RU2421866C1 - High-voltage thyristor control device - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: high-voltage thyristor control device refers to electric engineering industry, and namely to high-voltage power converters and can be used in devices of smooth start and speed control of high-voltage asynchronous and synchronous electric motors with voltage of 6, 10 and more kilovolt. Due to the fact that the device includes control units as per the number of high-voltage thyristors, and transistor switches, univibrator, optic receiver is introduced to each of them, and isolating transformer is provided with common current winding, pulse-phase control system (PPCS) is provided with optic transmitter, as well as their original connection diagram. ^ EFFECT: design of the device is simplified, its overall dimensions are decreased, capacitor couplings are excluded through high-voltage insulation in shaping circuit of control pulse of thyristor, thus increasing interference immunity of the device. ^ 1 dwg

Description

The invention relates to the field of electrical engineering, namely to power high-voltage converters, and can be used in soft starters and speed control of high-voltage asynchronous and synchronous motors with a voltage of 6.10 kV or more.

To ensure reliable operation of converters with high-voltage thyristors (especially when connected in series), a number of requirements for the magnitude and shape of the control pulses are required. In particular, the voltage amplitude at the beginning of the pulse (forcing) should be at the level of 8-10 V, the front of its rise should not exceed 1 μs, the duration should be at least 15-20 μs (preferably for the entire “burning” time), unlocking constant control current up to 400 mA, current in the boost section up to 600-800 mA. In this case, the isolation of the control circuits from the power must be strengthened and withstand the test voltage for the adopted voltage class.

A device for controlling a thyristor (applicant "MITSUBISHI ELECTRIC CORP", US 3950693, published April 13, 1976) containing a pulse transformer with a primary winding connected by terminals through a key to a high-frequency power voltage source is known. The key control circuit contains a high frequency pulse generator and a semiconductor key control device. When a command to open the thyristor is received, the control pulses from the pulse generator are fed to the key input, which is opened in step with them and through the pulse transformer, the rectifier at the output of the secondary winding of the transformer and the current-limiting resistor opens the thyristor. Thyristor control in this device is carried out by bursts of pulses.

The disadvantages of the analogue include:

- the presence of a pause between pulses to ensure magnetization reversal of pulse transformers;

- insufficient reliability of the device when operating in a high-voltage converter (with a supply voltage of 10 kV or more) due to the presence of capacitive coupling between the primary and secondary windings of pulse transformers, through which an interference signal can pass to the digital control system, which disrupts the operation of the control system;

- lack of forcing (increased signal) of the first pulse.

The closest in technical essence to the claimed invention, taken as a prototype, is a control device for high-voltage thyristors (applicant "ASEA AB" US 4337404, published 06/29/1982), containing a pulse-phase control system, a high-frequency oscillator, isolation transformers with two current primary windings and two secondary windings connected to the inputs of rectifiers, resistors.

High-voltage thyristors are controlled through rectifiers from the secondary windings of isolation transformers. Primary windings of decoupling transformers made in the form of current loops. The conclusions of one primary current winding, designed for boosting pulses, are connected respectively to the thyristor anode and the first capacitor charged through the first resistor from the first voltage source.

The second primary winding, designed to form control pulses with rated parameters, is connected by the first output to the collector of the transistor, and the second through a second resistor to a second voltage source. To recover the energy of the demagnetization of the primary winding when the control pulses are interrupted, a circuit consisting of a second capacitor, a first diode, and a third resistor is used. When the high-voltage thyristor is turned on, the first capacitor is discharged to the first primary winding of the decoupling transformers, forming forced control pulses in the high-voltage thyristors. When the current of the high-voltage thyristor drops to zero, it closes, and a command to turn on the transistor is received from the control circuit.

The transistor is controlled from a high-frequency oscillator and during its open state in the second primary winding of the decoupling transformers, control pulses of a nominal value are formed. During the closed state of the transistor, the demagnetization energy of the cores and the secondary windings of the decoupling transformers is supplied through rectifiers to the control circuits of the thyristors, and the energy of the primary winding is recovered to the second capacitor, from where it is again consumed during the formation of the next control pulse.

The disadvantage of the prototype device is:

- large dimensions of the decoupling transformer by the presence of a second current primary winding and the need for its implementation as well as its other primary winding in the form of a current loop with high voltage insulation;

- the presence of capacitive coupling between the primary and secondary windings of the isolation transformer, through which, upon a sharp change in voltage at the time of opening of the high-voltage thyristors, an impulse current pulse can pass through the circuit: phase, for example A, of the power supply voltage - high-voltage motor winding - capacitance between the winding and the housing motor (“ground”) - digital control system - primary windings of pulse transformers - capacitance between primary and secondary windings of isolation transformers - control thyristor electrodes - RC circuits - phase B (or C). The operation of the pulse-phase control system (SIFU) is disrupted, and a control pulse may appear on the high-voltage thyristor, which must be closed at this time. There is an uncontrolled inrush current in the power circuit, leading to the operation of the overcurrent protection and disconnecting the converter from the network. The most likely occurrence of this phenomenon with a supply voltage of 10 kV and above.

The technical result of the proposed device is to reduce the overall dimensions of the decoupling transformer, as well as to increase the noise immunity of the device and the reliability of the converter.

The specified technical result is achieved by the fact that in the control device for high-voltage thyristors containing a pulse-phase control system, a high-frequency oscillator, control units for the number of high-voltage thyristors, each of which contains rectifiers, an isolation transformer, the secondary windings of which are connected to the inputs of rectifiers, resistors, each control unit has an optical receiver, a single vibrator, transistor switches, the power inputs of which are connected to the outputs of the corresponding rectifier and the control inputs are connected to the output of the optical receiver, moreover, one transistor key is connected to the optical receiver directly or through an input logic element, and the other transistor key is connected to the optical receiver via a single-shot, and the outputs of the transistor keys are connected to the control electrode of the high-voltage thyristor via resistors, while isolation transformer is made with one primary winding connected to the output of the high-frequency oscillator, and the pulse-phase control system contains optical transmitters according to the number of control units.

Due to the fact that the control device for high-voltage thyristors contains a SIFU with optical transmitters, and transistor switches, a single-shot, an optical receiver are introduced into the control units, to perform an isolation transformer with one primary current winding and to place it in the power circuit of the control unit of the high-voltage thyristor (and not in the pulse passage channel thyristor control) the design of the isolation transformer is simplified, its dimensions are reduced, capacitive coupling through high-voltage isolation in pi forming thyristor control pulse, thereby increasing the noise immunity of the device.

The drawing shows a diagram of the inventive control device for high voltage thyristors, where the following notation:

1 - high voltage thyristors;

2 - pulse phase control system;

3 - optical transmitters;

4 - high-frequency oscillator;

5 - isolation transformers;

6, 7 - rectifiers;

8, 9 - transistor switches;

10 - one-shot;

11 - optoelectronic receiver;

12, 15, 16, 17, 18 - logical elements;

13, 14, 19 - resistors;

20 - capacitor;

21 - control units.

The control device for high-voltage thyristors contains a pulse-phase control system 2 (hereinafter, SIFU) with optical transmitters 3, a high-frequency oscillator 4, isolation transformers 5 with a primary current winding connected to the output of the oscillator 4, and two secondary windings connected to the inputs of rectifiers 6, 7 introduced into the communication circuit of the control electrode of the high-voltage thyristors 1 with the control signal sources are two transistor switches 8, 9, a single vibrator 10 and an optical receiver 11, the control circuit of the first trans 9 iterated key associated directly or via a logic element 12 in a yield of 11 optopriemnika; the output of the optical receiver 11 is also connected through a single vibrator 10 to the control circuits of the second transistor switch 8; the input circuits of the transistor switches 8, 9 are connected to the outputs of the rectifiers 6, 7, and the output circuits of the transistor switches are connected through the resistors 13, 14 to the control electrodes of the high-voltage thyristors 1. The one-shot 10 is made on the logic elements 15 18, the resistor 19, the capacitor 20. Elements 5 ... 20 form the control units 21, each of which controls one high voltage thyristor. The number of control units 21 in the device is equal to the number of controlled high-voltage thyristors 1.

The control device for high-voltage thyristors operates as follows:

In the initial state of the circuit, the high-frequency oscillator 4 operates, and current flows through the primary winding of the isolation transformer 5. There is voltage at the output of rectifiers 6, 7, and all circuit elements are powered. At the same time, there is no signal at the output of SIFU 2, at the output of the optical receiver 11 there is a logical unit, and at the inputs of transistor switches 8, 9, logical zeros, transistor switches 8, 9 are closed and there is no signal at the control electrode of thyristor 1. The capacitor 20 of the one-shot 10 is charged, remembering the logical unit at the input of the logical element 16.

When an optical signal appears at the output of the SIFU 2 optical transmitter 3, a logical zero appears at the output of the optical receiver 11, two logical units are at the inputs of the logic element 17, a logical zero is at its output, and logical units are at the outputs of the logic elements 12, 18 and the inputs of transistor switches 8, 9 . In this case, the transistor switches 8, 9 open, supplying a boost current through resistors 13, 14 to the control electrode of the high-voltage thyristor 1, causing it to quickly open. The duration of the boost current is determined by the discharge time of the capacitor 20 through the resistor 19, after which a logic zero appears at the input of the logic element 17, a logic one at its output, and a logic zero at the output of the logic element 18 and the input of the transistor switch 8. The transistor switch 8 is closed, the current through the resistor is stopped, the boost is removed, and then the control current flows through the thyristor control electrode through the transistor switch 9, the duration of which is equal to the signal duration at the SIFU output.

Thus, at the output of the high-voltage thyristor control device, a signal of the required shape and duration is generated without using an isolation transformer in the passage of the thyristor control pulse from the digital control system. The use of fiber optic isolation in the passage of the control signal of the high-voltage thyristor eliminates the appearance of interference to this high-voltage thyristor from the operation of other phases of the converter through capacitive isolation connections, increasing its reliability.

The execution of the decoupling transformer in the power circuit of the device, usually located directly at the thyristor in its high-voltage part, with one current winding reduces the overall dimensions of the decoupling transformer and allows to increase the air gaps between the elements, also increasing the reliability of the converter.

The inventive control device for high-voltage thyristors has been tested as part of the device UBPVD-S soft start high-voltage electric motors, the results of which decided to introduce it into production.

Claims (1)

A control device for high-voltage thyristors, containing a pulse-phase control system, a high-frequency oscillator, control units for the number of high-voltage thyristors, each of which contains rectifiers, an isolation transformer, the secondary windings of which are connected to the inputs of rectifiers, resistors, characterized in that each control unit contains optical receiver, one-shot, transistor switches, the power inputs of which are connected to the outputs of the respective rectifiers, and the control inputs are connected to the output of the optical receiver, moreover, one transistor switch is connected by an input to the optical receiver directly or through an input logic element, and the other transistor switch is connected by an input to the optical receiver through a single-shot, the outputs of the transistor switches are connected to the control electrode of the high-voltage thyristor through resistors, while the decoupling transformer is made with one primary winding connected to the output of the high-frequency oscillator, and the pulse-phase control system contains optical transmitters in number b locks of management.