Switching device for DC electrical network

Abstract

The invention relates to a switching device for a DC power grid. A switching device for a DC electrical network, comprising: first and second electrical terminals for electrical connection with corresponding conductors of an electrical wire; a primary switching arrangement comprising one or more primary switching devices configured to conduct or block a current along a conductive path between the first and second electrical terminals; a control stage comprising a control unit configured to control one or more controllable components of the switchgear; a power supply stage electrically connected to the control stage to feed power drawn from the wire to the control stage; and a secondary switching device comprising one or more secondary switching devices controllable by the control stage. The secondary switching device is configured to electrically connect the power stage with the first electrical terminal or the second electrical terminal as needed.

Description

Technical Field

[0001] This invention relates to the field of power grids. More specifically, this invention relates to a switching device for DC power grids. Background Technology

[0002] DC power grids are widely used in various applications, such as photovoltaic systems, naval systems, and energy storage systems using batteries-based energy storage systems (BESS).

[0003] As is known, when a fault event (such as an overload or short circuit) occurs in a DC power line, many electrical components electrically connected to the line can feed this electrical fault. This can obviously lead to catastrophic consequences, especially when power generation systems (such as photovoltaic panels) or energy storage systems (such as batteries) are installed in the power grid.

[0004] To prevent these undesirable events, DC power grids typically include switching devices to allow for the selective disconnection of portions of the grid in the event of a fault.

[0005] Some existing switching devices include electromechanical circuit breakers. Typically, these switching devices have the advantage of ensuring current isolation between disconnected parts of the power grid. Furthermore, they are relatively inexpensive to implement at the industrial level.

[0006] However, many existing switching devices include solid-state switching devices, which include switches based on semiconductor materials. The main advantage of these switching devices is that they potentially have unlimited electrical durability due to their arc-free switching operation. Furthermore, they operate quickly and have significantly shorter downtime compared to electromechanical switching devices.

[0007] Many switching devices used in DC power grids, especially those including solid-state switching devices, are equipped with control units to control the operation of controllable components mounted on a board, such as the aforementioned semiconductor-based switches.

[0008] Typically, the control unit is "self-powered," meaning that the switching device includes a power stage configured to feed the control stage by drawing power directly from the wires on which the control unit is mounted.

[0009] Typically, such a power stage is electrically connected to the power supply side of the wire in such a way that the control stage can be fed even when the switching device is still in the off state and no current flows along the wire ("black start"), as long as the wire is powered.

[0010] Existing switchgear using self-powered control stages has several areas for improvement.

[0011] Experience has shown how power supply stages typically experience inrush currents during the disconnection operation of switching devices. These undesirable events occur when the input capacitors of the power supply stage essentially act as short circuits during the initial phase of disconnection.

[0012] Therefore, the power supply stage (especially its input capacitors) must be of appropriate size to withstand these high-energy phenomena and avoid damage to the input capacitors. This obviously requires relatively high industrial costs to manufacture industrial-grade power supplies. Furthermore, the large arrangement of input capacitors in the power supply stage can significantly limit the current-breaking performance of the switching devices used to interrupt the current flowing along the wires. Summary of the Invention

[0013] The main objective of this invention is to provide a switching device for DC power grids that allows for overcoming or mitigating the aforementioned critical issues.

[0014] More specifically, the object of the present invention is to provide a switching device in which a power stage that is cheaper and smaller in size, and may include lower input capacitance, can be used compared to corresponding solutions in the prior art.

[0015] Another object of the present invention is to provide a switching device, particularly a switching device with interrupted rated values ​​in the event of an electrical fault, such as in the presence of a short circuit.

[0016] Another object of the present invention is to provide a switching device that can be easily manufactured at an industrial level at a competitive cost, compared to existing solutions.

[0017] To achieve these objectives and purposes, the present invention provides a switching device according to claim 1 and related dependent claims.

[0018] The switching device according to the present invention includes:

[0019] The first and second electrical terminals are used for electrical connection with the corresponding conductors of the wire;

[0020] A primary switching device includes one or more primary switching devices. The primary switching devices are configured to reversibly switch between an on state and a blocking state, wherein in the on state, the primary switching device conducts current along a conductive path between the first and second electrical terminals, and in the blocking state, the primary switching device blocks the current between the first and second electrical terminals.

[0021] A control level, which includes a control unit configured to control one or more controllable components of the switching device;

[0022] A power supply stage, electrically connected to the control stage, supplies power drawn from the wires to the control stage.

[0023] According to the present invention, the switching device includes a secondary switching device, which includes one or more secondary switching elements controllable by the control unit.

[0024] The secondary switching device is configured to reversibly switch between a first switching state and a second switching state. In the first switching state, the secondary switching device electrically connects the first electrical terminal to the power stage and electrically disconnects the second electrical terminal from the power stage. In the second switching state, the secondary switching device electrically disconnects the first electrical terminal from the power stage and electrically connects the second electrical terminal to the power stage.

[0025] According to one aspect of the invention, the control unit is configured to command the secondary switching device to operate based on the operating state of the switching device.

[0026] Preferably, the control unit is configured as follows:

[0027] If the first electrical terminal is electrically connected to the power supply portion of the wire, and the second electrical terminal is electrically connected to the load portion of the wire, then:

[0028] When the switching device is in the off state, the secondary switching device is commanded to operate in the first switching state; and

[0029] When the switching device is in the closed state, the secondary switching device is commanded to operate in the second switching state.

[0030] Preferably, the control unit is configured as follows:

[0031] If the first electrical terminal is electrically connected to the load portion of the wire, and the second electrical terminal is electrically connected to the power supply portion of the wire, then:

[0032] When the switching device is in the off state, the secondary switching device is commanded to operate in the second switching state;

[0033] When the switching device is in the closed state, the secondary switching device is commanded to operate in the first switching state.

[0034] According to one aspect of the invention, the control unit is configured to command the secondary switching device to reversibly switch between a first switching state and a second switching state during the opening or closing operation of the switching device.

[0035] Preferably, the control unit is configured to command the secondary switching device:

[0036] If the first electrical terminal is electrically connected to the power supply portion of the wire, and the second electrical terminal is electrically connected to the load portion of the wire, then:

[0037] Before the primary switching device performs a switching change corresponding to the closing operation, it switches from the first switching state to the second switching state;

[0038] When the primary switching device has completed the switching change corresponding to the disconnection operation, it switches back from the second switching state to the first switching state.

[0039] Preferably, the control unit is configured to command the secondary switching device:

[0040] If the first electrical terminal is electrically connected to the load portion of the wire, and the second electrical terminal is electrically connected to the power supply portion of the wire, then:

[0041] The primary switching device switches from the second switching state to the first switching state before performing a switching change corresponding to the closing operation;

[0042] When the primary switching device has completed the switching change corresponding to the disconnection operation, it switches back from the first switching state to the second switching state.

[0043] According to some embodiments of the present invention, the primary switching device of the switching device is a solid-state type switching device, and each includes one or more switches based on semiconductor materials.

[0044] According to some embodiments of the present invention, the primary switching device is an electromechanical switching device.

[0045] According to some embodiments of the present invention, the secondary switching device is an electromechanical switching device.

[0046] According to some embodiments of the present invention, the secondary switching devices are solid-state type switching devices, and each includes one or more switches based on semiconductor materials.

[0047] According to some embodiments of the present invention, the secondary switching device is a hybrid switching device. In this case, each secondary switching device includes one or more semiconductor-based switches and one or more electromechanical switches. Attached Figure Description

[0048] Other features and advantages of the invention will become apparent from the description of preferred, but not exclusive, embodiments of the switching device according to the invention, non-limiting examples of which are provided in the accompanying drawings, wherein:

[0049] Figure 1A schematic diagram illustrates a wire including a switching device according to the invention;

[0050] Figure 2 - Figure 3 Different embodiments of the switching device according to the present invention are illustrated schematically;

[0051] Figure 3A - Figure 3B The switching device according to the invention is illustrated schematically under different operating conditions;

[0052] Figure 4A - Figure 4B The primary switching device of the switching device according to different embodiments of the present invention is schematically shown;

[0053] Figure 5 - Figure 8 Some control logic implemented by the control unit of the switching device according to the present invention is illustrated schematically. Detailed Implementation

[0054] Referring to the accompanying drawings, the present invention relates to a switching device 1 for a DC power grid.

[0055] The switching device of the present invention is particularly suitable for low-voltage DC power grids, and for the sake of brevity, it will be described below with reference to these applications, without intending to limit the scope of the invention in any way. In fact, the switching device of the present invention can be successfully used in different types of electrical systems, such as medium-voltage DC power grids.

[0056] For illustrative purposes, the term “low voltage” (LV) generally refers to operating voltages below 1.5 kV AC and 2.0 kV DC, while the term “medium voltage” (MV) generally refers to higher operating voltages up to tens of kV, such as up to 72 kV AC and 100 kV DC.

[0057] The switching device 1 includes first and second electrical terminals 11, 12 for electrical connection with corresponding conductors of wire 100, which is advantageously used for electrical connection to first and second grid sections 101, 102 of a power grid.

[0058] When the switchgear is installed in the field, the first and second electrical terminals 11 and 12 are electrically connected to the first and second power grid sections 101 and 102 respectively via corresponding portions of the wire 100.

[0059] In operation, the electrical power flow along the wire 100 can be directed from the first grid section 101 to the second grid section 102. In this case, the first and second electrical terminals 11 and 12 are electrically connected to the power supply section and the load section of the wire 100, respectively.

[0060] Alternatively, the electrical power flow along wire 100 can be directed from the second grid section 102 to the first grid section 101. In this case, the first and second electrical terminals 11 and 12 are electrically connected to the load section and the power supply section of wire 100, respectively.

[0061] As an alternative, the electrical power flow along wire 100 can be bidirectional, as its direction depends on the instantaneous operating conditions of the power grid. This may occur, for example, when both grid sections 101 and 102 include power generation systems (e.g., photovoltaic panels) and / or energy storage systems (e.g., batteries). In this case, depending on the ongoing operating conditions of the power grid, the first and second electrical terminals 11 and 12 can be electrically connected alternately to the load and power supply sections of wire 100.

[0062] In the accompanying drawings, the switching device 1 includes a pair of first electrical terminals 11 and a pair of second electrical terminals 12. However, in other cases, the first electrical terminals 11 and the second electrical terminals 12 may include a different number of terminals, such as three terminals.

[0063] Furthermore, in the cited figures, the switching device 1 includes a first electrical terminal 11 and a second electrical terminal 12, which have a floating voltage compared to ground (level). However, in some cases, one of the first electrical terminals 11 or one of the second electrical terminals 12 may be directly grounded. In other cases, one of the first electrical terminals 11 and / or one of the second electrical terminals 12 may be electrically connected to ground, for example, via a resistor. According to another alternative, a grounding arrangement via a capacitor or diode network may be employed.

[0064] The switching device 1 is configured to allow or interrupt the flow of current along the wire 100. For this purpose, the switching device 1 includes one or more primary switching devices 3.

[0065] The primary switching device 3 is configured to reversibly switch between an on state and an off state. In the on state, the primary switching device 3 conducts current along the conductive path between the first electrical terminal 11 and the second electrical terminal 12. In the off state, the primary switching device 3 blocks the current flowing along the conductive path between the first electrical terminal 11 and the second electrical terminal 12.

[0066] The primary switching device 3 can reversibly switch between the aforementioned blocking and conducting states when it receives an appropriate input control signal.

[0067] When the primary switching device 3 is in the on state, it causes the switching device 1 to be in the closed state A, in which current is allowed to flow along the wire 100.

[0068] When the primary switching device 3 is in the blocking state, it causes the switching device 1 to be in the open state B, in which it blocks the current along the wire 100.

[0069] The transition of the primary switching device 3 from the on state to the off state constitutes the disconnection operation of the switching device, while the transition of the primary switching device 3 from the off state to the on state constitutes the closing operation of the switching device.

[0070] According to some embodiments of the present invention ( Figure 4A The primary switching device 3 is of the solid-state type. Therefore, they include one or more switches 30 based on semiconductor materials.

[0071] Typically, the semiconductor switch 30 can be a conventional type of semiconductor switch, such as a power MOSFET, JFET, insulated gate bipolar transistor (“IGBT”), gate turn-off thyristor (GTO), integrated gate commutated thyristor (“IGCT”), etc.

[0072] When a suitable input control signal is received, each semiconductor switch 30 can reversibly switch between an on state and an off state. In the on state, the semiconductor switch 30 conducts current, and in the off state, the semiconductor switch 30 blocks current.

[0073] Each semiconductor switch 30 is turned off when switching from the ON state to the OFF state, and turned on when switching from the OFF state to the ON state.

[0074] Preferably, each primary switching device 3 includes at least one pair of semiconductor switches 30 arranged in an anti-parallel or anti-series configuration to allow control of bidirectional current flowing along the conductive path between the first and second electrical terminals 11, 12.

[0075] Preferably, each primary switching device 3 includes a protection circuit 32 electrically connected in parallel with one or more semiconductor switches 30. Such a protection circuit is configured to protect the associated semiconductor switch (e.g., by limiting voltage transients) when the associated semiconductor switch is turned off during the disconnection operation of the switching device and / or dissipate electrical energy when necessary.

[0076] The protection circuit 32 may advantageously include one or more metal oxide rheostats, snubbers, spark gaps, discharge tubes, etc.

[0077] Preferably, each primary switching device 3 includes an electromechanical switch 31 that is electrically connected in series with a semiconductor-based switch 30.

[0078] The electromechanical switch 31 has one or more fixed contacts and one or more movable contacts. The latter may be coupled or uncoupled to the fixed contacts to conduct or block current.

[0079] The electromechanical switch 31 is in a closed state when its electrical contacts are coupled to conduct current, and in an open state when its electrical contacts are not coupled to block current.

[0080] The electromechanical switch 31 can be self-acting. In this case, the transition from a closed state to an open state occurs by using the electrodynamic force generated by the current circulation to move the movable contact or to trip the movement of the movable contact. Conversely, the reverse transition from an open state to a closed state can occur upon receiving an appropriate input control signal that triggers the actuation of a drive mechanism that moves the movable contact or trips the movement of the movable contact.

[0081] As an alternative, the electromechanical switch 31 can be of a fully controllable type. In this case, in response to receiving an appropriate input control signal, any reversible transition between a closed and open state occurs, the input control signal causing the activation of the drive mechanism to move the movable contact or causing the movement of the movable contact to trip.

[0082] As described above, the primary switching device 3 is configured to reversibly switch between an on state and an off state. In the on state, the primary switching device 3 conducts current along the conductive path between the first electrical terminal 11 and the second electrical terminal 12. In the off state, the primary switching device 3 blocks the current flowing along the conductive path between the first electrical terminal 11 and the second electrical terminal 12.

[0083] When one or more semiconductor switches 30 (and possibly electromechanical switches 31) operate in a manner that allows current to flow between the first and second electrical terminals 11, 12, the primary switching device 3 is in a conducting state, and when one or more semiconductor switches 30 (and possibly electromechanical switches 31) operate in a manner that blocks current from flowing between the first and second electrical terminals 11, 12, the primary switching device 3 is in a blocking state.

[0084] Other embodiments of the present invention ( Figure 4B The primary switching device 3 is electromechanical.

[0085] Each electromechanical switching device 3 has one or more fixed contacts and one or more movable contacts, the movable contacts being able to couple to or disconnect from the fixed contacts to conduct or block current.

[0086] Each switching device 3 is in a closed state (corresponding to the conducting state of the switching device) when its electrical contacts are coupled to each other to conduct current, and in an open state (corresponding to the blocking state of the switching device) when its electrical contacts are decoupled to each other to block current.

[0087] Advantageously, each electromechanical switching device 3 is of a controllable type. In this case, in response to receiving an appropriate input control signal that causes any reversible transition between a closed and open state, the input control signal causes the activation of the drive mechanism to move the movable contact or causes the movement of the movable contact to trip.

[0088] Typically, the primary switching device 3 of a switching device can be implemented at the industrial level based on known types of solutions. Therefore, they will be described below only with respect to aspects of interest to this invention.

[0089] The aforementioned first switching arrangement may also include electronic devices or circuits that perform the requested function. For the sake of brevity, these possible additional electrical devices or circuits are not described herein.

[0090] The switchgear 1 includes a control level 2, which includes a control unit 20 configured to control the operation of one or more controllable components of the switchgear.

[0091] The controllable components of switching equipment can be of various types, such as electronic devices, electromechanical devices, etc.

[0092] As can be clearly seen from the above, the controllable component includes the primary switching device 3 of the switching equipment. The control unit 20 can therefore control the operation of the primary switching device 3, such as its reversible transition between the on and off states.

[0093] Preferably, the control unit 20 is configured to process data / information according to an appropriate algorithm and provide appropriate control signals C to the aforementioned controllable components of the switching device.

[0094] Preferably, the control unit 20 can (in a known manner) communicate with one or more sensors (not shown) mounted on a switching device or along the wire 100 to receive data signals relating to the behavior of current, voltage and / or other physical quantities.

[0095] Preferably, the control unit 20 can communicate with local control devices (not shown) (e.g., protective relays) installed in the power grid and / or with remote control devices (not shown) (e.g., cloud computing systems) to exchange data signals and / or control signals with these external control devices.

[0096] Preferably, the control unit 20 includes a suitable digital processing device (e.g., one or more microprocessors) adapted to execute software instructions to perform the requested function.

[0097] Preferably, the control stage 2 includes an auxiliary storage circuit 21 (which may include one or more storage capacitors) electrically connected to the control unit 20.

[0098] Advantageously, the auxiliary storage circuit 21 is continuously charged during normal operation of the control level, and when the control level 2 can no longer be fed for any reason, the auxiliary storage circuit 21 can be used to feed the control unit 20 for a certain period of time.

[0099] In addition to the components described above, control level 2 may also include digital or analog electronic devices or circuits to perform the requested function. For the sake of brevity, these possible additional electrical devices or circuits are not described here.

[0100] Preferably, the switching device 1 includes a power supply stage 4 electrically connected to the control stage 2 to feed power drawn from the wire 100 to the control stage 2.

[0101] Preferably, the power stage 4 includes an input terminal 4A, at which the power stage 4 can be electrically connected to a first electrical terminal 11 or a second electrical terminal 12 of the switching device, as will be more clearly shown below.

[0102] Preferably, the power supply stage 4 includes an output terminal 4B, at which the power supply stage 4 is electrically connected to the control stage 2 to feed power to the control stage 2.

[0103] In the accompanying drawings, power stage 4 includes a pair of input terminals 4A and a pair of output terminals 4B, which have a floating voltage relative to ground. However, in some cases, one of the input terminals 4A and one of the output terminals 4B may be referred to as ground.

[0104] Preferably, the power stage 4 includes an input storage circuit 41 and a DC / DC converter 42 cascaded and electrically connected between the input and output terminals 4A and 4B.

[0105] Preferably, the DC / DC converter is electrically isolated. However, in some cases, a DC / DC converter without current isolation may also be used.

[0106] Preferably, the input storage circuit 41 includes one or more input capacitors.

[0107] Preferably, the DC / DC converter 42 includes a Buck type or a switching converter with another suitable configuration.

[0108] Preferably, the DC / DC converter 42 is configured to interact with the control unit 20 for operation.

[0109] Power stage 4 may also include digital or analog electronic devices or circuits to perform the requested function. For the sake of brevity, these possible additional electrical devices or circuits are not described here.

[0110] Typically, control stage 2 and power stage 4 of a switching device can be implemented at the industrial level, based on known types of solutions. Therefore, they will be described below only with respect to aspects of interest to this invention.

[0111] According to the present invention, the switching device 1 includes a secondary switching device, which includes one or more secondary switching devices 5 that can be controlled by the control unit 20.

[0112] Secondary switching device 5 is electrically connected to the first and second electrical terminals 11, 12 of the switching equipment and the power supply stage 4, namely the input terminal 4A of the power supply stage 4.

[0113] The secondary switching device 5 is configured to reversibly switch between a first switching state S1 and a second switching state S2 when an appropriate input control signal is received from the control unit 20.

[0114] When they are in the first switching state S1, the secondary switching device 5 electrically connects the first electrical terminal 11 of the switching device to the power supply stage 4 and electrically disconnects the second electrical terminal 12 of the switching device from the power supply stage 4. Figure 3A ).

[0115] When they are in the second switching state S2, the secondary switching device 5 electrically connects the second electrical terminal 12 of the switching device to the power supply stage 4 and electrically disconnects the first electrical terminal 11 of the switching device from the power supply stage 4. Figure 3B ).

[0116] As can be clearly seen from the above, once the appropriate input control signal is received from the control unit 20, the secondary switching device 5 can alternately connect the power stage 4 to the first terminal 11 or the second terminal 12. Therefore, the power stage 4 can be electrically connected to the power supply side or the load side of the wire 100 as needed.

[0117] As will become clearer below, this solution allows for the prevention of damage to power stage 4 during the disconnection operation of the switchgear, while ensuring optimal performance and interruption ratings of the switchgear, especially in the event of electrical faults such as short circuits.

[0118] According to some embodiments of the present invention ( Figure 2 The secondary switching device 5 is electromechanical. As an example, each secondary switching device 5 may be formed by an electromechanical relay having multiple electrical contacts that can be coupled or decoupled upon receiving an appropriate input control signal.

[0119] When the corresponding electrical contact is made to electrically connect the first electrical terminal 11 of the switching device to the power stage 4 and electrically disconnect the second electrical terminal 12 of the switching device from the power stage 4, Figure 3A When operating in the manner described above, the electromechanical relay 5 is in the first switching state S1.

[0120] When the corresponding electrical contact is made to electrically disconnect the first electrical terminal 11 of the switching device from the power supply stage 4 and electrically connect the second electrical terminal 12 of the switching device to the power supply stage 4, Figure 3B When operating in the manner described above, the electromechanical relay 5 is in the second switching state S2.

[0121] Other embodiments of the present invention ( Figure 3 The secondary switching device 5 is of the solid-state type and each includes one or more switches based on semiconductor materials. For example, each secondary switching device 5 may include a switching circuit comprising a plurality of semiconductor switches capable of reversibly switching between an on state and an off state upon receiving an appropriate input control signal.

[0122] When one or more semiconductor switches are respectively used to electrically connect the first electrical terminal 11 of the switching device to the power stage 4 and electrically disconnect the second electrical terminal 12 of the switching device from the power stage 4 ( Figure 3A When operating in the manner described above, the secondary switching device 5 is in the first switching state S1.

[0123] When one or more corresponding semiconductor switches electrically disconnect the first electrical terminal 11 of the switching device from the power supply stage 4 and electrically connect the second electrical terminal 12 of the switching device to the power supply stage 4 ( Figure 3B When operating in the manner described above, the secondary switching device 5 is in the second switching state S2.

[0124] Preferably, each secondary switching device 5 may include a protection circuit (not shown) electrically connected in parallel with one or more semiconductor switches. Such a protection circuit may advantageously include one or more metal oxide rheostats, buffers, spark gaps, discharge tubes, etc.

[0125] According to other embodiments of the invention (not shown), the secondary switching device 5 is hybrid. In this case, each secondary switching device includes one or more semiconductor-based switches and one or more electromechanical switches.

[0126] Typically, secondary switching devices 5 of switching devices can be implemented at the industrial level based on known types of solutions. Therefore, they will be described below only with respect to aspects of interest to the present invention.

[0127] The aforementioned second switch arrangement may also include electronic equipment or circuits that perform the requested function.

[0128] For example, it may include diodes arranged in series with each secondary switching device 5 to prevent reverse current from flowing through the switching device, thereby preventing the storage circuit 41 from discharging.

[0129] For the sake of brevity, possible additional electrical devices or circuits are not described here.

[0130] According to one aspect of the invention, the control unit 20 is configured to command the secondary switching device 5 to operate in the first switching state S1 or the second switching state S2, or to reversibly switch between the first and second switching states S1 and S2, depending on the operating state of the switching device (and therefore the operating state of the primary switching device 3).

[0131] Preferably, the control unit 20 is configured to command the secondary switching device 5 to operate in the first switching state or the second switching state when the switching device is operating in the closed state A or the open state B.

[0132] The control unit 20 is configured to select the switching state S1 or S2 for the secondary switching device 5 based on the direction of electrical power flow along the wire 100 and the state of the switching device.

[0133] If the first electrical terminal 11 is electrically connected to the power supply portion of the wire and the second electrical terminal 12 is electrically connected to the load portion of the wire (power flows along the wire in the direction from the first electrical terminal 11 to the second electrical terminal 12), then when the switching device is in the open state B, the control unit 20 commands the secondary switching device 5 to operate in the first switching state S1 described above, and when the switching device is in the closed state A, the control unit 20 commands the secondary switching device 5 to operate in the second switching state S2 described above. Figure 5 ).

[0134] If the first electrical terminal 11 is electrically connected to the load portion of the wire and the second electrical terminal 12 is electrically connected to the power supply portion of the wire (power flows along the wire in the direction from the second electrical terminal 12 to the first electrical terminal 11), then when the switching device is in the open state B, the control unit 20 commands the secondary switching device 5 to operate in the second switching state S2 described above, and when the switching device is in the closed state A, the control unit 20 commands the secondary switching device 5 to operate in the first switching state S1 described above. Figure 6 ).

[0135] When the power flow changes direction according to the instantaneous operating state of the power grid, the control unit 20 can dynamically change the control logic of the switching device 5 as needed.

[0136] As an example, the control unit 20 can determine the direction of power flow along the wire 100 based on appropriate detection signals received by appropriate sensors arranged on the switching device or along the wire 100, and command the switching device 5 by dynamically selecting the most suitable control logic.

[0137] Preferably, the control unit 20 is configured to command the secondary switching device 5 to reversibly switch between the first and second switching states S1, S2 during the opening or closing operation of the switching device.

[0138] The control unit 20 is configured to select the switching operation of the secondary switching device 5 based on the direction of electrical power flow along the wire 100 and the state of the switching device.

[0139] refer to Figure 7 If the first terminal 11 is electrically connected to the power supply portion of the wire and the second terminal 12 is electrically connected to the load portion of the wire (power flows along the wire in the direction from the first terminal 11 to the second terminal 12), then the control unit 20 commands the secondary switching device 5:

[0140] Before the primary switching device 3 performs the switching change corresponding to the closing operation (actually before the primary switching device 3 switches from the blocking state to the conducting state), it switches from the first switching state S1 to the second switching state S2.

[0141] When the primary switching device 3 has completed the switching change corresponding to the disconnection operation (actually after the primary switching device 3 switches from the on state to the off state), it switches back from the second switching state S2 to the first switching state S1.

[0142] Obviously, the switching timing between switch states S1 and S2 must be carefully adjusted to prevent power supply stage 4 from being connected to terminals 11 and 12 simultaneously, thereby preventing bypass of the main circuit breaker.

[0143] refer to Figure 8 If the first terminal 11 is electrically connected to the load portion of the wire and the second terminal 12 is electrically connected to the power supply portion of the wire (power flows along the wire in the direction from the second terminal 12 to the first terminal 11), then the control unit 20 commands the secondary switching device 5:

[0144] Before the primary switching device 3 performs the switching change corresponding to the closing operation (actually before the primary switching device 3 switches from the blocking state to the conducting state), it switches from the second switching state S2 to the first switching state S1.

[0145] When the primary switching device 3 has completed the switching change corresponding to the disconnection operation (actually after the primary switching device 3 switches from the on state to the off state), it switches back from the first switching state S1 to the second switching state S2.

[0146] When the power flow changes direction according to the instantaneous operating conditions of the power grid, the control unit 20 can dynamically change the control logic of the secondary switching device 5, as described above.

[0147] The behavior of the switching device according to the invention will now be described in more detail with reference to some specific operating conditions.

[0148] In the following discussion, it is assumed that the first and second electrical terminals 11, 12 of the switching device are electrically connected to the power supply portion and the load portion of the wire, respectively (electricity flows in the direction from the first electrical terminal 11 to the second electrical terminal 12).

[0149] The closed state (normal state) of the switchgear.

[0150] When the switching device is in closed state A, the primary switching device 3 operates in the conducting state and current flows along the wire.

[0151] Control unit 20 commands secondary switching device 5 to continue operating in the second switching state S2. Figure 5 ).

[0152] Therefore, power stage 4 is electrically connected to the second terminal 12, which is the load portion of the circuit, and is electrically disconnected from the first terminal 11.

[0153] The disconnection and opening operation of the switchgear can be performed at any time.

[0154] Disconnection operation of switching equipment

[0155] Now assume that the switching device must perform a disconnection operation, such as interrupting the nominal current, overload current, or short-circuit current along the wire.

[0156] Power stage 4 is electrically connected to the second terminal 12 and is electrically disconnected from the first terminal 11, that is, it is connected to the load portion of the wire.

[0157] Control unit 20 commands primary switching device 3 to switch from the on state to the off state.

[0158] When power stage 4 is electrically connected to the second terminal 12 (i.e., downstream of the primary switching device 3, referring to the direction of power flow along the wire) and is electrically disconnected from the first terminal 11 (i.e., upstream of the primary switching device 3), the possible current toward power stage 4 is interrupted by the primary switching device 3 itself, as the latter switches to a blocking state. Therefore, power stage 4 is unaffected by surge current.

[0159] Once the primary switching device 3 completes its switching transition, the control unit 20 commands the secondary switching device 5 to switch from the second switching state S2 to the first switching state S1. Figure 7 ).

[0160] Even if the control unit 20 cannot be fed by power drawn from the wires, the control unit 20 can still operate because it can utilize the electrical energy stored in the energy storage circuit 41 of the power stage 4 and / or stored by the auxiliary storage circuit 21.

[0161] Once the reverse switching of the secondary switching device 5 is completed, the power stage 4 is electrically connected to the first electrical terminal 11, that is, the power supply part of the wire, and is electrically disconnected from the second electrical terminal 12.

[0162] Even if the primary switching device 3 is in a blocking state and no current flows along the wire, the closing operation of the switching device can be performed at any time.

[0163] Disconnected state of switching equipment

[0164] When the switching device is in the open state B, the primary switching device 3 is in the blocking state and no current flows along the wire.

[0165] The control unit commands the secondary switching device 5 to continue operating in the first switching state S1. Figure 5 ).

[0166] Therefore, power stage 4 is electrically connected to the first electrical terminal 11, i.e., the power supply part of the circuit, and it is electrically disconnected from the second electrical terminal 12.

[0167] Even if the primary switching device 3 is in a blocking state and no current flows along the wire, the closing operation of the switching device can be performed at any time.

[0168] Closing operation of switchgear

[0169] Now assume that the switching device must perform a closing operation.

[0170] The control unit 20 initially commands the secondary switching device 5 to switch from the first switching state S1 to the second switching state S2. Figure 7 ).

[0171] Therefore, power stage 4 is electrically connected to the second electrical terminal 12, which is the load portion of the electrical line.

[0172] Once the secondary switching device 5 completes its switching process, the control unit 20 commands the primary switching device 3 to switch from the blocking state to the conducting state.

[0173] If no electrical fault occurs during the closing operation of the switching device, once the primary switching device 3 completes its switching transition, the control unit 20 commands the secondary switching device 5 to remain in the second switching state S2. Figure 7 ).

[0174] The disconnection operation of the switching equipment can be performed at any time.

[0175] If an electrical fault (e.g., a short circuit) occurs during the closing operation of the switching device (which generates current in case of a fault), the control unit 20 immediately commands the primary switching device 3 to switch back to the blocking state (in which case the secondary switching device 5 has no effect).

[0176] Once the primary switching device 3 completes its switching transition, the control unit 20 commands the secondary switching device 5 to switch back from the second switching state S2 to the first switching state S1. Figure 7 ).

[0177] In the same situation, the control unit 20 can still operate because it can utilize the electrical energy stored in the energy storage circuit 41 of the power stage 4 and / or stored by the auxiliary storage circuit 21.

[0178] Once the switching of the secondary switching device 5 is completed, the power stage 4 is reconnected to the first electrical terminal 11, i.e., the power supply part of the circuit, and is disconnected from the second electrical terminal 12.

[0179] Even if the primary switching device 3 is in a blocking state and no current flows along the wire, the closing operation of the switching device can be performed at any time (once the electrical fault is cleared).

[0180] If the first and second electrical terminals 11, 12 of the switching device are respectively electrically connected to the load portion and the power supply portion of the power line (power flows in the direction from the second electrical terminal 12 to the first electrical terminal 11), the behavior of the switching device according to the present invention is substantially the same. However, in this case, compared with the control logic described above, the control unit will employ the inverse control logic of the switching transformation of the secondary switching device 5 ( Figure 6 and 8 ).

[0181] When the power flow along the wire changes its direction according to the instantaneous operating state of the power grid, once the direction of the power flow is determined, the control unit 20 can dynamically change the selection logic of the switching conversion of the secondary switching device 5.

[0182] Compared with similar electrical systems in the prior art, the switching device according to the present invention offers relevant advantages.

[0183] With the aid of the aforementioned secondary switching device, the power stage of the switching device can be electrically connected to the load portion of the wire (i.e., downstream of the primary switching device designed to interrupt the current along the wire) or electrically connected to the power supply portion of the wire (i.e., upstream of the primary switching device designed to interrupt the current along the wire) in an alternating manner and depending on the operating conditions of the switching device.

[0184] By properly coordinating the switching transitions of the primary and secondary switching devices of the switchgear, this allows inrush current to be prevented from flowing through the power stage during the opening operation of the switchgear and during the closing operation of the switchgear (in case of a fault). Simultaneously, the control stage of the switchgear can be appropriately fed when needed.

[0185] Since the switching equipment no longer bears the flow of surge current, the power supply stage of the switching equipment can be designed to include a relatively small input capacitance and a reduced set of protection devices.

[0186] Therefore, the power stage of a switching device can have a very compact structure and be very inexpensive to manufacture at the industrial level.

[0187] On the other hand, the arrangement of smaller input capacitors in the power stage allows for improved interrupt ratings of the primary switching devices of the switching equipment, especially when the primary switching devices of the switching equipment are solid-state types.

[0188] The switching device according to the invention can ensure a high level of performance, while being relatively easy and inexpensive to manufacture at the industrial level.

Claims

1. A switching device (1) for a DC power grid, comprising: The first electrical terminal (11) and the second electrical terminal (12) are used for electrical connection with the corresponding conductor of the wire (100); A primary switching device includes one or more primary switching devices (3) configured to reversibly switch between an on state and an off state. In the on state, the primary switching device conducts current between a first electrical terminal (11) and a second electrical terminal (12), and in the off state, the primary switching device blocks the current flowing between the first electrical terminal (11) and the second electrical terminal (12). The control level (2) includes a control unit (20) configured to control one or more controllable components (30, 31, 32, 5, 42) of the switching device; A power supply stage (4) is electrically connected to the control stage (2) to feed power drawn from the wire (100) to the control stage (2); The switching device is characterized in that it includes a secondary switching device, which includes one or more secondary switching devices (5) controllable by the control unit (20). The secondary switching devices are configured to reversibly switch between a first switching state (S1) and a second switching state (S2). In the first switching state, the secondary switching device electrically connects the first electrical terminal (11) to the power stage (4) and electrically disconnects the second electrical terminal (12) from the power stage (4). In the second switching state, the secondary switching device electrically disconnects the first electrical terminal (11) from the power stage (4) and electrically connects the second electrical terminal (12) to the power stage (4).

2. The switching device according to claim 1, characterized in that, The control unit (20) is configured to command the secondary switching device (5) to operate according to the operating state of the switching device.

3. The switching device according to claim 2, characterized in that, The control unit (20) is configured to: If the first electrical terminal (11) is electrically connected to the power supply portion of the wire (100) and the second electrical terminal (12) is electrically connected to the load portion of the wire, then: When the switching device is in the open state (B), the secondary switching device (5) is commanded to operate in the first switching state (S1); as well as When the switching device is in the closed state (A), the secondary switching device (5) is commanded to operate in the second switching state (S2).

4. The switching device according to claim 2, characterized in that, The control unit (20) is configured to: If the first electrical terminal (11) is electrically connected to the load portion of the wire (100) and the second electrical terminal (12) is electrically connected to the power supply portion of the wire, then: When the switching device is in the open state (B), the secondary switching device (5) is commanded to operate in the second switching state (S2); as well as When the switching device is in the closed state (A), the secondary switching device (5) is commanded to operate in the first switching state (S1).

5. The switching device according to claim 2, characterized in that, The control unit (20) is configured to command the secondary switching device (5) to reversibly switch between the first switching state (S1) and the second switching state (S2) during the opening or closing operation of the switching device.

6. The switching device according to claim 5, characterized in that, The control unit (20) is configured to command the secondary switching device (5): If the first electrical terminal (11) is electrically connected to the power supply portion of the wire (100) and the second electrical terminal (12) is electrically connected to the load portion of the wire, then: Before the primary switching device (3) performs a switching change corresponding to a closing operation, it switches from the first switching state (S1) to the second switching state (S2); When the primary switching device (3) has completed the switching change corresponding to the disconnection operation, it switches back from the second switching state (S2) to the first switching state (S1).

7. The switching device according to claim 5, characterized in that, The control unit (20) is configured to command the secondary switching device (5): If the first electrical terminal (11) is electrically connected to the load portion of the wire (100) and the second electrical terminal (12) is electrically connected to the power supply portion of the wire, then: Before the primary switching device (3) performs the switching change corresponding to the closing operation, it switches from the second switching state (S2) to the first switching state (S1); When the primary switching device (3) has completed the switching change corresponding to the disconnection operation, it switches back from the first switching state (S1) to the second switching state (S2).

8. The switching device according to any one of the preceding claims, characterized in that, The one or more primary switching devices (3) are solid-state type switching devices, each including one or more switches (30) based on semiconductor materials.

9. The switching device according to any one of claims 1 to 7, characterized in that, The one or more primary switching devices (3) are electromechanical switching devices.

10. The switching device according to any one of the preceding claims, characterized in that, The secondary switching device (5) is an electromechanical type switching device.

11. The switching device according to any one of claims 1 to 9, characterized in that, The secondary switching device (5) is a solid-state type switching device, each comprising one or more switches based on semiconductor materials.

12. The switching device according to any one of claims 1 to 9, characterized in that, The secondary switching device (5) is a hybrid type of switching device, each comprising one or more semiconductor-based switches and one or more electromechanical switches.

13. A DC power grid, comprising at least one switching device (1) according to any of the preceding claims.

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