SU877785A1 - Method of control of pulse-width thyristorized regulator - Google Patents

Description

I

The invention relates to electrical engineering, and specifically to thyristor editors operating in a pulse-width manner.

Thyristor power controllers are known and fairly well used as output nodes of pulse-width controllers. They are most effective for objects with large iner-. tionality (for example, electric furnaces, heat heaters, etc.). To the device, the output node of such devices, a thyristor control unit, presents a number of specific requirements .15

In most cases, the load of the thyristor blocks is purely active, and with an arbitrary thyristor switching on moment, the problem arises: to limit the rate of current rise when they are switched on 20, since the thyristor parameter di / dt (slew rate) is finite and limited. This nepJBoe is a specific requirement for such devices. 25 This task is often solved by the use of current-limiting reactors (saturable), however, this is not very profitable economically at high power.

The second requirement for a thyristor unit is to reduce the level of radio interference that occurs when the thyristors are turned on at arbitrary points in time.

Both of these requirements, when operating a thyristor unit, are observed when synchronizing the moment of switching on the thyristors with the moment of zero crossing of the mains voltage applied to the thyristor unit.

The most simple is the synchronization task for a single-phase Christ controller, either by synchronizing the arrival to the thyristors of the control signal, or by the timing of the resolution of the arrival of the control signal 1.

Both are simple and reliable in operation, but a serious disadvantage of this method is the limited application for several phases. Devices that implement these methods, as a rule, contain two-input devices such as drivers, to the inputs of which a variable and control voltage is applied. At the output of such odds, the onset of the control signal always

coincides with the moment of voltage passing through zero.

There is a known method for controlling the pulse-width thyristor 1 by the regulator by unlocking each thyristor at the moment of changing the polarity of the voltage on it from the reverse to the direct 2

The disadvantages of this method are the difficulties of applying them to multiphase-thyristor devices: an increase in the complexity of the circuit with an increase in the number of phases, i.e. the need to apply several logic elements or drivers, the number of which must be equal to the number of phases or thyristors; non-universality, i.e. the inability to change the number of phases of the thyristor controller without changing the control circuit; the difficulty of galvanic separation of power and control devices between themselves and between phases.

The purpose of the invention is to obtain a universal method for synchronizing thyristor blocks, allowing operation with any number of phases, i.e. expansion of the field of application.

This goal is achieved by controlling the pulse width controller by unlocking each thyristor at the moment of changing the polarity of the voltage on it from the back to the direct unlocking pulses, start to feed the thyristor of an arbitrarily chosen synchronization phase at the moment of changing the polarity of the voltage applied to this thyristor, from reverse to direct and simultaneously to the thyristors of the remaining phases, to which at the moment of the beginning of the supply of the triggering pulses, the reverse polarity is applied.

In order to reduce the power of the control system, it is advisable to stop the supply of the unlocking pulses at the time of changing the polarity of the voltage applied to the thyristor of the synchronization phase from direct to the opposite to the said thyristor and simultaneously to the thyristors of the other phases, to which 8 direct polarity voltage.

Fig. 1 shows a diagram of a device that implements the method proposed in Fig. 2 - diagrams with reference to the case of three phases.

A device for implementing the proposed method contains a block 1 for obtaining an enable signal synchronized, for example, ro phase A, generator 2 and 3 control pulses, thyristor controller 4 (for 3 phases; A, B, C phases of the power supply), thyristors 5-10 regulator.

The diagram (Fig. 2) shows the voltage of phase A - 11; the signal at the output of block 1 (figure 1) - 12; sequence of generators - 13; the distribution of thyristors in groups connected to generators - 14.

The method is carried out as follows (for example, a three-phase regulator). 5 The synchronization phase is selected. A. Block 1 is designed so that when a signal from the PWM arrives at it, the output signal appears at the moment of zero crossing of the selected phase (A) and lasts for the duration of the signal from PWM, (Fig.2-12). This signal is authorizing the operation of generators 2 and 3 (figure 1). The sequence of operation of the generators is shown in FIG. 2-13.

5 The group of thyristors 5, 7, 10 is connected to the generator 2, and the group of thyristors b, 8, 9 to the generator 3. The working half-periods for the thyristors are shown in FIGS. 2-14.

0 Suppose the moment of arrival of the resolving signal came at the time of crossing the voltage of phase A, and after this moment a negative half-period of voltage follows

5 phase A (Fig.2-14). Generator 2 starts operating and the control pulses are applied to a group of thyristors 5, 7, 10. However, only thyristor 5 is turned on, since the direct voltage is only on it, and on thyristors 7, and 10 the opposite is true (Fig 2-14). After 1/6 of the period, the direct voltage appears on the thyristor 10 and it turns on and, after 2/6 periods, the thyristor 7 turns on (Fig. 2-14). With a half cycle change, the generator 2 turns off, and the generator 3 turns on and the control pulses are applied to a group of thyristors 6, 9, 8, which are sequentially turned on. This process is repeated for the duration of the enable signal.

With a different number of phases, the Thyristor group is connected to the generator 2, to which the direct voltage 5S is applied at the moment of changing the sign of the voltage from minus to plus of the selected synchronization phase, and to the generator 3 the remaining thyristors.

0 Thus, the synchronization of the inclusion of all thyristors (regardless of the number of phases) is carried out in accordance with the proposed method using only one synchronization device.

Claims (2)

1. A method of controlling a pulse-width thyristor controller by unlocking each thyristor at the time of polarity variation of the voltage across it from reverse to direct, characterized in that, in order to expand the field of application, the uncoupled pulses start to apply to the thyristor of a randomly selected synchronization phase at the time of changing the polarity of the voltage applied to this thyristor, from the reverse to the direct and simultaneously to the thyristors of the other phases, to which, at the moment of the beginning of the supply of the triggering pulses, a voltage is applied at. polarities.  2. The method according to Claim 1, which differs from that, that the triggering pulses cease to be supplied at the time of polarity reversal of the voltage applied to the thyristor of the synchronization phase, from direct to reverse to said thyristor and simultaneously to thyristors the remaining phases, to which at the time of the disconnection of the unlocking pulses, a direct polarity voltage is applied. Sources of information taken into account in the examination 1. The UK patent 1483896, cl. H 2 H, 1976. 2. Japanese Patent 52-31071, cl. 58 H 1 72, 1977. MIME S 7 Yu  V ill ft Time ff /