JPS61116996A - Controller of synchronous motor - Google Patents

Abstract

PURPOSE:To smoothly operate a synchronous motor by operating a forcible commutation type frequency converter in parallel with a load commutation type frequency converter in intermittent operation range, thereby reducing the torque ripple generated in the motor. CONSTITUTION:An inverter 27 communicates by a forcible communicating circuit or forcibly commutates by an inverter using a self-extinguishing type power converter such as a large power transistor. A frequency converter 100 for commutating a load is mainly operated always in an operating range exceeding an intermittent starting range to control a synchronous motor 15 at variable speed. A frequency converter 200 for forcibly commutating with the intermittent starting range as a center is operated. Thus, the torque of the motor 15 during the intermittent start can be reduced or the increase in the generated torque ripple can be suppressed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a control device for a synchronous Ie camera that can improve the operating characteristics in the low speed region of a thyristor motor drive system that performs variable speed control of a synchronous motor. It is something.

[Technical background of the invention and its problems] Thyristor motor drive systems are employed in various fields as motor drive systems that operate synchronous motors at variable speeds. In particular, since the back electromotive voltage of the synchronous motor is used to commutate the load of the inverter of the thyristor motor, the main circuit configuration is simple, the voltage of the main circuit can be easily increased, and high efficiency operation is possible. Ideal for variable speed operation. An example of the configuration of this thyristor motor drive system is shown in FIG.

In this figure, 11 is the input AC III, 12 is the rectifier, and 13 is the input AC III.
14 is a DC reactor, 14 is an inverter, 15 is a synchronous motor, 16 is a speed reference setter, 17 is a position detector that detects the position of the field of the synchronous motor 15, 18 is a speed controller,
19 is a current controller, 2o is a current detector, 21 is a phase controller, 22 is a β control device S23 is a current intermittent command device. The thyristor motor drive system shown in FIG. 3 is a known drive system, and its outline will be explained next. AC power from an input AC power source 11 is converted into DC power by a rectifier 12, smoothed by a DC reactor 13, and inversely converted into variable frequency AC power by an inverter 14. This inversely converted AC power is transferred to the synchronous motor 15.
Synchronous electric supply! 115 is operated at variable speed. The operating speed of the AC motor 15 is set by a speed reference setting device 16, and the speed reference signal and the operating speed signal of the synchronous motor 15 detected by the position detector 17 are compared and controlled by a speed controller 18.
A speed controller 18 outputs a current reference. This current reference signal and the detection signal of the current detector 20 are compared and controlled by the N-current controller 19, and the DC power output from the rectifier 12 is adjusted via the phase controller 21. If the DC power is increased, the generated torque of the synchronous motor 1115 will increase and the speed will increase, and if the DC power is decreased, the synchronous motor 15 will similarly decelerate. The synchronous motor 15 detects the position of the field by the position detector 17, and β
This position signal is input to the controller 22, and the β controller 22 controls the load commutation timing of the inverter 14 based on this position signal, and the inverter 14 is a synchronous motor).
°″″：1iJIllJJlrfi″′″ii; *
'ir h l 56 Synchronous motor 15 using the method described above
However, since the back electromotive force is low in the low speed region of the synchronous motor 15, the inverter 14 cannot perform the load commutation described above in the low speed operation region. For this reason,
In such a low speed operation region, the current controller 19 is controlled by the current intermittent command 23 at each commutation timing of the inverter 14 corresponding to the position detection signal of the position detector 17,
As a result, the DC current output from the rectifier 12 is controlled to zero, the current of the inverter 14 is also made zero at each commutation timing, and such operations are sequentially performed (repeatedly, the synchronous motor 1
Accelerate 5. This type of commutation method is called intermittent starting in thyristor motor drive systems, and it
Intermittent starting is commonly used below 0% speed.

Figure 4(a) shows the DC current waveform flowing through the DC reactor 13 during this intermittent start. ! The generated torque of one aircraft 15 is illustrated in FIG. 4(b).

When the operating speed is low, such as immediately after the synchronous electric motor 8115 is started, the period during which the DC N flow is reduced to zero can be relatively ignored. For example, in FIG. 4(a), 1 dl of DC current is passed from time r11q to time t12, and the DC current is made zero from time t12 to time t21. Also time t21
Then, the DC current rd1 is caused to flow until time t22. Similarly, the synchronous motor 15 is accelerated while the current is continued in sequence,
A DC current is applied from time t51 to time t52, and at time t
The DC N current is made zero from 52 to time t61. The synchronous motor 15 further accelerates and reaches a predetermined operating speed at time t8.
1, the inverter 14 switches to load commutation, so the DC current becomes continuous. During this intermittent start, the DC current is made zero from time t12 to time t21 and from time t52 to time t61.
The time it takes is determined by the conditions of the inverter 14, so it is constant. Therefore, from time t11 to time t21 and time t5
Comparing the average 'Il current from 1 to time t61, the average value of the DC current is significantly smaller in the latter period.

Therefore, since the torque generated by the synchronous motor 15 corresponds to the average value of the DC current, the synchronous motor 15
decreases as the operating speed increases.

At this time, since the DC reactor 13 tries to suppress the rise of the output current of the rectifier 13, this tendency becomes more severe as the operating speed of the synchronous motor 15 increases. Therefore, the generated torque rapidly decreases to a large extent around time t81 compared to around time t11.

The conventional thyristor motor drive system that operates as described above has the following technical problems.

(1) During intermittent starting, as mentioned above, the synchronous motor 1
The generated torque of No. 5 is large (pulsates), and the torque ripple rapidly increases, which adversely affects the mechanical system including the synchronous electric motor 115.

(2) In this intermittent starting region, the generated torque ripple is significantly reduced, making smooth starting and acceleration impossible.

[Object of the Invention] The present invention has been made in view of the above-mentioned drawbacks of the prior art.It is an object of the present invention to reduce the torque ripple generated by a synchronous motor and to achieve smooth operation in the low speed range where intermittent starting has conventionally been performed. The purpose of the present invention is to provide a control device for a synchronous motor that can perform the following steps.

[Summary of the Invention] In the present invention, in the low speed range where intermittent starting is performed, a forced commutation frequency converting device is connected in parallel with a conventional frequency converting device that performs load commutation, and both of the devices are connected during intermittent starting. Operate frequency conversion equipment. This improves the armature current waveform supplied to the synchronous motor, thereby suppressing an increase in the torque ripple generated by the synchronous motor and a decrease in the generated torque. Said'
j! The following methods are available to improve the machine electron current.

(1) Waveform correction is performed by supplying current from a forced commutation frequency converter to compensate for the shortfall in armature current due to intermittent starting of a frequency converter that performs load commutation.

('2) Both frequency converters are operated in parallel to improve the N-stream waveform.

(3) In the intermittent start region, only the forced commutation frequency converter is operated.

[Embodiment of the Invention] An embodiment of the present invention is shown in FIG. (in this figure)
3, 8, 0, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, and 8. In this figure, 24 is a rectifier, 25 is a DC reactor, 26 is a filter capacitor, 27 is an inverter, 100 is a frequency converter that performs load commutation, and 200 is a frequency converter that performs forced commutation.

In FIG. 1, a rectifier 24 converts the AC power of the input AC N source 11 into DC power, which is smoothed by a DC reactor 25 and a filter capacitor 26. This DC power is converted back into AC power by the inverter 27. The inverter 27 is a forced commutation inverter that performs commutation using a forced commutation circuit or using a self-extinguishing power conversion element such as a high-power transistor. The frequency converter [100] that performs load commutation is always actively operated in the operating range exceeding the above-mentioned intermittent start range, and as mentioned above, the frequency converter [100] The electric motor 15 is controlled at variable speed. On the other hand, there is a frequency conversion device 2 that performs forced commutation mainly in the intermittent starting region.
00 is driven. This situation will be explained using FIG. 2.

In FIG. 2, (a) is the output current waveform of the frequency converter ai oo that performs load commutation, (b) is the output current waveform of the frequency converter 200 that performs forced commutation, and (C) is the output current waveform of the synchronous motor 15. The armature current waveform supplied to the is illustrated. As described above, when the synchronous motor 15 is started intermittently, the output current waveform of the frequency converter 100 that performs load commutation changes from a 120° square wave to a current waveform at each commutation timing. The frequency converter 200 that performs forced commutation is operated at each timing of commutation of the inverter 14, and the M'Rm machine 15 is operated by the commutation of the inverter 14.
The insufficient current is supplied as shown in FIG. 2(b). As shown in the figure, N flow impulses are transferred to inverter 2
7 is easy because the inverter 27 is of the forced commutation type as described above. As a result, the waveform of the armature current supplied to the synchronous motor 15 can be improved to a 12° square wave current as shown in FIG. 2(C).

During intermittent starting of the synchronous motor 15, the load commutation type frequency conversion device 100 and the forced commutation type frequency conversion device 200
When operated as described above, the armature current waveform of the synchronous motor 1ilJl115 is improved, and the synchronous motor 1 during intermittent starting
It is possible to suppress the decrease in the generated torque and the increase in the generated torque ripple.

[Other Embodiments] In the present invention, the method of operating the load commutation type frequency converter 5i 100 and the forced commutation type frequency converter 200 is not limited to the method illustrated in FIG. You can also use the following method.

(1) In the intermittent start region, the frequency converter 200 that performs forced commutation is replaced by the frequency converter 100 that performs load commutation.
The armature current waveform supplied to the synchronous motor 15 is improved from the 120° square wave current waveform.

('2J In the intermittent start region, only the frequency converter 200 that performs forced commutation is operated to improve the armature current waveform supplied to the synchronous motor 15 from the 120° square wave current waveform.

As another embodiment of the present invention, a mechanical or electrical switch is provided at the output of the frequency converter 200 of the forced commutation type, so that the forced The commutation type frequency converter 200 may be separated. With this system configuration, the forced commutation type frequency converter 200 can have a voltage rating of about 1/10 or less of that of the synchronous motor 15, so that a compact and economical system can be configured.

In addition, the forced commutation frequency converter 100 may be used as an overvoltage suppression circuit of the load commutation frequency converter 200 in a high-speed operation region.

The forced commutation type frequency conversion device 100 is not limited to the circuit configuration shown in FIG. 1, and may be a frequency conversion device of AC to AC conversion. Furthermore, there are no limitations on the configuration, such as whether the load commutation type frequency converter 200 has a 6-pulse or 12-pulse configuration, or how far the phase of the armature current is advanced in order to perform load commutation.

1, within the scope of not changing the gist of the pond water invention;
Various variations can be constructed.

[Effects of the Invention] According to the present invention, a compact and economical forced commutation frequency converter is operated in parallel with a load commutation frequency converter in an intermittent operation region, and It is possible to provide a control device for a synchronous motor that can improve the armature current waveform of the synchronous motor and suppress an increase in torque ripple generated by the synchronous motor and a decrease in generated torque.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an IF flow pattern according to an embodiment of the present invention, and FIG. 3 is a plotter diagram of a conventional synchronous motor control IH setting. FIG. 4 is a waveform diagram of the DC current and generated torque in the low speed region of FIG. 3. 11... Input AC power supply, 12... Rectifier, 13...
・DC reactor, 14... Inverter, 15...
Synchronous motor, 16... Speed reference, 17... Phase detector, 18... Speed controller, 19... Current controller, 2
0... Current detector, 21... Phase controller, 22...
・β controller, 23... Current intermittent command device, 24... Rectifier, 25... DC reactor, 26... Filter capacitor, 27... A 4 inverter, 10o
...Load commutation type frequency conversion device, 200...Forced commutation type frequency conversion device. 1ml 1 2M Figure 3 Figure 4

Claims (1)

[Claims] A forced commutation frequency converter is provided in parallel with a load commutation frequency converter that discriminates the terminal voltage phase of the synchronous motor and supplies an armature current of an advanced phase during power running operation, and A control device for a synchronous motor, characterized in that the forced commutation type frequency converter is operated continuously or intermittently in a low speed operation region of the motor.