CN111244998B - Control method and device for converting single-pole ground return wire into metal return wire and storage medium - Google Patents
Control method and device for converting single-pole ground return wire into metal return wire and storage medium Download PDFInfo
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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
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/262—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 involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—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 involving signal transmission between at least two stations
- H02H7/263—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 involving signal transmission between at least two stations involving transmissions of measured values
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- 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]
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Abstract
The invention discloses a method for controlling a single-pole ground return wire to be converted into a metal return wire, which is suitable for a multi-terminal direct-current power transmission system and comprises the following steps: after the metal return wire connection is started, each sending end converter station controls a ground return wire change-over switch MRS of the station to be closed, and then an MRS on-position signal is sent to other sending end converter stations; after receiving MRS (signal to plate) on-position signals of all the sending end converter stations and after a preset time delay, each sending end converter station synchronously sends a brake-separating control command to a metal return line change-over switch MRTB of the station; and after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be larger than a preset current value, the metal loop change-over switch MRTB is immediately switched off. The invention also discloses a corresponding control device and a storage medium, and by implementing the method, the condition that the metal loop conversion fails due to the fact that MRTB is triggered to prohibit the opening logic can be effectively avoided in the process of converting the ground loop into the metal loop, and the operation reliability of the multi-terminal direct current system is improved.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to a method and a device for controlling a single-pole ground return wire to be converted into a metal return wire and a storage medium.
Background
The direct current transmission system has multiple operation modes, including bipolar operation, monopole earth return operation and monopole metal return operation. When one DC pole is overhauled or has a fault, the other DC pole can continue to operate in a single-pole ground loop operation mode, and the reliability of the DC power transmission system is improved. However, long-term ground return operation may affect normal and safe operation of the dc transmission system and affect the ecological environment of the ground pole accessories, so in order to reduce the operation time of the single-pole ground return mode caused by a fault, it is very important in the dc transmission system to control the conversion of the single-pole ground return into the single-pole metal return operation mode under the fault condition.
A transmitting end converter station of the direct current transmission system is configured with a Metallic Return Transfer Breaker (MRTB) and a ground Return switch (MRS), and when the direct current transmission system is in a single-pole ground Return operation, the MRTB is in a closed state and the MRS is in an open state. The principle of controlling the conversion of the single-pole ground return wire into the single-pole metal return wire is as follows: and controlling the switch MRS to be closed to form a state that a metal return line current path and a ground return line current path coexist, and sending a brake separating instruction to control the MRTB brake separation after the transmitting end converter station detects that the MRS in the station is closed. If the current of the metal return wire flowing through the station is larger than the threshold value, the switch MRTB is switched off, and the current path of the earth return wire is disconnected, so that the operation conversion from the earth return wire to the metal return wire is completed. If the current of the metal return wire is smaller than the threshold value, the MRTB forbids the switching-off logic, the switch MRTB does not switch off, and the conversion from the ground return wire to the metal return wire fails.
However, in the process of implementing the invention, the inventor finds that the prior art has at least the following problems: in a multi-terminal direct current transmission system, because a plurality of converter stations control current uniformly, the distribution of current on a ground return wire and a metal return wire is complex, when MRS of each converter station is controlled to be closed, the multi-terminal ground return wire and the metal return wire exist at the same time, and current level combination exists among the converter stations. After a certain converter station controls the MRTB to be switched off, the metal return current of another converter station becomes smaller than a threshold value under certain current level combination, and the MRTB forbidden switching-off logic is triggered, so that the switch MRTB of the circulating current station cannot be switched off.
Disclosure of Invention
The embodiment of the invention aims to provide a method, a device and a storage medium for controlling a single-pole ground return wire to be converted into a metal return wire, which can effectively avoid the condition that MRTB forbids switching-off logic to cause failure of metal return wire conversion in the process of converting the ground return wire of a multi-terminal direct-current power transmission system into the metal return wire, and improve the operation reliability of the multi-terminal direct-current system.
In order to achieve the above object, an embodiment of the present invention provides a method for controlling a single-pole ground return wire to a metal return wire, which is applicable to a multi-terminal dc power transmission system, and includes:
after the metal return wire connection is started, each sending end converter station controls a ground return wire change-over switch MRS of the station to be closed;
after detecting that a switch MRS of each sending end converter station is closed, each sending end converter station sends an MRS on-position signal to other sending end converter stations;
after receiving MRS (signal to switching System) on-position signals of all the sending end converter stations, each sending end converter station synchronously sends an opening control instruction to a metal return line change-over switch MRTB of the station;
and after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be larger than a preset current value, the metal loop change-over switch MRTB is immediately switched off.
As an improvement of the above solution, the method for controlling the unipolar ground return wire to the metallic return wire further comprises the steps of:
after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be less than or equal to the preset current value, the metal loop change-over switch MRTB keeps a closed state; and the metal return wire is disconnected when the current of the metal return wire is judged to be larger than the preset current value.
As an improvement of the above scheme, before each sending end converter station respectively controls the ground return line change-over switch MRS of its own station to be closed, the method further includes the steps of:
and closing a metal loop isolation disconnecting link in the receiving end converter station control station to start metal loop connection.
As an improvement of the above solution, the method for controlling the unipolar ground return wire to the metallic return wire further comprises the steps of:
each transmitting end converter station sends MRTB sub-bit signals to the receiving end converter station after detecting that a switch MRTB of the transmitting end converter station is disconnected;
and after the receiving end converter station receives the MRTB sub-bit signals of all the transmitting end converter stations, the grounding switch in the station is controlled to be closed.
As an improvement of the above solution, the method for controlling the unipolar ground return wire to the metallic return wire further comprises the steps of:
and after receiving the MRTB branch signals of all the transmitting end converter stations, the receiving end converter station controls the isolation disconnecting link of the earth return line to be disconnected.
As a modification of the above, the preset current value is 20A.
As an improvement of the above scheme, after receiving the MRS on-bit signals of all the transmitting end converter stations, each transmitting end converter station synchronously transmits a switching-off control command to the metal return line transfer switch MRTB of the station, which specifically includes:
after receiving MRS (signal to zero) on-position signals of all the sending end converter stations and after a preset time delay, each sending end converter station synchronously sends a brake-separating control command to a metal return line change-over switch MRTB of the station.
As a modification of the above, the preset time delay is 3 s.
An embodiment of the present invention further provides a control apparatus for a unipolar ground return wire to metal return wire, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, where the processor implements the control method for a unipolar ground return wire to metal return wire according to any one of the above items when executing the computer program.
An embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to execute the method for controlling a unipolar earth return wire to a metal return wire according to any one of the above items.
Compared with the prior art, the method, the device and the storage medium for controlling the conversion of the unipolar ground return wire into the metal return wire have the advantages that after the connection of the metal return wires is started, each sending end converter station controls the ground return wire change-over switch MRS of the station to be closed; after detecting that a switch MRS of each sending end converter station is closed, each sending end converter station sends an MRS on-position signal to other sending end converter stations; after receiving MRS (signal to switching System) on-position signals of all the sending end converter stations, each sending end converter station synchronously sends an opening control instruction to a metal return line change-over switch MRTB of the station; and after receiving the opening control instruction, the metal loop transfer switch MRTB is immediately disconnected when judging that the current of the metal loop flowing through the station is larger than a preset current value. In the process of converting the ground return wire of the multi-terminal direct current transmission system into the metal return wire, after each sending terminal converter station controls the switch MRS of the station to be closed, the switch MRTB is synchronously sent with a brake-separating control instruction after MRS on-bit signals sent by all sending terminal circulating current stations are received. By increasing the interactive communication among the transmitting end converter stations, the simultaneous opening of the switch MRTB is realized, the condition that the metal return wire conversion fails due to the fact that the MRTB is triggered to prohibit the opening logic can be effectively avoided, and the operation reliability of the multi-end direct current system is improved.
Drawings
Fig. 1 is a schematic flowchart of steps of a method for controlling a single-pole ground return to a metallic return according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of steps of another method for controlling a monopole ground return to a metal return according to a second embodiment of the present invention;
fig. 3 is a schematic diagram of single ground return wiring in a three-terminal dc power transmission system according to a second embodiment of the present invention;
fig. 4 is a schematic diagram of a single-pole metal return connection in a three-terminal dc power transmission system according to a second embodiment of the present invention;
fig. 5 is a schematic structural diagram of a control device for converting a single-pole ground return wire into a metallic return wire according to a third embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The method for controlling the conversion of the single-pole ground return wire into the metal return wire is suitable for a multi-terminal direct-current power transmission system. A multi-terminal dc transmission system refers to a dc transmission system comprising a plurality of converter stations. The converter stations comprise a transmitting end converter station and a receiving end converter station. The multi-terminal direct-current transmission system has the most remarkable characteristics of realizing multi-power supply and multi-drop power receiving, provides a more flexible transmission mode, and has various operation modes, including bipolar operation, monopolar ground loop operation, monopolar metal loop operation and the like. Each transmitting end converter station is provided with a metallic return line change-over switch MRTB and a ground return line change-over switch MRS, and each receiving end converter station is provided with a metallic return line isolation disconnecting link Q71, a ground return line isolation disconnecting link Q5 and an in-station grounding switch HSGS. When the multi-terminal direct current power transmission system is in the single-pole ground return wire change-over switch, the metal return wire change-over switch MRTB and the ground return wire isolation disconnecting link Q5 are in a closed state; the ground return line changeover switch MRS, the metallic return line isolation switch Q71, and the intra-station ground switch HSGS are in an off state. When the multi-terminal direct-current power transmission system is in a single-pole metal return line change-over switch, the ground return line change-over switch MRS, the metal return line isolation disconnecting link Q71 and the station internal grounding switch HSGS are in a closed state; the metallic return transfer switch MRTB and the earth return isolation switch Q5 are in an open state.
Fig. 1 is a schematic flowchart of steps of a method for controlling a single-pole ground return to a metallic return according to an embodiment of the present invention. The control method for converting the monopole earth return wire into the metal return wire comprises the steps S11 to S14:
and S11, after the metallic return wire connection is started, each sending end converter station controls the ground return wire change-over switch MRS of the station to be closed.
And S12, after each sending end converter station detects that the switch MRS of the station is closed, sending an MRS on-bit signal to other sending end converter stations.
And S13, after each sending end converter station receives MRS on-bit signals of all the sending end converter stations, synchronously sending an opening control command to the metal return line change-over switch MRTB of the station.
And S14, after each metal loop change-over switch MRTB receives the opening control instruction, when the current of the metal loop flowing through the station is judged to be larger than a preset current value, the metal loop change-over switch MRTB is immediately disconnected.
In the embodiment of the invention, in the process of converting the multi-terminal direct-current transmission system from the single-pole ground return operation mode to the single-pole metal return operation mode, each transmitting-end converter station sends a closing control instruction to the ground return conversion switch MRS of the station, so that the switch MRS is in a closed state after receiving the closing control instruction. After each sending end converter station detects that the switch MRS of the station is closed, information interaction with each other sending end converter station is established, namely, an MRS bit-combination signal is sent to other sending end converter stations, and meanwhile, the MRS bit-combination signal transmitted by other sending end converter stations is received. And after the sending end converter stations receive MRS on-position signals of all the sending end converter stations, each sending end converter station synchronously sends an opening control instruction to the metal return line change-over switch MRTB of the station. And after receiving the opening control instruction, the metal loop transfer switch MRTB detects whether the metal loop current IdL _ op flowing through the station is larger than a preset current value. When the metal loop current IdL _ op is judged to be larger than the preset current value, the switch MRTB is immediately in an off state. Therefore, after each sending-end converter station synchronously sends a switching-off control instruction, if the metal loop current of each sending-end converter station is greater than the preset current value, each switch MRTB realizes the effect of simultaneous switching-off.
In the prior art, after each sending-end converter station controls a switch MRS of the station to be closed, a switching-off control command is sent to a switch MRTB of the station, and the switch MRTB is controlled to be opened. After each sending end converter station completes the operations of closing the switch MRS and opening the switch MRTB respectively, the conversion from the single-pole earth return operation to the single-pole metal return operation is further completed. However, after the switch MRS is closed, the multi-terminal dc power transmission system will form a state in which the metal return current path and the ground return current path coexist, and at this time, the current distribution on the ground return and the metal return is complicated, and there are cases where various current levels are combined. After one converter station controls the MRTB to be switched off, the metal return wire current of the other converter station becomes smaller than a threshold value under certain current level combination, and the MRTB forbidden switching-off logic is triggered, so that the switch MRTB of the circulating current station cannot be switched off, and the conversion from the single-pole ground return wire operation to the single-pole metal return wire operation fails.
In the method for controlling a single-pole ground return wire to convert a metal return wire provided in the embodiment of the present invention, by increasing information interaction between each transmitting-end converter station, a switching-off control instruction for the switch MRTB of the local station is synchronously sent out, so that a situation that the metal return wire conversion fails due to the fact that the MRTB prohibits the switching-off logic and the metal return wire conversion fails due to the fact that the current of the metal return wire of another transmitting-end converter station becomes smaller than a threshold value under certain current level combinations after the switch MRTB of a certain transmitting-end converter station is switched off in one step is effectively avoided, and the operation reliability of a multi-terminal dc system is improved.
Fig. 2 is a schematic flow chart of steps of another method for controlling a unipolar ground return to a metallic return according to a second embodiment of the present invention. The second embodiment of the present invention is implemented on the basis of the first embodiment, and includes all the implementation steps of the first embodiment, and the method for controlling a unipolar ground return wire to a metal return wire includes steps S21 to S26:
and S21, closing a metal loop isolation knife switch in the receiving end converter station control station to start metal loop connection.
In the process of converting the single-pole ground return operation mode into the single-pole metal return operation mode, the multi-terminal direct current transmission system starts metal return connection by closing a metal return isolation switch Q71. The metal return isolation switch Q71 is disposed in the receiving end converter station.
And S22, after the metallic return wire connection is started, each sending end converter station controls the ground return wire change-over switch MRS of the station to be closed.
And S23, after each sending end converter station detects that the switch MRS of the station is closed, sending an MRS on-bit signal to other sending end converter stations.
And S24, after each sending end converter station receives MRS on-bit signals of all the sending end converter stations, synchronously sending an opening control command to the metal return line change-over switch MRTB of the station.
S25, after each metal loop transfer switch MRTB receives the switching-off control instruction, when the current of the metal loop passing through the station is judged to be larger than a preset current value, the metal loop transfer switch MRTB is immediately disconnected; wherein the preset current value is 20A.
S26, after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be less than or equal to the preset current value, the metal loop change-over switch MRTB keeps a closed state; and the metal return wire is disconnected when the current of the metal return wire is judged to be larger than the preset current value.
In the embodiment of the invention, after receiving the MRS on-bit signals of all the sending end converter stations, each sending end converter station synchronously sends the opening control instruction to the metal return line change-over switch MRTB of the station. However, at this time, since the multi-terminal dc power transmission system is in a state where the earth return current path and the metal return current path coexist, a certain transmitting-end converter station may cause the metal return current IdL _ op to be smaller than a preset current value under a current level combination, and in this case, even if the switch MRTB receives the opening control instruction, the opening condition is not satisfied, the MRTB is triggered to prohibit the opening logic, and the switch MRTB is kept in a closed state. And then, after the switches MRTB of other sending end converter stations meeting the switching-off condition are separated, the current between the stations is transferred, after the current flows through the sending end converter stations not meeting the switching-off condition, the metal return current IdL _ op is larger than a preset current value, the MRTB prohibits the switching-off logic from returning, and the switch MRTB is in a disconnected state when judging that the metal return current is larger than the preset current value, so that the conversion from the operation of a single-pole ground return wire to the operation of a single-pole metal return wire is completed.
It should be noted that, in the multi-terminal direct-current transmission system, there is no situation that no current flows through the metal loop or the current of the metal loop flowing through the metal loop is less than or equal to the preset current value after the switch MRS of each sending-end converter station is closed.
Further, referring to fig. 2, the method for controlling the unipolar ground return to metal return further includes steps S27 to S28:
s27, after each transmitting end converter station detects that a switch MRTB of the transmitting end converter station is disconnected, transmitting an MRTB sub-position signal to the receiving end converter station;
s28, after the receiving end converter station receives the MRTB sub-position signals of all the transmitting end converter stations, controlling grounding switches in the station to be closed; and controlling the earth return wire isolation disconnecting link to be disconnected.
When the switch MRS of each transmitting end converter station is closed and the switch MRTB is opened, the receiving end converter station controls the grounding switch HSGS in the control station to be closed and the ground return isolation knife switch Q5 to be opened, and the unipolar metal return path of each converter station of the multi-end direct-current transmission system is connected, so that the conversion from the operation of the unipolar ground return to the operation of the unipolar metal return is completed.
Further, step S24 is specifically: after receiving MRS (signal to zero) on-position signals of all the sending end converter stations and after a preset time delay, each sending end converter station synchronously sends a brake-separating control command to a metal return line change-over switch MRTB of the station.
Preferably, the preset time delay is 3 s.
Specifically, after each MRS switch is closed, the multi-terminal dc transmission system is in a state where the earth return current path and the metal return current path coexist, and the current in the system is redistributed. The time length is delayed for 3s, so that the transient process of the system can be avoided, and a certain time is reserved to detect whether the current of the metal return wire flowing through the MRS switch is greater than a preset current value, so that whether the MRTB forbids the opening logic is judged. The detection time for disabling the opening logic is typically 500 ms. After the preset time delay of 3s, if the MRTB forbids the switching-off logic, the MRTB is not triggered, the MRS is successfully switched on, a metal return current loop is formed, and then each transmitting end converter station synchronously transmits a switching-off control command to the metal return changeover switch MRTB of the station, so that the subsequent operations such as the disconnection of the switch MRTB are carried out, and the success rate of the process of converting the single-pole ground return into the metal return is further ensured.
As a preferred embodiment, referring to fig. 3-4, fig. 3 is a schematic diagram of single-pole ground return wiring in a three-terminal dc power transmission system according to a second embodiment of the present invention; fig. 4 is a schematic diagram of a single-pole metal return connection in a three-terminal dc power transmission system according to a second embodiment of the present invention.
The three-terminal direct-current transmission system comprises a sending-end converter station A, a sending-end converter station B and a receiving-end converter station C, wherein the station B is provided with a bus bar to realize three-station electrical connection. Station a is equipped with a metallic return line changeover switch MRTB1 and a ground return line changeover switch MRS 1; station B is equipped with a metallic return line changeover switch MRTB2 and a ground return line changeover switch MRS 2; station C is equipped with a metallic return isolation switch Q71, a ground return isolation switch Q5, and an intra-station ground switch HSGS. Under the single-pole earth return wire operation mode, the three-terminal direct current power transmission system has the following switching states: MRTB1 closed, MRTB2 closed, Q5 closed, MRS1 open, MRS2 open, Q71 open, HSGS open; under the operation mode of the single-pole metal return wire, the switching states are respectively as follows: MRTB1 open, MRTB2 open, Q5 open, MRS1 closed, MRS2 closed, Q71 closed, HSGS closed. When the three-terminal single-pole metal return wire operates, the grounding point is formed by grounding the station internal grounding switch HSGS of the station C.
The control method for switching the operation of the three-terminal direct-current power transmission system from the single-pole earth return wire to the single-pole metal return wire comprises the following steps: station C closes the metallic return isolation switch Q71 to initiate the metallic return connection. After the metallic loop connection is started, station a and station B perform metallic loop connection operations, respectively, station a closes transfer switch MRS1, and station B closes transfer switch MRS 2. After the switches MRS1 and MRS2 are switched on, the station A and the station B respectively send MRS on-position signals to the opposite station. After receiving the on-position signals of MRS1 and MRS2, station A sends an opening control command to a metal return line change-over switch MRTB1 of the station after 3s time delay; after receiving the on-bit signals of MRS1 and MRS2, station B sends an open-circuit control command to metallic return line changeover switch MRTB2 of its own station after 3s time delay.
In one embodiment, if after the switches MRS1 and MRS2 are closed, the metallic return currents IdL _ op1 and IdL _ op2 flowing through the station a and the station B are both greater than a threshold value, the MRTB switch is not triggered to prohibit the opening logic, and the MRTB1 and the MRTB2 realize simultaneous opening after receiving the opening control command.
It should be noted that, in actual engineering, when there may be a communication delay between the station a and the station B, it needs an inter-station communication time of about 100ms, and in this case, the switches MRTB1 and MRTB2 can still ensure that the opening is realized within 500 ms. Because the switching-off time interval is as small as microsecond level and can be ignored, the beneficial effect that after the switch MRTB of a certain transmitting end converter station is switched off in one step, the current of the metal return wire of the other transmitting end converter station becomes smaller than the preset current value under certain current level combination can still be avoided, and the MRTB forbids switching-off logic is triggered.
In another embodiment, if the switches MRS1 and MRS2 are switched on, then the ground return wire and the metal return wire in the three-terminal dc power transmission system exist at the same time, and under some current level combinations of the station a and the station B, the current IdL _ op of the metal return wire flowing through the station a or the station B is smaller than a preset current value and does not satisfy the switching-off condition, and the MRTB disables the switching-off logic. However, in this case, there is no situation that A, B two stations prohibit the MRTB at the same time, so, assuming that the station a does not satisfy the opening condition and the station B satisfies the opening condition at this time, the station B sends an opening control command to the switch MRTB2 after receiving the closing signals of MRS1 and MRS2, the switch MRTB2 satisfies the opening condition, the current between the converter stations in the three-terminal system is transferred, the metal loop current IdL _ op1 flowing through the station a is greater than the preset current value, the MRTB prohibits the opening logic from returning, and the switch MRTB1 is opened.
After receiving the branch signals of the switches MRTB1 and MRTB2, the station internal grounding switch HSGS of the station C is closed, the ground return isolation disconnecting link Q5 is opened, the three-station unipolar metal return appears, and the process of converting the unipolar ground into the unipolar metal return is completed.
In the method for controlling a single-pole ground return wire to a metal return wire provided by the second embodiment of the present invention, after the connection of the metal return wires is started, each sending end converter station controls a ground return wire change-over switch MRS of the local station to be closed; after detecting that a switch MRS of each sending end converter station is closed, each sending end converter station sends an MRS on-position signal to other sending end converter stations; after receiving MRS (signal to switching System) on-position signals of all the sending end converter stations, each sending end converter station synchronously sends an opening control instruction to a metal return line change-over switch MRTB of the station; and after receiving the opening control instruction, the metal loop transfer switch MRTB is immediately disconnected when judging that the current of the metal loop flowing through the station is larger than a preset current value. When the current of the metal return wire flowing through the station is judged to be less than or equal to the preset current value, the closed state is kept; and the metal return wire is disconnected when the current of the metal return wire is judged to be larger than the preset current value. In the process of converting the ground return wire of the multi-terminal direct current transmission system into the metal return wire, after each sending terminal converter station controls the switch MRS of the station to be closed, the switch MRTB is synchronously sent with a brake-separating control instruction after MRS on-bit signals sent by all sending terminal circulating current stations are received. By increasing the interactive communication among the transmitting end converter stations, the simultaneous opening of the switch MRTB is realized, the condition that the metal return wire conversion fails due to the fact that the MRTB is triggered to prohibit the opening logic can be effectively avoided, and the operation reliability of the multi-end direct current system is improved.
Fig. 5 is a schematic structural diagram of a control device for converting a single-pole ground return wire into a metallic return wire according to a third embodiment of the present invention. A third embodiment of the present invention provides a control apparatus 30 for a single-pole ground return wire to metal return wire, which includes a processor 31, a memory 32, and a computer program stored in the memory and configured to be executed by the processor, and when the processor executes the computer program, the processor implements the control method for a single-pole ground return wire to metal return wire according to the first embodiment or the second embodiment.
It should be noted that, the control device for converting a single-pole ground return wire into a metal return wire according to the embodiment of the present invention is used for executing all the process steps of the control method for converting a single-pole ground return wire into a metal return wire according to the embodiment, and the working principles and beneficial effects of the two are in one-to-one correspondence, so that details are not described again.
An embodiment of the present invention further provides a computer-readable storage medium, where the computer-readable storage medium includes a stored computer program, where when the computer program runs, the apparatus where the computer-readable storage medium is located is controlled to perform the method for controlling a unipolar earth return wire to a metal return wire according to the first embodiment or the second embodiment.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-only memory (ROM), a Random Access Memory (RAM), or the like.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.
Claims (9)
1. A control method for converting a single-pole ground return wire into a metal return wire is suitable for a multi-terminal direct-current power transmission system and is characterized by comprising the following steps:
after the metal return wire connection is started, each sending end converter station controls a ground return wire change-over switch MRS of the station to be closed;
after detecting that a switch MRS of each sending end converter station is closed, each sending end converter station sends an MRS on-position signal to other sending end converter stations;
after receiving MRS (signal to plate) on-position signals of all the sending end converter stations and after a preset time delay, each sending end converter station synchronously sends a brake-separating control command to a metal return line change-over switch MRTB of the station;
and after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be larger than a preset current value, the metal loop change-over switch MRTB is immediately switched off.
2. A method of monopole earth return to metal return control as claimed in claim 1 wherein said method of monopole earth return to metal return control further comprises the steps of:
after each metal loop change-over switch MRTB receives the switching-off control instruction, when the current of the metal loop flowing through the station is judged to be less than or equal to the preset current value, the metal loop change-over switch MRTB keeps a closed state; and the metal return wire is disconnected when the current of the metal return wire is judged to be larger than the preset current value.
3. The method for controlling a single-pole ground return to metal return of claim 1, wherein before each sending end converter station separately controls the ground return change-over switch MRS of its own station to close, the method further comprises the steps of:
and closing a metal loop isolation disconnecting link in the receiving end converter station control station to start metal loop connection.
4. A method of monopole earth return to metal return control as claimed in claim 2 wherein said method of monopole earth return to metal return control further comprises the steps of:
each transmitting end converter station sends MRTB sub-position signals to a receiving end converter station after detecting that a switch MRTB of the transmitting end converter station is disconnected;
and after the receiving end converter station receives the MRTB sub-bit signals of all the transmitting end converter stations, the grounding switch in the station is controlled to be closed.
5. A method of monopole earth return to metal return control as claimed in claim 4 wherein said method of monopole earth return to metal return control further comprises the steps of:
and after receiving the MRTB branch signals of all the transmitting end converter stations, the receiving end converter station controls the isolation disconnecting link of the earth return line to be disconnected.
6. A method for control of a unipolar earth return wire to a metal return wire according to any one of claims 1 to 5, wherein said predetermined current value is 20A.
7. A method for monopole earth return to metal return control as claimed in claim 1 wherein said predetermined time delay is 3 s.
8. A control apparatus for a unipolar earth return to metal return, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, the processor when executing the computer program implementing a method of controlling a unipolar earth return to metal return as claimed in any one of claims 1 to 7.
9. A computer-readable storage medium, comprising a stored computer program, wherein the computer program, when executed, controls an apparatus in which the computer-readable storage medium is located to perform the method of controlling a unipolar earth return wire to a metal return wire of any one of claims 1 to 7.
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| CN112366675B (en) * | 2020-10-30 | 2022-12-09 | 中国南方电网有限责任公司超高压输电公司 | Method for controlling conversion switch of parallel three-terminal direct current field |
| CN113555858B (en) * | 2021-07-28 | 2022-08-16 | 中国南方电网有限责任公司超高压输电公司昆明局 | Control method, device and protection system for direct current power transmission system under metal return wire |
| CN113437806B (en) * | 2021-08-27 | 2021-12-03 | 中国南方电网有限责任公司超高压输电公司广州局 | Method and device for controlling opening of metal loop switch and computer equipment |
| CN114336717B (en) * | 2021-12-02 | 2023-10-17 | 南方电网科学研究院有限责任公司 | Multi-terminal direct current transmission system converter station wiring and control method, equipment and medium |
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