JPS6336004B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic voltage regulator that includes a thyristor and supplies a stable alternating current voltage to a load.

[Conventional technology]

2. Description of the Related Art Conventionally, there has been an automatic voltage regulator shown in FIG. 1 that compensates for alternating current voltage fluctuations and supplies a stable alternating current voltage to a load. In the figure, an AC voltage V ₁ input via input terminals 1 and 2 is applied to the primary winding 3a of the regulating transformer 3, and is also applied to the load 5 via the primary winding 4a of the series transformer 4. be done. Between the secondary windings 3b of the regulating transformer 3, thyristor switches 6-1 to 6-4, each consisting of a pair of reversed thyristors connected in parallel, are bridge-connected, and their outputs are connected to the two of the series transformers 4. The voltage is applied to the next winding 4b. A bypass thyristor switch 7 having the same configuration as the thyristor switch 6-1 is connected to the secondary winding 4b. Thyristor
The switches 6-1 to 6-4 and 7 receive ignition signals from a control circuit (not shown).

Next, the operation will be explained. The control circuit operates the thyristor switches 6-1 and 6-4 according to the firing signal.
and 6-2 and 6-3 are used to selectively turn on and off the voltage _V3 of the secondary winding 3b of the regulating transformer 3. A selection is made as to whether to apply the voltage to the secondary winding 4b. In this way, the voltage fluctuation of the AC voltage V ₁ is compensated for by superimposing the compensation voltage of the voltage V ₃ having the same polarity or the opposite polarity with the AC voltage V ₁ from the series transformer 4 and applying it to the load 5. ing.

The overvoltage generated in the secondary winding 4b of the series transformer 4 causes the thyristor switches 6-1 to 6-6 to
For example, turn on thyristor switches 6-1 and 6-4 (tap +1
state) of the thyristor switches 6-2, 6-3
When switching on (tap-1 state), first turn on thyristor switch 7, then turn off thyristor switches 6-1 and 6-4,
It also performs switching control to turn on the thyristor switches 6-2 and 6-3 and turn off the thyristor switch 7.

[Problem that the invention seeks to solve]

Since the conventional automatic voltage regulator is configured as described above, there is a problem in that it requires a bypass thyristor switch to protect the thyristor switch for switching the polarity of the compensation voltage. Since these switching controls are redundant, there is a problem in that the response of the device is slow.

This invention was made in order to solve the above-mentioned problems, and it is possible to change the phase of the firing signal that controls the firing of the thyristor switch for switching the polarity of the compensation voltage by adjusting the commutation that occurs when switching It is an object of the present invention to provide an automatic voltage regulator that controls the current to be reduced, thereby omitting a bypass thyristor switch, and thereby improving the responsiveness of the device.

[Means for solving problems]

The automatic voltage regulator according to the first invention includes a control circuit that includes a detection circuit that detects a fluctuating voltage of an alternating current voltage, a comparison circuit that compares the fluctuating voltage with a predetermined reference voltage, and a zero cross point of a load voltage. It is composed of a pulse generation circuit that generates a timing signal with a constant advance phase, and a logic circuit that selectively outputs a firing signal for firing a thyritor based on the comparison result from the comparison circuit and the timing signal.

Further, the automatic voltage regulator according to the second invention includes a control circuit that includes a detection circuit that detects a fluctuating voltage of the AC voltage, a comparison circuit that compares the fluctuating voltage with a predetermined reference voltage, and a zero cross of the load voltage. Selecting and outputting a firing signal for firing the thyristor based on the comparison result of the first and second pulse generating circuits that generate timing signals at a certain leading phase different from the point, and the comparison circuit and the timing signal. It is composed of logic circuits.

Furthermore, the automatic voltage regulator according to the third invention includes a control circuit that includes a detection circuit that detects a fluctuating voltage of the AC voltage, a comparison circuit that compares the fluctuating voltage with a predetermined reference voltage, and a zero cross of the load voltage. first and second pulse generation circuits that generate timing signals at fixed leading phases that are different from each other; and a determination that determines whether the load is conductive or capacitive, based on the AC voltage and the current flowing through the load. a gate circuit that switches the output line of the timing signal based on the output signal of the discrimination circuit; and a point that fires the thyristor based on the comparison result of the comparison circuit and the timing signal inputted via the output line. It is constructed from a logic circuit that selectively outputs an arc signal.

[Effect]

The control circuit in the first invention compares the fluctuating voltage detected by the detection circuit with a reference voltage, and
An ignition signal for igniting the thyristor is selectively output based on the comparison result and a timing signal with a constant advance phase from the zero crossing point of the load voltage having the same phase as the compensation voltage.

In addition, the control circuit in the second invention compares the fluctuating voltage detected by the detection circuit with the reference voltage, and also generates a timing signal of a constant lead phase different from the zero cross point of the load voltage having the same phase as the compensation voltage. An ignition signal for igniting the thyristor is selectively output based on the comparison result.

Furthermore, the control circuit in the third invention compares the fluctuating voltage detected by the detection circuit with the reference voltage, and also sends timing signals of different constant lead phases to the load from the zero cross point of the load voltage having the same phase as the compensation voltage. It is switched by the output signal of a discrimination circuit that discriminates whether it is inductive or capacitive, and a firing signal for firing the thyristor is selectively output based on the comparison result and one of the timing signals switched by the discrimination circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3. FIG. 2 is a connection diagram of the main circuit according to the present invention, which has the same configuration as FIG. 1 except that the thyristor switch 7 is omitted. FIG. 3 shows a control circuit for generating firing signals for the thyristor switches 6-1 to 6-4 shown in FIG. In FIG. 3, 8 is a detection circuit for detecting a deviation ΔV from a predetermined reference voltage, that is, a varying voltage, and the voltage V ₂ applied to the load 5 is inputted thereto. 9 is a pulse generation circuit that generates a pulse train timing signal 9a, and a voltage applied to the load 5.
V ₂ is input. 10-1 and 10-2 are deviations △
One of the comparison circuits 10-1, which is a comparison circuit to which V is input, compares the deviation △V with a reference voltage +Vs that sets its upper limit, and when the deviation △V becomes larger than the reference voltage +Vs. When the output signal is 10-1
Set a to “1”. In addition, the other comparison circuit 10-
2 is the reference voltage − that sets the deviation △V and its lower limit.
Vs, and when the deviation △V becomes a negative voltage than the reference voltage -Vs, the output signal 10-2a is set to "1".
Make it.

The pulse generation circuit 9 outputs a voltage V ₃ or an output voltage V ₂ having the same phase as the voltage V ₃ (it is correct in a strict sense that the voltage V ₃ is applied to the pulse generation circuit 9, but the voltage V ₂ and the voltage V ₃ is the relationship between the primary voltage and the secondary voltage of the transformer, so they are in the same phase, and in actual circuits, for convenience, the zero point of the output voltage V ₂ is regarded as the zero point of the voltage V ₃ . , V = V = ₁ ±k・V = ₃
(where k is the voltage ratio of the series transformer), and V〓 ₂ and V〓
Since the phases of _V〓1 and V〓2 are equal, it can be considered that the phases of _V〓1 and _V〓2 are also equal. ) The timing signal 9a is generated when the phase advances by α ₁ degree from the zero crossing point where the transition from positive to negative occurs, and this
-1, 11-2. and gate 11
-1 and 11-2 gate the respective output signals 10-1a and 10-2a from the comparator circuits 10-1 and 10-2 using the timing signal 9a, and the signal 1
1-1a and 11-2a are obtained. Signal 11-1
a, 11-2a are input to the decoding circuit 12. The decoding circuit 12 receives signals 11-1a and 11-1a.
When -2a is "1, 0", the signal 12a is set to "1", and when it is "0, 0", the signal 12a is set to "1".
When b is set to "1" and "0, 1", the signal 12c is set to "1". The signals 12a, 12b, 12c are
The signal is input to an output circuit 13 including a selector circuit.
When the signal 12a is "1", the output circuit 13 sets the signals 13b and 13c to "1" and the signal 12b to "1".
In this case, the signals 13b and 13d are set to "1", and the signal 1 is set to "1".
When 2c is "1", the signals 13a and 13d are set to "1" and the others are outputted as "0". signal 13
a to 13d are the thyristors shown in Fig. 2, respectively.
This is the ignition signal for the switches 6-1 to 6-4, and the signal 13 is used for the AND gate 11-1 to the output circuit 13.
This is a logic circuit for selectively outputting a to 13d.

Next, the operation of the control circuit shown in FIG. 3 will be explained below using FIG. 4. FIG. 4a shows the input voltage V ₁ of the automatic voltage regulator. Moreover, the same figure b shows the output voltage _V2 of the automatic voltage regulator. This output voltage V ₂ is input to the detection circuit ₈ of the control circuit shown in FIG.
is calculated and outputs a DC voltage signal proportional to the magnitude of the deviation ΔV as shown in FIG. 4c.

On the other hand, the output voltage V ₂ having the same phase as the voltage V ₃ is input to the pulse generation circuit 9 . In this pulse generating circuit 9, the timing signal 9a is output when the output voltage V ₂ advances α ₁ degree from the zero cross point where it changes from positive to negative.
occurs. 9a is a pulse-like signal as shown in FIG. 4e.

Considering the case where there is no voltage fluctuation in the input voltage V ₁ before time t ₁ in Fig. 4, the deviation △V of the detection circuit is near zero as shown in Fig. 4 c. As shown in FIG. 4c, the comparator circuit 10
Since the comparison value of -1 is within the range of +Vs and the comparison value of comparison circuit 10-2 -Vs, comparison circuits 10-1 and 1
0-2, and as shown in FIG. 4d, the output signals 10-1 and 10-2 of the comparator circuits
1a and 10-2a are "0". (In the figure, only 10-2a is shown.) Therefore, the signals 11-1a and 11-2a from the AND gates 11-1 and 11-2 correspond to the signals f and g in FIG.
As shown in the figure, it becomes "0". The above signals 11-1a and 11-2a are supplied to the next stage decoding circuit 1.
2 is input. The decoding circuit 12 is composed of a kind of up/down counter, and the input signal 1
A counter operates according to the states of 1-1a and 11-2a. For example, when the signals 11-1a and 11-2a are both "0, 0", the output of the decoding circuit 12 maintains the current state, but the signals 11-1a and 11-
When the state with 2a is "1, 0", it counts down, and when it is "0, 1", it counts up, and the outputs 12a to 12c are outputted according to the logic table shown in FIG.

If the polarity of the series transformer 4 is set as shown in FIG. 2, the relationship between the tap position and the on/off state of the thyristor switches 6-1 to 6-4 and the
₁ , V〓 ₂ , and V〓 ₃ voltage vectors have magnitudes and directions as shown in FIG. That is, Figure 11a
11b shows the state of tap +1, FIG. 11b shows the state of tap 0, and FIG. 11c shows the state of tap -1.

If there is no voltage fluctuation in the input voltage V ₁ before time t ₁ , the values of the signals 11-1a and 11-2a are both "0", so the signals 12a to 1
2c maintains its current state, and if it is now at the tap 0 position in this state, the signal 12a is "0", the signal 12b is "1", and the signal 12b is "1", as shown in FIG. 12c outputs a signal of "0". These signals 12a, 12b, and 12c are input to the output circuit 13 at the next stage. This output circuit 13 outputs signals 13a and 13d according to the logic table shown in FIG.
Output.

Output signals 13a to 13d are firing signals of thyristor switches 6-1 to 6-4 shown in FIG. 2, respectively, and before time _t1 , output signals 13b and 13d are activated as shown in FIG. 4 k to n. The signal is set to "1", turning on the thyristor switches 6-2 and 6-4. In this state, both ends of the secondary winding 4b of the series transformer 4 are short-circuited, so the so-called tap 0 state (thyristor switches 6-2 and 6
-4 is on) and the input voltage is
V ₁ and output voltage V ₂ are equal.

Next, consider the case where the input voltage V ₁ decreases stepwise at time t ₁ as shown in FIG. 4a. As the input voltage _V1 decreases, the output voltage _V2 also decreases as shown in Figure 4b, so the deviation △V of the detection circuit 8 outputs a negative signal proportional to the voltage drop as shown in Figure 4c. .

Since this deviation △V exceeds the reference voltage -Vs that sets the lower limit, which is the comparison value of the comparison circuit 10-2 at time _t2 , the comparison circuit 10-2 operates and the output signal 10
-2a outputs a “1” signal.

When the output signal 10-2a of the comparator circuit _10-2 becomes "1", the timing signal 9a of the pulse generation circuit 9 is generated at time _t3 , which is α ₁ degree ahead of the zero-crossing point of the voltage V2. 11-2 operates and outputs a signal 11-2a as shown in FIG. 4g.
becomes “1”. As a result, according to the logic shown in FIG.
2c advances one step and changes as shown in FIG. 4 h to j, and further changes the output of the output circuit 13 as shown in FIG. 4 k to n in accordance with the logic of FIG. Therefore, at time _t3 , thyristor switch 6-2 is OFF, and thyristor switch 6-1 is turned OFF.
turns on, and the thyristor switch 6 turns on smoothly without overcurrent as shown in Figure 6d.
A switch can be made from -2 to 6-1, and a switch from tap 0 to tap +1.
As a result, the output voltage V ₂ is compensated for the voltage drop as shown in FIG. 4b, so the deviation ΔV of the detection circuit 8 is
returns to near zero as shown in FIG. 4c, and the output signal 10-2a of the comparator circuit 10-2 becomes "0" again at time _t4 . In this state, the decoding circuit 12 maintains the current state, so the tap continues to be in the +1 state, and while the input voltage is decreasing, the tap gradually becomes +1, which can almost compensate for the voltage fluctuation of the output voltage _V2 .

Also, for example, to explain the operation of lowering the tap from +1 tap to 0 tap, if a conventional control circuit that randomly selects the phase angle α ₁ is used, the α ₁ may be selected later than the zero cross point where the voltage V ₂ changes from positive to negative. In order to switch the tap position from +1 to 0, it is necessary to commutate the load current I _L2 from the thyristor switch 6-1 to the thyristor switch 6-2. To commutate the current from thyristor switch 6-1 to thyristor switch 6-2, a point (point B) delayed by α ₁ from the zero cross point (point A in Fig. 6) where voltage V ₂ changes from positive to negative. ), when the thyristor switch 6-2 is turned on, the voltage V ₂ is negative at this point, so the thyristor switch 6-2 is turned on.
The current flowing through the thyristor switches 6-1 and 6-2 increases in the direction of increasing the current flowing through the thyristor switches 6-1 and 6-2, and there is a risk that an excessive current may destroy the thyristor elements.

However, in the present invention, the thyristor switch is activated at a point (point C) where _the phase angle α ₁ shown in _FIG . When the switch 6-2 is turned on, the voltage V ₂ is positive at this point, so the current flows in a direction that cancels the current flowing through the thyristor switch 6-1, and the thyristor switch 6-2 is turned on at point d in the diagram.
The current in 1 becomes 0 and the thyristor switch 6-
1 is turned off and the load current I _L2 is turned off by the thyristor.
The current can be commutated to the switch 6-2, overcurrent can be prevented during commutation, and the withstand capacity of the thyristor element can be lowered, resulting in the advantage that the device can be made inexpensive.

Next, the operation when the load 5 is inductive is explained in the seventh section.
This will be explained with reference to the figures. Figure 7a shows the AC voltage V ₁
FIG. _7b shows _the voltage V 3 across the secondary winding 3b of the regulating transformer 3 and the current I _L2 flowing through the secondary winding 4b of the series transformer 4. 7d shows the current I ₁ flowing through the thyristor switch 6-1 in the direction of the arrow in FIG. 2, and FIG. 7e shows the current I ₂ flowing through the thyristor switch 6-2 in the direction of the arrow in FIG. show. As is clear from Figure 7,
The firing signals 13a to 13d change the time from time _t1 to time
The thyristor switch 6-1 turns from on to off until _t2 , and the thyristor switch 6-2 turns on from time _t1 . Between times _t1 and _t2, commutation current _I4 flows in the direction of the arrow shown in FIG. 7c through the thyristor switches 6-1 and 6-2. As is clear from such an operation, the current I _L1 supplied to the load 5 is
Any conversion of firing from -4 to 6-2, 6-3 or vice versa is continuous and has a fast compensatory response to varying voltages.

FIG. 8 shows a block diagram of a control circuit according to a second embodiment of the invention. Commutation current shown in Figure 7c
If I _L is large, thyristor switches 6-1 to 6
-4 may be destroyed, so in Fig. 8, in addition to the timing signal 9a, the timing signal 9-1a is
The commutation current is generated and controlled as explained below.
Control to make I ₄ small.

That is, the pulse generating circuit 9-1 has the same configuration as the pulse generating circuit 9, and is set to output the timing signal 9-1a at a phase angle of α ₂ (<α ₁ ). The timing signal 9-1a is
It is input to AND gate 11-2. The rest of the configuration is the same as in FIG. 3.

FIG. 9 shows a block diagram of a control circuit according to a third embodiment of the invention. In the embodiment shown in FIG. 9, the following control is performed so that the load 5 can handle both inductive and capacitive loads.

That is, a determination circuit 14 is provided which inputs the voltage V ₂ and the current I _L1 and determines whether or not the load 5 is inductive based on the phase difference between them. As a result of the determination, the determination circuit 14 outputs the signal 14a as "1" when the load 5 is inductive. The signal 14a is
Gates 16-1, 16-2 and inverter 15
The signal is input to AND gates 16-3 and 16-4 via. AND gates 16-1 and 16-3 input the timing signal 9a, and AND gate 1
6-2 and 16-4 input the timing signal 9-1a. The outputs of AND gates 16-1 and 16-4 are supplied to AND gate 11-1 via OR gate 17-1, and
The outputs of 2 and 16-3 are supplied to AND gate 11-2 via OR gate 17-2. AND gate 16-1 to or gate 17-2 are
This is a gate circuit that switches the output destination of the timing signals 9a and 9-1a.

When the load 5 is inductive, the signal 14a of the discrimination circuit 14 becomes "1", so the timing signal 9a is output to the AND gate 11-1 via the AND gate 16-1 and the OR gate 17-1. guided by. Also, the timing signal 9-1a is
It is led to AND gate 11-2 via gate 16-2 and OR gate 17-2. Below, the operation by introducing timing signals 9a and 9-1a into AND gates 11-1 and 11-2, respectively, is as follows.
It will be the same as the one in Figure 7.

Next, when the load 5 is capacitive, the signal 14a is "0" and the output of the inverter 15 is "1", so the timing signal 9a is output from the AND gate 16.
-3 and or via gate 17-2.
The timing signal 9-1 is guided to the gate 11-2.
a is AND gate 16-4 and OR gate 1
7-1 to AND gate 11-1. In this way, AND gate 11-1,1
Timing signals 9 and 9-1a are introduced to 1-2, respectively, in a manner opposite to that in the inductive case, and the capacitive case deals with a reverse voltage having a polarity opposite to that in the inductive case.

In addition, in the embodiment of this invention shown in FIG.
Adjusting the compensation voltage AC voltage input to the transformer 3
As shown _{in FIG} . Thyristor switch 6-1 from the line
A compensation voltage to be switched and controlled in steps 6-4 to 6-4 may be obtained, and the same effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the phase of the firing signal that controls the firing of the thyristor switch for switching the polarity of the compensation voltage is controlled so as to reduce the commutation current that occurs when switching the polarity of the thyristor switch.
Not only can the bypass thyristor switch be omitted and the response of the device can be improved, but also overcurrent can be prevented during commutation.
This has the effect of lowering the withstand capacity of the thyristor switch, thereby making the device cheaper. In addition, we have installed a discrimination circuit that discriminates the reactance characteristics of inductive or capacitive loads, and we have made it possible to switch the timing signal output line based on the output signal, so it is compatible with either inductive or capacitive loads. There is an effect that can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of the main circuit constituting a conventional automatic voltage regulator, Fig. 2 is a connection diagram of the main circuit of an automatic voltage regulator according to an embodiment of the present invention, and Fig. 3 is shown in Fig. 2. A block diagram of the control circuit in the automatic voltage regulator, FIG. 4 is a waveform diagram explaining the operation of the control circuit in FIG. 3, and FIG. 5 is a logic diagram showing the output signal in FIG. 3 in relation to the raising and lowering of the tap. , FIG. 6 is a waveform diagram explaining the tap-up operation of the automatic voltage regulator shown in FIG. 2, and a diagram showing the switch selection logic. FIG. 8 and 9 are block diagrams of control circuits showing other embodiments of the invention, FIG. 10 is a connection diagram of the main circuit of an automatic voltage regulator according to another embodiment of the invention, and FIG. FIG. 4 is an explanatory diagram showing the relationship between the tap state, the on/off state of the switch, and the voltage vector according to the invention. 3, 4...Transformer, 5...Load, 6-1 to 6-
4, 7... Thyristor switch, 8... Detection circuit, 9, 9-1... Pulse generation circuit, 10-1,
10-2...Comparison circuit, 12...Decoding circuit,
13...Output circuit. Note that the same reference numerals in the figures indicate the same parts.

Claims (1)

[Claims] 1. A series transformer having a primary winding connected in series to a load to which an alternating voltage is supplied and a secondary winding supplying a compensation voltage to compensate for fluctuations in the alternating voltage; a switch circuit that bridge-connects a thyristor connected in antiparallel to a secondary winding of a transformer, and selects the polarity of the compensation voltage by selective firing of the thyristor; and a control circuit that selectively outputs an ignition signal that fires the thyristor based on the control circuit, the control circuit includes a detection circuit that detects a fluctuating voltage of an AC voltage, and a voltage that is predetermined as the fluctuating voltage. a comparator circuit that compares the comparison result with a reference voltage and outputs a comparison result; a pulse generation circuit that generates a timing signal with a constant advance phase from a zero cross point where the load voltage changes from positive to negative; and a logic circuit that selectively outputs an ignition signal for igniting the thyristor based on the thyristor. 2. A series transformer having a primary winding connected in series to a load to which alternating current voltage is supplied and a secondary winding supplying a compensation voltage that compensates for fluctuations in the alternating voltage, and a secondary winding of this series transformer. a switch circuit that bridge-connects thyristors connected in antiparallel to a line, and selects the polarity of the compensation voltage by selectively firing the thyristor; and firing the thyristor based on the phase of the fluctuating voltage and the alternating current voltage. In the automatic voltage regulator, the control circuit includes a detection circuit that detects a fluctuating voltage of an alternating current voltage, and a control circuit that selectively outputs an ignition signal that causes an ignition to occur. a comparator circuit that outputs a comparison result; first and second pulse generation circuits that generate timing signals at different leading phases from a zero cross point where the load voltage changes from positive to negative; and the comparison result and the timing signal. and a logic circuit that selectively outputs an ignition signal for igniting the thyristor based on the thyristor. 3. A series transformer having a primary winding connected in series to a load to which an alternating current voltage is supplied and a secondary winding supplying a compensation voltage that compensates for fluctuations in the alternating voltage, and a secondary winding of this series transformer. a switch circuit that bridge-connects thyristors connected in antiparallel to a line, and selects the polarity of the compensation voltage by selectively firing the thyristor; and firing the thyristor based on the phase of the fluctuating voltage and the alternating current voltage. In the automatic voltage regulator, the control circuit includes a detection circuit that detects a fluctuating voltage of an alternating current voltage, and a control circuit that selectively outputs an ignition signal that causes an ignition to occur. a comparator circuit that outputs a comparison result, first and second pulse generation circuits that generate timing signals at different leading phases from the zero cross point where the load voltage changes from positive to negative; a discriminating circuit for discriminating the reactance characteristic of the load as a phase leading load or a lagging phase load based on the current; a gate circuit for switching the output line of the timing signal based on the output signal of the discriminating circuit; and a logic circuit that selectively outputs an ignition signal for igniting the thyristor based on the timing signal inputted through the thyristor.