JPS5899285A - Method for controlling converter for driving induction motor - Google Patents

Abstract

PURPOSE:To compensate for variation in secondary resistance of the motor, by controlling the output frequency of an inverter which is controlled in proportion to the sum of a slip frequency command signal and a detected speed signal in correspondence with the variation in magnetic flux of the motor and the polarity of the slip frequency command signal. CONSTITUTION:The PWM inverter 1 is controlled in association with the operation of a comparator 13, and an induction motor 2 is driven. A magnetic flux detector 16 integrates the primary voltage of the motor 2 and detects the signal proportional to the magnitude of the magnetic flux. An amplifier 17 outputs a signal corresponding to the deviation between a command signal of the amount of the magnetic flux and the detected signal. The signal is added to an adder 6 through a polarity inverter 19. Meanwhile, a signal corresponding to the polarity of the output signal from the amplifier 5 is taken out of a comparator 18, and the polarity of the slip frequency command signal is judged. The inverter 19 inverts the polarity in correspondence with the signal from the comparator 18. A frequency proportional to a frequency command signal is generated by an oscillator 7. The output of an exciting current command circuit 8 and the output of the amplifier 5 are multiplied 10 and 9 and added 11. Thus the variation due to the temperature of the secondary resistance of the motor is corrected and controlled.

Description

Detailed Description of the Invention The present invention v4 relates to a method of controlling an induction motor using an inverter device, and more particularly, a control method for compensating for characteristic changes that occur when the secondary resistance of the motor fluctuates due to temperature. Regarding.

A so-called vector control method is known in which the primary current of an induction motor is divided into an excitation component and a torque component, and each component is controlled independently to perform speed control with a rapid response. In this method, a current command pattern signal is calculated and synthesized based on the commands of each current component. The primary current of the J machine is controlled, but whether each component inside the motor is controlled directly according to the command depends on the control of the slip frequency (inverter output frequency). In other words, the -order current is considered to be decomposed into one minute of excitation and one minute of torque as a periphery frequency tS, and if the frequency is not appropriate, each component can be decomposed and controlled directly according to the command. I can't. What causes the slip frequency to become inappropriate?

The effect of temperature change on the secondary resistance of the electric IIh machine can be seen.

An object of the present invention is to provide a control method that can appropriately and honestly control the slip frequency even when changes in secondary resistance due to temperature are considered.

A feature of the present invention is that the output frequency of I/NO (-), which is controlled in proportion to the sum of the slip frequency command signal and the speed detection signal, is controlled in proportion to the fluctuation of the motor magnetic flux (Rorui or electric voltage) and the slip frequency command. depending on the polarity of the signal.

The problem lies in the fact that it is controlled by correction.

FIG. 1 shows a circuit configuration diagram of a PWM inverter device which is one embodiment of the present invention. In the figure, 1 is GTO (Qat@T
2 is a rust conduction motor, 3 is an operation command circuit that outputs command signals for the rotational speed and magnetic flux of the motor, and 4 is a speed detector.

5 is a speed l difference amplifier that amplifies the gap between the speed command signal and the speed detection signal, and 6 is a speed difference amplifier that adds the speed detection signal, the slip frequency command signal from the amplifier 5, and the output signal of the polarity inverter to be described later. 7 is an oscillator that outputs a two-phase sine wave signal with a frequency proportional to the output signal of adder 6; 8 is an excitation current command circuit that commands the excitation IA current of the motor 2; 9 is an amplification circuit 4;
The torque command No. 11I from 5 and one of the signals of excavation a7 are used as a signal, and the torque command of the next current is applied to the turf (5
The multiplier Jl generator 10 outputs the signal (sine wave signal), and the excitation Iadt signal is fully multiplied by the other jf1 signal of the oscillator 7, -
Multiplier that outputs the next (excitation component command pattern signal (sine wave signal) t-, 11 is a lA calculator that performs vector addition of each component command pattern + 1! and outputs a command pattern signal of the inverter output current, 12ri inverter output The IT current detector 13 which detects the storm x compares the current command butter/signal and the current detection signal,
- A comparator that outputs a PWM signal for on/off control; 14 is a gate circuit that provides a gate signal to the GTO; In addition.

There are three sets of similar parts 11' to 14 in proportion to the number of inverter output phases, but the other two sets are omitted from illustration.

15 is a transformer for detecting the inverter output voltage;
6 is a magnetic lid detector for integrating the 1-pressure detection signal and detecting the magnitude of the magnetic flux of the tvJ machine; 17 is a magnetic difference amplification device for amplifying the difference between the magnetic flux command signal and the detection signal. , 18 is a comparator that outputs a 21 direct signal according to the output 1g of the amplifier 5, and 17 is a polarity for switching the output signal polarity of the amplifier 417 according to the output 111 of the amplifier 418. It is inverted.

Next, the operation of the above circuit will be explained. First, the operation of the conventional circuit will be explained. Innoku Ichiyo 1's output m accent is the ratio f
! According to -1 of the circuit 13, it is controlled to be proportional to the XtIt command (turn signal). This current command signal is created as follows. The speed-black signal is added in addition-' 6, and a frequency command signal that commands the primary frequency of the motor is taken out.This signal and the signal from the 111 swivel 5- are combined into the slip frequency 1-command according to the relationship of the following equation. This will be the 1g issue.

f, = f, +f, ...
...(1) Here, f,: Slip frequency (proportional to the output signal of the amplification a5) f,:'#L mechanical rotation frequency (proportional to the speed detection signal) The oscillator 7 is proportional to the frequency command signal. Outputs a two-phase sine wave signal of the frequency. These are the current command butter 741
This is the phase reference for 1'@.

The multiplier 49.10 and the adder 11 perform all of the above-mentioned calculations and output a t-flow command pattern signal that commands two shifts of the inverter output current at one time. The result is that the inverter output *g is controlled in proportion to this 1g.

-The magnitude of the secondary current is controlled in such a way that it is proportional to the vector sum of the excitation component and the torque component. However, whether or not the primary current is correctly decomposed into each component within the motor is related to the slip frequency W, as shown in the linear equation.

Here, ■, : Torque ■,: Excitation amount 1: Constant of proportionality W: Slip angle frequency rl: Secondary resistance That is, the decomposition into each component is determined by W.

If W is not appropriate, it is not possible to calculate each component individually in a predetermined direction even if the magnitude of the negative current is controlled in a predetermined direction. At this time, the motor magnetic flux (voltage) varies from the reference value, causing an increase in motor voltage or a decrease in torque.

The reason why such a problem occurs is as described above and shown in Figure 15.
19 are circuits for solving this problem and are related to the present invention.

Before explaining the operation of the circuit, the principle will be briefly explained. When the resistance changes from the reference source, the second order of can-kaniso is 1. According to the relationship of equation (2). /1. changes from being honest. As a result, due to the fluctuation of ■, electric Ca flux (or electric
As sleep pressure) varies from the reference source, this change a′ik′I
Detect from the difference between the detection signal of one bundle of IL motors and its command signal, and correct the inverter output frequency according to the Cat of 7.
tt111I41, thereby preventing the above-mentioned problems.

Next, the operation of the circuit will be explained. 111, the bundle detector 16 integrates the motor voltage and detects a signal proportional to the size of the t11 bundle. Next, the amplifier 17 outputs an error signal for the difference of 1 between the magnetic flux command number 1M and the detection signal, and the signal is added to the adder 6 via the polarity inverter 19=.

On the other hand, a signal corresponding to the polarity of the output signal of the amplifier 65 is extracted from the ratio 11Ra1s, and this is a signal for determining the polarity of the slip frequency command signal, that is, the electric IIIJ low or regenerative operation.

Polarity Deactivation 619Fi Inverts the output signal polarity of the amplifier 17 in response to this signal, which is for the primary frequency t 1t11111 as follows. First, during the 111E dynamic operation, when the magnetic flux cover decreases, the primary frequency is controlled to decrease. As a result, the slip frequency is controlled to be small, and the i-bundle lid is increased to be properly corrected. At this time, the secondary resistance rt (according to the variation of D, the slip frequency W, changes tllJ11i4.
The wave number is controlled in an upward direction, and the magnetic flux t is also corrected appropriately.

On the other hand, during regenerative operation, when the amount of magnetic flux is low F, the primary frequency is controlled to increase in accordance with the pseudo inversion a19, contrary to the above. As a result, does the slip frequency become smaller? ff1J is controlled, the magnetic flux 11 increases and is corrected properly. At this time, W is corrected and controlled in accordance with the fluctuation of rl, as described above.

According to the present invention, it is possible to compensate for the influence of changes in motor secondary resistance, and it is possible to prevent increases in motor voltage and decreases in torque.

In the above implementation, the electric FA magnetic flux was detected by the magnetic flux amount detector 16, and the slip frequency was corrected and controlled according to the variation of the LA flux, but instead of @Higashijo detection, tEEt
Even if something is not detected, similar control can be performed. In this case, the eye wI is 1 in Figure 1.
Although the functions of the 6 to 190 parts are slightly different, the configurations are the same. Regarding the difference, in the circuit corresponding to 16, the magnitude t of the electric voltage is detected. 1 of the voltage command signal and detection signal from the operation command circuit 3 in an amplifier equivalent to 17.
A difference is detected. - Motivation magnetic flux and voltage have a ratio - relationship, so this is true! The same control as in the above-mentioned embodiment can be performed in the M mode, and the same effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conversion device for driving a WJ machine, which is one embodiment of the present invention.

Claims (1)

[Claims] 1. An induction motor and a converter ξ that supplies variable frequency alternating current to the induction motor, and an output voltage of the f converter based on signals that respectively command the excitation and torque components of the primary current of the rust conduction motor. 0 magnitude, and a control device that controls the output frequency of the converter according to the sum of the speed detection signal and the slip frequency command signal of the induction motor. a first means for ejecting a signal according to a change am to and adds the speed detection signal and the slip frequency command signal; a second means for determining the signal polarity of the slip frequency command signal;
A method of controlling a conversion device for driving an induction electric #1 machine, wherein the direction of change of the output signal of the first means is switched in accordance with the output signal of the second means, and the first step is standby.