RU2505899C1 - Integrated apparatus for melting ice and compensation of reactive power - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: integrated apparatus has two three-phase bridge converters on fully controlled semiconductor rectifiers, which are shunted by anti-parallel connected diodes, a capacitor bank at the direct current side of the converters, a first three-pole switch and two series-connected three-phase chokes, one of which is connected in parallel to a second three-pole switch - at the alternating current side. When melting ice, the first converter operates in a controlled rectifier mode and the second converter operates in self-contained voltage inverter mode, the output of said inverter being connected through a third three-pole switch to wires of the overhead power line which are closed at the opposite end, for simultaneous melting of ice thereon with low-frequency alternating current, where the inductive component of the resistance of the wires almost has no effect on the effective melting current value.

EFFECT: easy organisation and shorter duration of the melting process with simultaneous reduction of the amount of additional switching equipment.

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Description

Technical field

The invention relates to the field of electrical engineering and can be used in high voltage substations requiring the use of devices for melting ice on the wires of overhead power lines (VL) and reactive power compensation.

State of the art

Known combined installations for controlled ice melting on overhead lines and reactive power compensation, based on a three-phase bridge converter (two or three level) on fully controllable power semiconductor devices - IGBT or lockable thyristors (see US patent No. 6433520, published on 08.13.2002 ; patent RU No. 2376692, publ. 12/20/2009).

The converter contains three arms on series-connected fully controllable semiconductor gates, shunted by on-board diodes. When implementing a synchronous static compensator (STATCOM), the AC converter is connected to the three-phase winding of the power transformer through the first three-pole switch and the reactor group of two three-phase inductors, and a capacitor bank acting as a constant voltage source is connected to the DC output of the converter. In parallel with one of the three-phase reactors, a second three-pole switch is connected, the contacts of which are open when the device is in reactive power compensation mode.

When melting ice, the converter is transferred from compensation mode to controlled rectifier mode, with an output connected via a two-pole switch or two single-pole VL wires switches, on which ice is smelted with direct current. The contacts of the second three-pole switch are closed in this mode.

The advantage of using direct current is the ability to melt ice on long lines, because the current value is limited only by the active component of the overhead lines.

When using a controlled rectifier as the power source, the “wire-two-wire” connection option is usually used. First, a circuit formed by one of the wires of the line and two other wires connected in parallel is connected to the output of the rectifier. At the end of the ice melting on the first wire, a second and then a third wire is connected in its place. However, with this method, the organization of ice melting is significantly complicated, the melting time is increased, a large number of additional switching equipment is required at both ends of the line with its periodic switching during the melting process.

SUMMARY OF THE INVENTION

The technical effect of the invention is to simplify the organization and reduce the duration of the process of melting ice through a combined installation while reducing the number of additional switching equipment on the overhead line.

To achieve this effect, a second three-phase bridge converter is introduced into the installation using fully controllable semiconductor valves, shunted with on-board diodes, the DC terminals of which are connected to the DC outputs of the first converter, the three-phase terminals through the third three-pole switch are connected to the overhead lines for ice melting, and through the fourth three-pole switch with three-phase terminals of the first converter.

The implementation of the invention in view of its development

The essence of the invention is illustrated by the drawing in figure 1.

The proposed installation contains the first three-phase bridge converter 1 on fully controllable semiconductor switches (for example, IGBTs) shunted by on-board diodes, connected from the AC side to the three phases (A, B, C) of the secondary winding of the transformer or AC network through the first a three-pole switch 2 and three-phase inductors 3, 4, parallel to one of which a second three-pole switch 5 is connected. If the function of the current-limiting inductor 3 is sufficient suppl inductance of the leakage flux of the transformer secondary winding to which the AC input transducer 1. By DC terminals of the first inverter 6 is connected a capacitor bank and the DC terminals of the second three-phase bridge inverter 7 in a fully controllable semiconductor switches, diodes shunted counter included. The three-phase leads of the converter 7 through the third three-pole switch 8 are connected to the overhead lines for melting ice and through the fourth three-pole switch 9 are connected to the three-phase leads of the converter 1. Signals for controlling the state of the controlled valves of the converters are generated by the control device 10.

Installation works as follows.

When melting ice, converters 1 and 7 form a frequency converter with a pronounced DC link. The first of them works in a controlled rectifier mode, and the second in a three-phase autonomous inverter mode. The three-phase load of the inverter with the phase connection as a star is OHL wires, closed at the opposite end of the line and connected to the inverter output through the contacts of the three-pole switch 8. In the ice melting mode, the contacts of the switch 9 are open, and the contacts of the switch 5 are closed for more efficient use of the power of the installation.

The inverter by the signals of the control device 10 generates an alternating voltage of low frequency at the terminals of the overhead lines, under the action of which an alternating current flows through the wires of the line, the effective value of which is set and maintained at the required level by changing the output voltage of the converter 1 by affecting the value of the high-frequency pulse-width modulation coefficient (PWM). The frequency of the output voltage of the inverter 7 is chosen such that the inductive resistance of the line wires does not practically affect the effective value of the current flowing through them. When this condition is met, controlled ice melting using the proposed installation is possible on lines of the same length as in direct current melting.

In the reactive power compensation mode, the contacts of the three-pole switches 5 and 8 are open, the contacts of the three-pole switch 9 are closed and the converters 1 and 7 are connected in parallel. When setting the angle of control of the semiconductor switches of the converters α, slightly less than 180 °, a small active power is consumed from the AC network to maintain the voltage at the terminals of the capacitor bank 6. In this case, the alternating three-phase voltages Un, the first harmonic of which is shifted with respect to to the phase voltages of the AC source at an angle β = 180 ° -α. If the amplitudes of the first harmonic of the voltages U _P exceed the amplitude of the alternating voltage of the alternating current source, the converters generate reactive power in the network, if on the contrary, the converters load the network with reactive power. By changing the coefficient of the high-frequency PWM, the amplitude of the first harmonic of the voltages U _{P is} regulated, and, therefore, the magnitude and direction of the transmission of reactive power through the converters.

In the proposed combined device for melting ice and reactive power compensation, there is no need to use additional switching equipment and line switching in the process of melting ice, since these functions are performed by contactless semiconductor switches of an autonomous inverter. During the period of the output voltage at its output, the overhead wires are connected twice according to the “wire-two wires” scheme with their necessary permutations, similar to permutations during smelting of ice with direct current. In addition, the melting time is significantly reduced, since it occurs simultaneously on all OHL wires.

Claims (1)

Combined installation for melting ice and reactive power compensation, containing the first three-phase bridge converter on fully controllable semiconductor valves, shunted with on-board diodes, a capacitor bank on the DC side, the first three-pole switch and two three-phase inductors connected in series, the second three-pole connected in parallel to one of them switch - on the AC side, characterized in that a second three-phase bridge is inserted into it a howling converter on fully controllable semiconductor valves, shunted with on-board diodes, the DC terminals of which are connected to the DC terminals of the first converter, and the three-phase terminals are connected through the third three-pole switch to the wires of the power line for melting ice with alternating current of low frequency and through the fourth three-pole switch connected to the three-phase terminals of the first converter.