B₃、B₄The upper bridge arm controllable switch is closed and the lower bridge arm controllable switch is open.

Specifically, fig. 3(a) is a circuit topology in the normal mode, and fig. 3(b) is a circuit topology in the fault tolerant mode.As shown in FIG. 3(a), in normal mode, arm B₁、B₂The upper bridge arm controllable switches S1 and S2 are closed, and the lower bridge arm controllable switches S1 'and S2' are opened; bridge arm B₃、B₄The upper bridge arm controllable switches S3 and S4 are turned off, and the lower bridge arm controllable switches S3 'and S4' are turned on. In this mode, arm B₁、B₂Lower bridge arm controllable switches S1 ', S2' and bridge arm B₃、B₄The upper bridge arm controllable switches S3 and S4 are kept in an off state and do not participate in current control.

Work as when four-phase full-bridge topology circuit has controllable switch to take place the trouble of opening a circuit, can exert an influence to winding current control, make winding current can show the skew reference value, current control inefficacy, and then lead to magnetic suspension bearing rotor position to lose stability and take place to fall, unable normal work, concrete phenomenon when switching device opens a circuit includes:

when the upper bridge arm controllable switch S1 of the bridge arm B1 has an open circuit fault, the winding A₁Current cannot rise, so that winding A₁The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; similarly, when the upper arm controllable switch S2 of arm B2 has an open-circuit fault, winding A₃Current cannot rise, so that winding A₃The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; when bridge arm B₃After the lower bridge arm controllable switch S3' has an open circuit fault, the winding A₂Current cannot rise, so that winding A₂The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; when bridge arm B₄After the lower bridge arm controllable switch S4' has an open circuit fault, the winding A₄Current cannot rise, so that winding A₄The current decreases to 0 and the other winding currents will also slowly drop due to the control effect.

In the normal mode, if any one or more of the controllable switches S1, S2, S3 'and S4' has an open-circuit fault, the mode can be switched to the fault-tolerant mode.

As shown in FIG. 3(B), in fault tolerant mode, bridge arm B₁、B₂The upper bridge arm controllable switches S1 and S2 are disconnected, and the lower bridge arm controllable switches S3,S4, closing; bridge arm B₃、B₄The controllable switches of the upper bridge arms S3 'and S4' are closed, and the controllable switches S3 'and S4' of the lower bridge arms are opened; bridge arm B₁、B₂Upper bridge arm controllable switches S1 and S2 and bridge arm B₃、B₄The controllable switches S3 'and S4' of the lower bridge arm are in an off state and do not participate in current control. Bridge arm B₁、B₂The controllable switches of the upper bridge arms S1 'and S2' replace S3 'and S4' which have faults to participate in current control, and the bridge arm B₃、B₄The lower bridge arm controllable switches S3 and S4 replace the failed controllable switches S1 and S2 to participate in current control.

In the fault-tolerant mode, the fault switch device does not work, and the control of the current of each winding is realized by using other normal devices, so that the system continues to operate under the fault-tolerant working condition, and the magnetic suspension bearing rotor can still be suspended normally.

Namely when bridge arm B₁、B₂、B₃、B₄When one or more of the switching devices S1, S2, S3 'and S4' has a fault and an open circuit fault occurs, the switching device is switched to a fault-tolerant mode, and another group of spare switching devices S1 ', S2', S3 and S4 is started to work.

Because the electromagnetic force applied to 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, when the switch tube in the normal mode has an open-circuit fault, the switch tube can be switched to the fault-tolerant mode to reverse the current flowing through the coil, and the system can still work normally.

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, the magnetic suspension two-degree-of-freedom radial bearing system can continue to operate under the fault-tolerant working condition, and the magnetic suspension bearing rotor can still normally suspend.

The magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit provided by the embodiment of the invention has the advantages that the switch device is designed in a redundant manner based on the characteristic that the winding current in the active magnetic suspension bearing flows in a single direction, the normal mode and the fault-tolerant mode are realized, when the switch device fails, the fault switch tube does not participate in current control, the stable control on the magnetic suspension bearing system is realized by utilizing the redundant switch element, the system can be kept to run without stopping under the fault-tolerant working condition, the rotor is ensured not to fall off, and the fault tolerance capability of the magnetic suspension bearing system is effectively improved.

Based on the above embodiment, optionally, the winding a₁And A₃The common mode current and the differential mode current of the magnetic suspension radial bearing control the electromagnetic force of one degree of freedom in the magnetic suspension radial bearing with two degrees of freedom.

Specifically, the current loop control mode adopts differential control, and the control variable comprises a winding A₁And winding A₃Of (i) a common mode current (i)_a1+i_a3) Winding A₁And winding A₃Differential mode current (i)_a1-i_a3). Wherein, winding A₁And winding A₃The differential mode current of (a) controls the electromagnetic force in the x-direction in the magnetic bearing, thereby controlling the position of the shaft.

The winding A₂And A₄The common mode current and the differential mode current of the magnetic suspension two-freedom-degree radial bearing control the electromagnetic force of the other freedom degree of the magnetic suspension two-freedom-degree radial bearing.

Specifically, the current loop control mode adopts differential control, and the control variable comprises a winding A₂And winding A₄Of (i) a common mode current (i)_a2+i_a4) Winding A₂And winding A₄Differential mode current (i)_a2-i_a4). Wherein, winding A₂And winding A₄The differential mode current of (a) controls the electromagnetic force in the y-direction of the magnetic bearing, thereby controlling the position of the shaft.

Optionally, according to any of the above embodiments, the controllable switch is an insulated gate bipolar transistor; the unidirectional conducting device is a diode.

In particular, the controllable switch is a fully-controlled switch, such as an insulated gate bipolar transistor; the unidirectional conducting device is a diode.

Based on any of the above embodiments, optionally, the winding a in the normal mode₁、A₂、A₃、A₄Current direction and fault-tolerant mode of winding a₁、A₂、A₃、A₄Comprises the following steps:

in normal mode, winding A₁、A₃Has a current direction of bridge arm B₁、B₂Flows to the neutral point; winding A₂、A₄The current direction of the bridge arm B is from the neutral point₃、B₄A midpoint of (a);

in fault-tolerant mode, winding A₁、A₃The current direction of the bridge arm B is from the neutral point₁、B₂A midpoint of (a); winding A₂、A₄Has a current direction of bridge arm B₃、B₄Towards the neutral point.

Specifically, as shown in fig. 3(a), in the normal mode, the winding a₁、A₃Has a current direction of bridge arm B₁、B₂Flows to neutral point O; winding A₂、A₄The current direction of (A) is from the neutral point O to the bridge arm B₃、B₄The midpoint of (a). In fault-tolerant mode, winding A, as shown in FIG. 3(b)₁、A₃The current direction of (A) is from the neutral point O to the bridge arm B₁、B₂A midpoint of (a); winding A₂、A₄Has a current direction of bridge arm B₃、B₄Towards neutral point O.

It can be understood that, with the switching of the operation mode of the four-phase full-bridge topology circuit, the direction of the current of each winding is correspondingly switched.

Further, note bridge arm B₁Average voltage at output terminal is u₁Arm B of the bridge₂Average voltage at output terminal is u₂Arm B of the bridge₃Average voltage at output terminal is u₃Arm B of the bridge₄Average voltage at output terminal is u₄Average voltage of neutral point O is u₀By controllingThe duty ratio of the PWM signal of each switching device control signal may be adjusted to the average voltage u at the node₁、u₂、u₃And u₄Controlling;

note winding A₁Winding A₂Winding A₃And winding A₄All impedances of (are Z)_L；

Note winding A₁Wherein the current flowing through is i_a1Winding A₃Wherein the current flowing through is i_a3Winding A₂Wherein the current flowing through is i_a2Winding A₄Wherein the current flowing through is i_a4；

When the controller works normally, the winding A₁、A₃Has a current direction of bridge arm B₁、B₂Flows to neutral point O; winding A₂、A₄The current direction of (A) is from the neutral point O to the bridge arm B₃、B₄A midpoint of (a);

winding A₁Winding A₃Winding A₂And winding A₄The current magnitude in (a) can be expressed as:

the embodiment of the invention provides a switch open circuit fault tolerance system of a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topological circuit, which comprises the following components: a fault detection and mode switching module and a four-phase full-bridge topology circuit as described in any of the above embodiments;

the fault detection and mode switching module is used for winding A₁、A₃、A₂、A₄Is detected in real time, and the winding A is calculated₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a); if the winding A is₁、A₃、A₂、A₄If the sum of the absolute values of the currents is smaller than a preset current threshold value, the four-phase full-bridge topology circuit is switched from a normal mode to a fault-tolerant mode.

Specifically, in the normal mode, specific phenomena when the switching device is open include: when the upper bridge arm controllable switch S1 of the bridge arm B1 has an open circuit fault, the winding A₁Current cannot rise, so that winding A₁The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; similarly, when the upper arm controllable switch S2 of arm B2 has an open-circuit fault, winding A₃Current cannot rise, so that winding A₃The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; when bridge arm B₃After the lower bridge arm controllable switch S3' has an open circuit fault, the winding A₂Current cannot rise, so that winding A₂The current is reduced to 0, and the currents of other windings are also slowly reduced due to the influence of control; when bridge arm B₄After the lower bridge arm controllable switch S4' has an open circuit fault, the winding A₄Current cannot rise, so that winding A₄The current decreases to 0 and the other winding currents will also slowly drop due to the control effect.

If the fault detection and mode switching module judges the winding A₁、A₃、A₂、A₄If the sum of the absolute values of the currents is smaller than a preset current threshold value, it is confirmed that any one or more of the controllable switches S1, S2, S3 'and S4' in the four-phase full-bridge topology circuit has an open-circuit fault, the four-phase full-bridge topology circuit is switched from a normal mode to a fault-tolerant mode, so that a fault switch device does not work, the control of the current of each winding is realized by other normal devices, the system continues to operate under the fault-tolerant working condition, and the magnetic suspension bearing rotor is ensured to still suspend normally.

It can be understood that, with the switching of the operation mode of the four-phase full-bridge topology circuit, the direction of the current of each winding is correspondingly switched.

The magnitude of the preset current threshold is determined by a magnetic suspension bearing control system where the four-phase full-bridge topology current is located, and the preset current threshold is used for ensuring timely and accurate detection of the open-circuit fault of the controllable switching device. For example: according to A₁、A₃、A₂、A₄Is obtained by subtracting a certain margin from the sum of the bias currents.

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, the system can continue to operate under the fault-tolerant working condition, and the magnetic suspension bearing rotor can still normally suspend.

The control mode of the magnetic suspension bearing control system usually adopts double closed-loop control, the outer ring is a position ring, the relative position signal of the rotor fed back by a position sensor is compared with a given position, and the exciting current instruction signal of the inner ring winding given by a position ring controller is finally quickly tracked by a current ring, so that the effective control of the electromagnetic force is realized.

Specifically, as shown in fig. 4, the magnetic suspension bearing control is mainly divided into an outer ring position ring and an inner ring current ring, and the control flow is as follows: the position controller calculates a reference position signal and an actual position signal acquired by the displacement sensor to obtain a reference current signal, the current loop receives a reference current instruction, compares the reference current value with the actual current value, and inputs an error value into a current regulator (PI regulator), the PI current controller generates two groups of PWM driving signals, and the fault detection and mode switching module selects whether to switch the working mode to the fault-tolerant mode according to a current result detected in real time.

FIGS. 5(a) and 5(b) are radial displacement waveform diagrams of the rotor along x and y axes, respectively, and FIGS. 5(c) and 5(d) are waveforms of the radial displacement through the winding A₁、A₃Current i of_a1、i_a3Current waveform diagram of (2). The rotor is firstly dropped on the protective bearing, the rotor is floated in a normal mode, and after a transient process of a certain time, the rotor is kept in stable suspension. When the upper bridge arm switching tube of the first bridge arm has an open circuit fault within about 8.41s, the winding current control fails, the rotor position changes, the system switches to a fault-tolerant mode immediately after monitoring the fault current, and the rotor position passes throughAfter a certain time of transient process, the suspension is kept stable and flows through the winding A₁、A₃Current i of_a1、i_a3The value of the voltage is changed to-5A after a short time from the vicinity of +5A, which shows that the current flowing through the winding is reversed, namely the current switching process is finished and the system can stably run.

The system provided by the embodiment of the invention detects the current of each winding in real time, switches the working mode of the four-phase full-bridge topology circuit when the sum of the absolute values of the current of each winding is less than the preset current threshold value, so that a fault switch tube does not participate in current control, utilizes redundant switch elements to realize stable control on the magnetic suspension bearing system, can keep the system running without stopping under the fault-tolerant working condition, continues to maintain the suspension of the rotor in the magnetic suspension bearing system, ensures that the rotor does not fall off, and effectively improves the fault-tolerant capability of the magnetic suspension bearing system.

The embodiment of the invention provides a switch open circuit fault tolerance method for a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit, which is applied to the four-phase full-bridge topology circuit according to any one of the embodiments, as shown in fig. 6, and comprises the following steps:

s101: real-time detection of winding A₁、A₃、A₂、A₄Calculating the current of said winding A₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a);

specifically, when the system normally operates, the currents of the windings are detected in real time, and the sum of the absolute values of the currents of the windings is calculated.

S102: judging the winding A₁、A₃、A₂、A₄If the sum of the absolute values of (a) is less than the preset current threshold, if yes, go to step S103; if not, the process returns to step S101.

In particular, if the winding A is₁、A₃、A₂、A₄Is less than the preset current threshold, it means that an open circuit fault has occurred in any one or more of the controllable switches S1, S2, S3 ', S4'.

S103: and switching the four-phase full-bridge topology circuit from a normal mode to a fault-tolerant mode.

Specifically, when an open-circuit fault occurs in any one or more of the controllable switches S1, S2, S3 ', and S4', the current direction is switched, the four-phase full-bridge topology circuit is switched from the normal mode to the fault-tolerant mode, and another set of standby switching devices S1 ', S2', S3, and S4 is enabled to operate.

The method provided by the embodiment of the invention detects the current of each winding in real time, switches the working mode of the four-phase full-bridge topology circuit when the sum of the absolute values of the current of each winding is less than the preset current threshold value, so that a fault switch tube does not participate in current control, utilizes redundant switch elements to realize stable control on the magnetic suspension bearing system, can keep the system running without stopping under the fault-tolerant working condition, continues to maintain the suspension of the rotor in the magnetic suspension bearing system, ensures that the rotor does not fall off, and effectively improves the fault-tolerant capability of the magnetic suspension bearing system.

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 (7)

1. A magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit is characterized by comprising:

4 windings A₁、A₂、A₃、A₄4 bridge arms B₁、B₂、B₃、B₄And 1 DC voltage source;

bridge arm B₁、B₂、B₃、B₄Respectively with winding A₁、A₃、A₂、A₄Is connected to one end of winding A₁、A₃、A₂、A₄The other ends of the two are connected together to form a neutral point; wherein, winding A₁And A₃Electromagnetic force for controlling one degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing, winding A₂And A₄Control ofThe electromagnetic force of the other degree of freedom in the magnetic suspension two-degree-of-freedom radial bearing;

the bridge arm B₁、B₂、B₃、B₄The bridge comprises an upper bridge arm and a lower bridge arm, wherein the upper bridge arm and the lower bridge arm respectively comprise a controllable switch and a one-way conducting device which is connected with the controllable switch in an anti-parallel mode; the bridge arm B₁、B₂、B₃、B₄The upper node and the lower node are respectively connected with the anode and the cathode of the direct current voltage source;

the four-phase full-bridge topology circuit has a normal mode and a fault-tolerant mode, and in the normal mode, the bridge arm B₁、B₂The upper bridge arm controllable switch is closed, and the lower bridge arm controllable switch is opened; bridge arm B₃、B₄The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; in fault-tolerant mode, bridge arm B₁、B₂The upper bridge arm controllable switch is switched off, and the lower bridge arm controllable switch is switched on; bridge arm B₃、B₄The upper bridge arm controllable switch is closed and the lower bridge arm controllable switch is open.

2. The magnetically levitated two-degree-of-freedom radial bearing four-phase full-bridge topology circuit of claim 1, wherein the winding a is wound on a single winding₁And A₃The common mode current and the differential mode current of the magnetic suspension radial bearing control the electromagnetic force of one degree of freedom in the magnetic suspension radial bearing with two degrees of freedom, and the winding A₂And A₄The common mode current and the differential mode current of the magnetic suspension two-freedom-degree radial bearing control the electromagnetic force of the other freedom degree in the magnetic suspension two-freedom-degree radial bearing.

3. The magnetic levitation two-degree-of-freedom radial bearing four-phase full bridge topology circuit as claimed in any one of claims 1-2, wherein the controllable switch is an insulated gate bipolar transistor; the unidirectional conducting device is a diode.

4. The magnetically levitated two-degree-of-freedom radial bearing four-phase full-bridge topology circuit of claim 1, wherein the winding a is in a normal mode₁、A₂、A₃、A₄Current direction and fault-tolerant mode of winding a₁、A₂、A₃、A₄The current direction of (2) is opposite.

5. The magnetically levitated two-degree-of-freedom radial bearing four-phase full-bridge topology circuit of claim 4, wherein the winding A is in the normal mode₁、A₂、A₃、A₄Current direction and fault-tolerant mode of winding a₁、A₂、A₃、A₄Comprises the following steps:

in normal mode, winding A₁、A₃Has a current direction of bridge arm B₁、B₂Flows to the neutral point; winding A₂、A₄The current direction of the bridge arm B is from the neutral point₃、B₄A midpoint of (a);

in fault-tolerant mode, winding A₁、A₃The current direction of the bridge arm B is from the neutral point₁、B₂A midpoint of (a); winding A₂、A₄Has a current direction of bridge arm B₃、B₄Towards the neutral point.

6. The utility model provides a switch fault tolerant system that opens circuit of magnetic suspension two degree of freedom journal bearing four-phase full bridge topology circuit which characterized in that includes: a fault detection and mode switching module and a four-phase full bridge topology circuit according to any of claims 1-5;

the fault detection and mode switching module is used for winding A₁、A₃、A₂、A₄Is detected in real time, and the winding A is calculated₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a); if the winding A is₁、A₃、A₂、A₄If the sum of the absolute values of the currents is smaller than a preset current threshold value, the four-phase full-bridge topology circuit is switched from a normal mode to a fault-tolerant mode.

7. A switch open circuit fault tolerance method of a magnetic suspension two-degree-of-freedom radial bearing four-phase full-bridge topology circuit is applied to the four-phase full-bridge topology circuit according to any one of claims 1 to 5, and is characterized by comprising the following steps:

s101: real-time detection of winding A₁、A₃、A₂、A₄Calculating the current of said winding A₁、A₃、A₂、A₄The sum of the absolute values of the currents of (a);

s102: judging the winding A₁、A₃、A₂、A₄If the sum of the absolute values of (a) is less than the preset current threshold, if yes, go to step S103; if not, returning to the step S101;

s103: and switching the four-phase full-bridge topology circuit from a normal mode to a fault-tolerant mode.

Images