JPH0556663A - Protector for thyristor converter - Google Patents

Abstract

PURPOSE:To protect a thyristor by sending protective gate pulses in the case that the reverse voltage period is insufficient after circulation of an accident current, and sending protective pulses further at the point of time when forward voltage applied subsequently is added in the case that these protective pulses are sent. CONSTITUTION:Protective gate pulses are sent by first protective pulse generating means 18-22 so as to surely prevent the occurrence of partial turn off, in the case that the reverse voltage period after circulation of an accident current is insufficient, when an accident of an overcurrent flowing to the a thyristor 1 occurs. And in the case that these protective pulses are sent, protective pulses are sent further by second protective pulse generating means 24-26 at the point of time when forward voltage applied subsequently is added. Hereby, the thyristor 1 can be protected from the deterioration by forward power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection device for a thyristor converter used in DC power transmission equipment and the like, and more particularly to a protection device for a thyristor converter when a fault current is applied.

[0002]

2. Description of the Related Art In a thyristor converter, a forward voltage is applied after a short reverse voltage period (referred to as an allowance angle γ) after the end of energization, particularly during an inverter operation, so that the allowance angle γ And thyristor turn-off time (called Tq)
During the period, the thyristor converter is operated so that the following relationship is always maintained. γ> Tq + T = γ0 where T is the time considering the variation of γ between thyristors.

When one arm of the thyristor converter is composed of a large number of series thyristors, there is a variation in each Tq, so that in a critical γ operation, only a specific thyristor turns off. The entire thyristor is applied with the entire circuit voltage, resulting in breakdown. In order to avoid this, for example, Japanese Patent Publication No. 54-31660
A gate control circuit as shown in FIG. 2 disclosed in the above publication is used.

One arm of the thyristor converter consists of a number of series-connected thyristors and their associated circuits, one of which is
The part is shown in FIG. In FIG. 2, 1 is a thyristor, 2,
Reference numeral 3 is a voltage dividing resistor and a capacitor connected in parallel with the thyristor. The LEDs 4a and 4b are connected in parallel with the thyristor 1 via the current limiting resistor 5, respectively, and emit forward voltage signals (FV) and reverse voltage signals (RV) respectively, and inside the gate control device via the light guides 6a and 6b. Photoelectric conversion circuit 7
Is transmitted to and converted into an electric signal.

A normal gate pulse is generated as follows. The flip-flop is set by the ON signal ON which is transmitted from the converter controller (not shown) and reset by the OFF signal OFF. Flip flop 8
When is set, its output is another flip-flop 9
Is set, and the signal PHS0 becomes "1". F mentioned above
The V signal and the signal PHS0 are logically ANDed by the AND gate 10, and the output is pulsed by the mono-multivibrator 11 and amplified by the amplifier 12,
It drives the base of the switching transistor 13.

The same number of thyristor firing LEDs 141 to 14n as the series thyristor 1 are connected in series with the power supply capacitor 15, the current adjusting impedance 16 and the transistor 13. Therefore, when the transistor 13 is driven, a current flows through the LEDs 141 to 14n and is transmitted to the thyristor 1 via the light guide 17 as an optical gate pulse. Here, the thyristor 1 is assumed to be a light direct ignition type, and the thyristor 1 is ignited by the optical gate pulse.

On the other hand, when the reverse voltage period is less than the predetermined value, the protection gate pulse is generated as follows. FIG. 3 shows the thyristor voltage, FV signal, RV signal, PHS0 signal and gate pulse command during inverter operation. When the back pressure period γ after the end of the conduction period is equal to or greater than the predetermined value γ0, the flip-flop 8 is reset by the on-delay, so that the PHS0 signal becomes "0" as shown by the broken line, and the protection gate pulse is not output. However, when γ is smaller than γ 0, a forward gate voltage is applied and at the same time a protection gate pulse is output and all thyristors are fired.

[0008]

The conventional protection device for a thyristor converter has the following drawbacks.

That is, such as an arm short circuit or a DC short circuit,
When an accident in which an excessive current flows through the thyristor converter occurs, a gate block is generally used to protect the thyristor converter. Normally, after a reverse voltage is applied for 1.5 to 2 ms after a fault current flows, a forward voltage is applied, so that all thyristors can be turned off and gate blocking is possible. However, when the system voltage is distorted due to overlapping of opening and closing of the phase adjusting equipment, the reverse voltage period may become shorter than usual. In such a case, a thyristor that partially turns off may occur as described above.To prevent this, when γ is smaller than a predetermined value, the protection gate is applied when the forward voltage is applied.
Pulse must be output to protect the thyristor.

The thyristor causes a fault current to flow,
The junction temperature becomes higher than that during normal operation. The turn-off time (Tq) has a remarkable temperature dependency, and increases as the temperature rises. Therefore, with the setting of the reverse voltage period during normal operation, the case in which there is a thyristor that partially turns off and a thyristor that does not turn off cannot be completely prevented, and sufficient protection cannot be performed. ..

Therefore, the present invention has been made in order to solve the problem of the conventional protection device for a thyristor converter, and can reliably protect against partial turn-off even in the case of an accident such as an arm short circuit. It is an object of the present invention to provide a protection device for a thyristor converter that can achieve the above.

[0012]

In order to achieve the above-mentioned object, the present invention comprises at least a plurality of series-connected thyristors constituting an arm which constitutes a thyristor converter, and the reverse operation after the conduction period of the arm is completed. When the voltage application period is less than or equal to a predetermined value, in the protection device of the thyristor converter having protection means for generating a protection gate pulse each time a forward voltage is applied to the arm after the conduction period ends, the thyristor converter has an excessive voltage. When an accident occurs in which a current flows, when the reverse voltage application period after the conduction period of the arm is equal to or less than a desired value larger than the predetermined value, the forward voltage is applied to the arm after the conduction period is terminated. When the first protection pulse generating means for generating a protection gate pulse and the first protection pulse generating means operate, the first protection pulse generating means operates until the AC side breaker of the thyristor converter trips. It is characterized in that comprising a second protective pulse generating means for generating a Toparusu - forward voltage arm protection gate each time it is applied.

[0013]

According to the present invention, when the reverse voltage period is insufficient after the fault current flows, the first protection pulse generating means is used to surely prevent the partial turn-off from occurring.
Pulse is generated, and when this protection gate pulse is generated, the protection pulse is further generated by the second protection pulse generating means when the forward voltage applied subsequently is applied to protect the thyristor from deterioration due to the forward voltage. To do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1, which shows the same parts as those in FIG.

The configuration of FIG. 1 is different from the conventional configuration of FIG. 2 in that it includes first protection pulse generating means for generating two protection pulses and a second protection pulse generating means.
The protection pulse generating means is added. The first protection pulse generating means is a flip-flop 18, an inversion gate.
It is composed of a gate 19, an oaget 20, an and gate 21, and a mono-multi vibrator 22.

The flip-flop 18 is set at the same time as the flip-flop 8 is set, and the output from the margin angle γ1 and the inversion gate 19 of the arm short circuit detection signal becomes the input of the OR gate 20. Reset by output. The output of the flip-flop 18 is AND gate
The FV signal is logically ANDed by the gate 21 and its output is converted into a one-shot by the monomultivibrator 22 and becomes the input of the oaget 23. On the other hand, the second protection pulse generating means is composed of a flip-flop 24, an AND gate 25, and a mono-multivibrator 26.

The flip-flop 24 is set by the output of the AND gate 21, and reset by the trip signal (CB TRIP) of the circuit breaker. The output of the flip-flop 24 is logically ANDed with the FV signal by the AND gate 25, and the output is a mono-multi vibrator.
It is converted into a one-shot by the data 26 and becomes an input to the oaget 23.

With the above construction, when an arm short circuit occurs, the arm short circuit detection signal is transmitted, and the output of the inverting gate 19 becomes "0". At this time, if the reverse voltage period is γ1 or more, the flip-flop 18 is reset. Therefore, if the reverse voltage period is γ1 or less, the flip-flop 18 is not reset and the output remains "1" because no protection pulse is output. Becomes Therefore, when forward voltage is applied to the thyristor again and FV signal comes,
Since both inputs of the switch 21 are "1", the output thereof is "1", and the mono-multivibrator 22 operates to output the protection pulse. Further, the output of the AND gate 21 becomes a set signal of the flip-flop 24. Since the output of the flip-flop 24 is ANDed with the FV signal, after the protection gate pulse is output once after the arm short circuit,
The situation in which the protection gate pulse is output whenever the FV signal comes in is until the AC side circuit breaker of the thyristor converter trips, that is, the flip-flop 24 by the CB TRIP.
Continues until is reset.

As described above, an arm short circuit occurs,
If the reverse voltage period is shorter than .gamma.1 after passing one wave of fault current, according to the invention, a protective gate pulse is issued. The value of γ1 is selected according to the condition that the junction temperature of the thyristor after the fault current is applied is high.
It can always be protected in larger situations where a protective gate pulse is needed.

Furthermore, an arm short circuit occurs and the protection gate
After the occurrence of the gate pulse, if the forward voltage is applied until the breaker trips, the gate pulse is always output, so the thyristor is not deteriorated by the forward voltage.

Although the arm short circuit has been described above, the same applies to a DC short circuit. Although only one thyristor is shown in FIG. 1 as a representative, when a plurality of FV and RV signals are output to a plurality of thyristors, they are OR-combined and their outputs are explained here. FV or RV
It may be used as a signal. The first and second protection pulse generating means are not limited to the logic circuit shown in FIG. 1 and can be implemented with various design changes.

[0022]

As described above, according to the present invention,
It is possible to provide a thyristor converter protection device that can reliably protect a thyristor even when the margin angle is insufficient when a system short circuit occurs.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a conventional device.

FIG. 3 is a waveform diagram for explaining a protection operation of the thyristor converter.

[Explanation of symbols]

1 ... Thyristor 4 ... LED for forward voltage and reverse voltage 6 ... Light guide 8,9,18,24 ... Flip-flop 20,23 ... Ogate 10,21,25 ... And gate

Claims (1)

[Claims] 1. An arm constituting a thyristor converter is composed of at least a plurality of series-connected thyristors,
When the reverse voltage application period after the end of the conduction period of the arm is less than or equal to a predetermined value, protection of the thyristor converter provided with a protection means for generating a protection gate pulse each time a forward voltage is applied to the arm after the conduction period ends In the device, when an excessive current flows in the thyristor converter, when the reverse voltage application period after the end of the conduction period of the arm is equal to or less than a desired value larger than the predetermined value, the arm after the conduction period ends. A first protection pulse generating means for generating a protection gate pulse when a forward voltage is applied to the first protection pulse generating means, and the AC side circuit breaker of the thyristor converter when the first protection pulse generating means operates. A protection device for a thyristor converter, comprising a second protection pulse generating means for generating a protection gate pulse each time a forward voltage is applied to the arm until a trip occurs.