SU1511738A1 - A.c. voltage regulator - Google Patents

Abstract

The invention relates to electrical engineering and can be used to control the voltage of high-power consumers. The purpose of the invention is to increase reliability, improve the shape of the curve and the harmonic composition, as well as increase the stability of the output voltage. The output voltage is equal to the sum of the network voltage and the main winding 4 of the transformer 1. The goal is achieved due to the freedom to choose the control angles of the thyristors 7 ... 14 of single-phase bridge converters 5 and 6, regardless of phase differences and voltage and current signs. The control pulses to thyristors 7 ... 14 are applied to favorable times from the point of view of switching, which leads to an increase in reliability. Transducers 5 and 6 are used as switches for switching the polarity of the voltages applied to the right and left parts of the circuit, formed by windings 17, 3 and windings 16, 2 of drossel 15 and transformer 1, respectively. DC current generated in converters 5 and 6, it folds up with an alternating load current and prevents the current in thyristors 7 ... 14 from falling to zero in the working time interval. Ensuring the symmetry of the voltage of the winding 4 relative to the voltage of the network leads to an improvement in the shape and harmonic composition of the output voltage. 2 Il.

Description

The invention relates to electrical engineering and can be used to control the voltage of high-power electrical consumers.

The purpose of the invention is to increase the reliability of work, to improve the shape of the curve and harmonic composition, as well as to increase the stability of the output voltage of the on-load tap-changer.

FIG. 1 shows a schematic diagram of a variable loading regulator (RPN); in fig. 2 - voltage diagrams showing the on-load tap-changer operation.

The variable voltage regulator contains a transformer 1 with two high voltage booster voltages 2 and 3 and one secondary primary 4 windings, two single-phase bridge transformers

The generator 5 and 6, assembled on thyristors 7-10 and 11-14, respectively, and a two-winding choke 13 with windings 16 and 17. The windings 2 and 3 of transformer 1 are connected in series with the windings 16 and 17 of two-winding Drossel 15 and are included in the circuit of the current of single-phase thyristor bridge converters 5 and 6, respectively, with the winding 2 of the transformer 1 being turned on according to the winding 16 throttles 15, and the winding Y being opposite to the winding 17.

The main winding 4 of the transformer 1, in which the additional voltage is created, is connected between the input and output terminals of the on-load tap-changer

FIG. 1 is designated: U., Vix, respectively, of the mains voltage, windings 4 of the transformer 1 and at the output of the on-load tap-changer; in fig. 2 along the axis are shown: 18 — voltage G., 19 and 20 s

tension uj. and G at the outputs of single-phase thyristor bridge converters 5 and 6, respectively, 21 - voltage by a two-winding choke 15, 22 - voltage Ug of a winding 4, 23 - voltage U., on

Oıf

output tap changer.

During the operation of the circuit shown in FIG. 1, in each of the single-phase thyristor bridge converters 5 and 6, the thyristors are turned on and off in pairs by alternately supplying trigger pulses to the pair of thyristors on which the voltage Uj is switched at the time of switching. acts in the forward direction of the thyristors. Moreover, the sum of the control angles

0

five

0

five

0

five

0

five

0 5

the thyristor pairs of each single-phase thyristor bridge converter is (36Q - LoC) eLoGrad, and the sum of the corresponding thyristor pairs of different single-phase thyristor bridge converters is 180 e. The degree of normal circuit operation requires that the constant component of the single-phase output current. thyristor bridge converters 5 and 6 exceeded the te component variable, which is achieved by setting the value of l o /, which is practically within a few e, degrees o. In the diagrams of FIG. considered the ideal case when the resistance of the winding circuit of 2.3 transformer 1 is 0 „

Suppose that at the time point corresponding to the angle (Fig. 2), thyristors 8.9 and 12.13 and voltage 1) and Uj are working at the outputs of single-phase thyristor bridge converters 5 and 6 are opposite to the voltage I. in fig. 2 on axis 19 and 20, respectively. At an angle of 7 to, unlocking pulses are applied to the thyristors 7 and 10 s. Under the action of the voltage U of the network, these thyristors are unlocked, and the thyristors B and 9 are locked, as a result of which the voltage Uj at the single-phase output thyristor bridge converter 5 changes its sign and begins to coincide with voltage 1 of the network. At an angle of 180 - cC-7 (Unlocking pulses are applied to thyristors 11 and 14, as a result of which these thyristors unlock, and thyristors, 13 lock and voltage U at the output of a single-phase thyristor bridge converter 6 also changes its sign and begins to coincide with the voltage of the Up network at an angle of i.t-r 360 J ,,, oT, / j, j-,., - w if,, 4

Pirate pulses are applied to thyristors 12 and 13, which leads to unlocking thyristors 12, 13 and locking thyristors 11, 14o. Starting from the time point corresponding to the angle oi, 3, the voltage U at the output of the single-phase thyristor bridge converter 6 changes its sign again voltage U from the network

Further, by supplying the trigger pulses to the thyristors 8, 9 at an angle of 360 - 0 (7.10, etc., we get-diaof a h

Hfj

grams of stresses u

and g

pred5

put on fig 2 on axis 19 and 20 respectively

Since the windings 16 of the droplets 15 and 2 of transformer I are connected sequentially, and the windings of 17 droplets of 15 and 3 of transformer 1 are counter-sequentially, when the magnetizing forces of the windings of droplets 15 caused by the mains voltage add up, the magnetizing forces of the primary windings of transformer 1 must be subtracted or, conversely, when the indicated magnetizing forces are added in transformer 1, must be subtracted in choke 15. In this connection, each time the voltage applied to the left (in turn on 16 and 2) part of the circuit changes in direction as a result of switching the thyristors of bridge converters 5 and 6, the indicated voltage goes from transformer 1 to choke 15 or back

For example, consider the state of the circuit of FIG. 1, in the time interval corresponding to the section O “1 7, to that indicated in FIG. 2, In this time frame, the beginning of the windings 16 and 17 of the throttles 15 are connected through open thyristors 9 and 13 to the same input terminal. Those. The network voltage is applied to both windings of droplets 15 in the same direction. Therefore, the magnetic fluxes of these windings associated with the mains voltage add up And the beginnings of the windings 2 and 3 of the transformer 1 at a given time interval are connected through the winding of the drossel 15 and the bridge converters 5 and 6 to different input terminals. Therefore, in section O -01-, JO, the voltage on the choke 15 is equal to the mains voltage, and the voltage on the transformer 1 is zero.

It is easy to verify that, starting from the moment of time, corresponding to the angle o / -, jj, when the thyristors of the converter 5 are switched, the conditions for the addition of the corresponding magnetic fluxes of the windings of the throttles 15 and transformer 1 change; the indicated flows in transformer 1 are added, and in choke 15 are therefore subtracted; therefore, in the region o / t, o -

 -11, n

the voltage across choke 15 is zero.

11738

and transformer 1 operates in the same way as a normal transformer, the primary winding of which consists of two parallel branches — windings 2 and 3. Consequently, the EMF (com- puting voltage) of the secondary winding and transformer 1 differs from the primary voltage of the primary winding 0 in the opposite network voltage, by the magnitude of the transformation ratio,

Ieo Ui - yy. Curve voltoto-And to -

The base voltage is constructed according to the following equality:

 and 6- and -I with- Uc li. . 6A 2K 2K K

and has the form shown in FIG. 2

20 axis 22 ,,

Converters 5 and 6 are practically used as conventional switches for switching the polarity of the voltages supplied by the K25 to the right and left parts of the circuit of Fig. 1, but since such switching takes place during each period of the mains voltage, and the thyristors are not in - are fully controllable elements, the operation of these switches is subordinate to certain conditions, so that: so that the output of the switches does not have a large constant, pas component voltage, the sum of the moments of each switch is close to 360 eLagrad, and so that the thyristors do not turn off spontaneously at the moments when the alternating current passes through zero, the switches of the 4Q are selected according to the bridge rectifier circuit, due to the fact that an additional direct current is created in the thyristors of the circuit, which adds to the alternating load current and eliminates

d5 current drop in thyristors to zero on the working interval. Of the four steering angles (/ 7,10, 9, i, and about 2 tons), only one can be chosen arbitrarily from 0-180 °, so

50-how all other angles are determined

thirty

35

from the condition dj

ten

 8.9

 360 —LoC;

o / 11, 14 + 0 {, 2, 3, 360 (;, 10 + I, M

 180.

The angle o (-, fc is adjusted depending on the required voltage at the output of the regulator and each value is 4 o (7, 0 corresponds to a certain output voltage diagram, which is obtained as the sum of the network voltage).

and booster winding and is shown in Fig 2 along the axis 23 „

At an angle, fo 0 (and the values of other control angles determined by the angle i, voltage-I g winding 4 of transformer 1 consists of full half-periods of a sinusoid, i.e., has the shape of a sinusoid, C increases the angle o / jg half-periods Ug. are narrowed and consist of symmetric sections of a sinusoid. At an angle "(t, o 90 e. deg., voltage U d 0, With a further increase in the angle c /, o about half-periods G, it expands again, but with reverse sign, and at 0/7 (About 80 e-grads become full sinusoid.

Accordingly, with a change in the angle cf, 0 from 0 to 180 e град deg, the voltage of the output of the on-load tap-changer will vary within

None and

hell wokc -U 5 (, x

 and 4- and

wdKc

thirty

35

40

de and „„, - the maximum value of 25

of) Mm KS

Ned winding voltage 4 of transformer 1. At a nominal, average and maximum cold voltage, its harmonic coefficient is zero, while in the rototype and analogue schemes of the proposed on-load tap-changer, the harmonic factor of the output voltage is zero at its maximum and minimum the values of A, with the average value of the output voltage, its harmonic coefficient reaches a maximum. Therefore, with the same limits for adjusting the output voltage, the harmonic ratio of the output voltage in the proposed on-load tap-changer is less than that of the known 2 times,

In the real case, when & ei Q due to the inequality of the areas of the positive and negative portions of the diagrams shown in Fig. 2 on axes 19 and 20, at the outputs of the single-phase terminals of the bridge bridge transducers 5 and 6 there appear constant components of the voltages the action of which maintains the necessary constant components of the currents in their output circuits.

The mode in which the control angles of the transducers 5 and 6 are interconnected by the condition is 180 elSrad. is one of the possible modes of operation of the controller. Od45

50

55

0

five

0

five

five

0

five

However, in general, the observance of this condition is not necessary. The operation of the device is not impaired even when the converters 5 and 8 are controlled independently of each other. They can even be connected to completely different power sources with different voltages and frequencies. In particular, one of the indicated converters can be shorted. In all these cases, the voltage of the secondary winding 4 of transformer 1 will be determined by the indicated equality. For example, if converter 6 is shorted, Toe. Uj Oh, then according to the indicated equality we will have

and 5 ie voltage curve Ug

on a different scale will repeat the voltage curve U.

The technical and economic efficiency of the on-load tap-changer as compared to the prototype consists in increasing the reliability of work, reducing operating costs due to the absence of the need for highly qualified maintenance (since it does not require the use of complex means to ensure normal operation), improve the economic characteristics of consumers due to better quality of the output voltage. Reliability of switching thyristor rises due to the impossibility of an arbitrary change in current and switching voltage at the time of switching atsii. In addition, in the proposed device, the control pulses to the thyristors can be supplied at favorable times from the switching point of view.

When using this on-load tap-changer, the task of filtering the higher harmonic components of the output voltage is greatly simplified, since the output voltage of the on-load tap-changer contains harmonic components of only odd order, which do not change depending on the load. When the three on-load tap-changers are triggered for three-phase power supply consumers due to the mutual destruction of the harmonic components in the linear voltages of three times the output voltage of the device is much closer to the sinusoid, which makes it possible awn employed RSH {without the use of any additional filtering devices

one

Claims (1)

Claims An alternating voltage regulator comprising a transformer with one main and two additional boost windings and a single-phase thyristor bridge converter, characterized in that, in order to increase reliability, improve the shape of the curve and harmonic composition, as well as increase the stability of the output voltage, A two-winding choke and an additional single-phase thyristor bridge converter are inserted into it, and the first voltage transformer winding is connected according to but successively from one of two winding coils and choke circuit included in the DC-phase thyristor mosto810 The second inverter winding of the transformer is connected oppositely in series with the other winding of the double winding drosel and is connected to the DC diagonal of the additional single-phase thyristor bridge converter, the main winding of the transformer is connected between the input and output transistors, and the diagonal of the AC current of the single-phase thyristor thyristor circuits. the transducers are connected to the input terminals, in addition, the sum of the control angles of the thyristor pairs of each single-phase thyristor m Stow transformation bodies equal to 360, and the sum of the angles of control of the corresponding pairs of thyristors of different single-phase bridge transducers is -ISO,