CN111342431B - Method for avoiding overvoltage generated in locking process in back-to-back direct current transmission - Google Patents
Method for avoiding overvoltage generated in locking process in back-to-back direct current transmission Download PDFInfo
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- CN111342431B CN111342431B CN202010217074.6A CN202010217074A CN111342431B CN 111342431 B CN111342431 B CN 111342431B CN 202010217074 A CN202010217074 A CN 202010217074A CN 111342431 B CN111342431 B CN 111342431B
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- grounding point
- current
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- locking
- direct current
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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
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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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 discloses a method for avoiding overvoltage generated in a locking process in back-to-back direct current transmission. By introducing the current of the grounding point as the auxiliary criterion of the locking time sequence, when the polar bus grounding fault occurs near the grounding point end, the NB locking is selectively executed, the direct-current system overvoltage phenomenon caused by the fact that the FB locking is directly executed by the protection action of the converter can be effectively avoided, the reliable isolation of the power system fault is facilitated, and the risk of primary equipment operation of the system is reduced.
Description
Technical Field
The invention belongs to the field of back-to-back direct-current power transmission control protection, and particularly relates to a method for avoiding overvoltage in a locking process through back-to-back direct-current power transmission.
Background
Back-to-back dc transmission systems are dc transmission systems with transmission line lengths of zero. This type of dc transmission is mainly used for networking or power transmission between two ac power systems operating asynchronously (at different frequencies or at the same frequency but not synchronized), also called asynchronous tie stations. The rectifier station arrangement and the inverter station arrangement for back-to-back dc transmission are usually installed in one converter station, also called back-to-back converter station. In the back-to-back converter station, the direct current sides of the rectifier and the inverter are connected through a smoothing reactor to form a closed loop at the direct current side; and the alternating current sides of the two power systems are respectively connected with the connection points of the connected power grids, so that asynchronous networking of the two power systems is formed. In addition, the converter station internal grounding point is arranged at the midpoint of the receiving end converter bridge.
Fig. 1 is a schematic diagram of a back-to-back dc transmission main connection and a fault point. S1 represents a direct current sending end, S2 represents a direct current receiving end, F1 represents a valve arm short-circuit fault, F2 represents a 6-pulse current converter short-circuit fault, F3 represents a pole bus ground fault close to a ground point, and IdGND represents ground point current.
The locking mode of the back-to-back direct current system protection is similar to that of the conventional direct current power transmission and is divided into instant locking (Fast Block/FB locking) and Normal locking (Normal Block/NB locking).
And (3) locking immediately: similar to a conventional X latch. Immediate latching is typically used for valve area short circuit faults, and the trigger pulse is latched immediately after the fault is discovered. The rectifier station and the inverter station have different processes.
Normal locking: similar to a conventional Y latch. The normal latch is a common latch, and is generally used in the occasions of direct current pole area fault, alternating current fault, normal pole latch and the like, and aims at some faults which do not cause serious damage to equipment.
When a direct current bus ground fault occurs at the end, close to the grounding point, of the back-to-back direct current transmission system, the fault point and the grounding point form a short circuit loop, and the current converter protection with short protection action time is caused to precede the ground protection action of a polar region. The inverter protection action causes the control system to perform FB lockout. The locking process easily causes overvoltage phenomenon of a direct current system, and harms related primary equipment of the system.
In order to avoid the generation of the direct current locking overvoltage phenomenon after the protection action of the converter, the method for avoiding the overvoltage generation in the locking process of back-to-back direct current transmission is adopted, and the conversion of the locking mode is realized by using the grounding point current as an auxiliary criterion, so that the overvoltage generation in the direct current locking process after the fault of a direct current system is effectively avoided.
Disclosure of Invention
The present invention provides a method for avoiding overvoltage generated in a latching process in a back-to-back dc power transmission system, so as to avoid overvoltage generated in a dc latching process after a dc system fails.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for avoiding overvoltage generated in a locking process in back-to-back direct current transmission comprises the following steps: when the back-to-back direct current system generates fault protection action near the grounding point end to send out an immediate locking instruction, the immediate locking instruction or a normal locking instruction is selectively executed through the grounding point current auxiliary criterion.
Further, the auxiliary criterion of the grounding point current is whether the grounding point current is smaller than a grounding point current threshold value.
Further, the auxiliary criterion for current through the grounding point selectively executes an immediate locking instruction or a normal locking instruction, specifically: and judging whether the grounding point current is smaller than a grounding point current threshold value, if so, executing an immediate locking instruction, and otherwise, executing a normal locking instruction.
Further, still include: and judging whether the grounding point current is smaller than a grounding point current threshold value, if so, judging that the fault type is a valve area short circuit fault, and otherwise, judging that the fault type is a polar area grounding fault.
Further, the value range of the grounding point current threshold value is 0.1pu-1.0pu.
The invention has the beneficial effects that: the scheme of the invention utilizes the grounding point current as an auxiliary criterion, so that the NB latching is selectively executed under the working condition of the converter protection action caused by the grounding fault of the polar bus, the overvoltage phenomenon caused by the direct execution of the FB latching by a direct current system is avoided, and the reliable isolation of the power system fault and the safety of key primary equipment are facilitated.
Drawings
Fig. 1 is a schematic diagram of back-to-back dc transmission main connections and fault points;
fig. 2 is a logic diagram of the technical scheme of the invention.
Detailed Description
The technical scheme of the invention is explained in detail in the following with the accompanying drawings.
The embodiment of the invention provides a method for avoiding overvoltage generated in a locking process by back-to-back direct current transmission, which comprises the following steps: when the back-to-back direct current system generates fault protection action near the grounding point end to send out an immediate locking instruction, the immediate locking instruction or a normal locking instruction is selectively executed through the grounding point current auxiliary criterion.
The scheme of the invention utilizes the grounding point current as an auxiliary criterion, can ensure that the working condition of the converter protection action caused by the grounding of the polar bus selectively executes the normal locking instruction, avoids the overvoltage phenomenon caused by the direct execution of the immediate locking instruction by the direct current system, and is favorable for the reliable isolation of the power system fault and the safety of the key primary equipment.
The second embodiment of the present invention will be described with reference to the logic diagram of fig. 2. The method specifically comprises the following steps:
s1, a back-to-back direct current system generates fault protection action near a grounding point end to send an immediate locking instruction;
s2, judging whether the grounding point current IdGND is smaller than a grounding point current threshold value Iset or not; the value range of the grounding point current threshold value is 0.1pu-1.0pu, and the typical value is 0.5pu. The determination result is yes when IdGND is smaller than Iset, and no when IdGND is greater than or equal to Iset.
S3, executing an immediate locking instruction according to the judgment result of the step S2; otherwise, executing the normal locking instruction.
By introducing grounding point current as an auxiliary criterion, different working conditions of converter protection action caused by valve area short-circuit fault (F1 or F2) and pole bus grounding fault (F3) are distinguished. When the valve area is in short circuit fault, the grounding point current is smaller than the grounding point current threshold value set by the auxiliary criterion, and the converter protection action direct current system executes FB locking; when the polar bus is in ground fault, the current of the grounding point is larger than or equal to the grounding point current threshold value set by the auxiliary criterion, and the converter protection action direct current system executes NB locking.
The third embodiment of the present invention further includes, on the basis of the first and second embodiments: and identifying the fault type according to the judgment result of whether the grounding point current is smaller than the grounding point current threshold value, if so, judging the fault type to be a valve area short circuit fault, otherwise, judging the fault type to be a polar area ground fault.
The above embodiments are only for illustrating the technical idea of the present invention, and the technical idea of the present invention is not limited thereto, and any modifications made on the basis of the technical solution according to the technical idea of the present invention fall within the protective scope of the present invention.
Claims (4)
1. A method for avoiding overvoltage generated in the locking process of back-to-back direct current transmission is characterized in that,
when a fault protection action occurs to a back-to-back direct current system close to a grounding point end to send an immediate locking instruction, judging a grounding point current auxiliary criterion before executing the instruction, and selectively executing the immediate locking instruction or a normal locking instruction according to a judgment result of the grounding point current auxiliary criterion, wherein the method specifically comprises the following steps: and judging whether the grounding point current is smaller than a grounding point current threshold value, if so, executing an immediate locking instruction, and otherwise, executing a normal locking instruction.
2. The method of claim 1, wherein: the auxiliary criterion of the grounding point current is whether the grounding point current is smaller than a grounding point current threshold value.
3. The method of claim 2, further comprising: and judging whether the current of the grounding point is smaller than a current threshold value of the grounding point, if so, judging that the fault type is a valve area short circuit fault, and otherwise, judging that the fault type is a polar area ground fault.
4. The method of claim 2 wherein the ground current threshold value ranges from 0.1pu to 1.0pu.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010217074.6A CN111342431B (en) | 2020-03-25 | 2020-03-25 | Method for avoiding overvoltage generated in locking process in back-to-back direct current transmission |
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| CN202010217074.6A CN111342431B (en) | 2020-03-25 | 2020-03-25 | Method for avoiding overvoltage generated in locking process in back-to-back direct current transmission |
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| CN111342431B true CN111342431B (en) | 2022-12-09 |
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Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE515140C2 (en) * | 1995-02-10 | 2001-06-18 | Abb Ab | Installation for transmission of electrical power by means of high voltage direct current |
| CN100414797C (en) * | 2006-06-28 | 2008-08-27 | 南京南瑞继保电气有限公司 | Method for judging high-voltage polar wire short out of low voltage polar wire in back-to-back DC engineering |
| CN101369726A (en) * | 2006-06-28 | 2009-02-18 | 南京南瑞继保电气有限公司 | Method for fast recognition of back-to-back direct current system ground fault by utilization of voltage auxiliary criterion |
| CN101359876A (en) * | 2008-09-27 | 2009-02-04 | 北京网联直流工程技术有限公司 | DC system locking method for back-to-back DC networking project |
| CN105162155B (en) * | 2015-08-26 | 2017-10-27 | 浙江大学 | A kind of series hybrid bipolar direct current transmission system with DC Line Fault ride-through capability |
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2020
- 2020-03-25 CN CN202010217074.6A patent/CN111342431B/en active Active
Non-Patent Citations (1)
| Title |
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| 并联换流器直流输电中换流器区故障分析及处理策略;许训炜等;《电力系统自动化》;20161010;第40卷(第19期);第101-105页 * |
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