JPH0260485A - Controller for induction machine - Google Patents

Abstract

PURPOSE:To reduce the expansion of a system as a whole, and to improve control performance by converting encoder pulses detecting the rotational speed of an induction machine into an analog value by a frequency-voltage converter, adding the analog value and the slip frequency of the induction machine and determining the primary frequency command of the induction machine. CONSTITUTION:Speed pulses omegam detected by a pulse encoder 3 are converted into an analog voltage value by a frequency-voltage converter F/V11. A primary- frequency command signal omega1 obtained by analogically adding the analog signal omegam and an analog signal omegas output from a slip frequency commander 10 is input to a voltage-frequency converter V/F 12 and changed into voltage pulses, and the voltage pulses are input respectively to coordinate converters 6, 7. Accordingly, both the frequency-voltage converter 11 and the voltage-frequency converter 12 may be used in the converters having high frequency, thus realizing the converters delay of which is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an induction motor used in, for example, a ZARPO device.

[Conventional technology]

In recent years, induction machines have been increasingly used for variable speed drives using vector control. In this vector control, the -order frequency command is determined by adding the slip frequency and the rotation speed. When used as a pulse encoder speed detector, the -th order frequency command is determined by adding the pulse corresponding to the slip frequency and the encoder output pulse.

[Problem to be solved by the invention]

The delay in the pulse addition itself can be ignored, but the pulse corresponding to the slip frequency command has a much lower frequency than the encoder pulse, so it was difficult to reduce the delay in the oscillator that produces the pulse. . As a result, the system was delayed and the control performance deteriorated.

Therefore, the present invention can reduce the delay of the system as a whole,
An object of the present invention is to provide a control device for an induction machine that improves control performance.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a converter that controls voltage and frequency to drive an induction machine, and divides the primary current of the induction machine into an excitation current component and a torque current component orthogonal to this excitation current component. In a device that controls the input by controlling the rotational speed of the induction machine,
') means for converting the detected L fc y near -tano e # into an analog value using a frequency-voltage converter, and adding this to the slip frequency of the induction machine to determine the primary frequency command of the induction machine; It is equipped with

[Effect]

In the present invention, an encoder pulse is frequency-voltage converted to an analog value, and then added to a slip frequency command in analog form to obtain a -missing frequency command. The delay at this time is the delay of the frequency-voltage converter and the -missing frequency command A' pulse oscillator, but even if they are combined, the delay is less than that of a low-frequency oscillator such as a slip frequency. , This reduces system lag and improves control performance.

Here, we will explain why low frequency voltage-frequency converters have a large delay. Generally, a voltage-to-frequency converter integrates the input, and when the value exceeds a reference voltage, outputs a constant width pulse and partially discharges. When the value of the integrator that has been reduced thereby exceeds the reference voltage due to charging again, the integrator operates as an oscillator by repeatedly emitting pulses. To create a voltage-frequency converter in the low frequency range, it is necessary to have a large integration time constant. The slip frequency is usually several percent of the -order frequency, and is about 10% at most.

Therefore, a voltage-to-frequency converter that produces a slip frequency pulse will have a delay of at least ten times as much as a voltage-to-frequency converter that produces a -order frequency.

Therefore, even if the number of frequency-voltage converters is increased by one, the delay of the system as a whole can be reduced by using a voltage-frequency converter with a small delay by performing analog addition.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an embodiment of an induction motor control device according to the present invention. First, the main circuit will be explained. The converter 1 is a voltage source inverter, which controls voltage and frequency to drive an induction machine (IM) 2. The speed of the induction machine 2 is detected by a pulse encoder (PE) J. Current detectors 41 and 42 detect one forming flow signal iu and lv of the induction machine 2.

Next, the control system will be explained. The speed pulse ωm detected by the pulse encoder 3 is converted to a frequency-voltage converter (F/V
) I1 is converted to an analog voltage value, and the speed command (
ωrrl*) 14, and a torque current command (ir*) is output from the speed amplifier 9. Current detector 41.4
The current signals iu and iv output from 2 are sent to the B coordinate converter 6.
The excitation current component signal lδ and the torque current component signal 1 are
．． is converted to Here, torque current component signal 1. is compared with the torque current command lr* output from the speed amplifier 9 and inputted to the current amplifier 8. Further, the excitation current component signal lδ is compared with an excitation current command (ia*) 1 s and input to the current amplifier 8. The current amplifier 8 converts these current errors into voltage commands and inputs them to the A coordinate converter 7.

This coordinate converter 7 applies coordinate conversion to the voltage command PW
It is input to the M current control circuit 5 as a three-phase voltage command. P
The WM current control circuit 5 controls the converter 1 so that each current component matches the -5=order for each phase.

Here, the analog signal ω output from the frequency-voltage converter 11. The primary frequency command signal ω1 obtained by adding the analog signal ω8 outputted from the slip frequency command unit 10 in an analog manner is input to the voltage-frequency converter (V/F) 12 and converted into a voltage pulse. are input to coordinate converters 6 and 7, respectively.

As a result, the frequency-to-voltage converter 11. Both of the pressure-frequency converters 12 can be of high frequency, making it possible to realize a converter with small delay, and the delay as a whole is lower than when only the slip frequency is converted to the voltage-frequency converter 11 and digitally added. A small system can be realized.

Note that the present invention is not limited to the embodiments described above; for example, in the embodiments described above, the voltage source inverter 1 is used as the main circuit converter, but a current source inverter or the like may also be used. good.

Of course, various modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention described above, encoder pulses are converted by a frequency-voltage converter, and values obtained by analog addition are converted into pulses by a voltage-frequency converter, thereby converting a high frequency voltage-frequency converter. It is possible to provide a control device for an induction machine that can utilize the lag of the frequency-to-voltage converter, has a small lag because it is on a high frequency scale, and provides a control system with a small lag as a whole.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of an induction machine control device according to the present invention. 1...Voltage type inverter (converter), 2...Induction machine, 3.../Gurusu encoder, 41.42...t
Flow test 1fj D, 5...Taki current control circuit, 6,7...
・Coordinate converter, 8... Current amplifier, 9... Speed amplifier, 10... Slip frequency command device, 1 No.... Frequency-voltage converter, 12... Voltage-frequency converter, 13・
... Excitation current command, 14... Speed command.

Claims (1)

[Claims] In a device that controls input to a converter that controls voltage and frequency to drive an induction machine by dividing the primary current of the induction machine into an excitation current component and a torque current component orthogonal to the excitation current component, the induction A frequency-voltage converter converts an encoder pulse that detects the rotational speed of the machine using a pulse encoder into an analog value, and adds this to a slip frequency of the induction machine to determine a primary frequency command of the induction machine. A control device for an induction machine.