SU1422291A1 - Method of protecting parallel thyristor current inverter - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to increase the power reliability of the responsible consumers of electricity by reducing the power interruption time when the protection is triggered. In case of a short circuit in the network of loads, the alarm signal from the current sensor 13 acts on the control unit 11 with keys, which stops supplying control pulses to key 9. This turns on damper 3 and control unit 5 stops supplying pulses to the inverter thyristors. After the thyristors of the inverter 1 are quenched and the extinguishing device 3 is prepared for the next operation cycle, the control unit 11 is supplied with control pulses to the thyristors of the additional switch 10, which commutes the tap of the output transformer 8. In this case, the switching capacitors are discharged by the short-circuited load. Then, after a predetermined time, the control unit 5 sends control pulses to the inverter thyristors. 2 Il. (/)

Description

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i The invention relates to electrical engineering.

; The purpose of the invention is to increase the reliability of power supply to responsible consumers of electricity by reducing the time of power failure when protection is triggered.

Figure 1 shows the functional diagram of the device that implements the method of protection; Figure 2 shows the oscillogram Mjbi of the transition of a three-phase parallel and current inverter from the nominal operation mode to the short circuit mode and the load for different points of the beginning of the short circuit mode. A: The device (Fig. 1) consists of an inverter 1 containing an input reactor top 2, an extinguishing device 3, a switch 4 with a switch control unit 5, a reactive power compensator 6 with a compensator control block 7 (jaTopoM, an output transformer 8, contactless switches 9 and 10, key management unit 11, current limiting reactor 12, current sensor 13. The main thyristor switch 9 is connected to the main terminal of the transformer 8, and an additional switch 10 is connected to the tap output by block 11 control tim keys whose input is connected to the output of the current sensor 13. Block 11 outputs are connected with the control key inputs 9 and 10 and with a block 5 switch control inputs 4 of quench tron devices 3.

Figures 2 (a and b) show graphs of the counter-emf 14, the voltages on the switching capacitors 15, and the load current of the short-circuited phase 16.

The device that implements the method works as follows.

In the initial state, as long as the load current does not exceed the permissible value, it is powered from the main terminal of the transformer 8 through the key 9. The key 10 is then turned off. In the event of a short circuit in the network of loads, the alarm signal from the current sensor 13 acts on the key management unit 11. The block 11 stops the supply of control pulses to the thyristors of the key 9, which commutes the main output of the output transformer 8, and simultaneously sends the corresponding command to the blocks 3 and 5. When

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This includes the damping device 3 and the block 5 stops the supply of pulses to the thyristors of the inverter 1. After the thyristors of the inverter 1 are quenched and the damping device 3 is prepared for the next operation cycle, through time t relative to the moment of removal of the control pulses from the key 9 from block 11, control pulses on the thyristors of the additional switch 10, which commits the tap-off of the output transformer 8 (the introduction of the delay t is caused by the necessity to eliminate the possible short circuit of the winding v; the driving transformer through the thyristors new and additional keys for simultaneous operation). In this case, the switching capacitors are discharged by the short-circuit load current. Then, after time t, with respect to the moment of the removal of the control pulses from the key .9-the switch control block 5 delivers control signals to the thyristors of the inverter. In this case, the inverter is turned on for a short-circuited load through the additional switch 10.

Additional thyristor key 10 works until the protection device in the short-circuited load circuit disconnects it from the inverter. After the elimination of the short circuit, the key management unit 11 stops the supply of control pulses to the thyristors of the additional key 10. Then with a time delay relative to the moment of removal of the control pulses from the additional key (introduced in order to eliminate the output transformer winding short circuit), the unit 11 delivers control pulses to the main key 9. Thus, the reverse transition to the normal operation of the inverter is carried out.

As can be seen from the oscillograms (figure 2), the nature of the process depending on the moment of the start of the short circuit mode can be different. The time of operation of the primary key thyristors after removal of control pulses from them and the time of discharge of the capacitors vary widely. In any case, the key management unit 11 must provide a delay time t sufficient to reduce the current of the primary-key thyristors to zero, and a delay time sufficient to discharge the switching capacitors.

to a voltage of 10-15% of the nominal value.

The tap voltage of the output transformer 8 and the inductance of the current-limiting reactor 12 are calculated so that even in the dead short circuit mode at the output terminals of the device, the inverter operates at the fundamental frequency,

Claims (1)

Invention Formula The method of protection of a parallel thyristor current inverter containing a forced shutdown of the thyristors and an output transformer, the secondary winding of which is equipped with the main and additional terminals for connecting the load, which means that in case of output Hbw exceeding the output current with a given value windings of the output transformer, remove the control pulses from the thyristors of the current inverter, perform their forced locking, and then after a specified time produce supplying control pulses to the thyristors of the current inverter and connecting the load to the additional output of the secondary winding of the output transformer, characterized in that, in order to increase the power reliability of the responsible power consumers by reducing the time of interruption of the power supply when the protection operates, connect the load to the additional output of the secondary winding of the output transformer produced immediately after the forced closure of the thyristors of the current inverter, and then after a specified time The above control pulses are applied to the thyristors of the current inverter. n shY |