JPS6295987A - Controller for ac motor - Google Patents

Abstract

PURPOSE:To make currents follows up to a current command precisely without depending upon the speed of operation, and to conduct the torque control of high response with high accuracy by mounting a current change-rate control system controlling the rate of change of AC currents besides a current control system controlling a biaxial component. CONSTITUTION:An output signal i* from a current-command arithmetic circuit 22 is inputted to a change-section arithmetic circuit 23, and a current-detecting signal (i) from a current detector 18 is inputted to a change-section detecting circuit 24. The change-section arithmetic circuit 23 arithmetically operates the change section i*g of the input signal i*. The change-section detecting circuit 24 arithmetically operates the change section ig of the input signal (i). A current change-section control circuit 25 works in response to a deviation between the signals i*g and ig, and outputs a control signal controlling a frequency converter 1.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides an AC 'ME' that performs high-precision and high-response torque control.
This invention relates to a motive control device.

[Background of the invention]

In order to increase the torque of AC motors with high precision and high response,
Induction even for synchronous motors! Vector control is also adopted for the motive. In order to perform torque control with high precision and high response according to the original theory using vector control, it is necessary to make the actual current follow the tt flow command with high precision1. As described in Japanese Patent Publication No. 57-52392, two current control systems are used: an alternating current control system that controls alternating current, and a current component control system that controls current components. A known method is to eliminate stationary offset using a current component control system and improve the current waveform using an alternating current control system so that the actual current follows the current command with high accuracy.

However, if this method is used to make the actual current follow the command accurately even in response to transient torque command changes, there is a problem that the followability becomes insufficient in the high speed region due to the delay in the AC current control system. There is. In particular, when processing is performed by software using a microprocessor or the like, this effect becomes significant due to the delay caused by the sampling time.

[Purpose of the invention]

The invention has been made to address the above-mentioned problems, and its purpose is to provide a control device for an AC motor that can accurately follow a current command even in a transient state.

[Summary of the invention]

The present invention is characterized by a current control system that controls the two-axis distribution of the alternating current input terminal of the alternating current motor, and by controlling the alternating current of the alternating current motor.

[Embodiments of the invention]

FIG. 1 shows an embodiment in which the present invention is applied to an induction motor.

In Fig. 1, the output of the frequency converter 1 is the induction motor @2
connected to. As the frequency converter 1, various types of converters can be used, such as a cycloconverter, a PWM inverter, and a current source inverter. The rotation angle of the induction motor 2 is detected by a rotary encoder 3 connected to its shaft. The rotational speed of the induction motor 2 is commanded by a speed command circuit 11' as a speed command signal ω-, the output of which is input to a speed m1l circuit 13. On the other hand, the output of the encoder 3 is input to the speed detection circuit 12. The speed detection circuit 12 detects the rotation speed ω of the induction motor 2 by counting the number of pulses input from the encoder 3 within a predetermined time.

The output of the speed detection circuit 12 is input to the speed control circuit 13. The speed overturning circuit 13 operates according to the difference between the command signal ω79 from the speed command circuit 11 and the speed detection signal ω from the speed detection circuit 12, and outputs a torque current command signal It9 for the induction motor 2. . Output signal of speed control circuit 13
is input to the slip frequency calculation circuit 15 and the q-axis current control circuit 20. The output signal ω2 of the speed detection circuit 12 is also input to the excitation current command calculation circuit 14. The excitation current command calculation circuit 14 operates the induction motor 2 according to the speed detection signal ω2.
In order to perform field weakening control, an excitation current command signal ■♂ and a magnetic flux signal Φ2 are output. The excitation current command signal - is input to the d@ current control circuit 21, and the magnetic flux signal Φ2 is input to the slip frequency calculation circuit 15. Slip frequency calculation circuit 1
5 calculates slip frequency command signals ω,' from the signal engineer ♂ and Φ2.

All nine frequency converter numbers ω of the slip frequency calculation circuit 15,
1 and the speed detection signal ω of the speed detection circuit 12 are the adder 16.
is input. The adder 16 adds the signals ω- and ω7 to obtain a primary frequency signal ω-. The output signal ωl of the adder 16 is input to the oscillator 17. The oscillator 17 oscillates according to the primary frequency signal ω1 of the adder 16, and generates a sine wave signal sinω.

Output ωSω1t. The output signal of the oscillator 17 is input to a current component detection circuit 19 and a current command calculation circuit 22.

The current component detection circuit 19 inputs the alternating current detection signal i from the current detector 18, and outputs the signals sinωlt and CO5.
With ω1t as a reference, its components Ia and Iq are output.

In this case, Id is the magnetic flux direction component of the current, and ■ is the component perpendicular to it. The d-axis current component 1d of the current component detection circuit 19 is input to the d-axis current control circuit 21, and the q-axis current component I, is the same as the q-axis 1! is input to the flow control circuit 20. The q@current control circuit 20 outputs a working signal, $11, in accordance with the deviation between the torque current detection signal and the q@current component component.

The d-axis current measurement 1 circuit 21 outputs a working signal Id rate* in accordance with the deviation between the excitation current command signal ♂ and the d-axis current component Ia. Signal I4■ and ``'' 1 digit current command calculation circuit 2
2 is input. The current command calculation circuit 22 generates signals sinω, t, cosω, t according to the signals d0 and 111.
An alternating current command signal i is output based on the current command signal i.

The output signal i of the current command calculation circuit 22 is input to the change calculation circuit 23, and the current detection signal i from the current detector 18 is input to the change detection circuit 24. The variation calculating circuit 23 calculates the variation i,' of the input signal i. The change signal it' is input to the current change control circuit 25. The change detection circuit 24 calculates the change 11 of the input signal i. An eleven-digit change signal is input to the change control circuit 25. The current change control circuit operates according to the deviation between the signals i and 11, and outputs a control signal for controlling the frequency converter 1. The frequency converter 1 is controlled by the output signal of the current change control circuit 25.

Next, its operation will be explained. The speed control circuit 13 outputs a torque current command signal L'', which is a component orthogonal to the magnetic flux of the induction motor 2. On the other hand, the excitation current command calculation circuit 14 outputs the magnetic flux signal of the induction motor 2 based on the speed detection signal ω. 2
Outputs the excitation current command signal, which is the component that generates the magnetic flux. FIG. 2 shows a specific example of the excitation current command circuit 14. In FIG. 2, a magnetic flux command signal Φ21 corresponding to the speed detection signal ω is determined by a function generator 141.

The magnetic flux command signal Φ2'' and the magnetic flux signal Φ2 calculated by the magnetic flux calculation circuit 142 are input to the optical control circuit 143 for excitation.

The excitation current control circuit 143 operates according to the deviation between the signals Φ21' and Φ2, and outputs the excitation current command signals 1 and 11.

The magnetic flux calculation circuit 142 calculates 2 of the magnetic flux signal as a first-order delay calculation of the signal engineer and the umbrella.

Here, M is the excitation inductance of the induction motor 1, T2
is a quadratic time constant, and S is a Laplace operator.

In this way, the signals I-, I♂, and Φ2 are calculated.

Returning to FIG. 1, the slip frequency calculation circuit 15 calculates the slip frequency command signal ω- from the torque current command signal 1f4' and the magnetic flux signal Φ2. FIG. 3 shows a specific example of the slip frequency calculation circuit 15. Divider 151 and first-order lag circuit 15
2, the equation (1) is calculated, and the slip frequency command signal ω- is obtained. In equation (1), k is a constant, and T is a response time constant of the actual torque current to the torque current command signal umbrella. When the slip frequency command signal ω- is obtained by calculating equation (1), the signal ω- and the speed detection signal ω are added in the adder 16,
A primary frequency signal ω1 is obtained. The oscillator 17 oscillates at a frequency corresponding to the primary frequency signal ω1, and generates a sine wave signal sin
Outputs ω, t, cos ω, 1. Current component detection circuit 1
Reference numeral 9 detects two-axis (q-axis, d-axis) components of the current i using the sine wave signal as a reference.

FIG. 4 shows an example of the current component detection circuit 19.

Multipliers 191 to 194 and adders 195 and 196 perform the following calculations. Now, the detected AC two-phase signal is 1α, I
As β, iα= ■(cos (ω1t+θ) 1β= I Hsin (ω, 1+θ)・・・・・・・・・
...(2), the current components Id and Il are calculated as follows. Here, I+ is the peak value of the alternating current, and θ is the angle between the d axis (magnetic flux axis) and the current.

The q-axis current control circuit 20 connects the torque current command signal to the q-axis.
The optical control circuit 21 outputs a signal signal s'' corresponding to the deviation of the axis current component signal signal Ia.The light control circuit 21 outputs a signal corresponding to the deviation of the d-axis current component signal Ia and an excitation current command signal L* for the d-axis and a signal corresponding to the deviation of the optical component signal Ia. ■d
Output IIS. Then, the current command calculation circuit 22 outputs the signal sin according to the signal d**=''(,;**
AC current command signal 1 based on ω, t, cosω+tK
Outputs 1'. FIG. 5 shows an example of the current command calculation circuit 22. Multipliers 221 to 224, adders 225, 226
The calculation of equation (4) is performed by:

・・・・・・・・・(4) Here, in the examples of FIGS. 4 and 5, the three-phase AC signal lα,
iβ or 1α" i p**, but if the induction motor 2 is a 2-phase machine, it is sufficient to perform a known 2-phase to 3-phase conversion. Furthermore, 1 d**, 1, +1 (directly from 1α) It is possible to obtain three-phase alternating current command signals, and the reverse is also possible.As these are all well known, their explanation will be omitted.Furthermore, Fig. 1 shows one of the alternating current command signals. Only the phases are shown.

When the current command signal ++1 is obtained in this way, the change calculation circuit 23 calculates a change signal lf* of 1''.

Further, the change amount detection circuit 24 detects the change amount i of the current detection number 1g. The current change control circuit 25 operates according to the deviation between the signal 124 and it, and the frequency converter 1
Outputs a signal to control the The frequency converter 1 is controlled according to the output signal of the current change control circuit 25. In this way, the amount of change in the current flowing through the electric motor 3 is controlled.

Figure 6 shows the waveforms when the torque current command L'' changes when controlled as described above. In Figure 6, the solid line is for this embodiment, and the broken line is for the conventional example (controlling alternating current (If the current control system is used as a current control system).Since the change in alternating current is controlled, a voltage of 7 ohms can be produced successfully, which is effective in improving characteristics in the high speed region.Therefore, compared to conventional With the control method described above, it was difficult to obtain a good and constant current response from low speed to high speed, but this can be achieved according to the present invention.

In addition, in the embodiment shown in FIG. 1, 1! When the gains of the d-axis and q-axis current control circuits 20 and 21 can be freely selected in the L current ratio change calculation circuit 24, K can be omitted.

Furthermore, the slip frequency command signal ω- may be calculated using the current component signal Id or ω as shown in FIG.

FIG. 7 shows another embodiment of the present invention. In Figure 7,
Parts 1 to 25 represent the same parts as in FIG. The voltage command calculation circuit 26 outputs the signals sinω, t, according to the d-axis and q-axis current control circuits 21.20C+outputs Vt”, Vq”K.
An AC voltage command signal V- is output based on CO3ω,1. This calculation is the same as the calculation shown in FIG. On the other hand, 1! The output of the flow control circuit 25 is the voltage command signal v
It becomes b11. Adder 27 sums signals V- and v bll and outputs v signals for controlling frequency converter 1 . The frequency converter 1 is controlled according to v signals. 7th
d-axis as shown.

The purpose of the present invention can be achieved even if the q-axis current control circuit and the light quality control circuit are arranged in parallel and in a loop.

FIG. 8 shows an embodiment in which the present invention is applied to a synchronous electric motor.

In FIG. 8, numerals 1, 3, and 11 to 25 indicate the same parts as shown in FIG. 1. The synchronous motor 4 is driven by a frequency converter 1, and the relative position of the field F and the armature is detected by a position detector 5. The position detector 5 outputs a sine wave signal corresponding to the relative position of the field of the synchronous motor 4 and the armature. The magnetic flux command circuit 26 outputs a signal Φ that commands the magnetic flux of the synchronous motor 4 in response to the speed detection signal ω. The current component command circuit 27 receives the torque command signal T'' from the speed control circuit 13.
According to the magnetic flux command signal Φ0 from the magnetic flux command circuit 26,
Command of the components of the armature current I a *.

Outputs ■, ' and field current command signal ■f*. The configuration of the current component command circuit 27 is well known and will therefore be omitted.

The field current control circuit 28 receives the field 1! from the current component command circuit 27! It operates according to the deviation between the current command signal It'' and the field current detection signal 11 from the current detector 30.

The output of the field current control circuit 28 is connected to a converter 29,
The converter 29 controls the current flowing through the field F of the synchronous motor 4.

In this way, the embodiment shown in FIG. 1 can also be applied to vector control for a synchronous motor, and it is possible to improve the tracking accuracy and responsiveness of the armature to the flow command.

Further, the embodiment shown in FIG. 7 can be applied to a synchronous motor.

〔Effect of the invention〕

As described above, according to the present invention, the current of the AC motor can be made to accurately follow the current command regardless of the operating speed. As a result, highly accurate and highly responsive torque control can be performed.

In addition, although the magnetic flux of the electric motor was controlled in the above-mentioned embodiment, the magnetic flux may be constant. Furthermore, although the control in the above embodiments has been described as being implemented by a hardware circuit, it can also be implemented by software using a microcomputer or the like. In this case, even if the entire control is performed by software,
It is also possible to execute part of the process using software and process the rest using hardware.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 to 5 are block diagrams of a specific example of the circuit shown in FIG. 1, and FIG.
The operating waveform diagram in the figure, FIGS. 7 and 8 are configuration diagrams showing other embodiments of the present invention, respectively. 1... Frequency converter, 2... Induction 4 motor, 18...
・Current detector, 19...Current component detection circuit, 20...
・q-axis current control circuit, 21...d-axis current control circuit, 2
2...Current command calculation circuit, 24...Change detection circuit, 25...1! Streamification control circuit.

Claims (1)

[Claims] 1. A frequency converter that outputs variable frequency/variable voltage alternating current, and an alternating current motor driven by the frequency converter;
A current obtained by comparing two-axis current components detected by a current component detection means for detecting two-axis components of an AC input current of the AC motor with a torque current command signal and an excitation current command signal, respectively, and the two-axis current components detected by the current component detection means. current command means for inputting a deviation and outputting a sine wave current command signal; and a current change for controlling the frequency converter by inputting a current change amount obtained by comparing the change amount of the alternating current input current and the sine wave current command signal. A control device for an AC motor, comprising rate control means.