SU1683120A1 - Device for controlling thyristor states - Google Patents

Abstract

The invention relates to electrical engineering and can be used to monitor the state of thyristors in converter protection circuits. The aim of the invention is to enhance the functionality and increase reliability. The goal is achieved by the fact that the device for monitoring the state of the thyristors is equipped with an additional driver 7 time integrals 7, the element OR NOT 5 and the element OR 8, and the sensor 6 of the state of the thyristor is made in the form of a voltage sensor with a falling characteristic that allows you to identify additional emergency modes and simplify the device. 2 Il.

Description

FIG.

The invention relates to electrical engineering and can be used to monitor the state of thyristors in protection circuits of thyristor converters.

The aim of the invention is to enhance the functionality and increase the reliability of the device.

Figure 1 shows the block diagram of the device; 2 is an explanatory timeline.

A device for monitoring the state of thyristors 1, controlled from control system 2, contains a shaper of 3 time intervals, the output of which is connected to the inputs of the element AND 4 and the element OR-NOT 5, the other inputs of which are connected to the output of the thyristor state sensor b, made in the form of a voltage sensor with a falling characteristic, the output of which through an additional driver of 7 time intervals is connected to the third input of the element OR — NOT 5 The outputs of elements 4 and 5 are connected to the inputs of the output element OR 8.

The voltage sensor with a falling characteristic has an inverse dependence of the output signal on the magnitude of the voltage on the thyristor.

The device works as follows.

In normal operation (Fig. 2a), outside the conduction intervals of the monitored thyristor 1, the output of the voltage sensor b, having a falling characteristic, is maintained at the logic zero level, and at the output of the imaging unit 3 - at the level of the logical unit, which provides element 4 and the output of the logical element OR NOT 5 signals at the level of logical zero. Hence, the output of the logic element OR 8 will also be a signal at the level of logical zero, which indicates the normal operation of the converter.

When a control signal arrives from the corresponding channel of the control system to the control electrode of the monitored thyristor 1 and to the input of the imaging unit 3, the thyristor 1 is unlocked, and the output signal of the voltage sensor 6 is set at the level of the logical unit. At the same time, the inverter output 3 sets the signal at the level of logical zero, which provides a zero signal at the output of the element And 4. The shaper 7 is triggered by the signal of a single level at the output of the voltage sensor b time intervals. Single level signals from the output of voltage sensor 6 and

shaper 7 time intervals provide a signal of logical zero at the output of the logical element OR NOT 5 Since the output of the element AND 4 and

7 timeslots will output signals at the logic zero level, then the output of the entire device will also have a signal at the logic zero level, which corresponds to the healthy state

controlled thyristor.

Duration of the output signal is not

the logical zero level of the time element

3 is taken to be equal to the maximum duration of the conduction interval of the monitored thyristor 1 when operating in continuous mode and without overloading.

In this way,

20

72 - + Umaks

where G2 - the duration of the output signal at the level of logical zero element 3 time;

m is the number of pulsations of rectified voltage;

2 / m is the duration of the conduction interval of the controlled thyristor 1 at a switching angle equal to zero;

Umax is the maximum allowable switching angle of controlled thyristor 1 with normal operation of the valve converter and the absence of unacceptable overloads.

The duration of the conduction interval of the controlled thyristor 1, for example, in the rectifier circuit is determined by the dependence:

3-2lgo. „

And-- + y,

where A is the duration of the thyristor 1 conductivity interval,

y is the switching angle depending on the parameters of the converter circuit and the magnitude of the load current.

After locking the controlled thyristor 1, the signal at the output of sensor b is set at a logic zero level.

Thus, the duration of the output signal of the voltage sensor 6 at the level of the logical unit is equal to the duration of the conduction interval of the controlled thyristor 1, i.e.

.

where TI is the signal duration at the level of the logical unit at the input of voltage sensor 6,

During normal operation of the converter and the absence of unacceptable overloads: Y Hmax, and therefore, n years. This ratio between the intervals TI and ta provides a signal at the level of a logical zero at the output of the element 4, which indicates that the thyristor 1 is in good condition.

When emergency mode arises due to malfunction of the controlled thyristor type 1, breakdown in the conductive state or unacceptable converter overloads with an increase in the load current to values exceeding the maximum allowable value of maxmax and tons, therefore, after the time t from the moment of supplying the control pulse the monitored thyristor 1 at the output of the time element 3 sets the signal at the level of the logical unit, and the voltage at the output of the sensor 6 maintains the signal at the level of the logical one This is ensured by the appearance at the output of the AND 4 element and at the output of the logical element OR 8 / Fig. 2.6 / signal at the level of the logical unit, indicating the alarm state of the converter. If the breakdown of the monitored thyristor 1 occurred in the nonconducting state interval, then the output of the voltage sensor 6 sets a signal at the level of the logical unit, which together with the signal at the level of the logical unit at the output of the time element 2 will generate an alarm signal at the output of the And 4 element. Thus, the voltage sensor 6, the time element 3 and the element 4 provide detection of a breakdown type. The operation of the shaper of time intervals 7 and OR-NOT 5 in modes b, c (Fig. 2) is similar to work in mode a (Fig. 2).

If a malfunction of the controlled thyristor 1 occurs - a break in the conducting state or a non-conducting state of the thyristor, then the output of the voltage sensor 6 sets a signal at the level of logic zero, which will be maintained regardless of the arrival of the control pulses, the driver 7 time intervals output will have a steady signal at the level of logical zero. When the first impulse of the control pulse arrives at the output of element 3, the signal is set at the level of logic zero, and at the output of logic

element OR NOT 5 - the signal at the level of the logical unit, indicating the accident / Fig, 2, g /.

The operation of the proposed device in the mode of d intermittent currents (Fig. 2) is ana / iof of operation in normal mode. The duration of the conducting state of the controlled thyristor 1 will be less than m, and, therefore, the duration of the signal of a single

The level at the output of voltage sensor 6 T1 T2, therefore in the mode of intermittent currents at the first and second inputs of the element OR NOT 5 during the time ta -t there will be signals at the level of logical zero.

If only the output signals of the voltage sensor 6 and the time element 3 and, accordingly, the two-way OR-NOT circuit, are used for detecting a fault, then in the discontinuous mode

currents will form a false fault break signal. The use of the 7th time interval shaper and the three-input OR-NOT 5 circuit eliminates the possibility of forming a false alarm, because when the thyristor 1 is unlocked from the output signal of the voltage sensor 6, the shaper 7 time interval is started, and the duration of its output signal of the unit level is triggered.

Thus, by introducing an additional time generator, the functionality of the device is expanded due to the identification of additional emergency modes, and the implementation of a thyristor state sensor as a voltage sensor with a falling characteristic increases its reliability.

Claims (1)

Apparatus of the Invention A device for monitoring the state of thyristors controlled by a control system, comprising a state sensor a thyristor, a time slot shaper, whose input is intended to connect to the output this control theme, and the output to one of the inputs of the AND element, characterized in that extending functionality and increasing reliability, it is equipped with an additional time interval driver, an OR-NOT element and an OR output element, and the thyristor state sensor is made as a voltage sensor with a falling characteristic, the output of which is connected to another input of the AND element and to one and the second inputs of the element OR NOT, one directly and the second through an additional time interval generator, the third input of which is connected to the output of the time interval generator, and the output in with the output of the element AND - to the inputs of the output element OR. Phage. 2