Arrangement for generating a zero-current pulse and its use

Abstract

Arrangement for generating a zero-current pulse (1) for generating a zero-crossing current in an electrical component (3) carrying a direct current (2), in particular a vacuum interrupter, wherein the arrangement comprises an electrical energy storage device (4) with two poles (12), (13) via which the electrical energy storage device (4) can be charged from a voltage source (10), and a switch (5), and wherein a mesh can be formed with the arrangement via the energy storage device (4), the electrical component (3) carrying a direct current and the switch (5), such that the energy storage device (4) can be discharged when the switch (5) is closed by generating a zero-current pulse (1) flowing through the electrical component (3) in the opposite direction to the direct current (2), where the energy storage device (4) comprises a plurality of energy storage elements for the joint generation of a zero-current pulse (1), and the plurality of energy storage elements for the joint generation of a zero-current pulse (1) forms a chain conductor, wherein the energy storage elements are configured as chain links (6), (6'), (6'') each with a capacity (9), (9'), (9''), characterized by the fact that each chain link (6), (6'), (6'') is designed as a series connection of an inductor (7), (7'), (7''), a resistor (8), (8'), (8'') and a capacitor (9), (9'), (9''), the series connection of a first chain link (6) is formed between the poles (12), (13) of the energy storage device (4) and the series connection of a subsequent chain link (6'), (6'') is connected in parallel to the capacitor (9), (9') of the respective preceding chain link (6), (6').

Description

[0001] The present invention relates to an arrangement for generating a current-zero pulse to generate a current-zero crossing in an electrical component through which a direct current flows, in particular a vacuum tube, and to the use of the corresponding arrangement. State of the art

[0002] A vacuum tube is frequently used as a load or power switch in AC networks. To interrupt the anode current or switching current, the vacuum tube requires a negative voltage, which is provided by the negative half-wave of the AC voltage. If a DC current needs to be interrupted, a current pulse, or zero-crossing pulse, is required due to the lack of a zero crossing. This pulse is superimposed on the DC current to create the necessary zero crossing.

[0003] WO 2013 / 178696 A1 discloses a circuit breaker device for use in high-voltage direct current transmission, wherein the circuit breaker device consists of one module or several modules connected in series. DE 10 2011 079723 A1 discloses a DC line circuit breaker having a first node, a second node, a third node, a fourth node, and a fifth node. Furthermore, DE 10 2011 083514 A1 describes a DC circuit breaker with at least one interrupter and a commutator device arranged in parallel to the interrupter, wherein the commutator device comprises a capacitor circuit.

[0004] In previously known methods for generating an artificial zero-crossing of the current using a zero-current pulse, a simple RLC resonant circuit (a resonant circuit based on resistance, inductance, and capacitance) is typically employed. To switch off the direct current, the vacuum interrupter is opened, the zero-current pulse is applied, and the current is interrupted. A zero-current pulse generated by an RLC resonant circuit has a sinusoidal waveform. The frequency of the RLC resonant circuit is generally in the kHz range and thus significantly higher than the frequencies typically found in alternating current networks.

[0005] The current interruption by the vacuum switching tube occurs relatively reliably up to a certain maximum current transconductance dI / dt (derivative of the current with respect to time) at the current zero crossing. The current transconductance of the RLC resonant circuit corresponds to a cosine function. The dimensioning of the RLC resonant circuit can only be optimized for the magnitude of a specific, predefined current. Therefore, at the time of current interruption, different switching currents and a constant current-zero pulse result in different, potentially suboptimal, current transconductances at the zero crossing of the switching current.

[0006] Thus, an RLC resonant circuit designed to generate a high-amplitude zero-current pulse exhibits a very high initial current transconductance, which decreases with increasing time and amplitude according to the cosine function. If the DC current to be compensated is large, the zero-current crossing occurs at a time when the current transconductance has already decreased according to the cosine function and is therefore sufficiently low. However, if the DC current to be compensated is small, the zero-current crossing occurs at an earlier time when the current transconductance of the zero-current pulse is still very high, possibly too high. Object of the invention

[0007] The object of the invention is to provide an arrangement for generating a zero-current pulse which enables the interruption of switching currents of different magnitudes with a current steepness dI / dt that is as constant as possible.

[0008] The problem is solved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0009] According to the invention, an arrangement is provided for generating a zero-current pulse to create a zero-crossing current in an electrical component carrying a direct current, in particular a vacuum interrupter, wherein the arrangement comprises an electrical energy storage device with two poles, via which the electrical energy storage device can be charged from a voltage source, and a switch. A circuit can be formed with the arrangement via the energy storage device, the electrical component carrying a direct current, and the switch, such that the energy storage device can be discharged when the switch is closed by generating a zero-current pulse flowing through the electrical component in the opposite direction to the direct current. The energy storage device comprises a plurality of energy storage elements for the joint generation of a zero-current pulse.

[0010] One advantage of such an arrangement is that the shape, i.e., the amplitude over time, of the zero-current pulse can be shaped by superimposing the discharge curves of several energy storage elements. In this way, virtually arbitrarily shaped zero-current pulses can be generated, which may be required to interrupt direct currents in an electrical component. The term "electrical component" is to be understood so generally that it also includes a more complex—possibly integrated—circuit, or a device, in particular a conventional AC switching device.

[0011] Advantageously, the energy storage elements are designed differently, resulting in different discharge curves. The discharge of the majority of energy storage elements to jointly generate the zero-current pulse can occur in various ways, for example, in parallel, with time delays, dependently, or in series.

[0012] Advantageously, the energy storage device is designed such that a resonant circuit can be formed across the mesh when the switch is closed, causing the zero-current pulse to have alternating directions. This design offers the advantage that the connection point for the energy storage device to the conductor carrying the direct current can be positioned in the direction of the direct current upstream of the electrical component. When the energy storage device is discharged, the direct current flowing through the electrical component is initially amplified by the zero-current pulse before it reverses direction due to the resonant circuit and, after one half-cycle, compensates for the direct current with its negative direction.

[0013] According to the invention, the plurality of energy storage elements for the joint generation of a zero-current pulse form a chain conductor, wherein the energy storage elements are designed as chain links with a capacity each.

[0014] The term "chain conductor" refers to a chain-like electrical connection of similarly designed chain links in the form of electrical circuit arrangements.

[0015] The use of identical chain links offers the advantage of rationalizable manufacturing, and linking them offers the advantage of being able to form temporal dependencies or sequences.

[0016] According to the invention, the chain links of the chain conductor have inductances, resistances, and capacitances. An embodiment with passive components can be manufactured cost-effectively, and in particular, an arrangement can be formed from inductances, resistances, and capacitances that has a simple construction and also allows a controlled discharge process of a capacitance as an energy storage element.

[0017] According to the invention, each link in the chain is configured as an RLC element, i.e., each link is configured as a series connection of an inductor, a resistor, and a capacitor, wherein the series connection of a first link is connected between the poles of the energy storage device, and the series connection of a subsequent link is connected in parallel with the capacitor of the preceding link. Such a configuration offers the possibility of creating resonant circuits of different frequencies, resulting in zero-current pulse components with different current transconductances. In particular, it offers the possibility of creating zero-current pulses whose negative half-wave exhibits a low current transconductance at high amplitude. For example, a vacuum interrupter for interrupting a high direct current requires a zero-current pulse with high amplitude and low current transconductance.In comparison to an energy storage device that meets the relevant requirements and is built from only a pure RLC resonant circuit, a corresponding and appropriately parameterized ladder made of RLC elements requires less energy to be stored while delivering comparatively short current pulses and having smaller dimensions.

[0018] Advantageously, the arrangement comprises several energy storage elements dimensioned such that the zero-current pulse generated by the simultaneous discharge of the energy storage elements exhibits an approximately constant current slew rate across the entire segment. For example, the arrangement can be implemented as a chain conductor with several chain links whose inductances, resistances, and capacitances are dimensioned such that the zero-current pulse exhibits an approximately constant current slew rate across the entire segment.

[0019] Such an arrangement offers the advantage that it can be configured, for example, for a specific, nearly constant current transconductance, which, regardless of the magnitude of the DC current to be compensated, exhibits the specified current transconductance at the time of the zero-crossing current pulse. Thus, with appropriate parameterization, such an arrangement is suitable, for example, for compensating a DC current flowing through a vacuum interrupter, which is constant at the switching time, regardless of its magnitude, at a predefinable current transconductance. In other words, with this configuration, zero-crossing currents for DC currents of varying magnitudes can be generated with an optimal current transconductance.

[0020] Advantageously, the energy storage device comprises several, particularly preferably three, energy storage elements, dimensioned such that the zero-current pulse resulting from the simultaneous discharge of the energy storage elements exhibits an approximately triangular or ramp-shaped current waveform. Particularly preferably, the energy storage device comprises a chain conductor with three chain links, the inductances, resistances, and capacitances of which are dimensioned such that the zero-current pulse exhibits an approximately triangular or ramp-shaped current waveform. Such time-dependent zero-current pulse waveforms are easily implemented with passive components and provide a zero-current pulse with a constant current slope in certain sections.

[0021] The arrangement can further be designed such that the poles of the energy storage device can be connected to the voltage source via a charging resistor. It is also advantageous if the arrangement is designed such that this voltage source is the same voltage source that supplies the electrical energy for the direct current to be compensated. Such a design eliminates the need for a second voltage source. Advantageously, the charging resistor is arranged such that it forms a second loop with the voltage source, the electrical component, and the switch, and is not included in the aforementioned loop consisting of the switch, the electrical component, and the energy storage device, nor is it located in the current path of the direct current to be compensated.

[0022] Furthermore, the arrangement is advantageously designed such that it includes an energy absorber arranged parallel to the electrical component. This absorber allows the energy released due to a direct current interruption by the electrical component to be absorbed. Advantageously, the energy absorber is designed as a metal oxide current collector, for example, a metal oxide resistor or a metal oxide varistor. Metal oxide current collectors can be manufactured to be essentially age-resistant and are suitable for absorbing the energy generated during a discharge process.

[0023] Advantageously, this arrangement is used to generate a zero-current pulse in an electrical component carrying a direct current, where the electrical component is a vacuum switching tube. In such a use, the arrangement can be used to create a DC switch. Examples and drawings

[0024] The invention is explained in more detail below with reference to the accompanying drawings and by way of preferred embodiments.

[0025] They show Fig. 1 an embodiment of the invention with a chain ladder consisting of three chain links; Fig. Figure 2 shows an embodiment of an application of the invention for the design of a DC switch.

[0026] Fig. Figure 1 shows a preferred embodiment of the invention. Fig. Figure 1 shows an arrangement for generating a current zero pulse 1 to generate a current zero crossing in an electrical component 3 through which a direct current 2 flows, wherein the electrical component 3 is designed as a vacuum switching tube.

[0027] The arrangement includes an electrical energy storage device 4 with two poles 12, 13, which is connected to a Fig. The energy storage device 4 can be charged by the voltage source 10 shown. Furthermore, the arrangement forms a loop via the energy storage device 4, the DC-carrying electrical component 3 and a switch 5, such that the energy storage device 4 can be discharged when the switch 5 is closed, generating a zero-current pulse 1 which initially amplifies the DC current 2 via the electrical component 3.

[0028] The energy storage device 4 comprises a plurality of energy storage elements in the form of chain links 6, 6', and 6'' of a chain conductor for the joint generation of a zero-current pulse 1. The chain links 6, 6', 6'' of the chain conductor have inductances 7, 7', 7'', resistances 8, 8', 8'', and capacitances 9, 9', 9''. Each chain link 6, 6', 6'' is formed from a series connection of an inductance 7, 7', 7'', a resistance 8, 8', 8'', and a capacitance 9, 9', 9''. A series connection of a first chain link 6 is formed between the poles 12, 13 of the energy storage device 4. The series connection of a subsequent chain link 6´, 6´´ is connected in parallel to the capacitance 9, 9´ of the respective preceding chain link 6, 6´.

[0029] In such a configuration, the chain conductor forms a resonant circuit, the oscillation of which - provided the electrical component 3 is in a conductive state - can be initiated by closing the switch 5.

[0030] When switch 5 is closed, the capacitors 9, 9', 9'' discharge, forming a positive half-wave of a zero-current pulse 1. The positive half-wave of the zero-current pulse 1 has the same direction as the direct current 2, so that both currents initially add up in the electrical component 3.

[0031] After the capacitors 9, 9', 9'' are discharged, the inductors 7, 7', 7'' maintain the zero-current pulse 1 until the voltage U in the capacitors 9, 9', 9'' reverses polarity. As the voltage builds up, the amplitude of the zero-current pulse 1 decreases until it reaches zero.

[0032] Due to the reversal of the voltage U in the capacitors 9, 9', 9'', a negative half-wave follows the positive half-wave of the zero-current pulse 1. This negative half-wave of the zero-current pulse 1 opposes the direct current 2, so that, with appropriate dimensioning, the direct current 2 can be compensated by the negative half-wave of the zero-current pulse 1, and a zero-crossing of the current can be achieved for the sum of both currents in the electrical component 3.

[0033] The inductances 7, 7', 7'', resistances 8, 8', 8'' and capacitances 9, 9', 9'' of the chain links 6, 6', 6'' are dimensioned such that the current-zero pulse 1 has an approximately constant current steepness section by section.

[0034] Fig. Figure 2 shows an embodiment of an application of the invention for the design of a DC switch 17. The design of the energy storage device 4 and its interaction with the electrical component 3 and the switch 5 are shown in Figure 2. Fig. 1 identical. About the in Fig. In addition to the arrangement described in point 1, it is also Fig. 2 evident that the in Fig. 1 Energy storage device 4 shown, here represented by the chain conductor with the inductances 7, 7', 7'', the resistors 8, 8', 8'' and the capacitors 9, 9', 9'' is connected to the voltage source 10 via a charging resistor 11.

[0035] Furthermore, the same voltage source 10 supplies the electrical energy for the direct current 2 to be compensated. The charging resistor 11 is arranged such that it forms a second loop with the voltage source 10, the electrical component 3, and the switch 5, and is not included in the previously mentioned loop consisting of the switch 5, the electrical component 3, and the energy storage device 4, nor is it located in the current path of the direct current 2 to be compensated. A further, third loop, consisting of the voltage source 10, the energy storage device 4, and the charging resistor 11, allows the capacitors 9, 9', 9'' to be charged to the voltage U. DC the voltage source 10, provided that switch 5 is open.

[0036] When switch 5 is closed, the capacitors 9, 9', 9'' of the energy storage device 4 discharge via the electrical component 3 and the switch 5 in the form of the zero-current pulse 1. The electrical component 3, designed as a vacuum switching tube, is coupled to switch 5 and is opened when switch 5 is closed, so that when the zero-current crossing caused by the negative half-wave of the zero-current pulse 1 is reached, the direct current 2 can be switched off.

[0037] At the voltage source 10 with the voltage U DC A switching load with an inductive component 15 and a resistive component 16 is connected via the DC switch 17, which determines the DC current 2. Furthermore, Fig. 2 can be seen that the arrangement has an energy absorber 14 which is arranged parallel to the electrical component 3.

[0038] When the direct current 2 is interrupted by the electrical component 3, an overvoltage arises due to the inductive component 15 of the switching load via the electrical component 3, which can be absorbed by the energy absorber 14, which is designed as a metal oxide arrester. Reference sign 1 Current-zero pulse 2 Direct current 3 Electrical component 4 Energy storage 5 switches 6 chain links 7 Inductance 8 Resistance 9 capacity 10 Voltage source 11 Charging resistor 12 poles of the energy storage device 13 poles of the energy storage system 14 energy absorbers 15 switching load, inductive component 16 Switching load, resistive component 17 DC switches

Claims

Arrangement for generating a zero-current pulse (1) for generating a zero-crossing current in an electrical component (3) carrying a direct current (2), in particular a vacuum interrupter, wherein the arrangement comprises an electrical energy storage device (4) with two poles (12), (13) via which the electrical energy storage device (4) can be charged from a voltage source (10), and a switch (5), and wherein a mesh can be formed with the arrangement via the energy storage device (4), the electrical component (3) carrying a direct current and the switch (5), such that the energy storage device (4) can be discharged when the switch (5) is closed by generating a zero-current pulse (1) flowing through the electrical component (3) in the opposite direction to the direct current (2), wherein the energy storage device (4) comprises a plurality of energy storage elements for the joint generation of a zero-current pulse (1),and the plurality of energy storage elements for the joint generation of a zero-current pulse (1) form a chain conductor, wherein the energy storage elements are configured as chain links (6), (6'), (6'') each with a capacitance (9), (9'), (9''), characterized in that each chain link (6), (6'), (6'') is configured as a series connection of an inductance (7), (7'), (7''), a resistance (8), (8'), (8'') and a capacitance (9), (9'), (9''), the series connection of a first chain link (6) is configured between the poles (12), (13) of the energy storage device (4) and the series connection of a subsequent chain link (6'), (6'') is connected in parallel to the capacitance (9), (9') of the preceding chain link (6), (6'). Arrangement according to claim 1, characterized in that the energy storage device (4) is designed such that a resonant circuit can be formed via the mesh when the switch (5) is closed, so that the current-zero pulse (1) has alternating directions. Arrangement according to one of the preceding claims, characterized in that the arrangement has an energy absorber (14) arranged parallel to the electrical component (3). Arrangement according to claim 3, characterized in that the energy absorber (14) is designed as a metal oxide drain. Use of an arrangement according to one of the preceding claims for generating a zero-current pulse (1) in an electrical component (3) through which a direct current (2) flows, characterized in that the electrical component (3) is a vacuum switching tube.

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