Switch arrangement

Abstract

A switching arrangement (1) for interrupting an electric current, in particular a short-circuit current, with a high switching rate, it is proposed that the switching arrangement (1) comprises - a main line (2), which has a first SCR arrangement (3), which first SCR arrangement comprises at least a first SCR (4) and a first reverse-conducting diode (5) arranged parallel to the first SCR (4), - a first bypass line (6), which is connected to the main line (2) and is arranged parallel to the first SCR arrangement (3), - the first bypass line (6) comprises a second SCR arrangement (7), which second SCR arrangement comprises at least a second SCR (8) arranged with the same polarity as the first reverse-conducting diode (5), - the first bypass line (6) further comprises at least one capacitor (9) and a DC voltage source (10), which DC voltage source is connected to the capacitor (9) for precharging the capacitor (9).

Description

Technical Field

[0001] The present disclosure relates to a switching arrangement. Background Art

[0002] Modern circuit breakers nowadays typically increasingly include semiconductor switching arrangements for interrupting current even under fault conditions, especially short circuits. Such circuit breakers can be hybrid arrangements, as described by the applicant in WO 2015 / 028634 A1, or solid-state circuit breakers. Hybrid circuit breakers use semiconductor elements only for switching operations. Current does not flow through the semiconductors during normal operation. The advantage of this design is the low resistance and thus low voltage drop and low losses of these circuit breakers. The disadvantage is the need for an ultra-fast mechanical switch in the main line, which causes a delay anyway.

[0003] Solid-state circuit breakers do not require an ultra-fast mechanical switch in the main line. However, a typical problem with solid-state circuit breakers is the resistance during normal operation, which is caused by at least one switching semiconductor arranged in the main line. Current must flow through this semiconductor. The resistance causes a significant voltage drop and thus heating of the circuit breaker. Heat must be dissipated. Frequent thermal ripples also reduce the lifespan of the semiconductor elements. Summary of the Invention

[0004] The object of the present invention is to overcome the disadvantages of the prior art by providing a switching arrangement having low conduction state losses and the ability to turn off high in-rush currents.

[0005] According to the present invention, this object is solved by the following features.

[0006] A switching arrangement for interrupting current, especially short-circuit current, at a high switching rate, the switching arrangement comprising:

[0007] - a main line having a first SCR arrangement including at least a first SCR and a first reverse-conducting diode arranged in parallel with the first SCR arrangement,

[0008] - a first bypass line connected to the main line and arranged in parallel with the first SCR arrangement,

[0009] - the first bypass line includes a second SCR arrangement including at least a second SCR arranged with the same polarity as the first reverse-conducting diode,

[0010] - the first bypass line further includes at least one capacitor and a DC voltage source connected to the capacitor to pre-charge the capacitor.

[0011] Therefore, the switching arrangement can switch high currents, even high rising short-circuit currents. The SCR thyristor (hereinafter only referred to as SCR in the text) has an extremely low resistance in the conducting state, thus causing a low voltage drop and therefore low losses at high currents compared to even unipolar or bipolar transistors. Therefore, the switching arrangement 1 has a low heating tendency. The SCR has an extremely high blocking / reverse voltage and excellent overload capacity. However, the commutation process of the SCR arrangement according to the prior art is complex because the SCR does not have its own commutation ability and is therefore not suitable for simple use in the circuit breaker 21. The actual switching arrangement 1 can be commutated in a short time and can commutate the current, especially short-circuit current, at a high commutation rate of several kiloamperes per second.

[0012] The switching arrangement is even suitable for solid-state circuit breakers or hybrid circuit breakers. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is described with reference to the accompanying drawings. The drawings only show preferred embodiments of the present invention.

[0014] Figure 1 is a first preferred embodiment of an actual switching arrangement for unipolar current switching operation;

[0015] Figure 2 is a second preferred embodiment of the actual switching arrangement;

[0016] Figure 3 is a third preferred embodiment of the actual switching arrangement;

[0017] Figure 4 is a second preferred embodiment of the actual switching arrangement depicting additional features of the switching arrangement; and

[0018] Figure 5 is a block diagram of a solid-state circuit breaker having an actual switching arrangement. DETAILED DESCRIPTION

[0019] Figures 1 to 4 Shows a preferred embodiment of a switching arrangement 1 for commutating a current, especially a short-circuit current, at a high commutation rate, the switching arrangement 1 comprising:

[0020] - a main line 2 having a first SCR arrangement 3, the first SCR arrangement comprising at least a first SCR 4 and a first reverse-conducting diode 5 arranged in parallel with the first SCR 4,

[0021] - a first bypass line 6 connected to the main line 2 and arranged in parallel with the first SCR arrangement 3,

[0022] - The first bypass line 6 includes a second SCR arrangement 7, which includes at least a second SCR 8 arranged with the same polarity as the first reverse conducting diode 5.

[0023] - The first bypass line 6 further includes at least one capacitor 9 and a DC voltage source 10, which is connected to the capacitor 9 to pre - charge the capacitor 9.

[0024] Therefore, the switching arrangement can switch high currents, even high - rising short - circuit currents. The SCR thyristor (hereinafter only referred to as SCR in the text) has an extremely low resistance in the conducting state, resulting in a low voltage drop and thus low losses at high currents compared to even unipolar or bipolar transistors. Therefore, the switching arrangement 1 has a low heating tendency. The SCR has an extremely high blocking / reverse voltage and excellent overload capacity. However, the commutation process of SCR arrangements according to the prior art is complex because the SCR does not have its own commutation ability and is not suitable for simple use in a circuit breaker 21. The actual switching arrangement 1 can interrupt in a short time and is capable of interrupting current, especially short - circuit current, at a high commutation rate of several kilo - amperes per second. SCR is a common shortcut for silicon - controlled rectifier. The SCR is a type of thyristor.

[0025] The switching arrangement 1 is suitable for a solid - state circuit breaker 21. Figure 5 A block diagram showing a solid - state circuit breaker 21 including the actual switching arrangement 1 is shown. The circuit breaker further includes a clamping device 24 and a current - splitting relay 23 or a cut - off device. According to Figure 5 the circuit breaker includes two lines 2, 28. However, the circuit breaker can include a different number of lines.

[0026] The switching arrangement 1 is also suitable for devices different from the circuit breaker 1.

[0027] The switching arrangement 1 is suitable for interrupting current at a high commutation rate, especially short - circuit current. Preferably, the high commutation rate is a commutation rate higher than 1000 A / s, especially higher than 10,000 A / s, and especially preferably higher than 100,000 A / s.

[0028] The switching arrangement 1 includes a first SCR arrangement 3 arranged in the main line 2. The first SCR arrangement 3 includes at least a first SCR 4 and a first reverse conducting diode 5. Generally, the first reverse conducting diode 5 is arranged in parallel with the first SCR 4 with a different polarity. According to a preferred actual embodiment, the first SCR arrangement 3 further includes a buffer circuit 26 and a driver unit 25, as Figure 4 shown. These are standard components commonly used for semiconductor switching arrangements.

[0029] The first bypass line 6 is connected to the main line 2. The first bypass line 6 is arranged in a manner parallel to the first SCR arrangement 3 and bypasses the first SCR arrangement 3. In the first bypass line 6, a second SCR arrangement 7 is arranged. The second SCR arrangement 7 includes at least a second SCR 8 arranged with the same polarity as the first reverse-conductive diode 5, as can be seen in Figures 1 to 4 As shown in Figure 4 , the second SCR arrangement 7 further includes a buffer circuit 26 and a driver unit 25. These are standard components commonly used in most semiconductor switch arrangements.

[0030] The first bypass line 6 further includes at least one capacitor 9. A DC voltage source 10 is connected to the capacitor 9. The DC voltage source 10 is preferably controllable. This means that it can be connected to or disconnected from the capacitor 9 at least. The DC voltage source 10 charges the capacitor 9 and holds it in a charged state.

[0031] Specifically, the voltage on the capacitor 9 is always checked to ensure the breaking capacity of the switch arrangement 1 - if the voltage drop control system 14 places the switch arrangement 1 in a safe off state.

[0032] The switch arrangement 1 includes a control unit 14 as shown in Figure 4 and 5 . The control unit 14 is connected to the first SCR 4 and the second SCR 8 through its respective driver units 25. The control unit 14 is also connected to the DC voltage source 10 through a corresponding switch to disconnect the DC voltage source 10 from the capacitor 9.

[0033] In the on state of the switch arrangement 1, the control unit 14 provides an on signal or potential to the first SCR 4. In the case of AC, the control unit 14 or the driver unit 25 provides a pulse signal to the first SCR 4. It is obvious that the embodiment according to Figure 1 is only suitable for DC unidirectional breaking capacity. The embodiment according to Figures 2 to 4 can also be used in an AC power grid.

[0034] To disconnect the switch arrangement 1, the control unit 14 first turns on the second SCR 8 and stops sending pulses to the first SCR 4 by providing a suitable signal to the driver unit 25. If the design of the DC voltage source 10 requires it, the control unit 14 further disconnects the DC voltage source 10 and disconnects it from the capacitor 9 accordingly. Another option is the current limiting ability of the DC voltage source 10, which does not require disconnection. The capacitor 9 now discharges via the first bypass line 6. At the start of the disconnection operation, the current in the first bypass line 6 must be higher than the current in the main line 2. The first SCR 4 becomes blocking. When the capacitor 9 is disconnected from the DC voltage 10 source or separated by a high impedance, the capacitor 9 discharges and the current in the main line 2 can be completely cut off by commuting the second SCR 8 to the opposite polarity.

[0035] It has been shown that for the disconnection process, it is important that the current in the first bypass line 6 is higher than the current in the main line 2. According to a preferred embodiment, the first bypass line 6 further includes at least one inductor 11 arranged in series with the capacitor 9. The capacitor 9 and the inductor 11 form a resonant circuit 12. A sudden current change such as a step causes the resonant circuit 12 to start oscillating at its natural or resonant frequency, resulting in a resonant increase in the current in the first bypass line 6. This ensures that the current in the first bypass line 6 is higher than the current in the main line 2 outside the bypass section.

[0036] According to another preferred embodiment, the resonant circuit 12 further includes at least one resistor 13. The resistor 13 does not affect the resonant frequency, but affects the damping and time constant, and reduces the time required for the disconnection process.

[0037] Alternatively, the resistance of the inductor 11 can be used for this purpose.

[0038] Compared with the embodiment according to Figure 1 the embodiment according to Figures 2 to 4 includes other components. According to these embodiments, the main line 2 further includes a third SCR arrangement 15, which includes at least a third SCR 16 and a third reverse conducting diode 17 arranged in parallel with the third SCR 16. As shown only in Figure 4 the third SCR arrangement 15 further includes a common driver unit 25 and a buffer circuit 26. The third SCR arrangement 15 is arranged in the main line 2 with a polarity opposite to that of the first SCR arrangement 3. According to Figure 2 and Figure 3 the embodiments only differ in terms of polarity. Note that the name "third" reverse conducting diode 17 is chosen because it is part of the third SCR arrangement 15 and the second reverse conducting diode is not part of the described switch arrangement.

[0039] The switch arrangement 1 further includes a second bypass line 18, which is connected to the main line 2 and arranged in parallel with the third SCR arrangement 15. The second bypass line 18 includes a fourth SCR arrangement 19, which includes at least a fourth SCR 20 arranged with the same polarity as the third reverse conducting diode 17.

[0040] In principle, the second bypass line 18 can be embodied as a complete mirror image of the first bypass line 6, which has a separate second capacitor and a separate second DC voltage source, as well as other preferred components. However, it is not necessary to provide these components to the switch arrangement 1. According to the Figures 2 to 4 preferred embodiment shown, it is shown that the second bypass line 18 is connected to the first bypass line 6 at a certain point, and the capacitor 9 is part of both the first bypass line 6 and the second bypass line 18. Depending on the polarity of the voltage, either the first bypass line 6 or the second bypass line 18 is energized. Therefore, it is not necessary to provide a second capacitor and a second CD voltage source.

[0041] According to the preferred embodiment, the first bypass line 6 includes a resonant circuit 12 and the second bypass line 18 is connected to the first bypass line 6 at a certain point or in a certain way such that the resonant circuit 12 is part of both the first bypass line 6 and the second bypass line 18. The advantages of the resonant circuit 12 have been described. Moreover, an additional resistor 13 can be implemented, as Figures 2 to 4 shown.

[0042] The control unit 14 is also connected to the third SCR 16 and the fourth SCR 20 via corresponding separate driver units 15. In order to cut off the switch arrangement 1 according to Figures 2 to 4 one of them, the control unit 14 first turns on the second SCR 8 and the fourth SCR 20, and blocks the pulses to the first SCR 4 and the third SCR 16. Then, if necessary, the control unit 14 further cuts off the DC voltage source 10. The cut-off process has been described.

[0043] In order to reduce the amount of energy stored in the capacitor 9 for the cut-off process, the control unit 14 can sense the direction of the current in the main line 2 via a current sensor 22. Depending on the current sensing, it can turn on only one of the second SCR 8 or the fourth SCR 20. In addition to the positive effect of lower energy, it also reduces the current and thermal load on the first SCR 4 or the third SCR 16.

[0044] Figure 4 The grid source 27 is further shown.

[0045] The following is for understanding and explaining the principle of the actual disclosure.

[0046] A feature is typically introduced with the numeral "a" or "one". Thus, unless otherwise stated in the context, "a" or "one" should not be construed as a numerical term.

[0047] The conjunction "or" shall be interpreted as inclusive rather than exclusive. Unless otherwise specified in the context, "A or B" also includes "A and B", where "A" and "B" represent any features.

[0048] Unless the disclosure of the present invention otherwise defines, in several embodiments, ordinal numeral terms such as "first", "second", or "third" are used to specifically distinguish feature X or object Y. In particular, a feature X or object Y having an ordinal numeral term in the claims does not mean that the embodiments of the present invention covered by the claims must have another feature X or another object Y.

[0049] Unless otherwise specified in the context, the combination of "substantially" with a numerical value includes a tolerance of ±10% around the given numerical value.

[0050] Unless otherwise specified in the context, for a range of values, the endpoints are included.

Claims

1. A switching arrangement (1) for interrupting an electric current at a high switching rate, said switching arrangement (1) comprising: - a main line (2) having a first SCR arrangement (3), said first SCR arrangement comprising at least a first SCR (4) and a first reverse conducting diode (5) arranged in parallel with said first SCR (4), - a first bypass line (6) connected to said main line (2) and arranged in parallel with said first SCR arrangement (3), - said first bypass line (6) comprising a second SCR arrangement (7), said second SCR arrangement comprising at least a second SCR (8) arranged with the same polarity as said first reverse conducting diode (5), - said first bypass line (6) further comprising at least one capacitor (9) and a DC voltage source (10), said DC voltage source being connected to said capacitor (9) for precharging said capacitor (9).

2. The switching arrangement (1) according to claim 1, characterized in that said first bypass line (6) further comprises at least one inductor (11) arranged in series with said capacitor (9), and said capacitor (9) and said inductor (11) form a resonant circuit (12).

3. The switching arrangement (1) according to claim 2, characterized in that said resonant circuit (12) further comprises at least one resistor (13).

4. The switching arrangement (1) according to claim 1, characterized in that said switching arrangement (1) comprises a control unit (14), said control unit being connected to said first SCR (4), said second SCR (8) and said DC voltage source (10), and for interrupting said switching arrangement (1) said control unit (14) first turns on said second SCR (8) and turns off said first SCR (4), and said control unit (14) further turns off said DC voltage source (10).

5. The switching arrangement (1) according to claim 1, characterized in that the main line (2) further comprises a third SCR arrangement (15), said third SCR arrangement comprising at least a third SCR (16) and a third reverse conducting diode (17) arranged in parallel with said third SCR (16), and said third SCR arrangement (15) is arranged in said main line (2) with a polarity opposite to that of said first SCR arrangement (3), and said switching arrangement (1) comprises a second bypass line (18) connected to said main line (2) and arranged in parallel with said third SCR arrangement (15), and said second bypass line (18) comprises a fourth SCR arrangement (19), said fourth SCR arrangement comprising at least a fourth SCR (20) arranged with the same polarity as said third reverse conducting diode (17).

6. The switching arrangement (1) according to claim 5, characterized in that The second bypass line (18) is connected to the first bypass line (6), wherein the capacitor (9) is part of the first bypass line (6) and the second bypass line (18).

7. The switching arrangement (1) according to claim 5, characterized in that the first bypass line (6) further comprises at least one inductor (11) arranged in series with the capacitor (9), and the capacitor (9) and the inductor (11) form a resonant circuit (12), the second bypass line (18) is connected to the first bypass line (6), wherein the resonant circuit (12) is part of the first bypass line (6) and the second bypass line (18).

8. The switching arrangement (1) according to any one of claims 5 to 7, characterized in that the switching arrangement (1) comprises a control unit (14), the control unit is connected to the first SCR (4), the second SCR (8) and the DC voltage source (10), and for cutting off the switching arrangement (1), the control unit (14) first turns on the second SCR (8) and cuts off the first SCR (4), and the control unit (14) further cuts off the DC voltage source (10), the control unit (14) is connected to the third SCR (16) and the fourth SCR (20), and for cutting off the switching arrangement (1), the control unit (14) first turns on the second SCR (8) and the fourth SCR (20), and cuts off the first SCR (4) and the third SCR (16), and the control unit (14) further cuts off the DC voltage source (10).

9. The switching arrangement (1) according to claim 1, characterized in that the current is a short - circuit current.

10. A circuit breaker (21) having a switching arrangement (1) according to any one of claims 1 to 9.

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