JPS61177167A - Reactive power compensation type polyphase cycloconverter - Google Patents

Abstract

PURPOSE:To reduce a reactive power by connecting a plurality of sets of unit cycloconverters connected in anti-parallel with separately-excited converters and self-excited converters, and cancelling the delay current of the separately- excited converter with the leading phase current flowed to the self-excited converter. CONSTITUTION:Unit cycloconverters in which separately-excited converters 11-13 and self-excited converters 41-43 are connected in anti-parallel are connected with transformers 51-53 of the respective phases to form a polyphase cycloconverter. A control angle is regulated to flow currents of leading phase to the converters 41-43. The converters 11-13 are operated in phase for remov ing the delay currents from the power source in principle. The leading phases of the self-excited converters are controlled by a CPU, not shown, to cancel the delay current of the separately-excited converters. Thus, the reactive cur rents of the combined powers can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a microconverter that is configured by combining a plurality of self-excited converters and separately excited converters, and has a reactive power compensated polyphase output that reduces the reactive current of a power supply. .

[Conventional technology]

FIG. 11!3 is a configuration diagram showing an example of a conventional low reactive power type three-phase cycloconverter. In the same figure, 11 to 1
3.21~23 are separately excited converters, 31~33.41~
43 is a self-excited converter, 51 to 53 are transformers, and 6 is a load.

A CYC4 converter that obtains a desired variable voltage and variable frequency by cutting out the power supply voltage at an appropriate phase is constructed by connecting ordinary separately excited converters in antiparallel using, for example, thyristors, but the principle behind separately excited converters is First, it is known that the power factor of the power source is low because a delayed phase reactive current (power) is drawn from the power source when obtaining variable voltage.

In order to compensate for this drawback, as shown in FIG.
, 23) Self-extinguishing controllable electric valve (GTO)
A unit cycloconverter I is a controllable electric valve whose arc is extinguished by auxiliary means such as a thyristor, etc.) or a forced commutation circuit.
[(31, 41°32, 42.33.43), and this cycloconverter ■ operates under the same load conditions as the above cycloconverter I for the fundamental wave components of the output voltage and output current. The control angle is determined so that a leading phase current flows into the power supply, and the current is combined to cancel out the reactive current of the power supply. and,
In order to make the load conditions of the cycloconverters I and II the same, this can be achieved by connecting these cycloconverters in series or in parallel to supply power to one load.

[Problems to be solved by the invention] However, in such a configuration, the number of rectifying elements used increases, and its application is limited to large-capacity machines in particular, and the main circuit configuration becomes complicated. There was a problem that the main circuit and control device were expensive.

[Means for solving problems]

A polyphase cycloconverter is constructed by combining several unit cycloconverters in which a separately excited converter and a self-excited converter are connected in antiparallel or cross-wired. Adjust.

[Effect]

A cycloconverter is a system in which, for example, two sets of rectifiers are connected in antiparallel, and the rectifiers are switched according to the polarity of the load current.
Supply the desired AC power to the load.

In the following explanation, the direction in which the load current flows is assumed to be positive polarity, the rectifier that conducts current at this time is referred to as a stone-side converter, and the direction in which the load current flows opposite to the above is assumed to be reverse polarity, and the rectifier that conducts current at this time is referred to as a reverse side converter. I'll call you.

Now, in a multi-phase output cycloconverter, for example, a three-phase output cycloconverter, for example, the stone side converter is configured with a separately excited converter, and the reverse side converter is configured with a self-excited converter, and the control angle of the separately excited converter is, in principle, based on the lagging current from the power supply. The self-excited converter operates in a phase that takes the current leading from the power supply. At this time, since the current that flows into the load from the phase with the load must flow out from the phase with the load, the converter group in which M@humperter is conducting at all times and the converter on the opposite side are conducting Therefore, the reactive current component of the lagging phase of the isolated side, that is, the separately excited converter, and the reactive current component of the leading phase of the opposite side, that is, the self-excited converter, cancel each other out, significantly reducing the reactive current of the power supply. be able to. Looking at it from a different perspective, the reactive current flowing through each comparator is exchanged between the converters of each phase.

Next, we will discuss the desirable control angle relationship between separately excited converters and self-excited converters. Now, the target values of the control angle that change from moment to moment based on the output of AC voltage are expressed as αP and αN for separately excited converters and self-excited converters, respectively.
shall be. The output voltage should be the same regardless of which of the two converters is conducting, the connection directions of both converters should be opposite to each other, and the output voltage should be commutated within a small range. Cosine of angle (ω3)
Considering that the control angles αP and αN are proportional to , it is desirable that the control angles αP and αN be controlled so that the following relationship holds true.

cos ap --cos aH-'' (1) Therefore, the relationship between αP and αN is αN!αP−π 00″′. ′″
(2) or αN-π-αP...
... (3) becomes. In this case, αP is in the range from zero to π, and αN must be operated in the range from -π to zero because it takes current from the power supply, so (3)
The equation does not match the purpose of the present invention, and in the end, the control is performed so that the relational equation (2) holds true.

〔Example〕

#! FIG. 1 is a circuit diagram of a three-phase output cycloconverter according to an embodiment of the present invention. In the same figure, 11 to 13
is a separately excited converter, 41 to 43 are self-excited converters, 51
53 is a transformer, and 6 is a load. In other words, the separately excited converters 11 to 13 and the self-excited converters 41 to 43 are connected in antiparallel to each other, and the number of units is equal to the number of phases. Note that the figure shows a three-phase example, and the self-excited converter is composed of a GTO thyristor that can self-extinguish. Further, instead of connecting the separately excited converter and the self-excited converter in antiparallel, a cross connection can be used.

FIG. 1A is a block diagram showing a control device for one phase of the three-phase cycloconverter shown in FIG. In the same figure, 1
Is it electric? ItH moderator (AC switch), 2 and 4 are arithmetic units, 3 is a comparator, 71 is a firing angle adjuster for the separately excited fan park 11, 7
2 is a firing angle adjuster for the self-excited converter 41.

The operation of FIG. 1A will be explained.

The current target value l and the current actual value i are input to the current regulator IK, and the current regulator 1 operates so that there is no deviation between the command value l and the actual value i. The output of the current regulator 1 is used as a target voltage value for flowing a desired current. The voltage target value V is led to the arithmetic unit 2, and its output becomes, for example, a target value αP of the control angle of the layer side converter (separately excited converter) 110.

This target value αP is guided to the firing angle regulator 31. The firing angle regulator 31 is a phase shifter that adjusts the pulse generation point of the converter 11 by an angle proportional to αpK in synchronization with the power supply voltage. The separately excited converter 11 at the control angle αP1
generates an ignition pulse.

In the calculator 4, a control angle target value αN4'' of the reverse side converter (self-excited converter) is determined according to (2) 2 from αP, and an ignition pulse is given to the self-excited converter 41 at the desired control angle. The firing angle adjusters 71 and 72 have the same operating principle, but the adjuster 71 operates within a control angle range of 0 to 180 degrees, while the ignition angle adjuster 72 operates within a range of -180 degrees to zero. do.

The comparator 3 is a signal that enables output from at least one of the regulators 71 and 72, and one of the regulators 71 and 72 is selected depending on the polarity of the current command value.

Note that in FIG. 1, it is naturally possible to replace the connection positions of the separately excited converter and the self-excited converter, and the operation and effect of the present invention will not change even if they are not limited to anti-parallel connection but also cross connection. .

In addition, when multiple DC motors with the same load, for example two DC motors in particular, are mechanically directly connected, for example, a layer-side converter of a converter group that supplies power to one DC motor may be externally excited. In the converter, the reverse side converter is configured with a self-excited converter, the layer side converter of the converter group that supplies power to one other DC motor is configured with the self-excited converter, and the reverse side converter is configured with the separately excited converter, and the present invention By adjusting the control angle of each converter as shown, the power factor of the power source can be made approximately 1''. Figure 2B shows a three-phase output cycloconverter configured only with a conventional separately excited converter. An example of the input IIcIc type 1Is12e13 of one phase of each converter and the input current waveform i4 of one phase of the combined power supply when three-phase symmetrical sine wave voltage and sine wave current are output. Figure 2A shows the current waveform at the same location under the same load conditions as Figure 2B according to the present invention.As is clear from both figures, the present invention cancels out the reactive currents between each converter, and as a result, the power supply A fundamental wave power factor of approximately 11'' is achieved. Furthermore, ixa iz e is e i4a
For example, it is the current waveform of each part shown in FIG.

〔Effect of the invention〕

According to the present invention, in a multi-phase output cycloconverter, a separately excited converter and a self-excited converter are connected in anti-parallel or cross-connected to form one cycloconverter, and the mutual control angle is basically (2 By adjusting K so that the relational expression ( ) is maintained, an advantage is brought about that the reactive current of the combined power source can be reduced without increasing the number of basic rectifying elements.

[Brief explanation of drawings]

No. 111A is a configuration IN showing a multi-phase output cycloconverter control device according to the present invention, and No. 1 AIm is a block diagram showing a multi-phase output cycloconverter control device according to the present invention.
Figure @2A is a waveform diagram showing the power supply current waveform according to the present invention, #
! FIG. 2B is a waveform diagram showing a power supply current waveform according to a conventional example, and FIG. 3 is a configuration diagram showing a conventional example of a three-phase output cycloconverter main circuit. Code explanation 11-13. 21-23...Separately excited converter,
31-33t 41-43...Self-excited converter, 51-53...Transformer, 6...Load, 1...Current regulator (ACR) ), 2.4...
... Arithmetic unit, 3... Comparator, 71.72.
...Ignition angle adjuster. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Figure 1

Claims (1)

[Claims] 1) A multi-phase cycloconverter is constructed by combining a plurality of unit cycloconverters formed by antiparallel connection or cross connection of separately excited converters and self-excited converters, and the self-excited converter has an ineffective leading phase. Reactive power that is characterized by reducing the reactive current (reactive power) of the power supply by adjusting its control angle so that current flows and canceling out the reactive current of the delayed phase that flows to the separately excited converter of other phases. Compensated polyphase cycloconverter. 2) In the reactive power compensating polyphase cycloconverter according to claim 1, the time course of the control angles of the separately excited converter and the self-excited converter are each expressed as α_
A reactive power compensation type cycloconverter characterized in that each control angle is adjusted so that the following relationship holds, where P and α_N, α_N = α_P - 180 degrees (0≦α_P<180 degrees). .