SU1654946A1 - Device for controlling three-phase converter - Google Patents

Abstract

This invention relates to a converter technique and can be used in direct current to ac converters. The purpose of the invention is to improve the noise immunity. The goal is achieved by connecting the inputs of the comparators 7-9 to the corresponding outputs of the clock transformer 1s and the outputs of the comparators 7 to 9 with the control inputs of the respective selection blocks 4-6. As a result, the ignition angle of each thyristor of the converter 11 is determined taking into account the voltage condition of the previous phase. This eliminates the tilting of the converter 11 and, therefore, increases the noise immunity in the conditions of low-frequency interference and subsidence in the supply voltage, 6 sludge.

Description

The invention relates to a converter technique and can be used in direct-to-ac converters, for example, in regenerative braking control circuits for electric motors,

The aim of the invention is to improve noise immunity. I

FIG. 1 shows the functional diagram of the device} in FIG. 2 — An example of the implementation of the thyristor control pulse shapers of the converter; FIG. 3 shows an example of implementation of the selection block; FIG. 4 and 5 — An example of the implementation of the first and second three-phase rectifiers, respectively, in FIG. 6, the voltage plots, of a device for controlling a three-phase converter.

A device for controlling a three-phase converter contains a synchronizing transformer 1, first 2 and second 3 three-phase rectifiers with zero output, connected by their inputs to the outputs of synchronizing transformer 1, three selector units 4-6, each of which is connected to the output of the first three-phase rectifier 2, the second input - to the output of the second three-phase rectifier 3, three Comparators 7-9, each connected with its first input to the output of the corresponding block 4-6, the second input - to the corresponding Output dy synchronizing transformer 1 and the output control through pulse shaper 10 - to the control inputs of the thyristors thyristor one transducer 11 and to the third input of the corresponding unit 4 - 6 choice.

The first three-phase rectifier 2 can be made similarly to that shown in Fig. 4, the second three-phase rectifier 3 is similarly cast, My to FIG. 3, and the selection blocks 4-6, similarly to the one shown in Fig. 3.

The control pulse shaper 10 can be made as shown in the diagram (Fig. 2), containing a depressor 12 assembled on two inlet coincidence elements, pulse shaping units 13-18, and elements 19-24 of the galvanic isolation.

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1654946d

A device for controlling a three-phase converter operates as follows.

The phase voltages of the three-phase network, through the synchronization transformer 1, are each fed to the first input of one of the comparators 7-9. At the output of the comparators 7-9, an alternating signal is formed, a duty cycle 2, the phase position of which relative to the input sinusoidal signal is determined by the voltage at the second input of the comparator 7-9. In this case, the voltage to the second input of the comparator 7-9 comes from the output of the corresponding block 4-6 the choice and its sign is determined by the level of the output voltage of the comparator 7 - 9. So, for example, with a positive level of the output voltage of the comparator 7 - 9, the second input of the comparator 7-9 receives the output voltage of the selector 4-6, but equal to the output voltage of the first three-phase rectifier 2, being different from it by the amount of voltage drop across the diode selecting unit 4-6. The other diode of the selection block 4-6 is under reverse voltage, and the output voltage of the second three-phase rectifier 3, which is fed to the input of the selection block 4-6, does not affect its operation. Alternating signals of a duty cycle of 2 5s shifted relative to each other by 120 e. hail., from the outputs of the comparators 7-9 are fed to the inputs of the formers 10 control pulses. The resistor and the diode at the input of the decoder 12 are designed to match the output voltage of the comparators 7 to 9 with the logic levels of the elements of the decoder 12. The signals (12.1, 12.1, 12.2, 12.2, 12.3,12.3) of 120 el duration are formed at the output of the decoder. degrees with phase ratios in accordance with the voltage plots shown (Fig. 6), the duration of these signals is equal to the time of current flow through each thyristor of the thyristor converter 11 during energy recovery from the DC link to the network. On the negative fronts of these signals, using blocks 13-18, pulses of the required length are formed, which through elements 19 - 25 of galvanic isolation transfer 30

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on the control electrodes of the thyristors of the thyristor converter 11. The reaction of the control device is a three-phase converter for a terminal, for example, the voltage of phase A is shown in Fig. 6 by a dotted line. From the voltage plots, it follows that a voltage drop in phase A leads to an advance in the formation of the thyristor control signal of the phase B, which ensures the interception of current in the conditions of a drawdown in the network voltage.

Compared with the known, the proposed device for controlling a three-phase converter has a better performance under low-frequency noise and subsidence conditions in a three-phase network, which is achieved by connecting the second inputs of the comparators 7 to 9 with the corresponding outputs of the synchronizing transformer 1, and the outputs of the comparators 7 to 9 - sec the third inputs of the respective blocks 4-6 of choice. As a result, the ignition angle of each thyristor of the thyristor converter 11 is determined taking into account the state of the voltages phase phase, which eliminates the overturning of the thyristor converter 11 and, therefore, increases the

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performance under conditions of low-frequency noise and subsidence in the voltage of a three-phase network.

Claims (1)

Invention Formula A device for controlling a three-phase converter containing a clock transformer, the outputs of which are connected to the inputs of the first and second three-phase rectifiers with zero output, three selectors, the first inputs of which are connected to the output of the first three-phase rectifier with zero output, the second with the output of the second three-phase rectifiers zero output mitele, the outputs of the first, second and third selection blocks are connected to the first inputs of the respective comparators, the outputs of which through the formers of pulses are and means for connecting the control electrodes of the thyristor converter, characterized in that, in order to improve the noise immunity, the second input of each of comparators connected to a corresponding output of the synchronization transformer, and the control input of each selection block is connected to the output of the respective comparator. IK output komparsg / gg0 / ea Fig.Z DC Uc " Output Rig. four Output FIG. five three phase gemu g & (Pi / iS