JP3284526B2 - Instantaneous voltage drop compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an instantaneous voltage drop compensator for switching a voltage supply to a load using a pair of three-terminal thyristors.

[0002]

2. Description of the Related Art Conventionally, this kind of instantaneous voltage drop compensator stores electric energy in a capacitor via a transformer connected to an AC power supply as disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 1-123436. When the instantaneous voltage of the AC power supply drops, the energy stored in the capacitor is converted into a predetermined AC output voltage by an inverter, and the AC output voltage is supplied to a load composed of various electronic devices. The voltage supply to the load is switched while monitoring the voltage value.

FIG. 2 is a circuit diagram of an instantaneous voltage drop compensator using a pair of three-terminal thyristors as voltage switching means. In FIG.
V, an input terminal to which a single-phase AC power supply 2 is connected, 3, 3A are output terminals connected to both ends of an AC-driven load 4,
A pair of voltage supply lines 5 and 5A are connected between the input terminal 1 and the output terminal 3 and between the input terminal 1A and the output terminal 3A. An output voltage V1 from the AC power supply 2 is converted into a predetermined AC voltage by a charging transformer 6 connected to the input terminals 1 and 1A, and the converted voltage is rectified by a diode bridge 7 to form a capacitor 8 To be stored as electrical energy. 9 is an inverter provided with a plurality of switching elements (not shown),
When the output voltage V1 of the AC power supply 2 decreases, each switching element is switched to supply the AC output voltage V2 to the load 4 from the output voltage lines 10, 10A. A filter circuit 11 for removing a noise component included in the output voltage V2 is connected to the output side of the inverter 9, and the filter circuit 11 removes noise and the like accompanying the switching of the switching element. The filter circuit 11 includes an inductor 12 inserted and connected to one output voltage line 10 and a capacitor 13 connected between the output voltage lines 10 and 10A.

Reference numeral 14 denotes voltage switching means for switching the voltage supply to the load 4, and includes a first thyristor 15 composed of a bidirectional three-terminal thyristor (triac) and a second thyristor 16. . Each main terminal of the first thyristor 15 is inserted and connected to the one voltage supply line 5, and each main terminal of the second thyristor 16 is inserted and connected to one output voltage line 10. Termination of output voltage line 10,
That is, one main terminal of the second thyristor 16 is connected to one main terminal of the first thyristor 15 connected to the load 4 side, whereby the load of the first thyristor 15 and the second thyristor 16 is changed. The four main terminals are connected. The other output voltage line 10A from the inverter 9 is
It is connected to the other voltage supply line 5A.

Reference numeral 17 denotes a thyristor driving circuit connected to the gates of the thyristors 15 and 16. A trigger signal synchronized with the AC power supply 2 is supplied from the thyristor driving circuit 17 to one of the first and second thyristors 15 and 16. By outputting to one side, the output voltages V1 and V2 are selectively supplied to the load 4. Reference numeral 18 denotes a current transformer as a current detecting means inserted and connected to the voltage supply line 5. Based on the current detection signal from the current transformer 18 and the terminal voltage of the capacitor 8, the control circuit 19 When the control unit 19 detects a decrease in the output voltage V1 from the thyristor 15, the control unit 19 switches the thyristors 15, 16 on and off via the thyristor drive circuit 17, and simultaneously drives the inverter 9 via the built-in inverter drive circuit. Control.

[0006]

The instantaneous voltage drop compensator having the above-described configuration supplies a trigger signal from the thyristor drive circuit 17 only to the first thyristor 15 in a normal state.
With the first thyristor 15 turned on and the second thyristor 16 turned off, the output voltage V1
Is supplied to the load 4, but if the output voltage V1 from the AC power supply 2 drops for some reason, the thyristor drive circuit
Since 17 supplies a trigger signal only to the second thyristor 16, the first thyristor 15 is turned off and the second thyristor 16 is turned on by this to switch the output voltage V2 from the inverter 9 to the load 4. I am trying to supply. However, when an inductive or capacitive load 4 is connected to the output terminals 3 and 3A, a phase difference occurs between an AC voltage and an AC current applied to the load 4, so that the first and second thyristors 15 are connected. , 16 are switched on and off, the first thyristor 15 in the conducting state is incapable of turning off until the AC current reaches near zero amperes even after the AC voltage reaches near zero volts. Become. Therefore, if the second thyristor 16 is turned on by the trigger signal from the thyristor drive circuit 17 during this time, the output voltage V2 from the inverter 9 is not supplied to the load 4 and is supplied to the AC power supply 2 via the first thyristor 15. The problem of being returned is caused. Conventionally, in order to avoid such a situation, a commutation circuit 20 for applying a reverse voltage to the first thyristor 15 is provided so that the first thyristor 15 is forcibly turned on before the second thyristor 16 is turned on. However, since the dedicated commutation circuit 20 is required, there is a problem that the circuit configuration becomes complicated.

In view of the above problems, the present invention provides an instantaneous voltage drop compensating device that can supply an output voltage from an inverter to a load when the output of an AC power supply drops, with a simple circuit configuration without separately providing a commutation circuit. The purpose is to provide.

[0008]

According to a first aspect of the present invention, there is provided an instantaneous voltage drop compensating apparatus comprising: a first thyristor inserted and connected to one of a voltage supply line between an AC power supply and a load; and an output voltage line of an inverter. A second thyristor that is inserted and connected, and switches on and off of the first and second thyristors to supply an AC output voltage from the inverter to the load when the voltage of the AC power supply drops.
In order to remove a noise component included in the AC output voltage from the inverter, in the instantaneous voltage drop compensator provided with a filter circuit having at least a capacitor connected between the output voltage lines, the AC current from the AC power supply is A charging circuit for supplying a capacitor is connected to the filter circuit, and the energy stored in the capacitor is used as an oscillating current by utilizing an inductance existing in a line from the capacitor to the first thyristor. It is configured so as to be supplied to.

According to a second aspect of the present invention, in the instantaneous voltage drop compensating device, the charging circuit is configured by connecting a diode for backflow prevention and a current limiting resistor in series between one end of the capacitor and the voltage supply line. Is what is done.

[0010]

According to the structure of the first aspect, when the AC power supply is outputting a normal voltage, energy is stored in the capacitor constituting the filter circuit via the charging circuit. On the other hand, when the voltage of the AC power source decreases, the energy stored in the capacitor moves to the line from the capacitor to the first thyristor as the second thyristor turns on. At this time, an oscillating current is generated due to the inductance existing in the line, whereby the first thyristor is forcibly turned off. Using the capacitor of the existing filter circuit and the inductance existing in the line, simply providing a capacitor charging circuit,
When the voltage of the AC power supply drops, the first thyristor can be immediately turned off.

In the configuration of the second aspect, the first thyristor can be immediately turned off when the voltage of the AC power supply drops by simply adding a diode and a resistor to the existing device.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. The same parts as those in FIG. 2 shown in the conventional example are denoted by the same reference numerals, and detailed description of the common parts will be omitted.

In the present embodiment, a capacitor 13 of the filter circuit 11, a charging circuit 21 for supplying an alternating current from the AC power supply 2 to the capacitor 13,
Of the thyristor 15 on the line 22 extending to the main terminal of the load 4 (equivalently, the dashed inductor 23
As shown. ), It is noted that a commutation circuit for forcibly turning off the first thyristor 15 is formed.
The charging circuit 21 includes a diode 24 for preventing backflow and a resistor 25 for limiting current, one end of the capacitor 13 and the voltage supply line 5.
And is connected in series. The other points are exactly the same as the configuration of FIG. 2 shown in the conventional example.

Next, the operation of the instantaneous voltage drop compensating device in the present embodiment will be described. When the output voltage V1 of the AC power supply 2 is normally supplied, the trigger signal synchronized with the output voltage V1 is output from the thyristor driving circuit 17 only to the gate of the first thyristor 15 as described above. Therefore,
The first thyristor 15 is turned on, the second thyristor 16 is turned off, and the output voltage V1 from the AC power supply 2 is applied to the load 4.
Is supplied via the first thyristor 15. In the normal state, the drive of the inverter 9 is stopped, and when the potential of the voltage supply line 5 becomes higher than the terminal voltage of the capacitor 13, the diode 24 becomes conductive and the charging circuit 21 , The charging current flows into the capacitor 13 of the filter circuit 11. In this case, the second thyristor 16 is in the off state, and when the potential of the voltage supply line 5 becomes lower than the terminal voltage of the capacitor 13, the diode 24 becomes non-conductive. Charge energy continues to be stored.

On the other hand, when the control circuit 19 detects a drop in the output voltage V1 from the AC power supply 2, the control circuit 19 supplies a drive signal to each switching element of the inverter 9 and the thyristor drive circuit 17 Thyristor
Instead of 15, a trigger signal is output to the gate of the second thyristor 16. When the second thyristor 16 is turned on by a trigger signal from the thyristor drive circuit 17, the energy stored in the capacitor 13 moves to the line 22 via the second thyristor 16, but at this time, the energy is distributed to the line 22. The load 4 of the first thyristor 15 is controlled by the inductor 23.
The oscillating current is supplied to the main terminal connected to the side. Therefore, the inductive or capacitive load 4 is connected to the output terminals 3, 3
A, even if connected between the first thyristor 15 and the load 4 of the first thyristor 15 due to the oscillating current generated on the line 22.
When the power supply line 5 reaches near zero volts, the first thyristor
15 is forcibly turned off, and thereafter the output voltage V2 from the inverter 9 can be supplied to the load 4 side. In addition, at this point, the energy stored in the capacitor 13 is released as the oscillating current of the line 22, so that the filter circuit 11 can exhibit its original function of removing a noise component included in the output voltage V2.

As described above, in the above embodiment, the charging circuit 21 of the capacitor 13 is simply connected to the filter circuit 11 using the capacitor 13 of the existing filter circuit 11 and the inductance (inductor 23) existing on the line 22. The first thyristor 15 is immediately turned off by the oscillating current generated in the line 22 when the voltage of the AC power supply 2 drops, and the inverter 9 is not connected. Can supply the output voltage V2 to the load 4. That is, the instantaneous voltage drop compensating device in the present embodiment includes the first thyristor 15 inserted and connected to one of the voltage supply lines 5 and 5A between the AC power supply 2 and the load 4.
And a second thyristor 16 inserted and connected to one of the output voltage lines 10 and 10 A of the inverter 9.
The first and second thyristors 15 and 16
Is switched on and off to supply the AC output voltage V2 from the inverter 9 to the load 4,
In order to remove a noise component included in the AC output voltage V2 from the AC power supply, at least an instantaneous voltage drop compensator provided with a filter circuit 11 having a capacitor 13 connected between the output voltage lines 10 and 10A. A charging circuit 21 for supplying current to the capacitor 13 is connected to the filter circuit 11, and a line 22 from the capacitor 13 to the first thyristor 15 is connected.
The energy stored in the capacitor 13 using the inductor 23 existing in the first thyristor 15 is used as an oscillating current.
This is a simple circuit configuration in which a charging circuit 21 is provided without separately providing a commutation circuit as in the related art. Can be supplied with the output voltage V2.

A charging circuit 21 for charging the capacitor 13
Although various circuit configurations can be considered, a series circuit of the diode 24 and the resistor 25 is connected to the voltage supply line 5 as in this embodiment.
A capacitor connected between the capacitor and one end of the capacitor 13 is preferable because of the simplest circuit configuration. That is, in the present device, the charging circuit 21 is configured by connecting a diode 24 for preventing backflow and a resistor 25 for limiting current in series between one end of the capacitor 13 and the voltage supply line 5. By simply adding the diode 24 and the resistor 25 to the existing device, when the voltage of the AC power supply 2 drops, the first thyristor 15 is immediately turned off, and the output voltage V2 is supplied from the inverter 9 to the load 4. It becomes possible.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in this embodiment, a bidirectional three-terminal thyristor called a triac is used as a thyristor.
Although 15 and 16 are used, other three-terminal thyristors may be appropriately combined. Also, the first thyristor 15 is connected to the input terminal 1
The second thyristor 16 may be connected to the output voltage line 10A of the inverter 9 while being connected to the voltage supply line 5A between A and the output terminal 3A. Furthermore, the amplitude and cycle of the oscillating current generated from the line 22 can be changed by appropriately adjusting the length of the line 22, the capacity of the capacitor 13, and the like.

[0019]

According to the first aspect of the present invention, the instantaneous voltage drop compensating device is inserted and connected to one of the voltage supply lines between the AC power supply and the load and to one of the output voltage lines of the inverter. A second thyristor that is turned on and off when the voltage of the AC power supply drops to supply an AC output voltage from the inverter to the load by switching on and off of the first and second thyristors. In order to remove a noise component contained in the AC output voltage of the instantaneous voltage drop compensator provided with a filter circuit having at least a capacitor connected between the output voltage lines, an AC current from the AC power supply is supplied to the capacitor. A charging circuit connected to the filter circuit, and an inductor existing on a line from the capacitor to the first thyristor. The energy stored in the capacitor is supplied as an oscillating current to the first thyristor by utilizing the closet, so that a simple charging circuit can be provided without providing a separate commutation circuit. With the circuit configuration, the output voltage can be supplied from the inverter to the load when the output of the AC power supply decreases.

According to a second aspect of the present invention, in the instantaneous voltage drop compensator, the charging circuit includes a diode for backflow prevention and a current limiting resistor connected in series between one end of the capacitor and the voltage supply line. In this case, the output voltage is supplied from the inverter to the load when the output of the AC power supply is reduced by a simple circuit configuration in which a diode and a resistor are simply added to the existing device without separately providing a commutation circuit. be able to.

[Brief description of the drawings]

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

FIG. 2 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 2 AC power supply 4 Load 5, 5 A Voltage supply line 9 Inverter 10, 10 A Output voltage line 11 Filter circuit 13 Capacitor 15 First thyristor 16 Second thyristor 21 Charging circuit 22 Line 23 Inductor (inductance existing in line) 24 Diode 25 resistance

────────────────────────────────────────────────── (5) References JP-A-64-50725 (JP, A) JP-A-63-76340 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02J 9/00-11/00 H03K 17/08

Claims (2)

(57) [Claims] 1. An AC power supply, comprising: a first thyristor inserted and connected to one of voltage supply lines between an AC power supply and a load; and a second thyristor inserted and connected to one of output voltage lines of an inverter. The first and second thyristors are switched on and off when the voltage drops, to supply an AC output voltage from the inverter to the load, and to remove a noise component included in the AC output voltage from the inverter. Wherein at least an instantaneous voltage drop compensator comprising a filter circuit having a capacitor connected between the output voltage lines, a charging circuit for supplying an AC current from the AC power supply to the capacitor is connected to the filter circuit; The capacitor stored in the capacitor is utilized by utilizing the inductance existing in the line from the first thyristor to the first thyristor. An instantaneous voltage drop compensating device configured to supply the obtained energy as an oscillating current to the first thyristor. 2. The charging circuit according to claim 1, wherein the charging circuit includes a diode for backflow prevention and a current limiting resistor connected in series between one end of the capacitor and the voltage supply line. Instantaneous voltage drop compensator.