SU1686417A1 - Method of control over a c voltage regulator - Google Patents

Abstract

The invention relates to electrical engineering can be used in variable voltage regulators and stabilizers. The purpose of the invention is to increase the reliability when the regulator operates on the rectifier at the switching angle of the regulating switch smaller than the angle of the rectifier current relative to the voltage at the regulator input. Using regulatory 1 and shunt 2 keys alternately connect the load 3 to the mains and short-circuited. The control of the keys 1 and 2 is carried out using the control unit 4. The goal is achieved by delaying the supply of control pulses to the shunting key 2 until the control key 1 is opened. To do this, measure the current in key 1 and use the driver 8 to generate a sequence of current pulses from the moment it crosses zero. This sequence of pulses is multiplied with the sequence of pulses of control unit 4 designed to control key 2. Reliability is enhanced by eliminating the formation of a circuit of simultaneous conductivity of both keys 1 and 2. 2 Il. fe

Description

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The invention relates to electrical engineering, specifically to converter equipment, and can be used for contactless control of alternating voltage in power transformers of converter units of electrolysis plants, charging devices of capacitive energy storage devices and other consumers with a variable power factor load.

The aim of the invention is to increase the reliability when the regulator operates on the rectifier at the switching angle of the regulating switch smaller than the angle of the rectifier current relative to the voltage at the regulator input.

FIG. 1 shows a functional diagram of a device comprising an alternating voltage regulator on anti-parallel thyristor switches with forced (capacitive) switching implementing the proposed control method; in fig. 2 - timing diagrams explaining the essence of the control method at switching angle n, greater than the angle a p of the load current relative to the voltage at the input of the controller (first period) and at angle n (& switching less than the angle a p + 2tg ( the second period is the current shift relative to the voltage at the regulator input.

The device (Fig. 1) contains a regulator that includes regulating 1 and shunting 2 keys (shown by a dotted line) with forced switching, which are connected respectively in series between the input and output pins and parallel to the output pins to which the load 3 is connected, for example, a rectifier transformer - capacitive energy storage device, and key control unit 4 I and 2. Control unit 4 includes a DC network voltage synchronizer 5, a pulse-width modulator (PWM) 6, based on the vertical comparing method Pilo constant voltage Uy control and pulse distributor 1, one (double) output of which is connected to the control input of the regulating key 1. For the implementation of the proposed method, an 8 pulse generator and 9 and 10 coincidence elements (logical multiply). The elements 9 and 10 of the coincidence (conjunctors) are connected by inputs to the corresponding outputs of the distributor 7 of the width-modulated control pulses and the outputs of the driver 8 pulses, the current, and the outputs - to

the control input (s) of the shunt key 2.

Shaper 8 current pulses contains a zero-body 11 and two parallel

chains consisting of each of the galvanically isolated (optocoupler) element 12 (13) and the comparator 14 (15) connected in series to the output of the null organ 11 by a zener diode.

Optocouplers 12 and 13 are connected by inputs

counter and ensure the division of the two-period pulse sequence by the current generated by the null organ 11 into two half-wave ones; galvanic

isolating the power circuit and the control system of the regulator: perform the photoresistance function; Comparators 14 and 15 services / 1 1 I signal amplification and the establishment of a threshold of protection operation

A device that implements the proposed method for controlling an AC voltage regulator operates as follows.

In each half period of voltage 16

PWM network 6, synchronized with network voltage 16 by synchronizer 5, two anti-phase sequences of pulse-width modulated pulses 17 and 18 are formed. One sequence

pulses 17c distributor 7 pulses

enters directly to the securing key 1, and the other 18 through elements 9 and

10 matches per shunt key 2.

When closing the control key 1

the load 3 is connected to the mains and a current 19 flowing from the mains voltage 16 at an angle a flows through it. p, a load 20 is applied to the load 3 (shaded areas) during the flow of current

19, in the control switch 1 at the input of the null organ 11, a signal 21 to the flow appears, which is the sum of the voltages - the voltage drops at the power transition in the intervals y a к k and т t - к a and f + l of the closed

the key 1 and the reverse voltage in the interval o (X: Ј l - “to the open-ended key 1. The voltage drop across the power transition of the key (thyristor) 1 depends on its internal resistance and flowing tsk 19, and the voltage level U0 is determined the input parameters of a zero-organ 11 (performed, for example, on an operational amplifier and a two-channel zener diode installed at its input). The zero-organ 11 on

the moments a + LT1 (where n 1,2,3 ...) of the current 19 in the key 1 through zero (according to the signal 2, a sequence of two-half-wave pulses 22 in the current is formed, which, as it passes through the chain, the oltrons 12 and 13 are comparators 14 and 15 is divided into two sequences of half-wave pulses 23 and 24, arriving at the input of elements 9 and 10. Matches 9 and 10 produce a logical multiplication of pulses 23 and 24 and width-modulated pulses 18, intended to control the key 2, and from the outputs elements 9 and 10 to the control input of the shunt cable 2 is fed the resulting control signal 25. At a given switching angle a "determined by the control unit 4, the shunt switch 2 closes the signal 25 and the regulating switch 1 opens at the same time and a reverse voltage appears on it, which at a limited level U0 enters the zero-body 11. In the resulting short-circuit circuit key 2 - load 3 in the same direction the current decaying along the exponent 19 flows. At the moment a lk, uniquely connected with the angle “-“ to switching, the shunt key 4 opens, simultaneously The control switch 1 closes, connecting the load 3 to the power supply in the interval l - (and. g s p l. In the next half-period of voltage 16 of the network, the processes in the controller proceed analogs

Suppose that at the beginning of the second (2 l i s / 4 l, voltage period 16 of the network due to the action of counter electromotive force (capacitive energy storage)), the rectifier valves were locked, and the control voltage Uy at the PWM input 6 changed; pulses 17 and 18 will become equal to the duration of pulses 26 and 27 of control keys 1 and 2, respectively, and the switching angle will change to an angle (t ft and will be less than the angle a-eu-t 2l of the load current 19 relative to voltage 16.

From the moment of 7K, the impulse 26 of control by the regulating key 1 is absent, however, the key 1 is still closed in the interval "" a p + 2 l until the current 19 passes through zero. If, at the specified interval, the control pulse 27 is supplied directly to the shunt switch 2, then both keys will be closed, which will cause an emergency condition of the controller.

However, in the device that implements the proposed method, this will not happen. The duration of the current signal 21 becomes equal to the pulse duration 28. The duration of the signal 29 at the output of the null organ 11 will change and now, elements 9 and 10 will coincide with comparators 14 and 15

receive half-period pulses 30 and 211 current. Now the duration of the resultant control signal 32 of the shunt key 2 will become less by the duration of the width modulated control pulse 27 by. In this case, the load 3 will be closed by the key 2 only from the moment a p + l p of the passage of the current 19 through zero, i.e. unlocking the key 1. Further processes proceed as previously discussed.

Using the proposed method of controlling an AC voltage regulator eliminates the formation of a circuit of simultaneous conductivity.

both keys and, thereby, increase the reliability when operating the rectifier controller with counter electromotive force (in a closed automatic control system) and ensure the protection of the device from emergency operation.

Claims (1)

Claim method The control method of the variable voltage regulator containing the regulating and shunting keys with forced switching, with the control key connected in series between the input and output pins, and the shunt key - parallel to the output pins, which means that form two antiphase sequences of pulse-width modulated pulses that are used to control the regulating and shunt keys, and the adjustment key controls the first of the generated sequences of pulse-width modulated pulses, which is designed to increase the reliability of the regulator when the rectifier at the switching angle of the regulating key is smaller than the angle of the current of the rectifier relative to the voltage at the regulator input, the current in the regulating key is measured, the current sequence of pulses is generated by the moments of its crossing through zero, the second of these sequences is carried out -modulated pulses with a said sequence of current pulses and a resultant signal are controlled by a shunt key. bjl Fie.2