DD142832A3 - OVERVOLTAGE PROTECTION DEVICE FOR NETWORKED POWER SUPPLY - Google Patents

Abstract

The invention is a device for protection against overvoltages caused by switching operations arise in mains-deleted converters, which with non-linear protection elements and a de-energizing circuit and high inductance consumers, e.g. DC machines, dine. It should be unwanted Impairment of the operational safety during overvoltage protection avoided and an effective surge protection among the Conditions of real .Stromrichterbetriebes be created. To avoid the occurrence of the non - conductive state of energized de-energizing valve by one of a Vibration effect caused negative Tniordenspannungsirapulses If an attenuation reactor is inserted in the de-energizing circuit. Overvoltage protection device is provided with an information processing equipped, which depends on the height, type and duration the overvoltage excites the de-energizing circuit or the power converter disconnects from the grid «~ Pig.3 -

Description

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Title of the invention

Surge protection device for mains extinguished converters

Field of application of the invention

The invention relates to a device for the protection of power converters that feed consumers with high inductance, against overvoltages caused by switching operations. In high inductance (> 1H) consumers, e.g. The fields of DC machines store energy from 1CrJ to 1CrJ. When switching off, d.ho interruption of the circuit, this high energy is converted as heat energy. This happens in the form of a. Arc over the switching point, which continues to the consumer such a high voltage that the electronic components of the converter are destroyed.

Characteristic, the known technical solutions

To avoid these destructive effects, it is necessary to open the consumer current at the moment of shutdown a way via circuit elements such that the energy conversion is performed without the formation of a dangerous overvoltage. At a

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Representative circuit (Fig.1) of a power converter with the valves V in fully controlled Drehstrombrückenschal device to the currently known measures and their deficiency v / ground explained. The switching paths S are the switches arranged in or upstream of a power converter or fuses, which can shunt in any combination. In particular, the switches S1 represent switching devices such as e.g. Contactors in the Stromrich- 'terzuleitungen R, S, T, while the switch S2 represent mainly branch fuses. The consumer is represented by the series connection of R and L.

The arrangement of a zero valve V ^ (diode) parallel to the load 1 leads to the voltage near zero across the load 1. However, the performance of the power converter is affected by no inverter operation (demagnetization of L with negative voltage at the load) is more possible. The antiparallel arrangement of a second power converter (reverse operation) is not possible because the zero valve V ^ for. this "represents a short circuit.

The arrangement of a parallel resistor Rp leads to overvoltages within permissible limits if the value of the parallel resistor Rp is limited to approximately 3 to 4 times the value of the load resistance R. Due to the power loss of the parallel resistor Rp, however, the efficiency of the entire device is reduced by 25 % to 30%. Furthermore, the dynamic behavior (current ir as a puncture of time) is significantly negatively affected.

The arrangement of a non-linear element Rp leads according to the U-I characteristic of the available components (varistors, Selenbegrenzer) to overvoltage in just allowable height »Also, the power loss in normal operation

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(Rated voltage at the element) very low. These elements may umaetzen However only a fraction of the stored energy in the load and have a short conduction time relieved w; earth _e

The arrangement of a controlled zero valve Vj, (thyristor) is a commonly used measure for limiting the voltage. When exceeding a certain overvoltage when switching off the thyristor Vjt is ignited and acts as a zero valve. There are-also in power converters that do not contain the switch S2 (power converters with string fuses) operated at least the thyristors V3 (Pig.1) by means of an ignition device according to ignition V ^ as a controlled zero valves (DT-AS 1 283 358). The arrangement of controlled zero valves but has under the conditions of real power converter operation some shortcomings that put the reliability in embossing. Under real operation is in addition to the arrangement according to Pig.1 to understand that the converter includes capacitors, which serve to damp the so-called carrier jam effect and the perturbation, and that further connected to the input terminals of the power converter, the ignition pulses generating control device is connected. At a two-pulse power converter (Pig.2) with a capacitor C at the input as a substitute for the aforementioned capacitors in the power converter, the adverse phenomena occurring should be explained. At the input of the power converter, a non-linear element R, which preferably protects the power converter against overvoltages coming from the network, is arranged. At the time of shutdown by the S.chaltstrecke SI valves V1.1 and V2.2 of the converter should be conductive. The current i _T is taken over by the nonlinear element R and the capacitor C

is charged to the overvoltage dropping across R _n (u _c in the direction of the arrow). The controlled zero valve V ^ is ignited, with a delay, which is necessary so that no ignition during normal operation by overvoltages from the network. With ignition of the controlled zero valve V ^ the converter valves V1.1 and V2.2 are non-conductive, the controller 2 is supplied from the condenser G and ignites the converter valves V2.1 and 1.2, whereby the zero valve Y " by a negative Anodenspan- ' nungsimpuls (ug in the arrow direction) is non-conductive. The current JL. Now flows in the reverse direction through the non-linear element R and the capacitor C is reloaded, and if the overvoltage detection 3 is dynamically capable of the zero valve V ^ to ignite vii repetition of the process. If the zero valve V "is not ignited, then the current i _{T flows} continuously, only in

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alternating direction, through the non-linear element R The network-deleted circuit of the converter thus operates at shutdown by the switching path S1 as a self-extinguished inverter with energy supply. the inductance L of the consumer 1 further, wherein the non-linear element R is overwhelmed in terms of energy expenditure and the control device 2 receives over an unacceptably long time overvoltage. This oscillating effect leads in a three-phase bridge circuit to further adverse phenomena. In case of failure of a power supply line (circuit of one of the switches S1 in Figure 1), the power converter under the conditions of the oscillating operation on the remaining power supply lines still provide load current and the amplitude of the overvoltage is higher on the network side of the converter than on the output side. Another disadvantage is that by ignition of the controlled zero valve Vjj_ coming out of the network

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Overvoltages, in particular in the case of an antiparallel arrangement of a second power converter, a short circuit via the zero valve V «is produced. It is customary to switch a resistor in order to limit the current in series with the zero valve V _n and to suppress the formation of the ignition pulses in the control device. The latter measure, however, means a malfunction.

Object of the invention

The aim of the invention is to avert the caused by the known measures for overvoltage protection undesirable effects of the reliability of the converter.

Explanation of the essence of the invention

- The technical problem which is solved by the invention.

The invention has for its object to provide under the conditions of real power converter operation an effective, malfunction avoidance, overvoltage protection device for the protection of high-inductive loads feeding net.zgelöschte power converters, which are caused by switching operations on the power converters associated switching paths.

Features of the invention

The object is achieved by-dissolved in that in a known Entregerkreis consisting of the series arrangement of a limiting resistor

and a de-exciter valve assembly. a high initial inductance nonlinear de-excitation dope is combined in series and the surge protector is combined with information processing consisting of a pulse generator, a control angle controller, and a duration detector. The pulse generator each has one input for line and DC side voltage sensing and signal outputs ^ which at the same time to the pulse amplifier for the Entregerventilansteuerung ,. on the control angle controller, which is connected via a signal output to the Zündimpulssteuereinrichtung, and the Wirkdauermeßeinrichtung which is connected via a signal output to the network-side switching path, are guided ·

Further advantageous embodiments of the invention are

- That the provided on the pulse generator signal inputs to the mains and DC side voltage detection OR are linked, are performed on a threshold • valuer and carried out by means of a pulse train excitation of the Entregerventilansteuerung time delay;

- That in the Steuerwinkelsteller from the first pulse of the pulse generator, a time-limited signal is derived, which in the ignition pulse st euer your device setting the ignition pulses to the value of about 90 ° electrically causes j

In that case, the number of pulses leading to the shutdown of the power converter is a puncture of the mean pulse interval, namely the number of pulses leading to the shutdown of the power converter.

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art that pulses are not switched off at a large distance.

Embodiment "

The invention will be explained in more detail below using an exemplary embodiment.

A conventional power converter arrangement in antiparallel circuit, consisting of 12 valves V and the usual capacitor arrangement (not shown) for Trägerstaueffektbedämpfung and punk interference, the switching sections S1 and S2 and the power switch S3 »the usual network-side non-linear protection elements R-, the Zündimpulssteuereinrichtung 2 and the highly inductive load 1 with the resistive and inductive load components R and L ^ is connected to a protective device consisting of a per se known Entregerventilanordnung with the anti-parallel thyristors Vg - and Vg - ^ ¹¹ series circuit with the Begrenzungswider st and Rg and Ent'- invention Recirculation damper Lg connected in series. The nonlinear element R _n2 lies parallel to the consumer 1 and also to the protective device described. The protective device is assigned an information processing 4 consisting of a pulse generator 5 "a control angle adjuster 6 and an effective duration measuring device 7, which is supplied by a power supply unit 8 which advantageously ao is configured so that its output voltage is maintained in case of failure of the voltage of a power supply line or short circuit of the same against another supply line. In the pulse generator 5, the voltage on the input and output side of the power converter is detected via the OR-linked signal inputs Si1 and Si2. If an adjustable threshold is exceeded for

-S

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the duration of the excess rectangular pulses (with a width of about lOQyus and a distance of about 250 / us) generated, which are guided via a pulse amplifier 9 to the control electrode of the just to ignite ^ ntregerventils Y "and cause an activation of the Entregerventilkreises. In order to avoid pulse generation by overvoltage of short duration from the rush, which is not due to a switching action on the switching sections S1 to S3, the excitation is executed with a time delay, so that for the pail of a switching operation the nonlinear elements R ₁ and R ~ in the period between the occurrence of the overvoltage and its suppression by the Entregerventileinschaltuns: must implement a small part of the energy contained in the inductance L of the consumer 1. The generation of a pulse train causes a de-energizing circuit to be formed even when excitation has taken place by an overvoltage of longer duration from the mains, for example, by switching off a converter arrangement on the same network with a high inductance consumer and switching on the switching paths S1 to S3 are performed. To avoid a malfunction in the form that especially in anti-parallel circuit of the inverter according to Pig.3 excitation by overvoltage from the grid, and by switching the Entregerkreises an additional load by the Begrenzungswider st and Rg is formed in the Steuerwinkelsteller 6 by the the first pulse from the pulse generator formed a short-term (about 30 ms long) command, which causes in.der Zündimpulssteuereinrichtung 2 an adjustment of the ignition pulses for the power converter valves V to the value of about 90 ° electrically. As a result, at the output of the power converter, almost only AC voltage and the current-carrying de-excitation voltage are present.

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Valve V _E becomes nonconductive due to a negative anode voltage, and after resuming the control command, the normal operating state is restored. By the Wirkdauermeßeinrichtung 7, the time of occurrence of an overvoltage by counting the pulses from the pulse generator 5 is detected and given a certain number of pulses, a command to shutdown the power converter to the switching path S3 in the event that in particular by failure of a power line continuously the already described oscillation effect occurs and leads to an unduly long overvoltage load. ,

According to the time-dependent overload capacity of the non-linear elements R- and Rp, the number of pulses leading to the shutdown, a puncture of the mean Impulsabstande3 in such a way that at pulses at a large distance no shutdown command occurs »

The inventive insertion of the Entregerkreisdämpfungsdrossel L- the entry of the non-conductive state of the just energized Entregerventils Vg is prevented in the oscillating effect. With appropriate design of the Entregerkreisdämpfungsdrossel L ™ ensures that the occurring at the 'swinging effect described negative anode voltage pulse has no current zero result. To ensure the damping effect, the Entregerkreisdämpfungsdrossel L ™ at low current i ,. a high inductance and can have a small inductance at high current. Consequently, the Entregerkreisdämpfungsdrossel is designed as a so-called non-linear inductor with current-dependent inductance, as required to secure the puncture of the control angle actuator, where again the smallest possible inductance is required.

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The overvoltage protection device according to the invention: is not limited to power converter circuits according to FIGS. 1 and 3, but is equally advantageously used e.g. for a 2pula bridge circuit or 3-pulse center-point circuit, as well as for converters in set-up mode applicable ·

If a power converter does not include the switching paths S2, only the signal sensing Si1 is used on the power converter side and the DC side non-linear element Rp can be replaced by a high-resistance resistor to prevent overvoltages due to residual currents caused by the holding current of the thyristors V and Vg are to be replaced. It is also possible, instead of detecting the voltage, to indirectly carry the current through the non-linear elements as an effect of an overvoltage stress on the signal inputs Si1 and Si2. The overvoltage protection device also acts in the manner described if, instead of the non-linear elements, energy stores are arranged in the form of non-reactive capacitors connected, wherein, under reaction-free conditions, e.g. the connection via a rectifier bridge circuit is to be understood.

Claims (4)

Invention claim: Overvoltage protection device for high-inductive loads feeding network-deleted converters, in particular reversing converter with controllable valves, the power converter has switching paths in the converter leads and converter branches, while the grid side overvoltage protection elements and a Zündimpulssteuereinrichtung for the converter valves are connected and the DC side parallel to the consumer a non-linear overvoltage protection element and a de-energizing circuit is connected in which the de-energizing circuit is a series connection of a limiting resistor with a de-regulating valve arrangement consisting of a controllable valve controlled by a pulse amplifier for each current direction, characterized in that in the de-energizing circuit in series with the limiting resistor (Rg) and the de-regulating valve arrangement (Vg ₁ Vg ρ) is a non-linear de-excitation (Lg) inductor with high initial inductance and that the overvoltage protection device is combined with information processing (4) consisting of a pulse generator (5), a control angle adjuster (6), and a duration measuring device (7), the impulse 204496 generator (5) each having a signal input to the network and gleichatromaeitigen Spannungserfaasung (Si1; Si2) and signal outputs from the pulse generator , toroid (5) on the impulse amplifier (9) for deactivating valve control, on the control :. Angle plate (6), which is connected via a signal output to the Zündimpulssteuereinrichtung (2), and the Wirkdauermeßeinrichtung (7), which is connected via a signal output to the network-side switching path (S3) are guided. 2. Overvoltage protection device according to item 1, characterized in that the signal inputs (Si1; Si2) of the pulse generator (5) provided for line and line current-side voltage detection are ODBR-linked and fed to a threshold value generator, and in that the excitation of the deactivation valve control takes place by means of a pulse train is executed with a time delay. - 3. overvoltage protection device according to item 1, characterized in that in the Steuerwinkelsteller (6) from the first pulse of the pulse generator (5) a time-limited signal is derived, which in the Zündimpulssteuereinrichtung (2) an adjustment of the ignition pulses to the value of about 90 ° electrically causes. 4 · overvoltage protection device according to item 1, characterized in that the duration measuring device (7) includes a pulse counting circuit which triggers a shutdown command for the power converter after a certain number of pulses. 20449 Overvoltage protection device according to item 4, characterized in that the number of pulses that leads to the shutdown of the power converter, a puncture of the average pulse spacing and in such a way that when pulses at a large distance no shutdown occurs. - For this 2 sheets drawings -