JPH0419858Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a direct current or disconnection device using a GTO (gate turn-off) thyristor as a direct current or disconnection element.

B. Overview of the invention In a DC GTO thyristor disconnector where a reverse voltage may be applied from the load side, this invention detects when a reverse voltage is applied to the GTO thyristor by detecting the voltage change between the cathode and anode of the GTO thyristor. By detecting this and cutting off the on-gate current of the GTO thyristor, damage to the GTO thyristor due to reverse voltage application can be reliably and easily prevented.

C. Prior Art Recently, power supply devices that use GTO thyristors as DC cutoff elements have become popular. For example, a configuration in which a GTO shield disconnector is used as a shield breaking element for a DC electric railway is shown in Figure 2. When power is supplied from the main transformer 1 of the substation to the electric vehicle 4 through the rectifier 2 and the feeder line 3, a GTO disconnector 5 is provided between the rectifier 2 and the feeder line 3. 6 is a regenerative inverter of a regenerative substation;
The regenerated output is regenerated through the transformer 7.

The GTO thyristor 5B is connected to the GTO thyristor 5B when the power supply current becomes abnormal due to the control device 5A.
The GTO thyristor 5B is provided with a lightning arrester 5C in parallel to protect it from withstanding voltage in the ignition state.

D Problems to be solved by the invention In the conventional GTO thyristor, the forward overcurrent of the GTO thyristor and the overvoltage in the rupture state are protected by the control device 5A and the lightning arrester 5C. There was a problem that protection against regenerative reverse voltage from the electric car 4, etc. that was being supplied with power was not provided.

For example, in FIG. 2, when the electric car 4 switches from power running to regenerative mode, and the regenerative substation is far from the electric car 4 and the GTO disconnector 5, the A reverse voltage is applied to GTO thyristor 5B.

At this time, there will be no problem if the GTO thyristor 5B is in the OFF state, but if the GTO thyristor 5B is in the ON state where the positive gate current is continuously supplied, the reverse direction from the cathode to the anode side is caused by the application of a reverse voltage. Leakage current flows and power loss is the product of reverse current and reverse voltage in GTO thyristor 5B.
This loss may cause thermal damage to the GTO thyristor 5B.

One idea for this would be to connect a reverse blocking diode in series with the GTO thyristor, but this would result in a large and expensive device in which the diode has a current carrying capacity.

E Means and operation for solving the problem The present invention was made in view of the above problem, and uses a GTO thyristor as a damping element and controls on/off by switching its on-gate current and off-gate current. In the DC GTO shiya disconnector,
It has a reverse voltage detection means for detecting that a reverse voltage is applied from the load side, and a command means for forcibly cutting off the on-gate current of the GTO thyristor when there is a detection signal from this detection means. The voltage detection means includes a thyristor TH whose anode is connected to the cathode of the GTO thyristor, an input element of a photocoupler PC which is inserted in series with the thyristor TH and has a current path on the anode side of the GTO thyristor, and the anode of the thyristor TH. Zener diode ZD inserted between the gates and turns on the thyristor TH by detecting the reverse voltage of the GTO thyristor.
and has a configuration in which a detection output is obtained from the output element of the photocoupler PC, the reverse voltage of the GTO thyristor is detected as a reverse voltage between the cathode and anode by a Zener diode ZD, and this detection turns on the thyristor TH, When this thyristor TH turns on, a current flows through the input element of the photocoupler PC,
This current provides an isolated detection output to the output element of the photocoupler PC.

F. Embodiment FIG. 1 is a main circuit diagram showing an embodiment of the present invention. The GTO thyristor 11 has a gate circuit configured such that an on-gate current and an off-gate current are switched and supplied between the gate G and cathode K from an on-gate power supply 12P and an off-gate power supply 12N via switches 13P and 13N, respectively. Among these, switches 13P and 13N are the control device 14
Opening and closing is controlled by the power supply and stop operation control commands and overcurrent protection commands.

Here, in this embodiment, a protection circuit is provided in case a regenerative reverse voltage is applied from the electric vehicle 4 while the GTO thyristor 11 is in an on state (a state where an on-gate current is supplied). This protection circuit includes a reverse voltage detection circuit 15 provided between the cathode K and anode A of the GTO thyristor 11, and a command means (within the control device 14) that causes the control device 14 to open the switch 13P based on the detection signal of the detection circuit 15. (provided for).

The reverse voltage detection circuit 15 is a GTO thyristor 11
A thyristor whose anode is connected to the cathode K of
TH, a current setting resistor R1 connected in series between the anode and gate of this thyristor TH, a Zener diode ZD for setting the detected reverse voltage, and a current setting resistor _R1 connected in series between the cathode of the thyristor TH and the anode A of the GTO thyristor 11. It consists of a photodiode PD and a current limiting resistor R ₂ that serve as input elements of the photocoupler PC, a diode D ₁ that is connected in antiparallel to the photodiode PD, and a phototransistor PT that serves as an output element of the photocoupler PC.

With this configuration, when the switch 13P is closed and the on-gate current is supplied to the GTO thyristor 11, the thyristor TH is turned off through the diode _D1 , and when the regenerative reverse voltage from the electric car 4 is applied in this state, , when this reverse voltage exceeds the Zener voltage of the Zener diode ZD, the Zener diode
Current flows through ZD, turning on thyristor TH.
As a result, the ON output is taken out to the photocoupler PC,
This ON output causes the command means in the control device 14 to command the switch 13P to open.
3P is opened to cut off the on-gate current,
The GTO thyristor 11 is forced to turn off by applying a reverse voltage when the on-gate current is cut off, and in the turned-off state, reverse voltage is blocked and power loss due to reverse leakage current is eliminated.

Note that when the GTO thyristor 11 is in the OFF state and a regenerative reverse voltage is applied, a similar command is given, but at this time the switch 13P is in the open state, so that the same protection can be obtained. In addition, after the reverse voltage is eliminated, the reverse voltage detection circuit 1
Since the output of the switch 5 is restored and the off command for the switch 13P is also canceled, the switch 13P is controlled to close again and power supply is restarted.

In the above embodiment, in addition to opening the switch 13P when reverse voltage is detected, the switch 13N is closed, thereby supplying an off-gate current to the GTO thyristor 11.
1 may be configured to actively turn off.

G Effect of the invention As described above, according to the invention, it is possible to detect when a reverse voltage is applied to the GTO thyristor from the load side.
The reverse voltage between the cathode and anode of the GTO thyristor is detected by a Zener diode, the thyristor is turned on by this detection, current flows through the input element of the photocoupler, and an isolated detection output is obtained from the output element of the photocoupler. Since the on-gate current of the GTO thyristor is cut off and the turn-off is used to block reverse voltage and leakage current, it is possible to prevent damage to the GTO thyristor due to reverse voltage by simply adding a small amount of inexpensive circuitry.
It has an effect that can be easily prevented.

[Brief explanation of the drawing]

FIG. 1 is a main circuit diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram of an electric railway illustrating a conventional DC GTO switch. 3...Power line, 4...Electric car, 11...GTO
Thyristor, 12P...On-gate power supply, 12N
... Off-gate power supply, 13P, 13N ... Switch, 14 ... Control device, 15 ... Reverse voltage detection circuit, ZD ... Zener diode, PC ... Photocoupler, TH ... Thyristor, PD ... Photodiode, PT ... ...Phototransistor.

Claims (1)

[Scope of utility model registration request] In a DC GTO thyristor which uses a GTO thyristor as a breaker element and controls on/off by switching its on-gate current and off-gate current,
It has a reverse voltage detection means for detecting that a reverse voltage is applied from the load side, and a command means for forcibly cutting off the on-gate current of the GTO thyristor when there is a detection signal from this detection means. The voltage detection means includes a thyristor TH whose anode is connected to the cathode of the GTO thyristor, an input element of a photocoupler PC which is inserted in series with the thyristor TH and has a current path on the anode side of the GTO thyristor, and the anode of the thyristor TH. Zener diode ZD inserted between the gates and turns on the thyristor TH by detecting the reverse voltage of the GTO thyristor.
A direct current characterized by having a configuration in which a detection output is obtained from the output element of the photocoupler PC.
GTO shiya disconnector.