WO2021129822A1 - 高压直流输电系统直流侧接地故障控制方法及控制装置 - Google Patents

高压直流输电系统直流侧接地故障控制方法及控制装置 Download PDF

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Publication number
WO2021129822A1
WO2021129822A1 PCT/CN2020/139539 CN2020139539W WO2021129822A1 WO 2021129822 A1 WO2021129822 A1 WO 2021129822A1 CN 2020139539 W CN2020139539 W CN 2020139539W WO 2021129822 A1 WO2021129822 A1 WO 2021129822A1
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Prior art keywords
converter
pole
ground fault
converters
voltage
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PCT/CN2020/139539
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English (en)
French (fr)
Inventor
卢东斌
李海英
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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 BR112022010444-8A priority Critical patent/BR112022010444B1/pt
Publication of WO2021129822A1 publication Critical patent/WO2021129822A1/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
    • H02H7/265—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 making use of travelling wave theory
    • 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
    • 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 and a control device for ground fault control on the direct-current side of a high-voltage direct current transmission system.
  • HVDC transmission systems are divided into conventional HVDC transmission systems, flexible HVDC transmission systems, conventional UHV DC transmission systems, hierarchical access UHV DC transmission systems, and hybrid UHV DC transmission systems.
  • the conventional HVDC transmission system has only one grid commutating converter per DC pole.
  • a flexible DC transmission system has only one voltage source converter for each DC pole.
  • the high-end and low-end converters of a DC pole are all grid-commutated converters, and they are connected to the same AC grid.
  • the high-end and low-end converters connected to one DC pole of the UHV DC transmission system in layers are all grid-commutated converters, and they are respectively connected to two different AC power grids.
  • Hybrid UHV DC transmission systems are divided into inter-station mixing, inter-electrode mixing and intra-electrode mixing. Hybrid UHV DC transmission system between stations.
  • the high-end and low-end converters of one converter station are all grid-converted converters, and the high-end and low-end converters of the other converter station are all voltage source converters.
  • Device In the hybrid UHV DC transmission system with inter-pole hybrid, the high-end and low-end converters of one DC pole are all grid-commutated converters, and the high-end and low-end converters of the other DC pole are all voltage source converters.
  • the high-end and low-end converters of a DC pole are respectively the grid commutated converter and the voltage source converter.
  • the prior art isolates the fault by blocking the entire DC pole.
  • a ground fault occurs on the DC side of the valve area of the HVDC system
  • the prior art isolates the fault by blocking the entire DC pole.
  • bipolar operation after the entire DC pole is blocked, compared with the converter that only blocks the fault area, a larger current flows through the grounding pole line. If the transmission power is large, more DC power will be lost, and the entire DC pole will be blocked. , Before the neutral bus switch is opened, more fault current will flow through the fault point.
  • the embodiment of the application provides a method for controlling a ground fault on the DC side of a high-voltage direct current transmission system.
  • the high-voltage direct current 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.
  • the DC poles include at least one converter
  • the control method includes: controlling at least one converter at both ends of the ground fault to continue to operate;
  • the requirements of the high-voltage direct current transmission system determine the DC current reference values of the two converters at both ends of the ground fault, and the two converters include one continuous converter at each end of the ground fault;
  • the DC current reference value controls the DC currents of the two converters to be equal; if the area where the ground fault occurs is in the rectifier station or the inverter station, the high-voltage DC transmission system is controlled to isolate the ground After a fault, control the normal operation of the two converters, or control the two converters or the DC poles where the two converters are located, and control the high-voltage direct current transmission system to isolate the ground fault; if all The area where the ground fault occurs is in the DC line or the ground electrode line, and after a certain de-ionization time or the disappearance of the ground fault is detected, the two converters are controlled to operate normally.
  • the converter includes at least one of a grid-commutated converter or a voltage source converter.
  • the method further includes: according to the requirements of the AC system, controlling the high-voltage DC power transmission system to cut off or put into the AC filter connected to the AC system Device.
  • the method further includes: controlling the reactive power or AC voltage output by the voltage source converter according to the requirements of the AC system.
  • the weak AC system is an AC system in which the short-circuit current ratio of the AC system is less than 3, and the short-circuit current ratio is the ratio of the short-circuit capacity of the AC system to the rated power of the HVDC transmission system;
  • the requirements of the system include reactive power requirements and AC voltage limits.
  • the DC side ground fault includes: at least one of a valve area DC side ground fault, a pole area ground fault, a bipolar area ground fault, a DC line area ground fault, and a ground electrode line area ground fault;
  • the ground fault on the DC side of the valve area includes at least one of the grounding of the high-voltage bus on the DC side of the converter and the grounding of the low-voltage bus on the DC side of the converter;
  • the bipolar area ground fault includes: a bipolar neutral bus ground fault;
  • the DC line area ground fault includes: a DC line ground fault;
  • the ground electrode line area ground fault includes: a ground electrode Line ground fault.
  • the DC side ground fault is determined by detecting protection actions, and the protection includes: converter differential protection, extreme differential protection, extreme bus differential protection, extreme neutral bus differential protection, dual At least one of extremely neutral bus differential protection, valve group connection line differential protection, line longitudinal differential protection, line mutation protection, and line traveling wave protection.
  • the requirements of the high-voltage direct current transmission system include at least one of: active power demand, reactive power demand, ground current limit value demand, and current limit value demand of the DC pole where the fault is located.
  • the HVDC power transmission system has more than one demand, different demands are given priority at the same time.
  • the determining the DC current reference value of the two converters based on the demand of the high-voltage direct current transmission system includes: if the demand of the high-voltage direct current transmission system is an active power demand, converting the active power The power demand is divided by the sum of the absolute values of the DC voltages of all the converters operating in the rectifier station or the inverter station to obtain the DC current reference values of the two converters.
  • the DC current reference value of the two converters is determined based on the demand of the high-voltage direct current transmission system , Including: if the demand of the high-voltage direct current transmission system is a reactive power demand, determining the two converters based on the reactive power demand, no-load DC bus voltage, firing or shut-off angle, and commutation angle.
  • the calculation method of the DC current reference value of the rectifier side converter is as follows.
  • the calculation method of the inverter on the inverter side is as follows.
  • I ord is the reference value of DC current
  • Q conv is the reactive power demand of the six-pulse or twelve-pulse power grid commutated converter
  • U di0 is the power demand of the six-pulse or twelve-pulse grid commutated converter No-load DC bus voltage
  • ⁇ is the trigger angle of the converter
  • ⁇ is the commutation angle of the converter
  • ⁇ is the turn-off angle of the converter
  • the converter is a six-pulse power grid commutation converter
  • the determining the DC current reference value of the two converters based on the requirement of the HVDC system includes: if the requirement of the HVDC system is the earth current limit value requirement, so The DC current reference value of each converter of the two converters is greater than the difference between the DC current of the other DC pole in the same station and the ground current limit value, and is less than the DC current and the DC current of the other DC pole in the same station. The sum of the current limit values into the ground.
  • the determining the DC current reference value of the two converters based on the demand of the HVDC power transmission system includes: if the demand of the HVDC power transmission system is the current limit value of the DC pole where the fault is located It is required to determine that the DC current reference value of the two converters is less than the current limit value of the DC pole where the fault is located.
  • the DC current of the converter includes: at least one of the high-voltage bus current, the low-voltage bus current of the converter, the pole bus current of the DC pole where the converter is located, or the pole neutral bus current.
  • the controlling the DC currents of the two converters to be equal based on the DC current reference value includes: the ground fault occurs at the pole bus of the rectifier station and the pole of the inverter station. In the area between the busbars, the DC currents of the two converters located at the two stations at the two ends of the ground fault are controlled to be equal and the DC current reference value; the ground fault occurs at a DC pole In the area between the polar neutral bus and the polar neutral bus of the other DC pole in the same station, the DC currents of the two converters located at the two DC poles of the same station at the two ends of the ground fault are controlled to be equal And is the reference value of the direct current; when the ground fault occurs in the area between the converters of one direct current pole, the two converters at both ends of the ground fault are respectively located on the same direct current pole. The direct current is equal and is the reference value of the direct current.
  • the area between the pole bus of the rectification station and the pole bus of the inverter station includes the pole bus of the rectification station, and the DC side high voltage bus of the converter connected to the pole bus. At least one of the pole bus of the inverter station, the DC side high voltage bus of the inverter connected to the pole bus, and the DC line; the neutral bus of the one DC pole and the other of the same station.
  • the area between the polar neutral buses of the current poles includes a polar neutral bus with a DC pole, a low-voltage bus on the DC side of the converter connected with a DC pole to the polar neutral bus, and a polar neutral bus with another DC pole in the same station.
  • the controlling the DC currents of the two converters located at two stations at both ends of the ground fault to be equal and the reference value of the DC current includes: the two converters at both ends of the ground fault are located at two The two converters of the station both adopt current control, and the control target is the same as the direct current reference value.
  • the controlling the DC currents of the two converters located at two DC poles of the same station at both ends of the ground fault to be equal and the DC current reference value includes: the ground fault
  • the two converters located at the two DC poles of the same station at both ends adopt current control and the control target is the same as the DC current reference value; or the two DC converters at both ends of the ground fault are located at the same station, respectively.
  • the two converters of the two poles adopt maximum firing angle control or DC voltage control, and the DC pole of the other station and the converter of the other DC pole of the other station both adopt current control and the control target is the same as the DC current. Reference.
  • the controlling the DC currents of the two converters located at the same DC pole at both ends of the ground fault to be equal and the DC current reference value includes: The two converters located on the same DC pole both adopt current control and the control target is the same as the DC current reference value.
  • the normal operation of the inverter includes: the inverter operates according to a normal direct current and a normal direct current voltage; the normal direct current is between 0.05 and 1.6 times the rated direct current, and the normal direct current The voltage is between 0.3 and 1.3 times the rated DC voltage.
  • the converter blocking includes: controlling the grid commutating converter to stop triggering pulses; or/and controlling the grid commutating Put the inverter into the bypass pair.
  • the converter blocking includes: controlling the voltage source converter to stop a trigger pulse.
  • the detecting that the ground fault disappears includes: detecting the absolute value of the pole bus voltage or the DC line voltage; if the absolute value of the pole bus voltage or the DC line voltage is greater than a first DC voltage threshold, determining When the ground fault disappears, the first DC voltage threshold is between 0.05 and 1.1 times the rated DC voltage.
  • An embodiment of the present application also provides a ground fault control device on the DC side of a high-voltage direct current transmission system, including a detection unit and a control unit, the detection unit is used to detect the parameters of the high-voltage direct current transmission system; the control unit is based on the high voltage
  • the parameters of the DC transmission system determine that a ground fault occurs on the DC side of the HVDC transmission system, at least one converter at each end of the ground fault is controlled to continue to operate; based on the requirements of the HVDC transmission system, the two ends of the ground fault are determined DC current reference values of two converters, the two converters including one converter that continues to operate at both ends of the ground fault; controlling the two converters based on the DC current reference value
  • the direct currents are equal; if the area where the ground fault occurs is in the rectifier station or the inverter station, control the high-voltage direct current transmission system to control the normal operation of the two converters after isolating the ground fault, or control After the two converters are blocked or the DC poles
  • Fig. 1 is a schematic diagram of a main circuit of a high-voltage direct current 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 on the DC side of a high-voltage direct current transmission system according to an embodiment of the present application.
  • FIG. 3 is a schematic flowchart of another method for controlling ground faults on the DC side of a HVDC power transmission system according to an embodiment of the present application.
  • Fig. 4A is a graph of simulation test results when a ground fault occurs in the busbar on the rectifier side of the prior art.
  • FIG. 4B is a diagram of simulation test results when the rectifier side pole bus bar is grounded and provided by the embodiment of the present application.
  • FIG. 5 is a schematic flowchart of another method for controlling ground faults on the DC side of a HVDC power transmission system according to an embodiment of the present application.
  • FIG. 6 is a schematic flowchart of another method for controlling ground faults on the DC side of a HVDC power transmission system according to an embodiment of the present application.
  • Fig. 7 is a schematic structural diagram of a ground fault control device on the DC side of a high voltage direct current transmission system according to an embodiment of the present application.
  • Fig. 1 is a schematic diagram of a main circuit of a high-voltage direct current transmission system provided by an embodiment of the present application.
  • the main circuit of the HVDC transmission system includes the rectifier station 100, the inverter station 200, the first DC line 150, the second DC line 160, the rectifier station ground electrode line 114, the rectifier station ground electrode 115 and the inverter station ground electrode line 214, Ground pole 215 of the inverter station.
  • the rectifier station 100 includes a first DC pole I110, a 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 pole neutral bus switch 119, The first DC filter 93 and the first smoothing 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 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.
  • 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 pulsating bridge circuit includes, but is not limited to, a semi-controlled power semiconductor device that cannot be turned off, generally a thyristor device.
  • 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 a combined converter CSL and a stacked two-level converter CTL.
  • the converter includes, but is not limited to, a fully controllable power semiconductor device that can be turned off.
  • Modular multilevel converter MMC includes, but is not limited to, modular multilevel converter MMC with a half-bridge sub-module structure, modular multi-level converter MMC with a full-bridge sub-module structure, half-bridge and full-bridge At least one of the modular multi-level converter MMC with a hybrid sub-module structure.
  • the second DC pole II120 includes a second low-end valve group 121, a second high-end valve group 122, a second low-end converter transformer 126, a second high-end converter transformer 127, a second DC pole neutral bus switch 129, and a second A DC filter 94 and a second smoothing reactor 92.
  • the second low-end valve group 121 and the second high-end valve group 122 are connected in series.
  • the second low-end valve group 121 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 second high-end valve group 122 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 second low-end converter 3 and the second high-end converter 4 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 pole neutral bus switch 219, and a third A 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 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 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 low-end valve group 221, a fourth high-end valve group 222, a fourth low-end converter transformer 226, a fourth high-end converter transformer 227, a fourth DC pole neutral bus switch 229, and a second A DC filter 98 and a second smoothing reactor 96.
  • the fourth low-end valve group 221 and the fourth high-end valve group 222 are connected in series.
  • 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 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 fourth low-end converter 7 and the fourth high-end converter 8 include at least one of a grid phase converter or a voltage source converter.
  • the various switches mentioned above include but are not limited to at least one of mechanical switches, knife switches, DC circuit breakers, and thyristor valve groups.
  • both the high-end converters and the low-end converters of the DC poles of the rectifier station 100 and the inverter station 200 are grid-commutated converters, it is a 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 voltage source converters, it is a flexible UHV DC transmission system.
  • the voltage source converter has the ability to adjust the voltage to zero voltage or negative voltage, such as the modular multi-level converter based on the full-bridge sub-module, and the modular multi-level converter based on the hybrid of the half-bridge sub-module and the full-bridge sub-module. Level inverter.
  • 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.
  • the voltage source converter has the ability to adjust the voltage to zero voltage or negative voltage, such as the modular multi-level converter based on the full-bridge sub-module, and the modular multi-level converter based on the hybrid of the half-bridge sub-module and the full-bridge sub-module.
  • Level inverter such as the modular multi-level converter based on the full-bridge sub-module, and the modular multi-level converter based on the hybrid of the half-bridge sub-module and the full-bridge sub-module.
  • 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 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 grid commutated converters.
  • the third low-end converter 6 and the fourth low-end converter 7 are voltage source converters, which are hybrid UHV DC transmission systems that are mixed within the poles. Among them, the voltage source converter may not have the ability to adjust the voltage to zero voltage or negative voltage, such as a modular multilevel converter based on a half-bridge sub-module.
  • 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 IDC2N on the DC side of the low-end converter, Polar bus current IDL, polar neutral bus current IDNC, DC filter head current IZT1, ground electrode current IDEL, polar bus voltage UDL and polar neutral bus voltage UDN.
  • a ground fault on the DC side of the HVDC power transmission system includes, but is not limited to, at least one of the DC side ground fault in the valve area, the pole area ground fault, the bipolar area ground fault, the DC line area ground fault, and the ground pole line area ground fault.
  • the ground fault on the DC side of the valve zone includes but is not limited to at least one of the grounding of the high-voltage bus on the DC side of the converter and the grounding of the low-voltage bus on the DC side of the converter.
  • the pole region grounding fault includes but is not limited to at least one of pole bus grounding, pole midpoint grounding, and pole neutral bus grounding.
  • the bipolar ground fault includes but is not limited to the bipolar neutral bus ground fault.
  • Ground faults in the DC line area include but are not limited to DC line ground faults.
  • Ground faults in the ground electrode line area include but are not limited to ground faults in the ground electrode line.
  • Protection includes, but is not limited to, converter differential protection, extremely differential protection, extremely busbar differential protection, extremely neutral busbar differential protection, bipolar neutral busbar differential protection, valve group connection line differential protection, line longitudinal At least one of differential protection, line mutation protection, and line traveling wave protection.
  • FIG. 2 is a schematic flow chart of a method for controlling ground faults on the DC side of a high-voltage DC transmission system according to an embodiment of the present application, showing the high-voltage bus on the DC side of the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 (The measuring point IDC1P is close to the converter side) The control flow when a ground fault occurs.
  • the converters of the first DC pole I110 of the rectifier station 100 and the third DC pole I210 of the inverter station 200 are both grid-commutated converters or voltage source converters (half-bridge and full-bridge hybrid sub-module structure).
  • the bipolar full valve group Before the ground fault on the DC side, the bipolar full valve group operates.
  • the control flow is as follows.
  • At least one converter at each end of the ground fault is controlled to continue to operate.
  • ground fault is between two DC poles
  • at least one converter at each of the two DC poles at both ends of the ground fault is controlled to continue to operate. If the ground fault is in a DC pole, at least two converters of the DC pole where the ground fault is located will continue to operate.
  • the pole bus grounding fault is judged by the converter differential protection action.
  • the criterion of the converter differential protection action is as follows.
  • IDiff_v
  • IRes_v
  • IDiff_v is the converter differential current
  • 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
  • IRes_v is the braking current of the converter's differential protection
  • Iv_set is the starting current setting value of the converter differential protection
  • kv_set is the ratio coefficient of the converter differential protection.
  • the converter differential protection When the converter differential protection is activated, at least one converter at each of the two DC poles at both ends of the ground fault is controlled to continue to operate.
  • the first high-end converter 1 is controlled to be locked, and the first low-end converter 2 continues to operate;
  • the third high-end converter 5 is controlled to lock, and the third low-end converter 6 continues to operate.
  • the blocking process is controlled as follows: the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 stops immediately Trigger pulse, 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, and the first high-end converter 1 of the first DC pole I110 of the rectifier station 100 jumps to the first high-end converter
  • the current transformer inlet switch 131 closes the first high-end valve group and the second bypass switch 12, the third high-end converter 5 of the third DC pole I210 of the inverter station 200 is put into the bypass pair, and the second bypass switch 52 is closed.
  • the locking process is controlled as follows: control the first high-end converter 1 to immediately stop the trigger pulse and skip the first high-end converter After the first high-end converter transformer inlet switch 131 of the first high-end converter transformer is tripped, the second bypass switch 12 of the first high-end valve group is closed, and the third high-end converter 5 is controlled at the same time. The trigger pulse is immediately stopped, the third high-end converter transformer inlet switch 231 of the third high-end converter 5 is opened, and the second bypass switch 52 of the third high-end valve group is closed.
  • the DC current reference values of the two converters at both ends of the ground fault are determined based on the requirements of the HVDC power transmission system.
  • the requirements of the HVDC transmission system include, but are not limited to, at least one of active power requirements, reactive power requirements, ground current limit value requirements, and current limit value requirements of the DC pole where the fault is located. If the HVDC system requires more than One type, giving priority to different requirements at the same time.
  • I ord_p2 P ord /(U d_p2c1 + U d_p2c2 ),
  • I ord_p1 and I ord_p2 are the DC current reference values of pole I and pole II respectively
  • I del_lim is the limit value of current into the ground
  • P ord is the required value of active power
  • U d_p2c1 is the DC voltage of pole II high-end converter
  • U d_p2c2 is the DC voltage of the extremely II low-end converter.
  • the DC current reference value of the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 and the third low-end converter 6 of the third DC pole I210 of the inverter station 200 is given as I ord_p1 .
  • the DC currents of the two converters at both ends of the ground fault are controlled to be equal based on the DC current reference value.
  • the pole bus current IDL of the first low-side converter 2 of the first DC pole I110 of the control rectifier station 100 is equal to the pole bus current IDL of the third low-side converter 6 of the third DC pole I210 of the inverter station 200, and Is I ord_p1 , and the pole bus current IDL or the pole neutral bus current IDNC of the second high-end converter 4 and the second low-end converter 3 of the second DC pole II120 of the control rectifier station 100 is I ord_p2 .
  • the first high-end valve group 111 of the first DC pole I110 of the control rectifier station 100 closes the first high-end valve group and the first bypass switch 11, separates the first high-end valve group, the second bypass switch 12, and the first high-end valve group valve group.
  • the control method is: the rectifier station 100 first
  • the first low-side converter 2 of the DC pole I110 uses current control to control the DC current
  • the third low-side converter 6 of the third DC pole I210 of the inverter station 200 uses maximum firing angle control or DC voltage control to control DC voltage.
  • FIG. 3 is a schematic flow chart of another method for controlling ground faults on the DC side of a HVDC transmission system according to an embodiment of the present application, showing the pole bus of the first DC pole I110 of the rectifier station 100 (between the measuring points IDC1P and IDL) The control flow when a ground fault occurs on the DC side.
  • the converters of the first DC pole I110 of the rectifier station 100 and the third DC pole I210 of the inverter station 200 are both grid-commutated converters (double twelve-pulse converters). Before the DC side ground fault occurs, the two poles Full valve group operation. When a ground fault occurs on the pole bus (between the measuring point IDC1P and IDL) of the first DC pole I110 of the rectifier station 100 of the HVDC power transmission system, the control flow is as follows.
  • At least one converter at each end of the ground fault is controlled to continue to operate.
  • pole bus differential protection action is used to determine the pole bus ground fault, and the action criterion of the pole bus differential protection is as follows.
  • IDiff_p
  • IRes_p max(IDC1P, IDL, IZT1)
  • IDiff_p
  • IRes_p max(IDC2P, IDL, IZT1)
  • IDiff_p is the pole bus differential current
  • IDC1P is the high voltage bus current on the DC side of the high-end converter
  • IDL is the pole bus current
  • IZT1 is the DC filter head current
  • IRes_p is the braking current of the pole bus differential protection.
  • Ip_set is the starting current setting value of the pole-bus differential protection
  • kp_set is the ratio coefficient of the pole-bus differential protection
  • IDC2P is the high-voltage bus current on the DC side of the low-end converter.
  • At least one converter at each of the two DC poles at both ends of the control ground fault continues to operate.
  • at least one of the first high-end converter 1 and the first low-end converter 2 is controlled to continue to operate, and at least one of the third high-end converter 5 and the third low-end converter 6 continues to operate run.
  • the first high-end converter 1 and the first low-end converter 2, the third high-end converter 5 and the third low-end converter 6 all continue to operate as an example.
  • the DC current reference values of the two converters at both ends of the ground fault are determined based on the requirements of the HVDC power transmission system.
  • the requirements of the HVDC transmission system include, but are not limited to, at least one of active power requirements, reactive power requirements, ground current limit value requirements, and current limit value requirements of the DC pole where the fault is located. If the HVDC system requires more than One type, giving priority to different requirements at the same time. The priority of the above-mentioned different requirements can be given in terms of extremes.
  • the calculation method of the reactive power demand of the converter is as follows.
  • Q ord_p2 0.5 ⁇ I d_p2 ⁇ U di0_p2c1 ⁇ (2 ⁇ 21 +sin2 ⁇ 21 -sin2( ⁇ 21 + ⁇ 21 ))/(cos ⁇ 21 -cos( ⁇ 21 + ⁇ 21 ))+0.5 ⁇ I d_p2 ⁇ U di0_p2c2 ⁇ (2 ⁇ 22 +sin2 ⁇ 22 -sin2( ⁇ 22 + ⁇ 22 ))/(cos ⁇ 22 -cos( ⁇ 22 + ⁇ 22 )),
  • Q ord_p1 Q ord -Q ord_p2 .
  • the reactive power demand of the high-end converter or the low-end converter is 1/2 of the reactive power demand of pole I, specifically as :
  • the DC current reference value is calculated as follows.
  • I ord_p1 is the DC current reference value of pole I and pole II
  • Q ord , Q ord_p1 , and Q ord_p2 are the reactive power demand of bipolar, pole I, and pole II respectively
  • I d_p2 is the DC current of pole II
  • U di0_p1c1 , U di0_p1c2 , U di0_p2c1 , U di0_p2c2 are the six pulses in the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the low-end converter of pole II, respectively
  • the no-load DC voltage of the converter, ⁇ 11 , ⁇ 12 , ⁇ 21 , and ⁇ 22 are respectively the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the high-end converter of pole II.
  • the firing angle of the low-end converter, ⁇ 11 , ⁇ 12 , ⁇ 21 , and ⁇ 22 are respectively the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the high-end inverter of pole II.
  • the DC current reference value of the end converter 6 is I ord_p1 .
  • the HVDC system is controlled to cut off or put in the AC filter connected to the AC system.
  • the AC system is overvoltage, or the HVDC system provides reactive power to the AC system, or the HVDC system is blocked, it will cause the AC system to generate overvoltage, and the HVDC system is controlled to cut off the AC filter. If the AC system is undervoltage, or the AC system provides reactive power to the HVDC transmission system, control the HVDC transmission system to put in an AC filter.
  • the HVDC system when the transmission power of the HVDC system is large, after a ground fault occurs on the pole bus (between the measuring point IDC1P and IDL), the HVDC system will cause overvoltage to be generated in the AC system after the HVDC system is blocked. Before blocking, part or all of the AC filters in the first AC filter group 118 are cut off.
  • step S220 can be returned again to determine the two replacements at both ends of the ground fault based on the demand of the HVDC power transmission system.
  • the DC current reference value of the converter to ensure that the AC system voltage is within a reasonable range.
  • step S220 to step S240 can also be executed in a loop for multiple times, and then executed again.
  • the HVDC transmission system is controlled to isolate the ground fault.
  • the first high-end converter 1 and the first low-end converter 2 that control the first DC pole I110 of the rectifier station 100 are blocked, including controlling the above-mentioned converter to trip off the first high-end converter transformer inlet switch 131 and the first
  • the low-end converter transformer inlet switch 132 turns on the bypass pair and controls the closing of the first high-end valve group second bypass switch 12 and the first low-end valve group second bypass switch 22 to stop sending trigger pulses.
  • the rectifier station 100 opens the first DC pole neutral bus switch 119, and the isolation pole bus is grounded.
  • Fig. 4A is a graph of simulation test results when the busbar on the rectifier side is grounded in the prior art.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral line current
  • IDEL is the ground electrode line current
  • UAC_RMS is the effective value of the AC system voltage
  • BLOCK_IND_V1 is the high-side converter blocking signal
  • BLOCK_IND_V2 is Low-end converter block signal.
  • the rated voltage of the UHV DC transmission system is 800kV
  • the rated power is 8000MW
  • the rated line voltage of the AC system is 775kV
  • the rated phase voltage is 447.5.
  • the two poles operate at rated power.
  • the pole busbar differential protection will act, perform pole blocking, block the entire DC pole, high-end converter and low-end converter are both blocked, BLOCK_IND_V1 Displacement, BLOCK_IND_V2 displacement.
  • the current flowing through the fault point is equal to IDNC-IDL.
  • the peak current flowing through the fault point is 11007A; the electric quantity Q at the fault point: 2.24Ah; the I 2 t at the fault point: 13788.7A 2 h; the peak value of the effective value of the AC system phase voltage: 606.1kV.
  • FIG. 4B is a diagram of simulation test results when the rectifier side pole bus bar is grounded and provided by the embodiment of the present application.
  • UDL is the pole bus voltage
  • IDL is the pole bus current
  • IDNC is the pole neutral current
  • IDEL is the ground electrode line current
  • UAC_RMS is the effective value of the AC system voltage
  • BLOCK_IND_V1 is the high-side converter blocking signal
  • BLOCK_IND_V2 is Low-end converter block signal.
  • the rated voltage of the UHV DC transmission system is 800kV
  • the rated power is 8000MW
  • the rated line voltage of the AC system is 775kV
  • the rated phase voltage is 447.5.
  • the two poles are operated at rated power.
  • the DC currents of the two DC poles at both ends of the ground fault are controlled to be equal, and the HVDC transmission system is controlled to cut off the AC filter connected to the AC system.
  • the high-end converter and the low-end converter are both blocked, BLOCK_IND_V1 is changed, and BLOCK_IND_V2 is changed.
  • the current flowing through the fault point is equal to IDNC-IDL.
  • the peak current flowing through the fault point is 10109A; the electric quantity Q at the fault point: 0.19Ah; the I 2 t at the fault point: 719.7A 2 h; the peak value of the effective value of the AC system phase voltage: 531.7kV.
  • the method based on the present application can reduce the current flowing into the fault point, reduce the current flowing into the ground electrode line, and reduce the overvoltage level of the AC system.
  • FIG. 5 is a schematic flow chart of another method for controlling a ground fault on the DC side of a HVDC power transmission system according to an embodiment of the present application, showing the control flow when a ground fault occurs on the DC side of the DC line 150 of the HVDC power transmission system.
  • the converters of the first DC pole I110 of the rectifier station 100 and the third DC pole I210 of the inverter station 200 are both grid-commutated converters. Before a ground fault occurs on the DC side, the bipolar full valve group operates. When a ground fault occurs in the DC line 150 of the HVDC power transmission system, the control process is as follows.
  • At least one converter at each of the two DC poles at both ends of the ground fault is controlled to continue to operate.
  • the DC line ground fault is judged by the line mutation amount or/and the traveling wave protection action.
  • the action criterion of line mutation protection is as follows.
  • dUDL/dt is the sudden change amount of DC voltage per unit time
  • dUDL_set is the fixed value of sudden change of direct current voltage
  • UDL is the pole bus voltage
  • UDL_set is the fixed value of direct current voltage
  • control at least one converter at each of the two DC poles at both ends of the ground fault to continue operation.
  • the first high-end converter 1 and the first low-end converter 2 are controlled, and the third high-end converter 5 and the third low-end converter 6 continue to operate.
  • the DC current reference values of the two converters at both ends of the ground fault are determined based on the requirements of the HVDC power transmission system.
  • the requirements of the HVDC transmission system include but are not limited to at least one of active power demand, reactive power demand, ground current limit value, and current limit value of the DC pole where the fault is located. If the HVDC transmission system requires more than one type , And give priority to different needs at the same time.
  • the calculation method of the reactive power demand of the converter is as follows.
  • Q ord_p2 0.5 ⁇ I d_p2 ⁇ U di0_p2c1 ⁇ (2 ⁇ 21 +sin2 ⁇ 21 -sin2( ⁇ 21 + ⁇ 21 ))/(cos ⁇ 21 -cos( ⁇ 21 + ⁇ 21 ))+0.5 ⁇ I d_p2 ⁇ U di0_p2c2 ⁇ (2 ⁇ 22 +sin2 ⁇ 22 -sin2( ⁇ 22 + ⁇ 22 ))/(cos ⁇ 22 -cos( ⁇ 22 + ⁇ 22 )),
  • the reactive power demand of the high-end converter or the low-end converter is 1/2 of the reactive power demand of pole I, specifically as
  • the DC current reference value is calculated as follows.
  • I ord_p1 is the DC current reference value of pole I and pole II
  • Q ord , Q ord_p1 , and Q ord_p2 are the reactive power demand of bipolar, pole I, and pole II respectively
  • I d_p2 is the DC current of pole II
  • U di0_p1c1 , U di0_p1c2 , U di0_p2c1 , U di0_p2c2 are the six pulses in the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the low-end converter of pole II, respectively
  • the no-load DC voltage of the converter, ⁇ 11 , ⁇ 12 , ⁇ 21 , and ⁇ 22 are respectively the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the high-end converter of pole II.
  • the firing angle of the low-end converter, ⁇ 11 , ⁇ 12 , ⁇ 21 , and ⁇ 22 are respectively the high-end converter of pole I, the low-end converter of pole I, the high-end converter of pole II, and the high-end inverter of pole II.
  • the DC current reference value of the end converter 6 is I ord_p1 .
  • the DC currents of the two converters at both ends of the ground fault are controlled to be equal based on the DC current reference value.
  • the first high-end converter 1 and the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 are controlled, and the third DC pole of the inverter station 200 is controlled.
  • the third high-end inverter 5 and the third low-end inverter 6 of I210 operate normally.
  • the control method is that the first high-end converter 1 and the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 adopt current control to control the DC current, and the third high end of the third DC pole I210 of the inverter station 200
  • the converter 5 and the third low-end converter 6 adopt maximum firing angle control or DC voltage control to control the DC voltage.
  • the detection of the disappearance of the ground fault includes detecting the absolute value of the pole bus voltage UDL or the DC line voltage. If the absolute value of the pole bus voltage UDL or the DC line voltage is greater than the first DC voltage threshold, it is determined that the ground fault disappears, and the first DC voltage The threshold is between 0.03 and 1.3 times the rated DC voltage.
  • FIG. 6 is a schematic flow chart of another method for controlling ground faults on the DC side of the HVDC power transmission system according to an embodiment of the present application. It shows the valve assembly connection line (measurement point) of the first DC pole I110 of the rectifier station 100 of the HVDC power transmission system. Between IDC1N and IDC2P) the control flow when a ground fault occurs.
  • the converters of the first DC pole I110 of the rectifier station 100 and the third DC pole I210 of the inverter station 200 are both grid-commutated converters.
  • the bipolar full valve group operates before a ground fault occurs on the DC side.
  • the control flow is as follows.
  • At least one converter at each end of the ground fault is controlled to continue to operate.
  • valve group connection line differential protection action to determine the valve group connection line ground fault
  • valve group connection line differential protection action criterion is as follows.
  • IDiff_c
  • IRes_c
  • IDiff_c is the differential current of the valve group connection line
  • IDC1N is the low-voltage bus current on the DC side of the high-end converter
  • IDC2P is the high-voltage bus current on the DC side of the low-end converter
  • IRes_c is the differential protection of the valve group connection line.
  • Dynamic current Ic_set is the starting current setting value of the differential protection of the valve group connection line
  • kc_set is the ratio coefficient of the valve group connection line differential protection.
  • the differential protection of the valve group connection line When the differential protection of the valve group connection line is activated, at least two converters of the DC pole where the control ground fault is located continue to operate.
  • the first high-end converter 1 and the first low-end converter 2 are controlled to continue to operate.
  • the DC current reference values of the two converters at both ends of the ground fault are determined based on the requirements of the HVDC power transmission system.
  • the requirements of the HVDC transmission system include but are not limited to at least one of active power demand, reactive power demand, ground current limit value, and current limit value of the DC pole where the fault is located. If the HVDC transmission system requires more than one type , And give priority to different needs at the same time.
  • I ord_p1 is the DC current reference value of pole I
  • I flt_lim is the current limit value of the DC pole where the fault is located.
  • the DC current reference value of the first high-end converter 1 and the first low-end converter 2 of the first DC pole I110 of the given rectifier station 100 is I ord_p1 .
  • the first high-end converter 1 and the first low-end converter 2 of the first DC pole I110 of the rectifier station 100 can also be controlled to phase shift.
  • the DC currents of the two converters at both ends of the ground fault are controlled to be equal based on the DC current reference value.
  • the low-voltage bus current IDC1N on the DC side of the first high-end converter 1 of the first DC pole I110 of the control rectifier station 100 and the high-voltage bus current IDC2P on the DC side of the first low-end converter 2 are equal and are I ord_p1 .
  • the first high-end converter 1 and the first low-end converter 2 of the first DC pole I110 of the control rectifier station 100 are blocked. Specifically, the above-mentioned converter is controlled to trip off the first high-end converter transformer inlet switch 131 and the first low-end converter transformer inlet switch 132, and the bypass pair is turned on to control the closing of the first high-end valve group and the second bypass.
  • the switch 12 and the second bypass switch 22 of the first low-end valve group stop sending trigger pulses; the third high-end converter 5 and the third low-end converter 6 of the third DC pole I210 of the inverter station 200 control the firing angle If it is 90 degrees, the bypass pair is turned on, the second bypass switch 52 of the third high-end valve group and the second bypass switch 62 of the third low-end valve group are controlled to close, and the trigger pulse is stopped.
  • the rectifier station 100 opens the first DC pole neutral bus switch 119 to isolate the valve group connection line from a ground fault.
  • FIG. 7 is a schematic structural diagram of a ground fault control device 300 on the DC side of a HVDC power transmission system provided by an embodiment of the present application.
  • the device includes a detection unit 310 and a control unit 320.
  • the detection unit 310 is used to detect the parameters of the high-voltage DC transmission system, including 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 IDC2N on the DC side of the low-end converter.
  • the bus current IDL, the extremely neutral bus current IDNC, the DC filter head current IZT1, the ground electrode current IDEL, the extremely bus voltage UDL and the extremely neutral bus voltage UDN are the requirements of the high-voltage DC transmission system.
  • control unit 320 determines that a ground fault occurs on the DC side of the HVDC transmission system based on the DC current of the HVDC transmission system, it controls at least one converter at each end of the ground fault to continue to operate, and determines the ground fault at both ends of the ground fault based on the requirements of the HVDC transmission system.
  • the DC current reference values of the two converters include one continuous converter at each end of the ground fault.
  • the DC currents of the above two converters are controlled to be equal based on the DC current reference value.
  • the HVDC transmission system is controlled to isolate the above ground fault; if the area where the ground fault occurs is in the DC line or the ground electrode line, after a certain de-ionization time or detection of the disappearance of the ground fault, the above two converters are controlled to be normal run.

Abstract

本申请提供高压直流输电系统直流侧接地故障控制方法及控制装置。所述控制方法包括：控制接地故障两端各至少有一个换流器继续运行；基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值，所述两个换流器包括接地故障两端各一个继续运行的换流器；基于直流电流参考值控制所述两个换流器的直流电流相等；如果接地故障发生在整流站或逆变站内，控制高压直流输电系统隔离接地故障后控制所述两个换流器正常运行，或者控制所述两个换流器或所述两个换流器所在直流极闭锁后控制高压直流输电系统隔离接地故障；如果接地故障发生区域在直流线路或接地极线路，经过去游离时间或检测到接地故障消失后，控制所述两个换流器正常运行。

Description

高压直流输电系统直流侧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，具体涉及高压直流输电系统直流侧接地故障控制方法及控制装置。
背景技术
现有的高压直流输电系统分为常规高压直流输电系统、柔性直流输电系统、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。
常规高压直流输电系统一个直流极只有一个电网换相换流器。柔性直流输电系统一个直流极只有一个电压源换流器。常规特高压直流输电系统一个直流极的高、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一个换流站的高、低端换流器都为电网换相换流器，另一个换流站的高、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一个直流极的高、低端换流器都为电网换相换流器，另一个直流极的高、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一个直流极的高、低端换流器分别为电网换相换流器和电压源换流器。
当高压直流输电系统极区发生接地故障时，现有技术通过立即闭锁整个直流极来隔离故障。由于在隔离故障时，需要判断直流电压低延时后才能拉开极中性母线开关，双极运行时在极中性母线开关拉开前，接地故障点仍流过较大的故障电流。
当高压直流输电系统阀区直流侧发生接地故障时，现有技术通过闭锁整个直流极来隔离故障。双极运行时闭锁整个直流极后，与只闭锁故障区域的换流器相比，接地极线流过较大电流，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，在极中性母线开关拉开前，故障点也会流过更多的故障电流。
发明内容
本申请实施例提供一种高压直流输电系统直流侧接地故障控制方法，所述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，所述直流极包括至少一个换流器，当发生所述直流侧接地故障时，所述控制方法包括：控制所述接地故障两端各至少有一个换流器继续运行；基于所述高压直流输电系统的需求确定所述接地故障两端的两个换流器的直流电流参考值，所述两个换流器包括所述接地故障两端各一个继续运行的换流器；基于所述直流电流参考值控制所述两个换流器的直流电流相等；如果所述接地故障发生的区域在所述整流站或所述逆变站内，控制所述高压直流输电系统隔离所述接地故障后控制所述两个换流器正常运行，或者控制所述两个换流器或所述两个换流 器所在直流极闭锁后控制所述高压直流输电系统隔离所述接地故障；如果所述接地故障发生的区域在直流线路或接地极线路，经过一定的去游离时间或检测到所述接地故障消失后，控制所述两个换流器正常运行。
根据一些实施例，所述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，如果所述高压直流输电系统所连接的交流系统为弱交流系统或新能源接入系统，所述两个换流器至少一个为电网换相换流器时，则所述基于所述直流电流参考值控制所述两个换流器的直流电流相等之后，还包括：根据所述交流系统的需求，控制所述高压直流输电系统切除或投入与所述交流系统连接的交流滤波器。
根据一些实施例，如果所述高压直流输电系统所连接的交流系统为弱交流系统或新能源接入系统，所述两个换流器至少一个为电压源换流器，所述基于所述直流电流参考值控制所述两个换流器的直流电流相等之后，还包括：根据所述交流系统的需求，控制所述电压源换流器输出的无功功率或交流电压。
根据一些实施例，所述弱交流系统为交流系统的短路电流比小于3的交流系统，所述短路电流比为所述交流系统短路容量与所述高压直流输电系统额定功率的比值；所述交流系统的需求包括无功功率需求和交流电压限制。
根据一些实施例，所述直流侧接地故障包括：阀区直流侧接地故障、极区接地故障、双极区接地故障、直流线路区接地故障和接地极线路区接地故障的至少一种；所述阀区直流侧接地故障包括：换流器直流侧高压母线接地、换流器直流侧低压母线接地的至少一种；所述极区接地故障包括：极母线接地、极中点接地、极中性母线接地的至少一种；所述双极区接地故障包括：双极中性母线接地故障；所述直流线路区接地故障包括：直流线路接地故障；所述接地极线路区接地故障包括：接地极线路接地故障。
根据一些实施例，所述直流侧接地故障通过检测保护动作来判断，所述保护包括：换流器差动保护、极差动保护、极母线差动保护、极中性母线差动保护、双极中性母线差动保护、阀组连接线差动保护、线路纵差保护、线路突变量保护、线路行波保护的至少一种。
根据一些实施例，所述高压直流输电系统的需求包括：有功功率需求、无功功率需求、入地电流限制值需求、故障所在直流极的电流限制值需求的至少一种。
根据一些实施例，如果所述高压直流输电系统的需求多于一种，同时给定不同需求的优先级。
根据一些实施例，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：如果所述高压直流输电系统的需求为有功功率需求，将所述有功功率需求除以所述整流站或所述逆变站所有运行的换流器的直流电压绝对值之和，得到所述两个换流器的直流电流参考值。
根据一些实施例，如果所述换流器是六脉动或十二脉动的电网换相换流器，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：如果所述高压直流输电系统的需求为无功功率需求，基于所述无功功率需求、空载直流母线电压、触发角或关断角、换相角确定所述两个换流器的直流电流参考值，整流侧的换流器的计算方法如下。
Figure PCTCN2020139539-appb-000001
逆变侧的换流器的计算方法如下。
Figure PCTCN2020139539-appb-000002
式中，I ord为直流电流参考值，Q conv为六脉动或十二脉动的电网换相换流器的无功功率需求，U di0为六脉动或十二脉动的电网换相换流器的空载直流母线电压，α为换流器的触发角，μ为换流器的换相角，γ为换流器的关断角，所述换流器为六脉动的电网换相换流器时，b＝1/4，当所述换流器为十二脉动的电网换相换流器时，b＝1/2。
根据一些实施例，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：如果所述高压直流输电系统的需求为入地电流限制值需求，所述两个换流器的每个换流器的直流电流参考值大于同站另一直流极的直流电流与所述入地电流限制值的差，且小于同站另一直流极的直流电流与所述入地电流限制值的和。
根据一些实施例，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：如果所述高压直流输电系统的需求为故障所在直流极的电流限制值需求，确定所述两个换流器的直流电流参考值小于故障所在直流极的电流限制值。
根据一些实施例，所述换流器的直流电流包括：所述换流器的高压母线电流、低压母线电流、所述换流器所在直流极的极母线电流或极中性母线电流的至少一种。
根据一些实施例，所述基于所述直流电流参考值控制所述两个换流器的直流电流相等，包括：所述接地故障发生在所述整流站的极母线和所述逆变站的极母线之间的区域时，控制所述接地故障两端的分别位于两个站的所述两个换流器的直流电流相等且为所述直流电流参考值；所述接地故障发生在一个直流极的极中性母线和同站另一直流极的极中性母线之间的区域时，控制所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值；所述接地故障发生在一个直流极的换流器之间的区域时，控制所述接地故障两端的分别位于同一个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值。
根据一些实施例，所述整流站的极母线和所述逆变站的极母线之间的区域包括所述整流站的极母线、所述整流站与极母线连接的换流器直流侧高压母线、所述逆变站的极母线、所述逆变站与极母线连接的换流器直流侧高压母线和直流线路的至少一种；所述一个直流极的极中性母线和同站另一直流极的极中性母线之间的区域包括一个直流极的极中性母线、一个直流极与极中性母线连接的换流器直流侧低压母线、同站另一直流极的极中性母线、同站另一直流极的与极中性母线连接的换流器直流侧低压母线、双极中性母线和接地极线路的至少一种；所述一个直流极的换流器之间的区域包括阀组连接线、与阀组连接线连接的换流器直流侧高压母线或低压母线的至少一种。
根据一些实施例，所述控制所述接地故障两端的分别位于两个站的两个换流器的直流电 流相等且为所述直流电流参考值，包括：所述接地故障两端的分别位于两个站的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值。
根据一些实施例，所述控制所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值，包括：所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值；或者所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器采用最大触发角控制或直流电压控制，另一站的直流极和另一站另一直流极的换流器都采用电流控制且控制目标同为所述直流电流参考值。
根据一些实施例，所述控制所述接地故障两端的分别位于同一个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值，包括：所述接地故障两端的分别位于同一个直流极的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值。
根据一些实施例，所述换流器正常运行，包括：所述换流器按照正常直流电流和正常直流电压运行；所述正常直流电流为0.05至1.6倍额定直流电流之间，所述正常直流电压为0.3至1.3倍额定直流电压之间。
根据一些实施例，所述换流器为电网换相换流器时，所述换流器闭锁包括：控制所述电网换相换流器停发触发脉冲；或/和控制所述电网换相换流器投入旁通对。
根据一些实施例，所述换流器为电压源换流器时，所述换流器闭锁包括：控制所述电压源换流器停发触发脉冲。
根据一些实施例，所述检测到所述接地故障消失包括：检测极母线电压或直流线路电压的绝对值；如果所述极母线电压或直流线路电压的绝对值大于第一直流电压阈值，则判定所述接地故障消失，所述第一直流电压阈值为0.05至1.1倍额定直流电压之间。
本申请实施例还提供一种高压直流输电系统直流侧接地故障控制装置，包括检测单元和控制单元，所述检测单元用于检测所述高压直流输电系统的参数；所述控制单元基于所述高压直流输电系统的参数判定高压直流输电系统直流侧发生接地故障时，控制所述接地故障两端各至少有一个换流器继续运行；基于所述高压直流输电系统的需求确定所述接地故障两端的两个换流器的直流电流参考值，所述两个换流器包括所述接地故障两端各一个继续运行的换流器；基于所述直流电流参考值控制所述两个换流器的直流电流相等；如果所述接地故障发生的区域在所述整流站或所述逆变站内，控制所述高压直流输电系统隔离所述接地故障后控制所述两个换流器正常运行，或者控制所述两个换流器闭锁或所述两个换流器所在直流极闭锁后控制所述高压直流输电系统隔离所述接地故障；如果所述接地故障发生的区域在直流线路或接地极线路，经过一定的去游离时间或检测到所述接地故障消失后，控制所述两个换流器正常运行。
本申请实施例提供的技术方案，在高压直流输电系统直流侧发生接地故障时，通过控制接地故障两端的两个换流器直流电流相等，实现流过接地故障点的故障电流最小，隔离接地故障后控制两个换流器继续运行或者控制两个换流器闭锁后隔离接地故障。
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高压直流输电系统直流侧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高压直流输电系统直流侧接地故障控制方法流程示意图。
图4A是现有技术整流侧极母线接地故障时的仿真试验结果图。
图4B是本申请实施例提供的整流侧极母线接地故障时的仿真试验结果图。
图5是本申请实施例提供的又一种高压直流输电系统直流侧接地故障控制方法流程示意图。
图6是本申请实施例提供的再一种高压直流输电系统直流侧接地故障控制方法流程示意图。
图7是本申请实施例提供的一种高压直流输电系统直流侧接地故障控制装置结构示意图。
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高压直流输电系统的主回路示意图。
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包括第一直流极I110、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、第一直流极中性母线开关119、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。所述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，所述换流器包括但不限于可关断的全控型功率半导体器件。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包括第二低端阀组121、第二高端阀组122、第二低端换流变压器126、第二高端换流变压器127、第二直流极中性母线开关129、第二直流滤波器94和第二平波电抗器92。第二低端阀组121和第二高端阀组122为串联连接。
第二低端阀组121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。第二高端阀组122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。第二低端换流器3和第二高端换流器4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、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、第三直流极中性母线开关219、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包括第四低端阀组221、第四高端阀组222、第四低端换流变压器226、第四高端换流变压器227、第四直流极中性母线开关229、第二直流滤波器98和第二平波电抗器96。第四低端阀组221和第四高端阀组222为串联连接。
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。第四低端换流器7和第四高端换流器8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，包括但不限于机械开关、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，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压源换流器，则为柔性特高压直流输电系统。其中，电压源换流器具有调节电压到零压或负压的能力，如基于全桥子模块的模块化多电平换流器、基于半桥子模块和全桥子模块混合的模块化多电平换流器。
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。其中，电压源换流器具有调节电压到零压或负压的能力，如基于全桥子模块的模块化多电平换流器、基于半桥子模块和全桥子模块混合的模块化多电平换流器。
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。其中，电压源换流器可不具有调节电压到零压或负压的能力，如基于半桥子模块的模块化多电平换流器。
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：高端换流器直流侧的高压母线电流IDC1P、低压母线电流IDC1N，低端换流器直流侧的高压母线电流IDC2P、低压母线电流IDC2N，极母线电流IDL，极中性母线电流IDNC，直流滤波器首端电流IZT1，接地极电流IDEL，极母线电压UDL和极中性母线电压UDN。
高压直流输电系统发生直流侧接地故障包括但不限于阀区直流侧接地故障、极区接地故障、双极区接地故障、直流线路区接地故障和接地极线路区接地故障的至少一种。阀区直流侧接地故障包括但不限于换流器直流侧高压母线接地、换流器直流侧低压母线接地的至少一种。极区接地故障包括但不限于极母线接地、极中点接地、极中性母线接地的至少一种。双极区接地故障包括但不限于双极中性母线接地故障。直流线路区接地故障包括但不限于直流线路接地故障。接地极线路区接地故障包括但不限于接地极线路接地故障。
直流侧接地故障通过检测直流电流的差流、线路突变量或行波并导致相应的保护动作来判断。保护包括但不限于换流器差动保护、极差动保护、极母线差动保护、极中性母线差动保护、双极中性母线差动保护、阀组连接线差动保护、线路纵差保护、线路突变量保护、线 路行波保护的至少一种。
图2是本申请实施例提供的一种高压直流输电系统直流侧接地故障控制方法流程示意图，示出了当整流站100第一直流极I110的第一高端换流器1直流侧的高压母线(测点IDC1P靠近换流器侧)发生接地故障时的控制流程。
整流站100第一直流极I110和逆变站200第三直流极I210的换流器都为电网换相换流器或电压源换流器(半桥和全桥混合子模块结构)，发生直流侧接地故障前，双极全阀组运行。当高压直流输电系统整流站100第一直流极I110的第一高端换流器1直流侧的高压母线(测点IDC1P靠近换流器侧)发生接地故障时，控制流程如下。
在S110中，控制接地故障两端各至少有一个换流器继续运行。
具体而言，如果接地故障在两个直流极之间，控制接地故障两端两个直流极各至少有一个换流器继续运行。如果接地故障在一个直流极内，控制接地故障所在直流极至少有两个换流器继续运行。
通过换流器差动保护动作来判断极母线接地故障，换流器差动保护动作判据如下。
IDiff_v＝|IDC1P–IDC1N|，
IRes_v＝|IDC1P+IDC1N|/2，
IDiff_v>max(Iv_set,kv_set*IRes_v)。
其中，IDiff_v为换流器差动电流，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，IRes_v为换流器差动保护的制动电流，Iv_set为换流器差动保护的起动电流定值，kv_set为换流器差动保护的比率系数。
换流器差动保护动作时，控制接地故障两端两个直流极各至少有一个换流器继续运行。本实施例中，控制第一高端换流器1闭锁，第一低端换流器2继续运行；控制第三高端换流器5闭锁，第三低端换流器6继续运行。
如果第一高端换流器1和第三高端换流器5为电网换相换流器，控制其闭锁过程为：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。
如果第一高端换流器1和第三高端换流器5为电压源换流器，控制其闭锁过程为：控制第一高端换流器1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，同时控制第三高端换流器5立即停发触发脉冲，跳开第三高端换流器5的第三高端换流变压器进线开关231，闭合第三高端阀组第二旁通开关52。
在S120中，基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值。
高压直流输电系统的需求包括但不限于有功功率需求、无功功率需求、入地电流限制值需求、故障所在直流极的电流限制值需求中的至少一种，如果高压直流输电系统的需求多于一种，同时给定不同需求的优先级。
以整流站100或逆变站200的有功功率需求和入地电流限制值需求为例，如下式所示。
I ord_p2＝P ord/(U d_p2c1+U d_p2c2)，
I ord_p1≥I ord_p2-I del_lim且I ord_p1≤I ord_p2+I del_lim。
式中，I ord_p1、I ord_p2分别为极I和极II的直流电流参考值，I del_lim为入地电流限制值，P ord为有功功率需求值，U d_p2c1为极II高端换流器的直流电压，U d_p2c2为极II低端换流器的直流电压。
给定整流站100第一直流极I110的第一低端换流器2和逆变站200第三直流极I210的第三低端换流器6的直流电流参考值为I ord_p1。
在S130中，基于直流电流参考值控制接地故障两端的两个换流器的直流电流相等。
控制整流站100第一直流极I110的第一低端换流器2的极母线电流IDL与逆变站200第三直流极I210的第三低端换流器6的极母线电流IDL相等且为I ord_p1，控制整流站100第二直流极II120的第二高端换流器4和第二低端换流器3的极母线电流IDL或极中性母线电流IDNC为I ord_p2。
在S140中，控制高压直流输电系统隔离接地故障后控制两个换流器正常运行。
控制整流站100第一直流极I110的第一高端阀组111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。
控制整流站100第一直流极I110的第一低端换流器2和逆变站200第三直流极I210的第三低端换流器6正常运行，控制方法为：整流站100第一直流极I110的第一低端换流器2采用电流控制来控制直流电流，逆变站200第三直流极I210的第三低端换流器6采用最大触发角控制或直流电压控制来控制直流电压。
图3是本申请实施例提供的另一种高压直流输电系统直流侧接地故障控制方法流程示意图，示出了当整流站100第一直流极I110的极母线(测点IDC1P和IDL之间)发生直流侧接地故障时的控制流程。
整流站100第一直流极I110和逆变站200第三直流极I210的换流器都为电网换相换流器(双十二脉动换流器)，发生直流侧接地故障前，双极全阀组运行。当高压直流输电系统整流站100第一直流极I110的极母线(测点IDC1P和IDL之间)发生接地故障时，控制流程如下。
在S210中，控制接地故障两端各至少有一个换流器继续运行。
通过极母线差动保护动作来判断极母线接地故障，极母线差动保护动作判据如下。
正常运行、仅高端阀组运行时，
IDiff_p＝|IDC1P–IDL+IZT1|，
IRes_p＝max(IDC1P,IDL,IZT1)，
IDiff_p>max(Ip_set,kp_set*IRes_p)。
仅低端阀组运行时，
IDiff_p＝|IDC2P–IDL+IZT1|，
IRes_p＝max(IDC2P,IDL,IZT1)，
IDiff_p>max(Ip_set,kp_set*IRes_p)。
其中，IDiff_p为极母线差动电流，IDC1P为高端换流器直流侧的高压母线电流，IDL为极母线电流，IZT1为直流滤波器首端电流，IRes_p为极母线差动保护的制动电流，Ip_set为极母线差动保护的起动电流定值，kp_set为极母线差动保护的比率系数，IDC2P为低端换流器直流侧的高压母线电流。
极母线差动保护动作时，控制接地故障两端两个直流极各至少有一个换流器继续运行。本实施例中，控制第一高端换流器1和第一低端换流器2中的至少一个继续运行，第三高端换流器5和第三低端换流器6中的至少一个继续运行。本实施例以第一高端换流器1和第一低端换流器2，第三高端换流器5和第三低端换流器6都继续运行为例。
在S220中，基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值。
高压直流输电系统的需求包括但不限于有功功率需求、无功功率需求、入地电流限制值需求、故障所在直流极的电流限制值需求中的至少一种，如果高压直流输电系统的需求多于一种，同时给定不同需求的优先级。上述不同需求的优先级可以按极给定。
以整流站100或逆变站200的无功功率需求为例，换流器的无功功率需求计算方法如下。
Q ord_p2＝0.5×I d_p2×U di0_p2c1×(2μ 21+sin2α 21-sin2(α 21+μ 21))/(cosα 21-cos(α 21+μ 21))+0.5×I d_p2×U di0_p2c2×(2μ 22+sin2α 22-sin2(α 22+μ 22))/(cosα 22-cos(α 22+μ 22))，
Q ord_p1＝Q ord-Q ord_p2。
考虑到极I的高端阀组、低端阀组的电路参数相同，因此，高端换流器或低端换流器的无功功率需求为极I的无功功率需求的1/2，具体为：
Q ord_p1c1＝Q ord_p1c2＝Q ord_p1/2。
根据整流站的十二脉动换流器的无功功率需求，直流电流参考值的计算如下。
I ord_p1＝Q ord_p1c1/(0.5×U di0_p1c1×(2μ 11+sin2α 11-sin2(α 11+μ 11))/(cosα 11-cos(α 11+μ 11)))或I ord_p1＝Q ord_p1c2/(0.5×U di0_p1c2×(2μ 12+sin2α 12-sin2(α 12+μ 12))/(cosα 12-cos(α 12+μ 12)))。
式中，I ord_p1为极I和极II的直流电流参考值，Q ord、Q ord_p1、Q ord_p2分别为双极、极I、极II的无功功率需求，I d_p2为极II的直流电流，U di0_p1c1、U di0_p1c2、U di0_p2c1、U di0_p2c2分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器中的六脉动换流器的空载直流电压，α 11、α 12、α 21、α 22分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器的触发角，μ 11、μ 12、μ 21、μ 22分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器的换相角。
给定整流站100第一直流极I110的第一高端换流器1和第一低端换流器2和逆变站200 第三直流极I210的第三高端换流器5和第三低端换流器6的直流电流参考值为I ord_p1。
在S230中，基于直流电流参考值控制接地故障两端的两个换流器的直流电流相等。
控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2的极母线电流IDL与逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6的极母线电流IDL相等且为I ord_p1。
为了实现快速控制，可先控制接地故障两端的两个换流器的触发角为90度后，再基于直流电流参考值控制接地故障两端的两个换流器的直流电流相等。
在S240中，如果高压直流输电系统所连接的交流系统为弱交流系统或新能源接入系统，根据交流系统的需求，控制高压直流输电系统切除或投入与交流系统连接的交流滤波器。
具体而言，如果交流系统过压，或者高压直流输电系统给交流系统提供无功功率，或者高压直流输电系统闭锁后会导致交流系统产生过压，控制高压直流输电系统切除交流滤波器。如果交流系统欠压、或者交流系统给高压直流输电系统提供无功功率，控制高压直流输电系统投入交流滤波器。
本实施例中，当高压直流输电系统输送功率较大时，极母线(测点IDC1P和IDL之间)发生接地故障后，高压直流输电系统闭锁后会导致交流系统产生过压，在换流器闭锁前，切除第一交流滤波器组118中的部分或全部交流滤波器。
上述切除部分或全部交流滤波器后，高压直流输电系统的无功功率需求会发生变化，可重新回到步骤S220，重新基于所述高压直流输电系统的需求确定所述接地故障两端的两个换流器的直流电流参考值，以保证交流系统电压在合理范围内。
具体而言，步骤S220至步骤S240也可循环执行多次后，再往下执行。
在S250中，控制两个换流器所在直流极闭锁后控制高压直流输电系统隔离接地故障。
控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2闭锁，包括控制上述换流器跳开第一高端换流变压器进线开关131和第一低端换流变压器进线开关132，投入旁通对，控制闭合第一高端阀组第二旁通开关12和第一低端阀组第二旁通开关22，停发触发脉冲。控制逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6控制触发角为90度，投入旁通对，控制闭合第三高端阀组第二旁通开关52和第三低端阀组第二旁通开关62，停发触发脉冲。
整流站100拉开第一直流极中性母线开关119，隔离极母线接地故障。
图4A是现有技术整流侧极母线接地故障时的仿真试验结果图。
图4A所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，UAC_RMS为交流系统电压有效值，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW，交流系统额定线电压为775kV，额定相电压447.5。
故障前双极以额定功率运行，当检测到发生极母线永久接地故障时，极母线差动保护 动作，执行极闭锁，闭锁整个直流极，高端换流器和低端换流器都闭锁，BLOCK_IND_V1变位，BLOCK_IND_V2变位。故障点流过的电流等于IDNC-IDL。故障点流过的峰值电流为11007A；故障点的电量Q：2.24Ah；故障点的I 2t：13788.7A 2h；交流系统相电压有效值峰值：606.1kV。
图4B是本申请实施例提供的整流侧极母线接地故障时的仿真试验结果图。
图4B所示UDL为极母线电压，IDL为极母线电流，IDNC为极中性线电流，IDEL为接地极线路电流，UAC_RMS为交流系统电压有效值，BLOCK_IND_V1为高端换流器闭锁信号，BLOCK_IND_V2为低端换流器闭锁信号。特高压直流输电系统额定电压为800kV，额定功率为8000MW，交流系统额定线电压为775kV，额定相电压447.5。
故障前双极以额定功率运行，当检测到发生极母线永久接地故障时，控制接地故障两端两个直流极的换流器直流电流相等，控制高压直流输电系统切除与交流系统连接的交流滤波器，执行极闭锁，闭锁整个直流极，高端换流器和低端换流器都闭锁，BLOCK_IND_V1变位，BLOCK_IND_V2变位。故障点流过的电流等于IDNC-IDL。故障点流过的峰值电流为10109A；故障点的电量Q：0.19Ah；故障点的I 2t：719.7A 2h；交流系统相电压有效值峰值：531.7kV。
通过对比图4A和图4B，基于本申请的方法可减少流入故障点的电流，减少流入接地极线路的电流，减小交流系统过压水平。
图5是本申请实施例提供的又一种高压直流输电系统直流侧接地故障控制方法流程示意图，示出了当高压直流输电系统的直流线路150发生直流侧接地故障时的控制流程。
整流站100第一直流极I110和逆变站200第三直流极I210的换流器都为电网换相换流器，发生直流侧接地故障前，双极全阀组运行。当高压直流输电系统的直流线路150发生接地故障，控制流程如下。
在S310中，控制接地故障两端两直流极各至少有一个换流器继续运行。
通过线路突变量或/和行波保护动作来判断直流线路接地故障。线路突变量保护动作判据如下。
dUDL/dt<dUDL_set，
|UDL|<UDL_set。
其中，dUDL/dt为单位时间的直流电压突变量，dUDL_set为直流电压突变量定值，UDL为极母线电压，UDL_set为直流电压定值。
通过线路突变量或行波保护动作判断直流线路接地故障时，控制接地故障两端两个直流极各至少有一个换流器继续运行。本实施例中，控制第一高端换流器1和第一低端换流器2，第三高端换流器5和第三低端换流器6都继续运行。
在S320中，基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值。
高压直流输电系统的需求包括但不限于有功功率需求、无功功率需求、入地电流限制值、故障所在直流极的电流限制值中的至少一种，如果高压直流输电系统的需求多于一种，同时给定不同需求的优先级。
以整流站100或逆变站200的无功功率需求为例，换流器的无功功率需求计算方法如下。
Q ord_p2＝0.5×I d_p2×U di0_p2c1×(2μ 21+sin2α 21-sin2(α 21+μ 21))/(cosα 21-cos(α 21+μ 21))+0.5×I d_p2×U di0_p2c2×(2μ 22+sin2α 22-sin2(α 22+μ 22))/(cosα 22-cos(α 22+μ 22))，
Q ord_p1＝Q ord-Q ord_p2，
考虑到极I的高端阀组、低端阀组的电路参数相同，因此，高端换流器或低端换流器的无功功率需求为极I的无功功率需求的1/2，具体为
Q ord_p1c1＝Q ord_p1c2＝Q ord_p1/2，
根据整流站的十二脉动换流器的无功功率需求，直流电流参考值的计算如下。
I ord_p1＝Q ord_p1c1/(0.5×U di0_p1c1×(2μ 11+sin2α 11-sin2(α 11+μ 11))/(cosα 11-cos(α 11+μ 11)))或I ord_p1＝Q ord_p1c2/(0.5×U di0_p1c2×(2μ 12+sin2α 12-sin2(α 12+μ 12))/(cosα 12-cos(α 12+μ 12)))。
式中，I ord_p1为极I和极II的直流电流参考值，Q ord、Q ord_p1、Q ord_p2分别为双极、极I、极II的无功功率需求，I d_p2为极II的直流电流，U di0_p1c1、U di0_p1c2、U di0_p2c1、U di0_p2c2分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器中的六脉动换流器的空载直流电压，α 11、α 12、α 21、α 22分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器的触发角，μ 11、μ 12、μ 21、μ 22分别为极I的高端换流器、极I的低端换流器、极II的高端换流器、极II的低端换流器的换相角。
给定整流站100第一直流极I110的第一高端换流器1和第一低端换流器2和逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6的直流电流参考值为I ord_p1。
在S330中，基于直流电流参考值控制接地故障两端的两个换流器的直流电流相等。
控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2的极母线电流IDL与逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6的极母线电流IDL相等且为I ord_p1。
在S340中，经过一定的去游离时间或检测到接地故障消失后，控制两个换流器正常运行。
经过一定的去游离时间或检测到接地故障消失后，控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2，逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6正常运行。控制方法为整流站100第一直流极I110的第一高端换流器1和第一低端换流器2采用电流控制来控制直流电流，逆变站200第三直流极I210的第三高端换流器5和第三低端换流器6采用最大触发角控制或直流电压控制来控制直流电压。
上述检测到接地故障消失包括通过检测极母线电压UDL或直流线路电压的绝对值，如果极母线电压UDL或直流线路电压的绝对值大于第一直流电压阈值，则判定接地故障消失， 第一直流电压阈值为0.03至1.3倍额定直流电压之间。
图6是本申请实施例提供的再一种高压直流输电系统直流侧接地故障控制方法流程示意图，示出了当高压直流输电系统整流站100第一直流极I110的阀组连接线(测点IDC1N和IDC2P之间)发生接地故障时的控制流程。
整流站100第一直流极I110和逆变站200第三直流极I210的换流器都为电网换相换流器，发生直流侧接地故障前，双极全阀组运行。当高压直流输电系统整流站100第一直流极I110(测点IDC1N和IDC2P之间)的阀组连接线发生接地故障时，控制流程如下。
在S410中，控制接地故障两端各至少有一个换流器继续运行。
通过阀组连接线差动保护动作来判断阀组连接线接地故障，阀组连接线差动保护动作判据如下。
高端阀组和低端阀组同时运行时，
IDiff_c＝|IDC1N–IDC2P|，
IRes_c＝|IDC1N+IDC2P|/2，
IDiff_c>max(Ic_set,kc_set*IRes_c)。
其中，IDiff_c为阀组连接线差动电流，IDC1N为高端换流器直流侧的低压母线电流，IDC2P为低端换流器直流侧的高压母线电流，IRes_c为阀组连接线差动保护的制动电流，Ic_set为阀组连接线差动保护的起动电流定值，kc_set为阀组连接线差动保护的比率系数。
阀组连接线差动保护动作时，控制接地故障所在直流极至少有两个换流器继续运行。本实施例中，控制第一高端换流器1和第一低端换流器2继续运行。
在S420中，基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值。高压直流输电系统的需求包括但不限于有功功率需求、无功功率需求、入地电流限制值、故障所在直流极的电流限制值中的至少一种，如果高压直流输电系统的需求多于一种，同时给定不同需求的优先级。
以整流站100或逆变站200的故障所在直流极的电流限制值需求为例，如下式所示。
I ord_p1≤I flt_lim。
式中，I ord_p1为极I的直流电流参考值，I flt_lim为故障所在直流极的电流限制值。
给定整流站100第一直流极I110的第一高端换流器1和第一低端换流器2的直流电流参考值为I ord_p1。
如果I flt_lim为零，还可控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2移相来实现。
在S430中，根据接地故障发生的区域，基于直流电流参考值控制接地故障两端的两个换流器的直流电流相等。
控制整流站100第一直流极I110的第一高端换流器1直流侧的低压母线电流IDC1N和 第一低端换流器2直流侧的高压母线电流IDC2P相等且为I ord_p1。
在S440中，控制两个换流器所在直流极闭锁后控制高压直流输电系统隔离接地故障。
控制整流站100第一直流极I110的第一高端换流器1和第一低端换流器2闭锁。具体而言，控制上述换流器跳开第一高端换流变压器进线开关131和第一低端换流变压器进线开关132，投入旁通对，控制闭合第一高端阀组第二旁通开关12和第一低端阀组第二旁通开关22，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和第三低端换流器6控制触发角为90度，投入旁通对，控制闭合第三高端阀组第二旁通开关52和第三低端阀组第二旁通开关62，停发触发脉冲。
整流站100拉开第一直流极中性母线开关119，隔离阀组连接线接地故障。
图7是本申请实施例提供的一种高压直流输电系统直流侧接地故障控制装置300结构示意图，装置包括检测单元310和控制单元320。
检测单元310用于检测高压直流输电系统的参数，包括高端换流器直流侧的高压母线电流IDC1P、低压母线电流IDC1N，低端换流器直流侧的高压母线电流IDC2P、低压母线电流IDC2N，极母线电流IDL，极中性母线电流IDNC，直流滤波器首端电流IZT1，接地极电流IDEL，极母线电压UDL和极中性母线电压UDN，高压直流输电系统的需求。
控制单元320基于高压直流输电系统的直流电流判定高压直流输电系统直流侧发生接地故障时，控制接地故障两端各至少有一个换流器继续运行，基于高压直流输电系统的需求确定接地故障两端的两个换流器的直流电流参考值，上述两个换流器包括接地故障两端各一个继续运行的换流器。基于直流电流参考值控制上述两个换流器的直流电流相等。如果接地故障发生的区域在整流站或逆变站内，控制高压直流输电系统隔离接地故障后控制上述两个换流器正常运行，或者控制上述两个换流器闭锁或上述两个换流器所在直流极闭锁后控制高压直流输电系统隔离上述接地故障；如果接地故障发生的区域在直流线路或接地极线路，经过一定的去游离时间或检测到接地故障消失后，控制上述两个换流器正常运行。
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 (24)

  1. 一种高压直流输电系统直流侧接地故障控制方法，所述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，所述直流极包括至少一个换流器，当发生所述直流侧接地故障时，所述控制方法包括：
    控制所述接地故障两端各至少有一个换流器继续运行；
    基于所述高压直流输电系统的需求确定所述接地故障两端的两个换流器的直流电流参考值，所述两个换流器包括所述接地故障两端各一个继续运行的换流器；
    基于所述直流电流参考值控制所述两个换流器的直流电流相等；
    如果所述接地故障发生的区域在所述整流站或所述逆变站内，控制所述高压直流输电系统隔离所述接地故障后控制所述两个换流器正常运行，或者控制所述两个换流器或所述两个换流器所在直流极闭锁后控制所述高压直流输电系统隔离所述接地故障；如果所述接地故障发生的区域在直流线路或接地极线路，经过一定的去游离时间或检测到所述接地故障消失后，控制所述两个换流器正常运行。
  2. 如权利要求1所述的控制方法，其中，所述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，如果所述高压直流输电系统所连接的交流系统为弱交流系统或新能源接入系统，所述两个换流器至少一个为电网换相换流器时，则所述基于所述直流电流参考值控制所述两个换流器的直流电流相等之后，还包括：
    根据所述交流系统的需求，控制所述高压直流输电系统切除或投入与所述交流系统连接的交流滤波器。
  4. 如权利要求1所述的控制方法，其中，如果所述高压直流输电系统所连接的交流系统为弱交流系统或新能源接入系统，所述两个换流器至少一个为电压源换流器，所述基于所述直流电流参考值控制所述两个换流器的直流电流相等之后，还包括：
    根据所述交流系统的需求，控制所述电压源换流器输出的无功功率或交流电压。
  5. 如权利要求3或4所述的控制方法，其中，所述弱交流系统为交流系统的短路电流比小于3的交流系统，所述短路电流比为所述交流系统短路容量与所述高压直流输电系统额定功率的比值；所述交流系统的需求包括无功功率需求和交流电压限制。
  6. 如权利要求1所述的控制方法，其中，所述直流侧接地故障包括：阀区直流侧接地故障、极区接地故障、双极区接地故障、直流线路区接地故障和接地极线路区接地故障的至少一种；
    所述阀区直流侧接地故障包括：换流器直流侧高压母线接地、换流器直流侧低压母线接地的至少一种；
    所述极区接地故障包括：极母线接地、极中点接地、极中性母线接地的至少一种；
    所述双极区接地故障包括：双极中性母线接地故障；
    所述直流线路区接地故障包括：直流线路接地故障；
    所述接地极线路区接地故障包括：接地极线路接地故障。
  7. 如权利要求1所述的控制方法，其中，所述直流侧接地故障通过检测保护动作来判断，所述保护包括：
    换流器差动保护、极差动保护、极母线差动保护、极中性母线差动保护、双极中性母线差动保护、阀组连接线差动保护、线路纵差保护、线路突变量保护、线路行波保护的至少一种。
  8. 如权利要求1所述的控制方法，其中，所述高压直流输电系统的需求包括：有功功率需求、无功功率需求、入地电流限制值需求、故障所在直流极的电流限制值需求的至少一种。
  9. 如权利要求8所述的控制方法，其中，如果所述高压直流输电系统的需求多于一种，同时给定不同需求的优先级。
  10. 如权利要求8所述的控制方法，其中，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：
    如果所述高压直流输电系统的需求为有功功率需求，将所述有功功率需求除以所述整流站或所述逆变站所有运行的换流器的直流电压绝对值之和，得到所述两个换流器的直流电流参考值。
  11. 如权利要求8所述的控制方法，其中，如果所述换流器是六脉动或十二脉动的电网换相换流器，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：
    如果所述高压直流输电系统的需求为无功功率需求，基于所述无功功率需求、空载直流母线电压、触发角或关断角、换相角确定所述两个换流器的直流电流参考值，
    整流侧的换流器的计算方法如下，
    Figure PCTCN2020139539-appb-100001
    逆变侧的换流器的计算方法如下，
    Figure PCTCN2020139539-appb-100002
    式中，I ord为直流电流参考值，Q conv为六脉动或十二脉动的电网换相换流器的无功功率需求，U di0为六脉动或十二脉动的电网换相换流器的空载直流母线电压，α为换流器的触发角，μ为换流器的换相角，γ为换流器的关断角，所述换流器为六脉动的电网换相换流器时，b＝1/4，所述换流器为十二脉动的电网换相换流器时，b＝1/2。
  12. 如权利要求8所述的控制方法，其中，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：
    如果所述高压直流输电系统的需求为入地电流限制值需求，所述两个换流器的每个换流器的直流电流参考值大于同站另一直流极的直流电流与所述入地电流限制值的差，且小于同站另一直流极的直流电流与所述入地电流限制值的和。
  13. 如权利要求8所述的控制方法，其中，所述基于所述高压直流输电系统的需求确定所述两个换流器的直流电流参考值，包括：
    如果所述高压直流输电系统的需求为故障所在直流极的电流限制值需求，确定所述两个换流器的直流电流参考值小于故障所在直流极的电流限制值。
  14. 如权利要求1所述的控制方法，其中，所述换流器的直流电流包括：
    所述换流器的高压母线电流、低压母线电流、所述换流器所在直流极的极母线电流或极中性母线电流的至少一种。
  15. 如权利要求1所述的控制方法，其中，所述基于所述直流电流参考值控制所述两个换流器的直流电流相等，包括：
    所述接地故障发生在所述整流站的极母线和所述逆变站的极母线之间的区域时，控制所述接地故障两端的分别位于两个站的所述两个换流器的直流电流相等且为所述直流电流参考值；
    所述接地故障发生在一个直流极的极中性母线和同站另一直流极的极中性母线之间的区域时，控制所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值；
    所述接地故障发生在一个直流极的换流器之间的区域时，控制所述接地故障两端的分别位于同一个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值。
  16. 如权利要求15所述的控制方法，其中，
    所述整流站的极母线和所述逆变站的极母线之间的区域包括所述整流站的极母线、所述整流站与极母线连接的换流器直流侧高压母线、所述逆变站的极母线、所述逆变站与极母线连接的换流器直流侧高压母线和直流线路的至少一种；
    所述一个直流极的极中性母线和同站另一直流极的极中性母线之间的区域包括一个直流极的极中性母线、一个直流极与极中性母线连接的换流器直流侧低压母线、同站另一直流极的极中性母线、同站另一直流极的与极中性母线连接的换流器直流侧低压母线、双极中性母线和接地极线路的至少一种；
    所述一个直流极的换流器之间的区域包括阀组连接线、与阀组连接线连接的换流器直流侧高压母线或低压母线的至少一种。
  17. 如权利要求15所述的控制方法，其中，所述控制所述接地故障两端的分别位于两个站的两个换流器的直流电流相等且为所述直流电流参考值，包括：
    所述接地故障两端的分别位于两个站的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值。
  18. 如权利要求15所述的控制方法，其中，所述控制所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值，包括：
    所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值；或者
    所述接地故障两端的分别位于同一个站两个直流极的所述两个换流器采用最大触发角控制或直流电压控制，另一站的直流极和另一站另一直流极的换流器都采用电流控制且控制目标同为所述直流电流参考值。
  19. 如权利要求15所述的控制方法，其中，所述控制所述接地故障两端的分别位于同一个直流极的所述两个换流器的直流电流相等且为所述直流电流参考值，包括：
    所述接地故障两端的分别位于同一个直流极的所述两个换流器都采用电流控制且控制目标同为所述直流电流参考值。
  20. 如权利要求1所述的控制方法，其中，所述换流器正常运行，包括：
    所述换流器按照正常直流电流和正常直流电压运行；
    所述正常直流电流为0.05至1.6倍额定直流电流之间，所述正常直流电压为0.3至1.3倍额定直流电压之间。
  21. 如权利要求1所述的控制方法，其中，所述换流器为电网换相换流器时，所述换流器闭锁包括：
    控制所述电网换相换流器停发触发脉冲；或/和
    控制所述电网换相换流器投入旁通对。
  22. 如权利要求1所述的控制方法，其中，所述换流器为电压源换流器时，所述换流器闭锁包括：
    控制所述电压源换流器停发触发脉冲。
  23. 如权利要求1所述的控制方法，其中，所述检测到所述接地故障消失包括：
    检测极母线电压或直流线路电压的绝对值；
    如果所述极母线电压或直流线路电压的绝对值大于第一直流电压阈值，则判定所述接地故障消失，所述第一直流电压阈值为0.05至1.1倍额定直流电压之间。
  24. 一种高压直流输电系统直流侧接地故障控制装置，包括：
    检测单元，用于检测所述高压直流输电系统的参数；
    控制单元，基于所述高压直流输电系统的参数判定高压直流输电系统直流侧发生接地故障时，控制所述接地故障两端各至少有一个换流器继续运行；基于所述高压直流输电系统的需求确定所述接地故障两端的两个换流器的直流电流参考值，所述两个换流器包括所述接地故障两端各一个继续运行的换流器；基于所述直流电流参考值控制所述两个换流器的直流电流相等；如果所述接地故障发生的区域在所述整流站或所述逆变站内，控制所述高压直流输电系统隔离所述接地故障后控制所述两个换流器正常运行，或者控制所述两个换流器或所述两个换流器所在直流极闭锁后控制所述高压直流输电系统隔离所述接地故障；如果所述接地故障发生的区域在直流线路或接地极线路，经过一定的去游离时间或检测到所述接地故障消失后，控制所述两个换流器正常运行。
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