JP4760064B2 - Induction motor control method - Google Patents

Description

  The present invention relates to a control method for an induction motor that drives the motor at a variable speed by speed sensorless vector control of the induction motor using an adaptive secondary magnetic flux observer.

  FIG. 5 is a circuit configuration diagram showing a conventional example of a speed control device for an induction motor that performs this type of speed sensorless vector control.

  The speed control device shown in FIG. 5 includes a power converter 1 that supplies desired AC power to the induction motor 100, and a current detector that detects a primary current and a primary voltage from the power converter 1 to the induction motor 100, respectively. 2, a voltage detector 3 and a control unit 10 comprising a vector control system part and an adaptive secondary magnetic flux observer system part for variable speed control of the induction motor 100 via the power converter 1 based on the commanded speed command value. And.

  The vector control system portion is based on an adjustment calculation value that makes a deviation between a commanded speed command value and a rotational speed estimated value, which will be described later, zero, and a secondary magnetic flux estimated value of the induction motor 100, which will be described later. A speed adjusting means 11 for generating a value, a coordinate converting means 12 for converting the detected value of the primary current of the induction motor 100 from the current detector 2 into a detected value of torque current and exciting current of the motor, and the torque current A voltage command for the torque component of the motor based on an adjustment calculation value that makes the deviation between the command value and the detected value of the torque current zero, the secondary magnetic flux estimated value, and primary and secondary resistance estimated values of the induction motor 100 described later. Induction electric motor based on torque current adjusting means 13 for generating a value, an adjustment calculation value for making the deviation between the commanded excitation current command value and the detected value of the excitation current zero, and the primary / secondary resistance estimation values Excitation current adjusting means 14 for generating a voltage command value of 100 excitation components; slip frequency control means 15 for generating a primary frequency of the induction motor 100 based on the rotational speed estimated value and primary / secondary resistance estimated value; Coordinate reverse conversion means 16 for generating a three-phase voltage command value (AC amount) to the power converter 1 by performing coordinate reverse conversion based on the voltage command value and primary frequency of the torque component and excitation component, The speed adjusting means 11, the coordinate converting means 12, the torque current adjusting means 13, the exciting current adjusting means 14, the slip frequency controlling means 15, and the coordinate reverse converting means 16 are each formed by a known technique.

  The adaptive secondary magnetic flux observer system portion includes a current / magnetic flux observer 21, an observer gain setting device 22, and a rotational speed / resistance estimating means 23. The current / magnetic flux observer 21 includes the primary current of the induction motor 100, The primary resistance, secondary resistance, and rotation speed in the state equation with the secondary magnetic flux as a state variable are replaced with estimated values, respectively, and the respective values of the observer gain setting unit 22 are replaced with estimated errors of the torque current and excitation current of the motor. Based on the sum of the multiplied and fed back value and the primary voltage of the motor from the voltage detector 3, the estimated values of the torque current, excitation current, and secondary magnetic flux of the induction motor 100 are calculated. When this is expressed by a formula, the following formula 1 is obtained.

  The observer gain matrix G for determining the dynamic characteristics in the above equation is expressed by the following equation 2 and is set by the observer gain setting unit 22.

  Since the estimated value is used as a parameter in the current / magnetic flux observer 21 described above, if there is an error in the estimated value, the estimated value of each of the torque current and the excitation current of the induction motor 100 includes an error. Therefore, an adaptive estimation mechanism is added in the speed sensorless control using the adaptive secondary magnetic flux observer so that the error is eliminated, and the estimated values of the rotation speed, primary resistance value, and secondary resistance value of the induction motor 100 are rotated. The speed / resistance estimator 23 derives it based on the following equation (3).

Hidehiko Sugimoto, et al. “Improvement of Stability of Speed Sensorless Vector Control of Induction Motors” 2001 Annual Conference of the Institute of Electrical Engineers of Japan, 4-109, March 21, 2001

  For each element of the observer gain matrix G expressed by the equation 2, the non-patent document 1 and the like are set as expressed by the following equation 4.

  However, in the conventional method for setting the observer gain matrix G expressed by the above equation 4, when the rotational speed of the induction motor that performs speed sensorless vector control is low, the speed estimation error may not converge for a long time.

  An object of the present invention is to provide a method of controlling an induction motor that solves the above problems.

The present invention relates to a control method for an induction motor that drives the motor at a variable speed by speed sensorless vector control of the induction motor using an adaptive secondary magnetic flux observer.
An estimated value of the rotational speed of the electric motor is derived based on a value obtained by proportional-integral calculation of the phase and gain compensated for the phase and gain of the lead / lag characteristic with respect to the deviation between the estimated value of the torque current of the induction motor and its actual value. The control method characterized by doing is performed.

  A method for controlling an induction motor according to the present invention will be described below with reference to the drawings.

  FIG. 3 is a block diagram showing an equivalent feedback system related to an error of a state variable in speed sensorless vector control of the induction motor.

That is, in a conventional induction motor speed control device, when a round transfer function G (s) from the rotation speed of the induction motor 100 to the estimated rotation speed is obtained, it is expressed by the following equation (5). Here, G ₁ (s) represents a transfer function that outputs an error between state variables of the observer and the induction motor, and G _n (s) is a transfer function including an induction motor secondary resistance and a rotational speed estimator. .

In Equation 5, K _RrP and Kω _P are proportional gains of the _estimator , and K _RrI and Kω _I are integral gains. G ₂₂ is an element in the second row and second column of the observer gain matrix, and a coefficient q included in the 0th-order term in the denominator is a coefficient included in the second row and first column of the observer gain matrix.

That is, if the value of q is increased in the conventional induction motor control method, the gain of G ₁ (s) and the gain close to the DC can be increased, and as a result, the convergence performance of the speed error can be improved. In the case of 0, G ₁ (s) has a denominator of the fourth order and a numerator of the third order, and therefore there may be a frequency band in which the phase difference between the input and output of G ₁ (s) exceeds 90 °. Sometimes the stability of the control system is not guaranteed.

FIG. 4 is a block diagram of a speed estimation system using the induction motor control method of the present invention. That is, a compensator for a current estimation error of the induction motor is newly provided, and the phase difference is 90 for a frequency band in which the phase difference between the input and output of G ₁ (s) exceeds 90 ° in the conventional control method. Do not exceed °.

  When the compensator shown in FIG. 4 is used, it is possible to compensate for the phase lag caused by the effect of the observer gain in the adaptive secondary magnetic flux observer, so that the adjustment range of the observer gain can be expanded while keeping the control system stable. The estimation performance can be improved. Further, since the speed estimation performance in the frequency band with the increased gain can be improved by the gain compensation of the compensator, it is possible to have a desirable transfer characteristic as a speed estimation system.

  FIG. 1 is a circuit configuration diagram of an induction motor speed control apparatus for performing the induction motor control method of the present invention. In this figure, components having the same functions as those of the conventional configuration shown in FIG. A description thereof will be omitted here.

  That is, the control unit 30 shown in FIG. 1 has a phase / gain compensator 31 added to the control unit 10 shown in FIG.

  The phase / gain compensator 31 corresponds to the compensator shown in FIG. 4 and is a delay-advance filter represented by a transfer function as shown in the following equation (6).

Here, ω ₀₂ > ω ₀₁ , k> 1.

When ω ₀₁ in the above equation (6) is set lower than the resonance frequency determined by R _r / L _r and ω _{se #} , and phase lead compensation and gain compensation are performed in the vicinity of this resonance frequency, as shown in FIG. Bode plot characteristics can be obtained.

That is, in FIG. 2, a characteristic line A indicated by a solid line is a characteristic of a speed estimation system using the phase / gain compensator 31, and a characteristic line B indicated by a light solid line is a characteristic of a conventional speed estimation system , indicated by a broken line. A characteristic line C indicates the characteristic of the phase / gain compensator 31. As is apparent from this characteristic diagram, as a result of setting q high in the conventional control method, a phase delay of 90 ° or more occurs. However, in the control method of the present invention, the phase delay is 90 ° or less and the angular frequency is Since the gain in the vicinity of 100 [rad / s] is increased, the error convergence time is further shortened.

The circuit block diagram of the speed control apparatus of the induction motor which shows the Example of this invention Bode diagram explaining the operation of the speed estimation system of the present invention Block diagram of equivalent feedback system for error of speed sensorless control system Block diagram of speed estimation system explaining operation of the present invention Circuit configuration diagram of a speed control device for an induction motor showing a conventional example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Power converter device, 2 ... Current detector, 3 ... Voltage detector, 10 ... Control part, 11 ... Speed adjusting means, 12 ... Coordinate converting means, 13 ... Torque current adjusting means, 14 ... Excitation current adjusting means, 15 ... slip frequency control means, 16 ... coordinate reverse conversion means, 21 ... current / magnetic flux observer, 22 ... observer gain setter, 23 ... rotational speed / resistance estimator, 30 ... control section, 31 ... phase / gain compensator, 100 ... induction motor.

Claims (1)

In a control method of an induction motor that drives the motor at a variable speed by speed sensorless vector control of the induction motor using an adaptive secondary magnetic flux observer,
An estimated value of the rotational speed of the electric motor is derived based on a value obtained by proportional-integral calculation of the phase and gain compensated for the phase and gain of the lead / lag characteristic with respect to the deviation between the estimated value of the torque current of the induction motor and its actual value. A method for controlling an induction motor.

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