EP0081752A2 - Device for maintaining the voltage of a single or multiphase AC supply mains submitted to changing loads at a constant level - Google Patents

Device for maintaining the voltage of a single or multiphase AC supply mains submitted to changing loads at a constant level Download PDF

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Publication number
EP0081752A2
EP0081752A2 EP82111132A EP82111132A EP0081752A2 EP 0081752 A2 EP0081752 A2 EP 0081752A2 EP 82111132 A EP82111132 A EP 82111132A EP 82111132 A EP82111132 A EP 82111132A EP 0081752 A2 EP0081752 A2 EP 0081752A2
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Prior art keywords
voltage
time area
integrator
reactance
line
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EP82111132A
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German (de)
French (fr)
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EP0081752A3 (en
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Eberhard Dipl.-Ing. Schmid
Robert Brehler
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Siemens AG
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Siemens AG
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/12—Regulating voltage or current wherein the variable actually regulated by the final control device is ac
    • G05F1/40—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices
    • G05F1/44—Regulating voltage or current wherein the variable actually regulated by the final control device is ac using discharge tubes or semiconductor devices as final control devices semiconductor devices only

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  • the invention relates to a device for keeping the voltage constant between two conductors of a single-phase or multi-phase alternating current network subject to load fluctuations, with a series connection of a choke coil and an alternating current regulator connected to the two conductors each having a phase, the antiparallel-connected controllable valves of which are supplied with ignition pulses are derived from the deviation between a predetermined target value and a size of the voltage time area formed from the mains voltage by means of an integrator via at least one limit value detector.
  • a device of this type for use in, for example, arc melting furnaces or converter drives of networks supplying rolling mills is known from European patent application 26 260.
  • the consumers mentioned are subject to considerable load fluctuations and therefore cause voltage fluctuations in the supply network, which, for example as flicker phenomena, affect the brightness of incandescent lamps which are also connected to the supply network.
  • the purpose of the device is to keep the voltage of the supply network as constant as possible, but at least to suppress the voltage fluctuations to such an extent that they are no longer perceived as disturbing. For this, the voltage to be kept constant measured and the voltage time area determined during every half oscillation period of the mains voltage by means of an integrator.
  • the valve of the AC converter which is polarized in accordance with the sign of the half-oscillation, is ignited by a limit detector with a downstream pulse former, so that the two conductors of the network are conductively connected to one another via the choke connected upstream of the AC power controller.
  • the short-circuit current flowing through the actuator is limited by the choke coil.
  • the voltage remaining at the throttle after the ignition of the valve leads to a voltage time area for the mains voltage which is larger than the voltage time area corresponding to the predetermined desired value.
  • the error area caused thereby can be compensated for by an output signal of an additional integrator with an adjustable time constant, which integrates a measured variable corresponding to the short-circuit current in the series connection of choke and actuator.
  • the impedance of the series circuit which acts as a stabilizer and consists of a choke coil and an AC power controller should be zero.
  • a small inductance of the choke coil has the disadvantage ; with the fact that the harmonics generated by the actuator are large. This requires an increased effort in filter circuits.
  • the object of the invention is to determine the voltage time area including the error area caused by the choke in advance during each half-oscillation of the mains voltage and to take this into account for the command to ignite the actuator.
  • this object is achieved in that the actual value of the voltage time area of the mains voltage is the sum of the size formed by the integrator and a residual size of the voltage time area continuously determined in a computing circuit and dependent on the reactance of the series circuit.
  • a result comparable to the state of the art with regard to keeping the mains voltage constant can be achieved with significantly higher stabilizer impedances (i.e. generation of lower harmonics) or, with constant stabilizer impedances, significantly better results can be achieved with regard to keeping the mains voltage constant.
  • the conductor 1 shows two conductors 1, 2 of a single-phase or multi-phase network for supplying a load 4 which is subject to strong load fluctuations, for example an arc melting furnace.
  • the conductor 2 carries ground potential.
  • the load fluctuations in the supply network have the effect of voltage fluctuations, from which other consumers 5, in particular incandescent lamps, whose brightness fluctuations in the range between 3 and 10 Hz are perceived as particularly disturbing by the human eye, are protected should.
  • the two conductors, or in the multiphase network two conductors each are connected to one another via a series connection (stabilizer) comprising an alternating current controller 6 and a choke coil 9, comprising thyristors 7, 8 connected in parallel.
  • stabilizer stabilizer
  • the ignition pulses for the thyristors are supplied by a control device 10 which is connected to a measuring element 11 which detects the mains voltage u N and, as described in more detail in connection with FIG. 4, contains, inter alia, an integrator, limit indicator and pulse shaper. To suppress harmonics, filters consisting of coils 12 and capacitors 13 are provided.
  • the choke coil 9 limits the short-circuit current flowing through the alternating current controller 6 and its reactance X s forms, together with the reactance 3 of the network, designated X N , a voltage divider when the alternating current controller is conductive by ignition of one of the thyristors.
  • the line voltage uN corresponds to the voltage u o at all times if the load current is simply neglected (FIG. 2). If, on the other hand, the actuator is conductive, the voltage u 0 is divided , neglecting the impedance of the consumers 4 and 5, in accordance with the voltage divider ratio. So it is:
  • the profile of the mains voltage u N between 0 and + t w and between t x and t ⁇ is determined by the voltage u D at the choke 9, shown in broken lines.
  • the closely hatched portion b of the voltage time area still occurs as a result of the current i s flowing through the inductor.
  • the total voltage time area of the network Voltage is the sum of the hatched part a and the part b.
  • the time course of the measured part a (t), the calculated part b (t) and the voltage time area f composed thereof during a half-oscillation of the mains voltage is shown in FIG. 3.
  • the integrator in the control device has only the portion if the AC power controller is fired at time t X dt recorded.
  • U is N is the peak value
  • ⁇ is the angular frequency of the mains voltage U N.
  • the actual value ⁇ of the voltage time area obtained in this way is compared with a target value ⁇ *. If the deviation between these two values is zero, the actuator is ignited (ignition point t x ). After ignition (t x ) of the actuator, the voltage time area of the mains voltage is smaller than the voltage time area of the voltage u o by the triangle c between the solid and dash-dotted lines. The resulting total voltage time area of the mains voltage u N is equal to the setpoint
  • FIG. 4 shows, as an exemplary embodiment, the structure of an analog control device 10 to be used in the device according to FIG. 1, to which the mains voltage u N detected by the measuring element 11 is supplied as an input variable.
  • the measurement signal is first rectified in an absolute value generator 14 and at the same time broken down into a sine and a cosine component in a vector identifier 15.
  • the variable a (t) XU N dt is formed in an integrator 16 from the measurement signal rectified in the magnitude generator.
  • a zeroing pulse derived from the normalized sine component of the measurement signal via a limit indicator 17 and a time stage 18 resets the integrator at the end of each half-oscillation at the time t ⁇ -T / 2 by actuating a switch 19 and releases it again.
  • a constant with the value 1 is added to the normalized cosine component of the vector identifier and the sum in a multiplier 21 with the constant factor that can be set on a potentiometer 22 multiplied.
  • the product is the quantity b (t) which is fed to a summing element 23 in which the sum of the quantities representing the actual value of the voltage time area a (t) and b (t) are compared with a target value ⁇ *.
  • the integral of any other function of u N can, for example dt be formed.
  • y should be an integer so that the implementation remains simple.
  • control device Since the mode of operation of the control device is based on mathematical operations, digital arithmetic circuits or microprocessors can also be used instead of an analog arithmetic circuit.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Control Of Electrical Variables (AREA)
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Abstract

Zur Konstanthaltung der Spannung eines Netzes, das beispielsweise einen Lichtbogenschmelzofen speist, ist zwischen je zwei Leiter des Netzes eine Reihenschaltung aus einem Wechselstromsteller (6) und einer Drosselspule (9) geschaltet. Die steuerbaren Ventile (7, 8) werden in Abhängigkeit von dem Vergleich der Spannungszeitfläche, die mittels eines Integrators während jeder Halbschwingung aus der Netzspannung ermittelt wird, mit einem vorgegebenen Sollwert vorzeichenrichtig gezündet. Danach dem Zündzeitpunkt des Wechselstromstellers noch ein auf die Reaktanz der Drosselspule zurückzuführender Anteil der Spannungszeitfläche wirksam ist, wird dieserAnteil berechnet und zu dem vom Integrator ermittelten Anteil vor dem Vergleich mit dem Sollwert addiert.To keep the voltage of a network constant, which feeds an arc melting furnace, for example, a series circuit consisting of an alternating current controller (6) and a choke coil (9) is connected between two conductors of the network. The controllable valves (7, 8) are ignited with the correct sign depending on the comparison of the voltage-time area, which is determined from the mains voltage by means of an integrator during each half-oscillation, with a predetermined setpoint value. After a portion of the voltage-time area due to the reactance of the choke coil is still active at the time of ignition of the AC power controller, this portion is calculated and added to the portion determined by the integrator before the comparison with the setpoint value.

Description

Die Erfindung betrifft eine Vorrichtung zur Konstanthaltung der Spannung zwischen je zwei Leitern eines Lastschwankungen unterworfenen, ein- oder mehrphasigen Wechselstromnetzes mitteils einer an die beiden Leiter je einer Phase angeschlossenen Reihenschaltung aus einer Drosselspule und einem Wechselstromsteller, dessen antiparallel geschalteten steuerbaren Ventilen Zündimpulse zugeführt sind, die aus der Abweichung zwischen einem vorgegebenen Sollwert und einer aus der Netzspannung mittels eines Integrators gebildeten Größe der Spannungszeitfläche über mindestens einen Grenzwertmelder abgeleitet sind.The invention relates to a device for keeping the voltage constant between two conductors of a single-phase or multi-phase alternating current network subject to load fluctuations, with a series connection of a choke coil and an alternating current regulator connected to the two conductors each having a phase, the antiparallel-connected controllable valves of which are supplied with ignition pulses are derived from the deviation between a predetermined target value and a size of the voltage time area formed from the mains voltage by means of an integrator via at least one limit value detector.

Eine Vorrichtung dieser Art für den Einsatz in beispielsweiseLichtbogenschmelzöfen oder Stromrichterantriebe von Walzwerken speisenden Netzen ist aus der europäischen Patentanmeldung 26 260 bekannt. Die genannten Verbraucher sind erheblichen Lastschwankungen unterworfen und rufen daher Spannungsschwankungen im Versorgungsnetz hervor, die sich beispielsweise als sogenannte Flickererscheinungen auf die Helligkeit von ebenfalls an das Versorgungsnetz angeschlossenen Glühlampen auswirken. Sinn und Zweck der Vorrichtung ist es, die Spannung des Versorgungsnetzes möglichst konstant zu halten, zumindest aber die Spannungsschwankungen soweit zu unterdrücken, daß sie nicht mehr als störend empfunden werden. Hierzu wird die konstant zu haltende Spannung gemessen und während jeder halben Schwingungsperiode der Netzspannung mittels eines Integrators die Spannungszeitfläche ermittelt. Erreicht die Spannungszeitfläche der halben Periode einen vorgegebenen Sollwert, der beispielsweise dem Mittel- oder Effektivwert der Spannungszeitfläche der Halbschwingung entspricht, so wird über einen Grenzwertmelder mit nachgeschaltetem Impulsformer das dem Vorzeichen der Halbschwingung entsprechend gepolte Ventil des Wechselstromstellers gezündet, so daß die beiden Leiter des Netzes über die dem Wechselstromsteller vorgeschaltete Drossel leitend miteinander verbunden sind. Durch die Drosselspule wird der über den Steller fließende Kurzschlußstrom begrenzt. Die an der Drossel nach der Zündung des Ventils verbleibende Spannung führt für die Netzspannung zu einer Spannungszeitfläche, die größer als die dem vorgegebenen Sollwert entsprechende Spannungszeitfläche ist. Die dadurch verursachte Fehlerfläche kann durch ein dem Integrator zusätzlich zugeführtes Ausgangssignal eines weiteren Integrators mit einstellbarer Zeitkonstante ausgeglichen werden, der eine dem Kurzschlußstrom in der Reihenschaltung aus Drossel und Steller entsprechende Meßgröße integriert.A device of this type for use in, for example, arc melting furnaces or converter drives of networks supplying rolling mills is known from European patent application 26 260. The consumers mentioned are subject to considerable load fluctuations and therefore cause voltage fluctuations in the supply network, which, for example as flicker phenomena, affect the brightness of incandescent lamps which are also connected to the supply network. The purpose of the device is to keep the voltage of the supply network as constant as possible, but at least to suppress the voltage fluctuations to such an extent that they are no longer perceived as disturbing. For this, the voltage to be kept constant measured and the voltage time area determined during every half oscillation period of the mains voltage by means of an integrator. If the voltage time area of half the period reaches a predetermined target value, which corresponds, for example, to the mean or effective value of the voltage time area of the half-oscillation, then the valve of the AC converter, which is polarized in accordance with the sign of the half-oscillation, is ignited by a limit detector with a downstream pulse former, so that the two conductors of the network are conductively connected to one another via the choke connected upstream of the AC power controller. The short-circuit current flowing through the actuator is limited by the choke coil. The voltage remaining at the throttle after the ignition of the valve leads to a voltage time area for the mains voltage which is larger than the voltage time area corresponding to the predetermined desired value. The error area caused thereby can be compensated for by an output signal of an additional integrator with an adjustable time constant, which integrates a measured variable corresponding to the short-circuit current in the series connection of choke and actuator.

Zur Konstanthaltung der Spannungszeitfläche der Netzspannung müßte die Impedanz der als Stabilisator wirkenden Reihenschaltung aus Drosselspule und Wechselstromsteller Null sein. Eine kleine Induktivität der Dosselspule bringt jedoch den Nachteil;mit sich, daß die vom Steller erzeugten Oberschwingungen groß sind. Das bedingt einen erhöhten Aufwand an Filterkreisen.In order to keep the voltage time area of the mains voltage constant, the impedance of the series circuit which acts as a stabilizer and consists of a choke coil and an AC power controller should be zero. A small inductance of the choke coil has the disadvantage ; with the fact that the harmonics generated by the actuator are large. This requires an increased effort in filter circuits.

Hiervon ausgehend liegt der Erfindung die Aufgabe zugrunde, während jeder Halbschwingung der Netzspannung deren Spannungszeitfläche einschließlich der durch die Drossel bedingten Fehlerfläche im voraus zu bestimmen und für den Befehl zur Zündung des Stellers zu berücksichtigen. Gemäß der Erfindung wird diese Aufgabe dadurch gelöst, daß der Istwert der Spannungszeitfläche der Netzspannung die Summe aus der vom Integrator gebildeten Größe und einer in einer Rechenschaltung laufend ermittelten, von der Reaktanz der Reihenschaltung abhängigen Restgröße der Spannungszeitfläche ist.Proceeding from this, the object of the invention is to determine the voltage time area including the error area caused by the choke in advance during each half-oscillation of the mains voltage and to take this into account for the command to ignite the actuator. According to the invention, this object is achieved in that the actual value of the voltage time area of the mains voltage is the sum of the size formed by the integrator and a residual size of the voltage time area continuously determined in a computing circuit and dependent on the reactance of the series circuit.

Ein mit dem Stand der Technik vergleichbar gutes Ergebnis bezüglich der Konstanthaltung der Netzspannung kann mit wesentlich größeren Stabilisatorimpedanzen erreicht werden (d.h. Erzeugung kleinerer Oberschwingungen) oder bei gleichbleibenden Stabilisatorimpedanzen können wesentlich bessere Ergebnisse bezüglich der Konstanthaltung der Netzspannung erreicht werden.A result comparable to the state of the art with regard to keeping the mains voltage constant can be achieved with significantly higher stabilizer impedances (i.e. generation of lower harmonics) or, with constant stabilizer impedances, significantly better results can be achieved with regard to keeping the mains voltage constant.

An Hand der in der.Zeichnung dargestellten Figuren wird die Erfindung im folgenden näher erläutert. Es zeigen:

  • Fig. 1 den prinzipiellen Aufbau der Vorrichtung,
  • Fig. 2 den Verlauf der Netzspannung, der Spannung an der Drossel und des Stromes im Stabilisator während einer halben Periode der Netzspannung,
  • Fig. 3 die Spannungszeitfläche und ihre Zusammensetzung aus zwei Komponenten in Abhängigkeit von der Zeit,
  • Fig. 4 ein Ausführungsbeispiel einer erfindungsgemäßen Steuereinrichtung.
The invention is explained in more detail below with the aid of the figures shown in the drawing. Show it:
  • 1 shows the basic structure of the device,
  • 2 shows the profile of the mains voltage, the voltage across the choke and the current in the stabilizer during half a period of the mains voltage,
  • 3 shows the voltage time area and its composition from two components as a function of time,
  • Fig. 4 shows an embodiment of a control device according to the invention.

In Fig. 1 sind zwei Leiter 1, 2 eines ein- oder mehrphasigen Netzes zur Versorgung eines starken Lastschwankungen unterworfenen Verbrauchers 4, z.B. eines Lichtbogenschmelzofens, dargestellt. In einem einphasigen Netz führt der Leiter 2 Massepotential. Die Lastschwankungen wirken sich im Versorgungsnetz als Spannungsschwankungen aus, vor denen andere Verbraucher 5, insbesondere Glühlampen, deren Helligkeitsschwankungen im Bereich zwischen 3 und 10 Hz vom menschlichen Auge als besonders störend empfunden werden, geschützt werden sollen. Zu diesem Zweck sind die beiden Leiter, bzw. im mehrphasigen Netz je zwei Leiter über eine Reihenschaltung (Stabilisator) aus einem antiparallel geschaltete Thyristoren 7, 8 enthaltenden Wechselstromsteller 6 und einer Drosselspule 9 miteinander verbunden. Die Zündimpulse für die Thyristoren liefert eine Steuereinrichtung 10, die an einem die Netzspannung uN erfassenden Meßglied 11 angeschlossen ist und - wie im Zusammenhang mit Fig. 4 näher beschrieben - unter anderem einen Integrator, Grenzwertmelder und Impulsformer enthält. Zur Unterdrückung von Oberschwingungen sind aus Spulen 12 und Kondensatoren 13 bestehende Filter vorgesehen. Die Drosselspule 9 begrenzt den über den Wechselstromsteller 6 fließenden Kurzschlußstrom und ihre Reaktanz Xs bildet zusammen mit der mit XN bezeichneten Reaktanz 3 des Netzes einen Spannungsteiler, wenn der Wechselstromsteller durch Zündung eines der Thyristoren leitend ist.1 shows two conductors 1, 2 of a single-phase or multi-phase network for supplying a load 4 which is subject to strong load fluctuations, for example an arc melting furnace. In a single-phase network, the conductor 2 carries ground potential. The load fluctuations in the supply network have the effect of voltage fluctuations, from which other consumers 5, in particular incandescent lamps, whose brightness fluctuations in the range between 3 and 10 Hz are perceived as particularly disturbing by the human eye, are protected should. For this purpose, the two conductors, or in the multiphase network two conductors each, are connected to one another via a series connection (stabilizer) comprising an alternating current controller 6 and a choke coil 9, comprising thyristors 7, 8 connected in parallel. The ignition pulses for the thyristors are supplied by a control device 10 which is connected to a measuring element 11 which detects the mains voltage u N and, as described in more detail in connection with FIG. 4, contains, inter alia, an integrator, limit indicator and pulse shaper. To suppress harmonics, filters consisting of coils 12 and capacitors 13 are provided. The choke coil 9 limits the short-circuit current flowing through the alternating current controller 6 and its reactance X s forms, together with the reactance 3 of the network, designated X N , a voltage divider when the alternating current controller is conductive by ignition of one of the thyristors.

Ist der Wechselstromsteller nicht leitend, dann entspricht die Netzspannung uN in jedem Augenblick der Spannung uo, wenn der Laststrom vereinfachend vernachlässigt wird (Fig. 2). Ist der Steller dagegen leitend, so teilt sich die Spannung u0 unter Vernachlässigung der Impedanz der Verbraucher 4 und 5 entsprechend dem Spannungsteilerverhältnis auf. Es ist dann also:

Figure imgb0001
If the AC power controller is not conductive, then the line voltage uN corresponds to the voltage u o at all times if the load current is simply neglected (FIG. 2). If, on the other hand, the actuator is conductive, the voltage u 0 is divided , neglecting the impedance of the consumers 4 and 5, in accordance with the voltage divider ratio. So it is:
Figure imgb0001

Der Verlauf der Netzspannung uN zwischen 0 und + tw und zwischen tx und tπ wird von der gestrichelt gezeichneten Spannung uD an der Drossel 9 bestimmt. Nach Zündung des Wechselstromstellers im Zeitpunkt tx fällt in Folge des durch die Drosselspule fließenden Stromes is noch der eng schraffierte Anteil b der Spannungszeitfläche an. Die gesamte Spannungszeitfläche der Netzspannung ist also die Summe aus dem weitschraffierten Teil a und dem Anteil b.The profile of the mains voltage u N between 0 and + t w and between t x and tπ is determined by the voltage u D at the choke 9, shown in broken lines. After ignition of the AC power controller at time t x , the closely hatched portion b of the voltage time area still occurs as a result of the current i s flowing through the inductor. The total voltage time area of the network Voltage is the sum of the hatched part a and the part b.

Der zeitliche Verlauf des gemessenen Teils a (t), des errechneten Anteils b(t) und der daraus zusammengesetzten Spannungszeitfläche f während einer Halbschwingung der Netzspannung ist in Fig. 3 dargestellt. Der Integrator in der Steuereinrichtung hat, wenn der Wechselstromsteller im Zeitpunkt tX gezündet wird, nur den Anteil

Figure imgb0002
dt erfaßt.The time course of the measured part a (t), the calculated part b (t) and the voltage time area f composed thereof during a half-oscillation of the mains voltage is shown in FIG. 3. The integrator in the control device has only the portion if the AC power controller is fired at time t X
Figure imgb0002
 dt recorded.

Der nach der Zündung des Wechselstromstellers für die Spannungszeitfläche noch wirksame Anteil b ergibt sich zu

Figure imgb0003
The portion b which is still effective after the ignition of the AC power controller for the voltage time area is given by
Figure imgb0003

Darin ist UN der Scheitelwert und ω die Kreisfrequenz der Netzspannung uN.U is N is the peak value, and ω is the angular frequency of the mains voltage U N.

Zur Steuerung der Netzspannung wird der auf diese Weise gewonnene Istwert Φ der Spannungszeitfläche mit einem Sollwert Φ* verglichen. Ist die Abweichung zwischen diesen beiden Werten Null, wird der Steller gezündet (Zündzeitpunkt tx). Nach der Zündung (tx) des Stellers ist die Spannungszeitfläche der Netzspannung um das zwischen der durchgezogenen und der strichpunktierten Linie liegende Dreieck c geringer als die Spannungszeitfläche der Spannung uo. Die sich ergebende Gesamt-Spannungszeitfläche der Netzspannung uN ist gleich dem SollwertTo control the mains voltage, the actual value Φ of the voltage time area obtained in this way is compared with a target value Φ *. If the deviation between these two values is zero, the actuator is ignited (ignition point t x ). After ignition (t x ) of the actuator, the voltage time area of the mains voltage is smaller than the voltage time area of the voltage u o by the triangle c between the solid and dash-dotted lines. The resulting total voltage time area of the mains voltage u N is equal to the setpoint

Für die Berechnung des Anteils b(t) an der Spannungszeitfläche ist vorausgesetzt, daß

  • 1.) der Scheitelwert UN der Netzspannung sich nicht wesentlich ändert,
  • 2.) die Netzspannung uN sich nach dem Zündzeitpunkt t nur sinusförmig ändert,
  • 3.) die Kreisfrequenz sich nicht ändert und
  • 4.) die Reaktanz XN und damit die Kurzschlußleistung des Netzes konstant bleibt.
For the calculation of the proportion b (t) in the voltage time area it is assumed that
  • 1.) the peak value U N of the mains voltage does not change significantly,
  • 2.) the mains voltage uN only changes sinusoidally after the ignition point t,
  • 3.) the angular frequency does not change and
  • 4.) the reactance X N and thus the short-circuit power of the network remains constant.

Obwohl diese Voraussetzungen in der Regel zutreffen, führen sie dazu, daß die Berechnung von b(t) nur eine Näherungsrechnung darstellt.Although these prerequisites generally apply, they mean that the calculation of b (t) is only an approximation.

Fig. 4 zeigt als Ausführungsbeispiel den Aufbau einer in der Vorrichtung nach Fig. 1 zu verwendenden, analog arbeitenden Steuereinrichtung 10, der als Eingangsgröße die von dem Meßglied 11 erfaßte Netzspannung uN zugeführt ist. Das Meßsignal wird zunächst in einem Betragsbildner 14 gleichgerichtet und gleichzeitig in einem Vektoridentifizierer 15 in einen Sinus-und einen Cosinusanteil zerlegt. Aus dem im Betragsbildner gleichgerichteten Meßsignal wird in einem Integrator 16 die Größe a(t) = X UN dt gebildet. Ein aus dem normierten Sinusanteil des Meßsignals über einen Grenzwertmelder 17 und eine Zeitstufe 18 abgeleiteter Nullsetzimpuls setzt den Integrator am Ende jeder Halbschwingung im Zeitpunkt t π - T/2 durch Betätigung eines Schalters 19 zurück und gibt ihn wieder frei. Zu dem normierten Cosinusanteil des Vektoridentifizierers wird im Summierpunkt 20 eine Konstante mit dem Wert 1 addiert und die Summe in einem Multiplizierer 21 mit dem konstanten, an einem Potentiometer 22 einstellbaren Faktor

Figure imgb0004
multipliziert. Das Produkt ist die Größe b(t), die einem Summierglied 23 zugeführt wird, in dem die den Istwert der Spannungszeitfläche darstellende Summe aus den Größen a(t) und b(t) mit einem Sollwert Φ* verglichen wird. Überschreitet der Istwert den Sollwert, dann kippt ein dem Summierglied nachgeschalteter Grenzwertmelder 24 und zündet über Zeitstufen 25, 26 den Wechselstromsteller 6. Über eine Verbindungsleitung gelangt das Ausgangssignal des Grenzwertmelders 17, der in jedem Nulldurchgang der Spannung uN kippt, an je einen Eingang der Zeitstufen 25 und 26 und sorgt dafür, daß jeweils nur derjenige Thyristor 7 oder 8 gezündet wird, der der Polarität der Spannungshalbschwingung entspricht.FIG. 4 shows, as an exemplary embodiment, the structure of an analog control device 10 to be used in the device according to FIG. 1, to which the mains voltage u N detected by the measuring element 11 is supplied as an input variable. The measurement signal is first rectified in an absolute value generator 14 and at the same time broken down into a sine and a cosine component in a vector identifier 15. The variable a (t) = XU N dt is formed in an integrator 16 from the measurement signal rectified in the magnitude generator. A zeroing pulse derived from the normalized sine component of the measurement signal via a limit indicator 17 and a time stage 18 resets the integrator at the end of each half-oscillation at the time t π-T / 2 by actuating a switch 19 and releases it again. At the summing point 20, a constant with the value 1 is added to the normalized cosine component of the vector identifier and the sum in a multiplier 21 with the constant factor that can be set on a potentiometer 22
Figure imgb0004
 multiplied. The product is the quantity b (t) which is fed to a summing element 23 in which the sum of the quantities representing the actual value of the voltage time area a (t) and b (t) are compared with a target value Φ *. The actual value exceeds the nominal value, then tilts a downstream the summing limit monitors 24 and ignites over time stages 25, 26 6, the AC power controller via a connecting line passes the output of the threshold detector 17, which tilts in each zero crossing of the voltage u N, to a respective input of the Time stages 25 and 26 and ensures that only that thyristor 7 or 8 is fired that corresponds to the polarity of the voltage half-oscillation.

Anstelle der bisher betrachteten Integralbildung kann das Integral jeder anderen Funktion von uN beispielsweise

Figure imgb0005
dt gebildet werden. Dabei sollte y ganzzahlig sein, damit die Realisierung einfach bleibt.Instead of the integral formation considered so far, the integral of any other function of u N can, for example
Figure imgb0005
 dt be formed. Here y should be an integer so that the implementation remains simple.

Da die Arbeitsweise der Steuereinrichtung auf mathematischen Operationen beruht, können anstelle einer analogen Rechenschaltung auch digitale Rechenschaltungen oder Mikroprozessoren eingesetzt werden.Since the mode of operation of the control device is based on mathematical operations, digital arithmetic circuits or microprocessors can also be used instead of an analog arithmetic circuit.

Claims (3)

1. Vorrichtung zur Konstanthaltung der Spannungszeitfläche zwischen je zwei Leitern eines Lastschwankungen unterworfenen, ein- oder mehrphasigen Wechselstromnetzes mittels einer an die beiden Leiter je einer Phase angeschlossenen Reihenschaltung aus einer Drosselspule und einem Wechselstromsteller, dessen antiparallel geschalteten, steuerbaren Ventilen Zündimpulse zugeführt sind, die aus der Abweichung zwischen einem vorgegebenen Sollwert und einer aus der Netzspannung mittels eines Integrators gebildeten Größe der Spannungszeitfläche über mindestens einen Grenzwertmelder abgeleitet sind, dadurch gekennzeichnet , daß der Istwert der Spannungszeitfläche der Netzspannung die Summe aus der vom Integrator (16) gebildeten Größe und einer in einer Rechenschaltung (15, 20, 21) laufend ermittelten, von der Reaktanz der Reihenschaltung (6, 9) abhängigen Restgröße der Spannungszeitfläche ist.1.Device for keeping the voltage time area constant between two conductors of a single-phase or multiphase AC network which is subject to load fluctuations by means of a series circuit connected to the two conductors, one phase in each case, from a choke coil and an alternating current regulator, the antiparallel, controllable valves of which ignition pulses are supplied from the deviation between a predetermined target value and a size of the voltage time area formed from the line voltage by means of an integrator are derived via at least one limit value indicator, characterized in that the actual value of the voltage time area of the line voltage is the sum of the size formed by the integrator (16) and one in one Arithmetic circuit (15, 20, 21) continuously determined residual size of the voltage time area dependent on the reactance of the series circuit (6, 9). 2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Rechenschaltung aus einem Vektoridentifizierer (15) dessen einer Ausgang ein dem Cosinus-anteil der Netzspannung entsprechendes Signal liefert, einem nachgeschalteten Summierglied (20), dem eine Konstante mit dem Wert "1" zugeführt ist, und einem Multiplizierer (21) besteht, dessen-Ausgangsgröße das Produkt aus der im Summierglied gebildeten Summe und aus einem an einem Potentiometer (22) eingestellten, aus der Netzspannung , der Netzfrequenz und dem Verhältnis der Netzreaktanz zur Reaktanz der Reihenschaltung gebildeten Faktor ist.2. Device according to claim 1, characterized in that the arithmetic circuit from a vector identifier (15) whose one output supplies a signal corresponding to the cosine component of the mains voltage, a downstream summing element (20), to which a constant with the value "1" is supplied is, and a multiplier (21), the output of which is the product of the sum formed in the summing element and a factor set on a potentiometer (22), formed from the line voltage, the line frequency and the ratio of the line reactance to the reactance of the series circuit . 3. Vorrichtung nach Anspruch 2, dadurch gekennzeichnet, daß aus einem dem Sinusanteil der Netzspannung entsprechenden Ausgangssignal des Vektoridentifizierers (15) mittels eines Grenzwertmelders (17) und einer Zeitstufe (18) ein den Integrator (16) jeweils im Nulldurchgang der Spannung zurückstellendes Signal gebildet ist.3. Apparatus according to claim 2, characterized in that from an output signal of the vector identifier (15) corresponding to the sine component of the line voltage (15) by means of a limit detector (17) and a time stage (18) a integrator (16) in each case in the zero crossing of the voltage resetting signal is formed is.
EP82111132A 1981-12-15 1982-12-02 Device for maintaining the voltage of a single or multiphase ac supply mains submitted to changing loads at a constant level Withdrawn EP0081752A3 (en)

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DE19813149706 DE3149706A1 (en) 1981-12-15 1981-12-15 DEVICE FOR MAINTAINING THE VOLTAGE OF A SINGLE OR MULTI-PHASE AC NETWORK SUBJECT TO LOAD VARIATION
DE3149706 1981-12-15

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US5867016A (en) * 1997-09-25 1999-02-02 Tektronix, Inc. Duty cycle based AC power control with reduced voltage fluctuations

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US3435248A (en) * 1966-12-27 1969-03-25 Borg Warner A-c voltage regulator
DE2334040B1 (en) * 1973-07-04 1974-10-31 Siemens Ag Device for regulating the effective value of a pulsating controlled variable

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US3889176A (en) * 1973-10-10 1975-06-10 Acme Electric Corp Reactive regulator
EP0026260B1 (en) * 1979-09-27 1984-03-28 Siemens Aktiengesellschaft Device for controlling the voltage between two conductors of an a.c. supply mains for a rapidly changing load

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3435248A (en) * 1966-12-27 1969-03-25 Borg Warner A-c voltage regulator
DE2334040B1 (en) * 1973-07-04 1974-10-31 Siemens Ag Device for regulating the effective value of a pulsating controlled variable

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EP0081752A3 (en) 1983-07-20
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CA1196956A (en) 1985-11-19
BR8207283A (en) 1983-10-18

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