JPH0669294B2 - Reactive power compensation type power converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a reactive power compensation type power conversion device that reduces the reactive current of a power supply by combining a self-excited rectifier and a separately excited rectifier.

[Prior art]

FIG. 2 is a block diagram showing an example of a conventional low reactive power type power converter. In the figure, 11 and 12 are controllable separately excited rectifiers, 21 and 22 are self-excited rectifiers, 3 is a transformer, and 4 is a load.

Generally, as a static power converter for supplying a reversible direct current to a load, a controllable electric valve that cannot self-extinguish, such as an ordinary thyristor, is bridge-connected to form a rectifier. Are often connected in parallel (hereinafter referred to as antiparallel connection) to form a reversible separately excited rectifier. At this time, the separately-excited rectifier with a variable voltage output (hereinafter, simply referred to as controllable) takes a reactive current in a delayed phase from the power source due to its principle, and particularly when the output voltage is lowered, the power source power factor is greatly reduced. It is known. Further, when changing the polarity of the output current, in order to completely extinguish the thyristor that has been ignited up to now, at least a predetermined time determined as the turn-off time of the thyristor has elapsed after the output current became zero. Afterwards, the desired thyristor of the rectifier, which is connected in antiparallel with the rectifier that was previously flowing, must be fired. The dead time when changing the polarity of the load current is generally called a switching dead time, which is an operation delay with respect to current control, which is not preferable.

In order to make up for the above two drawbacks, the former one is extinguished by a self-extinguishing controllable electric valve (or a commutation circuit such as a forced commutation circuit) consisting of, for example, a GTO thyristor, as shown in FIG. A reversible self-excited rectifier 21,22 is configured by a controllable electric valve that is arced), and the reversible self-excited rectifier 21,22 and the reversible separately excited rectifier 11,12 are connected in series or in parallel. In the self-excited rectifiers 21 and 22, the control angle is determined so that the reactive current of the leading phase flows to the power supply, and the reactive current of the separately excited rectifier and the self-excited rectifier is combined to reduce the reactive current of the power supply. The method is adopted.

[Problems to be Solved by the Invention]

However, in the configuration as shown in FIG. 2, the latter drawback, that is, the switching dead time of the reversible separately-excited rectifier exists, so that another solution, for example, cross-connecting two separately-excited rectifiers and circulating current between both rectifiers is used. A method is required to eliminate the dead time of switching by causing the current to flow, which causes various problems such as an increase in the capacity of the converter, an increase in the number of main circuit components, and a generation of a reactive current of a delayed phase due to a circulating current.

In addition, the switching dead time of the thyristor rectifier connected in anti-parallel does not cause a power supply short circuit between the thyristor that has been ignited up to now and the thyristor that is newly ignited to switch the polarity of the load current. Is what you need. In FIG. 2, for example, when the output voltage is near zero, that is, when the control angle is near 90 degrees, when switching the rectifier to be passed through to switch the current polarity from 11 to 12, for example, thyristors U ₁ and Z ₁ Assuming that the thyristors are ignited, the thyristors that are ignited after the switching are U ₂ and Z ₂ , because the control angles are both near 90 degrees.
If there is at least a dead time for switching the turn-off time of the thyristor, a power supply short circuit will occur through U ₁ and Z ₁ , and this relationship is the same for thyristors Z ₁ and U ₂ .

An object of the present invention is to solve the above-mentioned problems of the prior art, to provide a reactive power compensating type power conversion device capable of eliminating a switching dead time at the time of switching a flowing rectifier and reducing a reactive current of a power supply. To do.

[Means for Solving the Problems]

In the reactive power compensation type power converter according to the present invention,
Two separately-excited rectifiers and self-excited rectifiers are connected in parallel with each other with their polarities reversed (reverse parallel connection), and are connected in series with their polarities reversed (hereinafter referred to as anti-series connection).
The control angle of the self-excited rectifier is adjusted by the ignition angle adjuster so that the reactive current of the phase flows to the power source.

In addition, two unit rectifiers in which the separately excited rectifier and the self-excited rectifier are connected in anti-parallel are connected in anti-parallel, and the control angle is set so that the reactive current of the phase proceeds to the power source and flows to the self-excited rectifier. It was decided to adjust with an arc angle adjuster.

[Action]

The power factor is set to "1" by setting the control angles of the separately excited rectifier and the self-excited rectifier on the flowing side to have opposite polarities.
And when switching the rectifier that flows,
The control angles of the self-excited and separately-excited rectifiers connected in anti-parallel are 18
The dead time for switching is eliminated by adjusting the ignition angle adjuster so that the phase difference is 0 degree.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention.

One of the features of the present invention is that one of the rectifiers connected in anti-parallel is a controllable separately excited rectifier such as a thyristor rectifier, and the other is an auxiliary means such as a controllable electric valve capable of self-extinguishing or a forced commutation circuit. A self-excited rectifier consisting of a controllable electric valve that can extinguish an arc. At this time, for any desired value of the output voltage, the separately-excited rectifier or the self-excited rectifier is ignited according to the polarity of the load current, but the control angle of the separately-excited rectifier and the self-excited rectifier is always around 180 degrees. The control angle is determined so that the phase difference is maintained. Since the separately-excited rectifier and the self-excited rectifier are connected in anti-parallel, when the phase difference between the two control angles is 180 degrees, the output voltage is the same regardless of which one is conducting. In this case, even if a thyristor rectifier of a type that requires a reverse voltage period defined as a turn-off time for extinguishing the arc is connected to one side connected in anti-parallel, the switching dead time of the rectifier can be made zero. Is. The principle will be described later, and the method for reducing the reactive current of the power supply according to the present invention will be described first.

From the conclusion, the main circuit of the power converter according to the present invention further includes a reversible rectifier (unit rectifier) in which the separately-excited rectifier and the self-excited rectifier are connected in antiparallel as described above, and further connected in antiseries or antiparallel. Configure.

Fig. 1 shows an example of connection in the case of reverse series connection. 11 and 12 are controllable separately excited rectifiers, 21 and 22 are self excited rectifiers, 11 and 21
It flows through the combination of, or the combination of 12 and 22.

In FIG. 1, the separately-excited rectifier 11 and the self-excited rectifier 22 constitute one unit rectifier, and the separately-excited rectifier 12 and the self-excited rectifier 21 are provided.
And constitute another unit rectifier. At this time,
The control angles of the self-excited rectifiers 21 and 22 are adjusted so that phase reactive current flows to the power source. Therefore, for example, the reactive current (power) of the delayed phase due to 11 and the reactive current (power) of the leading phase due to 21 are canceled out, and the reactive current (power) of the combined power source can be reduced. Since the reactive current of the power supply by the rectifier is proportional to the product of the output current and the sine of the control angle of the rectifier, it is desirable to control as follows. That is, for example, if the control angle of 11 is α, the control angle of 21 is −α. At this time, the average output voltage values of 11 and 21 are the same, the reactive currents of both rectifiers are canceled for the power source, and the fundamental wave power factor of the power source becomes "1". If the polarity of the output current is reversed,
Flow through 12 and 22, and the control angle of 22 is (α-180
And the control angle of 12 is (180 degrees-α).

Next, the controllable reversible rectifier of the present invention can eliminate the switching dead time of the rectifier, and the principle thereof will be described below.

Now, assume that the separately excited rectifier 11 is flowing, the controllable electric valve, for example, the thyristors U ₁ and Z ₁ are ignited, and at this time, immediately before the polarity of the load current is reversed. At this time,
Keeping the control angles of 11 and 22 at a phase difference of 180 degrees means
A controllable electric valve, such as a gate turn-off (GTO) thyristor X ₂ , W ₂ capable of self-extinguishing, is connected in antiparallel to each of the thyristors U ₁ and Z ₁ which have always been ignited. At this time, of course, the power supply short circuit does not occur,
Due to the conduction of X ₂ and W ₂ , U ₁ and Z ₁ have X ₂ and W ₂
A reverse voltage is applied by the armpit voltage, and further, Y ₂ which is next ignited and U ₂ which is then ignited are applied with reverse voltages by the power supply voltage to U ₁ and Z ₁ , respectively. , U ₁ , Z ₁ are safely extinguished. In the wiring example of FIG. 2, switching the rectifiers connected in antiparallel as described above means that at least one of the rectifiers has a control angle of -180.
Must be in the range 0 to 0 degrees, which is not feasible because the commutation condition of the separately excited rectifier is not satisfied.

Also, when multiple controllable reversible rectifiers operating under almost the same load conditions are required, the controllable separately excited rectifiers and self-excited rectifiers are connected in anti-parallel, and the reversible rectifiers and self-excited separately excited rectifiers flow. It is possible to reduce the reactive current of the combined power source by configuring so that the number of reversible rectifiers through which the rectifiers flow is almost the same.

Also, in a multi-phase cycloconverter that obtains another variable voltage and variable frequency from a commercial power source by changing the control angle with a reversible rectifier from moment to moment, as a reversible rectifier, a controllable separately excited rectifier and a self-excited rectifier are connected in antiparallel. If the controllable reversible rectifier is used, the reactive current is canceled between the rectifiers, and the reactive current of the combined power source can be reduced. Particularly in a cycloconverter, when the output frequency is increased, the switching dead time of the rectifier becomes an important problem from the viewpoint of control performance. However, according to the present invention, the switching dead time can be made zero, so that controllability is improved and It can be said that there is great progress in expanding the scope of application.

Next, a method of controlling the control angle will be described with reference to FIG. 1A. Note that FIG. 1A is a block diagram showing an example of a control unit of the reactive power compensation type power converter according to the present invention. In the figure, 5 is a current regulator (ACR), 6 is a calculator, and 7
Is an inverter, 8 and 9 are ignition angle adjusters, 10 is a comparator, and others are the same as those in FIG.

The current regulator 5 performs adjustment calculation so that there is no deviation between the target current value I ^* and the actual current value I, and its output becomes the target value of the output voltage. The computing unit 6 has the following target voltage value:
For example, the control angle α of the separately excited rectifier 11 is given. The firing angle adjuster 8 gives a gate signal to 11 appropriate thyristors in consideration of the phase of the power supply voltage. Further, the control angle of the self-excited rectifier 22 is 180 degrees with respect to the control angle of 11, so that X ₂ is fired at the timing when U ₁ is fired in FIG. 1, for example. To do. In the case of FIG. 1A, whether U ₁ or X _{2 is} to be ignited is determined by determining the polarity of the current target value I ^* with the comparator 10, and the desired electrical value is determined according to the result. Ignite the valve.

Further, when the actual current value becomes equal to or less than the predetermined value, the electric valve for flowing the current in the opposite direction may be ignited. This is because, according to the present invention, even if the rectifiers connected in anti-parallel are simultaneously fired, a power supply short circuit does not occur. The inverter 7 ignites, for example, the self-excited rectifier 21 at a phase (−α) in which the polarity of the control angle of the separately excited rectifier 11 is inverted,
Gives that control angle. Similarly, the ignition angle adjuster 9 is a comparator.
The output of 10 gives the firing signal of rectifier 21 or 12. In addition, the rectifier is at least always fired in the combination of 11 and 21 or in the combination of 22 and 12, and the self-excited rectifier
It goes without saying that, for 21 and 22, when the new electrovalve fires, it may be necessary in some cases to output an extinguishing signal to the electrovalve that was previously conducting.

FIG. 1B shows a schematic configuration diagram of a reactive power converter in which two unit rectifiers are connected in antiparallel. In the figure, separately excited rectifier 11
The self-excited rectifier 22 constitutes one unit rectifier, and the other-excited rectifier 12 and the self-excited rectifier 21 constitute another unit rectifier.

The connection relationship between the separately excited rectifiers 11 and 12, the self-excited rectifiers 21 and 22 and the ignition angle adjusters 8 and 9 of the control unit is the same as that in FIG. 1A. Incidentally, the coil L in FIG. 1B is provided to balance the current between the two unit rectifiers.

〔The invention's effect〕

According to the present invention, a controllable separately excited rectifier and a self-excited rectifier are connected in anti-parallel to form a controllable reversible rectifier, and when the rectifiers that flow are switched, the phase difference between the control angles of the respective rectifiers is 180.
The degree provides the advantage of eliminating switching dead time. In addition, the controllable reversible rectifier is further connected in anti-series or anti-parallel, and the control angle of the self-excited rectifier is basically the same as the value obtained by inverting the control angle of the other-excited rectifier that is also flowing at that time. By doing so, it is possible to cancel the reactive current of the power supply due to both rectifiers and to obtain the effect that the fundamental wave power factor of the power supply can be set to "1".

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main circuit of a reactive power compensation type power conversion device according to the present invention, and FIG. 1A is a block diagram showing a control unit of an anti-series connection type reactive power compensation type power conversion device according to the present invention. FIG. 1B is a block diagram showing a control section of an anti-parallel connection type reactive power compensation type power converter according to the present invention, and FIG. 2 is a configuration diagram showing a conventional example of a low reactive power type power converter. Code description 11,12 …… Excited rectifier, 21,22 …… Self-excited rectifier, 3 …… Transformer, 4 …… Load, 5 …… Current regulator (ACR), 6 ……
Computing unit, 7 ... Inverter, 8, 9 ... Firing angle adjuster, 10 ...
Comparator.

Claims (4)

[Claims] 1. A separately excited rectifier (11, 12) and a self-excited rectifier (21, 2)
2) and two unit rectifiers (11,22: 21,12) that are connected in parallel with their polarities reversed, and are connected in series with their polarities reversed, and the self-excited rectifier (21, For 22), a reactive power compensating type power converter characterized in that its control angle is adjusted by a firing angle adjuster (8, 9) so that a reactive current of a phase flows to a power source. 2. A separately excited rectifier (11,12) and a self-excited rectifier (21,2).
2) and two unit rectifiers (11,22: 21,12) that are connected in parallel with their polarities reversed, and are connected in parallel with their polarities reversed, and the self-commutated rectifier (21, For 22), a reactive power compensating type power converter characterized in that its control angle is adjusted by a firing angle adjuster (8, 9) so that a reactive current of a phase flows to a power source. 3. The firing angle adjuster (8, 9) adjusts the control angles of the separately-excited rectifier and the self-excited rectifier on the flowing side so that the respective control angles have opposite polarities. The reactive power compensation type power conversion device according to claim 1 or 2, characterized in that. 4. The ignition angle adjuster (8, 9) has a control angle of 180 ° between self-excited and separately-excited rectifiers connected in parallel when switching the rectifier on the flowing side according to the polarity of the load current. 3. The reactive power compensation type power converter according to claim 1 or 2, wherein each control angle is adjusted so as to have a phase difference of degrees.