JPH0150177B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic voltage regulator, and is suitable for use in regulating alternating current voltage of a power system.

When a load is connected to a system where AC voltage fluctuates, an automatic voltage regulator is generally installed to keep the voltage supplied to the load within a certain voltage range. composition was used. In Figure 1, 1U,
1V, 1W indicates a 3-phase input terminal, 2U, 2V,
2W indicates the corresponding phase output terminal. Also 3U, 3
V, 3W are adjustment transformers, input terminals 1U, 1V, 1
The phase-to-phase voltage is taken out from the secondary winding b by connecting the primary winding a connected to W in a star shape. The secondary windings b of the regulating transformers 3U, 3V, 3W are input to switching circuits 4U, 4V, 4W. The switching circuits 4U, 4V, and 4W are constructed by bridge-connecting thyristor switches 5, 6, 7, and 8 each having a pair of thyristors e and f connected in antiparallel, as shown in FIG. 2, for example. The output of the switching circuit 4U, 4V, 4W is the secondary of the series transformer 9U, 9V, 9W connected in series between the input terminal 1U, 1V, 1W and the corresponding output terminal 2U, 2V, 2W. Connected to winding h.

Next, the operation of the configuration shown in FIG. 1 will be explained. Although the automatic voltage regulator shown in FIG. 1 is for three phases, in order to simplify the explanation of the operation, for example, a U-phase circuit will be explained as shown in FIG.

The operation of the automatic voltage regulator shown in FIG. 3 can be explained as equivalent to the tap changer 11 shown in FIG. That is, first, when thyristor switches 7 and 8 in FIG. 3 are turned on and thyristor switches 5 and 6 are turned off, the secondary side of series transformer 9U is short-circuited by thyristor switches 7 and 8, and the No change in voltage occurs in the winding g. This is done by the tap changer 11 shown in Figure 4.
This is equivalent to being in the T ₀ state. Next, when thyristor switches 7 and 6 are turned on and thyristor switches 5 and 8 are turned off, the regulating transformer 3
The secondary voltage V ₃ of U is applied to the series transformer 9U in a direction that raises the output voltage V ₂ . This is equivalent to the tap changer 11 in FIG. 4 being in the tap _T1 state. Conversely, thyristor switches 5 and 8
is turned on and thyristor switches 7 and 6 are turned off, the secondary voltage V ₃ of the regulating transformer 3U is applied to the series transformer 9U in the direction of lowering the output voltage V ₂ , which is applied to the series transformer 9U as shown in FIG. 11 is tapped
This is equivalent to being in the T ₂ state.

In this way, according to the configuration shown in FIG. 3, the switching circuit 4U
By turning on and off the thyristor switches 5 to 8, it is possible to obtain an output voltage equivalent to raising or lowering the taps of the tap changer ₁₁ shown in FIG. By raising the tap and conversely lowering the tap when the input voltage _V1 increases, fluctuations in the output voltage _V2 can be suppressed within a certain range.

The operation of the U-phase circuit in Figure 3 is the same for the other phase circuits, and the series transformer of each phase adjusts the three-phase voltage by raising or lowering the voltage in the direction of the phase voltage vector. Become.

In the conventional automatic voltage regulator described above, the voltage is adjusted using a voltage that is in phase with the phase voltage, and therefore, the following disadvantages occur for a single-phase load. That is, since a single-phase load is connected between three-phase lines, it is required to adjust the voltage between the lines to which the load is connected to be constant. For example, if a single-phase load is connected between UV phases, it is necessary to raise the UV phase-to-phase voltage when it drops. Conventional equipment only compensates for the phase voltage, so if you try to compensate for the UV phase-to-phase voltage,
It is necessary to adjust both the U-phase voltage and the V-phase voltage, and it is necessary to perform at least two tap switching operations. However, since this tap switching is performed sequentially for each phase in synchronization with the power supply voltage, a period of 120° is required for the tap switching of the U phase and V phase.
The drawback is that it lacks quick response.

Furthermore, as shown in the vector diagram of Fig. 5, when compensating for the UV phase-to-phase voltage drop ΔV _UV by the phase voltage,
It compensates ΔV _U in the U-phase voltage direction and ΔV _V in the V-phase voltage direction, but since there is a 30° phase difference between the phase voltage and line voltage, |ΔV _U |+ |ΔV _V |=2 /√3・|ΔV _UV | ………(1) Therefore, it is necessary to increase the phase voltage by 2/√3 times the line voltage to be compensated. As is clear from this, the conventional device has the disadvantage that it requires an extra compensation capacity of 2/√3 times and is uneconomical for single-phase loads.

The present invention has been made in order to eliminate the drawbacks of the conventional products as described above, and by using a voltage in phase with the line voltage as a compensation voltage, the line voltage can be efficiently adjusted in series between two of the three phases. It is an object of the present invention to provide a quick-response automatic voltage regulator by simultaneously applying voltage to the transformer so as to be able to compensate for the line voltage with just one tap change.

An embodiment of the present invention will be described below with reference to the drawings.
In Fig. 6, 23, 24, 25 are regulating transformers, and the line voltages V〓UV, _V〓VW , _V〓VW ,
V〓 _WU are respectively input. Adjustment transformer 23,2
The secondary windings 4 and 25 are switching circuits 26, 27, 2
8 respectively.

As the switching circuits 26, 27, 28, the thyristor bridge circuit described above with reference to FIG. 2 can be applied. The output of the first switching circuit 26 is connected to a series transformer 31 installed in the U phase and a series transformer 32 connected to the V phase. Also, the second switching circuit 27
The output of the series transformer 33 installed in the V phase and the W
and a series transformer 34 connected to the phase.
Further, the output of the third switching circuit 28 is connected to a series transformer 35 installed in the W phase and a series transformer 36 installed in the U phase.

Next, the operation of the configuration shown in FIG. 6 will be explained.
Secondary voltage of regulating transformer 23 connected between UV phases
When the series transformers 31 and 32 are excited using V= _2UV , the voltage drop is compensated by a vector as shown in FIG. Incidentally, V〓 _2UV is lifted by the series transformer 31, and -V〓 _2UV is lifted by the series transformer 32.

The compensation transformer 23 thus connected between the UV phases
This means that the voltage can be adjusted in the direction of the UV phase-to-phase voltage.

Similarly, by exciting the series transformers 33 and 34 from the secondary side of the regulating transformer 24 connected between the VW phases, the voltage can be adjusted in the VW inter-phase voltage direction, and the voltage of the regulating transformer 25 connected between the WU phases can be adjusted. By exciting the series transformers 35 and 36 from the secondary side, the voltage between the WU phases can be adjusted.

Therefore, for example, if a single-phase load is connected between output terminals 2U and 2V corresponding to the UV phase, the UV
By controlling only the inter-phase switching circuit 26, the UV inter-phase voltage can be compensated, and automatic voltage control with simple and quick response can be performed. Further, since the compensation voltage acts in the line voltage direction, efficient voltage compensation can be performed.

In the above embodiment, two series transformers are connected to each phase, but instead of this, one common core transformer may be used.
Alternatively, a series transformer having two windings on the excitation side and one winding on the main circuit side may be used.

Further, the switching circuit can be realized using a mechanical switch instead of the thyristor switching circuit.

As described above, according to the present invention, the series transformer is configured to increase the voltage in the line voltage direction.
It is possible to perform voltage compensation with a quick response and high efficiency for a single-phase load.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing a conventional automatic voltage regulator, Fig. 2 is a connection diagram showing its switching circuit, Fig. 3 is a connection diagram showing a U-phase equivalent circuit of the automatic voltage regulator in Fig. Fig. 4 is a connection diagram showing a tap switching circuit for explaining the operation of the automatic voltage regulator, Fig. 5 is a vector diagram showing a voltage compensation method using a conventional device, and Fig. 6 is an automatic voltage regulator according to the present invention. FIG. 7 is a vector diagram for explaining the voltage compensation method. 1U~1W...Input terminal, 2U~2W...Output terminal, 3U~3W...Adjusting transformer, 4U~4W...
...Switching circuit, 9U~9W...Series transformer, 5~8
...Thyristor switch, 10...Load, 23~
25...Adjusting transformer, 26-28...Switching circuit,
31-36...Series transformer.

Claims (1)

[Claims] 1 A three-phase regulating transformer whose primary winding receives each line voltage applied to the three-phase input terminal, and the magnitude of the output voltage of each regulating transformer connected to the output terminal of each of the above regulating transformers. A switching circuit for three phases that sends out a regulated voltage switching output according to the voltage, and a primary winding inserted between the input terminal and the corresponding output terminal, respectively, and a switching circuit for two phases of the switching circuit. and a series transformer for three phases each receiving a switching output of the three phases, and when the voltage arriving at the input terminal changes and a switching operation is performed by the switching circuit, the three-phase output terminal is connected to the three-phase output terminal. An automatic voltage regulator characterized in that a compensation voltage for a power source impedance drop voltage is simultaneously applied to an output.