DD143987A5 - ARRANGEMENT FOR ELECTRONIC SWITCHING OF POWER CONDENSERS, FILTERS, SUCTION CIRCLES - Google Patents

Description

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Arrangement for the electronic switching of power capacitors, filter, absorption circuits. ·

Field of application of the invention

The invention has an arrangement for the electronic switching of power capacitors, filter, suction circuits that can be connected to a AC or three-phase network, the subject. ·. ''

Characteristics of the known technical solution

To compensate for the reactive power consumption in industrial networks, it is known to provide capacitor systems with Thyristorschaltgliedern (see K. Heumann, Basics of power * electronics, Verlag B. G. Teubner, Stuttgart, 1975, pages 184 to 188).

While a fixed capacitor battery delivers a constant capacitive reactive power and is therefore only suitable for plants with almost constant reactive power consumption, one can compensate for symmetrical and unbalanced load fluctuations with a capacitor battery in which parts of the battery with suitable switching devices on and off. , ,

From the ASEA magazine 1971, 6, pages 140 to 144 are Ko ndensatoranlagen with Thyristorschaltgliedern for reactive power :; compensation in which antiparallel-connected thyristors are connected in series with a capacitor and a choke coil to each phase of the network to be compensated.

are switched (Figure 1). The capacitor C is switched to the mains when the mains voltage is equal to the capacitor voltage. The current is alternately taken over by one of the two antiparallel-connected thyristors Tl or T2. In this known arrangement, the capacitors must be connected in series to avoid resonances occurring in the system harmonics inductors in series, which can also be designed if necessary so that the system can also serve as a harmonic filter. These inductors are absolutely necessary, since shock-compensation systems with thyristor-controlled power capacitors have significantly higher technical risks than the systems operating according to the indirect compensation method. To control malfunction cases special compensation measures are required in addition to increased control effort in this type of compensation. However, the total power to be installed in the individual plant components is less than half the power required for indirect compensation due to the typical consumer load cycles and the direct compensation.

However, special protection measures are required for incident cases:

In case of a defective compensation capacitor, no short-circuit current limiting takes place unless a special choke coil is provided for limiting. Similarly, switching operations in the network or the parallel connection of capacitor groups for compensation triggers transient and compensation processes, which are to be limited by special measures. For transient, short circuit and vibration discharge operations, a choke coil must therefore be provided as a special protective measure, the type rating of which must be rated at about 6 % of the installed compensation capacitor power.

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The aim of the invention is to balance by means of a capacitor bank and an electronic switch for switching on and off of parts of the capacitor bank symmetrical and unbalanced load fluctuations

Switching of capacitors occurring transient, short circuit and vibration discharge processes can be controlled with simple means without increased control effort and special protective measures.

Explanation of the essence of the invention

Object of the present invention is to provide an arrangement for switching on and off of AC power capacitors and / or filter or absorption circuits, in which a sufficient protection against transient, short circuit and vibration discharge processes is ensured and at the same time the choice and design of pure capacity and particularly to be provided, matched filter and Saugkreisdrosseln regardless of the protective measures mentioned can be done exclusively for special auszufilternde, higher frequencies.

The connected to the AC or three-phase AC power capacitors and / or filter or absorption circuits are switched on and off via a thyristor converter in three-phase or single-phase bridge circuit. In the DC branch of the thyristor power converter, a DC reactor is arranged, while the AC power capacitors and / or filter or absorption circuits are connected directly between the thyristor converter and the AC or three-phase network.

With this arrangement, decoupling of the choke coil effective for transient, short circuit and vibration discharge operations from the AC-side choke coils is effected. This makes it possible to switch pure capacitances and tuned filter or vacuum circuits of higher frequencies (250, 350, 550, 650 Hz, ...).

Execution example

On the basis of exemplary embodiments illustrated in the figures of the invention, the idea underlying the invention will now be explained in more detail. Show it

Figures 2 and 3 a capacitor switch in three-phase bridge circuit and

Figure 4 to 7 a capacitor switch in single-phase bridge circuit.

The capacitor switch shown in Figure 2 in three-phase bridge circuit consists of a connected to the three-phase network U, V, W pure power capacitor battery C and a thyristor switch S. Three-phase are no chokes required because the switch-on and short-circuit current limit of a DC choke coil Ld in. DC branch of the thyristor bridge circuit S is taken ·

In this arrangement, a filter circuit F is arranged between the thyristor S and the three-phase system U, V, W, in the series-connected three-phase reactors and capacitors, to certain, freely selectable frequencies (eg the 5th and 7th harmonic) are tuned. The choice of the three-phase side arranged Filterkreisdrosselspulen can be done free of necessary protective measures, since the necessary to limit equalizing currents choke coil is arranged as a DC choke coil Ld in the DC branch of the thyristor S. Due to the separate tuning of the filter circuits to the harmonics occurring in the system and the choke on the limitation of the compensation currents can be a significant reduction of the reactor power to be installed for the required protective measures can be achieved.

Figures 4 to 6 show application examples of the invention for switching pure power capacitors in single-phase converter arrangements.

Figure 4 shows a fully controlled single-phase bridge switch S with DC-side inductor Ld, which is connected in parallel for the freewheeling diode D. As in the arrangements described above, the power capacitor C is arranged directly between the thyristor switch S and the alternating current system U., Mp.

Figures 5 and 6 show in a modified arrangement of semi-controlled electronic switches S ₅ wherein once the thyristors and diodes are arranged separately in two branches of the bridge circuit, on the other respectively in series in ö.en two branches of the bridge circuit.

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FIG. 7 shows, analogously to FIG. 2, a single-phase arrangement for controlling matched filter circuits F by means of a fully controlled thyristor switch S, to whose DC terminals the DC choke coil Ld required to limit equalizing currents is connected. Again, the filter circuit elements are dimensioned independently of the required protective measures and can be freely tuned to specific frequencies.

Claims (3)

invention claim 1. Arrangement for the electronic switching of power capacitors, filter, absorption circuits, which can be connected to a three-phase AC or AC network, characterized in that in that a DC choke coil (Ld) is arranged in the DC branch and that the AC power capacitors (C) and / or filter circuits (S) are arranged as electronic switches in a three-phase or single-phase bridge circuit. F) are connected directly between the thyristor power converter (S) and the AC or three-phase network (U, V, W or U, Mp). 2; Arrangement according to item 1,
characterized by,. that the thyristor power converter (S) consists of a fully controlled power converter in three-phase or single-phase bridge circuit. 3 «Order under point 1,
characterized by that the thyristor power converter consists of a half-controlled thyristor diode converter in three-phase or single-phase bridge circuit. For this 1 string drawings