JPH01227681A - Variable speed controller for induction motor - Google Patents

Abstract

PURPOSE:To realize the high response and accurate torque control of an induction motor by setting a torgue current target value in which the iron loss of the motor is estimated. CONSTITUTION:A speed regulator 5 outputs a torque current target value i''T in response to a deviation between a speed set value omega' 2 and an actual speed value omega2. An adder 7 adds the value i''T to an iron loss current set value io tO obtain a torque current target value i'T. Current regulators 13, 14 calculate 2-axis voltage target values V'M, V'T on the basis of a magnetization current target value i'M, a magnetization current iM, a torque current target value i'M and a torque current iT. A coordinates converter 15 converts the values V'M, V'T into 2-axis voltage target value V'alpha, V'beta on the basis of the phase angle phiof a magnetic flux vector obtained by integrating the angular speed omegaS of a magnetic flux vector and the actual speed value omega2 of a motor, and supplies it to a firing pulse generator 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly accurate variable speed control device for an induction motor using vector control as a basic technology.

[Conventional technology]

FIG. 6 is a block diagram showing a conventional example of a variable speed control device for an induction motor using such vector control.

In the figure, 1 is an inverter that converts a DC power source PN into a three-phase power source, 2 is an induction motor to be controlled, and 6 is a speed detector, for example, a pulse oscillator is used. The control device includes a speed setter 4, a speed regulator 5, a magnetizing current setter 8, a speed calculator 9, an integrator 10, a 3-phase/2-phase converter 11, a coordinate rotator (VD) 12, 15, and a current regulators 13, 14,
It consists of an ignition pulse generator 16.

The deviation between the constant force ω2 and the actual speed value ω2 determined from the output of the speed detector 6 is amplified, and the output is the target f of the torque current.
[It becomes iT. 8, as already mentioned, from below (
This is a speed calculator that calculates the angle of the magnetic flux vector of the motor and the speed ω8 according to equation 1).

The angular velocity ω8 of the magnetic flux vector corresponds to the overall frequency of the induction motor in a steady state.

, where K is the proportionality constant r2' is the secondary resistance of the induction motor t□ is the excitation inductance of the induction motor p is the differential operator T2- (t2' + 1m) / r 2 't2'
The angular velocity ω8 of the secondary leakage inductance magnetic flux vector of the induction motor and the actual speed value ω of the motor are added by an integrator 10 and then integrated to obtain the phase angle ψ of the magnetic flux vector with respect to the rotor. 11 is 3 which converts the motor current into orthogonal two-phase current -21β as already mentioned.
In the phase/two-phase converter, by rotating the coordinate axis by ψ with the coordinate rotator 12, the value is converted into magnetization current - and torque current IT.
get. Magnetizing current 1. The torque current IT is input to current regulators 13 and 14, respectively, which amplify the deviations between iM'* and 1M, and between IT* and iT, respectively. Each output is the motor's two-axis voltage target value VM and v
VM*YT is converted into a two-phase voltage target value v*#vβ9 by the coordinate converter 15. The switching of five inverters is performed in the ignition pulse generator 16 for Vα, Vβ, and the like.

Note that when the main control target is torque, the speed setter 4 and the speed regulator 5 are not necessary, and the speed setting device 4 and the speed adjuster 5 are
Just give T.

The above is an overview of vector control, which is known as a high-performance torque control technology for AC motors.

[Problem that the invention aims to solve]

As already mentioned, vector control treats the magnetic flux, current, etc. of an AC motor as a vector quantity, and uses a current component (magnetizing current) that is parallel to the magnetic flux vector and contributes to magnetic flux generation.
By independently controlling the current component (torque current) that is perpendicular to the same vector and contributes to torque generation, high-performance torque control of the AC motor is possible. However, in conventional vector control, no mention is made of the iron loss of the AC motor, and the iron loss is ignored on the assumption that it is minute.

The effect of ignoring iron loss is to reduce the desired torque and cause an error in the actually generated torque. In particular, good torque control accuracy is required for applications that perform iL control, but it is difficult to say that torque caused by iron loss (control error can reach several percent) and iron standard can be ignored. .

An object of the present invention is to take the iron loss of the induction motor into consideration and set a torque current target value that takes into account the iron loss in advance.
An object of the present invention is to provide a variable speed control device for an induction motor that achieves high response and highly accurate torque control of the induction motor.

[Means to solve the problem]

To achieve the above object, in the present invention, in a variable remote control device for an induction motor using vector control, the sum of a predetermined constant determined by motor characteristics as an iron loss current and a torque current value corresponding to a desired torque is set. The torque current target value setting means is provided.

[Effect]

Considering the iron loss of an induction motor, the current component orthogonal to the magnetic flux vector is classified into a torque current that contributes to the original torque generation, a heat loss, and C) an iron loss current that does not contribute to torque generation. To clarify the concept of torque current,
Hereinafter, the conventional torque current will be referred to as the first torque current, and the torque current that contributes to the original torque generation according to the present invention will be referred to as the second torque current.

First torque current - second torque current + iron loss current 1.
(2) In the present invention, according to the single series, the second torque electric power is controlled depending on the desired torque, and the iron loss current is supplied at a predetermined IQ determined by the motor characteristics,
Realizes highly accurate torque control. When the secondary magnetic flux of the induction energizer is constant, the frequency at which the torque is stopped is proportional, so the frequency at which the torque is stopped is the second frequency corresponding to the desired torque.
is proportional to the torque current of , and is controlled accordingly.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention. Comparing FIG. 1 with FIG. 6 showing the prior art, it can be seen that the only difference is that an iron loss current setting device 6 and an adder 7 are added as shown in the figure, and other things are the same.

In FIG. 1, the speed regulator 5 calculates the actual speed value ω2 determined from the speed setting value *ω2 and the output of the speed detector 3.
The output becomes the target value iT1* of the second torque current corresponding to the desired torque.

6 is an iron loss current setting device that increases the iron loss current value determined by the motor characteristics by 4, and its setting value I. and IT are input to an adder *7 to obtain the first torque current target 1lfiT. Since the subsequent circuit operation is exactly the same as that already described with reference to FIG. 6, there is no need to repeat it here.

Next, a specific example of the iron loss current setting device will be explained.

Generally, iron loss occurs due to a change in magnetic flux 1, and its value depends on dF/dt. Now - phase magnetic flux ' 5ill
6′ 1 i, and dF/dt are expressed by the following equation (3).

dF/dt=ωWωSω1t ・・・・・・
(3) That is, when the rotation of the magnetic flux is bidirectional (when ω1 is bipolar), the polarity of the iron loss current changes depending on the rotation direction. FIG. 2 is a block diagram showing a configuration example of an iron loss current setting device when ω1 is bipolar.

In FIG. 2, 6 is an iron loss current setting device, 6A is a comparator for determining the polarity of ω1, 6B is an inverter for reversing the polarity,
6C is a switch that turns on/off according to the output of the comparator 6A. In other words, ω.

〉0, iron loss current i. is ω1 immediately after the setting of the setting device 6.
〈If 0, then i. has the opposite polarity of the setting value of the setting device 6.

FIG. 3 is a block diagram showing another example of the configuration of the iron loss current setting device. In FIG. 3, ω1 is input to a function generator 6D in which a function of iron loss current to ω1 is stored. The magnitude V of the magnetic flux is input to a function generator 6E in which a function for V of iron loss current is stored. The output of each function generator is multiplied by a multiplier 6F to produce a magnetizing current i. get.

FIG. 4 is a graph showing an example of functions stored in the function generator 6D. FIG. 5 is a graph showing an example of functions stored in the function generator 6E. Note that 1 is determined by the following formula.

〔Effect of the invention〕

According to the present invention, in a variable speed control device for an induction motor using vector control, since each stock control mu is determined taking into account the iron loss of the induction motor, there is an advantage that the WI degree (torque control) is improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a variable speed control device for an induction motor as an embodiment of the present invention, and FIGS. 2 and 6 each show a configuration example of an iron loss current setting device used in the embodiment of the present invention. Block diagram, FIG. 4 is a graph showing a function example of the function generator 6D in FIG. 3, FIG. 5 is a graph showing a function example of the function generator 6E in FIG. 3, and FIG. 6 is a vector control of an induction motor. 1 is a block diagram illustrating a conventional example of a variable control device according to. Explanation of symbols = 9- 1...Inverter, 2...Induction motor, 3...Speed detector, 4...Speed setter, 5... ... Speed regulator, 6 ... Iron loss current setting device, 7 ... Adder, 13゜14 ...
...Current regulator, 12.15...Coordinate rotator,
16...Ignition pulse generator representative Patent attorney Akio Namiki Patent attorney Kiyoshi Matsuzaki 1n-

Claims (1)

[Claims] 1) The primary current of an induction motor supplied via a power converter that can control the magnitude, frequency and phase of the output voltage is a component parallel to the magnetic flux of the motor (magnetizing current). In a variable speed control device for an induction motor, which separates a component (torque current) orthogonal to the torque current into a component (torque current) and adjusts each independently to control at least the motor torque, a torque current target value is set for adjusting the torque current. Taking into account the iron loss current that becomes heat loss and does not contribute to torque generation, a predetermined value determined by the motor characteristics as the iron loss current, and a torque current value corresponding to the desired torque,
1. A variable speed control device for an induction motor, comprising a torque current target value setting means for setting the sum of .