SU851728A1 - Method of control of thyristor-transformer ac voltage regulator - Google Patents

Description

one

The invention relates to electrical engineering and can be used in variable voltage regulators with a load connected via a transformer, for example, in electric resistance furnaces.

A known method of controlling an AC voltage regulator with phase switching of taps of the transformer primary winding, in which the magnitude of the delay angle is determined only by the required depth of voltage regulation fl.,

The disadvantage of this method is low energy indicators inherent in phase regulation

The closest to the proposed by the technical essence is the control of the thyristor-transformer regulator of alternating voltage, made in the form of a transformer, the primary winding of which has high and low voltage tapes connected to the input terminal through controlled keys from two. third-party conductivity. The control pulses are fed at the moment of zero current values, first to the lower stage tap, then to the higher stage tap, followed by changing the order of applying the control pulses to the reverse.

The disadvantage of this method is the saturation of a transformer when switching from one voltage level to another, accompanied by a surge current, which reduces the reliability and energy performance of the regulator.

The purpose of the invention is to increase the reliability and energy performance of the regulator.

This goal is achieved by the fact that when switching control pulses from a low-voltage tap-off key to a higher tap-off key in the first half-period, the delivery of the control pulse delays by 90 e. hail, relative to the moment of power voltage passing through zero: 20 value, and when switching back in the first half-period, the control pulse is re-sent to the high-voltage tap with the delay angle, the value of which

25 1 is preformed.

In addition, to determine the angle

delays after reapplication of the control pulse to the switch key

highest voltage level since

30 voltage transfer across

the zero value is measured by the volt-second integral of the voltage on the key of the high voltage step for 90 e. hail, then, when the control pulses are subsequently switched to the low-voltage tap-off key in the first half-period, the volt-second integral is measured on the high-voltage tap-off key and the control pulse is again applied to, the volt-second integral becomes equal to the previously measured volt-second integral.

At a constant value and nature of the load, the indicated re-injection of the control pulse is carried out with a constant delay angle.

FIG. 1 is a schematic diagram of the power part of the thyristor controller, explaining the proposed method; in fig. 2 and 3 are the diagrams of currents and voltages in the circuit, where L is the voltage of the CSS network; f - voltage between tap and 5 and - zero output 1; voltage .- on key 1; 2. - measured volt-second integrals on key 1; d - magnetic induction in the core of the transformer 3, е - current i of key 1, - current i of key 2.

The thyristor controller contains thyristor keys 1 and 2 for desoldering high and low voltage levels, transformer 3, primary winding 4 of the transformer, desoldering 5 and 6 of the highest and lowest stages, zero output 7 of the primary winding, secondary winding 8 of the transformer and load 9.

Thyristor keys 1 and 2 periodically connect the AC network to the tapes 5 and 6 of the primary winding 4 of the transformer 3. When the key 1 is closed and the key 2 is open, the branch line 5 is connected to the network, and the load voltage 9 corresponds to the highest step of the regulator output voltage. When the key is closed 2 and the open key is 1, a tap 6 is connected to. network, and the voltage in load 9 corresponds to the lowest stage.

At the lowest load voltage level (Fig. 2, time interval t to) when the key 2 is closed and the key 1 is open, the maximum value of induction. 2e) in the core of the transformer, achieved at the moments of transition of the voltage Uc of the network (Fig. 20) through zero, is determined by the increase,

%

SL

25 (W -NWj,)

U is the magnitude of the network voltage; W, is the number of turns of the winding section between tap-off 5 and zero output 7;

W is the number of turns of the winding between the taps 5 and 6;

S is the cross section of the transformer core;

 - circular frequency network voltage;

Vo-volt-second integral of the network voltage for one half period.

When switching control pulses from switch 2 key of the lower stage to switch 1 of the highest stage in the first half-period, the supply of the control pulse is delayed until moment t, shifted by an angle of 90 al. relative to the moment when the supply voltage goes over zero (Fig. 2S). Turn on key 1 at the moment of 1 "s. S-delay oL- ensures the absence of saturation of the transformer during the transition to a higher voltage level, since the induction at the time t of the network voltage going through a zero value at the end of the half-period, in which switching occurs, is equal to the maximum induction in the long-term connection mode steps,

Cho

CLA

(2)

J2.)

and induction immediately goes to steady state (Fig. 2e).

The transition from a higher voltage level to a lower voltage level is performed by reverse switching of control pulses.

From key 1 to key 2. Switching on key 2 is possible only after turning off key 1. Key 1 is turned off at the time tf of the current zero crossing i (Fig. 3e), shifted with respect to the time t, the voltage of the US network crossing zero to the side upholding the inductive nature of magnetizing current and load current. After key 1 is turned off, energy accumulated in

the magnetic field of the transformer core, between the tap B and the zero output 7 appears residual voltage, which up to the moment t is more than the network voltage, and does not allow to turn on the key 2. at the moment tg v.plyuchut

switch 2, and a load of low voltage appears at load 9 (fig. 3tf). At time t, a control pulse is re-applied to the key

1 with a delay angle cLz. After re-switching on, key 1 is turned off at time t. current zero crossing (Fig. 3b% b). Switching on key 2 from: low-level soldering is performed at time r when the network voltage Uc and the residual voltage between tap B and zero terminal 7 are compared, after which the transition to the lowest voltage level is completed (Fig. 3). The choice of the delay angle oi is determined from the condition that by the time tty. The transition to the lowest step of the induction voltage in the core of the transformer must be as it would be in the steady state of switching on the lowest step of the voltage. By this condition, induction is expressed through the voltage across the winding section with tap-off 5 (Fig.). Taking into account the equations (), (2), (3), as well as 1 J di-vyvs, we get vu o j. 0 where .ft is the volt-second integral for the yarn on the winding section with tap-off 5 for the half period (Fig. 3iJ, time interval) d is the volt-second integral for the yarn (Fig. 36) “the alignment (5) is converted to Ch o N "/ 2. h-h “or get the final wand JI Cha-H, o; . where% is the volt-second integral on the voltage on the key 1 during the time from the beginning of the half-wave, in which the desolver key is re-enabled to descend the steps to the moment when the re-activation is done}% is the volt-second integral on the key 1 from the beginning of the half-wave, in which the key is turned off, until the moment shifted by 90 el. rds :. in relation to the specified time. Since the volt-second integral H is used to determine the moment of the re-activation of the higher-level transmission key, which precedes the start of the measurement of the integral, the measurement of C is performed over a time interval. Thus, after re-supplying the control pulse to the key of the higher voltage step descent from the moment the power supply voltage passes through zero, the volt-second integral of the voltage is measured the tap of the highest voltage step for 90 electra grades; then, after the subsequent switching of control pulses to the low voltage tap key in the first half period, the volt-second integral of the voltage on the higher voltage step key is measured and again fed to it control pulse when the volt-second integral becomes equal to the previously measured volt-second integral. With a constant value and nature of the load, re-apply the control pulse to the key of the higher voltage step Produced with a constant angle. Re-enabling the high-voltage tap-off key with a certain delay angle ensures that there is no induction transition when switching from a tap with a smaller number of turns to a taping with a larger number of coils. but a transient process of establishing induction in the core begins, the time constant of which is determined by the active resistance of the primary winding and Inductance ngshagnichkvani transformer. The duration of the transient process reaches hundreds of periods of network voltage. At this time, the induction state in the core is difficult to determine when switching control pulses from the low voltage tap key to the high voltage tap key with a delay angle oQ 90 el. hail, switching on the high voltage step switch key, saturation of the core is possible. 90 el. The first doluperiod guarantees no saturation of the transformer. Therefore, the application of the proposed control method of the thyristor-transformer by means of the regulator allows to avoid the emergence of the transformer, thereby increasing the reliability of the energy indicators of the regulator.

Claims (3)

1. A method of controlling a thyristor-transformer AC voltage regulator, made in the form of a transformer, the primary winding of which has high and low voltage desolders connected to the input terminal through controlled keys with two-way conductivity, by applying control pulses at the time of zero current values first, a low-level desoldering key, then a higher-level desoldering key, followed by a change in the order of supplying control pulses to the reverse one, which means that with and (the In order to increase the reliability and energy indicators of the regulator, when switching control pulses from the low-voltage tap-off key to the higher-tap tap key in the first half-period, the control impulse is delayed by 90 e-deg, relative to the moment of the supply voltage transverse through zero. , and when switching back in the first half-period, the control pulse is re-applied to the high-voltage tap-off switch with a delay angle, the value of which is determined in advance. 2. The method of clause 1t. It is also distinguished by the fact that to determine the angle of delay after re-submission The control pulse of a high voltage step descaler from the moment the power supply voltage passes through a zero value measures the volt-second integral of the voltage at the high voltage desolder key for a current of 90 el. hail, then, when the control pulses are switched to the low-level tap, the voltage in the first half-period measures the volt-second integral of the voltage on the high-voltage tap of the higher voltage, and once again controls the impulse on it when the volsecond integral becomes equal earlier measured volt-second integral. 3. The method according to claims 1 and 2, characterized in that, at constant magnitude and nature of the load, said re-supply of the control pulse is carried out with a constant delay angle. .Information sources taken in. attention during examination 1. Authors certificate of the USSR. 201501, class 02 P 13/16, 1967. 2. Lake A. N., Gordinsky I. M. Control of a thyristor converter of discrete action as a means of improving its basic characteristics. In Sat.- Optimization of electromagnetic energy converters. Kiev, Naukova Dumka, 1976, p. 135.