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Brown, Boveri & Cie Ag

Kadry Sadek

Marcos Pereira

Michael Hausler

Norbert Christl

Walter Pfyl

Herbert Stemmler

Manfred Weibelzahl

Peter Dahler

Frank Schettler

Georg Wild

John J Vithayathil

Gerhard Linhofer

Josip Dobsa

Gerhard Guth

Wilfried Breuer

Philippe Huber

Peter Lutzelberger

Peter Mauchle

Walter Kuhn

Peter Neidhart

Marcos-Antonio Cavalcanti Pereira

Karl Ücker

Karl Uecker

In order to provide an apparatus () for flexible power transmission and for deicing of a high-voltage line, which has a plurality of phases, by means of direct current, with an AC voltage connection of the high-voltage line which has a number of phases corresponding to the phases of the high-voltage line, each phase having at least one inductance () and a valve circuit () connected in series with each inductance (), with the valve circuit () being connected by means of a junction point () to the AC voltage connection, and having a first current path () with a first power semiconductor valve () and a second current path () with a second power semiconductor valve (), with the power semiconductor valves () being connected in opposite senses with respect to one another with reference to the junction point () and in which case the first and the second current path () can be connected to a TCR star point by means of at least one star point switch (), whose design is simple and at the same time costs little, it is proposed that the TCR star point () is connected via a connecting line to a star point of a zero phase-sequence system suppression means ().

Device for flexible power transmission and deicing of a high-voltage power line by means of direct current

A device for transmitting electric power between alternating voltage networks includes converters interconnected by direct current lines and provided each with several six-pulse conversion bridges. The six-pulse conversion bridges of one same converter are capable of being connected to an alternating voltage network associated with the converters via inductances differently phase-shifted. A control unit is provided to energize the valves of the six-pulse conversion bridges. The device is more economical and the converters are interconnected by a plurality of direct current circuits, each direct current circuit being galvanically separated from at least an alternating voltage network.

Twelve-pulse HVDC transmission

A device (), for adjusting the impedance of a high voltage line (), supplying an alternating current, has at least one control coil (), which may be inserted in series in the high voltage line () and at least one switching device (), provided for each control coil (). The device is compact and economical. A control unit () for controlling each switching device () is also provided, such that the reactance of the control coil (), acting in the device may be adjusted by the switching of the switching device (), whereby each switching device () is arranged parallel to the corresponding control coil () in a parallel branch ().

Device for adjusting the impedance of a high voltage line supplying an alternating current

The novel circuit arrangement is used for the static generation of a variable electric output, as is common in static reactive-power compensation systems. According to the invention, a voltage is applied to a consumer, i.e. to a capacitor and/or an inductor, and a transformer (T) has at least two power-control windings (WW) in a secondary circuit, said windings being connected electrically in series via bridge circuits (BB). In their branches, the bridge circuits contain static switches (BSS) in an inverse-parallel connection, said switches can be selectively connected or disconnected.

Circuit arrangement for the static generation of a variable electric output

The invention relates to a hybrid for an AC mains system, with the hybrid filter having a passive and an active filter which are electrically connected in series, and with the active filter having a voltage source. According to the invention, a tuned filter, which is tuned to the rated frequency of the AC mains system, is electrically connected in parallel with the active filter. This results in a hybrid filter for an AC mains system, whose active filter is not loaded by the fundamental current component.

Hybrid filter for an alternating current network

A thyristor-controlled capacitor bank includes a thyristor switch and a capacitor bank. The capacitor bank is split into at least two series-connected capacitor groups. A series circuit including a thyristor switch and an inductor coil is connected in parallel with the capacitor group which is remote from a capacitor group at a mains power supply connection. A thyristor-switched capacitor bank is thus obtained which has a thyristor switch that therefore only needs to be constructed for a fraction of the mains power supply voltage itself, which is a major advantage for economic reasons.

Thyristor-switched capacitor bank

Method and apparatus for determining orders of non-characteristic

Where different 3-phase systems are connected to each other via two static converters having an intermediate direct-current circuit, the exchange of power via the intermediate direct-current circuit can be interrupted by a severe disturbance, for example by failure of a static-converter or by line or busbar faults causing a short-circuiting of one of the static converters. This interruption means a change in the balance of effective power and, associated with this, a shedding of reactive load for the other undisturbed 3-phase system. To reduce high dynamic overvoltages which can lead to plant components being endangered or to operational disturbances, the firing angle of the static converter remaining in operation is regulated with dependence on the alternating voltage of the alternating-current system connected to this static converter, in such a manner that the overvoltage is reduced. This is carried out by regulating the current. The firing angle can be adjusted simultaneously with the short circuiting of the intermediate direct-current circuit by means of a short circuit device.

Method for reducing dynamic overvoltages in an alternating-current

If in a high-voltage d-c transmission system (HVDCTS), a resonance frequency of an a-c voltage network (NB) connected to the inverter (1B) is located in the vicinity of a voltage component contained in the a-c voltage network, a resonance frequency which often cannot be compensated by a current regulator controlling the rectifier stage (1A) is coupled into the d-c circuit of the HVDCTS via the inverter. Therefore, resonance phenomena which requires an emergency shutdown of the HVDCTS are generated. Therefore, a pilot quantity (U'.sub.d) is formed with a defined phase shift relative to the resonance oscillation of the HVDCTS voltage and added to the output of the current regulator. Thereby, a constant HVDCTS current can be generated for a given operating point and the resonance in the a-c voltage network (NB) can be damped. If the resonance oscillation is determined by two quantities (U'.sub.d, i'.sub.d) of, respectively, the HVDCTS voltage as well as of the HVDCTS current, stable damping of the resonance phenomena can be achieved by the pilot control described with the two quantities even for deviating operating points.

Method and apparatus for suppressing resonance phenomena in the A-C

To reduce unwanted current oscillations such as, for example, of the second harmonic of the system frequency (f.sub.o), the firing angles (.alpha.1, .alpha.2) of a link-circuit rectifier (1) and of a link-circuit inverter (2) are compensatingly acted on in push-pull mode. For this purpose, a direct-current link-circuit current signal (S5, S5'), which contains the instability or the current oscillation to be compensated, is fed by means of a current detector (5, 5') to a bandpass filter (16, 16', 16') which is tuned to the frequency (f.sub.o, f.sub.x) of the respective current oscillation. The phase of a bandpass filter output signal (S16) is shifted by 90.degree. trailing in a 90.degree. phase-shifting section (15, 15', 15'). A compensating signal (S15,S15', S15') obtained in this manner is fed to first and second function generators (13, 13', 13'; 14, 14', 14'). The first function generators allow the positive component (S13) to pass and the second function generators allow the negative component (S14) of the compensating signal to pass. The output signal of the first function generator passes via a switch (12') to a summing section (11') for forming the cosine of the firing angle (.alpha.2) of the link-circuit inverter (2). The output signal of the second function generator passes via a switch (12) to a summing section (11) for forming the cosine of the firing angle (.alpha.1) of the link-circuit rectifier (1). By these means, the firing angle (.alpha.2) of the link-circuit inverter (2) is reduced when the direct-current link-circuit current signal is dropping and the firing angle (.alpha.1) of the link-circuit rectifier (1) is increased when it is rising.

Method and compensating device for compensating current oscillations

In this three-phase filter circuit system for static converter systems and particularly high-voltage direct-current short ties, at least two high-pass filters are provided which are connected in parallel. Each high-pass filter consists of a choke connected in parallel with a resistance and, in series with both, a capacitor and can be individually connected to the three-phase busbar via a switch. The filter circuits are used not only for reducing harmonics but also as compensating devices, which can be switched in steps, for the reactive power requirement of the static converters so that in the lower partial load range of the system one of the filter circuits is disconnected for reasons of reactive power balance. In order to improve the filtering effect in this lower partial load range, a bus-coupler switch connecting in each case the common junctions of capacitor, resistance and choke of the high-pass filters is closed. When the switch is closed, this widens the band width of the filter circuit which is in operation and increases the resonance frequency, and individual distortions, the total distortion and telephone interference factors on the busbar are reduced.

Alternating-current filter circuit arrangement

In a reactive power compensator used for capacitive or inductive reactive powers in alternating-voltage networks, a capacitor is connected to an alternating-voltage network for a short time by means of a thyristor switch. In order to reduce the voltage load on the thyristor switch, a discharge circuit is connected in parallel with the capacitor. Via this circuit, the capacitor can discharge, after being disconnected from the alternating-voltage network, with such a speed that the voltage occurring at the thyristor switch is no greater than about 1.5 times the maximum network voltage. In the discharge circuit, a variable inductive reactive resistance can be a discharge circuit choke having an iron core or the primary winding of a transformer. When the capacitor is connected to the alternating-voltage network, the discharge circuit choke is unsaturated and its reactive resistnace is large (or the transformer secondary is open) so that no significant leakage current can flow via the discharge circuit. After the capacitor is disconnected from the alternating-voltage network, the discharge circuit choke is saturated and its reactive resistance is small (or the transformer secondary is shortcircuited) so that a large discharge current can flow. No switching element is required in the discharge circuit. In order to limit the rectifier current of the thyristor switch and to change this rectifier current with time, an air choke is provided. The maximum rectifier voltage is limited by surge dissipators of zinc oxide.

Reactive power compensator with capacitor and capacitor discharge circuit

A compensation circuit for reactive power balance includes a capacitor, inductor and rectifier connected in series to a power system. In order to protect the rectifier from misfires of the thyristors, two discharge devices are connected in parallel to the series circuit from the common points in the series circuit. This protects the thyristors in case of a double misfire.

Circuit arrangement for the compensation of reactive power in an

Method of taking a pole of high-voltage d-c transmission system (HVDCTS) out of service, having a rectifier station connected to a first three-phase network and an inverter station connected to a second three-phase network, two d-c lines connected from one station to the other, each station being divided into halves, the station halves of each station being connected together on one side to a station center grounding electrode, the other side of each station being connectible to the positive d-c line so as to form a positive pole, and to the negative d-c line so as to form a negative pole, and residual-current switching means for taking a pole out of service, which includes grounding the station pole through a pole grounding switch which is spaced from the station center grounding electrode, and subsequently commutating a partial fault current of other poles, occurring from the pole being taken out of service, into the station center grounding electrode by the residual-current switch in the form of a circuit breaker.

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Erlangen, Germany

Kadry Sadek