Disclosure of Invention
In order to solve the problem of coupling of torque current and suspension current of a magnetic suspension motor, the invention introduces a variable bias current control mode of a suspension system of the magnetic suspension motor, which solves the electromagnetic coupling of two radial degrees of freedom of a rotor and enables the magnetic suspension motor system to have excellent dynamic and static performances.
The technical scheme of the invention is as follows:
a magnetic suspension motor decoupling control device comprises:
the displacement measurement module comprises a position sensor for measuring the rotation angle of the rotor and a displacement sensor for measuring the position offset of the rotor;
the expected suspension force calculation module is used for obtaining expected suspension force which is to be generated under the corresponding rotor position offset by utilizing the rotor rotation angle and the rotor position offset;
the variable bias current module is used for obtaining bias current of each phase by combining expected suspension force;
the control current calculation module is used for obtaining the control current of each phase by combining the expected levitation force;
the actual suspension force calculation module is used for combining the bias current and the control current to obtain actual suspension force;
and the suspension force comparison module is used for comparing the actual suspension force with the expected suspension force and judging whether the motor completes suspension control.
A decoupling control method for a magnetic suspension motor comprises the following steps:
measuring the rotation angle and the position offset of the rotor;
obtaining an expected suspension force which is to be generated under the corresponding rotor position offset by combining the rotor rotation angle and the rotor position offset, wherein the expected suspension force is generated by the bias current and the control current;
obtaining the bias current of each phase of winding;
obtaining the control current of each phase of winding;
combining the bias current and the control current to obtain actual suspension force;
and comparing the actual suspension force with the expected suspension force, and judging whether the motor completes suspension control.
Preferably, the desired levitation force to be generated under the corresponding rotor position offset is obtained by combining the rotor rotation angle and the rotor position offset, and the specific process is as follows:
each phase of winding sequentially generates expected suspension force, and the expected suspension force generated by each phase of winding is converted to
Direction or
In the direction; if the position of the phase stator is equal to
Direction or
The directions are overlapped, so that decomposition is not needed; if the position of the phase stator is equal to
In the positive direction or
If the angle is deviated from the positive direction, the expected suspension force of the phase needs to be adjusted
、
Decompose to
Direction and
direction, respectively obtained for each respective generation
Period in the direction ofInspection of the suspension force and
a desired levitation force in a direction;
measuring rotor in
Positional deviation amount of direction
And is connected with the rotor
Comparing the central positions of the directions, inputting the difference into a PID controller, and calculating to obtain
Desired levitation force in a direction
(ii) a Measuring rotor in
Positional deviation amount of direction
With a rotor in
Comparing the central positions of the directions, inputting the difference into a PID controller, and calculating to obtain
Desired levitation force in a direction
。
Preferably, the method obtains the bias current of each phase of winding, and comprises the following specific processes:
continuation of each phase winding after torque control has been turned offCurrent of current
Will be as bias current of the levitation system
Providing a part of suspension force for the motor; the bias current is calculated as
Follow current in constant inductance state
Continuously decrease as the freewheeling current
Minimum bias current down to system floating
While supplying a fixed bias current to the levitation system
。
Preferably, the method obtains the control current of each phase winding, and comprises the following specific processes:
control current of motor suspension can be solved by voltage equation of magnetic suspension motor
Wherein, the first and the second end of the pipe are connected with each other,
Uthe voltage of each phase winding of the motor is obtained;
Rresistance of each phase winding;
for the flux linkage of each phase of the winding,
Lfor each phase of the winding inductance,
for the free-wheeling current generated by each phase winding after torque control is turned off,
the rate of change of flux linkage versus time for each phase of the winding,
the rate of change of control current versus time for each phase.
Preferably, the actual levitation force is obtained by combining the bias current and the control current, and the specific process is as follows:
calculating formula according to actual suspension force of suspension motor
It can be known that the current stiffness coefficient
And coefficient of displacement stiffness
Will be applied to the actual levitation force of the switched reluctance motor
Producing an influence; by
It is known that the bias current
Will result in a current stiffness coefficient
(ii) a change; by
It is known that the bias current
Will result in a displacement stiffness coefficient
(ii) a change;
wherein
In order to achieve a magnetic permeability in a vacuum,
;
Nthe number of turns of the winding coil;
Sis the area of the magnetic pole,
is the air gap length.
Preferably, the invention is based on the use of a bias current
Generated main magnetic flux
And control the current
Generated levitating magnetic flux
Or
The superposition generates the actual suspension force
(ii) a Will be provided with
Phase of each phase in the directionInspection of suspension force
And
actual suspension force in direction
Obtaining a suspension control signal G through hysteresis control
3 (ii) a Will be provided with
Desired levitation force per phase in direction
And with
Actual suspension force in direction
Obtaining a suspension control signal G through hysteresis control
4 。
Preferably, after the torque control system of the levitation motor is turned off, the torque current does not decrease to 0, and the torque current has an influence on levitation control; the variable bias suspension control method takes torque follow current as bias current of suspension control, and realizes suspension control of the motor by matching with the control current, thereby solving the coupling problem between torque and suspension control.
The invention has the advantages that:
1. the invention provides the suspension force by utilizing the torque-controlled follow current, and optimizes the suspension current decoupling performance of the magnetic suspension motor on the basis of the motor decoupling structure.
2. The variable bias current control can better adapt to the suspension force control under different suspension requirements, and reduces the suspension power consumption.
3. The invention relates to the construction of decoupling control on a suspension system of a magnetic suspension motor, is suitable for the balance control of a high-speed rotor of the magnetic suspension system with self-decoupling characteristic, provides conditions for the support of the high-speed rotor, and can be applied to the field of high-speed and ultrahigh-speed electric transmission.
Detailed Description
The technical scheme of the invention is explained in detail in the following with the accompanying drawings:
as shown in fig. 1, a logic block diagram of variable bias levitation force control, a decoupling control device for a magnetic levitation motor, includes:
the displacement measurement module comprises a position sensor for measuring the rotation angle of the rotor and a displacement sensor for measuring the position offset of the rotor;
the expected suspension force calculation module is used for obtaining expected suspension force which is to be generated under the corresponding rotor position offset by utilizing the rotor rotation angle and the rotor position offset;
the variable bias current module is used for obtaining bias current of each phase by combining the expected suspension force;
the control current calculation module is used for obtaining the control current of each phase by combining the expected suspension force;
the actual suspension force calculation module is used for combining the bias current and the control current to obtain actual suspension force;
and the suspension force comparison module is used for comparing the actual suspension force with the expected suspension force and judging whether the motor completes suspension control.
As shown in fig. 2, a variable bias suspension force control flowchart is a magnetic levitation motor decoupling control method, which includes the following steps:
measuring the rotation angle and the position offset of the rotor;
obtaining an expected suspension force which is to be generated under the corresponding rotor position offset by combining the rotor rotation angle and the rotor position offset, wherein the expected suspension force is generated by the bias current and the control current together; the specific process is as follows:
measuring rotor in
Positional deviation amount of direction
And is connected with the rotor
Comparing the central positions of the directions, inputting the difference into a PID controller, and calculating to obtain the expected suspension force
(ii) a Measuring rotor in
Positional deviation amount of direction
With a rotor in
Comparing the central positions of the directions, inputting the difference into a PID controller, and calculating to obtain the expected suspension force
;
Each phase of winding generates expected suspension force in turn, and the expected suspension force generated by each phase of winding is converted into
Direction or
In the direction; if the position of the phase stator is equal to
Direction or
The directions are overlapped, so that decomposition is not needed; if the position of the phase stator is equal to
In the positive direction or
If the angle is deviated from the positive direction, the expected suspension force of the phase needs to be adjusted
、
Decompose to
Direction and
directions, respectively obtained for each correspondingly generated
Levitating force in the direction of and
suspension force in the direction.
Obtaining the bias current of each phase of winding, and the specific process is as follows:
free-wheeling current generated by each phase winding after torque control is turned off
Will be as bias current of the levitation system
Providing a part of suspension force for the motor; biasingThe current is calculated as
Follow current in constant inductance state
Continuously decrease as the freewheeling current
Minimum bias current down to system float
While providing a fixed bias current to the levitation system
。
And obtaining the control current of each phase of winding, wherein the specific process comprises the following steps:
control current of motor suspension can be solved by voltage equation of magnetic suspension motor
Wherein, the first and the second end of the pipe are connected with each other,
Uthe voltage of each phase winding of the motor is obtained;
Rresistance of each phase winding;
for the flux linkage of each phase winding,
Lfor each phase of the winding inductance,
for the free-wheeling current generated by each phase winding after torque control is turned off,
the rate of change of flux linkage versus time for each phase of the winding,
the rate of change of current versus time is controlled for each phase.
The actual suspension force is obtained by combining the bias current and the control current, and the specific process is as follows:
calculating formula according to actual suspension force of suspension motor
It can be known that the current stiffness coefficient
And coefficient of displacement stiffness
Will be to the suspension force of the switch reluctance motor
Producing an influence; by
It is known that the bias current
Will result in a current stiffness coefficient
(ii) a change; by
It is known that the bias current
Will result in a displacement stiffness coefficient
(ii) a change;
wherein
In order to achieve a magnetic permeability in a vacuum,
;
Nthe number of turns of the winding coil;
Sis the area of the magnetic pole,
is the air gap length.
By bias current
Generated main magnetic flux
And control the current
The generated levitation magnetic flux
Or
The superposition generates the actual suspension force
、
. Will be provided with
Desired levitation force per phase in direction
With actual levitation force
ThroughHysteresis control to obtain a suspension control signal G
3 . Will be provided with
Desired levitation force per phase in the direction
With actual levitation force
Obtaining a suspension control signal G through hysteresis control
4 。
After a torque control system of the levitation motor is turned off, the torque current is not reduced to 0, and the torque current has influence on levitation control; the variable bias suspension control method takes torque follow current as bias current of suspension control, and realizes suspension control of the motor together by matching with control current, so that the coupling problem between torque and suspension control is solved.
A decoupling control method for a magnetic suspension motor comprises the following steps:
a magnetic suspension motor is selected, and a torque system and a suspension system of the magnetic suspension motor have the self-decoupling characteristic. Carrying out rotating speed and current double closed-loop control on a torque system to set the rotating speed
And the actual rotational speed
The difference value of the voltage difference is obtained by a PID controller to obtain the control current of the motor
Controlling the current
And three-phase actual current
Current chopping control is carried out on the motor to obtain a control signal G
1 . Displacement measuring moduleObtained rotor rotation angle
Obtaining a torque conducting signal G of each phase winding of the motor through logic judgment of a switching signal
2 . Chopping current control signal G
1 And torque conducting signal G
2 Combining to obtain total control signal
And driving the power converter to control the torque of the magnetic suspension motor.
The magnetic suspension motor has self-decoupling characteristic. And the phase A performs torque control in an inductance rising area, after the torque conduction is finished, the inductance is positioned in an upper flat top area, the phase A performs suspension control at any time, and meanwhile, the phase B starts to rise to perform torque control on the phase B.
The suspension system performs displacement and suspension force double closed-loop control. Measuring rotor in
Displacement in direction
Comparing with the central position x, calculating to obtain the expected suspension force through a PID controller
(ii) a Measuring rotor in
Displacement in direction
Comparing with the central position y, calculating to obtain the expected suspension force through a PID controller
. In the radial suspension control process of the rotor, the suspension force is decomposed into
、
Directional equivalent radial force.
Suspension force in direction
Decomposing the suspension force into each phase, calculating to obtain the corresponding suspension force generated on each phase of winding of the motor according to the motor structure, and calculating the expected suspension force and the actual suspension force of each phase of winding
Obtaining a signal G through hysteresis control
3 ;
Suspension force in direction
Decomposing the magnetic field into each phase, calculating to obtain the corresponding suspension force on each phase winding, and comparing the expected suspension force with the actual suspension force
Obtaining a signal G through hysteresis control
4 。G
3 And G
4 Synthesized total control signal
And carrying out suspension control on the motor.
Current follow current generated by each phase winding after torque control is turned off
Will be used as bias current of the levitation system
And provides a part of suspension force for the motor. The follow current is continuously attenuated to the minimum bias current
Then, a constant bias current is given to the system
. By bias current
Generated main magnetic flux
And control the current
Generated levitating magnetic flux
Or
The suspension force is generated by superposition.
Performing double closed loop control of rotation speed and current on a torque system, such as the torque and suspension control block diagram of a magnetic suspension motor shown in FIG. 3, and setting the rotation speed
And the actual rotational speed
The difference value of the voltage difference is obtained by a PID controller to obtain the control current of the motor
Controlling the current
Phase current of actual phase
Current chopping is carried out on the motor to obtain a control signal G
1 . By rotor rotation angle
Controlling the conduction of each phase winding in different rotor position angle intervals to obtain a torque conduction signal G
2 . Control signal G
1 And torque conducting signal G
2 Combining to obtain total control signal
And driving a power converter to control the torque of the magnetic suspension motor.
During current chopping control, the relationship between each phase current and the rotor angle is shown as a current chopping waveform diagram in fig. 4.
The average value of the upper and lower limits of current chopping is shown. After torque off
To
Where the rate of change of the current in the winding is
Wherein the content of the first and second substances,
is the phase voltage of the windings,
in order to determine the angular velocity of the rotor,
is wound aroundThe maximum value of the group inductance is,
for winding current versus rotor rotation angle
The rate of change of (c).
Taking the maximum current chopping limit as
The minimum limit of current chopping is
. Torque follow current
Is expressed as
Current follow current generated by each phase winding after torque control is turned off
Will be used as bias current of the levitation system
And provides a part of suspension force for the motor. The follow current is continuously attenuated to the minimum bias current
Then, a constant bias current is given to the system
。
The logic block diagram of the levitation control is shown in fig. 3, and a direct levitation force control mode is adopted. With a rotor
Taking the direction as an example, the position signal sensor measures the displacement offset of the rotor
Compared with the central position, the expected suspension force is obtained through the calculation of a PID controller
。
Suspension force in direction
Decomposing the solution into each phase, and calculating to obtain the corresponding suspension force generated on each phase.
Determining torque current
With floating minimum bias current
The magnitude relationship of (1). If torque current
Greater than the minimum floating bias current
Then find out and
corresponding current stiffness coefficient
And coefficient of displacement stiffness
The following:
wherein the magnetic permeability of vacuum
;
NThe number of turns of the winding coil;
Sis the area of the magnetic pole, and the magnetic pole area,
is the air gap length.
Follow current of torque
I.e. the levitation bias current is also decreasing, if the torque current is
Less than suspended minimum bias current
Then, the calculation is performed according to the formula (3)
And corresponding to the fixed current stiffness coefficient and the fixed displacement stiffness coefficient. Current stiffness coefficient
Is composed of
Coefficient of displacement stiffness
Is composed of
The control current of the motor suspension can be solved by the voltage equation of the switched reluctance motor
Determining bias current
Generated main magnetic flux
And controlling the current
Generated levitating magnetic flux
Or
In the direction of (a). By bias current
Generated main magnetic flux
And control the current
Generated levitating magnetic flux
Or
The suspension force is generated by superposition. Desired suspending force of each phase
And actual levitation force
Obtaining a suspension control signal G through hysteresis control
3 。
Offset the displacement of the rotor
Comparing with the central point, and performing closed-loop control by a PID controller; each phase is wound at
Total suspension force generated in direction
With desired levitation force
And performing closed-loop control by a hysteresis controller.
The same direction can make the motor stably suspend.
Enabling torque to follow current as bias current of suspension control through variable bias suspension control method
In coordination with controlling the current
The suspension control of the motor is realized together, the problem that the suspension control is coupled due to the fact that the current of the winding is not 0 after the torque control is finished is solved, the torque control and the suspension control are decoupled, and the control of the suspension motor is facilitated.