JPH05292686A - Ac switching equipment - Google Patents

Abstract

PURPOSE:To prevent a cross current from flowing without providing a cross-current control means in a power device, and without using switching elements having a self-arc-extinguishing function as AC switches, in case of changing power sources. CONSTITUTION:Power devices 1 and 2 to be connected to a load 3 are changed by switching one of AC switches 10 and 20 from an on-state over to an off-state, and the other from an off-state over to an on-state. On that occasion, the direction of a load current is discriminated by a discriminating means 30, and firing starts from a thyristor of the same polarity as the direction of the load current at that point of time. As the result, it becomes possible to prevent a cross current from flowing between the power sources 1 and 2 in a period of a half cycle after the firing of the thyristor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC switch device that selectively uses an uninterruptible power supply and a commercial power supply depending on the situation, and in particular, when a large overload or a failure of the uninterruptible power supply occurs, the power supply is cut off. The present invention relates to an AC switch device that can be switched by a momentary interruption and can continuously supply power to a load.

[0002]

2. Description of the Related Art A switching element having a self-extinguishing function may be used in an AC switching device for switching between an uninterruptible power supply and a commercial power supply. However, since the switching element having the self-extinguishing function is expensive, it is generally used. , A switching element in which thyristors are connected in antiparallel is used.

When an alternating current switching device is constructed by using switching elements in which thyristors are connected in antiparallel, when switching the power supply, a current flows between the alternating current switching devices during a half cycle in which a firing signal is applied to the thyristor. Flow (hereinafter this current is called cross current). Therefore, in order to prevent the cross current from becoming large, it is necessary to control the cross current in the uninterruptible power supply.

FIG. 5 is a diagram showing a conventional example of an AC switch device for switching between an uninterruptible power source and a commercial power source. In FIG. 5, 1 is an uninterruptible power source, 2 is a commercial power source, 3 is a load, 5 is a knot circuit, Reference numerals 10 and 20 are first and second AC switches, and reference numerals 11, 12, 21, and 22 are thyristors. In the figure, the first and second AC switches 10 and 20 are composed of anti-parallel circuits of thyristors 11, 12 and 21, 22. The uninterruptible power supply 1 and the commercial power supply 2 are the first and second AC power supplies. Load 3 via switches 10 and 20
Connected with.

The switching signal C is a signal for switching the first and second AC switches 10 and 20. The switching signal C is directly applied to the first AC switch 10 and the second AC switch 20 is knotted. The circuit 5 provides a signal obtained by inverting the switching signal C. Therefore, when the switching signal C is at the high level, the first AC switch 1
0 is on, the second AC switch 20 is off, and the uninterruptible power supply 1 supplies power to the load 3. Further, when the switching signal C is at the low level, the second AC switch 20 is turned on and the first AC switch 10 is turned off,
Power is supplied to the load 3 from the commercial power supply 2.

FIG. 6 is a time chart showing the operation of the conventional example shown in FIG. 5, in which V1 is the voltage of the uninterruptible power supply 1, V2 is the voltage of the commercial power supply 2 and current I1 is the uninterruptible power supply. 1 current and current I2 are commercial power source 2 current and current I
3 is a current flowing through the load 3. In the figure, the voltage V1 of the uninterruptible power supply 1 is higher than the voltage V2 of the commercial power supply 2, the voltage phase of the uninterruptible power supply 1 and the voltage phase of the commercial power supply 2 match, and the current phase lags the voltage phase. The case of a delay power factor is shown.

Next, the operation of the conventional example shown in FIG. 5 will be described with reference to FIG. When the switching signal C is at high level, the first
When the AC switch 10 is turned on, the uninterruptible power supply 1
Is supplied to the load 3 and the current I is supplied from the uninterruptible power supply 1.
1 flows through the load 3, and the current I3 matching the current I1 flows through the load 3. Now, at the time point t, when the switching signal C becomes low level, the first AC switch 10 is turned off and the second AC switch 20 is turned on.

Here, the thyristor 12 of the first AC switch 10 maintains the ON state for the half cycle even when the ignition signal is turned OFF. Therefore, when an ON signal is given to the second AC switch 20 and the thyristor 21 is turned on, a cross current flows via the commercial power supply 2 → thyristor 21 → thyristor 12 → uninterruptible power supply 1.

This cross current flows for a period of t1 shown in FIG. 6, and when the current becomes zero, the thyristor 12 turns off,
Power is supplied to the load 3 from the commercial power supply 2.

[0010]

As described above, in the conventional device shown in FIG. 5, a cross current flows between the power sources during a half cycle when the power source is switched. Therefore, conventionally, it is necessary to provide a means for controlling the cross current in the uninterruptible power supply, which makes the device complicated and is one of the factors that reduce the reliability of the device.

The present invention has been made in view of the above-mentioned drawbacks of the prior art. An expensive element having a self-extinguishing function is used as a switching element of an AC switch, and a cross current control means is provided in a power supply device. It is an object of the present invention to provide a highly reliable AC switch device capable of preventing a cross current flowing between power sources with a simple structure that does not need to be provided and that is inexpensive.

[0012]

In order to solve the above problems, in the present invention, first and second AC switching devices in which thyristors are connected in anti-parallel, and first and second AC switching devices are provided.
And a load connected to the first and second AC switches, and one of the first and second AC switches is in a conductive state. From the non-conducting state and the other AC switch from the non-conducting state to the conducting state, in the AC switching device for switching the power supply device connected to the load, means for determining the direction of the load current is provided, When switching the conduction state, the gate of one AC switch is blocked, and among the thyristors connected in anti-parallel to the other AC switch, ignition is started from the thyristor with the same polarity as the direction of the load current at that time. As a result, a cross current flowing between the power supplies is prevented.

[0013]

The power supply device connected to the load is switched by changing one of the first and second AC switches from the conductive state to the non-conductive state and the other AC switch from the non-conductive state to the conductive state. At this time, the output of the means for determining the direction of the load current causes the thyristor having the same polarity as the direction of the load current at that time to start firing.

As a result, for example, when switching from the first power supply having a large power supply voltage to the second power supply having a small power supply voltage, the thyristor having the same polarity as the direction of the load current has a half cycle to which the firing signal is applied. It is possible to prevent the cross current from flowing even if the gate-blocked thyristor is in the conductive state during the half cycle, while it is not reverse-biased to be in the conductive state during the period.

Further, for example, when switching from a first power supply having a low power supply voltage to a second power supply having a high power supply voltage, the thyristor having the same polarity as the direction of the load current immediately becomes conductive, and the gate block. The formed thyristor is immediately brought into a non-conducting state, so that cross current can be prevented.

[0016]

FIG. 1 is a diagram showing an embodiment of the present invention. In the figure, the same components as those shown in FIG. 5 are designated by the same reference numerals, 1 is an uninterruptible power supply, 2 is a commercial power supply,
3 is a load, 5 is a knot circuit, 6 and 7 are first and second ignition condition circuits, 10 and 20 are first and second AC switches, 11, 12, 21, and 22 are thyristors, and 30 is a discrimination. The container 31 is a knot circuit.

In the same figure, the discrimination circuit 30 has a load current I.
Depending on the polarity of 3, if the load current is positive,
Level signal, and if the load current is negative,
A circuit that outputs a low-level signal, the output of which is the second signal via the firing condition circuit 6 and the knot circuit 31.
Is connected to the ignition condition circuit 7. The first and second ignition condition circuits 6 and 7 are circuits that ignite the first AC switch 10 or the second AC switch 20 in accordance with the switching signal C, and at that time, load current. Depending on the polarity of I3, the thyristor 11 or 12 of the AC switch 10 or the thyristor 21 of the AC switch 20
Or one of the 22 thyristors is fired first,
When the load current I3 becomes zero, the other thyristor is fired.

FIG. 2 is a diagram showing an example of the circuit configuration of the ignition condition circuits 6 and 7 of FIG.
65, 66, 71, 72, 75, 76 are NAND circuits, 6
3, 67, 73, 77 are knot circuits, 64, 68, 7
Reference numerals 4 and 78 denote AND circuits, and the same components as those in FIG. 1 are designated by the same reference numerals. In the figure, the switching signal C is given to the NAND circuits 61 and 65 and the knot circuit 5, and the output of the knot circuit 5 is given to the NAND circuits 71 and 75.

The output of the discriminator 30 is the NAND circuit 6
6, 76, given to the knot circuit 31, and knot circuit 31
Is output to the NAND circuits 62 and 72. The NAND circuits 61, 65, 71 and 75 are NAND circuits 62 and 65, respectively.
66, 72, and 76, a holding circuit whose output is used as an input of the other NAND circuit is formed.
The outputs of 1, 65, 71, 75 are knot circuits 63, 67,
73, 77.

The AND circuits 64 and 68 generate outputs when the outputs of the knot circuits 63 and 67 and the switching signal C match, and the AND circuits 74 and 78 output the outputs of the knot circuits 73 and 77 and the knot circuit 5, respectively. Generates output when match. 3 and 4 are time charts showing the operation of the embodiment of the present invention, in which V1 is the voltage of the uninterruptible power supply 1, V2 is the voltage of the commercial power supply 2, and the current I.
1 is the current of the uninterruptible power supply 1, current I 2 is the current of the commercial power supply 2, current I 3 is the current flowing through the load 3, firing signals p, q,
r and s are firing signals of the thyristors 11, 12, 21, 22 respectively.

In the figure, as in the conventional example, the voltage V1 of the uninterruptible power supply 1 is higher than the voltage V2 of the commercial power supply 2, the voltage phase of the uninterruptible power supply 1 and the voltage phase of the commercial power supply 2 match, and , Shows the case of a delay power factor in which the current phase lags the voltage phase. Next, the operation of this embodiment shown in FIGS. 1 and 2 will be described with reference to FIGS. In FIG. 1, when the switching signal C is at the high level, the firing signals p and q which are the outputs of the firing condition circuit 6 are at the high level, and the thyristors 11 and 12 of the first AC switch 10 are turned on. Also, the firing signals r and s, which are the outputs of the firing condition circuit 7, are at a low level, and the thyristors 21 and 21 of the second AC switch 20 are
22 is in a non-conducting state.

That is, in FIG. 2, the switching signal C
Is at a high level, one input of the NAND circuit 61 of the ignition condition circuit 6 is at a high level, and the output of the NAND circuit 62 is at a high level. The input is also at high level and its output is at low level. Therefore, the knot circuit 63
Output of the AND circuit 64 becomes high level because both inputs of the AND circuit 64 are high level.
And the ignition signal p becomes high level.

Similarly, the AND circuit 68 of the ignition condition circuit 6
Is also at a high level, and the ignition signal q is at a high level. On the other hand, regarding the ignition signals r and s of the ignition condition circuit 7, when the switching signal C is at the high level, the output of the knot circuit 5 becomes the low level, and the AND circuit 74 of the ignition condition circuit 7 and the AND circuit. The output of 78 goes low, and the firing signals r and s go low.

As described above, when the switching signal C is at the high level, the first AC switch 10 is in the ON state and the second AC switch 20 is in the OFF state. Power is supplied to the uninterruptible power supply 1
Therefore, the current I1 is flowing in the load 3. (1) Switching the power supply from the uninterruptible power supply 1 side to the commercial power supply 2 side.

Now, as shown in FIGS. 3 and 4, when the output of the discriminator 30 for detecting the polarity of the load current is at the low level at time t, the switching signal C goes to the low level. The outputs of the AND circuit 64 and the AND circuit 68 of the ignition condition circuit 6 shown in the figure are low level, and the ignition signals p and q are low level.
2 is gate blocked and AC switch 10 is off.

Since the thyristor 12 of the first AC switch 10 maintains the ON state until the current becomes zero even when the ignition signal is turned off, the current I1 of the uninterruptible power supply 1 becomes As shown in FIG. 3, it lasts until time t ′. On the other hand, when the switching signal C becomes low level, the output 5 of the knot circuit 5 becomes high level.

Here, as shown in FIGS. 3 and 4, when the discriminator 30 for detecting the polarity of the load current is at a low level,
Since the output of the NAND circuit 76 of the firing condition circuit 7 shown in FIG. 2 is at a high level, when the output of the knot circuit 5 goes to a high level, the output of the NAND circuit 75 goes to a low level. As a result, the output of the NAND circuit 76 becomes high level, and the low level state of the output of the NAND circuit 75 is held regardless of the output of the discriminator 30 as long as the output of the knot circuit 5 is high level. ..

Therefore, the output of the knot circuit 77 becomes high level, and both inputs of the AND circuit 78 are high.
Since it becomes a level, its output becomes a high level, and the ignition signal s becomes a high level. Therefore, an ignition signal is applied to the thyristor 22 of the AC switch 20 shown in FIG.
The thyristor 22 does not fire because it is reverse biased.

On the other hand, when the output of the discriminator 30 is at a low level, the output of the knot circuit 31 is at a high level, so the input of the NAND circuit 72 in FIG. 2 is at a high level and the other input. Since the output of the NAND circuit 71 is also at high level, the output of the NAND circuit 72 is at low level.
Therefore, the output of the NAND circuit 71 is at a high level, the output of the knot circuit 73 is at a low level, the output of the AND circuit 74 is at a low level, and the firing signal r is at a low level.

Therefore, at this time point, the ignition signal is not applied to the thyristor 21 of the AC switch 20. Here, as shown in FIG. 3, at time t ′, the current I1
, I2 becomes zero and the output of the discriminator 30 changes from low level to high level, the output of the knot circuit 31 becomes low level.

Therefore, the output of the NAND circuit 72 of the ignition condition circuit 7 of FIG. 2 is at the high level, and the output of the NAND circuit 71 is at the low level because the output of the knot circuit 5 is at the high level. This state is held regardless of the state of the knot circuit 31 as long as the output of the knot circuit 5 is at the high level. When the output of the NAND circuit 71 becomes low level, the output of the knot circuit 73 becomes high level, the output of the AND circuit 74 becomes high level, and the firing signal r becomes high level.

Therefore, a firing signal is applied to the thyristor 21 of the AC switch 20, the thyristor 21 is fired, and thereafter, the commercial power source 2 supplies power to the load 3.
When the output of the discriminator 30 that detects the polarity of the load current is at a high level and the switching signal C becomes a low level, the firing signal r of the firing condition circuit 7 is at a high level at that time. Next, the thyristor 21 of the AC switch 20
A firing signal is applied to the thyristor 21, but the thyristor 21 is reverse-biased and does not fire similarly to the above.

Then, as described above, the currents I1 and I2 are
Becomes zero and the output of the discriminator 30 changes from high level to low level, the ignition signal s of the ignition condition circuit 7 becomes high level, and the ignition signal is added to the thyristor 22 of the AC switch 20 to add the ignition signal. 22 fires, and thereafter
The load 3 is supplied with power from the commercial power supply 2. As described above, when the power supply to the load is switched from the power supply side having a high voltage (the uninterruptible power supply side) to the power supply side having a low voltage (the commercial power supply side), the switching signal C is output at the time of output. The polarity of the load current I3 is determined, an ignition signal is given to the reverse biased thyristor of the AC switch thyristors on the power supply side with a small voltage, and then the other thyristor is reached when the current becomes zero. Since the ignition signal is given to the power supply, the power supply is switched at the time when the load current becomes zero, and the cross current does not flow. (2) Switching from the commercial power supply 2 side to the uninterruptible power supply 1 side.

When the output of the discriminator 30 is at the low level and the switching signal C becomes the high level again while the power is being supplied from the commercial power source 2 to the load 3, the knot circuit 5 is activated. Becomes low level, the outputs of the AND circuits 74 and 78 of the ignition condition switching circuit 7 become low level, and the ignition signals r and s become low level. In addition, the NAND circuits 71 and 72 and the NAND circuit 7
The hold states of 5 and 76 are released.

On the other hand, when the switching signal C becomes high level, the ignition condition switching circuit 6 sets the ignition signal q to high level and causes the thyristor 12 of the AC switch 10 to fire as in the above case. In this case, the voltage V
Since 1> voltage V2, the thyristor 22 of the AC switch 20 is reverse-biased and immediately turned off, and the current flowing from the commercial power supply 2 to the load 3 is transferred from the uninterruptible power supply 1 to the load 3 via the thyristor 12. Supplied.

Then, as described above, the thyristor 11 of the AC switch 10 is turned on when the current becomes zero, and then the uninterruptible power supply 1 supplies power to the load 3 via the thyristor 11. When the output of the discriminator 30 is at a high level and the switching signal C goes to a high level, an ignition signal is given to the thyristor 11 of the AC switch 10 and the thyristor 22 of the AC switch 20 is reverse biased. The current immediately turns off and the current flowing from the commercial power supply 2 to the load 3 is supplied from the uninterruptible power supply 1 to the load 3 via the thyristor 11.

Next, as described above, the thyristor 12 of the AC switch 10 is turned on at the time when the current becomes zero, and then the uninterruptible power supply 1 supplies power to the load 3 via the thyristor 12. As described above, when switching from a low-voltage power supply side (commercial power supply side) to a high-voltage power supply side (uninterruptible power supply side), the thyristor of the AC switch on the high voltage side turns on immediately and the low-voltage side. The thyristor of the AC switch turns off immediately,
Although the current is switched from the power source side having a low voltage to the power source side having a high voltage, a cross current does not flow as in the case of (1).

In the above embodiment, a single-phase power source is described for the sake of simplicity, but the present invention is not limited to the above-described embodiment and can be applied to a multi-phase power source. Needless to say. Further, in the above-mentioned embodiment, the switching between the uninterruptible power supply and the commercial power supply has been described, but the present invention is not limited to the above-mentioned embodiment, and can be applied to switching of other power supplies.

[0039]

As is clear from the above description,
In the present invention, an AC switch device in which thyristors are connected in anti-parallel is provided between the first power source, the second power source and the load, and the AC switch is switched to change the power source to the first power source.
In the AC switching device for switching to the second power source or the second power source, the polarity of the load current is determined at the time of switching,
Among the thyristors of AC switches, the thyristor with the same polarity as the load current is used to start firing, so expensive elements with self-extinguishing function can be used as switching elements of AC switches, or power supply devices. It is not necessary to provide the cross current control means in the above, and it is possible to prevent the cross current flowing between the first power supply and the second power supply with a simple structure and at a low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a firing condition circuit.

FIG. 3 is a time chart showing the operation of the embodiment of the present invention.

FIG. 4 is a time chart (continuation) showing the operation of the embodiment of the present invention.

FIG. 5 is a conventional example.

FIG. 6 is a time chart showing an operation of a conventional example.

[Explanation of symbols]

1 uninterruptible power supply 2 commercial power supply 3 load 5 knot circuit 6,7 ignition condition circuit 10,20 AC switch 11, 12, 21, 22 thyristor 30 discriminator 31 knot circuit 61, 62, 65, 66, 71, 72, 75,76 NAND circuit 63,67,73,77 knot circuit 64,68,74,78 AND circuit

Claims (1)

[Claims] 1. A first and a second AC switch device in which thyristors are connected in antiparallel, a first and a second power supply device connected to the first and second AC switches, and a first and a second power supply device. And a load connected to the AC switch of, wherein one of the first or second AC switches is switched from a conductive state to a non-conductive state, and the other AC switch is switched from a non-conductive state to a conductive state, In an AC switch device that switches the power supply device connected to the load, a means for determining the direction of the load current is provided, and when switching the conduction state of the AC switch, while blocking the gate of one AC switch,
By starting ignition from a thyristor connected in anti-parallel to the other AC switch in the same polarity as the direction of the load current at that time, cross current flowing between the first and second power supplies was prevented. An AC switch device characterized in that