CN110729749A - Method for realizing quick conversion of ground return wire and metal return wire by using half-bridge MMC structure - Google Patents
Method for realizing quick conversion of ground return wire and metal return wire by using half-bridge MMC structure Download PDFInfo
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- CN110729749A CN110729749A CN201911120643.9A CN201911120643A CN110729749A CN 110729749 A CN110729749 A CN 110729749A CN 201911120643 A CN201911120643 A CN 201911120643A CN 110729749 A CN110729749 A CN 110729749A
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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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- 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 application provides an utilize half-bridge MMC structure to realize ground return wire metallic return line fast switching method, compromise the characteristics of flexible high voltage direct current transmission system, with the help of IGBT and the diode of half-bridge MMC structure, utilize the short characteristic of IGBT on-time, through simple operating procedure, realize ground return wire to metallic return line's fast switching, reduce the direct current greatly and flow into ground time, reduce the influence to facility on every side. Meanwhile, under the condition that no grounding electrode exists or the grounding electrode is unavailable, the reliability of the system can be improved, the probability of bipolar locking is reduced, and the stability of the system is improved.
Description
Technical Field
The invention belongs to the field of high-voltage direct-current power transmission systems, and particularly relates to a method for realizing quick conversion of ground return metal loops by using a half-bridge MMC structure.
Background
The direct current transmission system has multiple operation modes, including bipolar operation, monopole earth return operation and monopole metal return operation. When one DC pole is overhauled or has a fault, the other DC pole can continue to operate in a single-pole ground return line operation mode, so that the reliability of the DC transmission system is greatly improved. However, the long-term ground return operation easily causes problems of magnetic biasing, excessive low current entering and the like, so the operation mode of automatically converting the single-pole ground return into the single-pole metal return is often adopted under the fault condition, and meanwhile, under the condition that no grounding pole exists or the grounding pole is unavailable, when the single-pole locking occurs, the conversion from the single-pole ground return to the single-pole metal return must be completed quickly.
The existing large-scale metal transfer scheme is usually realized by using a switch to conduct, a metal loop is switched on by using an isolating switch and a metal loop switch MRS, and the current of a grounding electrode loop is shunted to the metal loop, so that the large-scale metal transfer is realized.
Disclosure of Invention
Based on the method, the invention aims to provide a method for realizing the quick metal return line conversion of the ground return line by utilizing a half-bridge MMC structure.
The invention provides a method for realizing quick conversion of a ground return metal loop by using a half-bridge MMC structure, which is applied to a direct-current power transmission system and comprises the following steps:
s1, a direct current passes through a neutral line high-speed switch HSNBS at a sending end, a metal loop transfer switch MRTB and a sending end grounding electrode to form a single-pole ground loop, a transistor switch T2 of a half-bridge MMC structure at an inversion side is triggered, and a shunt path is formed through a diode D2 of the half-bridge MMC structure at an rectification side;
s2, redistributing the direct current between the grounding electrode circuit and the direct current electrode wire;
s3, disconnecting the metal loop transfer switch MRTB, and enabling current to flow to a direct-current polar line of a fault pole through a neutral line high-speed switch HSNBS and a valve group bypass breaker at a sending end;
and S4, closing the metal loop of the fault pole by using the isolating switch and the metal loop switch MRS of the sending end to complete the conversion between the ground return wire and the metal return wire.
Preferably, step S4 is followed by:
and S5, disconnecting the related isolating switch.
Preferably, step S1 is preceded by:
and S01, when the single pole fails, the ground return wire and the metal return wire are switched only when the switching condition is met, and the double pole is locked without switching.
Preferably, step S1 is preceded by:
and S02, disconnecting the current conversion transformer incoming line circuit breaker at the sending end and the receiving end of the fault electrode, wherein normal inter-station communication needs to be ensured when the current conversion transformer incoming line circuit breaker at the sending end is disconnected.
Preferably, the direct current transmission system is a flexible high voltage direct current transmission system.
According to the technical scheme, the invention has the following advantages:
the invention provides a method for realizing quick conversion of a ground return wire and a metal return wire by utilizing a half-bridge MMC structure, which has the characteristics of a flexible high-voltage direct-current transmission system, realizes quick conversion of the ground return wire to the metal return wire by means of an IGBT and a diode of the half-bridge MMC structure through simple operation steps, greatly reduces the time of direct current flowing into the ground, and reduces the influence on surrounding facilities. Meanwhile, under the condition that no grounding electrode exists or the grounding electrode is unavailable, the reliability of the system can be improved, the probability of bipolar locking is reduced, and the stability of the system is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a flow chart of a method for implementing a fast ground return metal loop conversion using a half-bridge MMC structure according to an embodiment of the present invention
FIG. 2 is a schematic diagram of a single-pole ground return operating current loop in single-pole locking according to an embodiment of the present invention
FIG. 3 is a schematic diagram of a current loop for realizing a metal loop switching in an embodiment of the present invention
FIG. 4a is a schematic diagram of a current path of a half-bridge MMC structure on a rectifying side according to an embodiment of the present invention
FIG. 4b is a schematic diagram of a current path of an inverter-side half-bridge MMC structure according to an embodiment of the present invention
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4b, the present embodiment provides a method for realizing fast conversion of a ground return metal loop by using a half-bridge MMC structure, which is suitable for a flexible high-voltage power transmission system, where the flexible dc power transmission system with a half-bridge MMC structure includes two or more converter stations connected by a dc line, and each converter station dc side includes a high-speed neutral bus switch HSNBS, a metal loop conversion circuit breaker MRTB, a metal loop disconnecting switch, and a metal loop switch MRS.
In the present embodiment, the pole 1 is used as an operating pole, and the pole 2 is used as a fault pole (blocking pole), when the flexible high-voltage power transmission system is in a single-pole earth return operation, the current loop is as shown in fig. 2, the dotted line with an arrow in the upper half of fig. 2 indicates that current flows through the single-pole earth return, and the direct current passes through the neutral line high-speed switch HSNBS, the metal loop changeover switch MRTB and the earth pole line and finally enters the ground.
The method for quickly switching from the earth return wire to the metal return wire comprises the following steps:
s01, when the conversion condition is met, the earth return wire and the metal return wire are converted, and when the double poles are locked, the conversion is not carried out;
s02, disconnecting the current conversion transformer incoming line circuit breakers at the sending end and the receiving end, wherein normal inter-station communication needs to be ensured when the current conversion transformer incoming line circuit breaker at the sending end is disconnected;
s1, a direct current passes through a neutral line high-speed switch HSNBS at a sending end, a metal loop transfer switch MRTB and a sending end grounding electrode to form a single-pole ground loop, a transistor switch T2 of a half-bridge MMC structure at an inversion side is triggered, and a shunt path is formed through a diode D2 of the half-bridge MMC structure at an rectification side;
s2, redistributing the direct current between the grounding electrode circuit and the direct current electrode wire;
s3, disconnecting the metal loop transfer switch MRTB, and enabling current to flow to a direct-current pole line of the pole 2 through a neutral line high-speed switch HSNBS and a valve group bypass breaker at a sending end, as shown in FIG. 3, wherein a dotted line with an arrow in the upper half part of the FIG. 3 represents operation of a single-pole ground return line, and a solid line with an arrow in the lower half part represents current shunting of a metal return line flowing to a fault pole;
s4, closing the isolating switch for the metal loop of the pole 2 and the metal loop switch MRS of the sending end to complete the conversion between the ground loop and the metal loop;
s5, disconnecting the related isolating switch until the conversion between the ground return wire and the metal return wire is completed.
The half-bridge MMC structure with rectification side and inversion side is shown in fig. 4a and 4b, and the dashed straight arrows indicate the current paths.
It should be noted that when the pole 1 is a fault pole and the pole 2 is an operation pole, the fast switching between the earth return and the metal return can be analogized according to the essence of the present invention.
The characteristics of flexible high voltage direct current transmission system are taken into account to this embodiment, with the help of IGBT and the diode of half-bridge MMC structure, through simple operating procedure, realize the ground return wire to the quick switching of metallic return wire, reduce the direct current greatly and flow into ground time, reduce the influence to facility on every side. Meanwhile, under the condition that no grounding electrode exists or the grounding electrode is unavailable, the reliability of the system can be improved, the probability of bipolar locking is reduced, and the stability of the system is improved.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (5)
1. A method for realizing rapid conversion of a ground return metal loop by using a half-bridge MMC structure is applied to a direct-current power transmission system and is characterized by comprising the following steps:
s1, a direct current passes through a neutral line high-speed switch HSNBS at a sending end, a metal loop transfer switch MRTB and a sending end grounding electrode to form a single-pole ground loop, a transistor switch T2 of a half-bridge MMC structure at an inversion side is triggered, and a shunt path is formed through a diode D2 of the half-bridge MMC structure at an rectification side;
s2, redistributing the direct current between the grounding electrode circuit and the direct current electrode wire;
s3, disconnecting the metal loop transfer switch MRTB, and enabling current to flow to a direct-current polar line of a fault pole through a neutral line high-speed switch HSNBS and a valve group bypass breaker of the sending end;
and S4, closing the isolating switch for the metal loop of the fault pole and the metal loop switch MRS of the sending end to complete the conversion between the ground loop and the metal loop.
2. The method of claim 1, further comprising after step S4:
and S5, disconnecting the related isolating switch.
3. The method of claim 1, further comprising before step S1:
and S01, when the single pole fails, the ground return wire and the metal return wire are switched only when the switching condition is met, and the double pole is locked without switching.
4. The method of claim 1, further comprising before step S1:
and S02, disconnecting the current conversion transformer incoming line circuit breaker at the sending end and the receiving end of the fault electrode, wherein the normal communication between stations is required to be ensured when the current conversion transformer incoming line circuit breaker at the sending end is disconnected.
5. The method for achieving ground return metal loop fast conversion using a half-bridge MMC structure of claim 1, wherein the DC power transmission system is a flexible HVDC power transmission system.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911120643.9A CN110729749A (en) | 2019-11-15 | 2019-11-15 | Method for realizing quick conversion of ground return wire and metal return wire by using half-bridge MMC structure |
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| CN201911120643.9A CN110729749A (en) | 2019-11-15 | 2019-11-15 | Method for realizing quick conversion of ground return wire and metal return wire by using half-bridge MMC structure |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111416374A (en) * | 2020-02-28 | 2020-07-14 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Bipolar direct-current power transmission system and operation mode switching method thereof |
| CN112290520A (en) * | 2020-11-13 | 2021-01-29 | 中国南方电网有限责任公司超高压输电公司昆明局 | Grounding fault protection method for metal return line of three-terminal direct-current power transmission system |
| CN113437806A (en) * | 2021-08-27 | 2021-09-24 | 中国南方电网有限责任公司超高压输电公司广州局 | Method and device for controlling opening of metal loop switch and computer equipment |
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| CN106487033A (en) * | 2016-12-15 | 2017-03-08 | 南方电网科学研究院有限责任公司 | In a kind of Hybrid HVDC system, total head turns conversion method and the system that half pressure is run |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111416374A (en) * | 2020-02-28 | 2020-07-14 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Bipolar direct-current power transmission system and operation mode switching method thereof |
| CN112290520A (en) * | 2020-11-13 | 2021-01-29 | 中国南方电网有限责任公司超高压输电公司昆明局 | Grounding fault protection method for metal return line of three-terminal direct-current power transmission system |
| CN113437806A (en) * | 2021-08-27 | 2021-09-24 | 中国南方电网有限责任公司超高压输电公司广州局 | Method and device for controlling opening of metal loop switch and computer equipment |
| CN113437806B (en) * | 2021-08-27 | 2021-12-03 | 中国南方电网有限责任公司超高压输电公司广州局 | Method and device for controlling opening of metal loop switch and computer equipment |
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