JPH01283084A - Controller for cycloconverter - Google Patents

Abstract

PURPOSE:To alleviate the torque reduction generated in a motor at the time of stalling by superposing phase output current references of cycloconverter with triple frequency current reference. CONSTITUTION:A triple frequency current reference generator 20 calculates a current reference i3' having triple frequency of the output frequency of 3-phase cycloconverter 13 from a torque current command value iT', a magnetization current set value iM', a pole position angle lambda and an internal phase difference angle delta. Phase output current reference generators 21 calculate phase output current references iU', iV', iW' of 3-phase cycloconverters 13 from 3-phase winding current references iR', iS', iT' of a synchronous motor 14 and triple frequency current reference i3' of the output of a triple frequency current reference generator 20. Thus, when a synchronous motor stalls, a current limiting value for limiting a current concentration to a specific phase can be enhanced, and a torque reduction generated at the time of a stall can be alleviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention particularly relates to a control device for a cycloconverter that is most suitable for driving a synchronous motor.

[Conventional technology]

Figure 5 shows, for example, the publication rOH published in April 1981.
This is a block configuration diagram of a conventional synchronous machine vector control system shown in the paper "AC variable speed drive using vector control cycloconverter" published on page 37 of "M". In the figure, 1 is a speed setter, 2 is a 3 is a speed regulator, which calculates a torque command value Te'' based on the deviation between the set speed N1 and the actual speed N of the synchronous motor 14. 3 is a magnetic flux command calculator, which has the pattern shown in FIG. Magnetic flux command value φ1
give. 4 is a magnetic flux regulator, excitation current command value i,
5 is a magnetic flux calculator, which calculates the magnetic flux φ, field current if, internal phase difference angle cos δ, and sin δ. 6 is a divider, which calculates the torque set value Te” by the magnetic flux φ 7 is a vector rotator, and the torque current command value if, which is a DC amount, is created by dividing by
* and magnetizing current setting value iM*, two-phase AC current iα",
8 is a vector rotator, and a magnetic pole position signal cosλ is obtained.

sinλ and internal phase difference angle signal cos a , sin
The magnetic flux direction signals cosφ and sinφ are calculated from J. 9 is an operational amplifier), which is a two-phase/three-phase converter that converts two-phase alternating current iα1. The three-phase AC current command value jB"*5B"t'T" is obtained from iβ'. 10 is the armature current regulator, 11 is the gate control device of the cycloconverter, 12 is the 3-phase AC power supply, and 13 is the 3-phase Cycloconverter, 14 is a synchronous motor, 15 is a synchronous motor 140 rotor position detector, 16 is a speed generator that detects the rotor speed of the synchronous motor 140, 17 is a field current regulator, 18 is a gate control of the field control device The device 19 is a field control device as a phase control rectifier.

FIG. 6 shows a pattern of the magnetic flux command value φ" created by the magnetic flux command calculator 3, and the magnetic flux of the synchronous motor 14 is controlled according to this pattern. That is, the speed N of the synchronous motor 14 is set to the base speed NBA8B. While the magnetic flux command value φ9 is within the range of -N BA8B, the magnetic flux command value φ9 is maintained at a constant value φBASH, and when it is outside this range, the magnetic flux φ is weakened so that the product of the speed N and the magnetic flux φ becomes constant. Generated torque Te
is proportional to (φ*×if*), so constant torque current i
The relationship between speed N and torque Te when τO flows is as shown in FIG.

[Problem to be solved by the invention]

Since the conventional cycloconverter control device is configured as described above, when the synchronous motor 14 generates torque in a stalled state (rotation stopped state), the output current of the cycloconverter 13 becomes direct current, so the current flows concentratedly in a specific phase, and a peak current of the alternating current may continuously flow through the switching element of the specific phase. Since the current capacity of the cycloconverter 13 is normally selected based on the effective value of the alternating current, if the above-mentioned peak current flows continuously during overload, it will lead to overcurrent destruction of the switching elements, so the cycloconverter The overload rating of the converter 13 must be reduced at the time of a stall, and as a result, there is a problem in that the motor generated torque Te decreases at the time of the stall, as shown in FIG.

This invention was made in order to improve the above problems, and without increasing the current capacity of the cycloconverter,
An object of the present invention is to provide a control device for a cycloconverter that can increase the amount of overload torque generated when a synchronous motor stalls.

[Problem t - Means for Solving] The cycloconverter control i# device according to the present invention includes a triple frequency current reference generation circuit that generates a triple frequency current reference of the three-phase alternating current command value frequency, and a It has an output current reference generation circuit for each phase that adds the triple frequency current reference to the phase output current reference, and controls the torque and magnetic flux of a three-phase synchronous motor whose stator windings are triangularly connected. .

[For production]

In the cycloconverter control device of the present invention, the peak value of current in each phase of the cycloconverter output is reduced by the superimposition of the triple frequency current reference, thereby limiting current concentration to a specific phase when the synchronous motor stalls. The current limit value can be increased, and the reduction in torque generated during stalling can be alleviated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing one embodiment of the present invention.
In the figure, the same or equivalent components as in FIG. 5 are given the same reference numerals, and redundant explanation will be omitted. In Figure 1, 2
0 is a triple frequency current reference generation circuit that generates a current reference 18'' with a frequency triple the output frequency of the three-phase cycloconverter 13, and this is based on torque current command value if * magnetizing current set value jM'', magnetic pole position angle λ and internal phase difference angle a to calculate triple frequency current reference 58*. Reference numeral 21 denotes a reference generation circuit for each phase output current of the cycloconverter 13, which generates a reference current for each three-phase winding of the synchronous motor 14 jB"y i
ll”e iT* and the above triple frequency current reference generation [1
Triple frequency current standard i8*yoshi3 which is how to get i20
Each phase output current reference 'u' of phase cycloconverter 13
Calculate pW*iVO.

As shown in Fig. 2, the stator winding of the synchronous motor to be controlled is a three-phase triangular connection, so if the current direction of each phase is as shown in Fig. 2, the triple frequency current reference i3 " Cycloconverter when not adding , < -ta output current reference for each phase'
uo" s jvO" e jwo" becomes (1 formula).

At this time, It is.

Here, the cycloconverter each phase output current reference iuo"
Add triple frequency current reference 18* to t jvo" e 1vro" to create new output current reference for each phase iu" * "V
"e 'W" is synthesized. That is, the current reference is synthesized using (Equation 3).

At this time, it can be seen that even if the triple frequency current reference 18* is added, it has no effect on the stator winding current of the synchronous motor.

FIG. 3 shows how the peak value of each phase output current reference 'uO'*iVO'e'WO' is reduced when the triple frequency reference 18* is added.

Then, I u 'uo + 18*= Ip
'cos θ+s Ip c's 3θ (Equation 6), and the current reference peak value is reduced by about io%.

Note that the calculation formula for the triple frequency current reference 18* is derived as follows.

(Formula 8) %Formula% (Formula 9) (Formula 10) However, L, (11K) When constant tear K = 1/6, i
The peak value of uo''+- is the minimum.

(3) "jr" is the torque current command value, iM* is the magnetizing current setting value, λ is the magnetic pole angle, and δ is the internal phase difference angle.

Figure 4 shows the reduced hot water load torque when the synchronous motor stalls. Assuming that peak upstream current continues to flow in one phase when the motor is stalled, the overcurrent limit needs to be set to overload %/a.

Now, assuming an overload of 225%, 225%/ff'=
, 159%. According to the present invention, by superimposing the triple frequency current reference on the current reference for each phase of the cycloconverter output, the peak value of the phase current can be reduced by q times, so the overcurrent limit in this case is calculated as overload %/torque at stalling. The reduction is approximately 1
0% relaxation.

〔Effect of the invention〕

As described above, according to the present invention, the control device for the cycloconverter is configured to superimpose the triple frequency current reference on the output current reference for each phase of the cycloconverter, so that when the synchronous motor stalls, the current to a specific phase is reduced. The current limit value that limits concentration can be increased, and the reduction in torque generated by the motor at the time of stalling can be alleviated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a cycloconverter control device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the cycloconverter output current and the current direction of the synchronous motor,
Fig. 3 is a current reference waveform diagram of each phase of the cycloconverter, Fig. 4 is a characteristic diagram showing reduced overload torque when the synchronous motor stalls, Fig. 5 is a block diagram showing a conventional cycloconverter control device, Fig. 6 The figure is an input/output characteristic diagram of the magnetic flux command device, FIG. 7 is a speed-torque characteristic diagram, and FIG. 8 is a characteristic diagram showing the relationship between speed and overload torque. In the figure, 13 is a three-phase cycloconverter, 14 is a synchronous motor, 19 is a phase-controlled rectifier (thyristor), and 20
2 is a triple frequency current reference generation circuit, and 21 is an output current reference generation circuit for each phase. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Patent Applicant: Mitsubishi Electric Corporation" i, -1 Agent: Patent Attorney 1) Hiroshi Sawa 1991";

Claims (1)

[Claims] A synchronous motor whose stator winding is three-phase triangularly connected; a three-phase cycloconverter that supplies power to the stator winding of this synchronous motor; and a phase control rectifier that supplies power to an excitation winding of a rotor of the synchronous motor. A control device for a cycloconverter that controls the torque and magnetic flux of the synchronous motor by the three-phase cycloconverter and the phase-controlled rectifier, the cycloconverter generating a current reference with a frequency three times the output frequency of the three-phase cycloconverter; A control device for a cycloconverter, comprising: a frequency current reference generation circuit; and a respective phase output current reference generation circuit that adds the triple frequency current reference to each phase output current reference of the three-phase cycloconverter.