SU1411897A2 - Single-channel device for controlling rectifier converter - Google Patents

Abstract

This invention relates to electrical engineering and can be used in thyristor converters. The purpose of the invention is to increase the speed and reduce the pulsations of the rectified toKa. The introduction of a forced switching circuit, which allows the converter to operate with a switching frequency of a higher mains frequency,. increases the speed due to the transition to the inverter mode along the discharge curve of the capacitor of the forced switching circuit. 2 Il.

Description

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The invention relates to electrical engineering and can be used with thyristor converters of alternating voltage to constant, in which the thyristor cathodes have a common point (for example, zero semi-equals {1 and other auxiliary converter circuits), and is an improvement of the device according to ed. Ev, No. 1001428.

The purpose of the invention is to increase the speed of the device and reduce the amplitude of pulsations of the rectified current.

FIG. 1 shows the principle of a single-channel control device for a valve converter with a cathodic thyristor group; in fig. 2 shows an example of a relay element. .

A single-channel device for controlling a valve converter with a cathodic group of thyristors contains a current sensor 1, for which a measuring shunt connected in series with the load 2 of a valve converter is used. The output of current sensor 1 is connected to the input of relay element 3 in series with source 4 of control voltage. The relay element 3 can be a series-connected direct current amplifier 5, Schmidt trigger 6, amplifier 7 and switch 8. Switch 8 is inserted into the neutral wire of the diode distributor 9 pulses. The diode distributor 9 pulses contains a three-phase transformer 10 and diodes 11-13. The windings of the transformer 10 are included in the star with a neutral wire, the primary windings are connected to the network, and the secondary ones are connected through diodes 11-13 to the control electrodes of the corresponding thyristors 14-16. The zero point of the secondary windings through the limiting resistor 17 and the key 8 are connected to the cathodes of thyristors 14-16 of the valve converter.

The inverter diode distributor 18 pulses consists of diodes 19-21 and a transformer 10, the secondary windings of which are connected as follows: the end of the winding of phase C - to the beginning of the “winding phase of the hung terminal of the winding of phase B through diode 19 to the control electrode of the thyristor 14; ana - the windings of phases B and A are connected via diode 20

to thyristor 15; similarly, the windings of phases A and C are via diode 2 to thyristor 16. The zero point of secondary windings through limiting resistances 22 and switch 23 is connected to the cathode of thyristors 14-16 of the gate converter. United to the common point of the cathodes of thyristors 14-16 through the diode

Q 24, throttle 25, and capacitor 26 are connected to network zero. In parallel with the diode 24 and the choke 25, a thyristor 27 is connected, the cathode of which is connected to the cathodes of thyristors 14-16, the anode —c

5 by a capacitor 26, and the control electrode through the limiting resistor 28 to the cathode of the diode 24.

The device works as follows.

0 The control voltage II is applied to the input of the relay element 3 from the source 4 of the control voltage. The key 8 of the relay element 3 is closed, so | How conditions are fulfilled:

5U-KI 4,

where is the output voltage of the sensor 1 of the load current 2; The hinge width of the 2 L hysteresis of the rail element 3 is chosen to be less than the amplitude of the pulsations for example. No load current sensor 1 2.

The value is equal to zero at the initial moment of time and the distributor 9 pulses collected on the transformer 10 supply the unlocking signal to that of thyristors 14-16, on the anode of which the highest potential. If the highest potential at the anode of the thyristor 14, then the unlocking signal passes through the circuit: the end of the winding phase A of the distributor 9 pulses - dip

13- thyristor control electrode

14 - thyristor cathode 14 - closed switch B - limiting resistor 17 - common point of the diode distributor 9.

The thyristor 14 is opened up and the voltage of phase A is applied to the load 2. The current I of the load 2 under the action of the voltage of phase A increases. The voltage from current sensor 1 increases and, with U-KI, D unplugs relay element 3 and opens its key 8, removes unlocking voltage from thyristor 14. At the same time, key 23 of relay element 3 closes and invariant distributor 18 pulses supply unlocking signal on one of

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thyristors 14-16, on the anode of which there is the most negative potential. This thyristor cannot be ignited at this time, so the thyristor continues to conduct current 14.

Simultaneously, the diode 24 is in the chain - the choke 25 is flowing the charging current of the capacitor 26. The capacitor 26 is charged along a curve corresponding to the charge of the capacitor connected in series with the inductor until the voltage of the full charge is close to twice the voltage of phase A After the charge of the capacitor 26 is finished, the current through the diode 24 drops to O. The recharge of the capacitor 26 through the choke 25 cannot occur due to the one-way conduction of the diode 24 and the voltage of the capacitor 26 is applied to the cathode of the diode 24 Phase A which is applied to the anode of the diode 24. The diode 24 is also locked to the control electrode of the thyristor 27 through a limiting resistor 28 a positive voltage U is applied to its cathode, equal to the voltage of the charged capacitor 26.

The thyristor 27 is open, and the capacitor 26 is connected to the load 2 and to the cathodes of the thyristors 14-16. The voltage of capacitor 26 is blocking for open thyristor 14. The discharge current of the capacitor, which is negative for conductive thyristor 14, forcibly reduces the direct current of thyristor 14 to O. The parameters of the forced switching circuit are chosen so that the residence time of the conductive thyristor 14 is 14 under the blocking voltage of the capacitor 26 since connecting the capacitor 26 to the thyristor 14 was enough to disconnect the thyristor 14. The thyristor 14 is turned off and the capacitor 26 continues the process, then com ki 2.

The voltage U of the capacitor 26 decreases and reaches a value equal to the most negative voltage at the anode of one of the thyristor group of the converter.

Under the influence of the decreasing voltage and the capacitor 26, the current through the load 2 decreases and, accordingly, the voltage of the current sensor begins to decrease. By doing

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Conditions U-K17; 3 triggers the relay element 3, closes the key 8 and opens the key 23. The diode distributor 9 of pulses delivers a trigger signal to the thyristors 14-16.

With an appropriate choice of inductance of drossel 25 and capacitor 26 capacitance, the charge time is condensate. 26 and the time of its discharge is much less than the period Tj, of the network. In this case, when the discharge duration of the capacitor 26 is short and the anode of the thyristor 14 is operated before the relay element 3, the previously conducted current continues to be at its highest potential, the thyristor 14 opens again, unlocking impulse passes through the circuit described above.

The process of charging the capacitor 26 again begins to a value greater than the voltage of phase A. The device establishes a self-oscillation with a frequency depending on the parameters of throttles 25 and capacitor 26. When the voltage of phase A decreases, starting from the moment of natural switching, the voltage of phase B the phase voltage A becomes higher. When the trigger pulses are received from the diode distributor 9, the thyristor 15 is turned off. The trigger signal passes through the circuit: the end of the phase B winding of the distributor 9 - diode 12 - thyristor control electrode 15 - cat thyristor 15 - closed key 8 - limiting resistor 17 - common point of the diode distributor 9. Next, the voltage of phase C becomes higher than the voltage of phase B. The thyristor 16 operates. The starting pulse passes through the circuit: the end of the winding of phase C of the distributor 9 - diode 11 - thyristor control electrode 16 - thyristor cathode 16 - closed switch 8 - limiting resistor 17 - common point of the diode, distributor 9.

Thus, the circuit operates in a self-oscillating mode with a switching frequency depending on the parameters of the throttles 25 and the capacitor 26. The residence time of the converter in the inverter mode is determined by the level of the set current of the control voltage source. The relay element 3 controls the position of the key 8, depending on the above ratios (U-KI) and + L.

With a large input control voltage U, the voltage U., K1 to the transducer to operate with a switching frequency much higher than the supply mains frequency, which ensures: a significant increase in the converter performance due to switching to the inverter mode by the discharge curve of the capacitor of the forced switching circuit and reducing the amplitude of the pulsation of the voltage meleny current.

The current 1 does not have time to reach U + d during the charging time of the capacitor 26. The key 8 remains closed. Unlocking voltage is present at the control electrodes of the thyristors 4-16. The thyristor continues to burn, letting current through before a control voltage jump. The current may not reach the upper threshold value of the relay element 3, i.e. The condition is also fulfilled during the burning time of one thyristor. In this case, natural switching occurs, and the next switching order thyristor is ignited, which ensures the maximum voltage on load 2 until the voltage K1 reaches U + 4. After this, the considered above self-oscillatory regime is considered.

With an abrupt decrease in the control voltage U, the voltage

; The UQC of current sensor 1 becomes greater and + L. Key 23 closes and key 8 opens. A trigger pulse from a diode distributor 9 pulses

I to the thyristor, which passed the current at the moment, does not flow. Valve

 the converter goes to the inverter; mode on the discharge curve of the capacitor 26. Next, the inverter distributor 18 pulses due to the fact

j that key 23 continues to be in

I closed position, provides unlocking signals to each of the thyristors 14-16 at a control angle of / 180 -d- -V, where o and V are the switching angles and kom- 40 One-channel device for controlling the valve converter

Valve converter work-on auth. St. No. 10014285 is different

ten

The latency angle, when the signal is processed for a drop in the load current in a known device for inputting the signal for switching the circuit to the inverter mode, at the control angle / close to zero, reaches 1G. Such a delay prevents the use of known devices in 20 systems requiring high speed, for example, as an element of automation systems, etc.

When used in valve converters, thyristors with small

25

recovery time t „,,,,, О μs

the switching frequency f of the single-channel device can be increased to (3–5) kHz, respectively, by selecting the parameters of the throttle and the capacitor. By

30 compared with the known device, the speed of the proposed device increases by 20-50 times.

The amplitude of the pulsations of the rectified current decreases in proportion to the increase in the switching frequency of the device. . properties.

Claims (1)

Invention Formula in inverter mode with the maximum negative rectified voltage on the load until the current I of the load 2 drops to the specified one. The use of the proposed single-channel device for controlling a valve converter ensures that, in order to increase the speed of the device and reduce the amplitude of the pulsations of the rectified current, it is equipped with a forced switching circuit implemented in the form of a series-connected diode, throttle and capacitor , in comparison with the known devices parallel to the load, and the tirissacii, the expansion of functional areas, the cathode of which is connected to the capabilities of the valve photoelectret fire rate, an anode for a capacitor, and controlled by introducing in it a forced L chain gate electrode through a resistor switching sub-tion, allows the key to guide pre choke. 14118976 The generator should work with a switching frequency much higher than the power supply frequency, which provides: significant faster converter speeds due to switching to the inverter mode along the discharge curve of the forced switching circuit capacitor and reducing the amplitude of the ripple of the rectified current. - ten Single-channel device for controlling the valve converter The latency angle when the signal is processed for a drop in the load current in the known device of the arrival of the signal for switching the circuit to the inverter mode at the control angle / close to zero reaches 1G. Such a delay prevents the use of known devices in systems requiring high speed, for example, as an element of automation systems, etc. When used in valve converters, thyristors with small recovery time t „,,,,, О μs the switching frequency f of the single-channel device can be increased to (3–5) kHz, respectively, by selecting the parameters of the throttle and the capacitor. By Compared with the known device, the speed of the device is increased by 20-50 times. The amplitude of the pulsations of the rectified current decreases in proportion to the increase in the switching frequency of the device. . properties. Invention Formula U This is due to the fact that, in order to increase the speed of the device and reduce the amplitude of the pulsations of the rectified current, it is equipped with a forced switching circuit, implemented in the form of serially connected diodes. L B C P FIG. 7