JP2011004492A - Controller of induction motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deriving means for the electrical constant of an induction motor, suitable for controlling the variable speed of the induction motor.SOLUTION: An controller 20 is comprised of a command value computing means 21, an integrating means 12, coordinate transformation means 13, 14, and a constant computing means 22. At the constant computing means 22, the rated output value P[W], rated voltage value V[V], and rated current value I[A] of an induction motor 2 are input, and a rated magnetizing current computation value Ias an electrical constant of the induction motor 2 is derived using a publicly known mathematical expression. For this reason, it is unnecessary in this derivation to rotate the induction motor 2, apply special voltage to the induction motor 2, or provide an accurate and expensive measuring circuit. In this controller 20, therefore, the variable speed of the induction motor 2 is controlled through a power converter 1 using a publicly known technology based on the rated magnetizing current computation value Ias an electrical constant of the induction motor 2 obtained by the constant computing means 22 or the other electrical constant.

Description

  The present invention relates to an induction motor control device that performs variable speed control of an induction motor through a power conversion device that outputs a voltage having an arbitrary frequency and amplitude, and more particularly, to an electric motor used for variable speed control of the induction motor. The present invention relates to a constant calculation means for deriving a constant.

  FIG. 3 is a circuit configuration diagram showing a conventional example of this type of induction motor control device.

In FIG. 3, reference numeral 1 denotes an input three-phase voltage command v _U ^* , v _V ^* , v _W ^* (amount of alternating current), which is converted into an on / off signal to each built-in semiconductor switch by PWM calculation. This is a power conversion device that outputs a three-phase AC voltage based on these on / off signals. Reference numeral 2 denotes an induction motor fed from the power converter 1. Reference numeral 3 denotes a current detector that detects a current from the power converter 1 to the induction motor 2, that is, a primary current i ₁ of the induction motor 2. Reference numeral 10 denotes a control device that is formed of a command value calculation means 11, an integration means 12, coordinate conversion means 13 and 14, and a constant measurement means 15, and that performs variable speed control of the induction motor 2 via the power conversion device 1.

In the control device 10, a command value calculation means 11 the induction motor 2, is commanded primary angular frequency command value omega ₁ ^*, obtained the primary angular frequency command value omega ₁ ^* by time integration calculation by integrating means 12 In accordance with the phase angle command value θ ₁ ^* , i _1d and i _1q obtained by converting the primary current i ₁ of the induction motor 2 by the three-phase to two-phase conversion and the dq axis conversion by the coordinate conversion means 13, and the constant measurement means 15 The d-axis voltage command value v _1d ^* and q-axis voltage of the induction motor 2 are used based on the obtained exciting inductance calculation value L _m ^# as the electric constant of the induction motor 2 and other electric constants, using a known technique. The command value v _1q ^* is output. In the coordinate conversion means 14, the voltage command obtained by subjecting the d-axis voltage command value v _1d ^* and the q-axis voltage command value v _1q ^* to α-β conversion and two-phase to three-phase conversion based on the phase angle command value θ ₁ ^*. v _U ^* , v _V ^* , and v _W ^* are generated.

  As the constant measuring means 15, those disclosed in the following Patent Document 1 and Patent Document 2 are known.

JP 2003-244982 A JP 2006-158178 A

  In the constant calculator as the constant measuring means 15 described in Patent Document 1, an AC voltage having a predetermined voltage and frequency is applied to the induction motor and rotated in a no-load state, and the voltage and current at this time are calculated. Based on the measured value, the calculated value of the inductance of the induction motor is calculated. In this case, the induction motor is incorporated in a mechanical device and cannot be rotated in a no-load state. It was difficult.

  Further, in the constant calculator as the constant measuring means 15 described in Patent Document 2, a predetermined DC voltage is applied to the induction motor so as not to rotate, and the voltage and current at this time are measured. Based on the measured value, the excitation inductance calculation value of the induction motor is obtained. However, if the voltage applied when measuring the excitation inductance is low, the effect of setting errors of voltage error, current error, and other electrical constants (primary resistance, leakage inductance, secondary resistance, etc.) is large and can be obtained. Since the measured value includes measurement timing error, there is a problem that sufficient accuracy cannot be obtained due to the large error. To reduce the above error, a highly accurate and expensive measurement circuit is required. There was a problem of need.

  An object of the present invention is to provide a control device for an induction motor that can solve the above problems.

This first invention is a control device for an induction motor that performs variable speed control of an induction motor via a power conversion device that outputs a voltage of arbitrary frequency and amplitude.
The control device includes constant calculation means for performing calculation for deriving an electric constant of the induction motor based on a rated value of the induction motor.

According to a second aspect of the present invention, in the induction motor control device of the first aspect,
The constant calculation means inputs a rated output value, a rated voltage value, and a rated current value of the induction motor, and calculates a rated induced voltage calculation value of the induction motor by multiplying the rated voltage value by a predetermined coefficient. The rated output value is divided by the rated induced voltage calculated value to calculate the rated torque current calculated value of the induction motor, and the square value of the rated torque current calculated value is subtracted from the square value of the rated current value. A square root of the value obtained by the calculation and the subtraction operation is derived, and the derived square root is output as a calculated value of the rated magnetization current of the induction motor.

A third invention is a control device for an induction motor according to the first invention, wherein:
The constant calculation means inputs a rated output value, a rated voltage value, a rated current value, and a rated frequency of the induction motor, calculates a rated induced voltage of the induction motor by multiplying the rated voltage value by a predetermined coefficient. And calculating the rated torque current calculation value of the induction motor by dividing the rated output value by the rated induction voltage calculation value, and calculating the square of the rated torque current calculation value from the square value of the rated current value. The value is subtracted, the square root of the subtracted value is derived, the derived square root is set as the rated magnetizing current calculated value of the induction motor, and the rated induced voltage calculated value is calculated as the rated frequency and rated magnetizing current calculated value. The excitation inductance calculation value of the induction motor is derived by dividing the product by the product of, and the derived rated magnetization current calculation value and excitation inductance calculation value are output.

Furthermore, a fourth invention is the control apparatus for induction motors according to the first to third inventions,
The induction motor is subjected to variable speed control using the electric constant derived by the constant calculating means as a control constant of the control device.

  Since the present invention derives the electric constant of the induction motor based on the rated output value, the rated voltage value, etc. as the rated value of the induction motor, the voltage is applied to the induction motor for this derivation. There is no need to apply it, nor is a highly accurate measurement circuit required.

The circuit block diagram of the control apparatus of the induction motor which shows 1st Example of this invention The circuit block diagram of the control apparatus of the induction motor which shows 2nd Example of this invention Circuit diagram of induction motor control device showing conventional example

  In the embodiment of the present invention described below, components having the same functions as those of the conventional induction motor control device described in FIG. 3 are denoted by the same reference numerals, and the description thereof is omitted here.

  FIG. 1 is a circuit configuration diagram of an induction motor showing a first embodiment of the present invention.

  The control device 20 includes a command value calculation means 21, an integration means 12, coordinate conversion means 13 and 14, and a constant calculation means 22.

First, in the constant calculation means 22, the rated output value P _RATE [W], the rated voltage value V _RATE [V], and the rated current value I _RATE [A] of the induction motor 2 are input, and the following formula 1 Based on Equation 5, the rated magnetizing current calculation value I _MO ^# of the induction motor 2 is derived.
[Equation 1]
E ₂₀ = K × V _RATE
Here, E ₂₀ is the rated induced voltage value [V] of the induction motor 2, and K is a coefficient.

The rated induced voltage value E ₂₀ is a voltage induced in the excitation inductance of the induction motor 2 at the rated magnetic flux and the rated frequency, and is slightly smaller than the rated voltage value V _RATE. Is set in advance to a value of about 0.8 to 0.9.

Further, when the induction motor 2 is a three-phase induction motor, there is an equation 2 relationship among the rated output value P _RATE , the rated induced voltage value E _20, and the rated torque current value I _TO [A].
[Equation 2]
P _RATE = 3 × E ₂₀ × I _TO
Equation (3) is obtained by modifying Equation (2).
[Equation 3]
I _TO = P _RATE / (3 × E ₂₀ )
Since the rated current value I _RATE of the induction motor 2 is the current at the rated magnetic flux and the rated torque of the induction motor, there is a relationship expressed by Equation (4).
[Equation 4]
I _RATE = {(I _MO ^# ) ² + I _TO ² } ^1/2
Equation (5) is obtained by modifying Equation (4).
[Equation 5]
I _MO ^# = (I _RATE ² −I _TO ² ) ^1/2
That is, the constant calculation means 22 outputs the rated magnetization current calculation value I _MO ^# of the induction motor 2 obtained by the above formula 5.

  Thus, since the electric constant of the induction motor is derived based on the rated output value, rated voltage value, and rated current value as the rated values of the induction motor 2, the induction motor 2 is used for the derivation. There is no need to apply a special voltage, and there is no need for a highly accurate and expensive measuring circuit.

Further, in this control device 20, the primary angular frequency command value ω ₁ ^{* of the} induction motor 2 commanded by the command value calculation means 21 and the primary angular frequency command value ω ₁ ^* are time integrated by the integrating means 12. I _1d , i _1q obtained by three-phase-two-phase conversion and dq-axis conversion of the primary current i ₁ of the induction motor 2 by the coordinate conversion means 13 based on the phase angle command value θ ₁ ^* obtained in this way, and a constant calculation Based on the rated magnetization current calculation value I _MO ^# as an electric constant of the induction motor 2 obtained by the means 22 and other electric constants, the d-axis voltage command value v _1d ^{* of the} induction motor 2 is used while using a known technique ^. And the q-axis voltage command value v _1q ^* are output.

  FIG. 2 is a circuit configuration diagram of an induction motor showing a second embodiment of the present invention.

  The control device 30 includes a command value calculation means 31, an integration means 12, coordinate conversion means 13 and 14, and a constant calculation means 32.

In this constant calculation means 32, the rated output value P _RATE [W], the rated voltage value V _RATE [V], the rated current value I _RATE [A], and the rated frequency F [Hz] of the induction motor 2 are input. First, the rated magnetizing current calculation value I _MO ^# of the induction motor 2 is derived from the equations 1 to 5. Next, the excitation inductance calculation value L _m ^# of the induction motor 2 is derived based on the following equations 6 to 7.

That is, since the rated induced voltage value E ₂₀ of the induction motor 2 is a voltage when the rated magnetization current value flows through the exciting inductance, the following formula 6 is established.
[Equation 6]
E ₂₀ = ω _1RATE × L _m ^# × I _MO ^#
Here, ω _1RATE is a primary angular frequency corresponding to the rated frequency F of the induction motor 2, L _m ^# is an excitation inductance calculation value, and I _MO ^# is a rated magnetization current calculation value.

Equation (7) is obtained by transforming Equation (6).
[Equation 7]
L _m ^# = E ₂₀ / (ω _1RATE × I _MO ^# )
That is, the constant calculation means 32 outputs the rated magnetizing current calculation value I _MO ^{# of} the induction motor 2 obtained by the equation 5 and the excitation inductance calculation value L _m ^# obtained by the equation 7. Yes.

  Thus, since the electrical constant of the induction motor is derived based on the rated output value, rated voltage value, rated current value, and rated frequency as the rated value of the induction motor 2, for this derivation, There is no need to apply a special voltage to the induction motor 2, and a highly accurate and expensive measurement circuit is not required.

In the control device 30, the command value calculation means 21 calculates the primary angular frequency command value ω ₁ ^{* of the} induction motor 2 to be commanded and the primary angular frequency command value ω ₁ ^* by time integration calculation by the integration means 12. I _1d , i _1q obtained by three-phase-two-phase conversion and dq-axis conversion of the primary current i ₁ of the induction motor 2 by the coordinate conversion means 13 based on the phase angle command value θ ₁ ^* obtained in this way, and a constant calculation Based on the rated magnetization current calculation value I _MO ^# and the excitation inductance calculation value L _m ^# as the electric constants of the induction motor 2 obtained by the means 32 and other electric constants, the induction motor 2 is used while using a known technique. D-axis voltage command value v _1d ^* and q-axis voltage command value v _1q ^* are output.

  DESCRIPTION OF SYMBOLS 1 ... Electric power conversion apparatus, 2 ... Induction motor, 3 ... Current detector, 10 ... Control apparatus, 11 ... Command value calculating means, 12 ... Integration means, 13, 14 ... Coordinate conversion means, 15 ... Constant measurement means, 20 ... Control device, 21 ... command value calculating means, 22 ... constant calculating means, 30 ... control device, 31 ... command value calculating means, 32 ... constant calculating means.

Claims (6)

In a control device for an induction motor that performs variable speed control of an induction motor via a power conversion device that outputs a voltage of arbitrary frequency and amplitude,
The control apparatus for an induction motor according to claim 1, further comprising constant calculation means for performing calculation for deriving an electric constant of the induction motor based on a rated value of the induction motor. In the control apparatus of the induction motor according to claim 1,
The induction motor control apparatus according to claim 1, wherein the constant calculation means calculates a rated magnetizing current calculation value of the induction motor by using a rated output value, a rated voltage value, and a rated current value of the induction motor as inputs. In the control apparatus of the induction motor according to claim 2,
The constant calculation means inputs a rated output value, a rated voltage value, and a rated current value of the induction motor, and calculates a rated induced voltage calculation value of the induction motor by multiplying the rated voltage value by a predetermined coefficient. The rated output value is divided by the rated induced voltage calculated value to calculate the rated torque current calculated value of the induction motor, and the square value of the rated torque current calculated value is subtracted from the square value of the rated current value. Calculate the square root of the subtracted value,
The derived square root is output as a calculated value of the rated magnetization current of the induction motor. In the control apparatus of the induction motor according to claim 1,
The induction motor control apparatus according to claim 1, wherein the constant calculation means calculates an excitation inductance calculation value of the induction motor by using a rated output value, a rated voltage value, a rated current value, and a rated frequency of the induction motor as inputs. In the induction motor control device according to claim 4,
The constant calculation means inputs a rated output value, a rated voltage value, a rated current value, and a rated frequency of the induction motor, calculates a rated induced voltage of the induction motor by multiplying the rated voltage value by a predetermined coefficient. And calculating the rated torque current calculation value of the induction motor by dividing the rated output value by the rated induction voltage calculation value, and calculating the square of the rated torque current calculation value from the square value of the rated current value. The value is subtracted, the square root of the subtracted value is derived, the derived square root is set as the rated magnetizing current calculated value of the induction motor, and the rated induced voltage calculated value is calculated as the rated frequency and rated magnetizing current calculated value. To calculate the exciting inductance calculation value of the induction motor,
An induction motor control device that outputs the calculated rated magnetization current value and the calculated excitation inductance value. In the induction motor control device according to any one of claims 1 to 5,
An induction motor control device characterized in that the induction motor is subjected to variable speed control using the electric constant derived by the constant calculation means as a control constant of the control device.

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