WO2021129823A1 - 特高压直流高端换流器阀区接地故障控制方法及控制装置 - Google Patents

特高压直流高端换流器阀区接地故障控制方法及控制装置 Download PDF

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Publication number
WO2021129823A1
WO2021129823A1 PCT/CN2020/139541 CN2020139541W WO2021129823A1 WO 2021129823 A1 WO2021129823 A1 WO 2021129823A1 CN 2020139541 W CN2020139541 W CN 2020139541W WO 2021129823 A1 WO2021129823 A1 WO 2021129823A1
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Prior art keywords
converter
end converter
current
pole
control
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PCT/CN2020/139541
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English (en)
French (fr)
Inventor
卢东斌
陈乐�
王俊生
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南京南瑞继保电气有限公司
南京南瑞继保工程技术有限公司
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Priority to BR112022010457A priority Critical patent/BR112022010457A2/pt
Publication of WO2021129823A1 publication Critical patent/WO2021129823A1/zh

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    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • 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
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/26—Arrangements for eliminating or reducing asymmetry in polyphase 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase 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

  • This application relates to the technical field of high-voltage direct current transmission, in particular to a method for controlling a ground fault in the valve zone of an ultra-high voltage direct current high-end converter and its control device.
  • UHV DC transmission systems generally use two converters in series to form a DC pole. According to existing projects, they are divided into conventional UHV DC transmission systems, hierarchical access UHV DC transmission systems and hybrid UHV DC transmission systems.
  • the conventional UHV DC transmission system is a DC pole high-end and low-end converters, both of which are grid-commutated converters, and they are connected to the same AC grid.
  • Hierarchical access to the UHV DC transmission system is that the high-end and low-end converters of a DC pole are all grid-commutated converters, and they are respectively connected to two different AC power grids.
  • Hybrid UHV DC transmission systems are divided into several types: inter-station hybrid, inter-polar hybrid and intra-polar hybrid.
  • the inter-station hybrid hybrid UHV DC transmission system uses voltage source converters.
  • the converter station of a DC pole is high and low.
  • Both the end converters are voltage source converters
  • the hybrid UHV DC transmission system using voltage source converters for hybrid UHV DC transmission systems uses voltage source converters.
  • Both the high and low end converters of the DC pole are voltage source converters, and the poles are mixed.
  • the hybrid UHV DC transmission system adopts the grid-commutated converter and the high-end converter of the DC pole of the voltage source converter.
  • the high-end and low-end converters are respectively the grid-commutated converter and the voltage source converter.
  • the prior art isolates the fault by blocking the entire DC pole. After the fault is isolated, the single pole is used to continue the operation. Either switch to metal loop operation, or restart the non-faulty converter of the DC pole to achieve balanced operation of dual DC poles.
  • the existing technology mainly has the following problems: after the entire DC pole is blocked, a large current will flow through the ground electrode line, which will easily cause the transformer in the nearby substation to have DC bias and cause the transformer to saturate; after the entire DC pole is blocked, if the power is transmitted Larger, more DC power will be lost; after blocking the entire DC pole, more fault current will flow through the fault point.
  • the embodiment of the present application provides a method for controlling a ground fault in the valve area of a UHV DC high-end converter, which is applied to the high-end converter of the DC pole of an UHV DC transmission system, and the UHV DC transmission system includes at least one rectifier station and At least one inverter station, the rectifier station and the inverter station include single DC poles or double DC poles, the DC poles include at least two converters connected in series, and the high-end converters are near the pole bus In the converter, when the DC pole where the high-end converter is located in full valve group operation, and it is detected that a ground fault occurs in the valve area of the high-end converter, the control method includes: controlling the high-end converter Blocking; controlling the minimum current flowing through the fault point; isolating the high-end converter; controlling the UHV DC transmission system to resume normal operation.
  • the high-end converter or the low-end converter includes at least one of a grid phase converter or a voltage source converter.
  • the dual DC pole operation includes: each of the DC poles has at least one converter in operation; the full valve group operation includes: the DC pole where the high-end converter is located in addition to the high-end converter At least one converter is in operation besides the converter.
  • the occurrence of a ground fault in the valve area of the high-end converter includes: a ground fault occurs in the high-end converter, a ground fault occurs in the connection line between the high-end converter and the converter transformer, and the At least one of the ground faults in the valve-side winding of the converter transformer.
  • the detecting that a ground fault occurs in the valve area of the high-end converter includes:
  • controlling the high-end converter to lockout includes: controlling the high-end converter to stop sending trigger pulses, and close the high-end where the high-end converter is located.
  • the second bypass switch of the valve group trips the converter transformer inlet switch of the high-end converter, and the second bypass switch is connected to the positive pole and the negative pole of the high-end converter.
  • the controlling the high-end converter to lockout includes: when the high-end converter is in rectification operation, selecting the first rectifier-side converter One blocking mode or the second blocking mode of the rectifier-side converter; when the high-end converter is in inverter operation, select the first blocking mode of the inverter-side converter and the second blocking mode of the inverter-side converter Locking method.
  • the first blocking method of the rectifier-side converter includes: controlling the high-end converter in rectification operation to stop triggering pulses, and the corresponding inverter operation in the inverter controls the trigger angle to be 90 degrees; Control to jump off the converter transformer inlet switch of the high-end converter, close the second bypass switch of the high-end valve group where the high-end converter is located, and put the corresponding inverter running in the bypass pair into the bypass pair and close A bypass switch, the second bypass switch is connected to the anode and the cathode of the high-side converter.
  • the second locking method of the rectifier-side converter includes: controlling the high-end converter to put into a bypass pair, closing the second bypass switch of the high-end valve group where the high-end converter is located, and at the same time The inverter transformer inlet switch of the high-end converter is tripped, and the corresponding inverter control trigger angle of inverter operation is 90 degrees, and the second bypass switch is connected to the anode and cathode of the high-end converter ; Control the corresponding inverter running the inverter into the bypass pair and close the bypass switch.
  • the first locking method of the inverter-side converter includes: controlling to trip the converter transformer inlet switch of the high-end converter in inverter operation, turning on the bypass pair, and closing the high-end converter.
  • the second bypass switch of the high-end valve group where the converter is located, the corresponding rectifying operation of the converter has a control trigger angle of 90 degrees, and the second bypass switch is connected to the anode and cathode of the high-end converter; The corresponding converter in rectifying operation is put into the bypass pair, and the bypass switch is closed.
  • the second blocking method of the inverter-side converter includes: controlling the inverter operation of the high-end converter into a bypass pair, and closing the second of the high-end valve group where the high-end converter is located.
  • Bypass switch and at the same time trip the converter transformer inlet switch connected to the high-end converter, the corresponding rectifying operation converter controls the trigger angle to be 90 degrees, and the second bypass switch is connected to the low-end converter
  • the anode and cathode of the inverter; the inverter that controls the corresponding rectification operation is put into the bypass pair, and the bypass switch is closed.
  • controlling the current flowing through the fault point to be the smallest includes: controlling the voltage of the busbar of the DC pole where the high-side converter is located to zero or controlling the low-end commutation of the DC pole where the high-side converter is located
  • the DC current of the high-end converter is equal to the DC current of the corresponding pole of the station other than the station where the high-end converter is located, or the converter that controls the operation of the rectifier side of the DC pole where the high-end converter is located is phase shifted,
  • the low-end converter is the converter close to the extremely neutral bus.
  • the controlling the pole bus voltage of the DC pole where the high-end converter is located to zero includes: the low-end converter uses current control to control the DC current, and the inverter
  • the corresponding converter on the rectifier side adopts voltage control to control the pole bus voltage of the rectifier side to zero; or the low-end converter adopts voltage control to control the pole bus voltage of the rectifier side to zero, and sends fault information to the inverter.
  • the corresponding inverter on the inverter side uses current control to control the DC current.
  • the controlling the pole bus voltage of the DC pole where the high-side converter is located to zero includes: the low-side converter adopts voltage control to control the inverter side The pole bus voltage is zero, and the fault information is sent to the rectifier side.
  • the corresponding converter on the rectifier side uses current control to control the DC current; or the low-end converter uses current control to control the DC current, and the corresponding converter on the rectifier side uses current control to control the DC current.
  • the inverter uses voltage control to control the pole bus voltage on the inverter side to zero.
  • the DC current of the low-end converter controlling the DC pole where the high-end converter is located is equal to the DC current of the corresponding poles of other stations except the station where the high-end converter is located, including:
  • the low-end converter uses current control to control the DC current, the corresponding poles of the other stations use current control to control the DC current, and the low-end converter uses the same DC current reference value as the corresponding poles of the other stations;
  • the DC current of the low-end converter is at least one of the high-voltage bus current and the low-voltage bus current on the DC side of the low-end converter.
  • the DC current of the corresponding pole of the other station Is at least one of the pole bus current of the corresponding pole of the other station, the high voltage bus current of the DC side of the converter, and the low voltage bus current. If there are two or more of the other stations, the DC current of the corresponding pole of the other station It is at least one of the sum of the pole bus currents of the corresponding poles of the other stations, the sum of the high voltage bus currents on the DC side of the converter, and the sum of the low voltage bus currents.
  • the DC current reference value of the current-controlled converter is determined according to the active power, reactive power, or ground current limit requirements of the UHV DC transmission system.
  • the isolating the high-end converter includes: closing the first bypass switch of the high-end valve group where the high-end converter is located, and separating the second bypass switch and valve group switch of the high-end valve group. And a bus switch, the first bypass switch is connected in parallel with the high-end converter, the second bypass switch is connected to both ends of the high-end converter, and the valve block switch is connected to the high-end converter.
  • the busbar switch connects the high-end converter and the pole busbar.
  • the separation of the second bypass switch, valve group switch and bus switch of the high-end valve group where the high-end converter is located includes: If the high-voltage bus current on the DC side of the high-end converter is greater than the low-voltage bus current, the bus switch is separated first, then the second bypass switch is separated, and then the valve group switch is separated; if the high-end converter has a direct current The high-voltage bus current on the side is smaller than the low-voltage bus current, the valve group switch is first separated, then the second bypass switch is separated, and then the bus switch is separated.
  • the separation of the second bypass switch, valve group switch, and bus switch of the high-end valve group where the high-end converter is located includes: If the high-voltage bus current on the DC side of the high-end converter is greater than the low-voltage bus current, first separate the bus switch, then separate the valve group switch, and then separate the second bypass switch; if the high-end converter is on the DC side If the high-voltage bus current is less than the low-voltage bus current, the second bypass switch is first separated, then the valve group switch is separated, and then the bus switch is separated.
  • the separation of the second bypass switch, the valve group switch and the busbar switch of the high-end valve group where the high-end converter is located includes: If the high-voltage bus current on the DC side of the converter is greater than the low-voltage bus current, first separate the second bypass switch, then separate the bus switch, and then separate the valve block switch; if the high-voltage on the DC side of the high-end converter If the bus current is less than the low voltage bus current, the valve group switch is first separated, then the bus switch is separated, and then the second bypass switch is separated.
  • the controlling the UHV DC power transmission system to resume normal operation includes: controlling the low-end converter to resume operation, or controlling the converter on the rectifier side to resume normal operation after phase shifting.
  • the controlling the low-end converter to resume normal operation includes: among the converters of the corresponding poles of the low-end converter and the other station, one converter adopts voltage control or maximum Trigger angle control, other converters adopt current control, and control the low-end converter to operate according to normal DC voltage and normal DC current; said controlling the converter on the rectifier side to resume normal operation after the phase shift is removed, including : After the converter on the rectifier side is phase-shifted, among the converters of the low-end converter and the corresponding poles of the other stations, one converter adopts voltage control or maximum firing angle control, and the other converters The converter adopts current control to control the low-end converter to operate according to normal DC voltage and normal DC current.
  • the method before the isolation of the high-end converter, the method further includes: increasing the range of the differential protection differential current value of the DC pole where the high-end converter is located or increasing the DC where the high-end converter is located.
  • the extreme difference protection delays the fixed value or shields the extreme difference protection until the high-end converter is isolated.
  • the control of the current flowing through the fault point after the control of the current flowing through the fault point is minimized, it further includes: controlling the converter on the rectifier side to restart once after a certain de-ionization time; if the restart is successful, the converter on the rectifier side The converter resumes normal operation; if the restart fails, the converter on the rectifier side continues to control the minimum current flowing through the fault point.
  • the embodiment of the present application also provides an UHV DC high-end converter valve area ground fault control device, which applies the above-mentioned UHV DC high-end converter valve area ground fault control method.
  • the control device includes a detection unit and a control unit.
  • the detection unit is used to detect the high-voltage bus current and the low-voltage bus current of the high-end converter, the extremely neutral bus current of the dual DC poles, and the high-voltage bus current and the low-voltage bus current of the low-end converter And the pole bus current, the pole bus voltage and the pole neutral bus voltage are detected;
  • the control unit is used to determine the full valve group operation of the DC pole where the high-end converter of the UHV DC transmission system is located, and detects that the When a ground fault occurs in the valve area of the high-end converter, the high-end converter is controlled to lock; the current flowing through the fault point is minimized; the high-end converter is isolated; and the UHV DC transmission system is controlled to resume normal operation.
  • the entire DC pole is not blocked, but only the faulty converter is blocked.
  • the current of the normal operating pole is introduced to the pole bus of the fault pole, so as to prevent the current of the normal operating pole from flowing into the fault point or passing too much Shift the phase of the converter on the rectifier side to block the current from flowing to the fault point, so as to ensure more converters to operate and avoid the loss of large DC transmission power.
  • Fig. 1 is a schematic diagram of a main circuit of an UHV DC transmission system provided by an embodiment of the present application
  • FIG. 2 is a schematic flow chart of a method for controlling a ground fault in the valve zone of an UHV DC high-end converter provided by an embodiment of the present application;
  • FIG. 3 is a schematic flowchart of another method for controlling a ground fault in the valve zone of a UHV DC high-end converter provided by an embodiment of the present application;
  • Fig. 4 is a schematic structural diagram of a ground fault control device for a valve zone of an UHVDC high-end converter provided by an embodiment of the present application.
  • Fig. 1 is a schematic diagram of a main circuit of an UHV DC transmission system provided by an embodiment of the present application.
  • the main circuit of UHV DC transmission system includes rectifier station 100, inverter station 200, first DC line 150, second DC line 160, rectifier station ground electrode line 114, rectifier station ground electrode 115 and inverter station ground electrode line 214 , Inverter station grounding pole 215.
  • the rectifier station 100 includes a first first DC pole I110, a second second DC pole II120, a first AC filter bank 118, a first AC system 140, a converter transformer inlet switch and a metal loop transfer switch 113.
  • the first DC pole I110 includes a first high-end valve group 111, a first low-end valve group 112, a first high-end converter transformer 116, a first low-end converter transformer 117, a first DC filter 93, and a first flat. Wave reactor 91.
  • the first high-end valve group 111 and the first low-end valve group 112 are connected in series.
  • the first high-end valve group 111 includes a first high-end converter 1, a first high-end valve group, a first bypass switch 11, a first high-end valve group and a second bypass switch 12, a first high-end valve group bus switch 13, a first High-end valve group valve group switch 14.
  • the first bypass switch 11 of the first high-end valve group is connected in parallel with the first high-end converter 1, the first high-end valve group and the second bypass switch 12 are connected to both ends of the first high-end converter 1, and the first high-end valve group
  • the valve group switch 14 connects the first high-end converter 1 and the valve group connection line, and the first high-end valve group bus switch 13 connects the first high-end converter 1 and the pole bus.
  • the first low-end valve group 112 includes a first low-end converter 2, a first low-end valve group, a first bypass switch 21, a first low-end valve group and a second bypass switch 22, and a first low-end valve group valve Group switch 23, first low-end valve group bus switch 24.
  • the first low-end valve group first bypass switch 21 is connected in parallel with the first low-end converter 2
  • the first low-end valve group second bypass switch 22 is connected to both ends of the second low-end converter 2.
  • a low-end valve group valve group switch 23 connects the first low-end converter 2 and the valve group connection line
  • the first low-end valve group bus switch 24 connects the first low-end converter 2 and the extremely neutral bus.
  • the first high-end converter 1 and the first low-end converter 2 include at least one of a grid commutated converter or a voltage source converter.
  • the power grid commutation converter includes but is not limited to at least one of a six-pulse bridge circuit and a twelve-pulse bridge circuit.
  • the six-pulse bridge circuit and the twelve-pulse bridge circuit include, but are not limited to, non-switchable semi-controlled power semiconductor devices, generally thyristor devices.
  • Voltage source converters include, but are not limited to, two-level converters, diode-clamped multi-level converters, modular multi-level converters MMC, hybrid multi-level converters HMC, two-level converters At least one of the combined converter CSL and the stacked two-level converter CTL.
  • Voltage source converters include, but are not limited to, fully controlled power semiconductor devices that can be turned off.
  • the above-mentioned modular multilevel converter MMC includes, but is not limited to, a modular multilevel converter MMC with a half-bridge sub-module structure, a modular multi-level converter MMC with a full-bridge sub-module structure, a half-bridge and a full-bridge sub-module structure. At least one type of modular multilevel converter MMC with a bridge hybrid sub-module structure.
  • the second DC pole II120 includes a second high-end valve group 121, a second low-end valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second DC filter 94, and a second smoothing reactor ⁇ 92.
  • the second high-end valve group 121 and the second low-end valve group 122 are connected in series.
  • the second high-end valve group 121 includes a second high-end inverter 4, a second high-end valve group first bypass switch 41, a second high-end valve group second bypass switch 42, a second high-end valve group valve group switch 43, Two high-end valve group bus switch 44.
  • the first bypass switch 41 of the second high-end valve group is connected in parallel with the second high-end converter 4, and the second bypass switch 42 of the second high-end valve group is connected to both ends of the second high-end converter 4.
  • the second high-end valve group The valve group switch 43 connects the second high-end converter 4 and the valve group connection line, and the second high-end valve group bus switch 44 connects the second high-end converter 4 and the pole bus.
  • the second low-end valve group 122 includes a second low-end converter 3, a second low-end valve group first bypass switch 31, a second low-end valve group second bypass switch 32, and a second low-end valve group bus Switch 33, the second low-end valve group valve group switch 34.
  • the first bypass switch 31 of the second low-end valve group is connected in parallel with the second low-end converter 3
  • the second bypass switch 32 of the second low-end valve group is connected to both ends of the second low-end converter 3.
  • the second low-end valve group valve group switch 34 connects the second low-end converter 3 and the valve group connection line
  • the second low-end valve group bus switch 33 connects the second low-end converter 3 and the extremely neutral bus.
  • the second high-end converter 4 and the second low-end converter 3 include at least one of a grid commutated converter or a voltage source converter.
  • the inverter station 200 includes a third DC pole I210, a fourth DC pole II220, a second AC filter bank 218, a second AC system 240, and a converter transformer inlet switch.
  • the third DC pole I210 includes a third high-end valve group 211, a third low-end valve group 212, a third high-end converter transformer 216, a third low-end converter transformer 217, a third DC filter 97, and a third smoothing reactor. ⁇ 95.
  • the third high-end valve group 211 and the third low-end valve group 212 are connected in series.
  • the third high-end valve group 211 includes the third high-end converter 5, the third high-end valve group first bypass switch 51, the third high-end valve group second bypass switch 52, the third high-end valve group bus switch 53, and the third High-end valve group valve group switch 54.
  • the first bypass switch 51 of the third high-end valve group is connected in parallel with the third high-end converter 5, and the second bypass switch 52 of the third high-end valve group is connected to both ends of the third high-end converter 5.
  • the third high-end valve group The valve group switch 54 connects the third high-end converter 5 and the valve group connection line, and the third high-end valve group bus switch 53 connects the third high-end converter 5 and the pole bus.
  • the third low-end valve group 212 includes a third low-end converter 6, a third low-end valve group first bypass switch 61, a third low-end valve group second bypass switch 62, and a third low-end valve group valve Group switch 63, the third low-end valve group bus switch 64.
  • the first bypass switch 61 of the third low-end valve group is connected in parallel with the third low-end converter 6, and the second bypass switch 62 of the third low-end valve group is connected to both ends of the third low-end converter 6.
  • the three-low-end valve group valve group switch 63 connects the third low-end converter 6 and the valve group connection line, and the third low-end valve group bus switch 64 connects the third low-end converter 6 and the extremely neutral bus.
  • the third high-end converter 5 and the third low-end converter 6 include at least one of a grid commutated converter or a voltage source converter.
  • the fourth DC pole II220 includes a fourth high-end valve group 221, a fourth low-end valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth DC filter 98, and a fourth smoothing reactor ⁇ 96.
  • the fourth high-end valve group 221 and the fourth low-end valve group 222 are connected in series.
  • the fourth high-end valve group 222 includes a fourth high-end converter 8, a fourth high-end valve group first bypass switch 81, a fourth high-end valve group second bypass switch 82, a fourth high-end valve group valve group switch 83, and a fourth high-end valve group second bypass switch 82.
  • the first bypass switch 81 of the fourth high-end valve group is connected in parallel with the fourth high-end converter 8, and the second bypass switch 82 of the fourth high-end valve group is connected to both ends of the fourth high-end converter 8.
  • the valve group switch 83 connects the fourth high-end converter 8 and the valve group connection line
  • the fourth high-end valve group bus switch 84 connects the fourth high-end converter 8 and the pole bus.
  • the fourth low-end valve group 221 includes a fourth low-end converter 7, a fourth low-end valve group first bypass switch 71, a fourth low-end valve group second bypass switch 72, and a fourth low-end valve group bus Switch 73, the fourth low-end valve group valve group switch 74.
  • the first bypass switch 71 of the fourth low-end valve group is connected in parallel with the fourth low-end converter 7, and the second bypass switch 72 of the fourth low-end valve group is connected to both ends of the fourth low-end converter 7.
  • the four-low-end valve group valve group switch 74 connects the fourth high-end converter 7 and the valve group connection line, and the fourth low-end valve group bus switch 73 connects the fourth low-end converter 7 and the extremely neutral bus.
  • the fourth high-end converter 8 and the fourth low-end converter 7 include at least one of a grid commutated converter or a voltage source converter.
  • the various switches mentioned above include at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valve groups.
  • both the high-end converter and the low-end converter of the DC poles of the rectifier station 100 and the inverter station 200 are grid-converted converters, and the high-end converter and the low-end converter are connected to the same AC grid, then Conventional UHV DC transmission system.
  • both the high-end converter and the low-end converter of the DC poles of the rectifier station 100 and the inverter station 200 are grid-commutated converters, and the high-end converter and the low-end converter are connected to different AC power grids, they are divided Layer access to UHV DC transmission system.
  • the first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter of the first DC pole I110 and the second DC pole II120 of the rectifier station 100 3 are power grid commutated converters
  • the third high-end converter of the third DC pole I210 and the fourth DC pole II220 of the inverter station 200 5 are both voltage source converters, which are hybrid UHV DC transmission systems mixed between stations.
  • first high-end converter, the first low-end converter, the second high-end converter, and the second low-end converter of the first DC pole I110 and the second DC pole II120 of the rectifier station 100 are all grids
  • the commutation converter, the third high-end converter 5 and the fourth high-end converter 8 of the third DC pole I210 and the fourth DC pole II220 of the inverter station 200 are the grid commutation converters
  • the converter 6 and the fourth low-end converter 7 are voltage source converters, which are hybrid UHV DC transmission systems mixed within the poles.
  • the rectifier station 100 is connected to the ground electrode 115 through the ground electrode line 114.
  • the inverter station 200 is connected to the ground electrode 215 through the ground electrode line 214.
  • the first AC system 140 of the rectifier station 100 connects the first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter 3 through its first high-end converter 1, the first low-end converter 2, the second high-end converter 4, and the second low-end converter 3.
  • the alternating current is converted into direct current, and is transmitted to the inverter station 200 through the DC lines 150 and 160.
  • the inverter station 200 passes its third high-end converter 5, third low-end converter 6, fourth high-end converter 8 and second
  • the four-low-end converter 7 converts the DC power into AC power and sends it to the second AC system 240 of the inverter station 200, thereby realizing the forward transmission of DC power.
  • the converter of the rectifier station generally runs under current control, and the converter of the inverter station generally runs under voltage control or maximum firing angle control (AMAX). It should be pointed out that the maximum firing angle control (AMAX) is only applicable to grid-commutated converters, not to voltage source converters.
  • the analog signals collected by the rectifier station 100 and the inverter station 200 are: the high-voltage bus current IDC1P and the low-voltage bus current IDC1N on the DC side of the high-end converter, the high-voltage bus current IDC2P and the low-voltage bus current on the DC side of the low-end converter IDC2N, extremely neutral bus current IDNC, extremely bus current IDL, extremely bus voltage UDL and extremely neutral bus voltage UDN.
  • Fig. 2 is a schematic flowchart of a method for controlling a ground fault in a valve zone of an UHV DC high-end converter provided by an embodiment of the present application.
  • the UHV DC power transmission system includes at least one rectifier station and at least one inverter station.
  • the rectifier station and the inverter station include single DC pole or double DC pole.
  • the DC pole includes at least two converters connected in series, and the high-end converter is a converter close to the pole bus.
  • Full valve group operation At least two converters are operating at the DC pole.
  • a ground fault occurs in the valve area of the high-end converter: including at least one of a ground fault occurs in the high-end converter, a ground fault occurs in the connecting line between the high-end converter and the converter transformer, and a ground fault occurs in the valve side winding of the converter transformer.
  • Ground fault is detected in the valve area of the high-end converter: It is detected that the absolute value of the difference between the high-voltage bus current and the low-voltage bus current on the DC side of the high-end converter is greater than the set current difference.
  • the ground fault in the valve area of the high-end converter is judged by the converter differential protection action.
  • the criterion formula for the converter differential protection action is as follows.
  • IDiff_v
  • IRes_v
  • IDC1P is the high-voltage bus current on the DC side of the high-end converter
  • IDC1N is the low-voltage bus current on the DC side of the high-end converter
  • Iv_set is the starting current setting value
  • kv_set is the ratio coefficient.
  • the control method is as follows.
  • the high-end converter is a voltage source converter
  • the high-end converter is controlled to be blocked to immediately stop sending trigger pulses
  • the second bypass switch is closed, the converter transformer inlet switch of the high-end converter is tripped, and the second bypass is The switch connects the positive and negative poles of the high-side inverter.
  • the first high-end converter 1 Take the first high-end converter 1 as an example. If the first high-end converter 1 is a voltage source converter, the first high-end converter 1 is controlled to be blocked to immediately stop the trigger pulse, and the first high-end converter is skipped. 1 the first high-end converter transformer inlet switch 131, after the first high-end converter transformer inlet switch 131 is tripped, close the first high-end valve group second bypass switch 12, the first high-end valve group second bypass switch 12 Connect the anode and cathode of the first high-side inverter 1.
  • the high-end converter is controlled to lock and select different blocking methods according to the operation in the rectification or inverter state.
  • the high-end converter is in rectification operation, choose either of the following two blocking modes: the first blocking mode of the rectifier-side converter and the second blocking mode of the rectifier-side converter.
  • the high-end converter is in inverter operation, select either of the following two locking methods: the first locking method of the inverter-side converter and the second locking method of the inverter-side converter.
  • the rectifier station 100 if the first high-end converter 1 of the first DC pole I110 is rectified and operated, if the first blocking method of the rectifier side converter is adopted: the first DC pole I110 of the rectifier station 100 The high-end converter 1 immediately stops sending trigger pulses, and the third high-end converter 5 of the third DC pole I210 of the inverter station 200 controls the trigger angle to be 90 degrees; the first high-end converter of the first DC pole I110 of the rectifier station 100 The inverter 1 trips the first high-end converter transformer inlet switch 131, closes the first high-end valve group and the second bypass switch 12, and the third high-end converter 5 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, Close the second bypass switch 52.
  • the rectifier station 100 if the first high-end converter 1 of the first DC pole I110 is rectified and operated, if the second blocking method of the rectifier side converter is adopted: the first DC pole I110 of the rectifier station 100
  • the high-end converter 1 is put into the bypass pair, the first high-end valve group and the second bypass switch 12 are closed, the first high-end converter transformer inlet switch 131 is tripped, and the third high-end converter of the third DC pole I210 of the inverter station 200
  • the inverter 5 controls the trigger angle to be 90 degrees; the third high-end inverter 5 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, and the second bypass switch 52 of the third high-end valve group is closed.
  • the third high-end converter 5 of the third DC pole I210 is in inverter operation, if the first blocking method of the inverter side converter is adopted: the third DC pole I210 of the inverter station 200
  • the third high-end converter 5 trips on the third high-end converter transformer inlet switch 231, and the third high-end converter transformer inlet switch 231 trips and puts into the bypass pair, closing the third high-end valve group and the second bypass switch 52 ,
  • the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 controls the firing angle to be 90 degrees; the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 is put into the bypass pair, closing the first The second bypass switch 12 of the high-end valve group.
  • the third high-end converter 5 of the third DC pole I210 is in inverter operation, if the second blocking method of the inverter side converter is adopted: the third DC pole I210 of the inverter station 200
  • the third high-end converter 5 is put into the bypass pair, the second bypass switch 52 of the third high-end valve group is closed, and the third high-end converter transformer inlet switch 231 is tripped at the same time.
  • the first DC pole I110 of the rectifier station 100 A high-end converter 1 controls the trigger angle to be 90 degrees; the first high-end converter 1 of the first DC pole I110 of the rectification station 100 is put into the bypass pair, and the first high-end valve group and the second bypass switch 12 are closed.
  • the DC currents are equal.
  • the first low-side converter 2 uses current control to control DC current (such as IDL), and the third low-side converter 6 of the third DC pole I210 of the inverter station 200 (inverter side) uses voltage control. To control the pole bus voltage UDL of the first DC pole I110 of the rectifier station 100 to be zero.
  • the first low-end converter 2 uses voltage control to control the pole bus voltage UDL of the first DC pole I110 of the rectifier station 100 to zero, and sends the fault information to the inverter station 200.
  • the third low-end converter 6 of the three DC pole I210 uses current control to control the DC current (such as IDL).
  • the third low-side converter 6 uses voltage control to control the pole bus voltage UDL of the third DC pole I210 of the inverter station 200 to zero, and sends the fault information to the rectifier station 100, which is the first straight line of the rectifier station 100.
  • the first low-side converter 2 of the current pole I110 controls the DC current (such as IDL) to be equal.
  • the third low-side converter 6 uses current control to control DC current (such as IDL), and the first low-side converter 2 of the first DC pole I110 of the rectifier station 100 uses voltage control to control the inverter station. 200
  • the pole bus voltage UDL of the third DC pole I210 is zero.
  • the DC current of the low-end converter controlling the DC pole where the high-end converter is located is equal to the DC current of the corresponding poles of other stations except the station where the high-end converter is located, using the following method.
  • the low-end converter uses current control to control the DC current, and the converters of the corresponding poles of other stations use current control to control the DC current.
  • the low-end converters and the converters of the corresponding poles of other stations use the same DC current reference value. .
  • the DC current of the low-end converter is at least one of the high-voltage bus current and the low-voltage bus current on the DC side of the low-end converter, and the DC current of the corresponding pole of other stations is the pole bus current of the corresponding pole of other stations, and the converter DC At least one of the high-voltage bus current and the low-voltage bus current on the side.
  • the first low-side converter 2 uses current control to control DC current (such as IDL)
  • the third low-side converter 6 uses current control to control DC current (such as IDL)
  • the first low-side converter 2 and the third low-side converter 6 use the same current reference value.
  • the first low-side converter 2 uses current control to control DC current (such as IDL)
  • the third low-side converter 6 uses current control to control DC current (such as IDL)
  • the first low-side converter 2 and the third low-side converter 6 use the same current reference value.
  • the DC current reference value of the converter using current control is determined according to the active power, reactive power or ground current limit requirements of the UHV DC transmission system.
  • the first high-end converter 1 that is faulty is isolated by the following control: Close the first high-end valve group where the first high-end converter 1 is located
  • the first bypass switch 11 of the high-end valve group separates the second bypass switch 12 of the first high-end valve group, the first high-end valve group valve group switch 14 and the first high-end valve group bus switch 13.
  • breaking current of the second bypass switch 12 of the first high-side valve group is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-side converter 1 is greater than the low-voltage bus current IDC1N, first disconnect the first high-side valve group bus switch 13 , Then separate the first high-end valve group and the second bypass switch 12, and then separate the first high-end valve group valve group switch 14.
  • breaking current of the first high-end valve group and the second bypass switch 12 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first separate the first high-end valve group switch 14. Then separate the second bypass switch 12 of the first high-end valve group, and then separate the bus switch 13 of the first high-end valve group.
  • breaking current of the first high-end valve group switch 14 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is greater than the low-voltage bus current IDC1N, first disconnect the first high-end valve group bus switch 13, and then The first high-end valve group valve group switch 14 is separated, and then the first high-end valve group second bypass switch 12 is separated.
  • breaking current of the first high-end valve group switch 14 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first separate the first high-end valve group and the second bypass switch 12. Then separate the first high-end valve group valve group switch 14, and then separate the first high-end valve group bus switch 13.
  • breaking current of the first high-side valve group bus switch 13 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-side converter 1 is greater than the low-voltage bus current IDC1N, first separate the first high-side valve group and the second bypass switch 12 , Then separate the first high-end valve group bus switch 13, and then separate the first high-end valve group valve group switch 14.
  • breaking current of the first high-end valve group bus switch 13 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first open the first high-end valve group valve group switch 14, and then Separate the bus switch 13 of the first high-end valve group, and then separate the second bypass switch 12 of the first high-end valve group.
  • the low-end converter resumes normal operation as the low-end converter operates in accordance with normal DC voltage and normal DC current, and controls the pole bus voltage of the DC pole to the normal DC voltage.
  • the high-end converter detects a ground fault in the valve area of the high-end converter, increase the range of the range protection differential current setting of the high-end converter or increase the The range protection delay setting of the high-end converter or the shielded range protection, the differential protection of the shielded valve group connection line, and the DC low voltage protection. After the high-end converter is isolated, the range protection and valve group connection lines are opened. Differential protection, DC low voltage protection.
  • Dual DC pole balance control directs the current of the normal operating pole to the pole bus of the faulty pole, so as to prevent the current of the normal operating pole from flowing into the fault point too much, so as to ensure the operation of more converters and avoid the loss of large DC Transmission power.
  • FIG. 3 is a schematic flowchart of another method for controlling a ground fault in the valve zone of a UHV DC high-end converter provided by an embodiment of the present application.
  • the UHV DC power transmission system includes at least one rectifier station and at least one inverter station.
  • the rectifier station and the inverter station include single DC pole or double DC pole.
  • the DC pole includes at least two converters connected in series, and the high-end converter is a converter close to the pole bus.
  • Full valve group operation At least one converter is running in addition to the high-end converter in the DC pole where the high-end converter is located.
  • a ground fault occurs in the valve area of the high-end converter: including at least one of a ground fault occurs in the high-end converter, a ground fault occurs in the connecting line between the high-end converter and the converter transformer, and a ground fault occurs in the valve side winding of the converter transformer.
  • Ground fault is detected in the valve area of the high-end converter: It is detected that the absolute value of the difference between the high-voltage bus current and the low-voltage bus current on the DC side of the high-end converter is greater than the set current difference.
  • the ground fault in the valve area of the high-end converter is judged by the converter differential protection action.
  • the criterion formula for the converter differential protection action is as follows.
  • IDiff_v
  • IRes_v
  • IDC1P is the high-voltage bus current on the DC side of the high-end converter
  • IDC1N is the low-voltage bus current on the DC side of the high-end converter
  • Iv_set is the starting current setting value
  • k_set is the ratio coefficient.
  • the control method is as follows.
  • the high-end converter is a voltage source converter
  • the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 as an example, if the first high-end converter 1 is a voltage source converter, the first high-end converter 1 is controlled to be blocked to stop transmission immediately Trigger the pulse to close the first high-end valve group and the second bypass switch 12, and trip the first high-end converter transformer inlet switch 131 of the first high-end converter 1.
  • the first high-end valve group and the second bypass switch 12 are connected to the first high-end converter transformer.
  • the high-end converter is a grid-commutated converter
  • control the blocking of the high-end converter to select different blocking methods according to the rectification or inverter operation.
  • the high-end converter is in inverter operation, choose either of the following two blocking modes: the first blocking mode of the inverter-side converter and the second blocking mode of the inverter-side converter.
  • the rectifier station 100 if the first high-end converter 1 of the first DC pole I110 is rectified and operated, if the first blocking method of the rectifier side converter is adopted: the first blocking method of the first DC pole I110 of the rectifier station 100 The high-end converter 1 immediately stops sending trigger pulses, and the third high-end converter 5 of the third DC pole I210 of the inverter station 200 controls the trigger angle to be 90 degrees; the first high-end converter of the first DC pole I110 of the rectifier station 100 The inverter 1 trips the first high-end converter transformer inlet switch 131, closes the first high-end valve group and the second bypass switch 12, and the third high-end converter 5 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, Close the second bypass switch 52 of the third high-end valve group.
  • the rectifier station 100 if the first high-end converter 1 of the first DC pole I110 is rectified and operated, if the second blocking method of the rectifier side converter is adopted: the first DC pole I110 of the rectifier station 100
  • the high-end converter 1 is put into the bypass pair, the first high-end valve group and the second bypass switch 12 are closed, and at the same time, the first high-end converter transformer inlet switch 131 and the third high-end of the third DC pole I210 of the inverter station 200 are opened.
  • the inverter 5 controls the trigger angle to be 90 degrees; the third high-end inverter 5 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, and the second bypass switch 52 of the third high-end valve group is closed.
  • the third high-end converter 5 of the third DC pole I210 is in inverter operation, if the first blocking method of the inverter side converter is adopted: the third DC pole I210 of the inverter station 200
  • the third high-end converter 5 trips on the third high-end converter transformer inlet switch 231, and the third high-end converter transformer inlet switch 231 trips and puts into the bypass pair, closing the third high-end valve group and the second bypass switch 52 ,
  • the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 controls the firing angle to be 90 degrees; the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 is put into the bypass pair, closing the first The second bypass switch 12 of the high-end valve group.
  • the third high-end converter 5 of the third DC pole I210 is in inverter operation, if the second blocking method of the inverter side converter is adopted: the third DC pole I210 of the inverter station 200 The third high-end converter 5 is put into the bypass pair, the second bypass switch 52 of the third high-end valve group is closed, and the third high-end converter transformer inlet switch 231 is tripped at the same time.
  • the first DC pole I110 of the rectifier station 100 The trigger angle of the three high-end converter 5 is controlled to be 90 degrees; the first high-end converter 1 of the first DC pole I110 of the rectification station 100 is put into the bypass pair, and the first high-end valve group and the second bypass switch 12 are closed.
  • control the phase shift of the converter on the rectification side of the DC pole of the station where the high-end converter is located that is, control the trigger angle to be 164 degrees.
  • the corresponding low-end converters that control the DC poles of other stations are controlled or phase shifted at the maximum firing angle.
  • the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 detects a ground fault in the valve area of the first high-end converter 1, the first high-end converter 1 is controlled to lock, and the inverter station 200
  • the third high-end converter 5 of the third DC pole I210 is out of operation, and the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 is controlled to shift phase, that is, the trigger angle is controlled to be 164 degrees.
  • the third low-side converter 6 of the third DC pole I210 of the inverter station 200 operates under the maximum firing angle control.
  • the third high-end converter 5 of the third DC pole I210 of the inverter station 200 detects a ground fault in the valve area of the third high-end converter 5
  • the third high-end converter 5 is controlled to lock, and at the same time the rectifier station 100th
  • the first high-end converter 1 of a DC pole I110 is out of operation
  • the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 is controlled to shift phase, that is, the firing angle is controlled to be 164 degrees
  • the third low-end converter 6 of the third direct current pole I210 runs at the maximum firing angle control.
  • the faulty first high-end converter 1 is isolated by the following control: close the first bypass switch 11 of the first high-end valve group, and separate the first The high-end valve group second bypass switch 12, the first high-end valve group valve group switch 14, and the first high-end valve group bus switch 13.
  • breaking current of the second bypass switch 12 of the first high-side valve group is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-side converter 1 is greater than the low-voltage bus current IDC1N, first disconnect the first high-side valve group bus switch 13 , Then separate the first high-end valve group and the second bypass switch 12, and then separate the first high-end valve group valve group switch 14.
  • breaking current of the first high-end valve group and the second bypass switch 12 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first separate the first high-end valve group switch 14. Then separate the second bypass switch 12 of the first high-end valve group, and then separate the bus switch 13 of the first high-end valve group.
  • breaking current of the first high-end valve group switch 14 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is greater than the low-voltage bus current IDC1N, first disconnect the first high-end valve group bus switch 13, and then The first high-end valve group valve group switch 14 is separated, and then the first high-end valve group second bypass switch 12 is separated.
  • breaking current of the first high-end valve group switch 14 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first separate the first high-end valve group and the second bypass switch 12. Then separate the first high-end valve group valve group switch 14, and then separate the first high-end valve group bus switch 13.
  • breaking current of the first high-side valve group bus switch 13 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-side converter 1 is greater than the low-voltage bus current IDC1N, first separate the first high-side valve group and the second bypass switch 12 , Then separate the first high-end valve group bus switch 13, and then separate the first high-end valve group valve group switch 14.
  • breaking current of the first high-end valve group bus switch 13 is the largest, and the high-voltage bus current IDC1P on the DC side of the first high-end converter 1 is less than the low-voltage bus current IDC1N, first open the first high-end valve group valve group switch 14, and then Separate the bus switch 13 of the first high-end valve group, and then separate the second bypass switch 12 of the first high-end valve group.
  • the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 (rectifier side) resumes normal operation as the first low
  • the end converter 2 operates according to the normal DC voltage and the normal DC current, and controls the polar neutral bus current of the first DC pole I110 to be a normal DC current.
  • the control method is that the first low-end converter 2 uses current control to control the polar neutral bus current to a normal DC current, and the third low-end converter 5 uses voltage control to control the pole bus voltage to a normal voltage.
  • the high-end converter detects a ground fault in the valve area of the high-end converter, increase or increase the range protection differential current setting of the DC pole where the high-end converter is located.
  • the differential current of the range protection is the difference between the sum of the polar neutral bus current, the DC filter current, the polar neutral bus impulse capacitor current and the polar neutral bus arrester current and the polar bus current.
  • the differential current of the valve group connection line is the difference between the low-voltage bus current on the DC side of the high-end converter and the high-voltage bus current on the DC side of the low-end converter. The low DC voltage is achieved by judging that the bus voltage is low.
  • the low-end converter is controlled to restart once, if the low-end converter restarts successfully , The low-end converter resumes normal operation. If the low-end converter fails to restart, the low-end converter continues to keep phase shifting.
  • Fig. 4 is a schematic structural diagram of a ground fault control device for a valve zone of an UHVDC high-end converter provided by an embodiment of the present application.
  • the control device 300 is used to control the UHV DC power transmission system, and includes a detection unit 310 and a control unit 320.
  • the detection unit 310 detects the high-voltage bus current IDC1P and low-voltage bus current IDC1N of the high-end converter, detects the extremely neutral bus current IDNC of the dual DC poles, and detects the high-voltage bus current IDC2P, low-voltage bus current IDC2N and the pole bus of the low-end converter Current IDL, detect the pole bus voltage UDL and the pole neutral bus voltage UDN.
  • control unit 320 determines that the full valve group of the DC pole where the high-end converter of the UHV DC transmission system is located is running and detects that the valve area of the high-end converter has a ground fault, it selects any one of the following two control strategies.
  • Method 1 Control the blocking of the high-end converter; control the pole bus voltage of the DC pole where the high-end converter is located to be zero or the DC current of the low-end converter and the DC of the corresponding poles of other stations except the station where the high-end converter is located If the current is equal, the above-mentioned low-end converter is a converter close to the extremely neutral bus; isolate the high-end converter; control the low-end converter to resume operation.
  • Method 2 Control the high-end converter to lock; control the phase shift of the converter operating on the rectifier side of the DC pole where the high-end converter is located; isolate the high-end converter; control the converter on the rectifier side to return to normal after the phase shift is removed run.

Abstract

本申请提供特高压直流高端换流器阀区接地故障控制方法及控制装置。特高压直流输电系统包括至少一个整流站与至少一个逆变站，整流站与逆变站包括单直流极或双直流极，直流极包括串联连接的至少两个换流器，当高端换流器所在直流极为全阀组运行，并检测到高端换流器的阀区发生接地故障时，所述控制方法包括：控制高端换流器闭锁；控制流过故障点的电流最小；隔离高端换流器；控制特高压直流输电系统恢复正常运行。

Description

特高压直流高端换流器阀区接地故障控制方法及控制装置 技术领域
本申请涉及高压直流输电技术领域，具体涉及特高压直流高端换流器阀区接地故障控制方法及其控制装置。
背景技术
特高压直流输电系统一般采用两个换流器串联组成一个直流极，根据现有的工程分为常规特高压直流输电系统、分层接入特高压直流输电系统和混合特高压直流输电系统。
常规特高压直流输电系统为一个直流极的高、低端换流器都为电网换相换流器，且接入同一个交流电网。分层接入特高压直流输电系统为一个直流极的高、低端换流器都为电网换相换流器，且分别接入两个不同的交流电网。混合特高压直流输电系统分为几种：站间混合、极间混合和极内混合，站间混合的混合特高压直流输电系统采用电压源换流器的换流站一个直流极的高、低端换流器都为电压源换流器，极间混合的混合特高压直流输电系统采用电压源换流器的直流极的高、低端换流器都为电压源换流器，极内混合的混合特高压直流输电系统采用电网换相换流器和电压源换流器的直流极的高、低端换流器分别为电网换相换流器和电压源换流器。
当特高压直流输电系统双直流极平衡运行时，换流器检测到换流器阀区接地故障时，现有技术通过闭锁整个直流极来隔离故障，故障隔离后，采用单极大地继续运行，或者转金属回线运行，或者通过重启直流极的非故障换流器来实现双直流极平衡运行。
现有技术主要存在以下几个问题：闭锁整个直流极后，接地极线将流过很大电流，容易导致附近变电站的变压器有直流偏磁，引起变压器饱和；闭锁整个直流极后，如果输送功率较大，会损失较多的直流功率；闭锁整个直流极后，故障点会流过更多的故障电流。
因此，当特高压直流输电系统双直流极平衡运行时，换流器检测到换流器阀区接地故障时，应尽量在某些工况下不闭锁整个直流极，而只是闭锁故障的换流器。
发明内容
本申请实施例提供一种特高压直流高端换流器阀区接地故障控制方法，应用于特高压直流输电系统的直流极的高端换流器，所述特高压直流输电系统包括至少一个整流站与至少一个逆变站，所述整流站与所述逆变站包括单直流极或双直流极，所述直流极包括串联连接的至少两个换流器，所述高端换流器为靠近极母线的换流器，当所述高端换流器所在直流极为全阀组运行，并检测到所述高端换流器的阀区发生接地故障时，所述控制方法包括：控制所述高端换流器闭锁；控制流过故障点的电流最小；隔离所述高端换流器；控制 所述特高压直流输电系统恢复正常运行。
根据一些实施例，所述高端换流器或所述低端换流器包括电网换相换流器或电压源换流器中的至少一种。
根据一些实施例，所述双直流极运行包括：每个所述直流极有至少一个换流器在运行；所述全阀组运行包括：所述高端换流器所在直流极除所述高端换流器之外还至少有一个换流器在运行。
根据一些实施例，所述高端换流器的阀区发生接地故障，包括：所述高端换流器发生接地故障、所述高端换流器与换流变压器之间连接线发生接地故障、所述换流变压器阀侧绕组发生接地故障的至少一种。
根据一些实施例，所述检测到所述高端换流器的阀区发生接地故障，包括：
检测到所述高端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
根据一些实施例，如果所述高端换流器为电压源换流器，所述控制高端换流器闭锁包括：控制所述高端换流器停发触发脉冲，闭合所述高端换流器所在高端阀组的第二旁通开关，跳开所述高端换流器的换流变压器进线开关，所述第二旁通开关连接所述高端换流器的正极和负极。
根据一些实施例，如果所述高端换流器为电网换相换流器，所述控制所述高端换流器闭锁包括：当所述高端换流器整流运行时，选择整流侧换流器第一种闭锁方式或整流侧换流器第二种闭锁方式；当所述高端换流器逆变运行时，选择逆变侧换流器第一种闭锁方式和逆变侧换流器第二种闭锁方式。
根据一些实施例，所述整流侧换流器第一种闭锁方式包括：控制整流运行的所述高端换流器停发触发脉冲，相应的逆变运行的换流器控制触发角为90度；控制跳开所述高端换流器的换流变压器进线开关，闭合所述高端换流器所在高端阀组的第二旁通开关，相应的逆变运行的换流器投入旁通对，闭合旁通开关，所述第二旁通开关连接所述高端换流器的阳极和阴极。
根据一些实施例，所述整流侧换流器第二种闭锁方式包括：控制所述高端换流器投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，同时跳开所述高端换流器的换流变压器进线开关，相应的逆变运行的换流器控制触发角为90度，所述第二旁通开关连接所述高端换流器的阳极和阴极；控制所述相应的逆变运行的换流器投入旁通对，闭合旁通开关。
根据一些实施例，所述逆变侧换流器第一种闭锁方式包括：控制跳开逆变运行的所述高端换流器的换流变压器进线开关，投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述高端换流器的阳极和阴极；控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
根据一些实施例，所述逆变侧换流器第二种闭锁方式包括：控制逆变运行的所述高端 换流器投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，同时跳开所述高端换流器连接的换流变压器进线开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
根据一些实施例，所述控制流过故障点的电流最小，包括：控制所述高端换流器所在直流极的极母线电压为零或控制所述高端换流器所在直流极的低端换流器直流电流与除所述高端换流器所在站之外的其他站相应极的直流电流相等，或者控制所述高端换流器所在直流极的整流侧的运行的换流器移相，所述低端换流器为靠近极中性母线的换流器。
根据一些实施例，如果故障发生在整流侧，所述控制所述高端换流器所在直流极的极母线电压为零，包括：所述低端换流器采用电流控制来控制直流电流，逆变侧相应的换流器采用电压控制来控制整流侧的极母线电压为零；或者所述低端换流器采用电压控制来控制整流侧的极母线电压为零，并将故障信息发送到逆变侧，逆变侧相应的换流器采用电流控制来控制直流电流。
根据一些实施例，如果故障发生在逆变侧，所述控制所述高端换流器所在直流极的极母线电压为零，包括：所述低端换流器采用电压控制来控制逆变侧的极母线电压为零，并将故障信息发送到整流侧，整流侧相应的换流器采用电流控制来控制直流电流；或者所述低端换流器采用电流控制来控制直流电流，整流侧相应的换流器采用电压控制来控制逆变侧的极母线电压为零。
根据一些实施例，所述控制所述高端换流器所在直流极的低端换流器直流电流与除所述高端换流器所在站之外的其他站相应极的直流电流相等，包括：所述低端换流器采用电流控制来控制直流电流，所述其他站相应极采用电流控制来控制直流电流，所述低端换流器与所述其他站相应极采用相同的直流电流参考值；所述低端换流器的直流电流为所述低端换流器直流侧的高压母线电流、低压母线电流的至少一种，如果所述其他站只有一个，所述其他站相应极的直流电流为所述其他站相应极的极母线电流、换流器直流侧的高压母线电流、低压母线电流的至少一种，如果所述其他站有两个及以上，所述其他站相应极的直流电流为所述其他站相应极的极母线电流之和、换流器直流侧的高压母线电流之和、低压母线电流之和的至少一种。
根据一些实施例，所述采用电流控制的换流器的直流电流参考值根据特高压直流输电系统的有功功率、无功功率或入地电流限制需求确定。
根据一些实施例，所述隔离所述高端换流器包括：闭合所述高端换流器所在高端阀组的第一旁通开关，分开所述高端阀组的第二旁通开关、阀组开关和母线开关，所述第一旁通开关与所述高端换流器并联连接，所述第二旁通开关连接所述高端换流器的两端，所述阀组开关连接所述高端换流器与阀组连接线，所述母线开关连接所述高端换流器与极母线。
根据一些实施例，如果所述第二旁通开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述母线开关，再分开所述第二旁通开关，后分开所述阀组开关；如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先 分开所述阀组开关，再分开所述第二旁通开关，后分开所述母线开关。
根据一些实施例，如果所述阀组开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述母线开关，再分开所述阀组开关，后分开所述第二旁通开关；如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先分开所述第二旁通开关，再分开所述阀组开关，后分开所述母线开关。
根据一些实施例，如果所述母线开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述第二旁通开关，再分开所述母线开关，后分开所述阀组开关；如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先分开所述阀组开关，再分开所述母线开关，后分开所述第二旁通开关。
根据一些实施例，所述控制所述特高压直流输电系统恢复正常运行，包括：控制所述低端换流器恢复运行，或者控制所述整流侧的换流器解除移相后恢复正常运行。
根据一些实施例，所述控制所述低端换流器恢复正常运行，包括：所述低端换流器与所述其他站相应极的换流器中，一个换流器采用电压控制或最大触发角控制，其他换流器采用电流控制，控制所述低端换流器按照正常直流电压和正常直流电流运行；所述控制所述整流侧的换流器解除移相后恢复正常运行，包括：所述整流侧的换流器解除移相后，所述低端换流器与所述其他站相应极的换流器中，一个换流器采用电压控制或最大触发角控制，其他换流器采用电流控制，控制所述低端换流器按照正常直流电压和正常直流电流运行。
根据一些实施例，所述隔离所述高端换流器之前，还包括：增大所述高端换流器所在直流极的极差保护差动电流定值或者增大所述高端换流器所在直流极的极差保护延时定值或者屏蔽极差保护，直至所述高端换流器隔离。
根据一些实施例，所述控制流过故障点的电流最小之后，还包括：经过一定的去游离时间后，控制所述整流侧的换流器重启一次；如果重启成功，则所述整流侧的换流器恢复正常运行；如果重启失败，则所述整流侧的换流器继续控制流过故障点的电流最小。
本申请实施例还提供一种特高压直流高端换流器阀区接地故障控制装置，应用如上所述特高压直流高端换流器阀区接地故障控制方法，所述控制装置包括检测单元和控制单元，所述检测单元用于检测所述高端换流器的高压母线电流和低压母线电流，检测双直流极的极中性母线电流，检测所述低端换流器的高压母线电流、低压母线电流和极母线电流，检测极母线电压和极中性母线电压；所述控制单元用于判断所述特高压直流输电系统的所述高端换流器所在直流极为全阀组运行，并检测到所述高端换流器的阀区发生接地故障时，控制所述高端换流器闭锁；控制流过故障点的电流最小；隔离所述高端换流器；控制所述特高压直流输电系统恢复正常运行。
本申请实施例提供的技术方案，当特高压直流输电系统双直流极运行时，换流器检测到换流器阀区接地故障时，不闭锁整个直流极，而只是闭锁故障的换流器，通过控制流过 故障点的电流最小，如控制双直流极平衡控制，将正常运行极的电流导入到故障极的极母线上，从而避免正常运行极的电流过多地流入到故障点，或者通过将整流侧的换流器移相，阻断电流流入到故障点，从而保证更多换流器运行，避免损失较大直流输送功率。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是本申请实施例提供的一种特高压直流输电系统的主回路示意图；
图2是本申请实施例提供的一种特高压直流高端换流器阀区接地故障控制方法流程示意图；
图3是本申请实施例提供的另一种特高压直流高端换流器阀区接地故障控制方法流程示意图；
图4是本申请实施例提供的一种特高压直流高端换流器阀区接地故障控制装置的结构示意图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
应当理解，本申请的权利要求、说明书及附图中的术语“第一”、“第二”、“第三”、“第四”等是用于区别不同对象，而不是用于描述特定顺序。本申请的说明书和权利要求书中使用的术语“包括”指示所描述特征、整体、步骤、操作、元素和/或组件的存在，但并不排除一个或多个其它特征、整体、步骤、操作、元素、组件和/或其集合的存在或添加。
图1是本申请实施例提供的一种特高压直流输电系统的主回路示意图。
特高压直流输电系统主回路包括整流站100、逆变站200、第一直流线路150、第二直流线路160、整流站接地极线路114、整流站接地极115和逆变站接地极线路214、逆变站接地极215。
整流站100包括第一第一直流极I110、第二第二直流极II120、第一交流滤波器组118、第一交流系统140及换流变压器进线开关和金属回线转换开关113。
第一直流极I110包括第一高端阀组111、第一低端阀组112、第一高端换流变压器116、第一低端换流变压器117、第一直流滤波器93和第一平波电抗器91。第一高端阀组111和第一低端阀组112为串联连接。
第一高端阀组111包括第一高端换流器1、第一高端阀组第一旁通开关11、第一高端阀组第二旁通开关12、第一高端阀组母线开关13、第一高端阀组阀组开关14。第一高端阀组第一旁通开关11与第一高端换流器1并联连接，第一高端阀组第二旁通开关12连接第一高端换流器1的两端，第一高端阀组阀组开关14连接第一高端换流器1与阀组连接线，第一高端阀组母线开关13连接第一高端换流器1与极母线。
第一低端阀组112包括第一低端换流器2、第一低端阀组第一旁通开关21、第一低端阀组第二旁通开关22、第一低端阀组阀组开关23、第一低端阀组母线开关24。第一低端阀组第一旁通开关21与第一低端换流器2并联连接，第一低端阀组第二旁通开关22连接第二低端换流器2的两端，第一低端阀组阀组开关23连接第一低端换流器2与阀组连接线，第一低端阀组母线开关24连接第一低端换流器2与极中性母线。
第一高端换流器1和第一低端换流器2包括电网换相换流器或电压源换流器的至少一种。
电网换相换流器包括但不限于六脉动桥式电路、十二脉动桥式电路的至少一种。六脉动桥式电路和十二脉动桥式电路包括但不限于不可关断的半控型功率半导体器件，一般为晶闸管器件。
电压源换流器包括但不限于两电平换流器、二极管箝位型多电平换流器、模块化多电平换流器MMC、混合多电平换流器HMC、两电平级联型换流器CSL、堆叠式两电平换流器CTL的至少一种。电压源换流器包括但不限于可关断的全控型功率半导体器件。上述模块化多电平换流器MMC包括但不限于半桥子模块结构的模块化多电平换流器MMC、全桥子模块结构的模块化多电平换流器MMC、半桥和全桥混合子模块结构的模块化多电平换流器MMC的至少一种。
第二直流极II120包括第二高端阀组121、第二低端阀组122、第二低端换流变压器126、第二高端换流变压器127、第二直流滤波器94和第二平波电抗器92。第二高端阀组121和第二低端阀组122为串联连接。
第二高端阀组121包括第二高端换流器4、第二高端阀组第一旁通开关41、第二高端阀组第二旁通开关42、第二高端阀组阀组开关43、第二高端阀组母线开关44。第二高端阀组第一旁通开关41与第二高端换流器4并联连接，第二高端阀组第二旁通开关42连接第二高端换流器4的两端，第二高端阀组阀组开关43连接第二高端换流器4与阀组连接线，第二高端阀组母线开关44连接第二高端换流器4与极母线。
第二低端阀组122包括第二低端换流器3、第二低端阀组第一旁通开关31、第二低端阀组第二旁通开关32、第二低端阀组母线开关33、第二低端阀组阀组开关34。第二低端阀组第一旁通开关31与第二低端换流器3并联连接，第二低端阀组第二旁通开关32连接第二低端换流器3的两端，第二低端阀组阀组开关34连接第二低端换流器3与阀组连接线，第二低端阀组母线开关33连接第二低端换流器3与极中性母线。
第二高端换流器4和第二低端换流器3包括电网换相换流器或电压源换流器的至少一种。
逆变站200包括第三直流极I210、第四直流极II220、第二交流滤波器组218和第二交流系统240及换流变压器进线开关。
第三直流极I210包括第三高端阀组211、第三低端阀组212、第三高端换流变压器216、第三低端换流变压器217、第三直流滤波器97和第三平波电抗器95。第三高端阀组211和第三低端阀组212为串联连接。
第三高端阀组211包括第三高端换流器5、第三高端阀组第一旁通开关51、第三高端阀组第二旁通开关52、第三高端阀组母线开关53、第三高端阀组阀组开关54。第三高端阀组第一旁通开关51与第三高端换流器5并联连接，第三高端阀组第二旁通开关52连接第三高端换流器5的两端，第三高端阀组阀组开关54连接第三高端换流器5与阀组连接线，第三高端阀组母线开关53连接第三高端换流器5与极母线。
第三低端阀组212包括第三低端换流器6、第三低端阀组第一旁通开关61、第三低端阀组第二旁通开关62、第三低端阀组阀组开关63、第三低端阀组母线开关64。第三低端阀组第一旁通开关61与第三低端换流器6并联连接，第三低端阀组第二旁通开关62连接第三低端换流器6的两端，第三低端阀组阀组开关63连接第三低端换流器6与阀组连接线，第三低端阀组母线开关64连接第三低端换流器6与极中性母线。
第三高端换流器5和第三低端换流器6包括电网换相换流器或电压源换流器的至少一种。
第四直流极II220包括第四高端阀组221、第四低端阀组222、第四低端换流变压器226、第四高端换流变压器227、第四直流滤波器98和第四平波电抗器96。第四高端阀组221和第四低端阀组222为串联连接。
第四高端阀组222包括第四高端换流器8、第四高端阀组第一旁通开关81、第四高端阀组第二旁通开关82、第四高端阀组阀组开关83、第四高端阀组母线开关84。第四高端阀组第一旁通开关81与第四高端换流器8并联连接，第四高端阀组第二旁通开关82连接第四高端换流器8的两端，第四高端阀组阀组开关83连接第四高端换流器8与阀组连接线，第四高端阀组母线开关84连接第四高端换流器8与极母线。
第四低端阀组221包括第四低端换流器7、第四低端阀组第一旁通开关71、第四低端阀组第二旁通开关72、第四低端阀组母线开关73、第四低端阀组阀组开关74。第四低端阀组第一旁通开关71与第四低端换流器7并联连接，第四低端阀组第二旁通开关72连接第四低端换流器7的两端，第四低端阀组阀组开关74连接第四高端换流器7与阀组连接线，第四低端阀组母线开关73连接第四低端换流器7与极中性母线。
第四高端换流器8和第四低端换流器7包括电网换相换流器或电压源换流器的至少一种。
上述提到的各种开关，包括机械开关、刀闸、直流断路器、晶闸管阀组的至少一种。
如果整流站100和逆变站200的直流极的高端换流器和低端换流器都为电网换相换流器，高端换流器和低端换流器连接同一个交流电网，则为常规特高压直流输电系统。
如果整流站100和逆变站200的直流极的高端换流器和低端换流器都为电网换相换流器， 高端换流器和低端换流器连接不同交流电网，则为分层接入特高压直流输电系统。
如果整流站100的第一直流极I110和第二直流极II120的第一高端换流器1、第一低端换流器2、第二高端换流器4和第二低端换流器3都为电网换相换流器，逆变站200的第三直流极I210和第四直流极II220的第三高端换流器5、第三低端换流器6、第四高端换流器8和第四低端换流器7都为电压源换流器，则为站间混合的混合特高压直流输电系统。
如果整流站100的第一直流极I110和第二直流极II120的第一高端换流器、第一低端换流器、第二高端换流器和第二低端换流器都为电网换相换流器，逆变站200的第三直流极I210和第四直流极II220的第三高端换流器5和第四高端换流器8为电网换相换流器，第三低端换流器6和第四低端换流器7为电压源换流器，则为极内混合的混合特高压直流输电系统。
整流站100通过接地极线路114与接地极115连接。逆变站200通过接地极线路214与接地极215连接。功率正送时，整流站100的第一交流系统140通过其第一高端换流器1、第一低端换流器2、第二高端换流器4和第二低端换流器3将交流电转化为直流电，通过直流线路150、160输送到逆变站200，逆变站200通过其第三高端换流器5、第三低端换流器6、第四高端换流器8和第四低端换流器7将直流电转化为交流电送到逆变站200的第二交流系统240，从而实现直流功率正送。整流站的换流器一般运行在电流控制，逆变站的换流器一般运行在电压控制或最大触发角控制(AMAX)。需要指出的是，最大触发角控制(AMAX)仅适用于电网换相换流器，不适用于电压源换流器。
整流站100和逆变站200采集的模拟量信号为：高端换流器的直流侧的高压母线电流IDC1P、低压母线电流IDC1N，低端换流器的直流侧的高压母线电流IDC2P、低压母线电流IDC2N，极中性母线电流IDNC，极母线电流IDL，极母线电压UDL和极中性母线电压UDN。
图2是本申请实施例提供的一种特高压直流高端换流器阀区接地故障控制方法流程示意图。
特高压直流输电系统包括至少一个整流站与至少一个逆变站。整流站与逆变站包括单直流极或双直流极。直流极包括串联连接的至少两个换流器，高端换流器为靠近极母线的换流器。以下为技术术语定义。
全阀组运行：直流极至少有两个换流器在运行。
高端换流器的阀区发生接地故障：包括高端换流器发生接地故障、高端换流器与换流变压器之间连接线发生接地故障、换流变压器阀侧绕组发生接地故障的至少一种。
检测到高端换流器的阀区发生接地故障：检测到高端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
高端换流器的阀区发生接地故障通过换流器差动保护动作来判断，换流器差动保护动作判据公式如下。
IDiff_v＝|IDC1P–IDC1N|，
IRes_v＝|IDC1P+IDC1N|/2，
IDiff_v>max(Iv_set,kv_set*IRes_v)；
其中，IDC1P为高端换流器直流侧的高压母线电流，IDC1N为高端换流器直流侧的低压母线电流，Iv_set为起动电流定值，kv_set为比率系数。
当特高压直流输电系统的高端换流器所在直流极为全阀组运行，即一直流极的高端换流器和低端换流器同时运行，检测到高端换流器的阀区发生接地故障时，控制方法如下。
在S110中，控制高端换流器闭锁。
如果高端换流器为电压源换流器，控制高端换流器闭锁为立即停发触发脉冲，闭合第二旁通开关，跳开高端换流器的换流变压器进线开关，第二旁通开关连接高端换流器的正极和负极。
以第一高端换流器1为例，如果第一高端换流器1为电压源换流器，控制第一高端换流器1闭锁为立即停发触发脉冲，跳开第一高端换流器1的第一高端换流变压器进线开关131，第一高端换流变压器进线开关131跳开后，闭合第一高端阀组第二旁通开关12，第一高端阀组第二旁通开关12连接第一高端换流器1的正极和负极。
如果高端换流器为电网换相换流器，控制高端换流器闭锁根据运行于整流或逆变状态选择不同的闭锁方式。当高端换流器整流运行时，选择以下两种闭锁方式的任一种：整流侧换流器第一种闭锁方式和整流侧换流器第二种闭锁方式。当高端换流器逆变运行时，选择以下两种闭锁方式的任一种：逆变侧换流器第一种闭锁方式和逆变侧换流器第二种闭锁方式。
以整流站100为例，如果第一直流极I110的第一高端换流器1整流运行，如果采用整流侧换流器第一种闭锁方式：整流站100第一直流极I110的第一高端换流器1立即停发触发脉冲，逆变站200第三直流极I210的第三高端换流器5控制触发角为90度；整流站100第一直流极I110的第一高端换流器1跳开第一高端换流变压器进线开关131，闭合第一高端阀组第二旁通开关12，逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第二旁通开关52。
以整流站100为例，如果第一直流极I110的第一高端换流器1整流运行，如果采用整流侧换流器第二种闭锁方式：整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12，跳开第一高端换流变压器进线开关131，逆变站200第三直流极I210的第三高端换流器5控制触发角为90度；逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第三高端阀组第二旁通开关52。
以逆变站200为例，如果第三直流极I210的第三高端换流器5逆变运行，如果采用逆变侧换流器第一种闭锁方式：逆变站200第三直流极I210的第三高端换流器5跳开第三高端换流变压器进线开关231，第三高端换流变压器进线开关231跳开后投入旁通对，闭合第三高端阀组第二旁通开关52，整流站100第一直流极I110的第一高端换流器1控制触发角为90度；整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12。
以逆变站200为例，如果第三直流极I210的第三高端换流器5逆变运行，如果采用逆变侧换流器第二种闭锁方式：逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第三高端阀组第二旁通开关52，同时跳开第三高端换流变压器进线开关231，整流站100第一直流极I110 的第一高端换流器1控制触发角为90度；整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12。
在S120中，控制流过故障点的电流最小。
具体而言，控制高端换流器所在直流极的极母线电压为零或控制高端换流器所在直流极的低端换流器直流电流与除高端换流器所在站之外的其他站相应极的直流电流相等。
如果故障发生在整流站100(整流侧)第一直流极I110的第一高端换流器1时，同时逆变站200(逆变侧)第三直流极I210的第三高端换流器5退出运行，控制第一直流极I110的极母线电压UDL为零，可以选择以下两种方法中的任一种。
第一种，第一低端换流器2采用电流控制来控制直流电流(如IDL)，逆变站200(逆变侧)第三直流极I210的第三低端换流器6采用电压控制来控制整流站100第一直流极I110的极母线电压UDL为零。
第二种，第一低端换流器2采用电压控制来控制整流站100第一直流极I110的极母线电压UDL为零，并将故障信息发送到逆变站200，逆变站200第三直流极I210的第三低端换流器6采用电流控制来控制直流电流(如IDL)。
如果故障发生在逆变站200(逆变侧)第三直流极I210的第三高端换流器5时，同时整流站100(整流侧)第一直流极I110的第一高端换流器1退出运行，控制第三直流极I210的极母线电压UDL为零，选择以下两种方法中的任一种。
第一种，第三低端换流器6采用电压控制来控制逆变站200第三直流极I210的极母线电压UDL为零，并将故障信息发送到整流站100，整流站100第一直流极I110的第一低端换流器2来控制直流电流(如IDL)相等。
第二种，第三低端换流器6采用电流控制来控制直流电流(如IDL)，整流站100第一直流极I110的第一低端换流器2采用电压控制来控制逆变站200第三直流极I210的极母线电压UDL为零。
控制高端换流器所在直流极的低端换流器直流电流与除高端换流器所在站之外的其他站相应极的直流电流相等，采用如下方式。低端换流器采用电流控制来控制直流电流，其他站相应极的换流器采用电流控制来控制直流电流，低端换流器与其他站相应极的换流器采用相同的直流电流参考值。低端换流器的直流电流为低端换流器直流侧的高压母线电流、低压母线电流的至少一种，其他站相应极的直流电流为其他站相应极的极母线电流、换流器直流侧的高压母线电流、低压母线电流的至少一种。
如果故障发生在整流站100(整流侧)第一直流极I110的第一高端换流器1时，同时逆变站200(逆变侧)第三直流极I210的第三高端换流器5退出运行，第一低端换流器2采用电流控制来控制直流电流(如IDL)，第三低端换流器6采用电流控制来控制直流电流(如IDL)，第一低端换流器2和第三低端换流器6采用相同的电流参考值。
如果故障发生在逆变站200(逆变侧)第三直流极I210的第三高端换流器5时，同时整流站100(整流侧)第一直流极I110的第一高端换流器1退出运行，第一低端换流器2采用电流控制 来控制直流电流(如IDL)，第三低端换流器6采用电流控制来控制直流电流(如IDL)，第一低端换流器2和第三低端换流器6采用相同的电流参考值。
采用电流控制的换流器的直流电流参考值根据特高压直流输电系统的有功功率、无功功率或入地电流限制需求确定。
在S130中，隔离故障高端换流器。
以整流站100第一直流极I110的第一高端换流器1为例，通过以下控制隔离故障的第一高端换流器1：闭合第一高端换流器1所在高端阀组的第一高端阀组第一旁通开关11，分开第一高端阀组第二旁通开关12、第一高端阀组阀组开关14和第一高端阀组母线开关13。
如果第一高端阀组第二旁通开关12的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组母线开关13，再分开第一高端阀组第二旁通开关12，后分开第一高端阀组阀组开关14。
如果第一高端阀组第二旁通开关12的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组阀组开关14，再分开第一高端阀组第二旁通开关12，后分开第一高端阀组母线开关13。
如果第一高端阀组阀组开关14的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组母线开关13，再分开第一高端阀组阀组开关14，后分开第一高端阀组第二旁通开关12。
如果第一高端阀组阀组开关14的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组第二旁通开关12，再分开第一高端阀组阀组开关14，后分开第一高端阀组母线开关13。
如果第一高端阀组母线开关13的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组第二旁通开关12，再分开第一高端阀组母线开关13，后分开第一高端阀组阀组开关14。
如果第一高端阀组母线开关13的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组阀组开关14，再分开第一高端阀组母线开关13，后分开第一高端阀组第二旁通开关12。
在S140中，隔离完成后，高端换流器所在直流极的低端换流器恢复正常运行。
低端换流器恢复正常运行为低端换流器按照正常直流电压和正常直流电流运行，控制直流极的极母线电压为正常直流电压。
为了防止其他保护动作，此种情况下，高端换流器检测到高端换流器的阀区发生接地故障时，增大所述高端换流器的极差保护差动电流定值或者增大所述高端换流器的极差保护延时定值或者屏蔽极差保护、屏蔽阀组连接线差动保护、直流低电压保护，高端换流器隔离后，再开放极差保护、阀组连接线差动保护、直流低电压保护。
本实施例提供的技术方案，当特高压直流输电系统双直流极运行时，换流器检测到换 流器阀区接地故障时，不闭锁整个直流极，而只是闭锁故障的换流器，通过双直流极平衡控制，将正常运行极的电流导入到故障极的极母线上，从而避免正常运行极的电流过多地流入到故障点，从而保证更多换流器运行，避免损失较大直流输送功率。
图3是本申请实施例提供的另一种特高压直流高端换流器阀区接地故障控制方法流程示意图。
特高压直流输电系统包括至少一个整流站与至少一个逆变站。整流站与逆变站包括单直流极或双直流极。直流极包括串联连接的至少两个换流器，高端换流器为靠近极母线的换流器。以下为技术术语定义。
全阀组运行：高端换流器所在直流极除高端换流器之外还至少有一个换流器在运行。
高端换流器的阀区发生接地故障：包括高端换流器发生接地故障、高端换流器与换流变压器之间连接线发生接地故障、换流变压器阀侧绕组发生接地故障的至少一种。
检测到高端换流器的阀区发生接地故障：检测到高端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
高端换流器的阀区发生接地故障通过换流器差动保护动作来判断，换流器差动保护动作判据公式如下。
IDiff_v＝|IDC1P–IDC1N|，
IRes_v＝|IDC1P+IDC1N|/2，
IDiff_v>max(Iv_set,k_set*IRes_v)；
其中，IDC1P为高端换流器直流侧的高压母线电流，IDC1N为高端换流器直流侧的低压母线电流，Iv_set为起动电流定值，k_set为比率系数。
当特高压直流输电系统的高端换流器所在直流极为全阀组运行，即一直流极的高端换流器和低端换流器同时运行，检测到高端换流器的阀区发生接地故障时，控制方法如下。
在S210中,控制高端换流器闭锁。
如果高端换流器为电压源换流器，控制高端换流器闭锁为立即停发触发脉冲，跳开换流变压器进线开关，换流变压器进线开关跳开后，闭合第二旁通开关。
以整流站100的第一直流极I110的第一高端换流器1为例，如果第一高端换流器1为电压源换流器，控制第一高端换流器1闭锁为立即停发触发脉冲，闭合第一高端阀组第二旁通开关12，跳开第一高端换流器1的第一高端换流变压器进线开关131，第一高端阀组第二旁通开关12连接第一高端换流器1的正极和负极。
如果高端换流器为电网换相换流器，控制高端换流器闭锁根据运行于整流或逆变状态选择不同的闭锁方式，当高端换流器整流运行时，选择以下两种闭锁方式的任一种：整流侧换流器第一种闭锁方式和整流侧换流器第二种闭锁方式。当高端换流器逆变运行时，选择以下两种闭锁方式 的任一种：逆变侧换流器第一种闭锁方式和逆变侧换流器第二种闭锁方式。
以整流站100为例，如果第一直流极I110的第一高端换流器1整流运行，如果采用整流侧换流器第一种闭锁方式：整流站100第一直流极I110的第一高端换流器1立即停发触发脉冲，逆变站200第三直流极I210的第三高端换流器5控制触发角为90度；整流站100第一直流极I110的第一高端换流器1跳开第一高端换流变压器进线开关131，闭合第一高端阀组第二旁通开关12，逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第三高端阀组第二旁通开关52。
以整流站100为例，如果第一直流极I110的第一高端换流器1整流运行，如果采用整流侧换流器第二种闭锁方式：整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12，同时跳开第一高端换流变压器进线开关131，逆变站200第三直流极I210的第三高端换流器5控制触发角为90度；逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第三高端阀组第二旁通开关52。
以逆变站200为例，如果第三直流极I210的第三高端换流器5逆变运行，如果采用逆变侧换流器第一种闭锁方式：逆变站200第三直流极I210的第三高端换流器5跳开第三高端换流变压器进线开关231，第三高端换流变压器进线开关231跳开后投入旁通对，闭合第三高端阀组第二旁通开关52，整流站100第一直流极I110的第一高端换流器1控制触发角为90度；整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12。
以逆变站200为例，如果第三直流极I210的第三高端换流器5逆变运行，如果采用逆变侧换流器第二种闭锁方式：逆变站200第三直流极I210的第三高端换流器5投入旁通对，闭合第三高端阀组第二旁通开关52，同时跳开第三高端换流变压器进线开关231，整流站100第一直流极I110的第三高端换流器5控制触发角为90度；整流站100第一直流极I110的第一高端换流器1投入旁通对，闭合第一高端阀组第二旁通开关12。
在S220中,控制流过故障点的电流最小。
具体而言，控制高端换流器所在站直流极的整流侧的换流器移相，即控制触发角为164度。控制其他站直流极的相应的低端换流器运行在最大触发角控制或移相。
当整流站100第一直流极I110的第一高端换流器1检测到第一高端换流器1的阀区发生接地故障时，控制第一高端换流器1闭锁，同时逆变站200第三直流极I210的第三高端换流器5退出运行，控制整流站100第一直流极I110的第一低端换流器2移相，即控制触发角为164度。逆变站200第三直流极I210的第三低端换流器6运行在最大触发角控制。
当逆变站200第三直流极I210的第三高端换流器5检测到第三高端换流器5的阀区发生接地故障时，控制第三高端换流器5闭锁，同时整流站100第一直流极I110的第一高端换流器1退出运行，控制整流站100第一直流极I110的第一低端换流器2移相，即控制触发角为164度，逆变站200第三直流极I210的第三低端换流器6运行在最大触发角控制。
在S230中，隔离高端换流器。
以整流站100第一直流极I110的第一高端换流器1为例，通过以下控制隔离故障第一高端换流器1：闭合第一高端阀组第一旁通开关11，分开第一高端阀组第二旁通开关12、第一 高端阀组阀组开关14和第一高端阀组母线开关13。
如果第一高端阀组第二旁通开关12的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组母线开关13，再分开第一高端阀组第二旁通开关12，后分开第一高端阀组阀组开关14。
如果第一高端阀组第二旁通开关12的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组阀组开关14，再分开第一高端阀组第二旁通开关12，后分开第一高端阀组母线开关13。
如果第一高端阀组阀组开关14的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组母线开关13，再分开第一高端阀组阀组开关14，后分开第一高端阀组第二旁通开关12。
如果第一高端阀组阀组开关14的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组第二旁通开关12，再分开第一高端阀组阀组开关14，后分开第一高端阀组母线开关13。
如果第一高端阀组母线开关13的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P大于低压母线电流IDC1N，先分开第一高端阀组第二旁通开关12，再分开第一高端阀组母线开关13，后分开第一高端阀组阀组开关14。
如果第一高端阀组母线开关13的分断电流定值最大，且第一高端换流器1直流侧的高压母线电流IDC1P小于低压母线电流IDC1N，先分开第一高端阀组阀组开关14，再分开第一高端阀组母线开关13，后分开第一高端阀组第二旁通开关12。
在S240中，隔离完成后，整流侧的换流器解除移相后恢复正常运行。
以整流站100第一直流极I110的第一高端换流器1为例，整流站100(整流侧)第一直流极I110的第一低端换流器2恢复正常运行为第一低端换流器2按照正常直流电压和正常直流电流运行，控制第一直流极I110的极中性母线电流为正常直流电流。控制方法为第一低端换流器2采用电流控制来控制极中性母线电流为正常直流电流，第三低端换流器5采用电压控制来控制极母线电压为正常电压。
为了防止其他保护动作，此种情况下，高端换流器检测到高端换流器的阀区发生接地故障时，增大高端换流器所在直流极的极差保护差动电流定值或者增大高端换流器所在直流极的极差保护延时定值或者屏蔽极差保护、阀组连接线差动保护、直流低电压保护，高端换流器隔离后，再开放极差保护、阀组连接线差动保护、直流低电压保护。
极差保护差动电流为极中性母线电流、直流滤波器电流、极中性母线冲击电容器电流和极中性母线避雷器电流之和与极母线电流之差。阀组连接线差动电流为高端换流器直流侧的低压母线电流与低端换流器直流侧的高压母线电流之差。直流低电压是通过判断极母线电压低来实现的。
上述同时控制整流侧的换流器移相后，在隔离高端换流器前，可选地，经过一定的去游离时间后，控制低端换流器重启一次，如果低端换流器重启成功，则低端换流器恢复正常运行，如果 低端换流器重启失败，则低端换流器继续保持移相。
本实施例提供的技术方案，当特高压直流输电系统双直流极运行时，换流器检测到换流器阀区接地故障时，不闭锁整个直流极，而只是闭锁故障的换流器，通过将整流侧的换流器移相，阻断电流流入到故障点，从而保证更多换流器运行，避免损失较大直流输送功率。
图4是本申请实施例提供的一种特高压直流高端换流器阀区接地故障控制装置的结构示意图。控制装置300用于控制特高压直流输电系统，包括检测单元310和控制单元320。
检测单元310检测高端换流器的高压母线电流IDC1P和低压母线电流IDC1N，检测双直流极的极中性母线电流IDNC，检测低端换流器的高压母线电流IDC2P、低压母线电流IDC2N和极母线电流IDL，检测极母线电压UDL和极中性母线电压UDN。
控制单元320判断特高压直流输电系统的高端换流器所在直流极为全阀组运行并检测到所述高端换流器的阀区发生接地故障时，选择以下两种控制策略中的任一种。
方法一：控制该高端换流器闭锁；控制高端换流器所在直流极的极母线电压为零或低端换流器直流电流与除高端换流器所在站之外的其他站相应极的直流电流相等，上述低端换流器为靠近极中性母线的换流器；隔离高端换流器；控制低端换流器恢复运行。
方法二：控制该高端换流器闭锁；控制高端换流器所在直流极的整流侧的运行的换流器移相；隔离高端换流器；控制整流侧的换流器解除移相后恢复正常运行。
以上对本申请实施例进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明仅用于帮助理解本申请的方法及其核心思想。同时，本领域技术人员依据本申请的思想，基于本申请的具体实施方式及应用范围上做出的改变或变形之处，都属于本申请保护的范围。综上所述，本说明书内容不应理解为对本申请的限制。

Claims (25)

  1. 一种特高压直流高端换流器阀区接地故障控制方法，应用于特高压直流输电系统的直流极的高端换流器，所述特高压直流输电系统包括至少一个整流站与至少一个逆变站，所述整流站与所述逆变站包括单直流极或双直流极，所述直流极包括串联连接的至少两个换流器，所述高端换流器为靠近极母线的换流器，当所述高端换流器所在直流极为全阀组运行，并检测到所述高端换流器的阀区发生接地故障时，所述控制方法包括：
    控制所述高端换流器闭锁；
    控制流过故障点的电流最小；
    隔离所述高端换流器；
    控制所述特高压直流输电系统恢复正常运行。
  2. 如权利要求1所述的控制方法，其中，所述高端换流器或所述低端换流器包括电网换相换流器或电压源换流器中的至少一种。
  3. 如权利要求1所述的控制方法，其中，
    所述双直流极运行包括：每个所述直流极有至少一个换流器在运行；
    所述全阀组运行包括：所述高端换流器所在直流极除所述高端换流器之外还至少有一个换流器在运行。
  4. 如权利要求1所述的控制方法，其中，所述高端换流器的阀区发生接地故障，包括：
    所述高端换流器发生接地故障、所述高端换流器与换流变压器之间连接线发生接地故障、所述换流变压器阀侧绕组发生接地故障的至少一种。
  5. 如权利要求1所述的控制方法，其中，所述检测到所述高端换流器的阀区发生接地故障，包括：
    检测到所述高端换流器直流侧的高压母线电流和低压母线电流之差的绝对值大于设定的电流差值。
  6. 如权利要求1所述的控制方法，其中，如果所述高端换流器为电压源换流器，所述控制高端换流器闭锁包括：
    控制所述高端换流器停发触发脉冲，闭合所述高端换流器所在高端阀组的第二旁通开关，跳开所述高端换流器的换流变压器进线开关，所述第二旁通开关连接所述高端换流器的正极和负极。
  7. 如权利要求1所述的控制方法，其中，如果所述高端换流器为电网换相换流器，所述控制所述高端换流器闭锁包括：
    当所述高端换流器整流运行时，选择整流侧换流器第一种闭锁方式或整流侧换流器第二种闭锁方式；
    当所述高端换流器逆变运行时，选择逆变侧换流器第一种闭锁方式和逆变侧换流器第二种闭锁方式。
  8. 如权利要求7所述的控制方法，其中，所述整流侧换流器第一种闭锁方式包括：
    控制整流运行的所述高端换流器停发触发脉冲，相应的逆变运行的换流器控制触发角为90度；
    控制跳开所述高端换流器的换流变压器进线开关，闭合所述高端换流器所在高端阀组的第二旁通开关，相应的逆变运行的换流器投入旁通对，闭合旁通开关，所述第二旁通开关连接所述高端换流器的阳极和阴极。
  9. 如权利要求7所述的控制方法，其中，所述整流侧换流器第二种闭锁方式包括：
    控制所述高端换流器投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，同时跳开所述高端换流器的换流变压器进线开关，相应的逆变运行的换流器控制触发角为90度，所述第二旁通开关连接所述高端换流器的阳极和阴极；
    控制所述相应的逆变运行的换流器投入旁通对，闭合旁通开关。
  10. 如权利要求7所述的控制方法，其中，所述逆变侧换流器第一种闭锁方式包括：
    控制跳开逆变运行的所述高端换流器的换流变压器进线开关，投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述高端换流器的阳极和阴极；
    控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
  11. 如权利要求7所述的控制方法，其中，所述逆变侧换流器第二种闭锁方式包括：
    控制逆变运行的所述高端换流器投入旁通对，闭合所述高端换流器所在高端阀组的第二旁通开关，同时跳开所述高端换流器连接的换流变压器进线开关，相应的整流运行的换流器控制触发角为90度，所述第二旁通开关连接所述低端换流器的阳极和阴极；
    控制所述相应的整流运行的换流器投入旁通对，闭合旁通开关。
  12. 如权利要求1所述的控制方法，其中，所述控制流过故障点的电流最小，包括：
    控制所述高端换流器所在直流极的极母线电压为零或控制所述高端换流器所在直流极的低端换流器直流电流与除所述高端换流器所在站之外的其他站相应极的直流电流相等，或者控制所述高端换流器所在直流极的整流侧的运行的换流器移相，所述低端换流器为靠近极中性母线的换流器。
  13. 如权利要求12所述的控制方法，其中，如果故障发生在整流侧，所述控制所述高端换流器所在直流极的极母线电压为零，包括：
    所述低端换流器采用电流控制来控制直流电流，逆变侧相应的换流器采用电压控制来控制整流侧的极母线电压为零；或者
    所述低端换流器采用电压控制来控制整流侧的极母线电压为零，并将故障信息发送到逆变侧，逆变侧相应的换流器采用电流控制来控制直流电流。
  14. 如权利要求12所述的控制方法，其中，如果故障发生在逆变侧，所述控制所述高端换流器所在直流极的极母线电压为零，包括：
    所述低端换流器采用电压控制来控制逆变侧的极母线电压为零，并将故障信息发送到整流侧，整流侧相应的换流器采用电流控制来控制直流电流；或者
    所述低端换流器采用电流控制来控制直流电流，整流侧相应的换流器采用电压控制来控制逆变侧的极母线电压为零。
  15. 如权利要求12所述的控制方法，其中，所述控制所述高端换流器所在直流极的低端换流器直流电流与除所述高端换流器所在站之外的其他站相应极的直流电流相等，包括：
    所述低端换流器采用电流控制来控制直流电流，所述其他站相应极采用电流控制来控制直流电流，所述低端换流器与所述其他站相应极采用相同的直流电流参考值；
    所述低端换流器的直流电流为所述低端换流器直流侧的高压母线电流、低压母线电流的至少一种，如果所述其他站只有一个，所述其他站相应极的直流电流为所述其他站相应极的极母线电流、换流器直流侧的高压母线电流、低压母线电流的至少一种，如果所述其他站有两个及以上，所述其他站相应极的直流电流为所述其他站相应极的极母线电流之和、换流器直流侧的高压母线电流之和、低压母线电流之和的至少一种。
  16. 如权利要求13至15之任一项所述的控制方法，其中，所述采用电流控制的换流器的直流电流参考值根据特高压直流输电系统的有功功率、无功功率或入地电流限制需求确定。
  17. 如权利要求1所述的控制方法，其中，所述隔离所述高端换流器包括：
    闭合所述高端换流器所在高端阀组的第一旁通开关，分开所述高端阀组的第二旁通开关、阀组开关和母线开关，所述第一旁通开关与所述高端换流器并联连接，所述第二旁通开关连接所述高端换流器的两端，所述阀组开关连接所述高端换流器与阀组连接线，所述母线开关连接所述高端换流器与极母线。
  18. 如权利要求17所述的控制方法，其中，如果所述第二旁通开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：
    如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述母线开关， 再分开所述第二旁通开关，后分开所述阀组开关；
    如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先分开所述阀组开关，再分开所述第二旁通开关，后分开所述母线开关。
  19. 如权利要求17所述的控制方法，其中，如果所述阀组开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：
    如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述母线开关，再分开所述阀组开关，后分开所述第二旁通开关；
    如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先分开所述第二旁通开关，再分开所述阀组开关，后分开所述母线开关。
  20. 如权利要求17所述的控制方法，其中，如果所述母线开关的分断电流定值最大，所述分开所述高端换流器所在高端阀组的第二旁通开关、阀组开关和母线开关，包括：
    如果所述高端换流器直流侧的高压母线电流大于低压母线电流，先分开所述第二旁通开关，再分开所述母线开关，后分开所述阀组开关；
    如果所述高端换流器直流侧的高压母线电流小于低压母线电流，先分开所述阀组开关，再分开所述母线开关，后分开所述第二旁通开关。
  21. 如权利要求12所述的控制方法，其中，所述控制所述特高压直流输电系统恢复正常运行，包括：
    控制所述低端换流器恢复运行，或者控制所述整流侧的换流器解除移相后恢复正常运行。
  22. 如权利要求21所述的控制方法，其中，
    所述控制所述低端换流器恢复正常运行，包括：所述低端换流器与所述其他站相应极的换流器中，一个换流器采用电压控制或最大触发角控制，其他换流器采用电流控制，控制所述低端换流器按照正常直流电压和正常直流电流运行；
    所述控制所述整流侧的换流器解除移相后恢复正常运行，包括：所述整流侧的换流器解除移相后，所述低端换流器与所述其他站相应极的换流器中，一个换流器采用电压控制或最大触发角控制，其他换流器采用电流控制，控制所述低端换流器按照正常直流电压和正常直流电流运行。
  23. 如权利要求1所述的控制方法，其中，所述隔离所述高端换流器之前，还包括：
    增大所述高端换流器所在直流极的极差保护差动电流定值或者增大所述高端换流器所在直流极的极差保护延时定值或者屏蔽极差保护，直至所述高端换流器隔离。
  24. 如权利要求1所述的控制方法，其中，所述控制流过故障点的电流最小之后，还包括：
    经过一定的去游离时间后，控制所述整流侧的换流器重启一次；
    如果重启成功，则所述整流侧的换流器恢复正常运行；
    如果重启失败，则所述整流侧的换流器继续控制流过故障点的电流最小。
  25. 一种特高压直流高端换流器阀区接地故障控制装置，应用如权利要求1至24之任一项所述特高压直流高端换流器阀区接地故障控制方法，所述控制装置包括：
    检测单元，检测所述高端换流器的高压母线电流和低压母线电流，检测双直流极的极中性母线电流，检测所述低端换流器的高压母线电流、低压母线电流和极母线电流，检测极母线电压和极中性母线电压；
    控制单元，判断所述特高压直流输电系统的所述高端换流器所在直流极为全阀组运行，并检测到所述高端换流器的阀区发生接地故障时，控制所述高端换流器闭锁；控制流过故障点的电流最小；隔离所述高端换流器；控制所述特高压直流输电系统恢复正常运行。
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