SU1474791A1 - Method of controlling current inverter - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to converter technology, and can be used in thyristor frequency converters. The aim of the invention is to increase the stability of the inversion by eliminating the operating modes of the inverter without pausing the load current. In the inverter control method, the thyristor control pulses of the inverter cell and the thyristor, which create a load current pause, are generated, and the inhibition pulses are continuously formed, equal in duration to the interval at which the voltage of the power source in absolute value exceeds the voltage on the load. The resulting inhibit pulses and control pulses of the reverse thyristor are matched by formation time and, at the same time, these pulses are prevented from supplying control pulses to the reverse thyristor, and at the moments of the end of the effect of the inhibit pulses, control pulses are generated and fed to the thyristor creating a load current pause. 2 Il.

Description

The invention relates to electrical engineering, in particular, to converter technology, and can be used in thyristor frequency converters.

The aim of the invention is to increase the stability of the inversion by eliminating the modes of operation of the inverter without pausing the load current.

Figure 1 is a diagram of an inverter and control system that implements the proposed method; 2 shows time diagrams of the current i H and the voltage Uc of the load, with the re-formation of control pulses by the inverse thyristor Ion (a) and without

re-formation of these pulses (rf).

The inverter consists of a thyristor inverter cell 1, containing thyristors 2-5, a switching capacitor and a load 6 in the diagonal of an alternating current of the inverter cell, smoothing the throttle 7 in the DC circuit, and the smoothing choke 7 is bridged by an inverse thyristor 8, the control system 9 that includes driver of 10 reverse thyristor control pulses connected through matching unit 11 with reverse thyristor 8, driver of impulses of control thyristor

4 1

WITH

,

inverter cell switches connected to the thyristors 2-5 of the inverter cell 1, the generator of 13 inhibit pulses associated with the inputs to the load b and the power source, and the output from the matching unit 11.

The inverter works as follows.

At time ti (Fig. 2a), a pair of thyristors of the inverter cell 1 (Fig. 1), for example, thyristors 2 and 3, from the driver 12, serves a control pulse iy (2, 3). At the same time, a current 1I flows through Vjerm, equal to the current of the smoothing throttle 7, and the voltage across the load ITH varies according to a law close to sinusoidal. With a certain time delay corresponding to a given control angle, at the time ta a pulse is generated to control the reverse thyristor t0 (driver 10). The instantaneous voltage value at the load U and the voltage at the power source E d are simultaneously and continuously measured. Signals proportional to 11 c and E are fed to the driver 13, which generates a inhibit pulse equal in duration to the interval at which the power supply voltage exceeds the stress on the load in absolute value (shaded area). In block 11, the impulse inhibit collision

i, and the reverse thyristor control pulse i. 6 is matched against the formation time and, while simultaneously generating these pulses, the control pulses are prevented from being supplied to the reverse thyristor 8, and at the moment the t3 inhibit pulse ends, the driver 10 regenerates the control pulse 1OH, which is fed to the reverse thyristor 8. At the same time, the thyristor 8 is unlocked smoothing throttle 7 is closed through this thyristor, and the currents of the power source and load fall to zero. If the control pulse of the reverse thyristor i does not coincide in the passage time with the inhibit pulse (Fig. 26), then the supply of this pulse to the thyristor 8 is not prohibited. In this case, the control pulse is not re-formed.

Then, at a given time t4, equal to the half-cycle of the output frequency of the converter, include

Q

0

five

0

five

0

five

0

five

a pair of thyristors of the inverter cell, thyristors 4 and 5). The processes occurring in the inverter are repeated. Further continue alternate switching of the thyristors of the inverter cell 1 and the reverse thyristor 8.

By varying the time delay between the control pulses of the inverter cell 1 and the reverse thyristor 8 (control angle), pulse-width control of the load current, as well as control of the output voltage of the inverter, are performed.

The use of this control method allows you to unlock the reverse thyristor 8, taking into account the level of voltage. neither on the load and the power source. This eliminates the conditions in which a pause in the load current is not formed. The presence of a load current pause allows to increase the locking angle of the thyristors of the inverter cell 1, which contributes to increasing the stability of the inversion, reduces the likelihood of the inverter tipping over, and expands the frequency range of the converter.

Claims (1)

Formula invented and A method of controlling an inverter current, containing a thyristor inverter cell with a switching capacitor and a load in the diagonal of an alternating current, smoothing a choke in a DC source circuit, the smoothing choke is bounded by a reverse thyristor, which consists in forming thyristor control pulses the inverter cell and the reverse thyristor, the corresponding thyristors of the inverter cell are unlocked for the repetition interval, then the reverse a thyristor, characterized in that, in order to increase the stability of the inversion, prohibition pulses are continuously formed, equal in duration to the interval in which the voltage of the DC source exceeds the absolute value of the voltage on the load, the prohibition pulse and pulses coincide control of the reverse thyristor and during their prohibition of the supply of control pulses to the reverse thyristor, and at the moments of the end of the action of the inhibit pulses, the supply of control pulses to the reverse t Ristori. t t