Multi-port DC circuit breaker

Abstract

The invention provides a multi-port direct-current circuit breaker, the multi-port direct-current circuit breaker is provided with N ports, N through-flow branches and N oscillation branches, N is a positive integer and is greater than or equal to 3, the ports are sequentially connected through the through-flow branches to form a closed loop, the ports are correspondingly connected with a plurality of direct-current lines at an intersection, and the oscillation branches are connected with the ports. One end of each oscillation branch is connected with the corresponding port, and the other end of each oscillation branch is connected to a common point, so that any two ports are connected through the two oscillation branches connected in series, compared with a two-port direct current circuit breaker, the withstand voltage of each device in the oscillation branches can be reduced by half, and the cost of the devices is positively correlated with the withstand voltage; therefore, the cost of the multi-port direct-current circuit breaker is reduced.

Description

Technical Field

[0001] This application belongs to the field of power semiconductor device technology, and in particular relates to a multi-port DC circuit breaker. Background Technology

[0002] Large-scale offshore wind farms will become a major source of clean energy in the future, and these farms are often characterized by their long distance from shore and wide distribution. With the development of power devices and the increase in the total installed capacity of offshore wind farms, multi-terminal high-voltage direct current transmission based on voltage source converter stations has become the mainstream choice for connecting multiple offshore wind farms.

[0003] In multi-terminal flexible DC power grids, there are usually multiple junctions of DC lines. To ensure the reliability of the flexible DC power grid operation, DC circuit breakers also need to be installed at the junctions of multiple DC lines. If these circuit breakers are all conventional two-port DC circuit breakers, the cost of the entire system will be high. Summary of the Invention

[0004] This application provides a multi-port DC circuit breaker in which any two ports are connected by two series-connected oscillating branches. Compared with a two-port DC circuit breaker, the withstand voltage of each device in the oscillating branches can be reduced by half, thereby reducing the cost of the multi-port DC circuit breaker.

[0005] In a first aspect, embodiments of this application provide a multi-port DC circuit breaker, which is disposed at the intersection of multiple DC lines. The multi-port DC circuit breaker includes: N ports, N current-carrying branches and N oscillation branches, where N is a positive integer and N is greater than or equal to 3. Each port is connected in sequence through a current-carrying branch to form a closed loop; the port is also connected to a DC line. The current-carrying branch includes a switching module; Each oscillation branch corresponds to a port, with one end of each oscillation branch connected to its corresponding port, and the other end of each oscillation branch connected to a common point.

[0006] In some embodiments, the oscillation branch includes an oscillation inductor and an oscillation capacitor, with the oscillation capacitor connected in series with the oscillation inductor.

[0007] In some embodiments, the rated withstand voltage of the oscillating capacitor is greater than or equal to a first preset voltage, which is determined based on the breaking overvoltage of the multi-port DC circuit breaker.

[0008] In some embodiments, the oscillation branch further includes: an energy-consuming unit; At least one of the oscillating capacitor and the oscillating inductor is connected in parallel with the energy-consuming unit.

[0009] In some embodiments, the power-consuming unit includes a first metal oxide varistor.

[0010] In some embodiments, the switching module includes M mechanical switches, where M is a positive integer and M is greater than or equal to 1; When M is greater than or equal to 2, M mechanical switches are connected in series.

[0011] In some embodiments, the mechanical switch includes a vacuum mechanical switch and / or a gas mechanical switch.

[0012] In some embodiments, the rated withstand voltage of the mechanical switch is greater than or equal to a second preset voltage, which is determined based on the rated voltage of the multi-port DC circuit breaker.

[0013] In some embodiments, the current-carrying branch further includes an oscillation module, which is connected in series with the switching module.

[0014] In some embodiments, the oscillation module includes a switching unit and a protection unit, wherein the switching unit and the protection unit are connected in parallel.

[0015] In some embodiments, the switching unit comprises multiple series-connected switching sub-units, each sub-unit including two anti-connected series-connected switching transistors, with a diode connected in parallel across the two ends of each switching transistor, the conduction direction of the diode being opposite to the conduction direction of the parallel-connected switching transistors.

[0016] In some embodiments, the protection unit includes a second metal oxide varistor, which is connected in parallel with the switching subunit.

[0017] In some embodiments, the protection unit further includes a high-arc voltage switch, which is connected in parallel with the switching unit.

[0018] The multi-port DC circuit breaker provided in this application embodiment has multiple ports, multiple current-carrying branches, and multiple oscillating branches. Each port is connected in sequence through the current-carrying branches to form a closed loop. Each port is connected to multiple DC lines at the junction point. One end of each oscillating branch is connected to the corresponding port, and the other end is connected to a common point, so that any two ports are connected through two oscillating branches in series. Compared with a two-port DC circuit breaker, the withstand voltage of each device in the oscillating branch can be reduced by half. Since the cost of the device is positively correlated with the withstand voltage, the cost of the multi-port DC circuit breaker is reduced. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application; Figure 3 This is a schematic diagram of the structure of an oscillation module provided in one embodiment of this application; Figure 4 This is a schematic diagram of the structure of an oscillation module provided in another embodiment of this application; Figure 5 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application; Figure 6 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application; Figure 7 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application; Figure 8 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application; Figure 9 This is a schematic diagram of the structure of a multi-port DC circuit breaker provided in another embodiment of this application. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0022] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0023] In related technologies, conventional two-port DC circuit breakers are used at the junction of multiple DC lines. This places high voltage requirements on the components in the oscillating branch. Typically, the cost of electronic components is positively correlated with their rated withstand voltage, resulting in high costs for the power grid system.

[0024] To address the aforementioned technical problems, this application proposes a multi-port DC circuit breaker. This multi-port DC circuit breaker has N ports, N current-carrying branches, and N oscillating branches, where N is a positive integer and greater than or equal to 3. Each port is sequentially connected through the current-carrying branches to form a closed loop. Each port is correspondingly connected to multiple DC lines at the junction point. One end of each oscillating branch is connected to the corresponding port, and the other end is connected to a common point, so that any two ports are connected through two oscillating branches in series. Compared to a two-port multi-port DC circuit breaker, the withstand voltage of each device in the oscillating branch can be reduced by half, and the cost of the device is positively correlated with the withstand voltage, thereby reducing the cost of the multi-port DC circuit breaker.

[0025] The multi-port DC circuit breaker provided in the embodiments of this application is described below.

[0026] Figure 1 This is a schematic diagram of a multi-port DC circuit breaker provided in one embodiment of this application. The multi-port DC circuit breaker is disposed at the intersection of multiple DC lines and connected to the multiple DC lines.

[0027] like Figure 1 As shown, the multi-port DC circuit breaker may include: N ports, N current-carrying branches 1 and N oscillating branches 2, where N is a positive integer and N is greater than or equal to 3. The number of ports of the multi-port DC circuit breaker can be set according to the number of DC lines at the junction point. As an example, one port connects to one DC line.

[0028] Each port is connected in sequence through current-carrying branch 1 to form a closed loop; the port is also connected to a DC line.

[0029] For example, such as Figure 4 As shown, N equals 4, and the four ports are port A, port B, port C, and port D. Port A and port B are connected by a flow path 1, port B and port C are connected by a flow path 1, port C and port D are connected by a flow path 1, and port D and port A are connected by a flow path 1. With this configuration, ports A, B, C, and D form a closed loop through the four flow paths 1, and the closed loop is quadrilateral in shape.

[0030] It should be noted that, Figure 1The example shown is for a case where N equals 4, i.e., the multi-port DC circuit breaker includes four ports, four current-carrying branches, and four oscillation branches, and the overall shape of the multi-port DC circuit breaker is quadrilateral. However, this does not constitute a limitation on the multi-port DC circuit breaker provided in the embodiments of this application. In other embodiments, the multi-port DC circuit breaker may also include 3, 5, or more ports, and the overall shape of the multi-port DC circuit breaker may be set to any shape known to those skilled in the art, and is not limited herein.

[0031] The current-carrying branch 1 may include a switch module 11. The switch module 11 is used to control the conduction and disconnection of the current-carrying branch 1. Under normal operation of the power grid system, the switch module 11 is in the closed state, conducting the current-carrying branch 1, and the normal operating current flows in the current-carrying branch 1, while the oscillation branch 2 is bypassed. In the event of a fault in the power grid system, for example, a short-circuit fault occurs at port D, and the fault current flows to port D through the switch module 11 connected to port D and rises rapidly. After receiving the trip command, the multi-port DC circuit breaker sends trip commands to the two switch modules 11 connected to port D respectively. In response to the trip command, the switch module 11 disconnects the current-carrying branch it is in.

[0032] Each oscillation branch 2 corresponds one-to-one with a port. One end of each oscillation branch 2 is connected to its corresponding port, and the other end of each oscillation branch 2 is connected to a common point O. Any two ports are connected through two oscillation branches 2 connected in series. For example, as shown... Figure 4 As shown, the oscillation branch 2 corresponding to port A is denoted by OA, the oscillation branch 2 corresponding to port B is denoted by OB, the oscillation branch 2 corresponding to port C is denoted by OC, and the oscillation branch 2 corresponding to port D is denoted by OD.

[0033] As an example, the common point O can be a neutral point.

[0034] In related technologies, only one oscillation branch is provided between two-port and multi-port DC circuit breakers. In the multi-port DC circuit breaker provided in this application embodiment, two series-connected oscillation branches 2 are provided between any two ports. The withstand voltage of each device in the oscillation branch 2 can be reduced by half, and the cost of the device is positively correlated with the withstand voltage, thereby reducing the cost of the multi-port DC circuit breaker.

[0035] In addition, a multi-port DC circuit breaker with a corresponding number of ports can be set according to the number of DC lines at the junction point. The multi-port DC circuit breaker provided in this application has the advantages of high integration, small size and simple wiring, which helps to reduce installation and wiring costs.

[0036] This application proposes a multi-port DC circuit breaker, which has multiple ports, multiple current-carrying branches 1, and multiple oscillating branches 2. Each port is connected in sequence through the current-carrying branches 1 to form a closed loop. Each port is connected to multiple DC lines at the junction point. One end of each oscillating branch 2 is connected to the corresponding port, and the other end is connected to a common point O, so that any two ports are connected through two oscillating branches 2 in series. Compared with a two-port DC circuit breaker, the withstand voltage of each device in the oscillating branch 2 can be reduced by half, and the cost of the device is positively correlated with the withstand voltage, thereby reducing the cost of the multi-port DC circuit breaker.

[0037] In some embodiments, such as Figure 1 or Figure 2 As shown, the oscillation branch 2 may include an oscillation inductor 22 and an oscillation capacitor 21, with the oscillation capacitor 21 connected in series with the oscillation inductor 22.

[0038] In this embodiment, the oscillating inductor 22 and the oscillating capacitor 21 form an LC resonant circuit, and the oscillating inductor 22 and the oscillating capacitor 21 can realize the periodic mutual conversion of electric field energy and magnetic field energy.

[0039] After receiving the trip command, the switch module 11 will not disconnect immediately. The resonant current generated by the oscillating inductor 22 and the oscillating capacitor 21 is superimposed on the switch module 11, causing the switch module 11 to generate a zero-crossing point and complete the arc extinguishing interruption. The fault current no longer flows through the current-carrying branch 1 connected to the fault port.

[0040] In some embodiments, the rated withstand voltage of the oscillating capacitor is greater than or equal to a first preset voltage, which is determined based on the breaking overvoltage of the multi-port DC circuit breaker.

[0041] Combination Figure 1 or Figure 2 Compared to N two-port DC circuit breakers, the multi-port DC circuit breaker with N ports provided in this application embodiment uses the same number of capacitors, but two series-connected oscillation branches 2 are provided between any two ports. Each oscillation branch 2 is equipped with an oscillation capacitor 21. The rated withstand voltage of the oscillation capacitor 21 is halved. When selecting the oscillation circuit, a capacitor with a lower withstand voltage rating can be selected. The cost of the capacitor is proportional to the square of the rated withstand voltage, thereby significantly reducing the cost of the circuit breaker oscillation capacitor and thus reducing the cost of the power grid system.

[0042] For example, the breaking overvoltage of a multi-port DC circuit breaker is about 1.6 to 1.8 times its rated voltage. A first preset voltage can be set to be equal to half of the breaking overvoltage, and the withstand voltage of the oscillating capacitor can be greater than or equal to the first preset voltage.

[0043] In some embodiments, such as Figure 1 or Figure 2 As shown, the oscillation branch 2 also includes: an energy-consuming unit 23, which is connected in parallel with the oscillation capacitor 21.

[0044] In this embodiment, the energy-consuming unit 23 is used to monitor and limit the voltage across the oscillating capacitor 21 to prevent the oscillating capacitor 21 from breaking down due to overvoltage and to stabilize the LC resonance process.

[0045] In some embodiments, the energy-consuming unit is connected in parallel with the oscillating inductor.

[0046] In this embodiment, the energy dissipation unit 23 is used to suppress the reverse electromotive force overvoltage generated by the sudden change in current of the oscillating inductor 22, protect the oscillating inductor 22 and related devices, and stabilize the energy conversion during the LC resonance process.

[0047] In some embodiments, the power dissipation unit is connected in parallel with the oscillating inductor and the oscillating inductor.

[0048] In this embodiment, the oscillating inductor and oscillating capacitor form an LC resonant circuit. The energy dissipation unit is connected in parallel across the LC resonant circuit to provide "overvoltage protection" for the entire LC resonant circuit, while suppressing transient impacts and stabilizing the resonance process.

[0049] In some embodiments, such as Figure 1 or Figure 2 As shown, the power consumption unit 23 includes a first metal oxide varistor (MOV).

[0050] In this embodiment, the MOV is an overvoltage protection device with nonlinear voltage-resistance characteristics. Under normal voltage, the MOV exhibits a high-resistance state: when the circuit is at its normal operating voltage, the MOV's resistance is extremely high (reaching megaohms) and its leakage current is extremely low (reaching microamperes), hardly affecting the normal operation of the circuit, essentially acting as an "open circuit." Under overvoltage, the MOV exhibits a low-resistance conduction state: when an overvoltage occurs and the voltage exceeds the MOV's threshold voltage (i.e., varistor voltage), its resistance decreases sharply, dropping to the ohm or even milliohm level, allowing a large current to pass through instantaneously, clamping the overvoltage within a safe range, and preventing damage to downstream equipment due to overvoltage.

[0051] Meanwhile, the MOV also has a self-recovery characteristic after the overvoltage disappears. When the overvoltage disappears and the voltage drops back to the normal range, the MOV's resistance automatically returns to a high resistance state, returning to the "open circuit" mode, and it can resume operation without manual intervention.

[0052] In some embodiments, the residual voltage of the first metal oxide varistor is greater than or equal to a third preset voltage, which is determined based on the breaking overvoltage of the multi-port DC circuit breaker.

[0053] For example, the breaking overvoltage of the multi-port DC circuit breaker is about 1.6 to 1.8 times its rated voltage. A third preset voltage can be set to be equal to half of the breaking overvoltage, and the residual voltage of the first metal oxide varistor can be greater than or equal to the third preset voltage.

[0054] In some embodiments, such as Figure 1 or Figure 2 As shown, the switch module 11 includes M mechanical switches 111, where M is a positive integer and M is greater than or equal to 1; when M is greater than or equal to 2, the M mechanical switches 111 are connected in series.

[0055] In this embodiment, the switching module may include one mechanical switch or multiple mechanical switches. By connecting multiple mechanical switches in series, the withstand voltage of the entire switching module is increased as the number of series-connected mechanical switches increases, enabling the multi-port DC circuit breaker to reach a higher voltage level.

[0056] In some embodiments, the mechanical switch includes a vacuum mechanical switch and / or a gas mechanical switch.

[0057] In this embodiment, the switch module includes multiple mechanical switches, which can be vacuum mechanical switches, gas mechanical switches, or a combination of vacuum mechanical switches and gas mechanical switches.

[0058] Vacuum mechanical switches use high vacuum as the arc-extinguishing and insulating medium. Due to the lack of ionizing carriers, the arc is extinguished instantaneously at the current zero-crossing point after it is generated. Furthermore, the dielectric strength recovers extremely quickly after arc extinguishing, enabling them to adapt to high-frequency switching scenarios and preventing device damage caused by arc reignition. Simultaneously, the vacuum interrupter chamber employs a sealed structure, eliminating gas leakage, moisture absorption, or aging issues. Internal metal contact wear is minimal, resulting in low maintenance costs.

[0059] Gas-operated mechanical switches use sulfur hexafluoride (SF6) gas as the arc-quenching and insulating medium. SF6 has strong electronegativity and high insulation strength, enabling it to withstand ultra-high voltage conditions of 110kV~1000kV, avoiding insulation breakdown under high voltage. Furthermore, after arc quenching, the insulation strength of SF6 gas can recover to its initial value in a short time, supporting high-frequency switching operations, and leaving no residual arc after disconnection, thus avoiding interference with subsequent circuits.

[0060] In some embodiments, the rated withstand voltage of the mechanical switch is greater than or equal to a second preset voltage, which is determined based on the rated voltage of the multi-port DC circuit breaker.

[0061] The rated voltage of a multi-port DC circuit breaker is determined based on factors such as its application scenario and operating conditions.

[0062] For example, the second preset voltage is set to be equal to the rated voltage of the multi-port DC circuit breaker, that is, the rated voltage of the mechanical switch is greater than or equal to the rated voltage of the multi-port DC circuit breaker, so that the mechanical switch can maintain reliable insulation performance under all operating conditions, avoiding insulation breakdown due to insufficient voltage withstand, which may lead to equipment damage or safety accidents.

[0063] In some embodiments, such as Figure 2 As shown, the current-carrying branch 1 also includes an oscillation module 12, which is connected in series with the switch module 11.

[0064] In this embodiment, when the multi-port DC circuit breaker needs to be turned off, the control oscillation module 12 is periodically turned on and off to provide forced excitation to the oscillation branch 2, so that the oscillation capacitor 21 and oscillation inductor 22 in the oscillation branch 2 generate forced resonant current. As the number of cycles increases, the resonant current gradually amplifies and is eventually superimposed on the switch module 11 (or mechanical switch 111) to generate a zero crossing point. The switch module 11 (or mechanical switch 111) located on the same current-carrying branch as the oscillation module 12 is turned off.

[0065] For example, the on / off timing of the oscillation module 12 is precisely controlled to ensure that the excitation voltage (or excitation current) is in phase with the current oscillation state of the oscillation branch 2 each time it is turned on (i.e., the excitation direction is consistent with the current / voltage direction in the circuit). When the oscillation branch is in the capacitor discharge stage (current increases), the oscillation module 12 is turned on to inject energy into the current-carrying branch 1 to replenish the energy released by the capacitor. When it is in the inductor energy storage stage (voltage increases), the oscillation module 12 is turned off to prevent energy from flowing backward. After each cycle, the energy injected by the external excitation is greater than the energy consumed by the resistor in the current-carrying branch 1, causing the total energy stored in the current-carrying branch 1 to accumulate continuously. As the number of cycles increases, the energy storage continues to accumulate, and the peak value of the resonant current will gradually amplify until it is superimposed in reverse with the current in the current-carrying branch 1 (the current flowing through the mechanical switch 111), eventually causing the total current in the mechanical switch 111 to cross zero, achieving arc-free interruption.

[0066] In some embodiments, such as Figure 3 or Figure 4 As shown, the oscillation module 12 includes a switching unit 121 and a protection unit 122, with the switching unit 121 and the protection unit 122 connected in parallel.

[0067] In this embodiment, when it is necessary to connect the oscillation branch 2 and the current-carrying branch 1, the control switch unit 121 is turned on to form a current path and participate in the oscillation process. When it is necessary to disconnect the oscillation branch 2 and the current-carrying branch 1, the control switch unit 121 is turned off to cut off the current path. The protection unit 122 is used to protect the switch unit 121 to prevent damage to the switch unit 121 due to voltage spikes.

[0068] In some embodiments, such as Figure 3 or Figure 4 As shown, the switching unit 121 may include multiple series-connected switching subunits 1211. Each switching subunit includes two anti-connected series-connected switching transistors. A diode is connected in parallel across the two ends of each switching transistor. The conduction direction of the diode is opposite to the conduction direction of the parallel-connected switching transistors.

[0069] The switching transistor includes at least one of an insulated gate bipolar transistor (IGBT), an integrated gate-commutated thyristor (IGCT), and an injection-enhanced gate transistor (IEGT).

[0070] For example, such as Figure 3 or Figure 4 As shown, the switching unit 121 may include multiple switching subunits 1211 connected in series. Each switching subunit includes a first switching transistor Q1, a second switching transistor Q2, a first diode D1, and a second diode D2. The first switching transistor Q1 and the second switching transistor Q2 are connected in reverse series, and the first switching transistor Q1 is connected in parallel with the first diode D1, with the conduction direction of the first switching transistor Q1 opposite to that of the first diode D1. The second switching transistor Q2 is connected in parallel with the second diode D2, with the conduction direction of the second switching transistor Q2 opposite to that of the second diode D2. When it is necessary to connect the oscillation branch 2 and the current-carrying branch 1, the first switching transistor is controlled to conduct, forming a current path and participating in the oscillation process.

[0071] In this embodiment, when a drive signal is applied to the gate of the switching transistor, the switching transistor is turned on, and current flows through the switching transistor from one end to the other. At this time, the diode opposite to the switching transistor is turned off due to reverse bias. When the drive signal is removed from the gate of the switching transistor, the switching transistor is turned off, and the magnetic field energy stored in the oscillating inductor 22 in the oscillation branch 2 will generate a reverse electromotive force. At this time, the diode connected in reverse parallel is turned on due to forward bias, providing a freewheeling path for the inductive current and preventing the switching transistor from being broken down due to voltage spikes.

[0072] In some embodiments, such as Figure 3 or Figure 4 As shown, the protection unit 122 includes a second metal oxide varistor 1221, which is connected in parallel with the switch subunit 1211.

[0073] In this embodiment, the second metal oxide varistor 1221 is an overvoltage protection device. Under normal voltage, it exhibits a high resistance state, with a resistance reaching megaohms and a leakage current reaching microamperes, which hardly affects the normal operation of the circuit, essentially acting as an "open circuit." Under overvoltage, it exhibits a low resistance conducting state. When an overvoltage occurs in the circuit (such as a lightning strike or operational overvoltage), and the overvoltage exceeds the varistor voltage of the MOV, its resistance drops sharply to the ohm or even milliohm level, allowing a large current to pass through instantaneously, clamping the overvoltage within a safe range, and preventing the switching unit 121 from being damaged by the overvoltage. When the overvoltage disappears and the voltage returns to the normal range, the resistance of the second metal oxide varistor 1221 automatically returns to the high resistance state, allowing it to resume operation without manual intervention.

[0074] In some embodiments, such as Figure 4 As shown, the protection unit 122 also includes a high arc voltage switch 1222, which is connected in parallel with the switch unit 121.

[0075] The high-arc voltage switch 1222 is suitable for high-voltage, high-arc scenarios, achieving current interruption under high voltage through an arc-extinguishing mechanism. As an example, the high-arc voltage switch 1222 first generates an arc by tripping the circuit breaker, then transfers the current to the switching transistor using the arc voltage, which then periodically turns the circuit breaker on and off. The contacts and arc-extinguishing chamber structure of the high-arc voltage switch can withstand high arc voltages, preventing the arc from directly damaging the switch unit 121 (or the switching transistor).

[0076] The high arc voltage switch 1222 can increase the arc voltage of the mechanical switch 111 by means of magnetic blowout arc extinguishing, gas arc extinguishing or vacuum arc extinguishing.

[0077] In this embodiment, the switching transistor is responsible for high-frequency, rapid on / off control, enabling fine adjustment of the oscillation process; the high-arc voltage switch 1222 can operate when the switching transistor is turned off or in overvoltage scenarios, withstand higher arc voltage, assist in commutation or share voltage stress, and further improve the system's withstand voltage and reliability; the second metal oxide varistor 1221 undertakes overvoltage protection function, forming a multi-layer protection mechanism with the high-arc voltage switch and the switching transistor.

[0078] For example, such as Figures 5-9 As shown, taking a four-port DC circuit breaker as an example, the control timing and working principle of this multi-port DC circuit breaker are introduced. The thick black line represents the current flow path. This multi-port DC circuit breaker includes four ports: port A, port B, port C, and port D. The four ports are connected sequentially through current-carrying branches 1 (i.e., current-carrying branches AB, BC, CD, and DA) to form a loop. Each port is connected to the common point O through a corresponding oscillation branch 2, namely oscillation branches OA, OB, OC, and OD.

[0079] like Figure 5As shown, during normal operation, the normal operating current flows through the current-carrying branch 1 where the mechanical switch 111 is located, and the current does not pass through the oscillation branch 2, which is bypassed.

[0080] like Figure 6 As shown, in the event of a short-circuit fault at port D, the fault current flows to port D through mechanical switch 111 on current-carrying branch CD and mechanical switch 111 on current-carrying branch DA, causing the fault current to rise rapidly. Upon receiving a tripping command, the multi-port DC circuit breaker first sends tripping instructions to mechanical switches 111 on current-carrying branch CD and DA, and simultaneously activates the oscillation module 12. A certain tripping time is required for mechanical switches 111 on current-carrying branch CD and DA to reach a sufficient opening distance. Before this, mechanical switches 111 on current-carrying branch CD and DA are in the closed state; therefore, they are connected in parallel. Oscillating branches OA and OC are also connected in parallel. The oscillation module 12 on the current-carrying branch DA and the oscillation module 12 on the current-carrying branch CD are periodically turned on and off, and an amplified oscillation current is generated in the circuit formed by the oscillation branches OA, OC and OD and the corresponding mechanical switch 111. The current of the oscillation branch OD is the sum of the currents of the oscillation branches OA and OC.

[0081] like Figure 7 As shown, after a period of time, the amplitude of the oscillating current is sufficient to superimpose on the mechanical switch 111 on the current-carrying branch DA and the mechanical switch 111 on the current-carrying branch CD, causing it to generate a zero-crossing point and complete the arc-extinguishing interruption. Then, the fault current flows through the oscillating branches OA, OC and OD.

[0082] Figure 8 As shown, as the fault current continuously charges the oscillation capacitor 21 in the oscillation branch, the voltage across the oscillation capacitor 21 will reach the operating voltage of the energy dissipation unit 23 (e.g., MOV) connected in parallel with it. The fault current will be commutated from the oscillation capacitor 21 on the oscillation branches OA, OC and OD to the corresponding energy dissipation unit 23, where the energy dissipation units 23 on the oscillation branches OA, OC and OD are still connected in parallel.

[0083] like Figure 9 As shown, under the action of the energy dissipation unit 23, the voltage between the terminals of the multi-port DC circuit breaker is limited, and the fault current gradually decreases until it reaches zero, thus achieving the isolation of the fault terminal.

[0084] The above description is merely a specific implementation of this application. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific operation processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the protection scope of this application.

Claims

1. A multi-port DC circuit breaker, characterized in that, The multi-port DC circuit breaker is installed at the intersection of multiple DC lines. The multi-port DC circuit breaker includes: N ports, N current-carrying branches and N oscillation branches, where N is a positive integer and N is greater than or equal to 3. Each of the ports is connected sequentially through the current-carrying branch to form a closed loop; the port is also connected to the DC line. The current-carrying branch includes a switching module; Each oscillation branch corresponds to one of the ports, with one end of each oscillation branch connected to the corresponding port, and the other end of each oscillation branch connected to a common point.

2. The multi-port DC circuit breaker according to claim 1, characterized in that, The oscillation branch includes an oscillation inductor and an oscillation capacitor, with the oscillation capacitor connected in series with the oscillation inductor.

3. The multi-port DC circuit breaker according to claim 2, characterized in that, The rated withstand voltage of the oscillating capacitor is greater than or equal to a first preset voltage, which is determined based on the breaking overvoltage of the multi-port DC circuit breaker.

4. The multi-port DC circuit breaker according to claim 2, characterized in that, The oscillation branch also includes: an energy-consuming unit; At least one of the oscillating capacitor and the oscillating inductor is connected in parallel with the energy-consuming unit.

5. The multi-port DC circuit breaker according to claim 4, characterized in that, The energy-consuming unit includes a first metal oxide varistor.

6. The multi-port DC circuit breaker according to claim 1, characterized in that, The switching module includes M mechanical switches, where M is a positive integer and M is greater than or equal to 1; When M is greater than or equal to 2, the M mechanical switches are connected in series.

7. The multi-port DC circuit breaker according to claim 6, characterized in that, The mechanical switch includes a vacuum mechanical switch and / or a gas mechanical switch.

8. The multi-port DC circuit breaker according to claim 6, characterized in that, The rated withstand voltage of the mechanical switch is greater than or equal to a second preset voltage, which is determined based on the rated voltage of the multi-port DC circuit breaker.

9. The multi-port DC circuit breaker according to any one of claims 1-8, characterized in that, The current-carrying branch also includes an oscillation module, which is connected in series with the switching module.

10. The multi-port DC circuit breaker according to claim 9, characterized in that, The oscillation module includes a switching unit and a protection unit, wherein the switching unit and the protection unit are connected in parallel.

11. The multi-port DC circuit breaker according to claim 10, characterized in that, The switching unit comprises multiple series-connected switching subunits. Each switching subunit includes two anti-connected series-connected switching transistors. A diode is connected in parallel across the two ends of each switching transistor, and the conduction direction of the diode is opposite to that of the parallel-connected switching transistors.

12. The multi-port DC circuit breaker according to claim 11, characterized in that, The protection unit includes a second metal oxide varistor, which is connected in parallel with the switch subunit.

13. The multi-port DC circuit breaker according to claim 11, characterized in that, The protection unit also includes a high-arc voltage switch, which is connected in parallel with the switch unit.

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