CN113629749A - Single-station exiting method and device of multi-terminal direct-current power transmission system - Google Patents
Single-station exiting method and device of multi-terminal direct-current power transmission system Download PDFInfo
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- CN113629749A CN113629749A CN202010386989.XA CN202010386989A CN113629749A CN 113629749 A CN113629749 A CN 113629749A CN 202010386989 A CN202010386989 A CN 202010386989A CN 113629749 A CN113629749 A CN 113629749A
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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
- H02H7/268—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]
Abstract
The invention discloses a single-station exit method of a multi-terminal direct-current transmission system.A control and protection system of a converter station locks a converter of a station to be exited and trips an alternating-current side switch after receiving a station exit instruction; locking the direct current power control station; locking the direct-current voltage control station; detecting the current flowing through the circuit breaker of the station to be exited, and issuing a circuit breaker opening command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all converter stations are locked; after the breaker is tripped, performing direct-current side pole isolation on the station to be exited; re-unlocking the direct-current voltage control station and controlling the direct-current voltage to a normal value; and unlocking the direct current power control station again and controlling the direct current power to a normal value. The technical scheme provided by the application ensures that the circuit breaker is separated when the current flowing through the circuit breaker is basically zero, and the high-voltage circuit breaker with low cost and simple structure can be selected in the rear multi-terminal direct-current transmission project, so that the construction cost is effectively reduced, and the reliability and flexibility of system operation are improved.
Description
Technical Field
The invention relates to the field of direct current transmission, in particular to a single-station quitting method and a single-station quitting device of a multi-terminal direct current transmission system.
Background
In the application of multi-terminal direct current transmission, if a single station has an intra-area fault or needs to be overhauled, the optimal mode is to withdraw the station on line and keep other stations running continuously.
One way is to add a direct current breaker with strong current breaking capacity between the converter station and a direct current line, and quickly isolate the fault station through the direct current breaker. However, the dc circuit breaker has high cost, large floor space, complex structure and reduced reliability. Under the prior art, with the rise of voltage class, the cost and the difficulty of the direct current breaker almost increase exponentially, and the direct current breaker can hardly be applied to extra-high voltage occasions.
The other way is to adopt the high-voltage circuit breaker reformed by the conventional alternating-current circuit breaker, has simple structure and low cost, and is almost suitable for any voltage grade. But the capacity of breaking direct current is very limited, and even only dozens of amperes is achieved in extra-high voltage occasions. Therefore, the high-voltage circuit breaker cannot directly and rapidly isolate a fault station, and the current can be reliably isolated only by controlling the current to be below the breaking current by a control and protection system.
In consideration of economy and reliability, the use of a high-voltage circuit breaker to realize online exit of a converter station in an extra-high voltage application is the only choice in the prior art. The generally transmitted power of the extra-high voltage project is very high, and the power fluctuation caused in the station returning process has a large influence on the stable operation of the system, so that the station returning strategy needs to be matched with stable control, generally, the shorter the time of the power from one stable state to another stable state is, the better the station returning process is, the shorter the station returning process is. For some distribution network projects or projects with limited cost, the scheme of the high-voltage circuit breaker is also an effective measure for reducing the cost. Therefore, a single station exit strategy for multi-terminal direct current transmission based on a high-voltage circuit breaker needs to be researched to ensure that the converter station can be reliably isolated and the station exit process is short.
Disclosure of Invention
The invention aims to provide a single-station exit method and a single-station exit device of a multi-terminal direct-current transmission system, solves the problem of reliable and quick breaking of a high-voltage circuit breaker, and is suitable for multi-terminal direct-current transmission engineering.
In order to achieve the above purpose, the solution of the invention is:
in a first aspect, the invention provides a single-station exiting method for a multi-terminal direct-current transmission system, where the multi-terminal direct-current transmission system at least includes three converter stations, one of the converter stations is a direct-current voltage control station, and the other converter stations are direct-current power control stations, and the converter stations are connected by a direct-current line; at least one circuit breaker is arranged between the converter station to be withdrawn and the direct current line; the single-station exiting method comprises the following steps:
after receiving the station quitting instruction, the converter station control protection system locks a converter of the station to be quitted and trips an AC side switch;
locking the direct current power control station;
locking the direct-current voltage control station;
detecting the current flowing through the circuit breaker of the station to be exited, and issuing a circuit breaker opening command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all converter stations are locked;
and after the circuit breaker is tripped, the station to be exited executes the isolation of the direct current side pole, unlocks the direct current voltage control station again and controls the direct current voltage to a normal value, unlocks the direct current power control station again and controls the direct current power to a normal value.
Preferably, the blocking dc power control station includes: and after the direct current power is reduced to zero according to a certain slope by the direct current power control station, the direct current power control station is locked.
Preferably, the blocking dc power control station includes: and detecting the current direct current power or current, directly locking the direct current power control station when the current direct current power or current is lower than a set power or current locking threshold, otherwise, firstly controlling the direct current power to the locking threshold and then locking the direct current power control station.
Preferably, if the station to be exited is a dc voltage control station, after the converter of the station to be exited is locked and the ac side switch is tripped, one of the original dc power control stations takes over the dc voltage control to be a new dc voltage control station.
Preferably, the phase shift can be performed without latching if the converter valves not exiting the dc power control station are thyristor converter valves.
Preferably, the step of locking the dc voltage control station comprises: and the direct-current voltage control station is locked after the direct-current voltage is controlled to be zero by the direct-current voltage control station.
Preferably, the latching dc voltage control station further comprises: and detecting the direction and the amplitude of the direct current voltage control station, directly locking the direct current voltage control station if the direction of the direct current is detected to point to the direct current circuit and the amplitude is higher than an overcurrent threshold value, otherwise, controlling the direct current voltage to be zero and then locking the direct current voltage control station.
Preferably, the step of controlling the dc power to a normal value includes: and after the direct current power control station is unlocked, the direct current power is firstly controlled to be zero, and after the voltage of the direct current line is higher than a preset voltage threshold value, the direct current power is controlled to be a normal value.
Preferably, the method further comprises: when the current flowing through the circuit breaker at the station to be exited is detected, if the current is higher than a preset breaking threshold value and the duration time exceeds the power interruption allowable time, or the circuit breaker is not successfully tripped, the station to be exited fails, and the alternating-current side switches of other stations are tripped.
Preferably, if the station to be exited has a communication fault with other stations, only the station to be exited participates in operation, and other stations do not participate in operation; after receiving a station quitting instruction, locking a current converter of the station to be quitted and tripping an AC side switch; and after the station to be exited finishes locking and tripping the alternating current switch, directly detecting the current flowing through the circuit breaker, when the current is lower than a breaking threshold value and continuously exceeds a second preset time fixed value, the circuit breaker is switched off, and after the circuit breaker is tripped, performing direct current side pole isolation.
In a second aspect, the invention provides a single-station exit device of a multi-terminal direct-current transmission system, where the multi-terminal direct-current transmission system at least includes three converter stations, one of the converter stations is a direct-current voltage control station, and the other converter stations are direct-current power control stations, and the converter stations are connected by a direct-current line; at least one circuit breaker is arranged between the converter station to be withdrawn and the direct current line; characterized in that said single station exit device comprises:
a to-exit station locking unit: the system comprises a power supply, a converter, a tripping AC side switch, a power supply control circuit and a power supply control circuit, wherein the power supply is used for receiving a station quitting instruction and locking the converter of a station to be quitted and tripping the AC side switch;
normal station lockout unit: the DC power control station is used for locking the DC power control station and the DC voltage control station;
breaker opening unit: the system comprises a detection unit, a switching-off unit and a switching-off unit, wherein the detection unit is used for detecting the current flowing through a circuit breaker of a station to be exited, and issuing a circuit breaker switching-off command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all converter stations are locked;
isolation and unlocking unit: the direct current side pole isolation control system is used for detecting the state of the circuit breaker, executing direct current side pole isolation at a station to be exited after the circuit breaker is confirmed to be tripped, re-unlocking the direct current voltage control station and controlling the direct current voltage to a normal value, and re-unlocking the direct current power control station and controlling the direct current power to a normal value.
Preferably, the blocking dc power control station in the normal station blocking unit includes: and after the direct current power is reduced to zero according to a certain slope by the direct current power control station, the direct current power control station is locked.
Preferably, the blocking dc power control station in the normal station blocking unit includes: and detecting the current direct current power or current, directly locking the direct current power control station when the current direct current power or current is lower than a set power or current locking threshold, otherwise, firstly controlling the direct current power to the locking threshold and then locking the direct current power control station.
Preferably, in the locking unit of the station to be exited, if the station to be exited is a dc voltage control station, after locking the converter of the station to be exited and tripping the ac side switch, an original dc power control station is controlled to take over the dc voltage control to form a new dc voltage control station.
Preferably, the phase shift can be performed without latching if the converter valves not exiting the dc power control station are thyristor converter valves.
Preferably, the blocking dc voltage control station in the normal station blocking unit includes: and the direct-current voltage control station is locked after the direct-current voltage is controlled to be zero by the direct-current voltage control station.
Preferably, in the normal station blocking unit, before blocking the dc voltage control station, the normal station blocking unit further includes: and detecting the direction and the amplitude of the direct current voltage control station, directly locking the direct current voltage control station if the direction of the direct current is detected to point to the direct current circuit and the amplitude is higher than an overcurrent threshold value, otherwise, controlling the direct current voltage to be zero and then locking the direct current voltage control station.
Preferably, in the isolating and unlocking unit, controlling the dc power to a normal value includes: and after the direct current power control station is unlocked, the direct current power is firstly controlled to be zero, and after the voltage of the direct current line is higher than a preset voltage threshold value, the direct current power is controlled to be a normal value.
After the scheme is adopted, the circuit breaker is arranged between the converter stations and the direct current line, and the circuit breaker is in a non-voltage and non-current state in a mode of momentarily reducing the voltage of the direct current line to zero and locking all the converter stations, so that the circuit breaker is disconnected when the current flowing through the circuit breaker is basically zero; and after the circuit breaker is tripped, the circuit breaker is unlocked again and the direct current power is controlled to be a normal value when the circuit breaker does not quit standing, so that the system power suspension time caused in the whole process is short, and the requirement of stable operation of the system can be met. When the fault point may cause the equipment of the non-exit station to be over-current, the direct current reverse current pre-judgment criterion is adopted to accelerate the locking process, so that the protection action of the non-exit station is avoided. By adopting the invention, the high-voltage circuit breaker with low cost and simple structure can be selected in the rear multi-terminal direct-current transmission project, the construction cost is effectively reduced, and the reliability and flexibility of the system operation are improved.
Drawings
FIG. 1 is a schematic main wiring diagram of a three terminal DC embodiment of the present invention;
FIG. 2 is a basic flow diagram of a single station exit method of the present invention;
FIG. 3 is a flow chart of a station quitting method of a DC voltage control station according to the present invention;
FIG. 4 is a flow chart of a DC control station accelerated lock method of the present invention;
FIG. 5 is a flow chart of a multi-power station power recovery method of the present invention;
FIG. 6 is a flow chart of a method for backing off a station in case of a communication failure according to the present invention;
FIG. 7 is a schematic view of the multi-port DC single station exit device of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The single-station exiting method is suitable for a multi-terminal direct-current power transmission system and comprises multi-terminal conventional direct current, multi-terminal flexible direct current and multi-terminal mixed direct current. The multi-terminal direct current transmission system at least comprises three converter stations, wherein one converter station is a direct current voltage control station, the other converter stations are direct current power control stations, and all the converter stations are connected to a direct current circuit; at least one circuit breaker is arranged between the exit converter station and the direct current line. Fig. 1 is an embodiment of three-terminal direct current, direct current sides of three converter stations are all connected to a positive electrode line 11 and a negative electrode line 12, a breaker 13 is not configured for a converter station 1, one converter station 2 is configured, and two converter stations 3 are configured, and the converter stations 2 and 3 have the implementation conditions of the single-station exit method provided by the scheme.
The invention provides a first embodiment of a single-station exiting method of a multi-terminal direct-current power transmission system, which is shown in figure 2 and comprises the following steps:
Specifically, if the station returning command is manually issued, an operator can be required to manually reduce the power of the station to the minimum for issuing or the control system automatically controls the power to the minimum and then locks the station after issuing; and if the station quitting command is protection issuing, directly locking the current converter of the station to be quitted.
Specifically, after the dc power is reduced to zero by the dc power control station according to a certain slope, the dc power control station is locked.
In a preferred embodiment, the current dc power or current is detected, and when the current dc power or current is lower than a set power or current blocking threshold, the dc power control station is directly blocked, otherwise, the dc power is controlled to the blocking threshold before the dc power control station is blocked. In order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
And step 203, locking the direct current voltage control station.
Specifically, the direct-current voltage control station controls the direct-current voltage to be reduced to zero according to a certain slope and then locks the current converter; in order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
specifically, the breaking threshold is set according to the opening current allowed by the circuit breaker, the target is a low-cost high-voltage circuit breaker, the opening current is small, and the threshold needs to fully consider the influence of measurement precision and leave a proper margin; in order to shorten this process, the first predetermined time is as small as possible, but is at least greater than or equal to half of the period of the frequency of the ac system.
And step 205, detecting that the circuit breaker to be exited is separated.
Specifically, for a converter station configured with only one circuit breaker, only the position of the circuit breaker is detected; for a converter station equipped with two circuit breakers, it is desirable to detect that both circuit breakers are equally positioned.
And step 206, performing direct current side pole isolation on the station to be exited.
Specifically, after the circuit breaker connected between the exit station and the direct current line is separated, the direct current side pole is further isolated, so that the direct current side pole is reliably disconnected from the direct current line. Pole isolation requires that at least one isolation switch is separate between the inverter and the positive dc line and at least one isolation switch is separate between the inverter and the negative dc line.
And step 207, unlocking the direct-current voltage control station again and controlling the direct-current voltage to a normal value.
Specifically, after the exit station is separated from the breaker connected between the direct current lines, the direct current voltage control station unlocks again and controls the direct current voltage to rise to a normal value according to a certain slope; in order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
And step 208, unlocking the direct current power control station again and controlling the direct current power to a normal value.
Specifically, after the exit station is separated from the breaker connected between the direct current lines, the direct current power control station unlocks again and controls the direct current power to rise to a normal value according to a certain slope; in order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
When the multi-terminal direct-current transmission project operates, only one direct-current voltage control station is generally arranged, and the operating direct-current power control station can have a certain takeover sequence for direct-current voltage control. As shown in fig. 3, another embodiment of the single station exiting method of the multi-terminal dc power transmission system adjusts, on the basis of the first embodiment, steps 201 to 203 of the embodiment to the following steps:
and 301, the direct current voltage control station to be quitted receives a station quitting instruction, and the current converter and the AC side switch are locked.
Specifically, if the station quitting command is manually issued, an operator can be required to manually or automatically adjust the power instruction of the power control station by a program, and the power of the station to be quitted is controlled to be minimum and then locked; and if the station quitting command is protection issuing, directly locking the current converter of the station to be quitted.
And step 302, taking over the direct current voltage control by one of the direct current power control stations according to a preset sequence.
Specifically, the running direct current power control station takes over the direct current voltage control immediately when the original direct current voltage control station is locked according to a preset direct current voltage control take-over sequence, and becomes a new direct current voltage control station.
And step 303, the rest direct current power control stations control the direct current power to be zero and then lock.
Specifically, after the remaining dc power control stations reduce the dc power to zero according to a certain slope, the dc power control stations are locked.
In a preferred embodiment, the dc power or current of the remaining dc power control stations is detected, and when the detected dc power or current is lower than a set power or current blocking threshold, the dc power control station is directly blocked, otherwise, the dc power is controlled to the blocking threshold before the dc power control station is blocked. In order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
And step 304, the new direct current voltage control station locks after controlling the direct current voltage to be zero.
Specifically, the new direct-current voltage control station controls the direct-current voltage to be reduced to zero according to a certain slope and then locks the current converter; in order to shorten the process, the slope is preferably as fast as possible without affecting the control performance.
In a preferred embodiment, on the basis of the aforementioned single station exiting method embodiment of the multi-terminal dc power transmission system, when the multi-terminal dc power transmission system is a hybrid dc, if the converter valve that does not exit the dc power control station is a thyristor converter valve, only phase shifting may be performed without locking.
In yet another embodiment of a single station quitting method of a multi-terminal direct-current transmission system, the process of locking a direct-current voltage control station can be accelerated for fault quitting of a pole bus and the like which affect a direct-current side. As shown in fig. 4, on the basis of the first embodiment, step 203 is adjusted to the following steps:
And step 404, directly locking the inverter.
Specifically, the preset current threshold needs to be smaller than the endurance capacity of the dc bus and ensure that a fault exiting the station does not cause any protective action of the normal dc voltage control station.
In the aforementioned single-station exiting method for the multi-terminal dc power transmission system, after the fault station circuit breaker is positioned, the other converter stations will recover the dc voltage or the dc power, as shown in fig. 5, according to another embodiment of the single-station exiting method for the multi-terminal dc power transmission system, on the basis of the first embodiment, step 208 of the first embodiment is adjusted as follows:
and step 501, the direct current power control station receives the branch position of the circuit breaker of the exit station.
Specifically, for a current converter adopting a full-control device, the controllable zero power can be unlocked; for converters employing thyristors, the phase shift is still maintained.
Specifically, the preset voltage threshold may be set according to the type of the converter and the power instruction of the converter station: if the rectifier station is arranged lower and the inverter station is arranged higher, the direct-current voltage establishing process can be accelerated; the converter station setting using thyristor converter valves is lower, accelerating the current build-up process.
In a preferred embodiment, on the basis of the first single-station exiting method embodiment of the multi-terminal dc power transmission system, if the condition that the current of the circuit breaker does not meet the condition exceeds the power interruption allowance time or the circuit breaker is not successfully tripped, the station exiting fails, and other stations are notified to trip the ac side switch.
In another embodiment of the single station exiting method of the multi-terminal direct-current power transmission system, if communication between exiting stations fails, other stations cannot receive an exiting signal, and cannot lock and restart. For the fault affecting the direct current side, other stations carry out corresponding operation according to the protection action condition of the other stations; for faults that do not affect the dc side, the fault station may be isolated. As shown in fig. 6, a method for station quitting under communication failure includes the following steps:
and 601, under the condition of communication faults with other stations, receiving a station quitting instruction, and locking the station to be quitted and the AC side switch.
Specifically, because other stations are still running, the second preset time constant value is far larger than the first preset time constant value, and the problem that the current fluctuation flowing through the breaker exceeds the breaking threshold value to cause breaking failure is avoided.
And 603, detecting that the circuit breaker to be exited is separated, and issuing direct current side pole isolation.
After the scheme is adopted, the circuit breaker is arranged between the converter stations and the direct current line, and the circuit breaker is in a non-voltage and non-current state in a mode of momentarily reducing the voltage of the direct current line to zero and locking all the converter stations, so that the circuit breaker is disconnected when the current flowing through the circuit breaker is basically zero; and after the circuit breaker is tripped, the circuit breaker is unlocked again and the direct current power is controlled to be a normal value when the circuit breaker does not quit standing, so that the system power suspension time caused in the whole process is short, and the requirement of stable operation of the system can be met. When the fault point may cause the equipment of the non-exit station to be over-current, the direct current reverse current pre-judgment criterion is adopted to accelerate the locking process, so that the protection action of the non-exit station is avoided. By adopting the invention, the high-voltage circuit breaker with low cost and simple structure can be selected in the rear multi-terminal direct-current transmission project, the construction cost is effectively reduced, and the reliability and flexibility of the system operation are improved.
Fig. 7 shows an embodiment of a single station exit device of a multi-terminal dc power transmission system provided by the present invention, where the multi-terminal dc power transmission system at least includes three converter stations, one of the converter stations is a dc voltage control station, and the other converter stations are dc power control stations, and each converter station is connected through a dc line; at least one circuit breaker is arranged between the converter station to be withdrawn and the direct current line; the single-station exiting device comprises: the station locking unit to be exited, the normal station locking unit, the breaker opening unit and the breaker opening unit. Wherein:
a to-exit station locking unit: and the controller is used for locking the current converter of the station to be quitted and tripping the AC side switch after receiving the station quitting instruction.
Normal station lockout unit: for latching the dc power control station and latching the dc voltage control station.
Breaker opening unit: the system is used for detecting the current flowing through the circuit breaker of the station to be exited, and issuing a circuit breaker opening command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all the converter stations are locked.
Isolation and unlocking unit: the direct current side pole isolation control system is used for detecting the state of the circuit breaker, executing direct current side pole isolation at a station to be exited after the circuit breaker is confirmed to be tripped, re-unlocking the direct current voltage control station and controlling the direct current voltage to a normal value, and re-unlocking the direct current power control station and controlling the direct current power to a normal value.
In a preferred embodiment, based on the above apparatus embodiment, the latching dc power control station in the normal station latching unit includes: and after the direct current power is reduced to zero according to a certain slope by the direct current power control station, the direct current power control station is locked.
In a preferred embodiment, based on the above apparatus embodiment, the latching dc power control station in the normal station latching unit includes: and detecting the current direct current power or current, directly locking the direct current power control station when the current direct current power or current is lower than a set power or current locking threshold, otherwise, firstly controlling the direct current power to the locking threshold and then locking the direct current power control station.
In a preferred embodiment, based on the above device embodiment, in the locking unit for the station to be exited, if the station to be exited is a dc voltage control station, after locking the converter of the station to be exited and tripping the ac-side switch, an original dc power control station is controlled to take over the dc voltage to form a new dc voltage control station.
In a preferred embodiment, based on the above-described embodiment of the apparatus, the phase shifting may be performed without blocking if the converter valves not exiting the dc power control station are thyristor converter valves.
In a preferred embodiment, on the basis of the above apparatus embodiment, the latching dc voltage control station in the normal station latching unit includes: and the direct-current voltage control station is locked after the direct-current voltage is controlled to be zero by the direct-current voltage control station.
In a preferred embodiment, on the basis of the above device embodiment, the normal station locking unit further includes, before locking the dc voltage control station: and detecting the direction and the amplitude of the direct current voltage control station, directly locking the direct current voltage control station if the direction of the direct current is detected to point to the direct current circuit and the amplitude is higher than an overcurrent threshold value, otherwise, controlling the direct current voltage to be zero and then locking the direct current voltage control station.
In a preferred embodiment, based on the above device embodiment, the controlling the dc power to a normal value in the isolating and unlocking unit includes: and after the direct current power control station is unlocked, the direct current power is firstly controlled to be zero, and after the voltage of the direct current line is higher than a preset voltage threshold value, the direct current power is controlled to be a normal value.
Finally, it should be noted that: the technical solutions of the present invention are only illustrated in conjunction with the above-mentioned embodiments, and not limited thereto. Those of ordinary skill in the art will understand that: modifications and equivalents may be made to the embodiments of the invention by those skilled in the art, which modifications and equivalents are within the scope of the claims appended hereto.
Claims (18)
1. A single-station exiting method of a multi-terminal direct-current transmission system at least comprises three converter stations, wherein one converter station is a direct-current voltage control station, the other converter stations are direct-current power control stations, and the converter stations are connected through a direct-current line; at least one circuit breaker is arranged between the converter station to be withdrawn and the direct current line; the single-station exiting method is characterized by comprising the following steps:
after receiving the station quitting instruction, the converter station control protection system locks a converter of the station to be quitted and trips an AC side switch;
locking the direct current power control station;
locking the direct-current voltage control station;
detecting the current flowing through the circuit breaker of the station to be exited, and issuing a circuit breaker opening command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all converter stations are locked;
and after the circuit breaker is tripped, the station to be exited executes the isolation of the direct current side pole, unlocks the direct current voltage control station again and controls the direct current voltage to a normal value, unlocks the direct current power control station again and controls the direct current power to a normal value.
2. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: the latching dc power control station includes: and after the direct current power is reduced to zero according to a certain slope by the direct current power control station, the direct current power control station is locked.
3. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: the latching dc power control station includes: and detecting the current direct current power or current, directly locking the direct current power control station when the current direct current power or current is lower than a set power or current locking threshold, otherwise, firstly controlling the direct current power to the locking threshold and then locking the direct current power control station.
4. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: if the station to be withdrawn is a direct-current voltage control station, after the converter of the station to be withdrawn is locked and the switch at the alternating-current side is tripped, one of the original direct-current power control stations takes over the direct-current voltage to form a new direct-current voltage control station.
5. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: if the converter valve not exiting the DC power control station is a thyristor converter valve, only phase shifting can be carried out without locking.
6. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: the step of latching the dc voltage control station comprises: and the direct-current voltage control station is locked after the direct-current voltage is controlled to be zero by the direct-current voltage control station.
7. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: the latching direct-current voltage control station also comprises the following steps: and detecting the direction and the amplitude of the direct current voltage control station, directly locking the direct current voltage control station if the direction of the direct current is detected to point to the direct current circuit and the amplitude is higher than an overcurrent threshold value, otherwise, controlling the direct current voltage to be zero and then locking the direct current voltage control station.
8. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: the step of controlling the direct current power to a normal value comprises the following steps: and after the direct current power control station is unlocked, the direct current power is firstly controlled to be zero, and after the voltage of the direct current line is higher than a preset voltage threshold value, the direct current power is controlled to be a normal value.
9. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: further comprising: when the current flowing through the circuit breaker at the station to be exited is detected, if the current is higher than a preset breaking threshold value and the duration time exceeds the power interruption allowable time, or the circuit breaker is not successfully tripped, the station to be exited fails, and the alternating-current side switches of other stations are tripped.
10. A single station pull-out method of a multi-terminal dc transmission system according to claim 1, characterized by: if the station to be exited has communication faults with other stations, only the station to be exited participates in operation, and other stations do not participate in operation; after receiving a station quitting instruction, locking a current converter of the station to be quitted and tripping an AC side switch; and after the station to be exited finishes locking and tripping the alternating current switch, directly detecting the current flowing through the circuit breaker, when the current is lower than a breaking threshold value and continuously exceeds a second preset time fixed value, the circuit breaker is switched off, and after the circuit breaker is tripped, performing direct current side pole isolation.
11. A single-station exit device of a multi-terminal direct-current transmission system at least comprises three converter stations, wherein one converter station is a direct-current voltage control station, the other converter stations are direct-current power control stations, and the converter stations are connected through a direct-current circuit; at least one circuit breaker is arranged between the converter station to be withdrawn and the direct current line; characterized in that said single station exit device comprises:
a to-exit station locking unit: the system comprises a power supply, a converter, a tripping AC side switch, a power supply control circuit and a power supply control circuit, wherein the power supply is used for receiving a station quitting instruction and locking the converter of a station to be quitted and tripping the AC side switch;
normal station lockout unit: the DC power control station is used for locking the DC power control station and the DC voltage control station;
breaker opening unit: the system comprises a detection unit, a switching-off unit and a switching-off unit, wherein the detection unit is used for detecting the current flowing through a circuit breaker of a station to be exited, and issuing a circuit breaker switching-off command when the current is lower than a preset breaking threshold value and continuously exceeds a first preset time set value and all converter stations are locked;
isolation and unlocking unit: the direct current side pole isolation control system is used for detecting the state of the circuit breaker, executing direct current side pole isolation at a station to be exited after the circuit breaker is confirmed to be tripped, re-unlocking the direct current voltage control station and controlling the direct current voltage to a normal value, and re-unlocking the direct current power control station and controlling the direct current power to a normal value.
12. A single station withdrawl device for a multi-terminal direct current transmission system according to claim 11, characterized in that: the blocking dc power control station in the normal station blocking unit includes: and after the direct current power is reduced to zero according to a certain slope by the direct current power control station, the direct current power control station is locked.
13. A single station withdrawl device for a multi-terminal direct current transmission system according to claim 11, characterized in that: the blocking dc power control station in the normal station blocking unit includes: and detecting the current direct current power or current, directly locking the direct current power control station when the current direct current power or current is lower than a set power or current locking threshold, otherwise, firstly controlling the direct current power to the locking threshold and then locking the direct current power control station.
14. A single station withdrawl device for a multi-terminal direct current transmission system according to claim 11, characterized in that: in the locking unit of the station to be withdrawn, if the station to be withdrawn is a direct-current voltage control station, after a current converter of the station to be withdrawn is locked and an alternating-current side switch is tripped, an original direct-current power control station is controlled to take over the direct-current voltage to form a new direct-current voltage control station.
15. A single station pull-out method for a multi-terminal dc power transmission system according to claim 11, wherein: if the converter valve not exiting the DC power control station is a thyristor converter valve, only phase shifting can be carried out without locking.
16. A single station pull-out method for a multi-terminal dc power transmission system according to claim 11, wherein: the blocking dc voltage control station in the normal station blocking unit includes: and the direct-current voltage control station is locked after the direct-current voltage is controlled to be zero by the direct-current voltage control station.
17. A single station withdrawl device for a multi-terminal direct current transmission system according to claim 11, characterized in that: in the normal station locking unit, before locking the dc voltage control station, the normal station locking unit further includes: and detecting the direction and the amplitude of the direct current voltage control station, directly locking the direct current voltage control station if the direction of the direct current is detected to point to the direct current circuit and the amplitude is higher than an overcurrent threshold value, otherwise, controlling the direct current voltage to be zero and then locking the direct current voltage control station.
18. A single station withdrawl device for a multi-terminal direct current transmission system according to claim 11, characterized in that: in the isolation and unlock unit, controlling the dc power to a normal value includes: and after the direct current power control station is unlocked, the direct current power is firstly controlled to be zero, and after the voltage of the direct current line is higher than a preset voltage threshold value, the direct current power is controlled to be a normal value.
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| WO2015090100A1 (en) * | 2013-12-16 | 2015-06-25 | 国家电网公司 | On-line deblocking and blocking control method for extra-high voltage direct current transmission project converter |
| WO2016056274A1 (en) * | 2014-10-09 | 2016-04-14 | 三菱電機株式会社 | Dc circuit breaker |
| CN108879625A (en) * | 2018-07-19 | 2018-11-23 | 南京南瑞继保电气有限公司 | A kind of parallel connection multiterminal extra-high voltage direct-current transmission valve unit protection action processing method |
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