Abstract
Three-phase thyristor switches are designed for pulsed formation of inrush currents of electrical equipment with their subsequent shunting in steady state operation. In transformer substations, they perform a bumpless turning on of a power transformer by connecting its primary winding first to two phases of the network at the moment of zero crossing by the phase voltage of the network third phase, and then to the network third phase at the moment of zero crossing by the line voltage of the other two network phases. In this case, the starting currents of the transformer almost immediately enter the steady state without the appearance of constant components in the magnetization currents and voltage drop. To expand the functionality of thyristor switches, it is proposed, in addition to bumpless turning on of a power transformer, to disconnect it without arcing between the contacts of electrical equipment, as well as to carry out continuous voltage regulation for consumers when voltage in the network changes. The proposed method and structure for its implementation on the basis of two three-phase thyristor reactor keys and a capacitor bank make it possible while changing the network voltage to stabilize the generated reactive power at the input of the substation without creating the current distortions in the power transformer and power transmission simultaneously with stabilizing the substation output voltage. Modeling and research of the start-regulating device as part of a transformer substation was carried out in the MatLab environment. The results of numerical experiments in stationary and dynamic modes of the substation operation showed the feasibility of using the developed technical solutions for the industrial power supply system.
Highlights
The commercially available thyristor AC voltage regulators with natural switching (TRVN) have relatively small overall dimensions, high speed and operational reliability
Experimental studies on the use of TRVN as start-regulating devices for power transformers (PT) of substations 6 (10)/0.4 kV did not find practical application. This is due to the fact that with an increase in the control angle of the thyristors, TRVN consumes additional reactive power and introduces distortions in the output voltage and input current of the substation [2,3,4,5,6,7,8,9,10,11]
The proposed reactor-thyristor AC voltage regulator with natural switching (R-TRVN) device is installed on the high side of the PT in the same manner as the mechanical on-load tap-changer, and under continuous regulation it provides stable voltage for consumers with voltage deviations from the nominal by ± 10%
Summary
The commercially available thyristor AC voltage regulators with natural switching (TRVN) have relatively small overall dimensions, high speed and operational reliability. An increase in the inductance in the PT circuit during the pulse-phase control of the alternating voltage at the reactors neutralizes the additional reactive power generated by the capacitors, providing a slight deviation of the network phase current from voltage and maintaining the maximum cosφ value This is one of the great features of the proposed device. It contains the following elements and modules: three single-phase sources forming a three-phase network (Uа, Ub, Uc); power line W; input high-voltage switch Q1; high-voltage switch Q2 in the battery circuit of the capacitor bank CB; contactor AC; modules of the main VS-1 and additional VS-2 thyristor switches with a pulse-phase control system PPCS-1 and PPCS-2; main L1 and additional L2 reactors; power transformer PT; active-inductive load Z and other auxiliary elements
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