Coupling self-turn-off type direct current circuit breaker and control method thereof

Abstract

The invention provides a coupling self-turn-off type direct-current circuit breaker and a control method thereof, and belongs to the technical field of direct-current power system fault protection, and the coupling self-turn-off type direct-current circuit breaker comprises a main branch circuit which comprises a control switch; the transfer branch is connected with the main branch in parallel and comprises a bridge circuit formed by diodes and a first thyristor; the turn-off branch comprises a transformer and a control branch connected with the transformer; the secondary side of the transformer and the first thyristor are connected in series between the two output ends of the bridge circuit; and the control branch circuit is used for controlling the secondary side of the transformer to induce a negative electromotive force in the breaking process, transferring the current of the main branch circuit to the first thyristor, charging the control branch circuit after the current of the main branch circuit is transferred, and discharging the primary side of the transformer under the condition that the charging voltage reaches a preset maximum value so as to carry out current breaking. According to the invention, the problems that the reliability of short-circuit breaking is low and the volume and cost of the circuit breaker are increased in a hybrid breaking technology can be solved.

Description

Technical Field

[0001] This invention relates to the field of fault protection technology for DC power systems, specifically to a coupled self-turn-off type DC circuit breaker and its control method. Background Technology

[0002] Hybrid breaking technology features extremely low on-state losses under rated current conditions, fast short-circuit breaking speed, and long service life, making it an ideal fault protection method in the field of medium / high voltage DC power systems.

[0003] Hybrid breaking technology is based on the principle of current transfer. In order to absorb the energy in the system during the short-circuit breaking process, a voltage limiting and energy dissipation device based on a varistor is required, which results in too many breaking links. On the one hand, it reduces the reliability of short-circuit breaking, and on the other hand, it increases the size and cost of the circuit breaker. Summary of the Invention

[0004] In view of this, it is necessary to provide a coupled self-turn-off DC circuit breaker and its control method to solve the technical problems of low short-circuit breaking reliability and increased circuit breaker size and cost in hybrid breaking technology.

[0005] To address the aforementioned problems, in a first aspect, the present invention provides a coupled self-turn-off type DC circuit breaker, comprising: Main branch circuit, including: control switch; A transfer branch, connected in parallel with the main branch, includes: a bridge circuit composed of diodes and a first thyristor; The shut-off branch includes: a transformer and a control branch connected to the transformer; the secondary side of the transformer is connected in series with the first thyristor between the two output terminals of the bridge circuit; The control branch is connected to the primary side of the transformer and is used to control the secondary side of the transformer to induce a negative electromotive force during the disconnection process, so as to transfer the current of the main branch to the first thyristor. After the current transfer of the main branch is completed, the transformer is controlled to stop operation and charge itself. When the charging voltage reaches the preset maximum value, the primary side of the transformer is discharged to disconnect the current.

[0006] In one possible implementation, the control branch includes: a second thyristor, a third thyristor, a fourth thyristor, a pre-charge capacitor, and an energy storage inductor. The cathode of the second thyristor, the anode of the third thyristor, the anode of the fourth thyristor, and one pole of the primary side of the transformer are all connected to the first node; The cathode of the fourth thyristor, the other pole of the primary side of the transformer, and the negative pole of the pre-charge capacitor are all connected to the fourth node. The anode of the second thyristor and one pole of the energy storage inductor are connected together at the second node; The cathode of the third thyristor, the other pole of the energy storage inductor, and the positive pole of the pre-charge capacitor are all connected to the third node.

[0007] In one possible implementation, the coupled self-turn-off DC circuit breaker further includes a controller for controlling the control switch to close under rated operating conditions and controlling the control switch to open during short-circuit breaking.

[0008] In one possible implementation, the controller is further configured to control the first thyristor and the second thyristor to conduct after a target time has elapsed after controlling the control switch to open, so as to transfer the current of the main branch to the first thyristor.

[0009] In one possible implementation, the controller is further configured to control the fourth thyristor to conduct after the current transfer in the main branch is completed, so as to charge the pre-charge capacitor.

[0010] In one possible implementation, the controller is further configured to control the third thyristor to conduct when the charging voltage of the pre-charge capacitor reaches a preset maximum value.

[0011] In one possible implementation, the control switch is a mechanical switch.

[0012] In one possible implementation, the bridge circuit includes: a first diode, a second diode, a third diode, and a fourth diode; The cathode of the first diode is connected to the cathode of the second diode, and the anodes of the first diode and the second diode are respectively connected to the two ends of the main branch. The positive terminal of the third diode is connected to the positive terminal of the fourth diode, and the negative terminals of the third diode and the fourth diode are respectively connected to the two ends of the main branch.

[0013] In one possible implementation, the transformer is a step-up transformer.

[0014] Secondly, the present invention also provides a control method for a coupled self-turn-off DC circuit breaker, the control method being applied to the coupled self-turn-off DC circuit breaker described in any of the above claims, the control method comprising: During the disconnection process, a negative electromotive force is induced on the secondary side of the control transformer to transfer the current of the main branch to the first thyristor. After the current transfer in the main branch is completed, the transformer is controlled to exit operation and the control branch itself is charged. When the charging voltage reaches the preset maximum value, the primary side of the transformer is discharged to interrupt the current.

[0015] The beneficial effects of the above implementation method are as follows: The coupled self-turn-off DC circuit breaker and its control method provided by this invention, during the short-circuit breaking process of the coupled self-turn-off DC circuit breaker, firstly, after the switch is opened for a period of time, a negative electromotive force is induced on the secondary side of the control transformer to transfer the current of the main branch to the first thyristor. After the current transfer of the main branch is completed, the control transformer is taken out of operation and charges itself. When the charging voltage reaches a preset maximum value, the primary side of the transformer is discharged, and an electromotive force much higher than the system voltage is induced on the secondary side, causing the short-circuit current to drop to zero and the first thyristor to turn off, thus realizing the system current breaking. The solution provided by this invention does not require the use of a voltage-limiting and energy-dissipating device based on a varistor, thereby avoiding too many breaking stages, ensuring the reliability of short-circuit breaking, and avoiding increasing the size and cost of the circuit breaker. This solves the technical problems of low short-circuit breaking reliability and increased circuit breaker size and cost associated with hybrid breaking technology. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A circuit topology diagram of an embodiment of the coupled self-turn-off DC circuit breaker provided by the present invention; Figure 2 The circuit topology diagram of the current transfer process of the coupled self-turn-off DC circuit breaker provided by the present invention; Figure 3 The circuit topology diagram of the reverse energy storage process of the coupled self-turn-off DC circuit breaker provided by the present invention; Figure 4 The circuit topology diagram of the self-turn-off process of the coupled self-turn-off type DC circuit breaker provided by the present invention; Figure 5 The current waveform diagram during the short-circuit protection process of the coupled self-turn-off DC circuit breaker provided by the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In the description of the embodiments of this application, unless otherwise stated, "a plurality of" means two or more.

[0020] In this embodiment of the invention, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, apparatus, product or device that includes a series of steps or modules is not necessarily limited to those steps or modules that are explicitly listed, but may include other steps or modules that are not explicitly listed or that are inherent to such process, method, product or device.

[0021] The naming or numbering of steps in the embodiments of the present invention does not mean that the steps in the method flow must be executed in the time / logical order indicated by the naming or numbering. The execution order of the named or numbered process steps can be changed according to the technical purpose to be achieved, as long as the same or similar technical effect can be achieved.

[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This invention provides a coupled self-turn-off DC circuit breaker and its control method, which are described below.

[0024] like Figure 1 As shown, the present invention provides a coupled self-turn-off type DC circuit breaker, comprising: The main branch includes: a control switch; both ends of the main branch are used to connect to the power system; the control switch is a mechanical switch S; A transfer branch is connected in parallel with the main branch, and the transfer branch includes: a bridge circuit composed of diodes D1, D2, D3, and D4 and a first thyristor T1; The shut-off branch includes: a transformer M1 and a control branch connected to the transformer M1; the secondary side of the transformer M1 is connected in series with the first thyristor T1 between the two output terminals of the bridge circuit; the transformer M1 is a step-up transformer; The control branch is connected to the primary side of the transformer M1. During the disconnection process, it controls the secondary side of the transformer M1 to induce a negative electromotive force to transfer the current of the main branch to the first thyristor T1. After the current transfer of the main branch is completed, it controls the transformer M1 to stop running and charge itself. When the charging voltage reaches the preset maximum value, it discharges the primary side of the transformer M1 to disconnect the current.

[0025] It is understood that one of the objectives of this invention is to provide a coupled self-turn-off DC circuit breaker to meet practical application needs. By utilizing the high-voltage electromotive force generated by the reverse pulse discharge circuit, the self-turn-off of the semi-controlled thyristor device is achieved, eliminating the need for the varistor's voltage limiting and energy consumption, improving the reliability of the breakout, and reducing the size and cost of the circuit breaker.

[0026] During the short-circuit breaking process of the coupled self-turn-off DC circuit breaker, the control switch is first opened. After a certain delay after the control switch is opened, a negative electromotive force is induced on the secondary side of the transformer M1 to transfer the current of the main branch to the first thyristor T1. After the current transfer of the main branch is completed, the transformer M1 is taken out of operation and the capacitor in its own circuit is charged. When the charging voltage reaches the maximum value, the capacitor discharges directly through the primary side of the transformer M1, and an electromotive force much higher than the system voltage is induced on the secondary side, causing the short-circuit current to drop to zero and the first thyristor T1 to turn off, thereby realizing the system current breaking.

[0027] In some embodiments, the control branch includes: a second thyristor T2, a third thyristor T3, a fourth thyristor T4, a pre-charge capacitor C0, and an energy storage inductor L0; The cathode of the second thyristor T2, the anode of the third thyristor T3, the anode of the fourth thyristor T4, and one pole of the primary side of the transformer are all connected to the first node; The cathode of the fourth thyristor T4, the other pole of the primary side of the transformer, and the negative pole of the pre-charge capacitor C0 are all connected to the fourth node. The anode of the second thyristor T2 is connected to the second node along with one pole of the energy storage inductor L0; The cathode of the third thyristor T3, the other pole of the energy storage inductor L0, and the positive pole of the pre-charge capacitor C0 are all connected to the third node.

[0028] It is understandable that the control branch consisting of the second thyristor T2, the third thyristor T3, the fourth thyristor T4, the pre-charge capacitor C0, and the energy storage inductor L0 can control the primary side of the transformer to conduct, thereby inducing a negative electromotive force on the secondary side of the transformer, causing the current to flow from the main branch to the first thyristor.

[0029] The pre-charge capacitor C0 can be charged after the current transfer is complete, and then discharged through the primary side of the transformer to achieve current interruption.

[0030] In some embodiments, the coupled self-turn-off DC circuit breaker further includes: a controller for controlling the control switch to close under rated operating conditions and controlling the control switch to open during short-circuit breaking.

[0031] Under normal operating conditions, the ultra-fast mechanical switch S is closed, carrying the system current. During short-circuit breaking, a tripping command is first sent to the ultra-fast mechanical switch S to control it to trip.

[0032] In some embodiments, the controller is further configured to control the first thyristor and the second thyristor T2 to conduct after a target time has elapsed after controlling the control switch to open, so as to transfer the current of the main branch to the first thyristor.

[0033] Understandably, when it is necessary to transfer the current from the main branch to the first thyristor, the pre-charge capacitor C0, the energy storage inductor L0, the second thyristor T2, and the primary side of the transformer M1 are turned on. A negative electromotive force is induced on the secondary side of the high-frequency transformer M1. This causes the current to transfer from the main branch to the first thyristor T1 through diodes D1 and D3 (or D2 and D4).

[0034] In some embodiments, the controller is further configured to control the fourth thyristor T4 to conduct after the current transfer of the main branch is completed, so as to charge the pre-charge capacitor.

[0035] Understandably, after the current transfer is completed, the fourth thyristor T4 is turned on, the C0-L0-T4 circuit is turned on, the high-frequency transformer M1 is taken out of operation, and the energy is reversed to charge the pre-charge capacitor C0.

[0036] In some embodiments, the controller is further configured to control the third thyristor T3 to conduct when the charging voltage of the pre-charge capacitor reaches a preset maximum value.

[0037] Understandably, when the pre-charge capacitor C0 reaches its maximum voltage, the C0-M1 primary side-T3 circuit is activated. Capacitor C0 discharges directly through the primary side of the high-frequency transformer M1, inducing an electromotive force on the secondary side that is much higher than the system voltage, thus interrupting the system current.

[0038] In some embodiments, the bridge circuit includes: a first diode D1, a second diode, a third diode D3, and a fourth diode D4; The cathode of the first diode D1 is connected to the cathode of the second diode, and the anodes of the first diode D1 and the second diode are respectively connected to the two ends of the main branch. The positive terminal of the third diode D3 is connected to the positive terminal of the fourth diode D4, and the negative terminals of the third diode D3 and the fourth diode D4 are respectively connected to the two ends of the main branch.

[0039] It is understood that the transfer branch consists of the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4, as well as the first thyristor. The first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 form a diode bridge. The diode bridge ensures that the current flowing into the first thyristor T1 always maintains the same direction.

[0040] The connection point between the first diode D1 and the second diode D2, and the connection point between the third diode D3 and the fourth diode D4, are the output terminals of the bridge circuit.

[0041] In some embodiments, refer to Figure 1 As shown, this invention proposes a coupled self-turn-off DC circuit breaker, comprising a main branch, a transfer branch, and a turn-off branch. The main branch consists of an ultra-fast mechanical switch S, which is based on the principle of electromagnetic repulsion. The transfer branch consists of a diode bridge (i.e., a bridge circuit composed of diodes) D1, D2, D3, D4, and a first thyristor T1. The diode bridge ensures that the current flowing into the first thyristor T1 always maintains the same direction. The turn-off branch includes a pre-charge capacitor C0, an energy storage inductor L0, a second thyristor T2, a third thyristor T3, a fourth thyristor T4, and a high-frequency transformer M1.

[0042] The cathode of the second thyristor T2, the anode of the third thyristor T3, the anode of the fourth thyristor T4, and one terminal of the primary side of the high-frequency transformer M1 are connected to the first node N1; the cathode of the fourth thyristor T4, the other terminal of the primary side of the high-frequency transformer M1, and the negative terminal of the pre-charge capacitor C0 are connected to the fourth node N4; the anode of the second thyristor T2 and one terminal of the energy storage inductor L0 are connected to the second node N2; the cathode of the third thyristor T3, the other terminal of the energy storage inductor L0, and the positive terminal of the pre-charge capacitor C0 are connected to the third node N3; the high-frequency transformer M1 is a step-up transformer, and its secondary side is connected in series with the first thyristor T1 of the transfer branch through the fifth node N5 and the sixth node N6, and is connected to a bridge circuit composed of diodes.

[0043] Under rated operating conditions, the ultra-fast mechanical switch S closes, carrying the system current. During short-circuit breaking, the control process is as follows: 1) First, send the ultra-fast mechanical switch S to open, and the moving and stationary contacts of the ultra-fast mechanical switch S open to a sufficient opening distance.

[0044] 2) Send the turn-on command for the second thyristor T2 and the first thyristor T1, activating the transfer branch and the turn-off branch. The primary side of C0-L0-T2-M1 is turned on. A negative electromotive force is induced on the secondary side of the high-frequency transformer M1. This causes the current to transfer from the main branch to the first thyristor T1 through diodes D1 and D3 (or D2 and D4).

[0045] 3) After the current transfer is completed, the fourth thyristor T4 is turned on, the C0-L0-T4 circuit is turned on, the high-frequency transformer M1 is taken out of operation, the negative induced electromotive force of the current transfer branch disappears, and the ultra-fast mechanical switch S is restored to its dielectric blocking characteristics. At the same time, sufficient energy can be reverse-charged into the pre-charge capacitor C0.

[0046] 4) When the voltage of the pre-charge capacitor C0 is detected and reaches its maximum value, the third thyristor T3 is turned on, and the C0-M1 primary side-T3 circuit is turned on. The capacitor C0 discharges directly through the primary side of the high-frequency transformer M1, and an electromotive force much higher than the system voltage is induced on the secondary side, causing the short-circuit current to drop to zero and the first thyristor T1 to turn off, thereby realizing the interruption of system current.

[0047] Compared with existing technologies, the present invention has the following beneficial technical effects: The circuit breaker of the present invention adopts the diode bridge current conduction principle, which ensures that the direction of the breaking current in the first thyristor T1 in the transfer branch remains consistent, avoiding a complex current detection system. Simultaneously, the turn-off branch of the present invention, on the one hand, achieves rapid transfer of fault current from the main branch to the first thyristor T1 in the transfer branch in medium / high voltage fields; on the other hand, by adopting the boost principle, it not only achieves zero-crossing self-turn-off of the current in the first thyristor T1, but also offsets the energy stored in the system inductor, reducing the energy absorption and consumption stage of the varistor used in traditional hybrid breaking technology, improving the reliability of breaking, and reducing the size and cost of the circuit breaker.

[0048] The present invention also provides a control method for a coupled self-turn-off DC circuit breaker, the control method being applied to the coupled self-turn-off DC circuit breaker described in any of the preceding claims, the control method comprising: During the disconnection process, a negative electromotive force is induced on the secondary side of the control transformer to transfer the current of the main branch to the first thyristor. After the current transfer in the main branch is completed, the transformer is controlled to exit operation and the control branch itself is charged. When the charging voltage reaches the preset maximum value, the primary side of the transformer is discharged to interrupt the current.

[0049] Reference Figure 2As shown, a disconnection method for a coupled self-turn-off DC circuit breaker includes the following steps: t 0~ t Phase 1: The system operates under rated current-carrying conditions, with the ultra-fast mechanical switch S closed, carrying the system current. i 0.

[0050] t At time 1, a short circuit fault occurs, and the current in the system rises rapidly. t At time 2, the system detected a short circuit fault and sent an ultra-fast mechanical switch S disconnect command.

[0051] t At time 3, the moving and stationary contacts of the ultra-fast mechanical switch S separate and move to the appropriate opening distance, turning on the second thyristor T2 and the first thyristor T1. The primary side of C0-L0-T2-M1 is turned on, and through the high-frequency transformer M1, an induced electromotive force with "negative at the top and positive at the bottom" is induced in the transfer branch, as referenced. Figure 2 As shown. Under the action of the induced electromotive force, the fault current is rapidly transferred from the ultra-fast mechanical switch S in the main branch to the first thyristor T1 through diodes D1 and D3 (or D2 and D4).

[0052] t At time 4, the current transfer is complete, the fourth thyristor T4 is turned on, the C0-L0-T2-T4 circuit is completed, and the high-frequency transformer M1 is taken out of operation. (Refer to...) Figure 3 As shown, t 4~ t In stage 5, the short-circuit current is carried by the first thyristor T1 in the transfer branch. The ultra-fast mechanical switch S recovers its dielectric blocking characteristics under near-zero voltage conditions. In the turn-off branch, the pre-charge capacitor C0 discharges through the energy storage inductor L0, and energy is reversed to charge the pre-charge capacitor C0.

[0053] t At time 5, the voltage across the pre-charge capacitor C0 reaches its maximum reverse value. Simultaneously, the ultra-fast mechanical switch S recovers its dielectric blocking characteristic, turning on the third thyristor T3. (Refer to...) Figure 4 As shown, the pre-charge capacitor C0 discharges directly through the primary side of the high-frequency transformer. Because the high-frequency transformer is a step-up transformer, an electromotive force (EMF) with "positive at the top and negative at the bottom" is quickly induced on the secondary side, and this EMF is much higher than the system voltage. The first thyristor T1 experiences a reverse voltage across its terminals, the current decreases, and it enters the self-turn-off process. t At time 6, the current across the first thyristor T1 drops to zero. Thereafter, the induced electromotive force on the secondary side of the high-frequency transformer is maintained, keeping the voltage across the first thyristor T1 in reverse for a period of time to ensure that the first thyristor T1 recovers its forward blocking characteristic and completes the short-circuit breaking. The corresponding current waveform during the short-circuit protection process of the coupled self-turn-off DC circuit breaker is as follows: Figure 5As shown.

[0054] As can be seen, the entire breaking process no longer requires the use of a varistor to absorb energy during short-circuit breaking, thereby reducing the number of breaking steps, the size and cost of the circuit breaker, and improving the reliability of short-circuit breaking. Simultaneously, it enables short-circuit breaking to be completed by controlling the medium- and high-voltage systems through the low-voltage system.

[0055] The coupled self-turn-off DC circuit breaker and its control method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A coupled self-turn-off type DC circuit breaker, characterized in that, include: Main branch circuit, including: control switch; A transfer branch, connected in parallel with the main branch, includes: a bridge circuit composed of diodes and a first thyristor; The shut-off branch includes: a transformer and a control branch connected to the transformer; the secondary side of the transformer is connected in series with the first thyristor between the two output terminals of the bridge circuit; The control branch is connected to the primary side of the transformer and is used to control the secondary side of the transformer to induce a negative electromotive force during the disconnection process, so as to transfer the current of the main branch to the first thyristor. After the current transfer of the main branch is completed, the transformer is controlled to stop operation and charge itself. When the charging voltage reaches the preset maximum value, the primary side of the transformer is discharged to disconnect the current.

2. The coupled self-turn-off DC circuit breaker according to claim 1, characterized in that, The control branch includes: a second thyristor, a third thyristor, a fourth thyristor, a pre-charge capacitor, and an energy storage inductor; The cathode of the second thyristor, the anode of the third thyristor, the anode of the fourth thyristor, and one pole of the primary side of the transformer are all connected to the first node; The cathode of the fourth thyristor, the other pole of the primary side of the transformer, and the negative pole of the pre-charge capacitor are all connected to the fourth node. The anode of the second thyristor and one pole of the energy storage inductor are connected together at the second node; The cathode of the third thyristor, the other pole of the energy storage inductor, and the positive pole of the pre-charge capacitor are all connected to the third node.

3. The coupled self-turn-off DC circuit breaker according to claim 2, characterized in that, Also includes: The controller is used to control the control switch to close under rated operating conditions and to control the control switch to open during short-circuit breaking.

4. The coupled self-turn-off DC circuit breaker according to claim 3, characterized in that, The controller is further configured to, after a target time has elapsed following the opening of the control switch, control the first thyristor and the second thyristor to conduct, so as to transfer the current of the main branch to the first thyristor.

5. The coupled self-turn-off DC circuit breaker according to claim 4, characterized in that, The controller is also configured to control the fourth thyristor to conduct after the current transfer in the main branch is completed, so as to charge the pre-charge capacitor.

6. The coupled self-turn-off DC circuit breaker according to claim 5, characterized in that, The controller is also used to control the third thyristor to conduct when the charging voltage of the pre-charge capacitor reaches a preset maximum value.

7. The coupled self-turn-off DC circuit breaker according to claim 1, characterized in that, The control switch is a mechanical switch.

8. The coupled self-turn-off DC circuit breaker according to claim 1, characterized in that, The bridge circuit includes: a first diode, a second diode, a third diode, and a fourth diode; The cathode of the first diode is connected to the cathode of the second diode, and the anodes of the first diode and the second diode are respectively connected to the two ends of the main branch. The positive terminal of the third diode is connected to the positive terminal of the fourth diode, and the negative terminals of the third diode and the fourth diode are respectively connected to the two ends of the main branch.

9. The coupled self-turn-off DC circuit breaker according to claim 1, characterized in that, The transformer is a step-up transformer.

10. A control method for a coupled self-turn-off DC circuit breaker, characterized in that, The control method is applied to the coupled self-turn-off type DC circuit breaker according to any one of claims 1-9, and the control method includes: During the disconnection process, a negative electromotive force is induced on the secondary side of the control transformer to transfer the current of the main branch to the first thyristor. After the current transfer in the main branch is completed, the transformer is controlled to exit operation and the control branch itself is charged. When the charging voltage reaches the preset maximum value, the primary side of the transformer is discharged to interrupt the current.

Images