JPS5820225B2 - Protection device for thyristor rectifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on an abnormality detection signal from a power monitoring device to protect a thyrisk rectifier controlled by a current regulator via a firing angle regulator in the event of a power abnormality. The present invention relates to a protection device for a thyrisk rectifier, which applies an auxiliary input voltage as a pulse shift command signal to a current regulator, moves the thyrisk rectifier to an inverse conversion operation region, and narrows down its output current.

Power supply abnormality of the Cyrisk rectifier, e.g. abnormal voltage drop,
If a single phase short circuit or open phase occurs, disturbances will occur in the current control system, which may cause damage to the Cyrisk rectifier or damage to the load.
When a power supply abnormality occurs, it is desirable to reduce the output current of the Cyrisk rectifier to zero and temporarily evacuate the Cyrisk rectifier.

This can be done by means of a protection device as mentioned at the beginning.

According to this protection device, when the abnormality detection signal from the power supply monitoring device disappears, the Cyrisk rectifier is automatically restarted.

However, in the case of a conventional protection device, an inrush current is generated at the time of restart, and the circuit breaker is tripped by another protection system, so that automatic restart may not actually be possible.

In addition, when a transient voltage imbalance occurs due to a relatively long-term system abnormality, for example, when a furnace transformer connected to the same system is turned on or off, etc., a transient voltage imbalance occurs, especially in one phase. In a situation that corresponds to an open phase, the device that detects the voltage drop may be
In the case of a 0Hz system, an abnormality detection signal is generated at an interval of 10 m5ec, and as a result, the operation of the protection device becomes extremely unstable, and the protection device may not be able to fully perform its function.

SUMMARY OF THE INVENTION An object of the present invention is to provide a protection device that eliminates the above-mentioned problems and avoids tripping of the circuit breaker as much as possible to enable smooth automatic restart.

Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

FIG. 1 is a block diagram showing a control system of a silice rectifier to which a protection device according to the present invention is applied.

According to FIG. 1, the AC input side of the Cyrisk rectifier 3 is connected to the grid via a circuit breaker 1 and a transformer 2, and the Cyrisk rectifier 3 supplies direct current to a load (not shown), such as an electrolysis installation.

The negative charge current actual value is detected via the direct current transformer 4 and the isolation converter 5 and is led together with the current setpoint value set by the setting device 6 to the current regulator 7 .

The output voltage of the current regulator is used as the control input voltage of the firing angle regulator 8.

Firing angle regulator 8 receives, via filter 10, a synchronizing signal obtained from the grid voltage via a voltage transformer (not shown).

The output signal of the firing angle regulator 8 triggers the individual thylisks in the thylis rectifier via a pulse amplifier 9.

Current throttling in the event of a power supply abnormality is performed by shifting the Cyrisk rectifier 3 to the inverse conversion operation mode.

As a pulse shift command signal for causing this transition, an auxiliary input voltage a having a predetermined polarity and magnitude applied to the input terminal of the current regulator 7 as shown in the figure can be used.

FIG. 2 shows an embodiment of the protection device according to the invention applied to the device of FIG.

The power supply monitoring device includes, for example, a rectifier 12 that rectifies the voltage of the synchronous power supply for the firing angle regulator 8 taken out via a transformer 11, a comparator 13 to which the output voltage of this rectifier is applied, and a gate 14. We are prepared.

The output signal of the comparator 13 switches from a "0" signal to a "1" signal when the output voltage of the rectifier 12 falls below a specified value.

Further, a rectifier 16 and a comparator 17 may be provided in the control power transformer 15 that takes out the power for each electronic component shown in FIG. 1, and the comparator output signal may be guided to the NOR gate 14.

The output signal of the comparator 17 switches from a 10" signal to a 1" signal when the output voltage of the rectifier 16 falls below a specified value.

Further, if necessary, an input signal that changes from a 10" signal to a "1" signal in the event of some abnormality in the power supply can be introduced to the NOR gate 14, as shown at 18, for example.

By doing so, a 10'' signal appears at the output terminal of the NOR gate 14 when any power supply abnormality occurs.

The output signal 10 of the NOR gate 14 is a power supply abnormality detection signal of the power supply monitoring device.

A Noah timer (timer) 19 is located after the Noah gate 14.
is connected.

This timer 19 instantaneously changes its output state from 10" to "1" when the input signal "X1" changes from "0" to "0".

On the other hand, when the input signal returns from 10" to 1", the output state returns to 10" after a predetermined time delay.

A monostable element 20 is connected after the timer 19.

When the input signal given by the timer 19 changes from the state 10" to the state 11", the monostable element 20 operates for a certain period of time, regardless of the connection time of the input signal in the state 11". generates an output signal.

The output terminal of the monostable element 20 is connected to one input terminal of a NOR gate 21, and the other input terminal of this NOR gate 21 is connected to the output terminal of the timer 19.

A digital-to-analog converter 23 is connected to the output end of the NOR gate 21 via another NOR gate 22.

The digital-to-analog converter 23 generates a negative polarity voltage only when receiving an input signal in the state of 11''.

The output voltage of the digital-to-analog converter 23 is applied via a delay circuit 24 to the current regulator 7 as an auxiliary input voltage.

The delay circuit 24 can be composed of, for example, a diode D, a low resistance R, and a capacitor C as shown in the figure.

With this configuration, when a negative output voltage of the converter 23 is generated, the capacitor C is rapidly charged to the output voltage value of the converter, but when the output voltage of the converter 23 returns to zero, the blocking of the diode D As a result, the capacitor voltage does not immediately follow the output voltage value of its converter 23, and the capacitor C gradually discharges via the input resistance of the regulator 8.

As shown, the regulator 7 is constructed as a known PI regulator.

Furthermore, another timer 25 is connected to the output terminal of the timer 19, and this timer 25 receives one of the output signals of the timer 19.
When the state of 1" continues for a predetermined period of time, an output signal of 11" is generated, which becomes a trip command signal for the circuit breaker 1 shown in FIG.

The following overall operation is performed by the above configuration and the actions of each part.

When the power supply is in a normal state, the input signals of the NOR gate 14 are all in the state of 50'', so the output signal of the NOR gate is in the state of 1.

The output signal of the timer 19 is "0", the output signal of the monostable element 20 is "0", therefore the output signal of the NOR gate 14 is "11", and the output signal of the NOR gate 22 is "0".
It is in.

Therefore, the output voltage of converter 23 and delay circuit 24 is zero and the auxiliary input voltage of regulator 7 is zero.

In such a state, if some kind of power supply abnormality occurs, for example, an abnormal drop in the power supply voltage, the output signal of the NOR gate 14 changes to 10", which causes the timer 1 to change almost simultaneously.
The output signal of 9 changes to 11".

As a result, the monostable element 20 starts operating and emits a "1" signal, which causes the output signal of the NOR gate 21 to become "0".
changes to the state of

The “0” output signal of the NOR gate 21 is the output signal of the NOR gate 22.
The signal is inverted by 1 and becomes an 11'' signal and is guided to the converter 23.

Upon receiving this 11'' signal, the converter 23 generates a voltage of a predetermined magnitude of negative polarity and transmits it to the delay circuit 24.

At this time, the delay circuit 24 generates a negative voltage that follows the negative voltage of the converter 23 without much delay.

This negative voltage is provided as an auxiliary input voltage to the current regulator 8.

Therefore, the output voltage of the current regulator quickly reaches a saturation voltage that narrows down the actual current value, assuming that the actual current value has significantly increased compared to the current target value.

As a result, the firing angle regulator 8, which receives the output voltage of the current regulator 7 as a control input voltage, shifts the control angle of the thyrisk rectifier 3 to the minimum control advance angle γmin.

As a result, the output current of the Cyrisk converter 3 is quickly narrowed down to zero.

After a certain period of time has elapsed, the monostable element 20 returns to the output state of 0''.

At this time, the power supply abnormality has already been resolved and the node 14
The output signal of the NOR gate 21 returns to 'X 1', and if the timer 19 has already returned to the output state of '0' after a delay recovery time of at least 10m5eC in a 50Hz power supply, for example, the output signal of the NOR gate 21 becomes 11", so that the output voltage of the converter 23 falls stepwise to zero.

As a result, the output voltage of the delay circuit 24, ie the auxiliary input voltage of the regulator 8, gradually attenuates.

In this way, the pulse shift command is gradually released, so that the SiRisk rectifier can smoothly return to normal operation.

If the timer 19 has not returned to the output state of 0" even after the operation time of the monostable element 20 has completed, the respective pulse shift command state continues.

In this case, the pulse shift command state is canceled only when the timer 19 returns to the output state of 0''.

However, even after the timer 19 operates and issues an output signal of 11'', a predetermined time period longer than the operation time of the monostable element 20 has elapsed, the timer 19 still outputs an output signal of 10''.
If the output state does not return to ", the timer 25 operates and issues a trip command for the circuit breaker 1."

In the automatic recovery operation according to the present invention, the delayed recovery operation of the timer 19 and the logic operation of the NOR gate 21 are such that the power supply abnormality detection signal is periodically and repeatedly issued, for example, before a phase loss occurs in the power supply. It comes into effect in certain cases.

For example, if one phase of the power supply is missing in 50H2, 1
A short 10" signal appears periodically at the output end of the NOR gate 14 at intervals of 0 m5ec.

If there is no timer 19, for example 2 of the monostable element 20
After the fixed operating time of 0.00 m5ec ends and the pulse shift command is released, the monostable element 20 is triggered again to start operating and a pulse shift command is issued.

In other words, in this case, following the pulse shift command period of 200 m5ec, there is a pulse shift command release period of \゛10m5ec0', and such pulse shift commands and their cancellations are performed continuously, and therefore the current control Unnecessary disturbances will occur in the system.

In contrast, according to the present invention, the timer 1 performs a delayed recovery operation of at least 10 m5eC in a 50Hz system, for example.
As long as the open phase state continues due to the existence of timer 19
As long as the timer 19 holds the output state of 11", even if the monostable element 20 returns to the output state of 10", the NOAKATE 21 will maintain the output state of "0". 5. There is no change, and the pulse shift command state is connected.

In the case of a recoverable phase loss state, the pulse shift command is canceled after recovery.

In the case of an unrecoverable phase loss state, the timer 25 is activated and the circuit breaker 1 is tripped.

As described above, according to the present invention, the power supply monitoring devices 11 to 1
As soon as a power supply abnormality detection signal is issued from 8, the monostable element 20 is activated based on this abnormality detection signal.

As a result of this operation of the monostable element 20, an auxiliary input voltage is applied from the auxiliary input voltage generation circuits 23, 24 to the current regulator 7 as a pulse shift command signal.

Since this auxiliary input voltage is given to the current regulator at a sufficiently large value with the same polarity as the actual current value derived from the current detector 5, the output signal of the current regulator indicates that the firing angle of the thyrisk rectifier 3 is at the minimum controlled advance. It reaches a saturation value that becomes an angle.

As a result, the output current of the Sirisk rectifier is narrowed down to zero.

If the abnormality detection signal disappears when the fixed operating time of the monostable element 20 ends, a smooth return to normal operation will occur as the auxiliary input voltage gradually attenuates.

On the other hand, if the abnormality detection signal is still connected when the monostable element 20 returns to operation, the second timer element 25 will operate and issue a trip signal for the power supply side breaker 1.

However, this alone is inconvenient when an abnormality detection signal is generated periodically at short intervals, such as when a phase is open.

In other words, without the first timer element 19, the second timer element 25 cannot operate no matter how long the open phase state continues because the abnormality detection signal is not continuous.
When the monostable element 20 returns after a predetermined period of time, the monostable element 20 is activated again by the first abnormality detection signal generated thereafter.

This operation is repeated, that is, the generation and release of the pulse shift command signal are repeated, which causes disturbances in the current control system.

In order to eliminate this inconvenience, first, the first time limit element 19
By inserting , an abnormality detection signal that occurs periodically at short intervals is converted into a continuous signal.

This eliminates any disadvantages to the operation of the second timing element 25.

Also, the output signal of the first time element 19 and the monostable element 20
By creating a pulse shift command signal by ORing the output signals of The signal can be sustained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a control system of a silice rectifier to which the device of the present invention is applied, and FIG. 2 is a block diagram showing an embodiment of the device of the present invention. 1... Breaker, 2... Transformer, 3.
...Sirisk rectifier, 4 ... Current detector, 5 ... Isolation converter, 6 ... Current setting device, 7 ... Current adjustment device, 8... firing angle adjuster, 9... pulse amplifier, 10...
...filter, 11,15...instrument transformer,
12゜16... Rectifier, 13, 17...
... Comparator, 14.2L22 ... Noah gate, 19.25 ... Timer, 20 ...
- Monostable element, 23...Digital-to-analog converter, 24...Delay circuit.

Claims (1)

[Claims] 1. In order to protect the Cyrisk rectifier, which is controlled by the current regulator via the firing angle regulator, in the event of a power failure, a pulse shift command signal is sent to the current regulator based on the abnormality detection signal from the power supply monitoring device. in which the auxiliary input terminal of the thyrisk rectifier is given, the thyrisk rectifier is moved to the inverse conversion operation region and its output current is narrowed down, and the first one is operated by the abnormality detection signal and returns with a delay.
a timed element; a monostable element that is operated for a certain period of time by the output signal of the timed element; and a monostable element that generates the auxiliary input voltage while either the timed element or the monostable element is in operation; an auxiliary input voltage generating circuit that operates to gradually attenuate the auxiliary input voltage only when both of the auxiliary input voltages are restored; and a power supply attached to the thyrisk rectifier that operates with a delay based on the output signal of the first time element. and a second time limit element that issues a trip signal for a side breaker, and the delay operation time of the second time limit element is set longer than the operation time of the monostable element. Device.