SU1387150A1 - Method of controlling thyristor inverter - Google Patents

Abstract

This invention relates to electrical engineering and can be used in static converters. The purpose of the invention is to increase the power factor. This device provides for the correction of the inverter's stock angle setpoint depending on the transformer control zone, which eliminates the overshoot of the stock angle setpoint in the low zones and increases stability at the higher control zones. 4 il.

Description

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The invention relates to electrical engineering, in particular, to converter equipment, and can be used to regulate the inverter at the constancy of the stock angle, mainly on the electromotive composition of a single-phase-direct current in regenerative braking mode.

The aim of the invention is to increase the power factor of the inverter.

FIG. 1 shows the block diagram of the proposed device connected to the inverter - transformer; in fig. 2 and 3 are diagrams of output voltages of device blocks; in fig. 4 is an example of a specific implementation of a reference element, switchgear, and leveling device.

The device comprises serially connected mixing voltage setting device 1, comparison element 2, first integrated element 3, first phase control unit 4, coincidence element 5, second integrating element 6, second phase control unit 7, switchgear 8, block 9 output amplifiers. The device also has a cell, luch 10, the input of which through the rectifying bridge 11 is connected to the measuring transformer 12, and the output to the second element 1 of the comparison. In this case, the control input of the key 10 is connected to the output of the first unit 4 of the phase control of the device. A switching angle sensor 13 is connected to the second coincidence element 5. In addition, the device is equipped with a control voltage adjuster 14, the output of which is connected to the input of the quantizer 15 level and via the third phase control unit 16 to the second input of the switchgear 8, and the output of the quantizer 15 is connected to the third input of the comparison element 2 the control input of the switchgear 8. The device is connected to the inverter 17 and the sectioned transformer 18.

FIG. Figures 2 and 3 depict voltage diagrams at the input (О ,,,) and output of block 15 (Uni, Una, Uns) and voltage diagrams at the outputs of blocks 12, 10, 2, 4, 13, 5, 17.

The device works as follows.

In each half period, two pulses are produced with angles n and a (Fig. 3). The first pulse ar is generated automatically by the stock angle controller of the inverter unit 1-7, 10-13, the phase of the second SSR is adjusted by the driver (with manual control) using the control voltage setpoint 14.

To form the pulses, the valves of the inverter 17 are unlocked with the phase ap ar - Uis angle signals (Fig. 3), proportional in duration to the switching process, from the switching sensor 13, implement

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on the basis of the current transformer, are fed to the first input of the coincidence element 5. Its second input is supplied by rectangular signals U4 from the output of the first phase control unit 4, proportional in duration to a predetermined value of the stock angle of the inverter. When the voltages U4 and Uis coincide, the output of the coincidence element 5 generates a signal Us, proportional to the mismatch A between the given and actual stock angles A bs-bf. This signal corrects the output voltage level of the second integrating element and accordingly changes the phase ar of the trigger pulses at the output of the second phase control unit 7, which implements a pulse shaping method with a sweep conversion. As a result, the inverter is controlled by the constancy of the stock angle b const.

To form the stock angle setting bz, taking into account the magnitude and shape of the voltage of the power transformer, a signal Ui2 proportional to the supply voltage from the output of the measuring transformer 12 through a rectifying bridge I is applied to the key 10. Simultaneously, in the first unit 4 of the phase control, a sawtooth sweep voltage is formed Fig. 1 synchronized with the network, which is compared with the voltage Us at the output of the first integrating element 3. If, then the signal U4 is generated at the output of the first phase control unit 4. This signal locks the switch 10, at the output of which a voltage Uio equal to Ui2 appears.

In the comparison element 1, Uio is matched and the bias voltage Ui, which is chosen so that in the steady state the areas Si and 82 are equal.

If the distortion leads to a decrease in the supply voltage of the power transformer in the range from ar to l, the signal Uio changes in the same way and the area equality is violated by Si 82. This leads to a change in voltage at the output of the first integrating element 3 and a corresponding change in the duration of the signals of the first block 4 phase controls. The latter causes a decrease in the duration of the signals Uio at the output of the switch 10. This transient process stops at the moment when the volt-second area 82 of the voltage Uio becomes again equal to the volt-second area Si of the voltage Ui. Thus, the value of the stock angle setting b is automatically adjusted by maintaining equality over a half-period of volt-second areas of voltage Uio at the output of the switch 10 and voltage Ui at the output of the setting device 1 of the bias voltage.

Infinitely variable voltage Ui of inverter 17 is performed by turning the controller knob by the driver by an angle f, which leads to corresponding changes in the signal Uu at the output of the control voltage setting device 14 and the phase of adjustable pulses to the output of the third phase control unit 16 with a sweep transformation ("vertical method).

The quantizer 15 in terms of level, depending on the magnitude of the control voltage UM, generates signals corresponding to the zone number. This will lead to a change in the voltage U, at the output of the reference element 2 and the signal Us at the output of the first integrating element 3 and a corresponding change in the duration of the signals of the first phase control unit 4. The latter causes a decrease in the duration of the signals Uio at the output of the switch 10. This transient process stops at the moment when the volt-second area 82 of the voltage Uio becomes again equal to the volt-second area Si of the voltage U |. Thus, taking into account the control zone, the value of the stock angle setpoint is automatically adjusted by maintaining equality over a half-period of volt-second voltages Uio at the output of the key 10 and voltage Ui at the output of the bias voltage setting device 1.

The quantizer 15 is three threshold elements connected in parallel by level. Their thresholds are set to different levels - U,, Uni, and „5 (Fig. 2). The output signals of the threshold elements are equal to "O when Un and" I when Uy Un serve as logical signals of the control zone number. The presence at the outputs of all three threshold elements of the signals “O, i.e. with Uy-Un, it is perceived as a signal of the first control zone. After the threshold element 19 is triggered, the signal "1" appears at its output, which serves as a signal of the second control zone in the presence of signals "O at the outputs of the threshold elements 19 and 20. After the threshold element 21 triggers, the output signals of all the threshold elements (" "1, “O) corresponds to the third zone. After the threshold element 20 is triggered, the output signal combination "1," 1, "1 corresponds to the fourth control zone.

The logic signals from the outputs of the threshold elements of the quantizer 15 are fed to the summing input of the comparison element 2, made on the basis of the operational summator, by the level. As a result, with the transition to higher adjustment zones of the inverter, the stock angle settings increase.

The distribution of pulses with phases ar and ar on the respective shoulders of the inverter

17, depending on the control zone, is produced by the switchgear 8. This device is a unit of diode switches, the nodes of which realize

logical functions "I. It can also be performed on the basis of the K155 KP1 series selector-multiplexer.

The first and second inputs of the switchgear 8 are supplied with signals from

Q phase ar from the third phase control unit 16 and phase ap from the second phase control unit 7. The signals from the threshold elements 19-21 of the quantizer 15 are supplied to the control input of the switchgear 8 by a level. A certain combination of these signals ensures the implementation of a predetermined control algorithm.

The level quantizer 5 (FIG. 4) is three threshold elements connected in parallel. The output of the quantum body 15 is connected to a separate input of the comparison element 2, made on the basis of a multi-input operational adder.

Switchgear 8 is implemented based on integral multiplexer selectors. It distributes pulses along the converter's shoulders in accordance with the algorithm of its operation. The arms of the Uap control from the second phase control unit 7 or from the third phase control unit 16 in accordance with the control zone, which is determined by the control signals from the quantizer 15, are allowed or prohibited on each arm. The output of the selector-multiplexer permits the passage of the signal from one of the inputs, X16-X23, depending on the combination of signals at the control inputs XII, X13-X15.

The device allows to increase the power factor of the inverter due to the correction of the specified stock angle when working on various control zones. In particular, with a decrease in the control zone and a corresponding decrease in the inductance of the transformer, a decrease in the value of bz will increase the return of energy to the network and reduce the consumption of reactive current from the supply system.

In addition, the inverter’s stability in transient conditions is improved as a result of taking into account changes in the reactance of the power

0 transformer.

Claims (1)

Invention Formula A device for controlling a thyristor inverter, comprising a switching angle sensor, the input of which is intended to be connected to the winding of a power transformer, a rectifying bridge, a key, a measuring transformer and serially connected bias voltage adjuster, a reference element, the first integrating element, the first phase control unit , a coincidence element, a second integrating element, a second phase control unit, as well as an output amplifier unit, the output of which is intended to be connected to the valves In this case, the second input of the coincidence element is connected to the output of the switching angle sensor, and the output of the first phase control unit is connected via a switch to the second input of the comparison element, the control input of the switch is connected via a rectifying bridge to the output of the measuring transformer, the input of which is intended to be connected to winding power transformer. characterized in that, in order to increase the power factor, it is equipped with a control voltage sensor, a level quantizer, a third phase control unit, a switchgear, and the reference element is provided with a third input, and the control voltage output device is connected to the quantizer input the level and through the third phase control unit to the first input of the switchgear, the second input of which is connected to the output of the second phase control unit, and the output to the input of the output force unit the oil level of the quantizer output connected to a third input of the comparison element and the control input of the switchgear. W v2: L and, Have I I i Th ЗН h 2 / (jjt Have one/ ut I I t rL . (t Ljt h (jJt Fig.Z orn1 0omi To channel 2-n Fig.L