CN214314550U - Multi-port direct current circuit breaker - Google Patents

Abstract

The utility model relates to the technical field of power electronics, in particular to a multi-port direct current breaker, which comprises a breaking unit, wherein one end of the breaking unit is connected with a direct current bus, and the breaking unit at least comprises a first power electronic switch unit; one end of each through-current branch is connected with the direct-current bus, each through-current branch at least comprises a first mechanical switch, and each through-current branch is used for controlling the on-off of a corresponding line; the auxiliary branch units are provided with auxiliary branch units which correspond to the through-current branches one by one, and two ends of each auxiliary branch unit are respectively connected with the other end of the cut-off unit and the other end of the through-current branch and used for assisting in conducting current in the switching-off and switching-on processes and isolating each circuit after switching-off; the auxiliary branch unit is provided with a first auxiliary branch and a second auxiliary branch, and the conduction directions of the first auxiliary branch and the second auxiliary branch are opposite. The using quantity of the full-control devices is saved by more than 50% by sharing the breaking units.

Description

Multi-port direct current circuit breaker

Technical Field

The utility model relates to a power electronics technical field, concretely relates to multiport direct current breaker.

Background

Nowadays, a direct current power transmission and distribution technology becomes an effective means for large-scale delivery and consumption of renewable energy sources such as wind, light and the like, and a high-voltage direct current breaker is a key device for developing the direct current power transmission and distribution to more economical and flexible networking.

With the development of high-voltage large-capacity direct-current power grids, the use number of the circuit breakers is increased, and the requirement for the breaking capacity of the circuit breakers is increased, so that the power grids have higher requirements for the technology and the economy of the high-voltage direct-current circuit breakers. The mechanical direct current circuit breaker is strong in breaking capacity and high in economical efficiency, but the small current breaking difficulty and the cost of the energy storage device caused by multiple reclosing requirements are greatly increased, and the improvement of the breaking capacity is restricted. The breaking capacity of the hybrid circuit breaker is limited by the inherent current-cutting capacity of the full-control device, and the adoption of a large number of full-control devices causes the circuit breaker to be high in cost.

Disclosure of Invention

In view of this, the embodiment of the present invention provides a multi-port dc circuit breaker to solve the balance problem between the breaking capacity and the manufacturing cost.

An embodiment of the utility model provides a multiport direct current breaker, include:

the switching-off unit is connected with the direct current bus at one end and at least comprises a first power electronic switch unit;

one end of each through-current branch is connected with the direct-current bus, each through-current branch at least comprises a first mechanical switch, and each through-current branch is used for controlling the on-off of a corresponding line;

the auxiliary branch units are provided with one-to-one correspondence between the auxiliary branch units and the through-flow branches, two ends of each auxiliary branch unit are respectively connected with the other end of the cut-off unit and the other end of the through-flow branch, and the auxiliary branch units are used for isolating each circuit; the auxiliary branch unit is provided with a first auxiliary branch and a second auxiliary branch, and the conduction directions of the first auxiliary branch and the second auxiliary branch are opposite.

The embodiment of the utility model provides a multiport direct current breaker can make full accuse device use quantity practice thrift more than 50% through the mode of sharing the unit of breaking, and adopts the mode that mechanical switch and power electronic switch unit combine to realize multiport direct current breaker, can realize that stable state and trouble break circuit under the operating mode voltage between keep apart, can reduce the isolation cost to the balance between capacity and the cost of breaking has been guaranteed.

Optionally, the disconnection unit includes a disconnection branch and an energy consumption branch connected in parallel, where the disconnection branch has the first power electronic switch unit;

the through-current branch further comprises a second power electronic switching unit in series with the first mechanical switch.

Optionally, the disconnection unit includes a disconnection branch and an energy consumption branch connected in parallel, where the disconnection branch further includes a negative voltage coupling switch connected in series with the first power electronic switch unit;

the current branch has the first mechanical switch.

Optionally, the negative pressure coupling switch includes: the capacitor is connected with the third power electronic switch in series and then connected with the primary side of the coupling reactor in series, and the secondary side of the coupling reactor is connected with the first power electronic switch unit in series.

Optionally, the energy consuming branch comprises a non-linear resistance unit.

Optionally, the auxiliary branch unit includes: a third power electronic switching unit or diode unit.

The embodiment of the utility model provides a multiport direct current breaker utilizes each supplementary branch road unit can independently break each circuit short-circuit current, possesses many outlet short-circuit fault simultaneously and breaks and direct current bus fault clearance ability simultaneously.

Optionally, the third power electronic switching unit comprises:

the first power electronic switch and the one-way choke switch are connected in series;

or the like, or, alternatively,

and the second power electronic switches are connected in series in sequence.

Optionally, the diode unit includes:

a first diode connected in series in sequence;

or the like, or, alternatively,

the diode unit includes:

at least two diode branches connected in parallel;

a fourth power electronic switch in series with the at least two diode branches after parallel connection.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a multi-port dc circuit breaker according to an embodiment of the present invention;

fig. 2a and 2c are schematic structural diagrams of a breaking branch according to an embodiment of the present invention;

fig. 2b and fig. 2d are schematic structural diagrams of through-flow branches according to an embodiment of the present invention;

fig. 3 a-3 c are schematic structural diagrams of a first auxiliary branch according to an embodiment of the present invention;

fig. 4 a-4 c are schematic mechanical views of a second auxiliary branch according to an embodiment of the present invention;

fig. 5 a-5 d are schematic structural views of a power electronic switch unit according to an embodiment of the present invention;

fig. 6 is a schematic structural diagram of a negative pressure coupling switch according to an embodiment of the present invention;

fig. 7 a-7 b are schematic structural diagrams of a multi-port dc circuit breaker according to an embodiment of the present invention;

fig. 8 a-8 b are schematic diagrams of a multi-port dc circuit breaker according to an embodiment of the present invention being put into operation;

fig. 9 a-9 e are schematic diagrams illustrating a process of opening and closing a multi-port dc circuit breaker when a short-circuit fault occurs in a line 1 according to an embodiment of the present invention;

fig. 10 a-10 e are schematic diagrams illustrating a multi-port dc circuit breaker opening process during a dc bus short-circuit fault according to an embodiment of the present invention;

11 a-11 b are schematic diagrams of the multi-port dc circuit breaker opening process during non-synchronous multi-pole fault according to an embodiment of the present invention;

fig. 12 a-12 b are schematic diagrams of a multi-port dc circuit breaker opening process upon failure of a first mechanical switch according to an embodiment of the present invention;

fig. 13 is a flowchart of a control method for a multi-port dc circuit breaker according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by the skilled in the art without creative work belong to the protection scope of the present invention.

The embodiment of the utility model provides a multiport direct current circuit breaker, including breaking unit, two at least through-flow branches and two at least supplementary branch road units. The auxiliary branch units are arranged in one-to-one correspondence with the through-flow branches.

As shown in fig. 1, the multi-port dc circuit breaker includes m current branches and m auxiliary branch units, and in this embodiment, no limitation is imposed on the specific value of m, and corresponding setting may be specifically performed according to actual conditions, and it is only necessary to ensure that the current branches and the auxiliary branch units are set in a one-to-one correspondence manner.

Specifically, m direct current lines are led out of the direct current bus, and a through-current branch is arranged on each direct current line. That is, one end of the through-flow branch is connected to the dc bus, and the other end is connected to one end of the cut-off unit through the corresponding auxiliary branch unit. Wherein, the other end of the breaking unit is connected with the direct current bus.

The on-off unit at least comprises a first power electronic switch unit, and other switch units can be combined on the basis of the first power electronic switch unit, and the like, so that specific circuit structures of the first power electronic switch unit and the other switch units are not limited at all, and the on-off unit can be controlled to be on-off correspondingly according to requirements. The first power electronic switch unit can be formed by adopting full-control devices such as IGBT, IGCT, BIGT and IEGT and is used for bearing and turning off load and short-circuit current in a short time. For the convenience of the following description, the first power electronic switching unit is referred to as the main breaker, denoted MB.

The through-current branch at least comprises a first mechanical switch which is used for controlling the on-off of the corresponding line. As shown in fig. 1, the throughflow branches are connected in series on the respective dc lines. In particular, the current branch is used to conduct the load current during normal operation of the dc system.

And two ends of the auxiliary branch unit are respectively connected with the cut-off unit and the through-current branch and are used for assisting in conducting current in the switching-off and switching-on processes and isolating each line after switching-off. As shown in fig. 1, the auxiliary branch unit has a first auxiliary branch and a second auxiliary branch, and the conduction directions of the first auxiliary branch and the second auxiliary branch are opposite. Specifically, the auxiliary branch unit is used for providing a path and voltage isolation between lines for current in the breaking process, the first auxiliary branch (also called as an upper auxiliary branch) is used for conducting the breaking unit to flow current to the direct current line, and the second auxiliary branch (also called as a lower auxiliary branch) is used for conducting the direct current line to flow current to the breaking unit. For convenience of description hereinafter, the first auxiliary branch is referred to as an upper auxiliary branch, and the second auxiliary branch is referred to as a lower auxiliary branch.

Taking the dc line 1 as an example, the corresponding amplitude branch unit has a first auxiliary branch 1 and a second amplitude branch 1, and two ends of the first auxiliary branch 1 and the second auxiliary branch 2 are respectively connected to the cut-off unit and the through-current branch 1.

The multiport direct current circuit breaker that this embodiment provided can make full accuse device use quantity practice thrift more than 50% through the mode of sharing the unit of breaking, and adopts the mode that mechanical switch and power electronic switch unit combine to realize multiport direct current circuit breaker, can realize the line voltage isolation under steady state and the trouble condition of breaking, can reduce the isolation cost to the balance between capacity and the cost of breaking has been guaranteed.

In some optional embodiments of the present embodiment, the disconnection unit includes a disconnection branch and an energy consumption branch connected in parallel, wherein the disconnection branch has a first power electronic switching unit. The on-off branch is used for bearing and switching off load and short-circuit current in short time; the energy consumption branch is used for limiting switching-off overvoltage and absorbing energy.

In particular, the energy consuming branch may comprise a non-linear resistance unit SA connected in parallel across the breaking branch. One end of the energy consumption branch and one end of the cut-off branch are connected with the direct current bus, and the other ends of the energy consumption branch and the cut-off branch are connected with the corresponding direct current circuit through the upper auxiliary branch and the lower auxiliary branch respectively and then are connected with two ends of the through current branch in parallel.

In the present exemplary embodiment, 2 alternative embodiments are provided for the disconnection branch and the current branch. Specifically, scheme 1: as shown in fig. 2a, the open branch has a first power electronic switching unit, i.e. MB; as shown in fig. 2b, the current-carrying branch comprises a second power electronic switching unit (i.e. LCS) in series with the first mechanical switch (i.e. UFD). Wherein the second power electronic switching unit may also be referred to as a current transfer switching unit.

Scheme 2: as shown in fig. 2c, the open branch comprises a first power electronic switching unit MB and a negative voltage coupling switch CNV connected in series; as shown in fig. 2d, the current branch has a first mechanical switch, which is denoted MS in fig. 2d for the purpose of distinguishing it from the first mechanical switch in fig. 2 b.

In the scheme 1, the current branch comprises a first mechanical switch UFD and a current transfer switch LCS connected in series, and the breaking branch is composed of a main circuit breaker MB composed of fully-controlled power electronic switch units. In the scheme 2, the through-current branch comprises a first mechanical switch MS, and the open-close branch is formed by connecting a main circuit breaker MB formed by a full-control power electronic switch unit and a negative-pressure coupling switch CNV in series.

Specifically, scheme 1 forces the current to be diverted to the disconnect branch using a current transfer disconnect LCS to latch the set-up voltage during the disconnect process. Scheme 2 mainly plays the effect of transfer current through the negative pressure coupling unit, utilizes its inductive discharge to pour into reverse current to the through-current branch road, forces the current to shift to the branch road of breaking, compares with scheme 1, and the through-current branch road in scheme 2 only has mechanical switch, and the conduction loss can be approximately neglected, has reduced the running cost of circuit breaker.

In some optional embodiments of this embodiment, the auxiliary branch unit comprises a third power electronic switch unit or a diode unit. That is, the auxiliary branch unit may form the third power electronic switch unit through various power electronic switches, or may form the diode unit through a combination of a plurality of diodes, and the specific structure of the auxiliary branch unit is not limited in this embodiment, and may be specifically set according to an actual situation.

Each auxiliary branch unit can independently cut off short-circuit current of each line, and the device has the capacity of simultaneously cutting off short-circuit faults of multiple outgoing lines and clearing faults of the direct-current bus.

The third power electronic switch unit may also include a first power electronic switch and a unidirectional main flow switch connected in series; or a second power electronic switch connected in series.

The diode unit may also include a first diode connected in series in sequence, or may include at least two diode branches connected in parallel and a fourth power electronic switch, where the fourth power electronic switch is connected in series with the at least two diode branches connected in parallel.

Based on this, the present embodiment proposes the structure of the upper and lower auxiliary branches in 3. Wherein, fig. 3 a-3 c show the structural schematic diagram of the upper auxiliary branch, and fig. 4 a-4 c show the structural schematic diagram of the lower auxiliary branch.

For the upper auxiliary branch, scheme 1: the system comprises a unidirectional choke switch UCBS and a first power electronic switch which are connected in series, wherein the first power electronic switch can be an auxiliary valve T;

scheme 2: the second power electronic switch is connected in series in sequence, and the second power electronic switch can adopt an auxiliary valve T;

scheme 3: the first diode is connected in series in sequence, and the first diode can adopt an auxiliary valve D.

For the lower auxiliary leg, scheme 1: the system comprises a unidirectional choke switch UCBS and a first power electronic switch which are connected in series, wherein the first power electronic switch can be an auxiliary valve T;

scheme 2: the second power electronic switch is connected in series in sequence, and the second power electronic switch can adopt an auxiliary valve T;

scheme 3: the power supply comprises a plurality of diode branches and a fourth power electronic switch which are connected in parallel, wherein the fourth power electronic switch is connected with the plurality of diode branches which are connected in parallel in series. The fourth power electronic switch may also adopt a common auxiliary valve T, and the diode in the diode branch may adopt an auxiliary valve D.

It should be noted here that, in case 1 in both the upper auxiliary branch and the lower auxiliary branch, the first power electronic switch is included, but the two first power electronic switches in the upper and lower auxiliary branches may be the same or different.

Likewise, for scenario 2 in both the upper and lower auxiliary branches, a second power electronic switch is included, but the two second power electronic switches in the upper and lower auxiliary branches may be the same or different.

In some optional embodiments of this embodiment, the main breaker MB and the second power electronic switch unit LCS may be formed by cascading the power electronic switch units shown in fig. 5a to 5d, and the power electronic switch units may adopt fully-controlled devices such as IGBT, IGCT, BIGT, IEGT, and the like.

As shown in fig. 6, the negative voltage coupling unit includes a coupling reactor, a capacitor, and a third power electronic switch. The third power electronic switch can be realized by a thyristor valve and can also be realized by other power electronic switches. In particular, the secondary side CR of the coupling reactor_CNVConnected in series with main relay MB in the open branch, primary side T_CNVAnd a capacitor C_CNVThyristor valve T_CNVAre connected in series to form a discharge loop. When the pre-charging of the capacitor reaches a target voltage value, a thyristor valve is triggered in the on-off process of the circuit breaker, the capacitor and the primary side of the coupling reactor form an oscillating discharge loop to generate discharge current, the secondary side reacts negative pressure and simultaneously generates current, reverse current is injected into the through-flow branch to enable the current of the first mechanical switch MS to be zero-cross on-off, and the current is assisted to be transferred to the on-off branch.

In some specific applications of this embodiment, taking two dc lines as an example, the current branch adopts the structure shown in fig. 2a, and the cut-off branch adopts the structure shown in fig. 2b, where MB and LCS are based on the diode full-bridge sub-module topology shown in fig. 5d, the upper auxiliary branch adopts the structure shown in fig. 3c, and the lower auxiliary branch adopts the structure shown in fig. 4 c. Based on this structure, the structure of the resulting multi-port dc circuit breaker is shown in fig. 7 a.

In other specific applications of this embodiment, taking two dc lines as an example, the current branch adopts the structure shown in fig. 2c, and the cut-off branch adopts the structure shown in fig. 2d, where MB and LCS are based on the diode full-bridge submodule topology in fig. 5d, the upper auxiliary branch adopts the structure shown in fig. 3c, and the lower auxiliary branch adopts the structure shown in fig. 4 c. Based on this structure, the structure of the resulting multi-port dc circuit breaker is shown in fig. 7 b.

Compared with a single hybrid circuit breaker scheme, the method for sharing the main circuit breaker provided by the embodiment of the utility model saves the using quantity of the full-control devices by more than 50%; furthermore, the voltage isolation between lines under the working conditions of steady state and fault breaking is realized by utilizing the unidirectional high-voltage thyristor valve and the low-voltage diode valve, the isolation cost is greatly reduced, and the overall cost is saved by at least more than 40% compared with the scheme of adopting an independent single hybrid direct-current circuit breaker. The embodiment of the utility model provides a still provide a control method based on foretell multiport direct current circuit breaker, as shown in figure 13, control method include:

and S11, acquiring the working state of the multi-port direct current breaker.

The working states of the multi-port direct current circuit breaker comprise operation, line short-circuit fault disconnection, direct current bus short-circuit fault disconnection, failure of a first mechanical switch in a short-circuit fault disconnected through-current branch and the like. The working state of the multi-port direct current circuit breaker can be automatically monitored or monitored by other equipment.

S12, switching the on-state of the disconnection unit, the corresponding current branch and the corresponding auxiliary branch unit based on the operation state.

The multi-port direct current circuit breaker switches the conduction states of the switching-on/off unit, the corresponding through-current branch circuit and the auxiliary branch circuit unit according to different working states of the multi-port direct current circuit breaker.

According to the control method of the multi-port direct current circuit breaker, the working state of the multi-port direct current circuit breaker is monitored, and the conducting states of each cut-off unit, the through-current branch circuit and the auxiliary branch circuit unit are correspondingly controlled according to the monitoring result, so that the short-circuit current can be rapidly transferred, limited and cut-off, and the cut-off current can reach dozens of kA.

When the multi-port dc breaker is put into operation, the step S12 includes:

(1) switching on a switching-off branch in the switching-off unit so as to enable current to flow through the switching-off unit;

(2) when a closing judgment condition is met, a first mechanical switch in the through-flow branch is closed, so that current flows from the through-flow branch.

Specifically, taking the multi-port dc breaker shown in fig. 7a as an example, the multi-port dc breaker is put into operation:

before the dc breaker is put into operation, the main breaker MB is switched on and the current flows through the breaking branch, as shown in fig. 8 a; after the switching-on judgment condition is met, a mechanical switch UFD of the through-flow branch is switched on, and a current transfer switch LCS is switched on; after the UFD is switched on, the load current flows through the through-current branch, as shown in fig. 8b, the multi-port dc circuit breaker is put into operation.

To better illustrate the faults involved in the embodiments of the present invention, the following description is given for each fault:

(1) single line failure: short circuit fault of single direct current line;

(2) fault of direct current bus: short circuit fault of the direct current bus;

(3) simultaneous multi-line fault: more than 1 common bus direct current lines have faults simultaneously, and the action principle is switched off along with the fault of a single line corresponding to more than 1 through current branch circuits acting simultaneously;

(4) asynchronous line fault: more than 1 common bus direct current line has faults, and the fault time difference is smaller than the fault clearing time of a single line, namely, the subsequent faults still occur in the clearing process of the previous fault, and the action principle of the subsequent faults is different from that of the faults of multiple lines in the same period;

(5) fault clearance under failsafe: a fault occurs in the dc line and the first mechanical switch of the corresponding through-current branch fails.

When a fault occurs on the line side of the dc circuit breaker, that is, when the predetermined line short-circuit fault is open, taking a single-pole line fault as an example, the step S12 includes:

(1) switching on a switching unit in the switching-off branch and locking a first preset through-current branch corresponding to the preset line so as to force current to be transferred to the switching-off branch and the first auxiliary branch;

(2) when the current of the first preset through-current branch passes through zero, a first mechanical switch in the first preset through-current branch is switched off;

(3) latching the open branch and charging a capacitor in the open branch to transfer the current to the energy consuming branch;

(4) and when the voltage of the energy consumption branch circuit is higher than that of the multi-port direct current circuit breaker, the current of the first preset through current branch circuit is switched on and off.

Specifically, taking the multi-port dc circuit breaker shown in fig. 7a as an example, when the dc line 1 is disconnected due to a short-circuit fault, the multi-port dc circuit breaker receives a disconnection command or an overcurrent protection action, turns on the disconnection branch MB, and locks the LCS1 in the current branch 1 to force the current to be transferred to the disconnection branch, as shown in fig. 9 a; after the current of the current branch 1 crosses zero, the current is fed to the short-circuit point through the diode valve of the cut-off branch MB and the upper current branch 1, and the UFD1 is opened to achieve the voltage-resistant open distance, as shown in fig. 9 b; after the UFD1 reaches the withstand voltage separation distance, the main breaker MB is closed, the current charges the capacitor in the full bridge module, as shown in fig. 9c, the voltage rises to the parallel MOV, and the current is transferred to the MOV for circulation, as shown in fig. 9 d; when the MOV voltage is higher than the system dc voltage, the short circuit current continuously drops to zero crossing, the circuit breaker completes the current breaking, and the current branch UFD1 and the breaking branch MB and the corresponding auxiliary switches isolate the faulty line, as shown in fig. 9 e.

After the breaker is opened, the breaker can be quickly reclosed according to the requirements of a power grid system, and the reclosing operation process is similar to the closing process.

When the same-phase multi-pole line fault occurs on the line side of the direct current breaker, namely when a plurality of line short-circuit faults are on and off at the same time, the control method is the same as the control principle of the single-pole line fault. Specifically, the same principle of the preset line short-circuit fault disconnection control as described above is different in that a plurality of failed lines are controlled simultaneously in the case of a simultaneous multi-line fault. For details, please refer to the above description, which is not repeated herein.

When the dc bus short-circuit fault is open, S12 includes:

(1) switching on a switching unit in the switching-off branch and locking each through-current branch to force current to be transferred to the switching-off branch and the second auxiliary branch;

(2) when the current of each current branch passes through zero, a first mechanical switch in each current branch is switched off;

(3) latching the open branch and charging a capacitor in the open branch to transfer the current to the energy consuming branch;

(4) and when the voltage of the energy consumption branch circuit is higher than that of the multi-port direct current circuit breaker, the current of each through-current branch circuit is switched on and off.

Specifically, taking the multi-port dc circuit breaker shown in fig. 7a as an example, the principle of breaking when the power supply side of the dc circuit breaker fails is the same as the principle of breaking when the line side fails, except that the lower auxiliary valve Tl needs to be turned on to provide a path for short-circuit current during the breaking process, which is shown in fig. 10a to 10 e.

Further, when the line in which the second predetermined current branch is located is short-circuited and the first mechanical switch in the second predetermined current branch fails, the step S12 includes:

(1) keeping the second preset current branch on, and conducting the second auxiliary branch;

(2) latching the other current branches and the first auxiliary branch to force current to be transferred to the second preset current branch and the second auxiliary branch;

(3) when the current of the rest of the through-current branches passes through zero, the first mechanical switches of the rest of the through-current branches are switched off and the cut-off branches are locked, so that the isolation of the rest of the through-current branches is completed.

Specifically, taking the multi-port dc circuit breaker shown in fig. 7a as an example, taking the first mechanical switch UFD1 in line 1 as an example of failure and short-circuit fault in line 1 as an example, UFD1 cannot be opened due to the fault during the opening process, as shown in fig. 11 a. And keeping the LCS1 conductive, and triggering the lower auxiliary valve Tl, the locking LCS2 and the one-way choke switch UCBS 1. The current is transferred to the lower auxiliary valve Tl-MB-through-flow branch 1 for circulation, UFD2 is opened after the current of the through-flow branch 2 crosses zero, and MB is locked after UFD2 is opened in place, and the line 2 is isolated, as shown in fig. 11 b. The UFD malfunction protection function ensures that a multiport circuit breaker can effectively isolate a sound line after UFD malfunction.

When the line short-circuit fault where the at least two preset current branches are located is disconnected in the non-synchronous period, where the non-synchronous period is that a time difference between occurrence moments of the line short-circuit fault where the at least two preset current branches are located is smaller than clearing time of a single fault, that is, a subsequent fault still occurs in a clearing process of a previous fault, S12 includes:

(1) when a line where a third preset through-current branch is located has a fault at a first moment, locking the third preset through-current branch so as to enable current to flow to the cut-off branch through a corresponding first auxiliary branch;

(2) a first mechanical switch for opening the third preset through-current branch;

(3) when a line where a fourth preset through-current branch is located has a fault at a second moment, locking the fourth preset through-current branch so that current flows to the cut-off branch through the corresponding first auxiliary branch;

(4) and the first mechanical switch of the fourth preset through-current branch is switched off.

Specifically, also taking the multi-port dc circuit breaker shown in fig. 7a as an example, if the pole line 1 is shorted to ground at time 0, LCS1 is locked, and the current flows through the open branch, so the UFD1 is switched off. At the time of + δ T, the pole line 2 is grounded and shorted, as shown in fig. 12a, at this time, the LCS2 is locked only according to the conventional breaking process, and the UFD2 is switched off after the current of the current branch 2 crosses zero, as shown in fig. 12b, the breaking is completed after the breaking branch MB is locked. The fault clearing and isolation of the multipolar line short circuit continuous fault in a short time interval (ms level) can be realized through the design of the auxiliary branch circuit, and the isolation is carried out by utilizing a diode valve and a shared thyristor valve, so that the equipment cost is greatly reduced.

It should be noted that the line in which the current branch is located refers to the dc line to which the current branch is connected.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims (8)

1. A multi-port dc circuit breaker, comprising:

the switching-off unit is connected with the direct current bus at one end and at least comprises a first power electronic switch unit;

one end of each through-current branch is connected with the direct-current bus, each through-current branch at least comprises a first mechanical switch, and each through-current branch is used for controlling the on-off of a corresponding line;

the auxiliary branch units are provided with the auxiliary branch units which correspond to the through-current branches one by one, two ends of each auxiliary branch unit are respectively connected with the other end of the cut-off unit and the other end of the through-current branch, and the auxiliary branch units are used for assisting in conducting current and isolating each line after switching-off in the switching-off and switching-on processes; the auxiliary branch unit is provided with a first auxiliary branch and a second auxiliary branch, and the conduction directions of the first auxiliary branch and the second auxiliary branch are opposite.

2. The multi-port dc circuit breaker according to claim 1, wherein the breaking unit comprises a breaking branch and a power consuming branch in parallel, wherein the breaking branch has the first power electronic switching unit;

the through-current branch further comprises a second power electronic switching unit in series with the first mechanical switch.

3. The multi-port dc circuit breaker according to claim 1, wherein the breaking unit comprises a breaking branch and a power consuming branch in parallel, wherein the breaking branch further comprises a negative voltage coupling switch in series with the first power electronic switching unit;

the current branch has the first mechanical switch.

4. The multi-port dc circuit breaker of claim 3, wherein the negative coupling switch comprises: the capacitor is connected with the third power electronic switch in series and then connected with the primary side of the coupling reactor in series, and the secondary side of the coupling reactor is connected with the first power electronic switch unit in series.

5. The multi-port dc circuit breaker according to claim 3, wherein the energy dissipating branch comprises a non-linear resistance unit.

6. The multi-port dc circuit breaker according to any of claims 1-3, wherein the auxiliary branch unit comprises: a third power electronic switching unit or diode unit.

7. The multi-port dc circuit breaker according to claim 6, wherein the third power electronic switching unit comprises:

the first power electronic switch and the one-way choke switch are connected in series;

or the like, or, alternatively,

and the second power electronic switches are connected in series in sequence.

8. The multi-port dc circuit breaker according to claim 6, wherein the diode unit comprises:

a first diode connected in series in sequence;

or the like, or, alternatively,

the diode unit includes:

at least two diode branches connected in parallel;

a fourth power electronic switch in series with the at least two diode branches after parallel connection.

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