CN109074980B - Bidirectional reversing promoter - Google Patents

Abstract

A circuit breaker is provided for interrupting the flow of current between the first node and the second node. The circuit breaker includes a first switch branch including a first winding of a transformer and a mechanical switch connected in series. The circuit breaker further includes a second switching branch including a second winding of the transformer and a switching device including at least one switching device connected to the second winding. The first switch branch and the second switch branch are connected in parallel between the first node and the second node, and the second switch branch is configured for bidirectional operation.

Description

Bidirectional Reversing Promoter

technical field

The present disclosure relates to the field of circuit breakers for DC power systems. In particular, the present disclosure relates to bidirectional circuit breakers for DC power systems.

Background technique

To convert between alternating current (AC) and direct current (DC), voltage source converters (VSCs) have been developed as an alternative to more traditional line-commutated converters. VSCs typically constructed using insulated gate bipolar transistors (IGBTs) and anti-parallel diodes may not be able to handle DC faults (such as faults between high impedance and ground, or faults in the converter itself). The anti-parallel diode may conduct as a rectifier bridge to feed a fault, or act as a short circuit with eg a faulty IGBT, for example. The diodes at the IGBTs may be bypassed and cannot eliminate the faulty circuit on their own. To solve this problem, fast and reliable DC circuit breakers with low losses need to be inserted.

Modern DC circuit breakers often rely on a combination of mechanical switches that complement parallel-coupled semiconductor switches. During normal operation, when the semiconductor switch is open, current flows through the closed mechanical switch. If a fault is detected, the switch is reconfigured so that the current is commutated (redirected) through the semiconductor switch, while the mechanical switch is allowed to open. Once the mechanical switch has been opened (and the current through the mechanical switch has been driven to zero), the semiconductor switch can be opened again and any remaining energy can be absorbed by, for example, a varistor.

A further development of such semiconductor-based DC circuit breakers is the commutation booster disclosed in, for example, US 9,148,011, in which inductive coupling between a branch containing a mechanical switch and a branch containing a semiconductor switch is used to enhance the commutation of the current. commutation.

As VSCs emerge in a wider range of low voltage (LV), medium voltage (MU) and high voltage (HV) systems, more flexible and efficient DC circuit breakers may be required.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present disclosure to at least partially satisfy the above requirements. This and other objects are achieved by means of a circuit breaker for interrupting the flow of current between the first node and the second node.

According to one aspect of the present disclosure, a circuit breaker may include a first switch branch including a first winding of a transformer and a mechanical switch connected in series. The circuit breaker may further include a second switching branch including a second winding of the transformer and a switching device including at least one switching device connected to the second winding. The first switch branch and the second switch branch may be connected in parallel between the first node and the second node, and the second switch branch may be configured to operate bidirectionally (ie, between the first node and the second node) in either direction).

In this aspect, the circuit can be commutated in any direction from the first switching device to the second switching device because the second switching device is configured for bidirectional operation. This can allow the fault circuit to be interrupted in any direction, ie, from both sides of the circuit breaker, and the circuit breaker can be used in systems where fault currents (and also load currents) may occur in different directions. Examples of such systems include energy storage systems using, for example, batteries and voltage source converters (VSCs), where load current is typically carried in different directions depending on whether the system is currently in the charging or discharging phase, And where fault currents can travel in different directions, eg through faulty semiconductors in a VSC.

By allowing both load current and fault current to have multiple directions, circuit breakers of the present aspect may be used in transportation systems where batteries and voltage source converters are located, for example, in fixed installations or on board vehicles or both, eg, as In electric vehicles (EVs) such as trams, trains, buses, hybrid vehicles, etc. Other systems in which circuit breakers may be used include power transmission systems and grids where current flow may change its direction depending on the location of a fault within the system, such as a multi-terminal DC grid.

In one embodiment of the present disclosure, the switching arrangement may be a bidirectional device (or bipolar device), ie a device that allows current to flow in either direction between the first node and the second node.

In one embodiment of the present disclosure, the at least one switching device may include, or may be, at least one of the following: Insulated Gate Bipolar Transistor (IGBT), Metal Oxide Semiconductor Field Effect Transistor (MOSFET), Field Effect Transistor (FET), gate turn off (GTO) thyristor or capacitor based device. It is also contemplated that the at least one semiconductor switching device may be any other power transistor or power thyristor suitable for handling sufficiently high currents and/or powers.

In one embodiment of the present disclosure, the switching device may comprise a diode bridge.

In one embodiment of the present disclosure, the switching device may include a first semiconductor switching device and a second semiconductor switching device. The first semiconductor switching device and the second semiconductor switching device may be unidirectional (or unipolar devices) and may be configured to operate in electrically opposite directions between the first node and the second node, ie, the first and second Two semiconductor switching devices may allow blocking current flow through them, or allow current flow through them in a single direction between the first node and the second node.

In one embodiment of the present disclosure, the first semiconductor switching device, the second semiconductor switching device, and the second winding are connected as a loop from the second node to the second node, and the first node is connected to the second switch through the second winding branch. In this or other embodiments, the second winding may be at least a bifilar winding.

In one embodiment, the second switching branch may include a first sub-branch and a second sub-branch, the first sub-branch including a second winding connected in series to the first semiconductor switching device, and the second sub-branch including The second semiconductor switching device and the third winding of the transformer are connected in series (connected to each other in series to form the second sub-branch). The first sub-branch and the second sub-branch may be connected in parallel.

In one embodiment of the present invention, the switching device may further include a first diode connected in series with the first semiconductor switching device, and a second diode connected in series with the second semiconductor switching device. The first diode and the first semiconductor switching device and the second diode and the second semiconductor switching device may be connected in anti-parallel (ie, the first diode and the first semiconductor switching device on the one hand and the first semiconductor switching device on the other hand) Two diodes and a second semiconductor switching device are connected in electrical opposite directions between the first node and the second node).

In one embodiment of the present disclosure, the first semiconductor switching device and the second semiconductor switching device are connected in anti-parallel.

In one embodiment of the present disclosure, the circuit breaker may further include an overvoltage protection circuit.

In one embodiment of the present disclosure, the circuit breaker may further include a third switch branch including an overvoltage protection circuit. The third switch branch may be connected in parallel with the first switch branch and the second switch branch between the first node and the second node. It is also conceivable that the third switching branch may be connected in parallel with the switching device, eg, with the switching device.

In one embodiment of the present disclosure, the self-inductance of the first switch branch may be greater than the self-inductance of the second switch branch.

In one embodiment of the present disclosure, the conductor cross-section of the first winding may be larger than the conductor cross-section of the second winding.

In one embodiment of the present disclosure, a high voltage DC power system may be provided, the high voltage DC power system comprising at least one circuit breaker according to any embodiment of the present disclosure.

In one embodiment of the present disclosure, an energy storage system may be provided that includes at least one circuit breaker according to any embodiment of the present disclosure.

The present disclosure relates to all possible combinations of the features mentioned herein, including the features listed above and other features that will be described below with reference to different embodiments. Any of the embodiments described herein may be combined with other embodiments described herein, and the present disclosure also relates to all such combinations.

Description of drawings

The above and other objects, features, advantages and applications of the circuit breaker of the present invention will be better understood from the following detailed description of the illustrative and non-limiting embodiments.

Referring to the attached drawings, in which:

1 is a schematic diagram of a circuit breaker according to one or more embodiments of the present disclosure;

2 is a schematic diagram of a circuit breaker in accordance with one or more embodiments of the present disclosure;

3 is a schematic diagram of a circuit breaker in accordance with one or more embodiments of the present disclosure;

4a-4d are schematic diagrams of switching devices and switching devices according to one or more embodiments of the present disclosure;

Figure 5a is a schematic diagram of a high voltage DC system; Figure 5b is a schematic diagram of a node of the high voltage DC system, wherein the node includes one or more circuit breakers according to one or more embodiments of the present disclosure;

6 is a schematic diagram of an energy storage system including one or more circuit breakers in accordance with one or more embodiments of the present disclosure; and

7 is a schematic diagram of an electrical traction/drive system in a battery powered electric vehicle that includes one or more circuit breakers in accordance with one or more embodiments of the present disclosure.

In the drawings, the same reference numerals will be used for the same elements unless otherwise stated. Unless expressly indicated to the contrary, the drawings show only elements necessary to illustrate example embodiments, while other elements may be omitted or merely suggested for the sake of clarity.

Detailed ways

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings. The drawings illustrate presently preferred embodiments, however, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; and fully convey the scope of the invention to those skilled in the art.

Some embodiments of circuit breakers according to the present disclosure will now be described primarily with reference to FIGS. 1 , 2 and 3 .

FIG. 1 shows a circuit breaker 100 that can interrupt current flowing between a first node 102 and a second node 104 . The circuit breaker 100 includes a first switch branch 110 , and the first switch branch 110 includes a first winding 120 of a transformer and a mechanical switch 130 . The first winding 120 and the mechanical switch 130 are connected in series, and during normal operation (ie, when the circuit breaker 100 is not activated), current flows from the first node 102 through the first switch branch 110 to the second node 104 (or , depending on the direction of current flow, from the second node 140 to the first node 102). The first winding 120 may be on either side of the mechanical switch 130 .

The circuit breaker 100 further includes a second switching branch 112 including the second winding 122 of the transformer and a switching device including at least one switching device 140 . The second winding 122 may be on either side of the switching device and the at least one switching device 140 . During normal operation, the switching device is open (ie, for example, by keeping the at least one switching device 140 open or in a current blocking state, the switching device does not allow current to flow therethrough), and therefore no (or very little) current flows through the first switching device 140. Two switch branches 122 flow. The first switching branch 110 and the second switching branch 122 are connected in parallel between the first node 102 and the second node 104 .

Wherein the term "mutual" inductor refers to an inductor shared between the first switching branch and the second switching branch or shared by the first switching branch and the second switching branch. In this embodiment, the first winding and the second winding of the first switching branch and the second switching branch, respectively, together form a transformer. In these embodiments, the first winding and the second winding are arranged, or spaced apart, such that they can interact magnetically. In the figures, the inductor dot designation (which is based on the dotconvention of the same name) has been intentionally omitted. In eg FIG. 1 , winding 120 and winding 122 may be arranged such that the points of these windings (if they are included in the figure), for example, would appear on the same side of winding 120 and winding 122 (eg, both points on the left, or both points on the right).

The second switch branch 112 is configured for bidirectional operation. Wherein the term "bidirectionally" here means that when the switching device comprising the at least one switching device 140 is closed, current is allowed to flow through the second switching branch 112 in both directions. In other words, current may flow from the first node 102 through the second switching branch 112 to the second node 104 , and/or from the second node 104 through the second switching branch 112 to the first node 102 . This may be beneficial when the load current (ie, the current flowing through the circuit breaker 100 during normal operation) and the fault current, for example, may have opposite directions. Therefore, the circuit breaker 100 may be more flexible and capable of interrupting current flow independently of the electrical direction of the current flow. This may allow the circuit breaker 100 to also be used in DC systems where the current may occasionally change direction (such as in an energy storage system where, for example, the battery may first provide energy to the load, ie discharge itself, and then utilize the resulting load current reversal to recharge). The circuit breaker 100 can be used, for example, in systems where the DC current can have multiple directions, while the polarity of the DC voltage remains unchanged.

If a fault is detected, eg, by detecting an abnormal increase in load current, the circuit breaker 100 may be activated by allowing current to flow through the switching device (eg, by closing at least one semiconductor switching device 140 and placing it in a non-current blocking state) . This may initiate commutation (redirection) of current from the first switching branch 110 to the second switching branch 112 . Due to its physical properties, the transformer can "resist" (ie, oppose and/or react) to any change in the sum of the currents through the first switching branch 110 and the second switching branch 112 . As the increased amount of current passes through the second switching branch 112, the transformer can help to further reduce the amount of current passing through the first switching branch 110, eventually forcing the magnitude of this current to go to zero (or, at least, decrease significantly) at some point. magnitude of current). For this purpose, the self-inductance of the first switching branch 110 may be greater than the self-inductance of the second switching branch 112 . This may be achieved, for example, when the self-inductance of the first winding 120 is greater than the self-inductance of the second winding 122 . At this point when the magnitude of the current through the first switch branch 110 becomes zero, the mechanical switch 130 can be operated with less effort and with a reduced risk of electrical breakdown (or arcing) across the gap of the mechanical switch 130 and was opened. The physical requirements on the mechanical switch 130 can be reduced, which can allow, for example, to reduce production costs.

When the second switch branch 112 is configured for bidirectional operation, the circuit breaker is no longer limited to interrupting current flow in a particular electrical direction, and the circuit breaker 100 may also be used to interrupt systems where this may occur (eg, in energy storage systems, or, for example, in multi-terminal HVDC systems or similar systems). In other circuit breakers where the commutating branch (eg, the second switching branch 112 ) is not configured for bidirectional operation (such as in circuit breakers where, for example, the switching devices are asymmetrical with respect to the direction of current flow), this flexible , direction independent current interruption will not be possible.

In some embodiments of the circuit breaker 100, the switching device may be bidirectional by using, for example, a semiconductor switching device (eg, an IGBT or any other type of transistor or eg a thyristor) together with additional components. An example of such a bidirectional device 420 is shown in Figure 4c, where four diodes 424, 425, 426 and 427 are arranged with a semiconductor switching device 422 in a diode bridge configuration. When semiconductor switching device 422 is turned on (or "off", eg, in a current blocking state), no current can pass from one side to the other (eg, from left to right). When semiconductor switching device 422 is closed (or "on", eg, in a non-current blocking state), current may pass from left to right via diode 424 , switching device 422 and diode 425 . Likewise, current may pass from right to left via diode 426, switching device 422, and diode 427, making switching device 420 bidirectional.

In some embodiments of a circuit breaker (eg, circuit breaker 100 ), the switching device may include more than one switching device, eg, a first semiconductor switching device and a second semiconductor switching device, wherein the first and second semiconductor switching devices are Unidirectional (or, unipolar device). Even if the first and second semiconductor switching devices are unidirectional, the switching arrangement can be made bidirectional, eg by arranging the first and second semiconductor switching devices between the first node 102 and the second node 104 Operates in the opposite direction of electricity.

An example of such a switching arrangement 400 is shown in FIG. 4 a , where a first semiconductor switching device 402 is connected in series with a first diode 408 , and where a second semiconductor switching device 404 is connected in series with a second diode 406 . The first semiconductor switching device 402 and the first diode 408 are connected in antiparallel with the second semiconductor switching device 404 and the second diode 406 . When both semiconductor switching devices 402 and 404 are turned on, no current can flow, eg, from left to right, due to diodes 406 and 408 . When the first semiconductor switching device 402 is closed, current may flow from left to right via the first switching device 402 and the first diode 408 . When the second semiconductor switching device 404 is turned on, current can flow from right to left via the second switching device 404 and the second diode 406, making the switching device 400 bidirectional.

A second example of such a bidirectional switching arrangement 410 is shown in Figure 4b, where a first semiconductor switching device 412 and a second semiconductor switching device 414 are connected in anti-parallel. When both switching devices 412 and 414 are turned on, no current can flow, eg, from left to right. If the first semiconductor switching device 412 is closed, current can flow from left to right. If the second semiconductor switching device 414 is closed, current can flow from right to left, and the switching device 410 can be bidirectional.

FIG. 2 shows another embodiment of a circuit breaker 200 . For circuit breaker 100, circuit breaker 200 includes a first switch branch 210 including a first winding 220 of a transformer and a mechanical switch 230 connected in series. The first winding 220 may be on either side of the mechanical switch 230 . A circuit breaker is connected between the first node 202 and the second node 204 . The second switching branch 212 is connected in parallel with the first switching branch 210 between the node 202 and the node 204, and the second switching branch 212 in this embodiment includes a first set 214 of electrical components and a second set of electrical components Group 216.

The first group 214 includes the second winding 222 of the transformer and the first semiconductor switching device 242 . The second winding 222 may be on either side of the first semiconductor switching device 242 . The second group 216 includes the second semiconductor switching devices 244 . In this embodiment, the first semiconductor switching device 242 and the second semiconductor switching device 244 of the switching device may be unidirectional. The two switching devices 242 and 244 and the second winding are connected from the second node 204 to the second node 204 as a loop (ie, a closed circuit). The first node 202 may be connected to the second switching branch 212 through a tap to the second winding 250 of the first set 214 . The first and second switching devices are arranged in anti-parallel in this arrangement so that current can pass through the first sub-branch 214 in a first direction and through the second sub-branch 216 in a second direction opposite the first direction. An example of a unidirectional semiconductor switching device 430 is shown in Figure 4d, where, for example, transistor 432 allows current to flow from left to right when it is turned on, and otherwise blocks current flow from left to right or right to left, makes the device unidirectional.

In the circuit breaker 200 in FIG. 2, the first group 214 and the second group 216 can be considered to be connected in parallel, with the second switch branch 212 being connected to the tap 250 going to the second winding 222 of the transformer node 202. When at least one of semiconductor switching device 242 and semiconductor switching device 244 is turned on (ie, closed) after a fault is detected, current will be commutated from first switching branch 210 to second switching branch 212 and through The second winding 222 . As described earlier, the ability of the transformer to "resist" any change in the sum of the currents through the first and second switching branches will by forcing the current through the first switching branch 210 to be zero at some point in time , to relieve the subsequent closing of the mechanical switch 230 .

By using two subsets 214 and 216 through which current can pass in different directions, unidirectional semiconductor switching devices 242 and 244 can be used without additional components in the switching arrangement, such as diodes connected in parallel or in series. This may reduce, for example, power losses associated with the otherwise use of such diodes and/or other additional components, and/or reduce, for example, the number and cost of components required.

Another embodiment of a circuit breaker 300 is shown in FIG. 3 . For circuit breakers 100 and 200, circuit breaker 300 includes a first switch branch 310 including a first winding 320 of a transformer and a mechanical switch 330 connected in series. The circuit breaker 300 is connected between the first node 302 and the second node 304 . The circuit breaker 300 further includes a second switch branch 312 , which in turn includes a first sub-branch 314 and a second sub-branch 316 . The first sub-branch 314 includes the second winding 322 of the transformer and the first semiconductor switching device 342 connected (series) together, and the second sub-branch 316 includes the second semiconductor switching device 344 .

The second sub-branch 316 includes the third winding 324 of the transformer, which is connected (in series) to the second semiconductor switching device 344 . The first and second sub-branches are connected in parallel to form a second switch branch 312 , and the second switch branch 312 is connected in parallel with the first switch branch 310 between nodes 302 and 304 . When the third winding 324 is used, no taps to any winding are required to connect the second switching branch 312 to the first switching branch 310 in this embodiment. However, if, for example, the combined length (number of turns, eg, inductance) of the second winding 322 and the third winding 324 matches the combined length of the second winding 222 in the circuit breaker 200, and the tap 250 is located in the middle of the second winding 222, it is possible to It is contemplated that the embodiment of circuit breaker 300 is functionally equivalent to the embodiment of circuit breaker 200 .

Circuit breakers 100, 200, 300 according to the present disclosure may also include overvoltage protection circuits, such as snubbers (eg, varistors, RC snubbers, RCD snubbers, or capacitors). The overvoltage protection circuit may be included in a third switch branch connected in parallel with the first and second switch branches (between the first node and the second node). The third switching branch may also not be connected in parallel with the entire first and/or second switching branch, but only with eg switching devices (such as switching device 140 in FIG. 1 ) or switching devices (such as in FIG. 2 ) The switching devices 242, 244 and any one of 324, 344 in FIG. 3) are connected in parallel. It is also envisaged that the third switching branch may comprise an additional winding of the transformer and that this additional winding is connected in series with eg an overvoltage protection circuit. For example, the current can be commutated to the third switching branch also by opening the switching device and dissipated by the overvoltage protection circuit.

With a "switching device," any device that can be used to selectively block current flow through it is envisioned. Examples of such devices, preferably adapted to handle high current and/or high power, may include various semiconductor switching devices such as transistors (eg, IBGTs, FETs, MOSFETs) and various thyristors (eg, gate off off the GTO thyristor). The switching device may also include a capacitor.

In Figures 1 to 3, the mutual inductance between the windings/coils is shown with two parallel lines. Inductors can be made with air core coils only, with magnetic flux-carrying magnetic materials (with relative permeability greater than 1), or with a combination thereof.

Winding 122, 222, 322 or 324 is normally unloaded (ie, it does not carry current) and is only active during periods when the switching device is handling the fault. During this period, the normally unloaded windings cause temporary losses and it may be acceptable to experience an adiabatic temperature rise. In addition to the increase in the adiabatic temperature, the cross-sectional area of the conductors of the normally unloaded winding can thus be reduced. The cross-sectional area of conductors in normally active windings (such as windings 120, 220, and 320) may be increased (eg, by redistributing material such as copper from normally unloaded windings to normally active windings). The normally active winding can thus carry current with reduced usual conduction losses, which can lead to increased efficiency of the circuit breaker. As an example, the cross-sectional area of a normally active winding may be 10-30 (or more) times the cross-sectional area of a normally unloaded winding.

It is contemplated that circuit breakers according to the present disclosure may be included in various types of systems, and particularly systems in which VSCs are present. Examples of such systems may be energy storage systems, data centers, transportation systems such as electric vehicles, EVs, and HVDC power transmission systems. Circuit breakers can be used in DC systems with many terminals (internal terminals or terminals for connection to an AC system). An example of such a system may be, for example, a wind farm, where the generated AC power from the wind turbines is converted to DC power before being transmitted away on the DC grid. Other systems include electric buses, trams, and trains, where AC motors are driven by DC power (such as, for example, by batteries). In particular, circuit breakers according to any of the embodiments of the present disclosure may be used in DC systems where load currents and fault currents may be located at locations within the system (ie, in situations where conventional or recently disclosed DC circuit breakers may not be flexible enough ) flow in different directions.

In Figure 5a, a multi-terminal HVDC system 500 is shown. The system 500 has three nodes 510 , 512 and 514 connected to each other in a delta fashion via DC power lines 520 , 522 and 524 . At each node, a voltage source converter (VSC) connects the corresponding node to the external AC system. The external AC system may be, for example, a fan, a water turbine, or any other electrical device or electrical system that consumes or generates AC power. If a fault occurs on the DC side of the system 500, it is preferable if the fault can be quickly detected and isolated so that the system 500 can be returned to its normal operating state as quickly as possible.

In Figure 5b, the first node 510 of the multi-terminal HVDC 500 is shown in more detail. To convert between AC and DC, node 510 includes a VSC circuit 540 formed at least in part by IGBTs coupled in anti-parallel with respective freewheeling diodes. If a fault occurs on the DC side of the system 500, the IGBTs of the VSC may not be able to block the fault current. Rather, the freewheeling diode can act as a bridge rectifier and continue to feed the fault. To at least partially address this problem, the node 510 is equipped with circuit breakers 560 and 562 according to one or more of the embodiments described above, the circuit breakers 560 and 562 being positioned at the terminals of the VSC circuit . Additional circuit breakers 564, 565, 566 and 567 are also positioned at the ends of DC power lines 520 (including two wires 520a and 520b) and 524 (including two wires 524a and 524b). In some embodiments, only circuit breakers 560 and 562 may be required, while in some embodiments, only additional circuit breakers 564, 565, 566, and 567 may be required. Node 510 is also equipped with DC switches 570 , 571 , 572 and 573 which are positioned on corresponding lines of power lines 520 and 524 .

If a DC fault is detected, such as when the current is confirmed to exceed a predetermined threshold, the corresponding circuit breaker may be activated to interrupt the current as previously described herein. Once the current is interrupted, the corresponding DC switch can be opened and the faulty line can be isolated. Because one or more circuit breakers according to the present disclosure do not require current to pass through any switching devices (such as semiconductor switching devices) during normal operation, protection against overcurrent, eg in HVDC systems, can be achieved while reducing losses and Increased cost-effectiveness and robustness.

Conventional alternatives, such as systems using IGBT circuit breakers instead of circuit breakers according to the present disclosure, would require the semiconductor switches to also carry current during normal operation, and would therefore be expected to have higher losses. In addition, such conventional circuit breakers would also not be able to interrupt current flow in either direction. The IGBT circuit breaker is a unidirectional device and the current flowing in the direction of the freewheeling diode will not be interrupted. Such fault currents may be caused, for example, by faults occurring on the converter side of the node, and interruption of such currents may have to rely on IGBTs in the converter itself.

In Figure 6, a medium voltage (MV) energy storage system 600 is shown with a plurality of batteries 620 and 622 connected to AC line 610 via a voltage source converter (VSC). Only a single phase of the AC line 610 is shown, and it is envisaged that similar arrangements may exist for other phases. In energy storage system 600 , each battery is connected to line 610 via a cascaded H-bridge inverter 630 and DC-DC chopper circuit 640 . .

As previously mentioned, the VSC itself is susceptible to DC faults and normal current control may be aborted, especially since current in the system 600 may flow in different directions depending on whether the battery is being discharged or charged. Furthermore, fault currents may enter the interior through faulty semiconductors in the VSC. To at least partially address this problem and provide protection against DC current faults in system 600, circuit breakers 660, 662, and 624 in accordance with one or more embodiments of the present disclosure are inserted. It is envisaged that more or fewer circuit breakers may be required. In Figure 6, circuit breakers 660 and 662 are inserted between the respective batteries 620 and 622 and a DC-DC chopper circuit (such as circuit 640), while circuit breaker 624 is inserted between the cascaded batteries and inverters Between the stack of circuits and the AC line 610 . Because these circuit breakers are capable of isolating fault currents flowing in multiple directions, the circuit breakers can also provide protection in systems like energy storage system 600, while reducing current due to no semiconductor devices in the circuit breakers during normal operation loss.

In FIG. 7, a low voltage (LV) electrical traction/drive system 700 in a battery powered electric vehicle (EV) is shown. System 700 includes a battery 720 coupled to an AC electric motor 730 via an inverter circuit 710 including a plurality of IGBTs and anti-parallel coupled diodes. Battery 720 may be charged using suitable charging techniques, shown schematically by charging connections 750 and 752 . Charging may be provided as DC (using eg charging connection 750 , preferably provided with protection according to the present disclosure) or as AC (using eg charging connection 752 ). Current (such as normal current or fault current) may flow in multiple directions depending on whether the battery 720 is being discharged (eg, while the vehicle is running) or is being charged. Circuit breakers 760, 762, 764, and 766 in accordance with one or more of the previously described embodiments of the present disclosure are inserted to provide protection against DC faults in system 700 (independent of direction of current flow and with reduced losses ). In FIG. 7 , circuit breaker 760 is inserted between inverter circuit 710 and battery 720 , while circuit breakers 762 , 764 and 766 are inserted on corresponding phases between inverter circuit 710 and AC motor 730 . It is contemplated that fewer or more circuit breakers could be used if desired.

Other traction/drive systems in which circuit breakers according to one or more embodiments of the present disclosure may be used include various transmission systems such as, for example, trains, trams, and electric buses. In such systems, batteries are not necessarily required, and power may be received from, for example, external conductors (such as overhead lines or a third rail). Other examples may be, for example, a hybrid vehicle, where the battery is charged using an internal combustion engine, and where the current flow may depend on whether the battery is being charged or recharged.

Although features and elements are described above in specific combinations, each feature or element can be used alone without the other features and elements, or in various combinations with other features and elements, or without other Features and elements are used in various combinations.

In addition, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Claims (9)

1. A circuit breaker for interrupting a flow of current between a first node and a second node, comprising:

a first switching leg comprising a mechanical switch and a first winding of a transformer connected in series; and

a second switching leg comprising a second winding of the transformer and a switching device,

wherein the first switching leg and the second switching leg are connected in parallel between the first node and the second node, and wherein the second switching leg is configured to operate bi-directionally,

wherein the switching arrangement comprises a first semiconductor switching device and a second semiconductor switching device, wherein the first semiconductor switching device and the second semiconductor switching device are unidirectional and are configured to operate in electrically opposite directions between the first node and the second node, an

Wherein the first semiconductor switching device, the second semiconductor switching device and the second winding are connected as a loop from the second node to the second node, the first node is connected to the second switching branch through the second winding, or

Wherein the second switching leg comprises a first sub-leg and a second sub-leg, the first sub-leg comprising the second winding connected in series to the first semiconductor switching device, the second sub-leg comprising the second semiconductor switching device and a third winding of the transformer connected in series, wherein the first sub-leg and the second sub-leg are connected in parallel.

2. The circuit breaker of claim 1, wherein when the first semiconductor switching device, the second semiconductor switching device, and the second winding are connected as a loop from the second node to the second node, and the first node is connected to the second switching leg through the second winding, the second winding is at least a bifilar winding.

3. The circuit breaker of claim 1 or 2, wherein the first semiconductor switching device is connected in anti-parallel with the second semiconductor switching device.

4. The circuit breaker of claim 1 or 2, further comprising an overvoltage protection circuit.

5. The circuit breaker of claim 4, further comprising a third switching leg including the overvoltage protection circuit, wherein the third switching leg is connected in parallel with the first and second switching legs between the first and second nodes.

6. The circuit breaker of any of claims 1, 2, and 5, wherein the self-inductance of the first switching leg is greater than the self-inductance of the second switching leg.

7. The circuit breaker of any of claims 1, 2, and 5, wherein a conductor cross-section of the first winding is larger than a conductor cross-section of the second winding.

8. A high voltage direct current power system comprising at least one circuit breaker according to any of the preceding claims.

9. An energy storage system comprising at least one circuit breaker according to any one of claims 1 to 7.

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