JPH02276419A - Vbo free thyristor conversion device - Google Patents

Abstract

PURPOSE:To suppress the overvoltage applied to a thyristor valve appropriately by tripping a gate block of the thyristor valve or a circuit breaker so long as the point in time when the number of times for ignition VBO of a thyristor valve detected by a comparator that it is more than the number indicated by a setter is within the specified time limits. CONSTITUTION:When the third ignition VBO is caused within 50ms from the first ignition VBO, a counter 21 counts '3' and a comparator 23 compares it with '3' indicated by a setter 23 to output '1' and sets the output of an FF 20 to '1'. Consequently, the output of an OR circuit 25 becomes '1' and the output of an inversion circuit 26 '0'. Then the output of an AND circuit 27 will be '0', because the input on one side of it becomes '0'. Thyristor valves are gate-blocked for all phases. When each thyristor valve extincts all arcs, AC phase voltage is applied to thyristor valves, so that no ignition VBO will be caused to them.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a thyristor conversion device used in DC power transmission, a reactive power compensator, etc., which is configured with a VBO-free thyristor having an overvoltage protection function.

(Prior Art) Electric thyristors or optical thyristors have been used in thyristor conversion devices such as direct current power transmission (hereinafter referred to as HVDC) and var power compensator (hereinafter referred to as SvC). Since these thyristors do not have an overvoltage suppression function on their own, overvoltage has been suppressed using arresters or overvoltage protection circuits.

On the other hand, recently, a thyristor, a so-called VBO-free thyristor, which can protect itself against forward overvoltage by a self-ignition (VBO ignition) function has been put into practical use, and is now being applied to a thyristor conversion device.

This makes it possible to omit an overvoltage protection circuit or an arrester.

However, self-ignition of the VBO free thyristor is not allowed for VBO firing every cycle (continuous VBO firing) for thermal reasons, and VBO firing of several cycles is the limit. On the other hand, the overvoltage determined by the system extends over several cycles to hundreds of cycles (this varies depending on the system conditions). Therefore, if the overvoltage continues for a long time, the VBO free thyristor will be damaged.

These will be explained using FIGS. 6, 7, and 8.

Figure 6 shows the overall configuration of a converter system using VBO-free thyristors for HVDC, and Figure 7 shows its VBO
One arm of a converter using an O-free thyristor (hereinafter referred to as a thyristor valve or valve) and its gate pulse generator (hereinafter referred to as PG) are shown.

IU to IZ are thyristor valves, 2 is a DC reactor,
3 is a transformer for the converter, and 4 is a circuit breaker that connects the converter to the AC system.

Further, 5 is a VflO free thyristor, 6 and 7 are snubber circuit resistors and capacitors, 8 is a DC voltage dividing resistor, 9
is a suppression reactor for di/dt and dv/dt suppression. 10 is a light guide for transmitting the gate optical signal from the PG to the thyristor valve. 11 is a light emitting element for generating a light gate, and 12, 13, and 14 are switching elements, resistors, and DC power supplies for driving the light emitting element.

The switching element 12 receives a gate command signal, au (signal au may be either a conduction command signal itself from a converter control device (not shown) or an AND signal of a conduction command signal and a forward voltage signal of a valve (not shown). ,) With this configuration, when the switching element 12 is operated by the gate command signal au, the light emitting element 11 and the light guide 10 are activated.
A gate light signal is supplied to each VBO free thyristor 5 in the thyristor valve through the thyristor valve, and all the VBO free thyristors 5 of the U-phase valve fire at the same time. The thyristor valve therefore becomes conductive.

(Problem to be solved by the invention) Figure 8 shows that the system voltage increases for some reason and VBO
Indicating the case of ignition (example of inverter operation) t=T
In the example where system overvoltage occurs at , t is normal operation (
Normal ignition), overvoltage operation (VBO
ignition).

In this case: t) If the overvoltage firing period (or number of firings) of T1 exceeds the limit of the VBO free element, the VBO free element will be completely damaged.

As described above, if a VBO-free thyristor is directly applied to a thyristor converter, the above-mentioned serious accident will occur.

The present invention was made in view of the above-mentioned drawbacks, and detects the overvoltage protection firing of the VBO free thyristor, and depending on the number of firings, performs gate blocking, breaker release, or restart, etc., and damages the VBO free thyristor. It is an object of the present invention to provide a VBO-free thyristor conversion device that can appropriately suppress overvoltage applied to a thyristor valve without causing damage to the thyristor valve.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a thyristor valve composed of a VBO free thyristor, and an LED for igniting the thyristor valve.
, a power supply and switching element that drives the LED,
A light guide that transmits optical gate signals, Vlloll-
VBO firing detection circuit that detects VBO firing of thyristor valve, counter that counts the number of VBO firings, continuous VB
It consists of a timer for detecting O ignition, a setter for setting a criterion for determining whether the number of VBO ignitions is too large, and a comparator for comparing the counter output number with the set number indicated by the setter.

(Function) The timer starts measuring a certain period of time after the VBQ firing of the thyristor valve begins to occur, while the counter starts counting the number of VBO firings of the thyristor valve and indicates that the number is greater than the number indicated by the setting device. If the time detected by the comparator is within a predetermined time, it is assumed that the thyristor valve has fired Vllo a predetermined number of times in succession, and the gate block or circuit breaker of the thyristor valve is tripped.

(Example) An example of an embodiment of the present invention will be described below, in which, for example, a thyristor valve is gate-blocked when the thyristor valve is VBO-ignited three or more times in a row. FIG. 1 is a diagram showing one embodiment of the present invention, showing a U-phase iris valve and its gate pulse generator.

Elements having the same functions as those in FIG. 7 are denoted by the same reference numerals, and explanations thereof will be omitted.

15 is a light emitting element for snubber current detection, 16 is a light emitting element 1
5 is an anti-parallel connected diode, 17 is a light guide, 1B is a photoelectric conversion circuit, 19 is an AND circuit,
These circuits constitute the VBO ignition detection circuit of the thyristor valve.e VBo free thyristor 5 is the VBO
When igniting, the turn-on occurs from a higher forward voltage than during normal operation, so the discharge current of the snubber capacitor 7 flowing through the light emitting element 15 at this time is as follows.

It becomes larger than during normal operation, and the light emitting element 15 emits light strongly. Therefore, by setting the light reception detection level of the photoelectric conversion circuit 18 to a predetermined value, VB
When the O free thyristor 5 fires, the photoelectric conversion circuit 18 does not operate and the VBO free thyristor 5
The photoelectric conversion circuit 18 constitutes a circuit that operates only when the light is ignited. The AND circuit 19 performs a logical product of the VBG firing detection signals of the thyristor valves constituting the U-phase valve, thereby obtaining the VBO firing detection signal VU as the U-phase valve.

20 is a one-shot circuit that plays the role of a timer, and input v
When U changes from “0” to 1”1”, the output is ((0
” to “’1” for a predetermined T seconds II I IP
The state is maintained and changes from 1'' to "0" after T seconds. In this embodiment, the value of T is determined based on the frequency of the AC system because it is detected when the via ignition occurs three or more times in a row. The value shall be at least 2 cycles and less than 3 cycles.

In this embodiment, the frequency of the AC system is 507, and the value of T is 50+ns. 21 is the valve VB at the counter
The number is counted every time the O firing signal VU is input, but when the output of the one-shot circuit 20 changes from "1" to "0", the count is all cleared. 22 is a setting device which is set to 3 times in this embodiment. 23 is a comparator; when the output of the counter 21 is less than the set value of the setter 22, the output of the comparator 23 is 0''; when the output of the counter 21 is more than the set value of the setter 22, the output of the comparator 23 is re.
1 tt. 24 is a flip-flop for latching signals. When the output of the comparator 23 becomes "1", the U-phase valve VBO protection signal PU, which is the output of the flip-flop 24, becomes 11171. 25 is an OR circuit, and U
vB of phase valve.

In addition to the protection signal PU, the VBO protection signals of the valves of other phases are configured by similar circuits (not shown), that is, the VBO protection signal pv of the V-phase valve, the VBO protection signal pw of the w-phase valve, and the VBO of the x-phase valve. Protection signal px, y-phase valve VBO protection signal py, z-phase valve Veo protection signal P
Create a logical sum of Z. 26 is an inverting circuit that inverts the output of the OR circuit 25;

27U to 27Z are two-man powered AND circuits, one input receives the output signal of the inverting circuit 26, and the other input receives the gate command signal aU of the thyristor valve of each phase.
”aZ is input and logical product is performed.

The output of the AND circuit 27U is input to the switching element 12 that drives the light emitting element 11 for generating a light gate of the U-phase bulb. The outputs of the AND circuits 27V to 27Z are input to a switching element (not shown) that drives a light emitting element for generating an optical gate, similarly to the U phase.

The effect will be explained in the case where the VBO free thyristor valve fires only once, such as in the case of a temporary surge. When the VBO-free thyristor 5 of the U-phase thyristor valve fires in VBO, the optical signal from the light emitting element 15 passes through the light guide 17 and operates the photoelectric conversion circuit 18, and the output VU of the AND circuit 19 becomes 1" in a pulsed manner and the counter is activated. 21 counts 1. Since the value indicated by the setter 22 is 3, the output of the comparator 23 is 0". On the other hand, the one-shot circuit 20 counts 50 when VU becomes "1".
Generates a one-shot pulse between w. This 50ff1
Since the second VBO ignition does not occur during s, the UV
The signal does not become "1". Then, the output of the counter 21 remains 1, and the output of the comparator 23 is gt On.

Therefore, the output Pun of the flip-flop 24 is "O", and the output of the OR circuit 25 is also "0". Therefore, the output of the inverting circuit 26 is "1", and the AND circuits 27U to 27
Z gives a signal according to the gate command signal aU-aZ of each phase to the switching element 12, and each valve is not gate-blocked.The pulse generated by the one-shot circuit 20 is 5.
When changing from 111" to tt O" after 0m5, the count number of the counter 21 is reset.

Next, a case where the overvoltage determined by the system continues for several cycles will be explained using FIGS. 1 and 2.

First, when the first VBO ignition occurs, the counter 21 reads “
1". Next, the comparator 23 compares it with the value indicated by the setter 22 and outputs 11 Orl. On the other hand, 929
The output of the 128 circuit 20 generates a one-shot pulse for 50m5 from the time when the first VBO ignition signal VU becomes 111''.The output of the comparator 23 is 0'', so it is a temporary pulse. As in the case of surge, the thyristor valve is not gate blocked. Next, when the second VBO ignition occurs, the counter 21 counts 412 II, but the comparator 23 compares it with "3" indicated by the setting device 22 and outputs 0, so the thyristor valve is also gated. Not blocked.

Furthermore, when the third VBO firing occurs within 50 m5 from the first VBO firing, the counter 21 counts "3" and the comparator 23 compares it with '3' indicated by the setting device 22.
N, and the output of flip-flop 2o is 1t1u.
Set to . Therefore, the output of the OR circuit 25 is II 17
1, the output of the inverting circuit 26 becomes 0'', and one input of the AND circuit 27 becomes 0'', so the output of the AND circuit 27 becomes 0, and all phases of the thyristor valves are gate-blocked. Thyristor valve is gate blocked,
When all the thyristor valves are extinguished, an alternating current phase voltage is applied to the thyristor valves, and since this value is 1/VB compared to the line pressure, the thyristor valves are at the VBO point. There will be no arc.

As described above, according to the embodiment of the present invention, VB.

Continuous VB of thyristor valve using free thyristor
It is possible to reduce the number of O ignitions to 3 times or less, and the VBO
It is possible to provide a VBO free thyristor converter that can effectively suppress the overvoltage of the thyristor valve without exceeding the allowable overvoltage protection period of the free thyristor 1 and therefore without destroying the thyristor valve.

FIG. 3 shows another embodiment of the present invention. According to this embodiment, when a thyristor valve causes continuous VBO ignition more than a predetermined number of times, the gates of all valves are blocked and the output of the OR circuit 25 is performed. The signal is used to issue a signal to trip the circuit breaker 4, so that the alternating current voltage applied to the thyristor valve becomes non-voltage, and overvoltage of the thyristor valve can be suppressed.

FIG. 4 shows another embodiment of the invention. The output of the OR circuit 25 is input to an on-delay circuit 28 that is delayed by a predetermined time that is considered to sufficiently attenuate the overvoltage determined by the system, and the output of the on-delay circuit 28 is input to a one-shot circuit 29 for generating a reset pulse. 29 resets the flip-flop 24. When the flip-flop 24 is reset, the output of the OR circuit 25 becomes 14011 and the output of the inverting circuit 26 becomes #I11, so that the gate block of the thyristor valve is released and the converter can be operated.

Therefore, according to FIG. 4, when the thyristor valve is continuously turned on by VBO more than a predetermined number of times, the overvoltage applied to the thyristor is suppressed by gate blocking the thyristor valve, and the gate blocking is automatically released after a predetermined time. , can provide a restartable thyristor converter.

FIG. 5 shows another example of the present invention. Components showing the same operations as those in FIG. 4 are designated by the same reference numerals, and explanations thereof will be omitted.

The output of the on-delay circuit 28 is transferred to the one-shot circuit 29.
At the same time, it is input to another one-shot circuit 30. The one-shot circuit 30 is a circuit that generates a pulse for a predetermined period of 10 seconds when the input signal changes from ti Oyt to 1'''.

The output signal of the one-shot circuit 30 and the output signal of the AND circuit 19 are input to an AND circuit 31. The signal from the AND circuit 31 is used as a trip command for the circuit breaker 4. Also,
The signal from the AND circuit 31 is inputted to an OR circuit 258 via a flip-flop 32 and an OR circuit 32.

According to this embodiment, the overvoltage applied to the VBO-free thyristor is suppressed by gate-blocking the thyristor valve 1 when the thyristor valve 1 continuously fires the VBO a predetermined number of times or more, and the gate is automatically blocked after a predetermined time. To release (deblock), the converter can be restarted, and if thyristor valve 1 fires at VBO again within a predetermined time (To) after the converter is restarted, all thyristor valves are gate-blocked again. At the same time, the circuit breaker 4 trip command is sent to make the AC voltage of the thyristor valve 1 non-voltage, thereby suppressing the overvoltage of the thyristor valve 1.

In Figures 1, 3, 4, and 5, 19 is an AND circuit to detect the VBO firing as a thyristor valve;
Overvoltage suppression may be performed for continuous VBO ignition in units of O-free thyristors.

〔Effect of the invention〕

As explained above, according to the present invention, the overvoltage protection firing of the VBO free thyristor is detected, and depending on the number of firings, the gate is blocked, the breaker is opened, or the restart is performed, without destroying the VBO free thyristor. VBO that can appropriately suppress overvoltage applied to the thyristor valve
A free thyristor conversion device can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a diagram for explaining the operation of FIG. 1, and FIGS. 3 to 5 show other different embodiments of the present invention. Block diagram, 6th
The figure is an overall configuration diagram of a thyristor conversion device for DC power transmission.
The figure is a block diagram of one arm and a gate pulse generator of a conventional thyristor converter for DC power transmission, and FIG. 8 is a time chart for explaining the operation of FIG. 7. 5...VBO thyristor, 7...Capacitor 6
．． 8.13... Resistor 9... Anode reactor 10, 17... Light guide, 12... Switching element, 16... Diode, 19... AND circuit, 21... Counter, 23 ...Comparator. 25...OR circuit.

Claims (4)

[Claims] (1) In a V_B_O free thyristor conversion device using a V_B_O free thyristor as a switching element, means for detecting that the overvoltage protection firing of the V_B_O free thyristor has occurred a predetermined number of times or more in a predetermined period; V_B_O comprising means for blocking the gate of the free thyristor conversion device
Free thyristor conversion device. (2) In a V_B_O free thyristor conversion device using a V_B_O free thyristor as a switching element, means for detecting that the overvoltage protection firing of the V_B_O free thyristor has occurred a predetermined number of times or more in a predetermined period; A V_B_O free thyristor converting device comprising means for blocking a gate of the free thyristor converting device and opening an AC side disconnector of the V_B_O free thyristor converting device. (3) In a V_B_O free thyristor conversion device using a V_B_O free thyristor as a switching element, means for detecting that the overvoltage protection firing of the V_B_O free thyristor has occurred a predetermined number of times or more in a predetermined period; A V_B_O free thyristor conversion device comprising means for blocking a gate of the free thyristor conversion device and means for releasing the gate block when a predetermined time has elapsed after the gate has been blocked. (4) In a V_B_O free thyristor conversion device using a V_B_O free thyristor as a switching element, means for detecting that the overvoltage protection firing of the V_B_O free thyristor has occurred more than a predetermined number of times in a predetermined period; means for blocking the gate of the free thyristor conversion device; and means for releasing the gate block when a predetermined period of time has elapsed after blocking the gate;
The V_B_O is set again within a predetermined time after the gate block is released.
A V_B_O free thyristor converter comprising means for blocking the gate again and opening the AC side or disconnector of the V_B_O free thyristor converter when the free thyristor is activated for overvoltage protection.