A combined dc circuit breaker and breaking method

Abstract

A combined direct current circuit breaker and breaking method, the circuit breaker is composed of a main branch, a current transfer branch, a fuse branch and a MOV energy dissipation branch, the main branch, the current transfer branch, the fuse branch and the MOV energy dissipation branch are in parallel, the two sides of the whole topology are respectively led out into the line end and the outgoing line end, the main branch includes a vacuum arc-extinguishing chamber CB controlled by an external magnetic field, the current transfer branch includes a transfer capacitor C and a line stray inductance in series, the fuse branch includes a switch S and a fuse FUSE in series, the fuse branch transfers the current of the main branch to the fuse branch when breaking the fault current, then the fuse is fused, and the breaking is completed; the MOV energy dissipation branch includes a metal oxide varistor MOV to limit the overvoltage caused by the current mutation and dissipate energy.

Description

Technical Field

[0001] This invention relates to the field of DC circuit breaker technology, and in particular to a combined DC circuit breaker and its interruption method. Background Technology

[0002] Against the backdrop of ever-increasing energy demand and continuous optimization of the energy structure, the power system is undergoing profound changes and development. With the significant advantages of DC transmission technology in long-distance, high-capacity power transmission, renewable energy integration, and urban power grid supply, its application scope is becoming increasingly widespread. However, the inherent characteristics of DC systems also present a series of highly challenging problems for the design and operation of power equipment. Fault currents in DC systems rise extremely rapidly, and the absence of a natural zero-crossing point means that once a fault current occurs, it is difficult to extinguish itself. Traditional mechanical DC circuit breakers have long breaking times, large size, and high cost, while DC circuit breakers composed solely of fuses suffer from high on-state losses and difficult heat dissipation, often failing to meet practical application requirements.

[0003] The information disclosed in the background section is only intended to enhance the understanding of the background of the present invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a combined DC circuit breaker and its interruption method, which can quickly interrupt fault conditions. On the other hand, the rated current loss is significantly reduced and the volume is also significantly reduced. The circuit breaker structure is optimized, which can reduce the switching load and effectively improve the reliability of the circuit breaker.

[0005] The present invention adopts the following technical solution:

[0006] A combined DC circuit breaker consists of a main branch, a current transfer branch, a fuse branch, and an MOV energy dissipation branch. These four branches are connected in parallel, with input and output terminals extending from both sides of the topology. The main branch includes a vacuum interrupter CB controlled by an external magnetic field. Under normal operating conditions, the main branch carries the load current. Current transfer from the main branch to the current transfer branch or the fuse branch is achieved through the control of the external magnetic field under normal or fault conditions. The branch circuit includes a transfer capacitor C connected in series and a stray inductance of the line. When the current transfer branch interrupts the normal load current, the voltage of the transfer capacitor C is increased by LC oscillation, and the current of the main branch is transferred to the current transfer branch. The fuse branch circuit includes a switch S connected in series and a fuse FUSE. When the fuse branch interrupts the fault current, the current of the main branch is transferred to the fuse branch circuit, and then the fuse blows, completing the interruption. The MOV energy dissipation branch circuit includes a metal oxide zinc varistor MOV to limit overvoltage caused by sudden current changes and dissipate energy.

[0007] In the combined DC circuit breaker, when the system is operating normally, the system current is conducted through the vacuum interrupter CB of the main branch. When the system needs to be interrupted for normal operation, the system current gradually transfers to the current transfer branch under the control of the external magnetic field as the vacuum interrupter CB of the main branch is opened, and the voltage of the transfer capacitor C increases. When the voltage of the transfer capacitor reaches the conduction voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is dissipated and the system current disappears, thus completing the interruption of the load current.

[0008] In the combined DC circuit breaker, when a fault short circuit occurs in the system and needs to be interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current gradually shifts to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts and generates an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

[0009] In the combined DC circuit breaker, the opening and closing of the vacuum interrupter CB of the main branch is controlled by a fast-acting mechanism.

[0010] In the combined DC circuit breaker, the MOV energy dissipation branch includes one or a combination of the following devices: line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, and fully insulated composite jacket metal oxide surge arrester.

[0011] In the combined DC circuit breaker, the switch S is a bidirectional current-carrying switch, which includes one or more of the following devices: mechanical switch, thyristor, IGBT, IGCT.

[0012] In the combined DC circuit breaker, the combined DC circuit breaker interrupts both bidirectional load current and bidirectional fault current.

[0013] In the combined DC circuit breaker, the external magnetic field control unit of the vacuum interrupter CB includes a magnetic blow-out coil.

[0014] In the combined DC circuit breaker, the main branch includes a vacuum interrupter CB1 and a vacuum interrupter CB2 connected in series, the current transfer branch and the MOV energy dissipation branch are both connected in parallel to the vacuum interrupter CB1, and the fuse FUSE is connected in parallel to the vacuum interrupter CB2.

[0015] The breaking methods of combined DC circuit breakers include:

[0016] When the system is working normally, the system current is conducted through the vacuum interrupter CB of the main branch, and the switch S is open. No current flows through the current transfer branch, the fuse branch, and the MOV energy dissipation branch except for the main branch.

[0017] When the system interrupts the normal load current, the system current is transferred to the current transfer branch under the vacuum arc controlled by the external magnetic field as the vacuum interrupter CB of the main branch is opened. The transfer capacitor C and the stray inductance of the line form an LC oscillation circuit. Under the action of the forward and reverse currents, the voltage of the transfer capacitor C rises in the process of change. When the voltage of the transfer capacitor C reaches the operating voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is completely dissipated and the system current disappears, thus completing the interruption of the load current.

[0018] When the system fault short circuit is interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current is transferred to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts and generates an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the combined DC circuit breaker utilizes fast switching, vacuum interrupter and circuit design to quickly and safely disconnect bidirectional load or fault current in a short time, and the transfer capacitor does not require an additional charging system, which is inexpensive and can be applied to bidirectional current-carrying medium and low voltage DC systems. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0021] Figure 1 This is a schematic diagram of the circuit breaker body structure;

[0022] Figure 2 This is a schematic diagram of the circuit breaker breaking principle of the present invention, wherein, Figure 2 (a) is a schematic diagram of normal flow. Figure 2 (b) is a schematic diagram of the positive oscillating current in the current transfer branch after the vacuum switch in the main branch is opened under load current. Figure 2 (c) is a schematic diagram of the reverse oscillating current in the current transfer branch after the vacuum switch in the main branch is opened under load current. Figure 2 Image (d) is a schematic diagram of the energy dissipation process. Figure 2 (e) is the current diagram in the fuse branch after the vacuum switch of the main branch is opened under short-circuit fault current;

[0023] Figure 3 This is an embodiment A of the circuit breaker of the present invention having bidirectional breaking capability;

[0024] Figure 4 This is an embodiment B of the circuit breaker of the present invention having bidirectional breaking capability;

[0025] Figure 5 This is a schematic timing waveform diagram of the circuit breaker embodiment B of the present invention when interrupting the load current;

[0026] Figure 6 This is a schematic timing waveform diagram of the circuit breaker embodiment B of the present invention when interrupting the short-circuit current;

[0027] Figure 7 The figure shown is a simulation waveform of the bidirectional circuit breaker embodiment B interrupting a 5.7kA current when the transfer capacitor C is 200μF and the stray inductance of the line is 3μH. Detailed Implementation

[0028] Specific embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While specific embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0029] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out this disclosure; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of this disclosure. The scope of protection of this disclosure is determined by the appended claims.

[0030] To facilitate understanding of the embodiments of this disclosure, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of this disclosure.

[0031] like Figures 1 to 7 As shown, in one embodiment of the circuit breaker, a combined DC circuit breaker consists of a main branch, a current transfer branch, a fuse branch, and an MOV energy dissipation branch. These four branches are connected in parallel, with input and output terminals leading out from both sides of the entire topology. The main branch includes a vacuum interrupter CB controlled by an external magnetic field. Under normal operating conditions, the main branch carries the load current. The transfer of current from the main branch to the current transfer branch or the fuse branch is achieved through the control of the external magnetic field under normal or fault conditions. The current transfer branch includes a transfer capacitor C connected in series with a stray inductance in the line. When the current transfer branch interrupts the normal load current, the voltage of the transfer capacitor C increases through LC oscillation, and the current of the main branch is transferred to the current transfer branch. The fuse branch includes a switch S connected in series with a fuse FUSE. When the fuse branch interrupts the fault current, the current of the main branch is transferred to the fuse branch, and then the fuse blows, completing the interruption. The MOV energy dissipation branch includes a metal oxide zinc varistor MOV to limit overvoltage caused by sudden current changes and dissipate energy.

[0032] In the preferred embodiment of the combined DC circuit breaker, when the system is operating normally, the system current is conducted through the vacuum interrupter CB of the main branch. When the system needs to be interrupted for normal operation, the system current gradually transfers to the current transfer branch under the control of the external magnetic field as the vacuum interrupter CB of the main branch is opened, and the voltage of the transfer capacitor C increases. When the voltage of the transfer capacitor reaches the conduction voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is dissipated and the system current disappears, thus completing the interruption of the load current.

[0033] In the preferred embodiment of the combined DC circuit breaker, when a fault short circuit occurs in the system and needs to be interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current gradually shifts to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts and generates an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

[0034] In a preferred embodiment of the combined DC circuit breaker, the opening and closing of the vacuum interrupter CB of the main branch is controlled by a fast-acting mechanism.

[0035] In a preferred embodiment of the combined DC circuit breaker, the MOV energy dissipation branch includes one or a combination of the following devices: line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, and fully insulated composite-jacketed metal oxide surge arrester.

[0036] In a preferred embodiment of the combined DC circuit breaker, the switch S is a bidirectional current-carrying switch, which includes one or more of the following devices: mechanical switch, thyristor, IGBT, IGCT.

[0037] In a preferred embodiment of the combined DC circuit breaker, the combined DC circuit breaker interrupts both bidirectional load current and bidirectional fault current.

[0038] In a preferred embodiment of the combined DC circuit breaker, the external magnetic field control unit of the vacuum interrupter CB includes a magnetic blowout coil.

[0039] In a preferred embodiment of the combined DC circuit breaker, the main branch includes a vacuum interrupter CB1 and a vacuum interrupter CB2 connected in series, the current transfer branch and the MOV energy dissipation branch are both connected in parallel to the vacuum interrupter CB1, and the fuse FUSE is connected in parallel to the vacuum interrupter CB2.

[0040] The breaking methods of combined DC circuit breakers include:

[0041] When the system is working normally, the system current is conducted through the vacuum interrupter CB of the main branch, and the switch S is open. No current flows through the current transfer branch, the fuse branch, and the MOV energy dissipation branch except for the main branch.

[0042] When the system interrupts the normal load current, the system current is transferred to the current transfer branch under the vacuum arc controlled by the external magnetic field as the vacuum interrupter CB of the main branch is opened. The transfer capacitor C and the stray inductance of the line form an LC oscillation circuit. Under the action of the forward and reverse currents, the voltage of the transfer capacitor C rises in the process of change. When the voltage of the transfer capacitor C reaches the operating voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is completely dissipated and the system current disappears, thus completing the interruption of the load current.

[0043] When the system fault short circuit is interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current is transferred to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts and generates an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

[0044] In one embodiment, the combined DC circuit breaker consists of a main branch, a current transfer branch, a fuse branch, and an MOV energy dissipation branch, wherein the specific circuit structure (single current direction) is as follows: Figure 1 As shown.

[0045] (1) The main branch, current transfer branch, fuse branch and MOV energy dissipation branch are connected in parallel, and the incoming and outgoing terminals are respectively led out from both sides of the entire topology.

[0046] (2) The main branch consists of a vacuum interrupter CB that is controlled by an external magnetic field. Under normal circumstances, it carries the load current and can transfer the current from the main branch to the current transfer branch or the fuse branch under normal or fault conditions by controlling the external magnetic field.

[0047] (3) The current transfer branch is connected in series with the transfer capacitor C and the stray inductance of the line. When the normal load current is interrupted, the capacitor voltage is increased by LC oscillation, and the main branch current is transferred to the current transfer branch.

[0048] (4) The fuse branch consists of a switch S and a fuse FUSE. When interrupting the fault current, the main branch current is transferred to the fuse branch, and then the fuse blows, completing the interruption.

[0049] (5) The MOV energy dissipation branch consists of a zinc oxide varistor MOV, which is responsible for limiting overvoltage caused by sudden current changes and dissipating energy.

[0050] When the system is working normally, the system current is conducted through the vacuum interrupter CB of the main branch.

[0051] When the system needs to be switched off for normal operation, the system current gradually shifts to the current transfer branch under the control of the external magnetic field as the vacuum interrupter CB of the main branch is opened, causing the voltage of the transfer capacitor to rise. When the voltage of the transfer capacitor reaches the MOV turn-on voltage, the MOV turns on with a voltage limit and dissipates the remaining energy in the line until the energy is completely dissipated and the system current disappears, thus completing the interruption of the load current.

[0052] When a short circuit occurs in the system and needs to be interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch opens, the system current gradually shifts to the fuse branch under the control of an external magnetic field. When the fuse accumulates enough heat, it melts and generates an arc. The current in the fuse branch drops rapidly until the system current disappears, thus completing the interruption of the fault short circuit current.

[0053] The opening and closing of the vacuum interrupter CB in the main branch is controlled by a fast-acting mechanism. The current transfer branch connects the transfer capacitor C in series with the stray inductance of the line, and then in parallel across the vacuum interrupter CB. The fuse branch connects a switch S in series with a fuse FUSE, and then in parallel across the vacuum interrupter CB. The switch S can be any bidirectional current-carrying switch, including but not limited to one or more combinations of the following devices: mechanical switch, thyristor, IGBT, IGCT. The MOV energy dissipation branch includes but is not limited to one or more combinations of the following devices: metal oxide surge arrester, line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, fully insulated composite-jacketed metal oxide surge arrester, and detachable surge arrester.

[0054] Figure 2 This is a flowchart illustrating the opening and closing principle of the circuit breaker of this invention, as follows: Figure 2 As shown in Figure (a), when the system is operating normally, the system current is conducted through the vacuum switch of the main branch. When switch S is open, no current flows through the current transfer branch, the fuse branch, and the MOV energy dissipation branch, except for the main branch.

[0055] like Figure 2 (b) Figure 2 As shown in (c), when the system needs to interrupt the normal load current, the system current gradually transfers to the current transfer branch under the vacuum arc controlled by the external magnetic field as the main branch vacuum interrupter CB is opened. The transfer capacitor and the stray inductance of the line constitute an LC oscillating circuit. Under the action of forward and reverse currents, the voltage of the transfer capacitor rises as it changes.

[0056] like Figure 2 As shown in (d), when the voltage of the transfer capacitor reaches the operating voltage of the surge arrester, the surge arrester conducts and limits the voltage, and dissipates the remaining energy in the line until the energy is completely dissipated, the system current disappears, and the load current is interrupted.

[0057] likeFigure 2 As shown in (e), when a short circuit occurs in the system and needs to be interrupted, the switch S is closed. As the vacuum interrupter CB in the main branch opens, the system current gradually transfers to the fuse branch under the control of an external magnetic field. When the fuse accumulates sufficient heat, it melts and generates an arc. Subsequently, the current in the fuse branch rapidly decreases until the system current disappears, completing the interruption of the fault short circuit current. The opening and closing of the vacuum interrupter CB in the main branch is controlled by a fast-acting mechanism. The current transfer branch is connected in series with the transfer capacitor C and the stray inductance of the line, and in parallel across the vacuum interrupter CB. The fuse branch is connected in series with a switch S and a fuse FUSE, and in parallel across the vacuum interrupter CB. The switch S can be any bidirectional current-carrying switch, including but not limited to one or more combinations of the following devices: mechanical switch, thyristor, IGBT, IGCT. The MOV power dissipation branch includes, but is not limited to, one or more combinations of the following devices: metal oxide surge arrester, line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, fully insulated composite jacket metal oxide surge arrester, and detachable surge arrester.

[0058] Figure 3 The diagram shown is a circuit topology diagram of an embodiment A of a bidirectional circuit breaker based on the present invention. CB1 and CB2 are vacuum switches. When interrupting normal load current, CB2 short-circuits the fuse FUSE. When interrupting fault short-circuit current, CB2 disconnects to connect the fuse FUSE in series in the circuit, allowing the fuse to melt and interrupt the short-circuit current. Figure 4 The working principle of the left side is no different from that of the case of interrupting normal load current as described above.

[0059] Figure 4 The diagram shown is a circuit topology diagram of a bidirectional circuit breaker embodiment B based on the present invention, where T represents a bidirectional thyristor, and the drive circuits for the magnetic blow-out coil and the mechanical switch are not shown.

[0060] Figure 5The diagram shown is a schematic timing waveform of the bidirectional circuit breaker embodiment B when interrupting the load current: it is assumed that the direction of the system current during interruption is from left to right, and the positive direction of the current in each branch is also from left to right. The voltage is taken as the associated reference direction of the current. At time t0, the vacuum interrupter CB trips, creating a vacuum break. The current flowing through the vacuum break is called the break current, which oscillates from a decreasing state, while the transfer capacitor current oscillates from a rising state. Between t0 and t1, the transfer capacitor current and the break current continue to oscillate. At time t1, the transfer capacitor current, i.e., the transfer branch current, reaches the system short-circuit current. Assuming the vacuum interrupter CB can cut off, the entire system short-circuit current is transferred to the transfer branch. Between t1 and t2, under the action of the forward current, the capacitor voltage continues to rise. At time t2, the transfer capacitor voltage reaches the arrester's operating voltage, and the arrester's conduction voltage is limited. Between t2 and t3, the system short-circuit current decreases, and the transfer capacitor current gradually transfers to the arrester. At time t3, the transfer capacitor current returns to zero, the transfer capacitor voltage reaches its maximum value, and the arrester current also reaches its peak value. Between t3 and t4, the transfer capacitor voltage gradually decreases to the system voltage. Between t3 and t5, the arrester consumes the remaining energy in the system until the system current disappears, completing the interruption under the load current.

[0061] Figure 6 The diagram shows a schematic timing waveform of a bidirectional circuit breaker embodiment B when interrupting load current. It is assumed that the system current direction during interruption is from left to right, and the subsequent current direction in each branch is also from left to right. The voltage is taken as the associated reference direction of the current. At time t0, the vacuum interrupter CB trips. Between t0 and t1, the system current gradually transfers from the break point to the fuse, and the fuse voltage gradually increases. At time t1, the break point current is completely transferred to the fuse branch, assuming the vacuum switch can be cut off. At time t2, the fuse accumulates sufficient heat, causing it to melt, generating an arc and creating a voltage spike. Between t2 and t3, the fuse current gradually decreases. At time t3, the fuse current disappears. Assuming the fuse breaks are also successfully cut off, the short-circuit current interruption is complete.

[0062] Figure 7 The figure shows the simulated waveform of a bidirectional circuit breaker embodiment B interrupting a 5.7kA current when the transfer capacitor C is 200μF and the stray inductance of the line is 3μH. The curves in the figure are: green - breaking current, red - transfer capacitor voltage, and blue - transfer capacitor current, respectively. This illustrates the feasibility of the present invention.

[0063] Furthermore, during the normal load current interruption process, when the main branch vacuum interrupter CB triggers tripping, the external magnetic field control device adjusts the arc morphology in real time, causing the break current to rapidly transfer to the current transfer branch under the action of the arc voltage. At this time, the LC oscillation circuit formed by the transfer capacitor C and the stray inductance of the line is activated: the capacitor voltage and current begin to oscillate until the current is completely transferred to the current transfer branch. Subsequently, the transfer capacitor voltage continues to rise to the MOV conduction threshold, and the MOV quickly conducts and forms a low-resistance path, dissipating the remaining energy as heat. This process does not require an external charging system; it only relies on the natural voltage rise characteristics of LC oscillation and the voltage clamping effect of the MOV to ensure that the break current drops rapidly and crosses zero, avoiding arc reignition and overvoltage impact, while maintaining the small size design of the circuit breaker.

[0064] During fault short-circuit current interruption, after the system detects a fault, it quickly closes switch S to connect the fuse (FUSE) to the circuit. When CB trips, magnetic field control ensures that the current is quickly transferred from the main branch to the fuse branch. Under the action of the transferred current, the fuse (FUSE) accumulates heat energy through the Joule heating effect. When the temperature reaches the melting point of the fusible element, the fuse melts and generates an electric arc. This arc rapidly limits the current (current drop rate > 10kA / μs), causing the current in the fuse branch to quickly cross zero, ultimately cutting off the fault circuit. The synergistic effect of the fuse's thermal response characteristics and magnetic field control avoids the malfunction caused by sudden current changes in traditional fuses, while utilizing the fuse's high breaking capacity (capable of withstanding short-circuit currents above 100kA) to achieve rapid fault isolation. By employing a four-layer collaborative mechanism of "precise transfer under magnetic field control + passive boosting via LC oscillation + passive voltage limiting via MOV + thermal response interruption via fuse," the problem of interruption in DC systems without natural zero-crossing points is solved. This avoids the long interruption time of traditional mechanical circuit breakers and overcomes the drawbacks of high on-state losses and poor heat dissipation of pure fuses. Furthermore, since the transfer capacitor C utilizes stray inductance as an oscillation element and requires no additional energy storage, the circuit breaker is smaller and less expensive than traditional solutions, making it particularly suitable for bidirectional current interruption scenarios in medium- and low-voltage DC distribution systems (such as photovoltaic power plants, data centers, and electric vehicle charging networks).

[0065] Although the embodiments of this disclosure have been described above in conjunction with the accompanying drawings, this disclosure is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this disclosure, and all of these are within the scope of protection of this disclosure.

Claims

1. A combined DC circuit breaker, comprising a main branch, a current transfer branch, a fuse branch, and an MOV energy dissipation branch, characterized in that: The main branch, current transfer branch, fuse branch, and MOV energy dissipation branch are connected in parallel. The topology has input and output terminals on both sides. The main branch includes a vacuum interrupter CB controlled by an external magnetic field. Under normal operating conditions, the main branch carries the load current. Current transfer from the main branch to the current transfer branch or fuse branch is achieved through the control of the external magnetic field under normal or fault conditions. The current transfer branch includes a transfer capacitor C connected in series with a stray inductance. When the current transfer branch interrupts the normal load current, the voltage of the transfer capacitor C increases through LC oscillation, simultaneously transferring the main branch current to the current transfer branch. The fuse branch includes a switch S connected in series with a fuse FUSE. When the fuse branch interrupts a fault current, it transfers the main branch current to the fuse branch, and then the fuse blows, completing the interruption. The MOV energy dissipation branch includes a zinc oxide varistor (MOV) to limit overvoltage caused by sudden current changes and dissipate energy.

2. The combined DC circuit breaker according to claim 1, characterized in that: Preferably, when the system is operating normally, the system current is conducted through the vacuum interrupter CB of the main branch. When the system needs to be disconnected for normal operation, the system current gradually transfers to the current transfer branch under the control of the external magnetic field as the vacuum interrupter CB of the main branch is opened, and the voltage of the transfer capacitor C increases. When the voltage of the transfer capacitor reaches the conduction voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is completely dissipated and the system current disappears, thus completing the disconnection of the load current.

3. The combined DC circuit breaker according to claim 1, characterized in that: When a short circuit occurs in the system and needs to be interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current gradually shifts to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts, generating an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

4. The combined DC circuit breaker according to claim 1, characterized in that: The opening and closing of the vacuum interrupter CB of the main branch circuit is controlled by a rapid-action mechanism.

5. The combined DC circuit breaker according to claim 4, characterized in that: The MOV power dissipation branch includes one or a combination of the following devices: line-type metal oxide surge arrester, gapless line-type metal oxide surge arrester, and fully insulated composite jacket metal oxide surge arrester.

6. The combined DC circuit breaker according to claim 1, characterized in that: The switch S is a bidirectional current-carrying switch, which includes one or more of the following devices: mechanical switch, thyristor, IGBT, IGCT.

7. The combined DC circuit breaker according to claim 1, characterized in that: The combined DC circuit breaker interrupts both bidirectional load current and bidirectional fault current.

8. The combined DC circuit breaker according to claim 1, characterized in that: The external magnetic field control unit of the vacuum interrupter CB includes a magnetic blow-out coil.

9. The combined DC circuit breaker according to claim 1, characterized in that: The main branch includes vacuum interrupters CB1 and CB2 connected in series, the current transfer branch and the MOV energy dissipation branch are both connected in parallel to the vacuum interrupter CB1, and the fuse FUSE is connected in parallel to the vacuum interrupter CB2.

10. The breaking method of the combined DC circuit breaker according to any one of claims 1-9, characterized in that: It includes, When the system is working normally, the system current is conducted through the vacuum interrupter CB of the main branch, and the switch S is open. No current flows through the current transfer branch, the fuse branch, and the MOV energy dissipation branch except for the main branch. When the system interrupts the normal load current, the system current is transferred to the current transfer branch under the vacuum arc controlled by the external magnetic field as the vacuum interrupter CB of the main branch is opened. The transfer capacitor C and the stray inductance of the line form an LC oscillation circuit. Under the action of the forward and reverse currents, the voltage of the transfer capacitor C rises in the process of change. When the voltage of the transfer capacitor C reaches the operating voltage of the metal oxide varistor MOV, the metal oxide varistor MOV conducts to limit the voltage and dissipates the remaining energy in the line until the energy is completely dissipated and the system current disappears, thus completing the interruption of the load current. When the system fault short circuit is interrupted, the switch S is closed. As the vacuum interrupter CB of the main branch is opened, the system current is transferred to the fuse branch under the control of the external magnetic field. When the fuse accumulates heat and melts and generates an arc, the current in the fuse branch decreases until the system current disappears, thus completing the interruption of the fault short circuit current.

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