CN110797900B - Method for quitting fault of three-terminal hybrid direct-current valve bank during inter-station communication fault - Google Patents
Method for quitting fault of three-terminal hybrid direct-current valve bank during inter-station communication fault 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
- H02H7/10—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 for converters; for rectifiers
- H02H7/12—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 for converters; for rectifiers for static converters or rectifiers
- H02H7/122—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 for converters; for rectifiers for static converters or rectifiers for inverters, i.e. dc/ac converters
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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
- H02H7/10—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 for converters; for rectifiers
- H02H7/12—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 for converters; for rectifiers for static converters or rectifiers
- H02H7/125—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 for converters; for rectifiers for static converters or rectifiers for rectifiers
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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 relates to the field of extra-high voltage multi-terminal hybrid direct-current transmission fault processing, in particular to a fault quitting method of a three-terminal hybrid direct-current valve bank during inter-station communication fault. A valves of rectification side LCC station breaks down and extremely shuts down the back, should ensure that contravariant side decides power VSC station extremely shutdown earlier, and contravariant side decides direct current voltage VSC station and stops down at last, just so can ensure that when each station withdraws from, direct current voltage can remain stable, avoids direct current system to take place the oscillation, and direct current system loses stably. Under the communication fault between the three terminals, when the valve group fault exits, the corresponding stations all adopt the extreme shutdown method, so that the protection action again caused by overvoltage on the non-fault valve group after the fault valve group is locked can be effectively avoided. The valve group fault of the LCC station can ensure that the inversion side fixed direct current power VSC station and the inversion side fixed direct current voltage VSC station are stably locked successively by adopting a low current locking method after the rectification side is extremely stopped, and the condition that the VSC station is out of control is effectively avoided.
Description
Technical Field
The invention relates to the field of extra-high voltage multi-terminal hybrid direct-current transmission fault processing, in particular to a fault quitting method of a three-terminal hybrid direct-current valve bank during inter-station communication fault.
Background
The ultra-high voltage three-terminal hybrid direct-current transmission technology is a new power technology, only one ultra-high voltage three-terminal hybrid direct-current transmission project in China is in construction in the world at present, and no ultra-high voltage three-terminal hybrid direct-current transmission project is put into operation.
In an extra-high voltage three-terminal hybrid direct-current transmission project, a transmitting terminal station S1 adopts a power grid commutation converter-based LCC-HVDC, and a receiving terminal station S2 and a receiving terminal station S3 adopt a hybrid direct-current transmission system which is based on a modular multilevel converter MMC-HVDC and operates in parallel at three terminals.
When the communication between stations is normal and the valve group is failed to exit, the converter station where the failed valve group is located can quickly transmit a valve group protection exit instruction to the other two stations, and the three stations can quickly and safely realize the protection exit of the valve group through the sequence control and the coordination of the voltage controller and the current controller.
Under the condition of communication faults between stations, data interaction between the three-terminal control protection systems cannot be carried out, and the original direct-current control protection function cannot finish the coordination quitting of the valve bank between the three stations. For a conventional LCC extra-high voltage three-terminal direct current system, when one converter station valve group fails to exit in inter-station communication failure, the other two stations respectively exit one valve group through direct current low voltage protection 27DC action under the regulation of respective voltage and current controllers. However, for mixed three-terminal direct current adopting LCC and MMC, after one valve bank of the LCC station at the rectification side is locked, the direct current voltage can still be controlled to be about 800kV by the inverter station fixed direct current voltage VSC station, and therefore the non-fault valve bank can not be overvoltage guaranteed only by actively stopping the operation electrode when the valve bank has a fault. For the valve group faults of the VSC station, the fault characteristics of the direct current system are different, the abnormal phenomena of direct current voltage, sudden change of direct current, long-time oscillation and the like easily occur, and even the whole direct current system is unstable. Therefore, the research on a valve group fault exit method under the condition of communication fault is a key technology and a difficulty of an extra-high voltage three-terminal hybrid direct current control protection system.
Disclosure of Invention
The invention aims to provide a method for quitting the fault of a three-terminal hybrid direct-current valve group during the inter-station communication fault, which can ensure that a current converter is safely quitted, and simultaneously control the influence on the direct-current operation within the minimum range, and ensure the safe and stable operation of a direct-current transmission system.
The embodiment of the invention is realized by the following steps:
a three-terminal hybrid direct-current valve group fault exit method during inter-station communication fault is disclosed, wherein a three-terminal hybrid direct-current transmission system comprises an LCC transmitting terminal station and two VSC receiving terminal stations; the two VSC receiving end stations are respectively a fixed direct-current voltage VSC receiving end station and a fixed direct-current power VSC receiving end station; the LCC sending terminal station comprises two LCC converter valve banks which are connected in series; the constant direct-current voltage VSC receiving end station and the constant direct-current power VSC receiving end station respectively comprise two MMC converter valve groups which are connected in series; the method is characterized in that: the following three valve group fault exit conditions are provided under the condition of communication fault between three stations:
A. when a valve bank fault exits at the LCC sending end station:
step 1: if the valve bank protection sends an emergency stop command, the failed valve bank immediately shifts the phase, and simultaneously sends a protective locking command to the other valve bank, and the other valve bank immediately shifts the phase after receiving the protective locking command of the valve bank; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
if the valve group protection sends a locking pulse command, the fault valve group is locked immediately, and simultaneously sends a protective locking command to the other valve group of the local pole, and the other valve group receives the protective locking command of the local valve group and immediately shifts the phase; the fault valve group converts the valve group protective locking trigger pulse command into an extreme emergency shutdown command, and the extreme emergency shutdown command is carried out after 20 ms;
step 2: after the LCC sending end station is extremely stopped, the voltage of a direct current port is reduced by the fixed direct current power VSC receiving end station; when the voltage of a port of a fixed direct-current voltage VSC receiving end station is larger than the voltage of a direct-current port of a fixed direct-current power VSC receiving end station, the fixed direct-current voltage VSC receiving end station sends back power to the fixed direct-current power VSC receiving end station;
and step 3: configuring a minimum direct current voltage reference value limit value UREF-MIN when communication faults of a fixed direct current power VSC receiving end station and the fixed direct current voltage VSC receiving end station occur, and configuring a maximum feedback power limit value PMAX of the fixed direct current voltage VSC receiving end station and the fixed direct current power VSC receiving end station;
and 4, step 4: setting minimum current locking logic of a constant direct-current voltage VSC receiving terminal; when the actual current of the VSC receiving terminal station with constant direct current power is less than I _ SET, the pole is stopped by the direct current low-current locking action after T1 is delayed, and the pole quitting is finished;
and 5: when the actual current of the VSC receiving terminal is less than I _ SET, the pole is stopped by the direct-current low-current locking action after T2 is delayed, and the pole quitting is finished;
B. when a valve bank fault of a fixed direct-current voltage VSC receiving end station exits:
step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;
step 2: if the valve group of the fixed direct current power VSC receiving end station does not have a fault, the direct current system is maintained in the constant current control of the LCC sending end station; determining the direct current power VSC receiving end station to continuously control the direct current power;
if the valve bank of the fixed direct current power VSC receiving end station fails; the fixed direct current power VSC receives a locking trigger pulse of the terminal station and simultaneously sends a zero pressure control instruction to enable the other valve group of the local pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;
and 4, step 4: c, the LCC sending end station stops running with low direct current, the LCC sending end station stops running with extreme, and the LCC sending end station stops running with three stations;
C. when a valve bank fault of a fixed direct current power VSC receiving end station exits:
step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;
step 2: if the valve group of the fixed direct-current voltage VSC receiving end station does not have a fault, the direct-current system is maintained in the constant current control of the LCC sending end station; the fixed direct-current voltage VSC receiving terminal station continuously controls the direct-current voltage;
if the valve bank of the fixed direct-current voltage VSC receiving end station fails; the constant direct-current voltage VSC receives a terminal station locking trigger pulse and simultaneously sends a zero pressure control instruction to enable the other valve group of the current pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value U _ LCC _ REF, and enabling the LCC sending end station to enter constant voltage control and run in no-load;
and 4, step 4: and C, the LCC sending end station stops running at low direct current, the LCC sending end station stops running at an extreme, and the LCC sending end station stops running at three stations.
Further, the setting range of the UREF _ MIN is 0.6-0.7 p.u.; the setting range of PMAX is 0.05-0.06 p.u.; the setting range of the I _ SET is 0.05-0.07 p.u.; the value range of T1 is 120-150 s, and the value of T2 is 0.5-1 s more than that of T1; the value range of U _ LCC _ REF is 1.03-1.04 p.u.
Further, I _ SET is 0.07 p.u.; t1 is 120 s; t2 was 120.5 s.
Further, when the poles of the two VSC receiving end stations are both stopped, the actual current value of the LCC sending end station is less than I _ SET, the poles are stopped by the direct-current low-current locking action after the delay time is 15-20 s, and the poles of the three stations are stopped.
Further, the MMC transverter valve bank is formed by mixing a half-bridge submodule and a full-bridge submodule, and the proportion of the full-bridge submodule and the half-bridge submodule is not lower than 50%.
Further, each converter valve group is provided with a bypass switch Q93, a bypass isolation knife switch Q3, an anode isolation switch Q2 and a cathode isolation switch Q1.
Further, each pole is provided with a pole bus isolating switch Q9 and a high-speed neutral bus switch HSNBS; the VSC receiving end station is also provided with a high-speed parallel switch HSS.
The invention has the beneficial effects that:
under the condition of communication failure among the three terminals, the invention provides that the extra-high voltage three-terminal hybrid direct-current series valve banks are all in an unlocked state, and when the valve banks fail to exit, the corresponding stations all adopt an extreme shutdown method, so that the problem that the non-failed valve banks are protected to act again due to overvoltage after the failed valve banks are locked can be effectively avoided. Meanwhile, aiming at the characteristics of the ultra-high voltage three-terminal mixed direct current, the invention designs a direct current low-current locking method which comprises the following steps: for the valve group fault of the rectification side LCC sending end station, after the rectification side pole is stopped, the inversion side fixed direct current power VSC receiving end station and the inversion side fixed direct current voltage VSC receiving end station can be ensured to be stably locked successively, and the condition that the VSC receiving end station is out of control is effectively avoided; meanwhile, after a valve group of a VSC receiving end station is extremely stopped due to fault, the other VSC receiving end station also has the working condition after the valve group is extremely stopped due to fault, the rectification side can be locked by low current, the LCC sending end station on the rectification side is prevented from long-time no-load operation, and the impact on the whole direct current system is reduced while the converter is guaranteed to safely exit.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram of a connection mode of a series connection double-valve-group extra-high voltage three-terminal hybrid direct-current power transmission system;
FIG. 2 is a circuit diagram of a transmitting LCC type converter 6 ripple converter;
fig. 3 is a detailed circuit diagram of the ripple converter of the transmitting-end LCC type converter 12;
fig. 4 is a simplified circuit diagram of a ripple converter of the transmitting-end LCC type converter 12;
FIG. 5 is a diagram of a receive-side hybrid MMC circuit configuration;
FIG. 6 is a schematic diagram of half-bridge sub-modules of a receive-side hybrid MMC circuit;
FIG. 7 is a schematic diagram of a full bridge sub-module of the receiving-side hybrid MMC circuit;
fig. 8 is a flowchart of a failure exit of a valve group of an LCC sending end station according to an embodiment of the present invention;
fig. 9 is a flowchart of a fault exit of a valve block of a constant direct-current voltage VSC receiving terminal according to an embodiment of the present invention;
fig. 10 is a flowchart of a failure exit of a constant dc power VSC receiving end station valve group according to an embodiment of the present invention;
fig. 11 is a schematic diagram of a VSC receiving terminal dc low current blocking logic according to an embodiment of the present invention;
fig. 12 is a schematic diagram of a low-current blocking logic of the LCC transmitting station according to an embodiment of the present invention.
Icon: the system comprises a 1-LCC sending end station, an 11-LCC converter valve bank, a 2-VSC receiving end station and a 21-MMC converter valve bank.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. 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.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
Example (b):
the embodiment provides a method for quitting a fault of a three-terminal hybrid direct-current valve bank during communication fault between stations, and a three-terminal hybrid direct-current transmission system comprises an LCC transmitting terminal station 1 and two VSC receiving terminal stations 2. The schematic structure of the three-terminal hybrid dc transmission system is shown in fig. 1. The LCC transmitting end station 1 is a rectifying station, and the VSC receiving end station 2 is an inverting station. The LCC sending terminal station 1 adopts an LCC type converter valve group 11, and the topological structure is shown in figures 2-4. The two VSC receiving end stations 2 both adopt MMC converter valve groups 22; the MMC converter valve block 22 is formed by mixing a Half-Bridge Sub-module (HBSM for short) and a Full-Bridge Sub-module (FBSM for short), and the proportion of the Full-Bridge Sub-module and the Half-Bridge Sub-module is generally not lower than 50%. The topology is shown in fig. 5-7.
To implement the throw-in and throw-out operation of the series valve banks, whether LCC or MCC type, each converter valve bank is configured with a bypass switch Q93, a bypass isolation knife switch Q3, an anode isolation switch Q2, and a cathode isolation switch Q1. To implement the isolation of the poles, a pole bus isolation switch Q9, a high speed neutral bus switch HSNBS, is provided for each pole. In order to implement the switching in and out of the pole (or station), the VSC receiver station is also provided with a high speed parallel switch HSS.
When an extra-high voltage three-terminal hybrid direct-current transmission project normally operates, a rectification side LCC sending end station controls direct-current power/direct current, a VSC receiving end station on an inversion side controls direct-current voltage (fixed direct-current voltage VSC receiving end station), and another VSC receiving end station on the inversion side controls direct-current power/direct current (fixed power VSC receiving end station), generally, the inversion side VSC receiving end station with large power capacity controls direct-current voltage, and the inversion side VSC receiving end station with small power capacity controls direct-current power/direct current.
The LCC sending terminal station comprises two LCC converter valve banks connected in series. The fixed direct-current voltage VSC receiving end station and the fixed direct-current power VSC receiving end station respectively comprise two serially connected MMC converter valve banks.
Aiming at valve bank fault quitting when one-pole series valve bank of a three-terminal hybrid direct current transmission system is in operation and communication faults between three stations occur, the technical scheme of the invention comprises the following steps:
when communication between three stations fails, each station cannot acquire signals such as running states of valve banks of each station after the failure, control protection action instructions and the like, and a direct-current voltage controller and a direct-current controller of each station are adjusted according to voltage and current instructions before the failure. When one valve bank of the LCC sending end station on the rectifying side fails, if the failed valve bank is locked, the direct-current voltage is still controlled to be 800kV by the VSC receiving end station on the inverting side, the non-failed valve bank of the LCC sending end station on the rectifying side is immediately over-voltage and is locked by the direct-current over-voltage protection action, and the operation is stopped. After a valve bank of the inversion side fixed direct current power VSC receiving end station breaks down, if only the fault valve bank is locked, because the inversion side fixed direct current voltage VSC receiving end station still controls the direct current voltage at 800kV, the inversion side fixed direct current power VSC receiving end station non-fault valve bank will be overvoltage and overcurrent immediately, and the protection such as direct current overvoltage and overcurrent protection will act and stop the operation extremely. After a valve bank of the inversion side fixed direct current voltage VSC receiving terminal fails, if only the failed valve bank is locked, because the inversion side fixed direct current voltage VSC receiving terminal can control the direct current voltage to be about 800kV for maintaining the direct current power, the inversion side fixed direct current voltage VSC receiving terminal non-failed valve bank can be immediately over-voltage and over-current, and the direct current over-voltage protection, the over-current protection and other protection can act and stop the operation. The invention provides that under the condition of communication failure between three stations, when all the valve group failure occurs during operation of the pole series valve groups, the protection action of the failed valve group is converted into a pole shutdown instruction, another valve group is jumped in parallel, poles are isolated, a neutral bus isolating switch is pulled, HSNBS is divided, and HSS is also divided from a VSC receiving end station, so that when the valve group failure exits, equipment is not damaged due to overvoltage and overcurrent.
When one valve bank of the rectifier side LCC send-end station fails, the valve bank exit method is shown in fig. 8. When a valve bank of the rectifying side LCC sending end station breaks down, after pole locking, if the inverting side fixed DC voltage VSC receiving end station is locked before the fixed DC voltage VSC receiving end station, the inverting side fixed power VSC receiving end station cannot maintain the stability of the DC voltage, the DC voltage will generate large fluctuation, and finally, the system may oscillate, so that the DC system loses stability. The invention provides that under the condition of communication failure between three stations, one valve bank of a rectification side LCC sending end station has failure, after pole locking, the inversion side fixed power VSC receiving end station is ensured to be firstly pole locked, and the inversion side fixed direct current voltage VSC receiving end station is finally locked, so that when each station exits, the direct current voltage can be ensured to be stable, and the direct current system is prevented from oscillating and losing stability.
When a valve bank fault exits at the LCC sending end station: if the valve bank protection sends an emergency stop command, the failed valve bank immediately shifts the phase, and simultaneously sends a protective locking command to the other valve bank, and the other valve bank immediately shifts the phase after receiving the protective locking command of the valve bank; the failure valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the extreme emergency shutdown command is carried out after 20 ms.
If the valve group protection sends a locking pulse command, the fault valve group is locked immediately, and simultaneously sends a protective locking command to the other valve group of the local pole, and the other valve group receives the protective locking command of the local valve group and immediately shifts the phase; the failure valve group converts the valve group protective locking trigger pulse command into an extreme emergency shutdown command, and the extreme shutdown is carried out after 20 ms.
After the inverter side constant direct current voltage VSC receiving end station stops operating at the rectifier side LCC transmitting end station, the direct current voltage drop is reduced due to the reduction of the direct current, the direct current voltage reference value UD _ REF _ VARC is increased, and the direct current voltage is increased in a short time; the inverter side fixed direct current power VSC receiving terminal station reduces the direct current port voltage thereof in order to maintain direct current. When the voltage of the port of the inverter side constant direct current voltage VSC receiving end station Is greater than the voltage of the direct current port of the constant direct current power VSC receiving end station, power Is reversely sent to the constant direct current power VSC receiving end station, the current direction of the constant direct current power VSC receiving end station Is reversed, the current value Is3 Is less than 0, the current value of the constant direct current power VSC receiving end station Is2, and the absolute values of the constant direct current power VSC receiving end station Is2 and Is3 are equal. If the maximum back-transmission power limit value PMAX of the inverter side constant direct-current voltage VSC receiving end station is not set, the back-transmission power may reach the power value of the constant direct-current power VSC station before the fault, the power flow direction of the whole power system will be affected, and even the frequency fluctuation of the inverter side constant direct-current voltage VSC station will be caused. The invention provides that under the condition of communication failure between three stations, one valve bank of a rectification side LCC station has failure, after the pole is locked, the maximum feedback power limit value PMAX of an inversion side fixed direct current voltage VSC station is limited, and the inversion side fixed direct current power VSC station and the fixed direct current voltage VSC station are locked in sequence through direct current low current in a short time.
The specific implementation mode is as follows: configuring a communication fault which is a minimum direct current voltage reference value limit UREF _ MIN (generally taking 0.6-0.7 p.u.) at two VSC stations, and setting a maximum feedback power limit PMAX (generally taking 0.06p.u.) at a fixed direct current voltage VSC station at an inversion side; and meanwhile, setting minimum current locking logic of the VSC station with the constant direct-current voltage, and locking poles after the actual current value of the VSC station is smaller than I _ SET (generally 0.07p.u., wherein the per unit value is the rated current of the VSC station) for a period of time. When the actual current Is2 of the inverter side constant direct current power VSC station Is less than I _ SET, the delay T1 (generally 120s) Is stopped by the direct current low current locking action, and the pole quitting Is completed. When the actual current Is3 of the inverter side constant direct current voltage VSC station Is less than I _ SET, the delay T2 (generally 120.5s) Is stopped by the direct current low current locking action, and the pole quitting Is completed.
Fig. 11 is a schematic diagram of a VSC receiving terminal dc low-current blocking logic according to an embodiment of the present invention. STATCOM _ MOD is the static reactive compensation MODE, OPEN _ LINE _ TEST is the unloaded pressurization TEST MODE, DEBLOCK _ IND indicates that the pole is in the unblock state, ACTIVE indicates that the polar control system control host computer is the main system, INVERTER indicates that the contravariant side receives end gentle straight VSC station, TWO _ VSC _ MODE indicates TWO pure gentle straight VSC station operational MODEs, IDCN _100 indicates each converter station actual direct current value, TCOM _ OK indicates that communication is all normal between the three terminal stations.
When the inverter side constant direct current power VSC station and the constant direct current voltage VSC station have a valve block fault in succession, the valve block exiting method is as shown in fig. 9 and 10. When the valve group faults occur in the inverter side fixed direct-current power VSC station and the fixed direct-current voltage VSC station in succession, after the two VSC stations stop running, the direct-current voltage of the rectifier side LCC sending end station is continuously increased. When the direct current voltage rises to a voltage control reference value U _ LCC _ REF (the value range of the U _ LCC _ REF is 1.03-1.04 p.u.), the LCC sending end station at the rectifying side enters constant voltage control, and if the direct current low current locking logic of the LCC sending end station at the rectifying side is not set, the direct current system is finally maintained at the constant voltage control of the LCC sending end station at the rectifying side, and the rectifying side runs in an idle state. The invention provides that under the condition of communication failure between three stations, a rectification side LCC station Is configured with direct current low current blocking logic, when the poles of a VSC receiving end station stop operation, the actual current value Is1 of an LCC sending end station Is less than I _ SET (generally 0.07p.u.), and the time delay T3 (generally 15s) Is completed by the direct current low current blocking operation stop operation pole and pole exit.
Fig. 12 is a schematic diagram of the low-current blocking logic of the LCC transmitting station according to the embodiment of the present invention. In the figure, OPEN _ LINE _ TEST is in a no-load pressurization TEST mode, a lockout _ IND finger is in an unlocking state, an ACTIVE finger control system control host is a main system, IDCN _100 indicates actual direct current values of all converter stations, and TCOM _ OK indicates that communication between three terminals is normal.
The invention has the beneficial effects that:
under the condition of communication failure among the three terminals, the invention provides that the extra-high voltage three-terminal hybrid direct-current series valve banks are all in an unlocked state, and when the valve banks fail to exit, the corresponding stations all adopt an extreme shutdown method, so that the problem that the non-failed valve banks are protected to act again due to overvoltage after the failed valve banks are locked can be effectively avoided. Meanwhile, aiming at the characteristics of the ultra-high voltage three-terminal mixed direct current, the invention designs a direct current low-current locking method which comprises the following steps: for the valve group fault of the rectification side LCC sending end station, after the rectification side pole is stopped, the inversion side fixed direct current power VSC receiving end station and the inversion side fixed direct current voltage VSC receiving end station can be ensured to be stably locked successively, and the condition that the VSC receiving end station is out of control is effectively avoided; meanwhile, after a valve group of a VSC receiving end station is extremely stopped due to fault, the other VSC receiving end station also has the working condition after the valve group is extremely stopped due to fault, the rectification side can be locked by low current, the LCC sending end station on the rectification side is prevented from long-time no-load operation, and the impact on the whole direct current system is reduced while the converter is guaranteed to safely exit.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A three-terminal hybrid direct-current valve group fault exit method during inter-station communication fault is disclosed, wherein a three-terminal hybrid direct-current transmission system comprises an LCC transmitting terminal station and two VSC receiving terminal stations; the two VSC receiving end stations are respectively a fixed direct-current voltage VSC receiving end station and a fixed direct-current power VSC receiving end station; each pole of the LCC sending end station comprises two LCC converter valve groups connected in series; each pole of the constant direct-current voltage VSC receiving end station and the constant direct-current power VSC receiving end station comprises two MMC converter valve groups which are connected in series; the method is characterized in that: the following three valve group fault exit conditions are provided under the condition of communication fault between three stations:
A. when a valve bank fault exits at the LCC sending end station:
step 1: if the valve bank protection sends an emergency stop command, the failed valve bank immediately shifts the phase, and simultaneously sends a protective locking command to the other valve bank, and the other valve bank immediately shifts the phase after receiving the protective locking command of the valve bank; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
if the valve group protection sends a locking pulse command, the fault valve group is locked immediately, and simultaneously sends a protective locking command to the other valve group of the local pole, and the other valve group receives the protective locking command of the local valve group and immediately shifts the phase; the fault valve group converts the valve group protective locking trigger pulse command into an extreme emergency shutdown command, and the extreme emergency shutdown command is carried out after 20 ms;
step 2: after the LCC sending end station is extremely stopped, the fixed direct current power VSC receiving end station maintains the direct current power, and the voltage of a direct current port is reduced; when the voltage of a port of a constant direct-current voltage VSC receiving end station is larger than the voltage of a direct-current port of a constant direct-current power VSC receiving end station, the constant direct-current voltage VSC receiving end station transmits power back to the constant direct-current power VSC receiving end station;
and step 3: configuring a minimum direct-current voltage reference value limit value of the valve group operation and maximum feedback power limit values of two VSC receiving end stations when communication faults of a fixed direct-current power VSC receiving end station and the fixed direct-current voltage VSC receiving end station occur;
and 4, step 4: setting a current reference value of direct-current low-current lock of each converter station as I _ SET; setting minimum current locking logic of a constant direct-current voltage VSC receiving terminal; when the actual current of the VSC receiving terminal station with constant direct current power is less than I _ SET, the pole is stopped by the direct current low-current locking action after T1 is delayed, and the pole quitting is finished;
and 5: when the actual current of the VSC receiving terminal is less than I _ SET, the pole is stopped due to the direct-current low-current locking action after T2 delay, and the pole quitting is finished;
B. when a valve bank fault of a fixed direct-current voltage VSC receiving end station exits:
step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;
step 2: if the valve group of the fixed direct current power VSC receiving end station does not have a fault, the direct current system is maintained in the constant current control of the LCC sending end station; determining the direct current power VSC receiving end station to continuously control the direct current power;
if the valve bank of the fixed direct current power VSC receiving end station fails; the fixed direct current power VSC receives a locking trigger pulse of the terminal station and simultaneously sends a zero pressure control instruction to enable the other valve group of the local pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;
and 4, step 4: the LCC sending end station is stopped due to low direct current, the LCC sending end station is stopped due to extreme stop, and the LCC sending end station is stopped due to three stations;
C. when a valve bank fault of a fixed direct current power VSC receiving end station exits:
step 1: the fault valve group immediately locks a trigger pulse and simultaneously sends a zero pressure control command to the other valve group, the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, the valve group is extremely shutdown after 20ms, and the extreme exit is completed;
step 2: if the valve group of the fixed direct-current voltage VSC receiving end station does not have a fault, the direct-current system is maintained in the constant current control of the LCC sending end station; the fixed direct-current voltage VSC receiving terminal station continuously controls the direct-current voltage;
if the valve bank of the fixed direct-current voltage VSC receiving end station fails; the constant direct-current voltage VSC receives a terminal station locking trigger pulse and simultaneously sends a zero pressure control instruction to enable the other valve group of the current pole to control zero pressure; the fault valve group converts the valve group emergency shutdown command into an extreme emergency shutdown command, and the valve group is extremely shutdown after 20 ms;
and step 3: increasing the direct-current voltage of the LCC sending end station to a voltage control reference value, and enabling the LCC sending end station to enter constant voltage control and run in no-load;
and 4, step 4: the LCC sending end station is stopped due to low direct current, the LCC sending end station is stopped due to extreme stop, and the LCC sending end station is stopped due to three stations.
2. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: setting the minimum direct-current voltage limit value of a fixed direct-current voltage VSC receiving end station within the range of 0.6-0.7 p.u.; setting the maximum back transmission power limit value of a fixed direct-current voltage VSC receiving end station within the range of 0.05-0.06 p.u.; the setting range of the I _ SET is 0.05-0.07 p.u. of the rated current value of each converter station; the value range of T1 is 120-150 s, and the value range of T2 is 0.5-1 s greater than that of T1; the value range of the voltage control reference value is 1.03-1.04 p.u.
3. The method for quitting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 2, wherein the method comprises the following steps: i _ SET is 0.07 p.u.; t1 is 120 s; t2 was 120.5 s.
4. The method for quitting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 2, wherein the method comprises the following steps: and when the two VSC receiving end stations stop running, the actual current value of the LCC sending end station is less than I _ SET, the direct-current low-current locking action stops running after the delay time is 15-20 s, and the three-station electrode stops running.
5. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: MMC transverter valves are formed by half-bridge submodule piece and full-bridge submodule piece mixture, and the component proportion of full-bridge submodule piece and half-bridge submodule piece is not less than 50%.
6. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: each converter valve bank is provided with a bypass switch Q93, a bypass isolation knife switch Q3, an anode isolation switch Q2 and a cathode isolation switch Q1.
7. The method for exiting the fault of the three-terminal hybrid direct-current valve bank during the inter-station communication fault as claimed in claim 1, wherein the method comprises the following steps: each pole is provided with a pole bus isolating switch Q9 and a high-speed neutral bus switch HSNBS; the VSC receiving end station is also provided with a high-speed parallel switch HSS.
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| CN111564863A (en) * | 2020-04-16 | 2020-08-21 | 南方电网科学研究院有限责任公司 | Third station online switching control system and method of direct current transmission system |
| CN111585256B (en) * | 2020-05-22 | 2022-08-19 | 西安许继电力电子技术有限公司 | Control method and device for hybrid cascade multi-end converter valve |
| CN111900756A (en) * | 2020-06-09 | 2020-11-06 | 许继集团有限公司 | Inter-station communication method for three-terminal direct-current power transmission system |
| CN111769549B (en) * | 2020-06-17 | 2023-12-15 | 中国南方电网有限责任公司 | Emergency power distribution method suitable for extra-high voltage three-terminal hybrid direct current |
| CN111953011B (en) * | 2020-06-23 | 2022-04-15 | 清华大学 | Cooperative frequency support control method and system for accessing double-fed wind power system into LCC-HVDC system |
| CN111769526A (en) * | 2020-07-07 | 2020-10-13 | 北京四方继保自动化股份有限公司 | Valve group fault exit control method for extra-high voltage multi-terminal hybrid direct-current transmission system |
| CN112865161B (en) * | 2021-01-05 | 2024-04-12 | 许继电气股份有限公司 | Control method and device for switching valve group of constant-power converter station during communication failure between stations |
| CN113541183A (en) * | 2021-06-11 | 2021-10-22 | 中国长江三峡集团有限公司 | Series multi-terminal bipolar direct-current power transmission system |
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