SU1008868A1 - Thyristorized voltage inverter - Google Patents

Abstract

THYRISTOR INVERTER OF VOLTAGE, containing two arms connected in series between power rails per phase of load. each of which is made ", ff-: in the form of a series-connected nonlinear reactor and a circuit of an oppositely connected thyristor and diode shunted by an RC circuit, the common point of the shoulders forming the output phase output of the inverter, as well as switching nodes in the form of a three-terminal network the number of load phases, each of which is connected by one of its three outputs to the corresponding output phase output of the inverter, is different from the fact that, in order to reduce the magnitude of the voltage acting on the thyristors, the other two A output of each of the switching nodes i connected to the taps of the corresponding nonlinear (A GOVERNMENTAL reactors 00 and cx: 00.

Description

- Fig. / The invention relates to converter technology and can be used in high voltage installations for converting the type of current. The known circuit of the inverter, which contains working tiribtory with back-to-parallel diodes and a terminal unit-1. The disadvantage of this inverter is low reliability because the valves are subject to high current and voltage rise rates. Closest to the proposed voltage inverter, containing in phase connected in series between the poles of the source arms, consisting of a nonlinear reactor, counter-parallel thyristor, diode and RC circuit, the common point of the shoulders being the output of the inverter, as well as the switching node with one output connected to the output of the inverter 2. A disadvantage of the known device is an increased voltage acting on the valves. The purpose of the invention is to reduce the voltage acting on the valves. This goal is achieved in those in the thyristor voltage inverter., Containing two arms connected in series to the load phase, each of which is fulfilled in the serially connected nonlinear reactor and the circuit of the parallel-connected thyristor and diode shunted RC circuits, with the common point of the shoulders forming the output phase output of the inverter, as well as the switching nodes in the form of three-terminal circuits, according to the number of load phases, each of which is connected by one of its three outputs to the corresponding the other output phase output of the inverter, the other two outputs of each of the switching nodes are connected to the tapings of the corresponding non-linear reactors. g :, FIG. 1 shows a device diagram; in fig. 2 - voltage and current diagrams. Working thyristors 1 and 2 with matching diodes 3 and 4, as well as RC circuits consisting of resistors 5 and 6 and capacitors 7 and 8, are connected in series with operating nonlinear reactors 9 and 10 between the inverter supply buses. The switching node consists of thyristors 11 and 12, reactor 13 and capacitor 14. One output of the switching node is connected to the output of the inverter, and the other two to the tapings of nonlinear reactors 9 and 10. The device operates as follows. On the working thyristors 1 and 2 and the switching thyristors 11 and 12, control pulses are applied in a certain sequence. Thyristors 1 and 2 alternately conduct current. To turn on the next working thyristor 1 (2), the previous 2 (1) must be turned on. This function is performed by the switching unit, circled in the drawing by a dotted line. This block can be performed by any other known scheme. When switching on the switching thyristor, a current pulse is created, 2-4 times higher than the load current and directed towards the working current of thyristors 1 and 2.. Nonlinear reactors 9 and 10 in the working thyristor circuit limit the rate of current rise and voltage, reduce thyristor losses at the stage of switching on and, together with RC circuits, reduce the voltage spikes on the valves. When the working thyristor 1 (or 2) is turned off by the current of the switching node, the reactor 9 (or 10) must be remagnetized to prepare for switching on in the next period. A similar solution is used in high-voltage inverters, because the placement on the cores (1 of reactors 9 and 10 additional demagnetizing windings, practiced in low-voltage installations, is difficult because it is difficult to ensure the required level of insulation. Fig. 2 shows diagrams the voltage Uc on the switching capacitor 14 of the switching current IK and the load current of the thyristor 1c, as well as the voltage U i on the backstop: from a thyristor not conducting current. At time I, when the difference 1 - IH reaches the required value, the reactor At time tj, the voltage of the capacitor 14 is divided between the inductances of reactors 9 and 13. The voltage applied to the reactor 9 is added to the source voltage and creates a voltage surge on the opposite, not included, voltage of the inverter, the valve 2.4 and reactor 10. A decrease in the number of turns of the reactor 9 to which the switching node is connected leads to a shift in the moment tj to the right (in the direction of delay), i.e. towards lower voltages on the capacitor 14. On the other hand, the inductance of part of the reactor 9 decreases and the autotransformer effect increases. Taking into account the effects of these I factors, the voltage at the reactor 9

equals j

KwV -w,

LS

Wp

cL,

and

where LI, LQ is the inductance of the switching reactor and part of the reactor 9 with a tap;

W,

W "the number of turns of the reactor 9 and taps;

and the voltage across the capacitor;

K -

coefficient of proportionality.

Taking into account that usually Lj, Lg, from this formula, it is obtained that a decrease in the number of turns W ,, desoldering of reactor 9 leads to a decrease in voltage surge on the opposite arm of the inverter. However excessive

a decrease in WQ is unacceptable, since it can lead to the fact that reactor 9 will not remagnetize. In extreme cases, Wo "0 and WQ W get V (y O and u and 1

The outcome of the conditions of the Hc1 reliable reversal magnetization Z is equal to 0.5-0.8 depending on the ratio of the amplitude of the switching circuit and the load current.

Thus, switching the switching node to the tapings of non-linear operating reactors leads to a reduction in voltage emissions of 15-25%, which requires a smaller class of thyristors. This is especially important in high-voltage installations, where valves up to several tens-co-ten are switched in series. Such a solution can reduce the cost and size of the installation.

f

Claims (1)

(5 7) TYRISTOR VOLTAGE INVERTER, comprising two arms connected in series between the supply buses per phase load, in the form of a series-connected non-linear reactor and a circuit of oppositely connected thyristor and diode, shunted by an RC circuit, and the common point of the arms forms an output phase output inverter, as well as switching nodes in the form of triples in the number of load phases, each of which is connected by one of its three terminals to the corresponding output phase output of the inverter, which means that , To reduce the voltage level acting on the thyristors, the two other output of each of the switching nodes are connected to respective taps of the nonlinear