JPH0638574A - Motor controller for induction motor - Google Patents

Abstract

PURPOSE:To provide a vector controller which makes compensation for a secondary resistance change possible with simple construction and increases control accuracy. CONSTITUTION:A subtracting part 9 finds an error component DELTAI1q from a detected torque current I1q and a torque current command I1q*. A PI (proportional plus integral) calculating part 10 finds a correction component DELTAtau2 for a secondary time constant from the error component DELTAI1q. A slip calculating part 11 corrects the secondary time constant tau2 with the correction component DELTAtau2. A slip angular frequency omegas is calculated by the use of the secondary time constant tau2 corrected. While, a subtracting part 14 finds an error component DELTAI1d from a detected exciting current I1d and an exciting current command I1qd*. A PI calculating part 15 finds a voltage correction component DELTAV1d* form the error component DELTAI1d. And a subtracting part 16 corrects a voltage command V1d* by use of the error component DELTAV1d*. Correction accuracy of the secondary time constant tau2 is raised by raising the accuracy of the secondary magnetic flux control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor vector control device, and more particularly to a device for compensating for a variation in secondary resistance of an induction motor.

[0002]

2. Description of the Related Art A vector controller for an induction motor attempts to obtain high-performance variable speed control by always making the secondary magnetic flux of the electric motor and the secondary current orthogonal to each other. A vector operation is performed to control the following currents so that they do not interfere with each other.

In the conventional voltage-type vector calculation, it is assumed that the internal constant of the motor is known, and then the exciting current command I _1d * and the torque current command I _1q * are calculated by using the equations (1) and (2).
The primary voltage biaxial components V _1d * and V _1q * are obtained from (dq axis components of the primary current. However, the dq axes are rotation orthogonal coordinates with the secondary magnetic flux as the reference axis).

[0004]

## EQU1 ## V _1d * = R ₁ I _1d * -ω ₁ LσI _1q * (1)

[0005]

V _1q * = ω ₁ L ₁ I _1d * + R ₁ I _1q * (2) where Lσ = (L ₁ L ₂ −M ² ) / L ₂ and L ₁ is the primary of the motor Inductance, L ₂ is a secondary inductance, R ₁ is a primary resistance, and ω ₁ is a primary (output) frequency.

Further, the slip angular frequency ω _S is calculated using the quadratic time constant τ ₂ obtained by the equation (3).

[0007]

Τ ₂ = L ₂ / R ₂ (3)

[0008]

Of the above internal constants of the electric motor, the inductance component has little variation with temperature, but the resistance value of the secondary resistance R ₂ etc. varies with temperature.
Therefore, the internal constant fluctuates depending on the temperature, the above assumption is no longer satisfied, and the torque component current and the generated torque become non-proportional due to deviation from the vector control condition, and an unstable phenomenon such as overshoot occurs when the torque fluctuates. .

Various methods for compensating for fluctuations in the secondary resistance have been proposed in the past. For example, a method of measuring the temperature of an electric motor to compensate for a change in resistance, or measuring the magnetic flux on the secondary side with a magnetic sensor. There is a method to replace the magnetic flux calculation with
There is a problem that an additional device such as a high-precision sensor is required, and the signal to be handled is analog, so that it is susceptible to noise.

In view of such a problem, an object of the present invention is to provide a vector control device capable of compensating for a change in secondary resistance with a simple structure and improving control accuracy.

[0011]

In order to achieve the above object, the present invention provides a secondary resistance and other internal constants of a motor as set values, and performs voltage type vector control calculation using the set values. A vector control device for calculating an excitation axis component and a torque axis component of an output voltage from an excitation current command and a torque current command is provided with the following means.

(1) Calculation means for detecting a deviation between the torque current command and the detected torque current. Examples of the method of detecting the deviation include a method of taking the input difference and performing proportional integration.

(2) Correcting means for correcting the set value of the secondary resistance with reference to the value detected by the torque current deviation calculating means being zero. It is preferable that this correcting means corrects the set value of the secondary resistance used for calculating the slip angular frequency from the exciting current and the torque current, for example.

In addition to the above means, the following means can be provided.

(1) Calculation means for detecting the deviation between the exciting current command and the detected exciting current.

(2) Correction means for correcting the excitation axis component of the output voltage using the detection value of the excitation current deviation calculation means as the correction component.

[0017]

According to the present invention, the error component of the torque current when the electric motor is ideally controlled by the vector control is caused by the error of the secondary resistance setting value, and the torque current error component is set to zero. In addition, the secondary resistance variation is compensated by correcting the secondary resistance set value used for calculating the slip angular frequency, for example. Also, if the secondary magnetic flux deviates from the target, it will cause an error in the above-mentioned secondary resistance correction operation, so correct the excitation axis component of the output voltage (command) so that the excitation current error component becomes zero. Suppresses the deviation of the secondary magnetic flux.

[0018]

1 shows a vector control device according to an embodiment of the present invention. In FIG. 1, a voltage-type vector calculation unit 1
Is the excitation current command I _1d *, the motor torque current command I _1q * and the inverter output frequency ω using the equations (1) and (2).
₁ from those for calculating the motor primary d-axis and q-axis voltage command V _id * and V _iq *. PWM control inverter 2
, The voltage command V _id *, performs PWM operation on the basis of V _iq *, is to control the speed squirrel cage induction motor 3 by operating the inverter main circuit by using a pulse pattern obtained by this calculation.

The speed detector 4 has a rotation sensor for obtaining a speed detection pulse of several pulses per rotation from the shaft or gear output of the electric motor 3, and obtains the detection frequency ω _r from this detection pulse. The cushion circuit 5 uses the frequency command ω _r
It is intended to mitigate the impact of changes in *. The speed control amplifier 6 obtains the torque current command I _1q * by matching the detected frequency ω _r and the frequency command ω _r * and performing PI calculation.

The current detector 7 detects the phase currents I _U , I _V ,
I _W is detected. The coordinate conversion unit 8 determines the rotation coordinates dq from the phase θ and converts the phase currents I _U , I _V , and I _W into the currents I _1d and I _1q based on the rotation coordinates dq. The subtracting unit 9 detects the detected torque current I _1q and the torque current command I _1q *
The error component ΔI _1q is obtained by matching and.
PI calculation unit 10 is a proportionally integrating the error component [Delta] I _1q obtaining a correction component △ tau ₂ of the secondary time constant tau ₂ (secondary resistance). The slip calculation unit 11 calculates the slip angular frequency ω _S from the excitation current command I _1d * and the motor torque current command I _1q * using the equation (3), and at this time, the correction from the PI calculation unit 10 is performed. command △ tau ₂ by a secondary time constant tau ₂ corrected by performing a calculation. The output frequency calculation unit 12 calculates the primary (output) frequency ω ₁ from the slip angular frequency ω _S and the detection frequency ω _r.
Is calculated. The phase calculator 13 calculates the phase θ from the output frequency ω ₁ .

The subtraction unit 14 matches the detected exciting current I _1d with the exciting current command I _1d * to obtain the error component ΔI _1d . The PI calculator 15 proportionally integrates the error component ΔI _1d to obtain the voltage correction component ΔV _1d *. The subtraction unit 16 uses the error component ΔV _1d to generate the voltage command V _1d.
It corrects *.

In such a configuration, the error component Δ of the torque current when the magnetic flux current and the torque current are ideally controlled
It is considered that I _1q is caused by an error in the secondary time constant setting value used in the calculation of the slip angular frequency, that is, an error in the secondary resistance setting value (the secondary inductance has extremely small fluctuation). Therefore to get the correction component .DELTA..tau ₂ of the torque current error components [Delta] I _1q from the secondary time constant tau ₂ by PI calculating unit 10, the error component [Delta] I _1q by this correction component .DELTA..tau ₂ corrects the secondary time constant tau ₂ The secondary resistance R is set to zero.
Perform temperature compensation of ₂ .

Here, when the response of the secondary resistance correction is made faster, the actual secondary magnetic flux may deviate from the phase to be controlled, and an error occurs in the estimation of the secondary resistance variation. Therefore, the subtraction unit 14 by obtains the voltage command V _1d * of compensation value [Delta] V _1d * from the exciting current error components [Delta] I _1d, error components [Delta] _1d by correcting the voltage command V _1d * The correction component [Delta] V _1d * To zero. This suppresses the deviation of the secondary magnetic flux and suppresses the error in the secondary resistance estimation.

Further, the above-mentioned model calculation formula is a steady-state formula, and a voltage due to a current differential term is generated in an actual electric motor during a transition when a speed or a load changes suddenly, and an error occurs in estimation of a secondary resistance variation. Cause. Therefore, for example, when the current command changes, a PI circuit 10 is provided with a switch circuit that prohibits correction of the secondary time constant for a certain period from the change time.
Insert it in the subsequent stage. Alternatively, focusing on the fact that the current differential term is a high frequency component, a low-pass filter or the like is inserted in the subsequent stage of the subtraction unit 9 or the like.

Although the secondary time constant τ ₂ and the voltage command V _1d * are corrected in the embodiment by the method of correcting the set value or the calculated value, for example, the set value of the secondary resistor R ₂ is directly corrected. Various modes for directly or indirectly compensating for a target parameter, such as a configuration and a configuration for correcting the slip angular frequency ω _S , can be adopted.

[0026]

As described above, according to the present invention,
In order to correct the secondary resistance setting value so that the deviation between the torque current command of the electric motor and the detected torque current during constant time becomes zero,
It has the following effects.

(1) Since the parameter correction component for secondary resistance compensation is obtained based on the deviation between the command value and the detected value of the torque current component, the control configuration is simple and the amount of calculation is small. -A vector controller can be realized by a microcomputer.

(2) Since the above deviation can be calculated for each PWM calculation cycle, it is possible to perform secondary resistance compensation with excellent responsiveness.

(3) Since the calculation error of the slip angular frequency is suppressed even when the internal temperature of the electric motor fluctuates,
The linearity of the actual torque is improved, and high torque control accuracy can be obtained.

(4) The accuracy of the induction motor model is ensured by the vector calculation, and the accuracy of the secondary magnetic flux constant control is improved by feeding back the error between the command value and the detected value of the exciting current. It becomes possible to control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a vector control device according to an embodiment of the present invention.

[Explanation of symbols]

7 ... Current detector 8 ... Coordinate conversion unit 9 ... Subtraction unit for _obtaining torque current error component ΔI _1q 10 ... PI calculation unit for obtaining secondary time constant correction component Δτ ₂ 11 ... Slip calculation unit 14 ... Excitation current error Subtraction unit for obtaining component ΔI _1d 15 ... PI calculation unit for obtaining correction component ΔV _1d * of voltage command 16 ... Subtraction unit for correcting voltage command V _1d *

Claims (3)

[Claims] 1. An internal constant of a motor such as a secondary resistance is given as a set value, a voltage type vector control calculation is performed using the set value, and an exciting axis component and a torque of an output voltage from an exciting current command and a torque current command. In a vector control device for calculating an axial component, a calculation means for detecting a deviation between the torque current command and the detected torque current, and setting of the secondary resistance on the basis of setting a detection value of the torque current deviation calculation means to zero. A vector control device for an induction motor, comprising: a correction unit that corrects a value. 2. The vector control device for an induction motor according to claim 1, wherein the correction means corrects a set value of a secondary resistance used in calculating a slip angular frequency from an exciting current and a torque current. A vector control device for an induction motor, characterized by being a thing. 3. The vector controller for an induction motor according to claim 1, wherein the exciting current command and a deviation of the detected exciting current are detected by a calculating means, and a detected value of the exciting current deviation calculating means is used as a correction component. A vector control device for an induction motor, comprising: a correction unit that corrects an excitation axis component of the output voltage.