SU966824A1 - Device for synchronization of converter control system with three-phase ac network - Google Patents

Description

(5A) DEVICE FOR SYNCHRONIZATION SYSTEM

THREE-PHASE TRANSMITTER CONTROL The invention relates to converter technology and can be used in control systems for valve converters and electric drives. Devices are known for synchronizing the converter control system with a three-phase AC network, containing three circuits, each of which includes a diode and a zener diode connected to the mains phases and loaded to a damping resistor, the outputs of which are connected to the inputs of the corresponding differentiating elements Cl through the optocouplers. The disadvantages of lime devices are low synchronization due to the variation in the parameters of the elements and significant power losses in the damping resistor. The closest technical solution to the invention in terms of means and results achieved is a device for synchronizing the AC converter with a three-phase AC network, which contains three limiting amplifiers, the inputs of which are connected to the terminals for connecting the AC network, and three formers synchronization pulses 2. The disadvantage of the device is low reliability and noise immunity. The purpose of the invention is to increase reliability and noise immunity. The goal is achieved by the fact that the device is equipped with three three-input NAND logic elements, the first inputs of which are connected to the outputs of the respective limiting amplifiers, while the output of the first element AND-NES is connected to the input of the first driver and the second inputs of the second and third elements AND- NOT, the output of the second element AND-NOT is connected to the input of the second shaper and to the second input of the first and third inputs of the third element is AND-NOT connected to the input of the third pulse shaper and to the third inputs of the first and second th AND-IE.

FIG. 1 shows an electrical diagram of a synchronization device of a converter control system with a three-phase, AC network; in fig. 2 - time diagrams that show his work.

The device (Fig. 1) contains three limiting amplifiers 1–3 made, for example, on the basis of operational amplifiers operating in the regime of bargains, three-input logic elements AND-Ht 4–6 and synchronization pulse shapers whose outputs are 10–12, respectively, are outputs devices. Formers 7-9 can be implemented as differentiating JC-chains. The outputs of the limiting amplifiers 1-3, are qualitatively connected to the first inputs of the N-6 logical elements. The output of the M-tJE logic element is connected to the input of the imaging unit 7 and the second inputs of the logic elements 5 and 6. The output of the logic element 5 is connected to the input of the imaging unit 8, the second input of the element and the third input of the element 6. The output of the logic element 6 is connected to the input of the imaging unit and also the third inputs of elements i and 5.

The device works as follows.

j§ The phase voltages of the L, B, and C networks of FIG. 2s | . Amplifier limits 1-3 form rectangular pulses whose duration coincides with negative half-periods of phase voltages (Fig. 26 6 and g.

In the positive half-periods of the phase voltages, the limiting amplifiers are in the locked state and there are no pulses at their outputs. The signals from the outputs of blocks 1-3 are fed to the first inputs of logical elements AND-NOT (-6.

Claims (2)

The operation of logic circuits 4-6 is illustrated by their state table. temporary plots indicated in the diagram (Fig. 2 "); At the outputs of logical elements AND-NOT-6 rectangular and pulses are formed, the leading fronts of which are synchronized with the moments of the transition of the corresponding phase voltage of the network through zero from minus to plus (.fig. 2 d, e, V of D-element k - phase A, for element 5 - phase B and for element 6 - phase C. Formers produce the formation of narrow sync pulses synchronized with the leading edges of square pulses from the outputs of elements A-6. Thus, at the outputs 10-12, devices are formed clock pulse hard locked As it follows from FIG. 2 and the state table, rectangular pulses are formed at the outputs of logic circuits tS only at the instants of the appearance of a new combination of two zeros on the buses Ax | A, B-, C. Therefore upon the appearance of a positive polarity pulse at the output of one of the limiting amplifiers 1, 2 or 3 (for example, due to the failure of the voltage of phase A in sections 3 and 10 or phase C in section 6, fig. 2 a) The state of the logical elements k-6 remains the same. Consequently, the immunity of the device is improved. On the other hand, the state of the k-6 elements changes only when the first phase of the supply voltage goes from minus to plus, i.e. when zeros appear on the first inputs of these circuits. With repeated zero crossings of the voltage of this phase, the states of the elements do not change (Fig. 2, E, e, G, portions j and 9). Thereby increases the reliability of the device. Another advantage of the proposed device is the termination of its operation when the voltage of one of the phases of the supply network is lost. This situation is illustrated by the operation diagram (Fig. 2, sections 12-18) and the state table. When the voltage of one of the phases disappears, for example, phase 9 + 6 V, the logic elements k-6 transition to the state when their outputs have a constant potential (in Fig.2 e, g, 3, it is a unit, zero and the unit respectively for the circuits - (), Therefore, there are no clock pulses at the output of the formers. Thus, using the invention improves the reliability and noise immunity of the device. Formula of the Invention A device for synchronizing a converter control system with a three-Lase AC network containing There are three limiting amplifiers, the inputs of which are connected to the terminals for connecting the phases of the AC network, and three synchronization pulse makers, characterized in that, in order to increase reliability and noise immunity, it is equipped with three three-input and -NE elements, the first inputs which are connected to the outputs of the respective limiting amplifiers, while the output of the first element AND-NOT is connected to the input of the first driver and the second inputs of the second and third elements AND-NOT, the output of the second element AND NOT under for prison to and to the input of the second shaper; The second input of the first and third inputs of the third NAND, and the output of the third element N-NOT connected to the input of the third driver, pulses and to the third inputs of the first and second elements AND-NOT. Sources of izhormatsii, rintye into account with the expert: ize 1.Demidov S.V., Kazansky V.A., ydov.V.A. Experience in building digital control systems for tank electric drives. L., LDTP, 1979, p. 17 2. Girenko V.L. et al. Experience in the application of integrated circuits in thyristor electric drives. L., LDNTP,. 976, p. 29.