SU682992A1 - Method and apparatus for controlling a converter on gate members having an a-c output - Google Patents

Description

The device (see Fig. 1) contains thyristors I and 2, transformer 3 with primary winding 4, load 5, phase control blocks 6 and 7, resistors 8 and 9, a control unit 10, a phase-sensitive detector 11 and a current transformer 12.

The control method is illustrated by the example of the AC voltage regulator, but the essence of the processes does not change when the transformer is connected to other types of converters on the key elements. With a linear load and asymmetry of inclusive pulses, one-sided saturation of the transformer core occurs, the magnetizing current (see Fig. 2, d) increases sharply, acquiring an asymmetrical shape with respect to smallpox time. The maximum value of the magnetizing current occurs at the time when the network voltage passes through zero in only one direction (in Fig. 2, d is the transition from positive to negative values). The primary current of the transformer (see Fig. 2, d), equal to the current of magnetization and the reduced load current (see Fig. 2, c), also acquires an asymmetrical shape. As in the magnetizing current curve, there is a large difference in the values in the primary current curve, especially for the moments when the network voltage passes through zero. By measuring the amplitudes of the primary current at the moments when the network voltage passes through zero, current signals are obtained (see Fig. 2, e) containing a constant component, which is used to eliminate the asymmetry of the pulses. The asymmetry of the switching pulses is changed until the magnetizing current (see Fig. 3, d) and, accordingly, the primary current (see Fig. 3, e) take a symmetrical shape with respect to the time axis. In this case, the transformer leaves the saturation state.

When subtracting the primary current values of the secondary current from the primary current, the sensitivity of the response to the saturation of the transformer increases.

With a non-linear load, for example, of the type half-wave rectifier, the transformer is saturated even with symmetry of the switching pulses, and the magnetizing current (see Fig. 4, d) is asymmetrical about the time axis. Similarly, by measuring the amplitudes of the primary current at times of voltage crossing the network through zero, current signals are obtained (see Fig. 4, e), which are used to introduce asymmetry of the switching pulses so that the magnetization current becomes symmetrical (see Fig. 5, d) and the transformer is out of saturation.

The method allows current transformers to be used as sensors, despite the fact that the average value of the current in the secondary winding is always zero.

In the proposed device for carrying out the method, the measurement of the amplitudes of the primary current at times of a zero-voltage transition is produced by a phase-sensitive detector 11, which is connected to a current sensor 12, made in the form of a current transformer. The signal from the detector output is fed to the input of the automatic control unit 10, which generates a signal t / ynp2 to change the asymmetry of the switching pulses supplied to the inputs of the blocks 6 and 7 of the phase control. Inclusion pulses from the outputs of blocks 6 and 7 are applied to the control electrodes of thyristors 1 and 2. A change in the asymmetry of the switching pulses occurs until transformer 3 is not

out of saturation. The magnitude of the voltage across the load is controlled by a symmetrical change in the switching pulses as a function of the control voltage t / resistor supplied through resistors 8 and 9.

Claims (3)

1. The method of controlling the converter on key elements with AC output included in the primary circuit of the transformer, by periodically supplying control pulses to the keys with subsequent measurement and comparison of parameters characterizing the positive and negative half-waves of the primary circuit current, and changing the duration and phase of the control pulses, providing a zero value of the difference between these parameters, characterized in that, in order to increase reliability and energy indicators, the instantaneous value of the current in the primary circuit at the moments of transition of the output voltage through . 2. A method according to claim 1, characterized in that the reduced value of the current of the secondary circuit is subtracted from the current of the primary circuit of the transformer. 3. A device for implementing the method according to claims. 1 and 2, containing a transformer, the primary winding of which is connected to the input terminals via the primary winding of the current transformer and thyristor switches, the control electrodes of which are connected to the outputs of the phase control units connected by their inputs to the regulator output, and the secondary winding is connected to the output terminals characterized in that it is equipped with a phase-sensitive detector, the inputs of which are connected to the input terminals and the secondary winding of the current transformer, and the output is connected to the input of the regulating body. Sources of information taken into account in exertizs 1. US patent No. 3829794, cl. H 02M 7/55, 1974. figg FIG 3 fug. at one - 17 u if five