JPH1141996A - Induction motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a system by operating the inner product of a secondary current vector and a secondary flux vector, estimating the secondary resistance from the inner product according to a speed estimation system 1 or 2 and operating a rotational speed thereby eliminating the control error of speed or torque due to temperature fluctuation. SOLUTION: An inner product operating means 11 operates the inner product of the secondary current vector i2 delivered from a secondary current operating unit 8 and a secondary magnetic flux vector ϕ2 delivered from a secondary flux operating unit 7 and a hysteresis comparator 12 makes a decision whether the inner product goes zero or not. If the output is zero from the decision results, a speed estimation system (1) 13 estimated the rotational speed of a motor otherwise the speed estimation system (1) 13 and a speed estimation system (2) 15 estimate the secondary resistance R2. Subsequently, the rotational speed of the motor is operated based on the new secondary resistance R2 estimated by the speed estimation system (1) 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction motor driven by a voltage-type inverter, and more particularly to an induction motor control device for suppressing a characteristic change due to a change in a parameter of the motor.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional control block of an induction motor control device for controlling the torque and speed of an induction motor with high accuracy and high speed without attaching a speed detector of the induction motor. Technology will be described. In FIG. 2, 1 is a motor, 2 is an inverter, and 3 and 4 are voltage and current detectors. Reference numeral 5 denotes a coordinate converter from the three-phase stator coordinate system (u, v, w) to the two-phase stator coordinate system (α, β).
Reference numeral 6 denotes a primary magnetic flux vector calculator, 7 denotes a secondary magnetic flux vector calculator, 8 denotes a torque calculator, 9 denotes a rotation speed calculator of an induction motor, and 10 denotes a speed PI controller. Reference numeral 11 denotes a binary hysteresis comparator for judging a deviation of the primary magnetic flux from a target value, and reference numeral 12 denotes a ternary hysteresis comparator for judging a deviation of the torque from the target value. Reference numeral 13 determines a vector area where a magnetic flux vector exists. Reference numeral 14 denotes a switching table determined by the outputs of 11, 12, and 13.

A deviation from the magnetic flux and torque calculated inside the control circuit with respect to a magnetic flux command | φ * 1 | and a torque command T * given from the outside is added to a hysteresis comparator, and the deviation is set within a predetermined hysteresis deviation. Instantaneous control of the output voltage of the inverter is performed to maintain the voltage, and a conduction signal is generated.

The primary magnetic flux φ1 of the induction motor is calculated from the primary voltage V1 and current i1 of the induction motor output from the coordinate converter 5 according to equation (1). Here, R1 is the primary resistance of the induction motor.

[0005]

(Equation 1)

The primary magnetic flux φ output from the primary magnetic flux calculator 6
From the primary current i1 output from the coordinate converters 1 and 5, the secondary magnetic flux φ2 of the induction motor is calculated by equation (2). Here, L1 and L2 are self-inductances on the primary and secondary sides of the induction motor, and M is a mutual inductance between the primary winding and the secondary winding.

[0007]

(Equation 2)

The primary magnetic flux φ output from the primary magnetic flux calculator 6
1 and the primary current i1 of the output of the coordinate converter 5, the torque T of the induction motor is calculated by equation (3).

[0009]

(Equation 3)

The secondary magnetic flux φ of the output of the secondary magnetic flux calculator 7
2 and the torque T of the induction motor output from the torque calculator 8, the rotation speed ωm of the induction motor is calculated by the equation (4). Here, φ2α and φ2β are the α-axis component and the β-axis component after the two-phase coordinate conversion.

[0011]

(Equation 4)

Output ωm of rotational speed calculator 9 of the induction motor
The torque controller 10 generates a torque command from the speed controller 10 by calculating a deviation from the speed command value. In addition, the primary magnetic flux command φ * 1
And the calculated value φ1 of the primary magnetic flux output from the primary magnetic flux calculator 6
, The deviation between the torque command T * of the output of the speed controller 10 and the calculated value T of the torque of the output of the torque calculator 8, and the calculated value φ1 of the primary magnetic flux 6 of the output are 11, 1
Input to 2 and 13. Switching table 14 is 1
The inverters are controlled by determining the primary voltage vector based on the outputs of 1, 12, and 13. As described above, the respective blocks for the magnetic flux and the speed estimation calculation are added to the basic torque control system block to constitute a speed sensorless speed control system.

[0013]

However, in the above-mentioned prior art, the secondary resistor R2 is used for calculating the speed of the induction motor. This R2 fluctuates according to the temperature of the motor, and R2 fluctuates due to the temperature fluctuation, thereby causing an error in speed calculation. The present invention has been made in view of the above points, and an object of the present invention is to provide an induction motor control device that solves these drawbacks.

[0014]

That is, means for achieving the object is the speed estimation method 1 described above (operation (4)).
Equation 2) and the following speed estimation method 2 independent of R2 are used. Since the speed estimation method 2 does not include R2, it has robustness against fluctuations in R2. However, there are conditions for using the speed estimation method 2. That is, when the denominator of the speed calculation formula for the speed estimation method 2 does not become zero, the speed estimation method 2 can be used. The method of the present invention
Inner product calculating means for calculating an inner product of the secondary current vector i2 of the output of the calculator of the secondary current and the secondary magnetic flux vector φ2 of the output of the calculator of the secondary magnetic flux, and an output of the inner product calculating means. Means for determining whether the result is zero, and from the result of this determination, if the output of the above inner product calculating means is zero,
The rotational speed of the motor is estimated by the speed estimation method 1. If the output of the inner product calculation means is not zero, the speed estimation method 1 and the speed estimation method 2 are used to estimate R2, and then the speed estimation method 1 and a new estimation are performed. A means for calculating the rotation speed of the electric motor based on the calculated R2.

Hereinafter, the reason why the means for solving the above problem can solve the above problem will be described. From the basic formula of the voltage and current of the motor in the stator coordinates, the voltage on the secondary side appears as follows.

[0016]

(Equation 5)

The current on the secondary side appears as follows.

[0018]

(Equation 6)

The reactive power Q input to the secondary side is given by the following equation.

[0020]

(Equation 7)

From this equation, the estimated value of the rotational speed of the induction motor is calculated by equation (8).

[0022]

(Equation 8)

If the rotational speed of the induction motor is estimated using equation (8), the estimated rotational speed of the induction motor does not depend on R2. At this time, since the speeds calculated by the equations (4) and (8) are the same value, the secondary-side resistance R2 is calculated from the two equations by the equation (9).

[0024]

(Equation 9)

In equation (8), there is a case where the denominator becomes zero. Judging this, when the denominator of the equation (8) does not become zero, a new R2 is calculated by the equation (9), and the rotation speed of the motor is calculated by this and the equation (4). (8)
When the denominator of the equation becomes zero, it is considered that R2 does not change abruptly. Therefore, the rotation speed of the motor is calculated using the equation (4) and the previously estimated R2. Thus, the above problem can be solved. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0026]

FIG. 1 shows an embodiment of the present invention.
Description of the same parts as in FIG. 2 of the prior art is omitted. In FIG. 1, reference numeral 8 denotes a secondary current calculator, which calculates the current from the output of the coordinate converter 5 and the primary magnetic flux output from the primary magnetic flux calculator 6 according to equation (8).

Numeral 11 denotes a secondary magnetic flux vector of the output of 7 and 8
Calculates the inner product of these two quantities and the rotational speed of the induction motor from the secondary current of the output, and further determines whether the inner product becomes zero. 14 calculates R2 according to equation (9). Reference numeral 13 calculates the rotational speed of the induction motor according to equation (8). Numeral 15 calculates the rotational speed of the induction motor using equation (4). If the inner product is not zero (condition is satisfied), the rotational speed of the induction motor is calculated through 13 (if the condition is not satisfied). If the inner product is zero (condition is not satisfied), the secondary resistance is determined through 14. R2 is calculated, and using this, the rotational speed of the induction motor is calculated by 15.

Numeral 19 generates an excitation current command from a secondary-side magnetic flux command. Reference numeral 18 generates a torque current command from the secondary-side magnetic flux command and the torque command. Reference numeral 17 denotes a slip frequency calculator. Reference numeral 16 denotes a rotation angle calculator of a rotation coordinate system.
Reference numeral 20 denotes a coordinate converter 2 for converting a two-phase coordinate system to a rotating coordinate system. Reference numeral 21 denotes a voltage command calculator. The converted current values are compared with the excitation current at 19 outputs and the torque current at 18 outputs, respectively, and a voltage command is generated from the deviation through PI calculation. The inverter is controlled using this voltage command. Since 16 to 21 are well-known functional blocks, detailed description thereof will be omitted.

[0029]

As described above, according to the present invention, even if the actual resistance R2 on the secondary side fluctuates due to the temperature fluctuation of the motor, the actual R2 is calculated, and induction is performed using the calculated R2. Calculate the rotation speed of the motor. Therefore, even if R2 fluctuates due to temperature fluctuation, no speed or torque control error occurs, and the stability of the system is ensured.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of the present invention.

FIG. 2 is a functional block diagram of a conventional technique.

[Explanation of symbols]

 Reference Signs List 1 motor 2 inverter 3 voltage detector 4 current detector 5 coordinate converter 6 primary magnetic flux vector calculator 7 secondary magnetic flux vector calculator 8 torque calculator 9 rotation speed calculator 10 speed PI controller 11 hysteresis comparator 12 hysteresis Comparator 13 Vector area judgment 14 Switching table 15 Rotation speed calculator 16 Rotation angle calculator 17 Slip frequency calculator 18 Torque current commander 19 Excitation current commander 20 Coordinate converter 21 Voltage command calculator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichiro Miyashita 338-1, Ogino, Kamisakuyanagi, Yamato-shi, Kanagawa Prefecture Toyo Electric Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. An induction motor driven by an AC power supply, a voltage detection means for detecting a supply voltage to the induction motor, a current detection means for detecting an input current of the induction motor, and a voltage of an output of the voltage detection means. A voltage-system primary magnetic flux vector calculating means for calculating a primary magnetic flux vector based on the vector and the current vector of the output of the current detecting means; A secondary magnetic flux vector calculating means for calculating a secondary magnetic flux vector of the induction motor from the magnetic flux vector; and a primary magnetic flux vector output from the primary magnetic flux vector calculating means and a primary magnetic flux vector output from the primary magnetic flux vector calculating means. A secondary current vector calculating means for calculating a secondary current vector; and a current vector output from the current detecting means. A torque calculating means for calculating a generated torque of the motor from the primary magnetic flux vector output from the primary magnetic flux vector calculating means; a secondary magnetic flux vector output from the secondary magnetic flux vector calculating means; and a torque output from the torque calculating means. And an induction motor control device comprising a speed calculation means 1 for calculating a rotation speed of the induction motor from a secondary resistance R2 of the induction motor. Speed calculation means 2 for calculating the rotation speed of the motor from the secondary current vector output from the current vector calculation means, independent of the secondary resistance R2 of the motor, and rotation speed of the motor dependent on the secondary resistance R2 of the motor A parameter for estimating the motor secondary resistance R2 from the arithmetic means 1 and the motor rotational speed calculating means 2 independent of the motor secondary resistance R2; Induction motor control apparatus characterized by being composed of a data estimator. 2. The output of the secondary resistance estimating means of the motor,
2. The induction motor control device according to claim 1, wherein the rotation speed of the motor is calculated using the secondary resistor R2 and the rotation speed calculation means 1 of the motor.