JPH04344121A - Control angle malfunction detector for thyristor valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control angle abnormality detection circuit for a thyristor valve used in DC power transmission and the like.

0002

[Prior Art] Thyristor valves used for DC power transmission, etc. generally have a firing angle of about 10 to 20 degrees during continuous operation for reasons such as reducing the arrester protection level, reducing the number of series connections, and reducing the snubber resistance capacity. It is designed to operate continuously at an electrical angle of about 10 to 20 degrees (hereinafter simply referred to as degrees) or a margin angle of about 10 to 20 degrees (hereinafter simply referred to as degrees).

0003

However, when the thyristor valve is activated, when the power flow is reversed, or when an accident occurs, it is unavoidable to operate the thyristor valve at the firing angle α1 near 90 degrees for a short period of time. Therefore, since the firing angle is generally controlled by the control device, a timer or the like is used to prevent the value of the firing angle α commanded by the control device from taking a value near 90 degrees for a predetermined period of time or more. ing. The closer the firing angle α is to 90 degrees, the larger the voltage peak value applied to the thyristor valve becomes.
Arrester stress increases. Furthermore, since the snubber resistance loss is given by equation (1), the snubber resistance loss increases as the firing angle approaches 90 degrees. Loss = 39.44f2 ×Cd2 (UiM/k)2
×(3/1-31/2 /8π× cos2α)×R
d×Kr +0.875f×Cd×(UiM/k)
2 [sin2 α+ sin2 (α+u)]×K
r...(1) f: Power supply frequency (Hz) u: Overlap angle (radian) Cd: Surge absorption capacitor (F) Rd: Surge absorption resistor (damping resistance) (Ω) k: Series C
Number of pairs of d and Rd (number of series thyristors) Kr: Total C
d, Rd number of sets (total number of thyristors)

However, due to some reason, such as an abnormality in the timer on the control panel, even if the operation continues for a long time with the firing angle near 90 degrees, the firing angle α
Since there is no means to detect abnormalities in the arrester, there is a risk of thermal runaway of the arrester or burnout of the snubber resistor. Furthermore, there was a possibility that the arrester stress would increase, leading to thermal runaway or destruction of the arrester. In addition, operation when α is around 90 degrees consumes a large amount of reactive power, destabilizing the system, and increases radio noise because the valve turn-on voltage is high.

An object of the present invention is to provide a control angle abnormality detection circuit for a thyristor valve that is capable of detecting an abnormality and generating an abnormal signal when operation continues with the firing angle α being around 90 degrees. It is about providing.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a voltage detection circuit that detects at least one of a forward voltage and a reverse voltage of a thyristor valve, and an output of the voltage detection circuit that detects a voltage of the thyristor valve. The first detects that the voltage application period is longer than a predetermined period in one cycle.
a time detection circuit; an AND circuit that outputs a signal when a signal indicating that the thyristor valve is in operation and a signal from the first time detection circuit are both input;
The device also includes a second time detection circuit that outputs a voltage abnormality signal when the output of the AND circuit continues for a predetermined period or more every cycle.

[0007]

[Operation] According to the present invention, when it is detected that the voltage application period of the thyristor valve is longer than a predetermined period in one cycle, and the thyristor valve is in operation, the signal generated is If it continues for a predetermined period or more, it will be output as a voltage abnormality signal, so if the firing angle α is 90
If operation continues in the vicinity of 100°C, the abnormality can be detected.

[0008]

Embodiment A schematic configuration of an embodiment of the present invention will be described below with reference to FIG. 1 conceptually represents one arm of a thyristor valve, which consists of a series circuit of a thyristor 2, a snubber resistor 3 connected in parallel to the thyristor 2, a snubber capacitor 4, and a series circuit connected in parallel to the thyristor 2. The current limiting resistor 5, the forward voltage detecting LED 6 of the thyristor valve 2, and the reverse voltage detecting LED 7 of the thyristor valve 2 are connected in parallel.

8 and 9 are LEDs 6 for forward voltage detection, respectively.
and a light guide that transmits the optical signal from the reverse voltage detection LED 7; 10 and 11 are photoelectric conversion circuits that convert the optical signals from the light guides 8 and 9 into electric signals FV and RV, respectively; and 12 is a photoelectric conversion circuit with a predetermined firing angle. A first on-delay circuit turns on after a time limit T1 to detect that the firing angle is greater than or equal to a predetermined value, and a second on-delay circuit 13 turns on after a time limit T2 to detect that the firing angle is less than a predetermined value. , 14 is a first off-delay circuit that turns off after time limit T3 to make the output signal of the on-delay circuit 12 continuous; 15 is a first off-delay circuit 13;
16 and 17 are AND circuits, and 18 is an on-delay circuit that is turned on after a third time period T5 to make the output signal continuous.

Here, the first on-delay circuit 12 constitutes a first time detection circuit of the present invention, the second on-delay circuit 13 constitutes a second time detection circuit of the present invention, and the first on-delay circuit 12 constitutes a first time detection circuit of the present invention. The second off-delay circuits 14 and 15 and the third on-delay circuit 18 constitute a third time detection circuit of the present invention.

Here, the time limit T1 of the first on-delay circuit 12 is a value obtained by adding a predetermined margin Δα1 to the maximum continuous control angle α1 during rectifier operation determined by the system. The time limit T2 of the second on-delay circuit 13 is 120 which is the minimum continuous control angle α2 during inverter operation determined by the system from 360 degrees, the predicted minimum overlap angle U, a predetermined margin, and the energization period. This is the value after subtracting the degree. In other words, it is the value obtained by adding a predetermined margin to the maximum continuous margin angle γ determined by the system. In addition, the time limits T3 and T4 of the first and second off-delay circuits 14 and 15 are set at almost the commercial frequency in order to make the outputs continuous, since the outputs of the off-delay circuits 14 and 15 are intermittent signals based on the commercial frequency. be equal to the period of Further, the time limit T5 of the third off-delay circuit is set to a value obtained by adding a slight margin to the maximum continuous operation time in the vicinity of the firing angle of 90 degrees determined based on the system requirements, for example, the margin angle advance time.

Next, the operation of the embodiment configured as described above will be explained with reference to the time charts of FIGS. 2 and 3. As shown in FIG. 2, when the thyristor valve 1 is normally operating as a rectifier, the firing angle α is around 20 degrees, so the light signal detected by the forward voltage detection LED is transmitted to the light guide 8. The width of the electrical signal converted by the photoelectric conversion circuit 10, that is, the forward voltage signal FV of the thyristor valve 1, is about 20 degrees, which is narrower than the time limit T1 of the on-delay circuit 12, so the signal a becomes "0". , the output c of the off-delay circuit 14 remains at "0".

On the other hand, when the rectifier is in operation, the reverse voltage detection LE
The width of the electrical signal converted from the optical signal detected by D by the photoelectric conversion circuit 11 via the light guide 9, that is, the reverse voltage signal RV of the thyristor valve 1, is sufficiently longer than the time limit T2 of the off-delay circuit 13, so that the signal b repeats “1” and “0” at the commercial frequency cycle. Therefore, the output d of the off-delay circuit 15 becomes "1". Therefore, since one input of the AND circuit 16 is "0" and the other is "1", the output e is "0". One input signal f of the AND circuit 17, that is, the deblock signal DEB (a signal indicating that the thyristor valve 1 is in operation) is always "1" when the thyristor valve 1 is operating φ, but the other input signal e That is, since the output of the AND circuit 16 is "0", its output g also becomes "0". Therefore, the output h of the on-delay circuit 18 also becomes "0", and no control angle abnormality signal is output.

Now, consider the case where the firing angle α approaches 90 degrees. As shown in FIG. 3, when the firing angle α approaches 90 degrees, the width of the forward voltage signal FV becomes wider, and when it exceeds the time limit T1 of the on-delay circuit 12, the on-delay circuit 12
The output a of the off-delay circuit 14 repeats "1" and "0" at the cycle of the commercial frequency, and the output c of the off-delay circuit 14 becomes "1".
becomes.

On the other hand, the reverse voltage signal RV is also similar to that shown in FIG. 2, and the output d of the off-delay circuit 15 is "1". Therefore, the output e of the AND circuit 16 becomes "1", and the output of the AND circuit 17 also becomes "1". Therefore, when the firing angle α is close to 90 degrees, the on-delay circuit 1
If it continues for more than the time period T5 of 8, the output signal h becomes “1”.
Therefore, a control angle abnormality signal is output, and necessary protection is provided by a protection circuit (not shown).

Note that while the thyristor valve 1 is floating, the widths of the forward voltage signal FV and the reverse voltage signal RV are both 1.
80 degrees, and the output signal e of the AND circuit 16 becomes "1", but since the deblock signal f is "0",
The signal g is "0", the signal b is "0", and no control angle abnormality signal is output.

[0017] The above has been explained for the case of rectifier operation, but also for the case of inverter operation.
The operation is the same except that the relationship between the forward voltage signal FV and the reverse voltage signal RV is reversed.

[0018]

[Effects of the Invention] According to the present invention described above, the firing angle is 9
It is possible to provide a control angle abnormality detection circuit for a thyristor valve that can reliably detect an abnormality and generate an abnormality signal when operation near 0 degrees continues.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a control angle abnormality detection circuit for a thyristor valve according to the present invention.

FIG. 2 is a time chart showing the operation of FIG. 1;

FIG. 3 is a time chart showing the operation of FIG. 1;

[Explanation of symbols]

Claims (1)

[Claims] 1. A voltage detection circuit that detects at least one of a forward voltage and a reverse voltage of a thyristor valve, and a voltage application period of the thyristor valve according to the output of this voltage detection circuit is equal to or longer than a predetermined period in one cycle. an AND circuit that outputs a signal when a signal indicating that the thyristor valve is in operation and a signal from the first time detection circuit are both input; A control angle abnormality detection circuit for a thyristor valve, comprising: a second time detection circuit that outputs a voltage abnormality signal when the output of the circuit continues for a predetermined period or more every cycle.