JPS6359768A - Phase control of cyclo converter - Google Patents

Abstract

PURPOSE:To improve the performance of a control device, by a method wherein the deviation of phase between the control device and an object to be controlled is corrected by optimizing the phase of a commanding reference sine wave signal as well as a detecting reference sine wave signal with respect to a reference sine wave phase. CONSTITUTION:An induction motor 2 is controlled by a cyclo converter 1 through vector control. An exciting current command Id and a torque current command Iq are inputted into a 2-phase/3-phase converter 9 and are operated together with a 2-phase sine wave signal, produced based on a frequency command (OMEGA1), thereafter, are outputted as the AC current commands (iu), (iv), (iw) of respective phases. The AC current control circuit 6, 7, 8 of respective phases operate phase control circuits 3, 4, 5 so that differences between the AC current commands (iu), (iv), (iw) and actual currents (iu'), (iv'), (iw') become zero. The control circuits are constituted of digital apparatuses, therefore, the delay of command transmission and the delay of detection, which are accompanied by sampling, are generated. In order to prevent the deterioration of accuracies due to the delays, the AC current commands are advanced by a phase angle theta1, corresponding to the delay of the command transmission, and the values of detection are advanced by another phase angle theta2, corresponding to the delay of detection, to process them.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention supplies a desired frequency to an electric motor without phase delay in order to drive an alternating current machine driven at variable speed by a cycloconverter using a vector control device. The present invention relates to a phase control device for a cycloconverter.

[Conventional technology]

In AC variable speed drive systems using cycloconverters, various studies have recently been conducted to improve the output frequency using circulating current type cycloconverters, etc., and to expand their application to high-speed rotating machines. In this case, compensating for the current phase shift is known, for example, from Japanese Patent Publication No. 59-23195.

Furthermore, with the rapid progress of microprocessor technology in recent years, it has become possible to provide a control device that is cheaper than conventional analog circuits by performing control calculations for the drive system using a digital computer.

However, as a result, the control system changed from an analog continuous system to a sample value control system, and problems unique to sample value control have arisen. Particularly, when trying to perform control up to a high frequency as described above, the sampling time cannot be ignored.

[Two points while the invention is trying to solve the problem]

Conventionally, when increasing the output frequency of a cycloconverter and increasing the rotational speed of a motor, a control method has been proposed for compensating for the adverse effect of response delay in a current control system, as shown in Japanese Patent Publication No. 59-23195. however,
These conventional methods are only considered in a continuous system, and when sample value control is performed using a digital computer as a control device, there may be a delay in transmission of command signals, a delay in response due to a delay in detection of sample values, etc. has not been taken into account at all. An object of the present invention is to compensate for the response delay of a control system due to sample value control.

[Means for solving problems]

Focusing on the fact that when AC signals are controlled by sampled value control, problems specific to sampled value control, such as delays in command transmission and delays in detected values, result in phase delays in the amount of alternating current.1
In the present invention, a reference sine wave generator for commands and a reference sine wave generator for detection, whose phase can be advanced in advance, are provided in order to compensate for a one-phase delay with respect to the reference AC command of the control system. It is characterized by being able to optimally adjust the phase of each sine wave signal. According to the present invention, this is achieved by compensating for the response delay of the control system.

[Effect]

In the present invention, a plurality of first and second sine wave generators are provided, and the phase angle θ is individually adjusted to 8.
The command reference sine wave generator, which is a sine wave generator, is a reference sine wave generator for the control system.

By advancing the phase, it is possible to correct the transmission delay that occurs between the DC current command and the AC voltage command that causes the actual AC current to flow.

Further, the detection reference sine wave generator, which is the second sine wave generator, can similarly advance the phase to some extent to correct the detection delay caused by the detector.

By the above-mentioned functions, the phase of the controlled object and the control system can be matched to improve the response.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a device in which a cycloconverter 1 (not shown) converts a commercial frequency three-phase AC power source into a variable voltage variable frequency power source and supplies it to a three-phase induction motor 2, which is a load. This figure shows an example of a control circuit for causing a sinusoidal alternating current to flow through the induction motor 2. The cycloconverter 1 is configured with a circuit in which a forward/reverse converter consisting of a pair of thyristor converters connected in antiparallel is provided for each phase of a three-phase alternating current.

The output voltage of the cycloconverter 1 is determined by Gate Pu given from the phase control circuit @3, 4.5 provided for each phase.
It is varied by the 1se signal. On the other hand, the control circuit includes an AC current control circuit 6 that controls each phase AC current of the induction motor 2;
7, 8. A two-phase/three-phase conversion circuit 9 that outputs a three-phase sine wave command, a reference sine wave generator 20 according to the present invention, a primary current of the induction motor with a component in the same direction as the rotating magnetic field (excitation current component Id
) and an orthogonal component (torque current component q).

It is well known that there is a vector control method as a method for variable speed control of an induction motor in the same way as a DC motor. This vector control means that the primary current of the induction machine is divided into a component in the same direction as the rotating magnetic field (Iih magnetic current component knee) and a component orthogonal to the rotating magnetic field (Iih magnetic current component knee).
Separate the torque current components into
(2), and the magnitude of Iq is controlled, and the phase of the current with respect to the rotating magnetic field is controlled by giving a slip frequency according to the ratio of Iq/I-. In FIG. 1, in order to perform the above-mentioned vector control, the excitation current component A- and the torque current command Iq- are set to 2 from another circuit (not shown).
It is input to the phase/three-phase conversion circuit 9, and the frequency command ω1m of the negative order current is input to the reference sine wave generator 2o. The reference sine wave generator 20 generates two acupressure sinusoidal signals (sinωxt) with a 90° phase difference.

cosω11) is produced, and its output is input to the two-phase/three-phase change circuit 9. In the 2-phase/3-phase conversion circuit 9, (1)
, (2) are performed to obtain alternating current commands 1u", iv"gl- for each phase.

(1) The AC current control circuits 6, 7.8 are provided with the AC current commands 1u"tlv"l 1w' for each phase, the amount of AC feedback detected by the current detector 12, and the AC current feedback amount detected by the current detector 12. The deviation of is input, and its output signal is a control signal e u according to the output voltage of each phase converter.
'He v', Q- are output. In addition, a three-phase/two-phase conversion circuit 11 is provided for the purpose of compensating for control errors due to response delays in the AC current control system, and this circuit includes:
The alternating current feedback amount (i uj l Vtiw) is input, and Ia and Iq times signals are detected by inverse calculation of equations (1) and (2). Note that the IcyIq signal and the command value are ■
It is assumed that the deviation of -fist and force q* is a control error due to a response delay of the current control system, and this response delay of the control system is compensated for by another circuit not shown.

When the control calculations described above are performed by a digital computer, the configuration is as shown in FIG. 2.

15 in FIG. 2 shows a digital computer, and the other circuits are as follows:
These are the same as those indicated by the same numbers in FIG.

In FIG. 2, an exciting current command Ii*, a torque current command 1q., and a number frequency command ωl.
is input as digital data to the computer 15, and the above-mentioned control calculations are performed at predetermined intervals.

The calculation results are input to each phase control circuit 3, 4.5 as each phase voltage command eu''vev'ge-.

The operation will be further explained with reference to FIG. FIG. 3 (1) shows the operating waveforms of the U-phase voltage command eu" and the U-phase AC current 1u, and FIG. 3 (2) shows the timing at which the digital computer 15 starts calculation at each predetermined sampling time. ,
FIG. 3(3) shows, as a time chart, the time during which the computer 15 calculates according to the timing.

Now, at time 1, the command values Ia fist, I fist, ω1-
The computer 15 takes in the data of mu g lv y 1w and the feedback amount mu g lv y 1w, and the calculation ends at time tz.

As a result, the voltage command euψH8v", 8- is output. The same operation is repeated thereafter. 8'uψ shown by the solid line in Fig. 3 (1) instantaneously outputs the specified voltage command without calculation delay. This corresponds to the voltage command waveform configured in the analog control system.The alternating current flowing in that case is shown by the solid line l'u.In contrast, at time t2
Since the voltage command eu" is output at a timing delayed by , it is shown that due to sample value control, a current flows that is delayed by one phase angle θ1 with respect to the original phase.This phase delay is normally caused by a control error due to the response delay of the current control system described above. Similarly, special public service 59-23
If a compensation circuit with the concept as shown in No. 495 is configured, compensation may be possible, but there is a drawback that excessive compensation cannot be made due to the delay of the compensation circuit.

In the present invention, the phase delay angle θ1 by the sample value control is
By advancing the reference sine wave command by 01 in advance, the alternating current is made to flow in the original current phase. In other words, in Fig. 3 (1), the dotted line e- is replaced by the solid line e'-.
By advancing to the timing of , the original alternating current phase (the timing of i' in the solid line) is achieved. In addition, as with the command, there is a phase lag in the detection of the feedback amount, so the reference sine wave generation circuit is separated into the command side and the detection side so that the detection phase can be adjusted on the detection side in the same way as on the command side. This is the feature of the present invention. The specific circuit configuration is shown in FIG. FIG. 4 shows the internal configuration of the reference sine wave generator 20 shown in FIG. 1, which is a circuit characteristic of the present invention. The input signal of the frequency command ω1* is integrated by the integrating circuit 21, a signal of fωtit is output, and the command side phase adjustment signal θ1 and the detection side phase adjustment signal θ2 are input,
The fωit signal and the θ signal or C2 are added in separate adders 22 and input to separate two-phase sine wave output circuits 23. The two-phase sine wave output circuit for command is 5 inches (ωx fist
+θt), cos ((111 fist + 01)), and the detection two-phase sine wave output circuit outputs a 5in (
ωtt+02) l C08(+11 s t+02)
outputs a two-phase signal.

〔Effect of the invention〕

According to the present invention, with respect to the reference sine wave phase of the control device,
By optimizing the phase of the reference sine wave signal for command and the phase of the reference sine wave signal for detection, the phase shift between the control device and the controlled object can be corrected, unstable elements can be removed, and the control device can be improved. It has the effect of improving performance.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a circuit diagram of an embodiment of the present invention. FIG. 3 is an explanatory diagram of the operation during sample control, and FIG. 4 is a detailed block diagram of two-phase advance. 2o... Reference sine wave generator, 21... Integrator, 22
...Adder, 23...Two-phase sine wave output, θl...
Command phase advance angle, C2...Detection phase advance angle, ω1
1...-Number frequency command.

Claims (1)

[Claims] 1. A cycloconverter device that supplies an AC power source with variable voltage and frequency to an AC motor, a phase adjuster and a control circuit for each phase of the cycloconverter for controlling the phase of each phase using a microprocessor, and a control circuit for controlling the phase of each phase of the cycloconverter using a microprocessor; A sine wave command generator with two-phase/three-phase conversion that outputs a sinusoidal command to a control circuit, and a two-phase reference frequency generator that outputs a reference frequency signal to the sine wave command generator, The phase control device for a cycloconverter is characterized in that it has a plurality of reference frequency generators, such as a first frequency generator and a second frequency generator, and the phase angle θ of each can be adjusted individually. Phase control device for cycloconverter.