JPH0429533A - Ac switching circuit - Google Patents

Abstract

PURPOSE:To positively invert the polarity of voltage to be applied between the anode and cathode of a thyristor and to switch the power supply path stably and surely by providing a circuit for interrupting inverter operation over a predetermined short interval after application of a power supply path switching command and producing a command for bringing the output voltage to zero. CONSTITUTION:A circuit 8 for locking an inverter 2 is provided. When power supply to a load 5 is switched from an inverter to direct AC power supply, output voltage of the inverter 2 is brought to zero over a short interval during which a PG output pulse signal is outputted. Consequently, a reverse voltage is applied reliably between the anode and the cathode of each thyristor element in an inverter thyristor switch 3 and thereby simultaneous conduction of both thyristor switches 3, 4 is avoided stably and surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching circuit for an AC switch for switching a power supply path in an inverter power supply device having a backup AC power supply direct bypass path, such as an uninterruptible power supply device.

[Conventional technology]

As a conventional AC switch switching circuit of this type, the one shown in the circuit diagram of FIG. 2 showing an example of the overall configuration of the above-mentioned inverter power supply device is known.

In Fig. 2, ■ is an AC/DC converter that receives alternating current input AC, , rectifies it and outputs direct current;
The DC/AC converter, ie, the inverter 3, which receives the DC output of the DC converter and converts it into AC output, is composed of cyrisks connected in antiparallel to each other, and the inverter 2
A thyristor switch 4 for an inverter opens and closes a power supply path for the output load 5, and 4 has the same configuration as the switch 3, and is a direct feeder switch 4 that opens and closes a direct feed bypass path that directly feeds the AC input AC, fi to the load 5. The thyristor switch AC, □ is the AC output that is supplied to the load 5. Further, 6 is a control circuit that outputs a control command signal S2° to the inverter 2, and 7 is a control circuit for both the switches 3.
and 4, respectively, conduction/cutoff command signals S3 and 5
This is an AC output selection circuit that outputs 4 and selects both of the power supply paths.

Note that the above-mentioned signals S and 54 refer to both the above-mentioned switches 3 and 4.
and are mutually locked so that the conduction state and cutoff state of each are always opposite to each other.

In addition, when the switch 3 is cut off, the switch 4 is turned off.
In order to instantaneously re-supply power from the inverter 2 by changing the power supply route again even when the load 5 is supplied with power directly from the inverter side to the alternating current input AC, . The inverter continues its operation.

[Problem to be solved by the invention]

However, in the above-mentioned conventional switching circuit, the operation of the inverter itself continues even when the power supply route to the load is set to the direct AC power supply side, and therefore, at the point when the power supply route is switched from the inverter side to the direct supply side. In,
If the AC power supply voltage is lower than the inverter output voltage, sufficient reverse voltage cannot be applied to the thyristor switch forming the thyristor switch in the output feed path of the inverter, and the thyristor continues to conduct, thus There is a risk that the sirisk switches in the power supply paths on the inverter side and the AC power supply direct side will both become conductive, causing a cross current between the inverter and the AC power supply, resulting in instability of the power supply voltage to the load. was there.

In view of the above, it is an object of the present invention to provide an AC switch switching circuit that enables a stable change of the power feeding route regardless of the above-mentioned fluctuations in the direct-side AC power supply voltage.

[Means to solve the problem]

In order to achieve the above object, the AC switch switching circuit of the present invention provides an inverter output power supply path via a first AC switch, and a second AC switch that is mutually locked with respect to the opening/closing operation thereof. A control command signal for the inverter and a closing command for the second AC switch are input in the switching circuit of the double-receive switch in the AC power supply device that supplies power to a load by a direct bypass route of the AC power supply via the AC switch. A lock circuit is provided for interrupting the output of the control command signal to the inverter for a predetermined short period from the time when the closing command is input, and the first AC switch is opened and the second AC switch is closed. When switching between the two power feeding paths, the output of the inverter is interrupted for the predetermined short period of time.

[Effect]

In order to turn the conductive cyrisk into a cutoff state, it is necessary to reverse the polarity of the voltage applied between the anode and cathode.

Furthermore, as mentioned above, when switching the AC power supply load power supply route from the inverter side to the direct AC power supply side, the inability to switch the power supply route due to continued conduction of the inverter-side sirisk switch is caused by the instantaneous value at the time the power supply route switching command is applied. This is due to the fact that when the output voltage of the inverter is higher than the voltage of the AC power supply, the polarity of the voltage applied between the anode and cathode of the thyristor of the thyristor switch on the inverter side is not reversed. Furthermore, instantaneous value control of the two mold pressures is not performed at the time of the route switching, and the magnitude relationship between the two instantaneous values is indefinite.

Therefore, the present invention provides a circuit that instructs the inverter to suspend its operation for a predetermined short period of time from the time when the power supply path switching command is applied, and to reduce the output voltage to zero, thereby reducing the voltage applied between the anode and cathode of the thyristor. By reliably performing polarity reversal, the power supply path switching can be performed stably and reliably.

〔Example〕

Embodiments of the present invention will be described below with reference to the circuit diagram shown in FIG. In FIG. 1, the same reference numerals are given to components having the same functions as in the prior art embodiment shown in FIG. 2.

FIG. 1 is a circuit diagram of FIG. 2 in which a lock circuit 8 for a DC/AC converter, that is, an inverter 2 is provided. Further, in the lock circuit, PG is a pulse generating section that performs monostable oscillation operation, and outputs a pulse signal of a predetermined constant short time duration when a command signal S4 is applied to the direct feed thyristor switch 4, and ADD is a pulse generator that performs monostable oscillation operation. A signal synthesis unit receives the control command signal S2° for the inverter 2 and the output pulse signal of the pulse generator PC, and outputs a new control command signal S2 by interrupting the signal S2° while the PG output pulse signal continues. Therefore, the output voltage of the inverter 2 has a value of zero while the PC output signal continues.

That is, when switching from the inverter output power supply to the AC power supply direct power supply to the load 5, the output voltage of the inverter 2 is made zero for a predetermined short period of time during which the PC output pulse signal is output. A reverse voltage is surely applied between the anode and the cathode for each of the thyrisk elements, and both the thyrisk elements are
Simultaneous conduction of switches 3 and 4 is stably and reliably avoided.

〔Effect of the invention〕

According to the present invention, regarding a switching circuit for the opening/closing thyristor switch of each of the two power supply paths in an AC power supply device having an inverter output power supply path and a direct AC power supply path to a load, the AC power supply is directly transmitted from the inverter output power supply path to the switching circuit for the opening/closing thyristor switch. By providing a lock circuit that interrupts the operation of the inverter for a predetermined short period of time and makes its output voltage zero when switching to the current path, both the sirisk switches can be made conductive at the same time regardless of the presence or absence of fluctuations in the AC power supply voltage. This makes it possible to avoid such a situation, and it is possible to stably and reliably switch the power supply path as described above.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the prior art. 1...AC/DC converter, 2...DC/AC converter (inverter), 3...Sirisk switch for inverter, 4...Sirisk switch for direct feed, 5...
・Load, 6... Control circuit, 7... AC output selection circuit, 8... Lock circuit, ADD... Signal synthesis unit, PC
...Pulse generator.

Claims (1)

[Claims] 1) The inverter's output power supply path via the first AC switch and the direct feed bypass path of the AC power source via the first AC switch and a second AC switch whose opening/closing operations are mutually locked. A control command signal for the inverter and a closing command for the second AC switch are input in a switching circuit for both AC switches in an AC power supply device that supplies power, and the inverter is controlled for a predetermined short period of time from the time when the closing command is input. A lock circuit for interrupting the output of a command signal is provided, and when the first AC switch is opened and the second AC switch is closed to switch the two power supply paths, the inverter is operated for a predetermined short period of time. An AC switch switching circuit characterized by causing output interruption.