JPS63114591A - Modulation system of flux control type inverter - Google Patents

Abstract

PURPOSE:To restrain beat, appearing in the output current of an inverter, by a method wherein the output of a flux regulating means is synchronized substantially with a modulated wave. CONSTITUTION:A synchronized signal is outputted from a flux command value generator 13 to a modulated wave generator 15, therefore, a flux commanding value is synchronized with a modulated wave. Therefore, the output of a flux regulator, inputting a deviation between the flux command value and the actual value of flux, is synchronized substantially with the modulated wave. According to this method, a time point, whereat the output of the flux regulator 14 passes zero point, becomes the same as a time point, whereat the modulated wave passes a zero point, whereby beat in the output current of a transistor inverter 3 may be restrained.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention relates to a modulation method for a magnetic flux control type inverter that outputs alternating current of variable voltage and variable frequency. 1 is a circuit diagram showing a conventional example of a modulation method of a controlled inverter. In FIG. 2, DC power from a DC power supply 2 is converted into AC power of a desired voltage and frequency by a transistor inverter 3 made up of transistors, and a trap is created to drive an induction motor 4 at variable speed. It has become.

In order to output such variable voltage/variable frequency alternating current power, the transistor inverter 3 is controlled as follows.

That is, the output voltage of the transistor inverter 3 is inputted to the magnetic flux detector 12 via the isolation transformer 11.
By integrating the output voltage of the transistor inverter 3, that is, the terminal voltage of the induction motor 4, the actual value of the stator magnetic flux of the induction motor 4 is obtained.

On the other hand, since a magnetic flux command value is output from the magnetic flux command value generator 13, the deviation between this magnetic flux command value and the actual magnetic flux value obtained as described above is determined for each phase, and this deviation is used for magnetic flux adjustment. This magnetic flux regulator 1
From 4 onwards, a voltage command value such that the actual magnetic flux value matches the magnetic flux command value is output for each phase. This voltage command value is input to a modulator 16 provided for each phase.
The modulated wave output from the is input.

The modulator 16 configured with a comparator sends a modulation signal obtained by comparing the above-mentioned magnitude relationship between the two human forces to the ignition pulse generator 17, and the ignition pulse generator 17
The transistor inverter 3 turns on and off the transistors constituting it sequentially by the firing pulses for each phase output from the transistor inverter 3, and adjusts the voltage and frequency of the alternating current that is its output to desired values. Can be set to

There is a large difference between the frequency of the magnetic flux command value output from the magnetic flux command value generator 13 of the transistor inverter 3 which is operated under control as described above, and the frequency of the modulated wave output from the modulated wave generator 15. The magnetic flux regulator 14 is not large.
is saturated, the point at which the output of the magnetic flux regulator 14 passes through the zero point and the point at which the modulated wave passes through the zero point do not match, which causes the transistor inverter 3 to It has the disadvantage of causing a beat in the output current.

As shown in FIG. 2, when an induction motor 4 is connected to the transistor inverter 3, this current beat causes torque ripple in the induction motor 4, which adversely affects the load connected to the motor 4. Otherwise, various inconveniences may occur, such as generation of noise.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a modulation method for a magnetic flux controlled inverter that can suppress beats in the inverter output current that cause various problems.

[Key points of the invention]

According to the present invention, beats in the output current of a magnetic flux control type inverter are mainly caused by the fact that the time point at which the output of the magnetic flux adjustment means passes through the zero point and the time point at which the modulated wave passes through the zero point do not coincide. It focuses on one thing,
If the magnetic flux command value and the modulated wave are synchronized, the output of the magnetic flux adjustment means and the modulated wave can be almost synchronized, and therefore the beat that occurs in the output current of the magnetic flux control type inverter can be suppressed, and the accompanying This is an attempt to eliminate various inconveniences.

[Embodiments of the invention]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
The contents of the present invention will be described below with reference to the figures.

In FIG. 1, DC power from a DC power source 2 is converted into AC power with a desired voltage and frequency by a magnetic flux control type transistor inverter 3, so that an induction motor 4 is operated at variable speed with this AC power. be able to. In order to output AC power of such desired voltage and desired frequency,
An isolation transformer 11 is provided on the output side of the transistor inverter 3, and the inverter output voltage isolated and taken out is inputted to a magnetic flux detector 12 constituted by an integrating circuit. Furthermore, the deviation between the actual magnetic flux value outputted from the magnetic flux detector 12 and the magnetic flux command value outputted from the magnetic flux command value generator 13 is calculated, and the deviation thus obtained is sent to the magnetic flux regulator 14. Let them input. In this way, the magnetic flux regulator 14 outputs a control signal that makes the input deviation zero, so this control signal and the modulated wave output from the modulated wave generator 15 are connected to the modulator 16 which is composed of a comparator. By inputting the modulated signal to the ignition pulse generator 17, the modulation signal obtained by comparing the magnitude relationship between the two human forces in the modulator 16 is transmitted to the ignition pulse generator 17, and the ignition pulse from the ignition pulse generator 17 is As a result, each transistor constituting the transistor inverter 3 is sequentially turned on and off to output desired AC power, as in the case of the conventional circuit described above in FIG. Although the control portion of the transistor inverter 3 in the embodiment circuit shown in FIG. 1 is shown by a single line for the sake of simplicity, it is actually provided for each phase.

In the present invention, the magnetic flux command value generator 13 issues a synchronizing signal to the modulated wave generator 15, so the magnetic flux command value and the modulated wave are synchronized.

Therefore, the output of the magnetic flux regulator 14, which inputs the deviation between the magnetic flux command value and the actual magnetic flux value, and the above-mentioned modulated wave are almost synchronized. That is, the time when the output of the magnetic flux regulator 14 passes through the zero point and the time when the modulated wave passes through the zero point are almost the same, so that the beat of the output current of the transistor inverter 3 can be suppressed.

〔Effect of the invention〕

According to this invention, in the magnetic flux control type inverter, the beat of the output current of the magnetic flux control type inverter, which occurs because the output of the magnetic flux control means is not synchronized with the modulated wave, is input to the magnetic flux control means. By constantly synchronizing the magnetic flux command value and the modulated wave, the time point when the modulated wave passes the zero point and the time point when the output of the magnetic flux adjustment means passes the zero point can be made to be almost the same, so it is very easy to It is possible to suppress the beat of the inverter output current, and eliminate the problem of noise caused by torque ripple in the load.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional example of a modulation method for a magnetic flux control type inverter. 2...DC power supply, 3...Transistor inverter, 4...Induction motor, 11...
...Isolation transformer, 12...Magnetic flux detector, 13.
...Magnetic flux command value generator, 14...Magnetic flux regulator, 15...Modulated wave generator, 16...
- Modulator, 17...Ignition pulse generator. ：Go・；・′

Claims (1)

[Claims] 1) Input the deviation between the actual magnetic flux value obtained by integrating the output AC voltage of the inverter that converts DC to AC and the separately set magnetic flux command value, and output a control signal to make this input deviation zero. A magnetic flux control device that can set the voltage and frequency of the output alternating current to a desired value using a signal obtained by comparing the magnitude relationship between the modulated wave from the modulated wave generating means and the output signal of the magnetic flux adjusting means. 1. A modulation method for a magnetic flux controlled inverter, wherein a modulated wave from the modulated wave generating means is output in synchronization with the magnetic flux command value.