WO2022246976A1 - 多端直流输电系统的直流断路器 - Google Patents

多端直流输电系统的直流断路器 Download PDF

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Publication number
WO2022246976A1
WO2022246976A1 PCT/CN2021/105376 CN2021105376W WO2022246976A1 WO 2022246976 A1 WO2022246976 A1 WO 2022246976A1 CN 2021105376 W CN2021105376 W CN 2021105376W WO 2022246976 A1 WO2022246976 A1 WO 2022246976A1
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Prior art keywords
switch
current
circuit breaker
transmission line
voltage
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PCT/CN2021/105376
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English (en)
French (fr)
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何竞松
彭光强
武霁阳
王越杨
毛炽祖
陈礼昕
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中国南方电网有限责任公司超高压输电公司检修试验中心
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Publication of WO2022246976A1 publication Critical patent/WO2022246976A1/zh

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Definitions

  • the present application relates to the technical field of multi-terminal direct current transmission, in particular to a direct current circuit breaker of a multi-terminal direct current transmission system.
  • HVDC circuit breaker is an important equipment of multi-terminal DC transmission system and DC grid. It can break the DC fault current as needed, isolate the faulty DC line and converter station, and provide the necessary guarantee for the safe, reliable and stable operation of the DC grid.
  • the existing high-voltage DC circuit breakers are all composed of a steady-state flow branch, a current transfer branch, and an energy absorption branch connected in parallel in terms of realization principles.
  • the current transfer branch and the steady-state flow branch realize DC current under different working conditions.
  • a large number of surge arresters are used in the breaking and energy absorption branches to solve the problem of overvoltage tolerance and high energy absorption during the breaking process.
  • the parallel connection of the above three branches is not only complicated in structure, but also very inconvenient to maintain.
  • a DC circuit breaker comprising: a transformer, a first switch, a second switch and a signal acquisition module, the secondary winding of the transformer and the first switch are both arranged on a power transmission line, and the primary winding of the transformer passes through the
  • the second switch is connected to the AC grid
  • the signal acquisition module is connected to and collects the first voltage of the primary winding, the second voltage of the AC grid, and the current of the secondary winding;
  • the first switch When the power transmission line is in a normal operating state, the first switch is closed and the second switch is open; when the power transmission line is in a fault state and the difference between the second voltage and the first voltage satisfies
  • the threshold When the threshold is turned off, the second switch is turned on, and when the current decreases and reaches the current threshold, both the first switch and the second switch are turned off.
  • the signal acquisition module includes a voltage acquisition module and a current acquisition module, the voltage acquisition module is respectively connected to both ends of the second switch, and the current acquisition module is connected to the secondary winding.
  • the current threshold is a safe current that allows disconnection of the transmission line to eliminate the fault.
  • the transformer includes an iron core, a primary winding and a secondary winding, both of the primary winding and the secondary winding are wound on the iron core, and the input end of the primary winding is connected to the An AC grid, the output end of the primary winding is connected to the AC grid through the second switch, and the secondary winding is connected to the transmission line after being connected in series with the first switch.
  • the first switch is a first AC contactor
  • the coil of the first AC contactor is connected to the control module
  • the contacts of the first AC contactor are arranged on the power transmission line.
  • the second switch is a second AC contactor
  • the coil of the second AC contactor is connected to the control module
  • one end of the contact of the second AC contactor is connected to the transformer
  • the other end of the contact of the second AC contactor is connected to the AC grid.
  • a multi-terminal DC power transmission system includes the DC circuit breaker described in any one of the above.
  • the multi-terminal DC power transmission system further includes a control module and a transmission line, the control module is connected to the DC circuit breaker, and the DC circuit breaker is arranged on the transmission line.
  • the multi-terminal direct current transmission system further includes a converter station, the input end of the converter station is connected to the AC grid, and the output end of the converter station is connected to the DC grid through the transmission line.
  • the number of the DC circuit breakers and the number of the converter stations are consistent with the number of the power transmission lines, and the input terminals of each converter station are Connect the AC power grid, the input end of each transmission line is connected to one of the converter stations, the output end of each transmission line is connected to the DC power grid, and the output end of each transmission line is also correspondingly provided with a DC circuit breaker , each of the DC circuit breakers is also connected to the control module.
  • the DC circuit breaker of the above-mentioned multi-terminal DC transmission system transfers the energy of the fault current to the AC grid through the electromagnetic induction principle of the transformer and controls the switching of the two switching elements at an appropriate time, and can automatically suppress the fault at the initial stage.
  • Fault current the principle is simple and reliable, avoiding the use of multi-branch parallel structure and lightning arresters and other equipment, reducing equipment complexity and maintenance difficulty.
  • Fig. 1 is a topological diagram of a DC circuit breaker in an embodiment
  • Fig. 2 is a topological diagram of a DC circuit breaker in the prior art
  • Fig. 3 is a schematic diagram of a DC circuit breaker in a normal flow stage in an embodiment
  • Fig. 4 is a schematic diagram of the DC circuit breaker in the self-inductance current suppression stage in an embodiment
  • Fig. 5 is a schematic diagram of the DC circuit breaker in the forced current suppression stage in an embodiment
  • Fig. 6 is a schematic diagram of a DC circuit breaker in a fault disconnection stage in an embodiment
  • Fig. 7 is a topology diagram of a multi-terminal direct current transmission system in an embodiment.
  • first, second and the like used in this application may be used to describe various elements herein, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element.
  • a first resistance could be termed a second resistance, and, similarly, a second resistance could be termed a first resistance, without departing from the scope of the present application.
  • Both the first resistance and the second resistance are resistances, but they are not the same resistance.
  • connection in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have the transmission of electric signals or data between each other.
  • the current at the opening is zero, and the arc is extinguished. Subsequently, the short-circuit current is transferred to the current transfer branch to charge the capacitor C.
  • the MOA of the arrester operates, and the fault current is transferred to the MOA of the arrester (energy absorption branch). After the absorption is completed, the current becomes zero, and the breaking process of the high-voltage DC circuit breaker ends.
  • the existing high-voltage DC circuit breakers all need to include multiple branch structures.
  • current transfer branches are required to create current zero-crossing points to eliminate arcs, and when the DC capacity is large, a large number of arrester equipment is also required. For energy absorption, resulting in a complex structure of the device.
  • the present application proposes a DC circuit breaker 10, as shown in FIG.
  • a switch 120 is arranged on the transmission line, the primary winding of the transformer 110 is connected to the AC grid through the second switch 120, and the signal acquisition module 140 is connected to and collects the first voltage of the primary winding, the second voltage of the AC grid, and the current of the secondary winding;
  • the first switch 120 is closed and the second switch 130 is open;
  • the second switch 130 is closed , and when the current decreases and reaches the current threshold, both the first switch 120 and the second switch 130 are turned off.
  • the transformer 110 is a device that uses the principle of electromagnetic induction to change the AC voltage, and includes two sets of coils wound with wires, and interacts with each other in an inductive manner.
  • an alternating current flows in one set of coils
  • an alternating voltage with the same frequency will be induced in the other set of coils, and the magnitude of the induced voltage depends on the strength of the magnetic induction of the two coils.
  • the principle of electromagnetic induction when the AC current flowing through the coil is greater, the magnetic induction intensity induced on the other side is greater, and the induced AC voltage is also greater. In one embodiment, as shown in FIG.
  • the transformer 110 can be a single-phase transformer, including an iron core, a primary winding and a secondary winding, the primary winding and the secondary winding are both wound on the iron core, and the input end of the primary winding is connected to
  • the output end of the primary winding is connected to the AC grid through the second switch 130 , and the secondary winding is connected in series with the first switch 120 to connect to the transmission line.
  • the signal collection module 140 is connected to the primary winding of the transformer 110 and collects its first voltage as a basis for judging whether the transmission line is faulty. Specifically, in the normal operation state of the transmission line, a DC current flows on it, and a DC voltage flows through the secondary winding of the transformer 110, and no induced voltage is generated in the primary winding, so in the normal operation state of the transmission line , the first voltage of the primary winding collected by the signal acquisition module 140 is zero; and when a ground fault occurs on the transmission line, the fault current flowing through the secondary winding side is in the opposite direction to the normal current. The self-inductance electromotive force is generated in the winding, and then the self-induction electromotive force will also induce a voltage on the primary winding.
  • the fault threshold is a voltage greater than zero, which can be set according to actual conditions.
  • the second voltage of the AC power grid collected by the signal collection module 140 is used as a basis for judging when to suppress the fault current.
  • the second switch 130 is closed to connect the primary winding of the transformer 110 to the AC power grid, and induce a reverse suppression electromotive force to the secondary winding of the transformer 110, so as to Counteracts the fault current flowing in the secondary winding.
  • the cut-off threshold can be set according to the actual situation, it can be a value close to zero, or it can be set to zero, it is not limited to this, as long as it can ensure that the pressure difference between the two ends of the second switch 130 is small, The second switch 130 will not be damaged.
  • the current collected by the signal collection module 140 connected to the secondary winding of the transformer 110 can be used as a basis for judging whether to disconnect the first switch 120 and the second switch 130 to cut off the transmission line and the AC grid to isolate the fault point.
  • the first switch 120 is arranged on the transmission line for connecting and disconnecting the transmission line, and the first switch 120 also judges whether the connection needs to be disconnected according to the current of the secondary winding collected by the signal collection module 140 .
  • the first switch 120 When the power transmission line is in a normal operating state, the first switch 120 is always in a closed state, and the direct current is transmitted through the power transmission line. And when the ground fault occurs on the transmission line and the current drops to the threshold, the first switch 120 is turned off to disconnect the fault point on the transmission line.
  • the second switch 130 is also turned off, the primary winding of the transformer 110 is disconnected from the AC grid, and the faulty transmission line is completely isolated.
  • the current threshold is a safe current that allows the disconnection of the transmission line to eliminate the fault, which can be determined according to the parameters of the first switch 120.
  • the current threshold is turned off, the first switch 120 can be guaranteed not to damage the first switch. 120 and the impact is minimal, it can be set to zero, or it can be set to a small current value close to zero.
  • the way of closing and opening the first switch 120 and the second switch 130 is not unique, and can be determined according to the application scenario of the DC circuit breaker of the present application.
  • the first switch 120 and the second switch 130 can be switching elements that are manually opened and closed, and the signal acquisition module 140 is connected to the display device and the alarm device of the control center through a digital-to-analog conversion circuit.
  • the technicians in the control center find and operate the first switch 120 and the second switch 130 accordingly to complete the transmission line fault isolation operation.
  • the first switch 120 and the second switch 130 can also be automatic control switching elements, and the first switch 120, the second switch 130 and the signal
  • the acquisition modules 140 are all connected to the control module in the system, and the control module automatically controls the switching elements to perform corresponding actions according to the fed-back data, so as to complete the transmission line fault isolation.
  • the above-mentioned DC circuit breaker transfers the energy of the fault current to the AC grid through the electromagnetic induction principle of the transformer and controls the switching of the two switching elements at an appropriate time, and can automatically suppress the fault current by generating a self-induced electromotive force at the initial stage of the fault ,
  • the principle is simple and reliable, avoiding the use of multi-branch parallel structure and lightning arresters and other equipment, reducing equipment complexity and maintenance difficulty.
  • the signal acquisition module 140 includes a voltage acquisition module and a current acquisition module, the voltage acquisition module is connected to both ends of the second switch 130 , and the current acquisition module is connected to the secondary winding.
  • the voltage collection module is connected to both ends of the second switch 130, and collects the first voltage of the primary winding and the second voltage of the AC grid, as the basis for judging whether a fault occurs on the transmission line and when to suppress the fault current.
  • the current collection module is connected to the secondary winding of the transformer 110 and collects its current as a basis for judging whether it is necessary to disconnect the first switch 120 and the second switch 130 to cut off the transmission line and the AC grid to isolate the fault point.
  • the voltage acquisition module and the current acquisition module can be analog acquisition modules with communication functions, and can be respectively connected to the two ends of the second switch 130 and the secondary winding to acquire voltage and Current, and then transmit the collected data through the communication interface on the analog quantity acquisition module for related operations.
  • the voltage acquisition module and the current acquisition module can also be composed of a voltage or current sensor and a digital-to-analog conversion circuit. The voltage or current is collected by the voltage or current sensor and then the collected data is transmitted through the digital-to-analog conversion circuit for related operations.
  • the embodiment is not limited thereto.
  • the voltage and current values of the transformer 110 are respectively collected by the signal collection module 140 as the judgment basis, which provides a data basis for the DC circuit breaker to break the fault on the transmission line.
  • the first switch 120 and the second switch 130 are control switches with control terminals connected to the control module in the system.
  • the first switch 120 is a first AC contactor
  • the coil of the first AC contactor is connected to the control module
  • the contacts of the first AC contactor are arranged on the power transmission line.
  • the AC contactor is a device that uses electromagnetic force and spring force to achieve the conduction and disconnection of the contacts.
  • the static iron core When the coil is energized, the static iron core generates electromagnetic attraction, the armature is attracted, and the armature is connected.
  • the connecting rod drives the contact to move, so that the normally closed contact is disconnected, and the contactor is in the energized state; when the coil is de-energized, the electromagnetic attraction disappears, the armature is reopened, the normally open contact is closed, and the contactor is released under the action of the bit spring , all contacts are reset accordingly, and the contactor is in a de-energized state.
  • the coil of the first AC contactor is used as the control terminal to connect the control module in the system.
  • the control module powers off the coil of the first AC contactor to make the first
  • the contacts of the AC contactor connected in series to the transmission line are disconnected to break off the fault point on the transmission line.
  • the second switch 130 is a second AC contactor
  • the coil of the second AC contactor is connected to the control module
  • one end of the contact of the second AC contactor is connected to the primary winding of the transformer.
  • the other end of the contact of the second AC contactor is connected to the AC grid.
  • the coil of the second AC contactor is used as the control terminal to connect to the control module in the system.
  • the control module sends a signal to the second AC contactor.
  • the coil of the transformer is energized, so that the primary winding of the transformer is connected to the circuit of the AC grid through the contact of the second AC contactor, and the fault current is suppressed.
  • the control module powers off the coil of the second AC contactor, so that the primary winding of the transformer is connected to the AC grid circuit through the contacts of the second AC contactor. , breaking the fault point on the transmission line.
  • the converter station transmits the DC current to the DC grid through the transmission line.
  • the DC circuit breaker includes a transformer, AC circuit breaker A and AC circuit breaker B, the secondary winding of the transformer and AC circuit breaker A are set on the transmission line, and the primary winding of the transformer is connected through AC circuit breaker B AC power grid, the terminal of AC circuit breaker B connected to the AC grid is terminal K1, the terminal of AC circuit breaker B connected to the primary winding of the transformer is terminal K2, the first voltage is the voltage of terminal K2, and the second voltage is the voltage of terminal K1, its working process Can include the following four stages:
  • Stage 1 Normal circulation stage.
  • Stage 2 self-inductance suppression flow stage.
  • Stage 3 Forced suppression stage.
  • Phase 4 Fault disconnection phase.
  • the energy of the fault current 2 is basically released, and the AC circuit breaker A and AC circuit breaker B are disconnected to isolate the ground fault point.
  • the energy of the fault current is transferred to the AC grid through the principle of electromagnetic induction of the transformer and the switching of the two AC contactors at an appropriate time, and the fault current can be automatically suppressed at the initial stage of the fault.
  • the principle is simple and reliable, avoiding the use of multi-branch parallel structure and lightning arresters and other equipment, reducing the complexity and maintenance difficulty of DC circuit breakers.
  • a multi-terminal DC power transmission system including the DC circuit breaker 10 in any one of the above items.
  • the multi-terminal DC power transmission system further includes a control module 20 and a transmission line, the control module 20 is connected to a DC circuit breaker 10 , and the DC circuit breaker 10 is arranged on the transmission line.
  • control module 20 is connected to the control terminal of the AC circuit breaker A of the DC circuit breaker 10 and the control terminal of the AC circuit breaker B of the DC circuit breaker 10, and the secondary winding of the transformer of the DC circuit breaker 10 is connected to the contact of the AC circuit breaker A.
  • the head is set on the transmission line.
  • the control module 20 controls the opening and closing states of the AC circuit breaker A and the AC circuit breaker B according to the first voltage, the second voltage and the current fed back by the signal acquisition module of the DC circuit breaker 10, so as to break the transmission line The purpose of connecting the upper ground fault point to the DC grid.
  • the fault current is cut off by the DC circuit breaker 10 so that the fault part cannot continue to transmit power to the DC grid, which can greatly shorten the recovery time after the fault.
  • the multi-terminal direct current transmission system further includes a converter station 30, the input end of the converter station 30 is connected to the AC grid, and the output end of the converter station 30 is connected to the DC grid through a transmission line.
  • the converter station 30 is a station for converting alternating current into direct current or converting direct current into alternating current.
  • the converter station 30 converts the AC power in the AC grid into DC power and then transmits it to the DC grid through the transmission line.
  • the fault current 1 from the converter station is eliminated by the control and protection system of the converter station 30 in a timely manner, and does not belong to the working area of the DC circuit breaker 10 .
  • the number of DC circuit breakers 10 and the number of converter stations 30 are consistent with the number of power transmission lines, and the input end of each power transmission line is connected to a converter station 30 correspondingly, and each power transmission line The output ends of the lines are all connected to the DC power grid, and a DC circuit breaker 10 is correspondingly arranged at the output end of each transmission line, and each DC circuit breaker 10 is also connected to the control module 20 .
  • the multi-terminal direct current transmission system is composed of three or more converter stations 30 and transmission lines connecting the converter stations 30 .
  • a DC circuit breaker 10 is provided, so that multiple AC power sources can stably and safely supply power to multiple load centers.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Driving Mechanisms And Operating Circuits Of Arc-Extinguishing High-Tension Switches (AREA)
  • Direct Current Feeding And Distribution (AREA)

Abstract

本申请涉及一种直流断路器，包括：变压器、第一开关、第二开关与信号采集模块，变压器的二次绕组与第一开关设置于输电线路，变压器的一次绕组通过第二开关连接交流电网，信号采集模块连接并采集一次绕组的第一电压、交流电网的第二电压与二次绕组的电流；在输电线路为正常运行状态时，第一开关闭合，第二开关断开；在输电线路为故障状态且第二电压与第一电压的差值满足关断阈值时，第二开关闭合，以及在电流降低并达到电流阈值时，第一开关与第二开关均断开，能将故障电流的能量转移至交流电网，且在故障初期就自动抑制故障电流，断开故障点的原理简单可靠，避免了采用多支路的并联结构以及避雷器等设备，降低了设备复杂度以及维护难度。

Description

多端直流输电系统的直流断路器 技术领域
本申请涉及多端直流输电技术领域，特别是涉及一种多端直流输电系统的直流断路器。
背景技术
高压直流断路器是多端直流输电系统和直流电网的重要设备，能按需要分断直流故障电流，隔离出现故障的直流线路和换流站，为直流电网的安全可靠稳定运行提供必要的保障。
现有的高压直流断路器在实现原理上均由稳态通流支路、电流转移支路及能量吸收支路并联组成，电流转移支路与稳态通流支路实现不同工况下直流电流的分断，能量吸收支路采用大量避雷器设备用以解决开断过程中产生的过电压耐受问题和高额能量吸收问题，以上三条支路并联的形式不仅结构复杂，维护也十分不便。
发明内容
基于此，有必要针对现有问题，提供一种没有复杂多支路结构的多端直流输电系统的直流断路器。
一种直流断路器，包括：变压器、第一开关、第二开关与信号采集模块，所述变压器的二次绕组与所述第一开关均设置于输电线路，所述变压器的一次绕组通过所述第二开关连接交流电网，所述信号采集模块连接并采集所述一次绕组的第一电压、所述交流电网的第二电压与所述二次绕组的电流；
在所述输电线路为正常运行状态时，所述第一开关闭合，所述第二开关断开；在所述输电线路为故障状态且所述第二电压与所述第一电压的差值满足关断阈值时，所述第二开关闭合，以及在所述电流降低并达到电流阈值时，所述第一开关与所述第二开关均断开。
在其中一个实施例中，所述信号采集模块包括电压采集模块与电流采集模块，所述电压采集模块分别连接所述第二开关的两端，所述电流采集模块连接所述二次绕组。
在其中一个实施例中，所述电流阈值为允许断开所述输电线路以消除故障的安全电流。
在其中一个实施例中，所述变压器包括铁芯、一次绕组与二次绕组，所述一次绕组与所述二次绕组均缠绕在所述铁芯上，所述一次绕组的输入端连接所述交流电网，所述一次绕组的输出端通过所述第二开关连接所述交流电网，所述二次绕组与所述第一开关串联后接入所述输电线路。
在其中一个实施例中，所述第一开关为第一交流接触器，所述第一交流接触器的线圈连接控制模块，所述第一交流接触器的触头设置于所述输电线路。
在其中一个实施例中，所述第二开关为第二交流接触器，所述第二交流接触器的线圈连接所述控制模块，所述第二交流接触器的触头的一端连接所述变压器的一次绕组，所述第二交流接触器的触头的另一端连接所述交流电网。
一种多端直流输电系统，包括上述任意一项中所述的直流断路器。
在其中一个实施例中，上述多端直流输电系统还包括控制模块和输电线路，所述控制模块连接所述直流断路器，所述直流断路器设置于所述输电线路。
在其中一个实施例中，上述多端直流输电系统还包括换流站，所述换流站的输入端连接交流电网，所述换流站的输出端通过所述输电线路连接直流电网。
在其中一个实施例中，上所述输电线路为三条以上，所述直流断路器的数量和所述换流站的数量与所述输电线路的数量一致，各所述换流站的输入端均连接所述交流电网，各条输电线路的输入端对应连接一个所述换流站，各条输电线路的输出端均连接直流电网，各条输电线路的输出端还对应设置一个所述直流断路器，各所述直流断路器还均连接所述控制模块。
上述多端直流输电系统的直流断路器，通过变压器的电磁感应原理，以及在适当的时候控制两个开关元件的开闭状态切换将故障电流的能量转移至交流电网，且能在故障初期就自动抑制故障电流，原理简单可靠，避免了采用多支路的并联结构以及避雷器等设备，降低了设备复杂度以及维护难度。
附图说明
图1为一实施例中直流断路器的拓扑图；
图2为一现有技术中直流断路器的拓扑图；
图3为一实施例中直流断路器在正常流通阶段的示意图；
图4为一实施例中直流断路器在自感抑流阶段的示意图；
图5为一实施例中直流断路器在强制抑流阶段的示意图；
图6为一实施例中直流断路器在故障断开阶段的示意图；
图7为一实施例中多端直流输电系统的拓扑图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。
可以理解，本申请所使用的术语“第一”、“第二”等可在本文中用于描述各种元件，但这些元件不受这些术语限制。这些术语仅用于将第一个元件与另一个元件区分。举例来说，在不脱离本申请的范围的情况下，可以将第一电阻称为第二电阻，且类似地，可将第二电阻称为第一电阻。第一电阻和第二电阻两者都是电阻，但其不是同一电阻。
可以理解，以下实施例中的“连接”，如果被连接的电路、模块、单元等相互之间具有电信号或数据的传递，则应理解为“电连接”、“通信连接”等。
在此使用时，单数形式的“一”、“一个”和“所述/该”也可以包括复数形式，除非上下文清楚指出另外的方式。还应当理解的是，术语“包括/包含”或“具有”等指定所陈述的特征、整体、步骤、操作、组件、部分或它们的组合的存在，但是不排除存在或添加一个或更多个其他特征、整体、步骤、操作、组件、部分或它们的组合的可能性。
传统机械式或全固态等类型的直流断路器断开直流电流的基本原理相似，均由稳态通流支路、电流转移支路、能量吸收支路等并联且互相配合进行断流。例如，如图2所示的无源自激振荡型高压直流断路器，在系统正常运行时，直流电流经交流断路器B流通(稳态通流支路)。当系统发生故障时，交流断路器B分闸，分闸后会产生不稳定的电弧电压，引发电感L、电容C和电阻R支路产生振荡(电流转移支路)，通过选择合适的电感L和电容C的参数，使它们与电弧的负阻特性相匹配，电流转移支路振荡电流幅值会迅速增加，当振荡电流幅值同流过分闸处电流幅值相等、方向相反时，叠加到分闸处的电流即为零， 实现电弧熄灭。随后，短路电流转移到电流转移支路上，对电容C进行充电，当其正向电压达到避雷器MOA动作值时，避雷器MOA动作，故障电流被转移至避雷器MOA中(能量吸收支路)，待能量吸收完毕后电流变为零，高压直流断路器分断过程结束。
由此可见，现有的高压直流断路器均需包含多条支路结构，原理上都需要电流转移支路创造电流过零点来消灭电弧，并且在直流容量较大时，还需要大量的避雷器设备来进行能量吸收，导致设备结构复杂。
在一个实施例中，本申请提出一种直流断路器10，如图1所示，包括：变压器110、第一开关120、第二开关130与信号采集模块140，变压器110的二次绕组与第一开关120均设置于输电线路，变压器110的一次绕组通过第二开关120连接交流电网，信号采集模块140连接并采集一次绕组的第一电压、交流电网的第二电压与二次绕组的电流；在输电线路为正常运行状态时，第一开关120闭合，第二开关130断开；在输电线路为故障状态且第二电压与第一电压的差值满足关断阈值时，第二开关130闭合，以及在电流降低并达到电流阈值时，第一开关120与第二开关130均断开。
具体地，变压器110为利用电磁感应的原理来改变交流电压的装置，包括两组绕有导线的线圈，并且彼此以电感的方式互相影响。当交流电流流于其中的一组线圈时，在另一组线圈中将感应出具有相同频率的交流电压，而感应的电压大小取决于两线圈磁感应的强度。根据电磁感应原理，当流过线圈的交流电流越大时，另一侧感应出磁感应强度越大，感应出的交流电压也就越大。在一个实施例中，如图1所示，变压器110可为单相变压器，包括铁芯、一次绕组与二次绕组，一次绕组与二次绕组均缠绕在铁芯上，一次绕组的输入端连接交流电网，一次绕组的输出端通过第二开关130连接交流电网，二次绕组与第 一开关120串联后接入输电线路。
进一步地，信号采集模块140连接变压器110的一次绕组并采集其第一电压，作为判断输电线路是否发生故障的依据。具体的，在输电线路正常运行状态下，其上流过的为直流电流，变压器110的二次绕组中流过的也是直流电压，在一次绕组并不会产生感应电压，因此在输电线路正常运行状态下，信号采集模块140采集的一次绕组的第一电压为零；而当输电线路发生接地故障时，二次绕组侧流过的故障电流与正常电流的方向相反，由于楞次定律，会在二次绕组中产生自感电动势，然后该自感电动势也会对一次绕组感应出电压，当信号采集模块140采集的一次绕组的第一电压大于故障阈值时，可判断输电线路发生了接地故障，需要进行故障电流抑制与隔离的操作。其中，故障阈值为大于零的电压，可根据实际情况设定。
进一步地，信号采集模块140采集的交流电网的第二电压，作为判断何时进行故障电流抑制的依据。在第二电压与第一电压的差值满足关断阈值时，第二开关130闭合将变压器110的一次绕组接入交流电网，对变压器110的二次绕组感应产生一个反向的抑制电动势，以抵消二次绕组中流过的故障电流。具体地，关断阈值可根据实际情况设定，可以是一个接近零的数值，也可以设置为零，不以此为限定，只要能保证第二开关130的两端闭合时压差较小，不会损坏第二开关130。
进一步地，当变压器110的二次绕组感应产生反向的抑制电动势后，会逐步抵消二次绕组中流过的故障电流，将二次绕组的电流逐步拉低。因此信号采集模块140连接变压器110的二次绕组并采集的电流，可以作为判断是否需要断开第一开关120与第二开关130来切断输电线路与交流电网以隔离故障点的依据。
其中，第一开关120设置于输电线路，用于连接与分断输电线路，第一开关120还根据信号采集模块140采集的二次绕组的电流来判断是否需要断开连接。在输电线路处于正常运行状态时，第一开关120一直处于闭合状态，直流电流经过输电线路进行传输。而当输电线路发生接地故障且降低至电流阈值时，第一开关120断开，分断输电线路上的故障点。与此同时，由于无需继续对故障电流进行抵消抑制，将第二开关130也断开，变压器110的一次绕组与交流电网断开连接，故障输电线路完全被隔离。在一个实施例中，电流阈值为允许断开输电线路以消除故障的安全电流，可根据第一开关120的参数进行确定，在电流阈值时断开第一开关120，能保证不损坏第一开关120且冲击最小，可设置为零，也可设置为一个接近于零的小电流值。
此外，第一开关120与第二开关130的闭合与断开采取的方式并不唯一，可根据本申请直流断路器的应用场景来确定。例如，在一个实施例中，第一开关120与第二开关130可以是手动分合的开关元件，信号采集模块140通过数模转化电路连接控制中心的显示设备与报警设备，当发生变压器110的一次绕组的电压或二次绕组的电流达到电流阈值时，控制中心技术人员发现并对第一开关120与第二开关130进行相应操作，完成输电线路故障故障隔离操作。在另一个实施例中，如果应用场景中包含可进行自动控制的控制模块时，第一开关120与第二开关130还可以是自动控制型开关元件，第一开关120、第二开关130与信号采集模块140均连接至系统中的控制模块，控制模块根据反馈的数据自动控制开关元件进行相应动作，完成输电线路故障隔离。
上述直流断路器，通过变压器的电磁感应原理，以及在适当的时候控制两个开关元件的开闭状态切换将故障电流的能量转移至交流电网，且能在故障初期产生自感电动势自动抑制故障电流，原理简单可靠，避免了采用多支路的并 联结构以及避雷器等设备，降低了设备复杂度以及维护难度。
在一个实施例中，如图1所示，信号采集模块140包括电压采集模块与电流采集模块，电压采集模块连接第二开关130的两端，电流采集模块连接二次绕组。
具体地，电压采集模块连接第二开关130的两端，采集一次绕组的第一电压与交流电网的第二电压，作为判断输电线路是否发生故障以及何时进行故障电流抑制的依据。电流采集模块连接变压器110的二次绕组并采集其电流，作为判断是否需要断开第一开关120与第二开关130来切断输电线路与交流电网以隔离故障点的依据。
其中，电压采集模块与电流采集模块可为带有通讯功能的模拟量采集模块器，可通过模拟量采集模块器上的三路通道分别连接第二开关130的两端与二次绕组采集电压与电流，然后通过模拟量采集模块器上的通讯接口将采集的数据传输出去进行相关操作。此外，电压采集模块与电流采集模块也可为电压或电流传感器与数模转换电路结合组成，通过电压或电流传感器采集电压或电流后经过数模转换电路将采集的数据传输出去进行相关操作，本实施例不以此为限定。
在本实施例中，通过信号采集模块140分别采集变压器110的电压与电流值作为判断依据，为直流断路器达到分断输电线路上的故障提供数据基础。
在采用自动控制的方式对第一开关120与第二开关130的开闭状态进行调整时，第一开关120与第二开关130为带控制端的控制开关，控制端连接至系统中的控制模块。
在一个实施例中，如图1所示，第一开关120为第一交流接触器，第一交流接触器的线圈连接控制模块，第一交流接触器的触头设置于输电线路。
其中，交流接触器为利用电磁力与弹簧弹力相配合，实现触头的导通与断开的装置，当其线圈通电后，使静铁芯产生电磁吸力，衔铁被吸合，与衔铁相连的连杆带动触头动作，使常闭触头断开，接触器处于得电状态；当其线圈断电时，电磁吸力消失，衔铁在复开，使常开触头闭合，位弹簧作用下释放，所有触头随之复位，接触器处于失电状态。
具体地，第一交流接触器的线圈作为控制端连接系统中的控制模块，在信号采集模块140反馈的电流降低至电流阈值时，控制模块给第一交流接触器的线圈断电，使第一交流接触器串接于输电线路的触头断开，分断输电线路上的故障点。
在一个实施例中，如图1所示，第二开关130为第二交流接触器，第二交流接触器的线圈连接控制模块，第二交流接触器的触头的一端连接变压器的一次绕组，第二交流接触器的触头的另一端连接交流电网。
具体地，第二交流接触器的线圈作为控制端连接系统中的控制模块，在信号采集模块140反馈的第二电压与第一电压的差值满足关断阈值时，控制模块给第二交流接触器的线圈通电，使变压器的一次绕组通过第二交流接触器的触头连接至交流电网的回路导通，进行故障电流抑制。然后在信号采集模块140反馈的电流降低至电流阈值时，控制模块给第二交流接触器的线圈断电，使变压器的一次绕组通过第二交流接触器的触头连接至交流电网的回路断开，分断输电线路上的故障点。
在本实施例中，通过将本申请直流断路器中的开关元件与控制模块连接，可达到快速自动分断输电线路上的故障点的目的。
以下以直流断路器应用于多端直流输电系统为例进行解释说明，在多端直流输电系统中，换流站通过输电线路将直流电流输送至直流电网。如图3-图6 所示，直流断路器包括变压器、交流断路器A与交流断路器B，变压器的二次绕组与交流断路器A设置于输电线路，变压器的一次绕组通过交流断路器B连接交流电网，交流断路器B连接交流电网的端子为K1端，交流断路器B连接变压器的一次绕组的端子为K2端，第一电压为K2端的电压，第二电压为K1端的电压，其工作过程可包括以下四个阶段：
阶段一：正常流通阶段。
具体地，如图3所示，当输电线路处于正常运行状态时，交流断路器A闭合，交流断路器B断开，此时正常的直流电流通过变压器二次绕组与交流断路器A正常流通过直流断路器，变压器二次绕组无感应电动势，K2端电压为零。
阶段二：自感抑流阶段。
具体地，如图4所示，当输电线路发生接地故障时，接地故障点两端的来自换流站的故障电流1与来自直流电网的故障电流2快速增大，均流向接地故障点。此时，故障电流2与正常的直流电流方向相反，根据楞次定律，会在变压器二次绕组中产生自感电动势E1，自感电动势E1的方向与故障电流2方向相反，即在故障初期就能自动起到抑制故障电流2的作用，同时，由于电磁感应原理，会在变压器的一次绕组中感应产生一定的电压，使得K2端电压升高。
阶段三：强迫抑流阶段。
具体地，当K2端的电压大于故障阈值时，判断出输电线路发生接地故障，且在K1端的交流电压接近K2端的电压时，闭合交流断路器B，对变压器的二次绕组引入交流电网，由此通过电磁感应在变压器二次绕组中产生一个与故障电流2方向相反的强制电动势E2，主动抑制并逐步将流过变压器二次绕组中的电流降低，同时强制电动势E2产生的电压与正常直流电流方向相同，也有利于输电线路在故障期间继续运行，抵消接地故障点拉低电压的影响，在此过程中 故障电流2的能量通过变压器逐步向交流电网释放。
阶段四：故障断开阶段。
具体地，当变压器二次绕组中的电流持续降低并达到电流阈值时，故障电流2的能量基本释放完成，断开交流断路器A和交流断路器B将接地故障点隔离。
在本实施例中，通过变压器的电磁感应原理，以及在适当的时候控制两个交流接触器的开闭状态切换将故障电流的能量转移至交流电网，且能在故障初期就自动抑制故障电流，原理简单可靠，避免了采用多支路的并联结构以及避雷器等设备，降低了直流断路器的复杂度以及维护难度。
在一个实施例中，如图7所示，提供一种多端直流输电系统，包括上述任意一项中的直流断路器10。
具体地，对于多端直流输电系统，在发生接地故障时，需要短时停运整个多端直流系统以清除故障，然后重启直流系统，这会导致与其相连的交流系统受到较大冲击，对弱交流系统的影响更为显著，甚至会带来系统失稳的风险。因此，在多端直流系统中设置直流断路器10以切断故障电流并使故障部分退出运行，能大幅缩短故障后的恢复时间，且不需停运整个多端直流系统。
在一个实施例中，如图7所示，上述多端直流输电系统还包括控制模块20和输电线路，控制模块20连接直流断路器10，直流断路器10设置于输电线路。
具体地，控制模块20连接直流断路器10的交流断路器A的控制端与直流断路器10的交流断路器B的控制端，直流断路器10的变压器的二次绕组与交流断路器A的触头设置于输电线路。在输电线路发生接地故障时，控制模块20根据直流断路器10的信号采集模块反馈的第一电压、第二电压与电流控制交流断路器A与交流断路器B的开闭状态，达到分断输电线路上接地故障点与直流 电网的连接的目的。
在本实施例中，通过直流断路器10切断故障电流并使故障部分无法继续给直流电网输电，能大幅缩短故障后的恢复时间。
在一个实施例中，如图7所示，上述多端直流输电系统还包括换流站30，换流站30的输入端连接交流电网，换流站30的输出端通过输电线路连接直流电网。
具体地，换流站30为完成交流电变换为直流电或者将直流电变换为交流电的转换的站点。在本实施例中，换流站30将交流电网中的交流电转换为直流电后通过输电线路输送至直流电网。此外，在输电线路上发生接地故障时，来自换流站端的故障电流1由换流站30的控制保护系统及时响应进行消除，不属于直流断路器10的工作区域。
在一个实施例中，输电线路为三条以上，直流断路器10的数量和换流站30的数量与输电线路的数量一致，各条输电线路的输入端对应连接一个换流站30，各条输电线路的输出端均连接直流电网，各条输电线路的输出端还对应设置一个直流断路器10，各直流断路器10还均连接控制模块20。
具体地，多端直流输电系统由三个或三个以上的换流站30及连接换流站30之间的输电线路组成。在每条输电线路连接至直流电网的末端，均设置有一个直流断路器10，可实现多个交流电源稳定安全的向多个负荷中心进行供电。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的 普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种直流断路器，其特征在于，包括：变压器、第一开关、第二开关与信号采集模块，所述变压器的二次绕组与所述第一开关均设置于输电线路，所述变压器的一次绕组通过所述第二开关连接交流电网，所述信号采集模块连接并采集所述一次绕组的第一电压、所述交流电网的第二电压与所述二次绕组的电流；
    在所述输电线路为正常运行状态时，所述第一开关闭合，所述第二开关断开；在所述输电线路为故障状态且所述第二电压与所述第一电压的差值满足关断阈值时，所述第二开关闭合，以及在所述电流降低并达到电流阈值时，所述第一开关与所述第二开关均断开。
  2. 根据权利要求1所述的直流断路器，其特征在于，所述信号采集模块包括电压采集模块与电流采集模块，所述电压采集模块分别连接所述第二开关的两端，所述电流采集模块连接所述二次绕组。
  3. 根据权利要求1所述的直流断路器，其特征在于，所述电流阈值为允许断开所述输电线路以消除故障的安全电流。
  4. 根据权利要求1所述的直流断路器，其特征在于，所述变压器包括铁芯、一次绕组与二次绕组，所述一次绕组与所述二次绕组均缠绕在所述铁芯上，所述一次绕组的输入端连接所述交流电网，所述一次绕组的输出端通过所述第二开关连接所述交流电网，所述二次绕组与所述第一开关串联后接入所述输电线路。
  5. 根据权利要求1所述的直流断路器，其特征在于，所述第一开关为第一交流接触器，所述第一交流接触器的线圈连接控制模块，所述第一交流接触器的触头设置于所述输电线路。
  6. 根据权利要求5所述的直流断路器，其特征在于，所述第二开关为第二 交流接触器，所述第二交流接触器的线圈连接所述控制模块，所述第二交流接触器的触头的一端连接所述变压器的一次绕组，所述第二交流接触器的触头的另一端连接所述交流电网。
  7. 一种多端直流输电系统，其特征在于，包括权利要求1-6中任意一项所述的直流断路器。
  8. 根据权利要求7所述的多端直流输电系统，其特征在于，还包括控制模块和输电线路，所述控制模块连接所述直流断路器，所述直流断路器设置于所述输电线路。
  9. 根据权利要求8所述的多端直流输电系统，其特征在于，还包括换流站，所述换流站的输入端连接交流电网，所述换流站的输出端通过所述输电线路连接直流电网。
  10. 根据权利要求9所述的多端直流输电系统，其特征在于，所述输电线路为三条以上，所述直流断路器的数量和所述换流站的数量与所述输电线路的数量一致，各所述换流站的输入端均连接所述交流电网，各条输电线路的输入端对应连接一个所述换流站的输出端，各条输电线路的输出端均连接直流电网，各条输电线路的输出端还对应设置一个所述直流断路器，各所述直流断路器还均连接所述控制模块。
PCT/CN2021/105376 2021-05-28 2021-07-09 多端直流输电系统的直流断路器 WO2022246976A1 (zh)

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