JP3053121B2 - Control method of induction motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method utilizing vector control of an induction motor, and more particularly to a control method used for a high-speed spindle drive of a machine tool.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a system. This system includes an induction motor a, a rotation speed detector b attached thereto, and an inverter device c that detects the rotation speed and drives the induction motor a.

In the prior art, at low speed rotation, an inverter device c performs vector control with a speed sensor based on a detection signal ωr of a rotation speed detector b to drive an induction motor. However, when servo performance is required during low-speed operation or when a high-resolution rotation speed detector b is required to perform positioning control, the detection signal ωr of the rotation speed The detection signal ωr of the rotation speed detector b does not output a correct speed detection amount due to the detection signal ωr being attenuated and not being correctly transmitted to the inverter device c or the operation delay of the detection circuit in the rotation speed detector b. Therefore, vector control with a speed sensor cannot be performed. Therefore, conventionally, at high speed rotation, the induction motor is driven by V / f constant control which does not require the detection signal ωr of the rotation speed detector b.

[0004]

However, in the prior art, there is a problem that the speed control that can be performed by the vector control with the speed sensor cannot be performed in a high-speed rotation region where the V / f constant control is performed. Therefore, an object of the present invention is to enable speed control even in a high-speed rotation region.

[0005]

In order to solve the above problems SUMMARY OF THE INVENTION The control method of the induction motor of the present invention, the induction motor times
A rotation speed detector for detecting a rotation speed, and a speed of the rotation speed detector.
The speed detection signal and the speed command given to the inverter
As an input, control is performed so that the actual speed matches the command speed.
Speed control unit and inverter output detection voltage or
And a control signal corresponding to
Input the corresponding control signal and
Magnetic flux / torque current estimator that outputs constant value and magnetic flux estimated value
And a torque current command output from the speed control unit and a torque
Torque for calculating speed signal by comparing and controlling estimated current value
A current control unit and a speed calculated by the torque current control unit
The slip frequency is the ratio of the signal to the motor's torque current and magnetic flux.
Based on the motor circuit constant
Slip frequency to calculate the slip frequency required for torque control
A computing unit, provided on the output side of the torque current control unit,
The motor circuit constant is determined by the torque current command and the estimated torque current.
A motor circuit constant correction unit that corrects to match,
Select the output of the torque current controller and the output of the rotation speed detector.
And a switch for selectively outputting.
If the speed is lower than the upper limit speed at which the correct rotation speed can be detected,
Outputting the output of the rotation speed detector as a speed detection signal
Performs vector control with a speed sensor, and the rotation speed detector
If the speed is higher than the upper limit speed at which the correct rotation speed can be detected,
Outputting the output of the torque current control unit as a speed signal
Speed sensorless vector control and speed sensor
During the response vector control, the speed
Motor circuit constants corrected during vector control with sensor
And is used as a motor circuit constant .

[0006]

According to the present invention, speed sensorless vector control, which has lower control performance at high speed rotation than vector control with speed sensor but can perform speed control which cannot be performed by V / f constant control, is applied. Thus, speed control can be performed even in a high-speed rotation region.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described below with reference to the control block diagram of FIG. This system is an induction motor 1
And an inverter 3 for detecting the number of rotations and driving the induction motor 1 by detecting the number of rotations. The inverter device 3 includes a speed controller 4, a magnetic flux controller 5, a current controller 6, a magnetic flux / torque current estimator 7, a torque current controller 8, a slip frequency calculator 9 including a motor circuit constant 10, and a motor circuit constant . A correction unit 11, a switch 12 for switching between a speed detection value and a speed estimation value, a primary current command generator 13, an excitation inductance function 14, a multiplier 15,
The power conversion unit 16 includes an integrator 17.

In the vector control, generally, a torque generation mechanism of a motor is obtained by a mathematical solution, and is inversely expanded to control a voltage, a frequency, and a phase applied to the motor so as to generate a torque in accordance with a torque command. Things. If this mathematical solution is simplified and expressed, it is as shown in equations (1) to (7). = Torque _{T = kφ 2 I T (1} ) exciting current amplitude _{I M (1 / M) φ} 2 (2) 1 primary current amplitudes ^{_{I 1 = √ (I M 2}} + I T 2) (3) 1 primary current delay angle ^{_{θ T = tan -1 (I T}} / I M) (4) 1 primary frequency _{ω 1 = ωr + ωs (5} ) 1 primary current vector _{I 1 = I 1 ∠θ 1 (} 6) slip frequency ωs = Ks (I _T / Φ ₂ ) (7) Therefore, the inverter performs vector control based on equations (1) to (7). Where Ks is the torque current of the motor
And the coefficient that converts the ratio of magnetic flux to slip frequency ωs.
Called the (true) motor circuit constant. The magnetic flux controller 5 controls so that the command magnetic flux phi ₂ ^* and estimated flux value phi ₂ are identical, the excitation inductance function as its output (2) 14
, Is converted into an excitation current command I _M ^* . The output of the speed control unit 4 is regarded as a torque current command I _T ^*, and the primary current command generator 13 outputs I ₁ ^* and θ based on the equations (3) and (4).
Output _T ^* . On the other hand, the primary frequency calculation is performed by the slip frequency calculator 9 based on the equation (7), and outputs a slip frequency signal ωs ^* . (5) Based on the formula, by adding the speed signal ωr and the slip frequency signal .omega.s ^* make primary frequency signals omega _1, which integrated value and primary current delay angle theta _T ^* added by the integrator 17 Thus, a primary current phase angle θ ₁ ^* is generated.
The multiplier 15 calculates the primary current command amplitude I ₁ ^* based on the equation (6) ^.
And θ ₁ ^* to generate a primary current command vector I ₁ ^* . The current command unit 6 generates a primary voltage command vector V ₁ ^* so that the same current as the primary current command vector flows, and the power conversion unit 17 generates a necessary voltage, frequency, and phase. Give to. In the flux-torque current estimation unit 7, the primary current vector I ₁ and the primary voltage command vector V ₁ ^* from the torque current estimated value I _T and the magnetic flux estimation value phi ₂ is obtained. May use the inverter output voltages V ₁ instead of the primary voltage command vector V ₁ ^*.

In the present invention, when the speed of the induction motor 1 is lower than the upper limit speed at which the rotation speed detector 2 can accurately detect the rotation speed, the switch 12 switches the signal of the rotation speed detector 2 to the speed signal ωr. Then, the vector control with the speed sensor is performed. At the same time, the torque current command I _T ^*
And inputting the torque current estimated value I _T to the torque current controller 8. Here, the estimated torque current value can be expressed as follows from equation (7). I _T = (ωsφ ₂ ) / Ks (8) The magnetic flux estimated value φ ₂ is obtained from the magnetic flux controller 5 by the command magnetic flux φ _2.
Since it is controlled to match ^* , φ ₂ ^* is considered equal to φ ₂ . In addition, the output of the rotation speed detector 2 is set to 1
The actual slip frequency ωs is equal to the slip frequency signal ωs ^* because it is used in the following equation (5). Therefore, the torque current command I _T ^* can be expressed by the following equation. I _T ^* = (ωsφ ₂ ) / Ks ^* (9) Here, Ks ^* is a motor circuit constant output by the motor circuit constant correction unit 11. Therefore, the difference in the torque current command I _T ^* and the torque current estimated value I _T is caused since the motor circuit constant Ks ^* does not match the true motor circuit constant Ks. Therefore the torque current controller 8, when with the speed sensor vector control, by correcting the motor circuit constant Ks ^* as the torque current command I _T ^* and the torque current estimated value I _T is matched, the true motor circuit constant Ks ^* Has the function of approaching the motor circuit constant Ks.

In the present invention, when the speed of the induction motor 1 becomes higher than the upper limit speed at which the rotation speed detector 2 can detect an accurate rotation speed, the vector control with the speed sensor is performed as described in the section of the prior art. Switch 12
Is set so that the output side of the torque current controller 8 becomes the speed signal ωr, and the speed sensorless vector control is performed. Here, the motor circuit constant correction unit 11 holds the value of Ks ^* used in the vector control with the speed sensor. Motor times
Assuming that the path constant Ks ^* is equal to the true motor circuit constant Ks, equation (9) can be expressed as follows. _{^{I T * = (ωs * φ}} 2) / Ks (9) ' Thus, (8), (9)' difference in torque than formula current command I _T ^* and the torque current estimated value I _T is the slip frequency signal .omega.s ^* And the true slip frequency ωs. Therefore, the torque current controller 8 sets the torque current command I _T ^*
The torque current estimated value I _T to match, have the ability to estimate the motor speed ωr and. If the motor circuit constant Ks ^* is equal to the true motor circuit constant Ks, the motor speed will be exactly equal to the motor speed estimate ωr. As described above, even in the speed sensorless vector control, since the motor speed estimation value ωr is provided, the speed of the induction motor 1 can be controlled.

[0011]

As described above, according to the present invention,
Even when the rotational speed detector is higher than the upper limit speed at which an accurate rotational speed can be detected, the speed of the induction motor can be controlled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a system configuration diagram of an induction motor control device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 induction motor, 2 rotation speed detector, 3 inverter device, 4 speed control unit 5 magnetic flux control unit, 6 current control unit, 7 magnetic flux / torque current estimator 8 torque current controller, 9 slip frequency calculator, 10
Motor circuit constant 11 Motor circuit constant correction unit , 12 switch, 13
Primary current command generator 14 Excitation inductance function, 15 Multiplier, 16
Power converter 17 integrator 18 current detector 19 voltage detector .omega.r ^* speed command .omega.r speed detection signal I _T ^* torque current command I _T torque current estimated value phi ₂ ^* command flux phi ₂ flux estimation value I _M ^* excitation current command I ₁ ^* 1 primary current command I ₁ ^* 1 primary current command vector I ₁ 1 primary current vector V ₁ ^* 1 primary voltage command vector V ₁ inverter output voltage omega ₁ 1 primary frequency theta _T ^* 1 primary current lag angle theta ₁ ^* Primary current phase angle ωs ^* Slip frequency command

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 21/00 H02P 5/408-5/412 H02P 7/628-7/632

Claims (1)

(57) [Claims] A rotational speed detector for detecting a rotational speed of an induction motor.
Output device (2), a speed detection signal of the rotation speed detector (2), and an inverter
The speed command given to the device is input and the
A speed control unit (4) for controlling the speeds to match, and an output detection voltage of the inverter or a control signal corresponding thereto.
Signal and inverter output detection current or equivalent
With control signal as input, estimated torque current and estimated magnetic flux
And a torque current command output from the speed control unit (4).
Torque for calculating speed signal by comparing and controlling the estimated current value
A torque current control unit (8); a speed signal calculated by the torque current control unit (8);
Converts the ratio of motor torque current to magnetic flux to slip frequency
Control based on the motor circuit constant
Frequency calculator for calculating the required slip frequency
(9) , provided on the output side of the torque current control unit (8),
The torque circuit command and the torque current estimated value match
A motor circuit constant correction unit (11) for correcting the rotation speed, an output of the torque current control unit (8), and the rotation speed detector
A switch (12) for selectively outputting the output of (2).
An upper limit speed at which the rotation speed detector can detect an accurate rotation speed.
If smaller, the output of the rotation speed detector (2) is increased.
Output as a degree detection signal and perform vector control with a speed sensor.
The upper limit speed at which the rotation speed detector can detect an accurate rotation speed.
If larger, the output of the torque current controller (8)
Output as speed signal and speed sensorless vector control
And at the time of speed sensorless vector control, the switch
Corrected during vector control with speed sensor at the time of switching
Motor circuit constants and use them as motor circuit constants
A method for controlling an induction motor.