CN109347134B - Bipolar flexible DC power grid pole line electrical main wiring system and online maintenance method - Google Patents
Bipolar flexible DC power grid pole line electrical main wiring system and online maintenance method 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
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B3/00—Apparatus specially adapted for the manufacture, assembly, or maintenance of boards or switchgear
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
本发明涉及一种双极柔性直流电网极线电气主接线系统及在线检修方法，其包括从交流侧到极线的电气主接线电路，交流侧输电线一端经交流侧穿墙套管与从交流侧到极线的电气主接线电路一端连接，从交流侧到极线的电气主接线电路另一端经换流器到直流汇流母线的电气主接线电路连接至直流汇流母线一侧；交流侧输电线另一端经交流侧穿墙套管与从交流侧到中性线的电气主接线电路一端连接，从交流侧到中性线的电气主接线电路另一端经中性线穿墙套管与中性线区域连接；两直流断路器接线电路一端均与直流汇流母线另一侧连接，两直流断路器接线电路另一端分别经第一极线穿墙套管和第二极线穿墙套管与户外极线1电气主接线电路、户外极线2电气主接线电路连接。
The invention relates to a bipolar flexible DC power grid pole line electrical main wiring system and an on-line maintenance method, comprising an electrical main wiring circuit from an AC side to a pole line, one end of an AC side transmission line passing through a wall bushing on the AC side and connecting from the AC side to the pole line. One end of the electrical main wiring circuit from the side to the pole line is connected, and the other end of the electrical main wiring circuit from the AC side to the pole line is connected to one side of the DC bus bar through the inverter to the electrical main wiring circuit of the DC bus bar; AC side transmission line The other end is connected to one end of the electrical main wiring circuit from the AC side to the neutral line through the AC side wall bushing, and the other end of the electrical main wiring circuit from the AC side to the neutral line is connected to the neutral via the neutral line wall bushing. One end of the wiring circuit of the two DC circuit breakers is connected to the other side of the DC busbar, and the other end of the wiring circuit of the two DC circuit breakers is connected to the outdoor through the first pole line wall bushing and the second pole line wall bushing respectively. The pole line 1 electrical main wiring circuit and the outdoor pole line 2 electrical main wiring circuit are connected.
Description
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a bipolar flexible direct current power grid polar line electric main wiring system and a direct current breaker online maintenance method.
Background
The flexible direct current transmission technology is a new generation direct current transmission technology based on a fully-controlled power electronic device, has the characteristics of high response speed, good controllability, flexible operation mode, small occupied area and the like with the same capacity, is in a rapid development stage at present, and a plurality of flexible direct current transmission projects are planned, designed and built, such as a Yubei +/-420 kV flexible direct current back-to-back project, a Zhang northe +/-500 kV four-end flexible direct current power grid project, a Wudongde +/-800 kV mixed flexible direct current transmission project and the like in China. The high-capacity flexible direct-current power grid can exert the technical advantages of flexible direct-current power transmission, can realize multi-power supply or multi-drop power supply, and is an effective solution for accessing and conveying a large-scale renewable energy source grid, wind, light, storage and pumped storage.
The design of the main electrical connection is one of the key contents of the research of the transmission technology of the flexible direct current power grid system, the determination of the main electrical connection is closely related to the reliability, flexibility and economy of the operation of the whole power system and the converter station, and the main electrical connection has great influence on the selection of electrical equipment, the arrangement of a power distribution device, relay protection and the design of a control mode. Therefore, the relation of all aspects must be correctly processed, relevant influence factors must be comprehensively analyzed, and the main wiring scheme of the flexible direct current transmission system must be reasonably determined. For main wiring of flexible direct-current power transmission systems with multiple forms such as two ends, multiple ends, back-to-back and the like, more documents are discussed at home and abroad; however, the design of the electrical main connection of the flexible direct-current power grid, particularly the electrical main connection of the polar line area, is rarely related; the polar line high-voltage direct-current circuit breaker is one of the most core key devices in flexible direct-current power grid engineering, can complete the disconnection of fault current within milliseconds, quickly and reliably realize the isolation and the coincidence of fault lines, and simultaneously can realize the flexible switching on and off of a converter station in a direct-current power grid, thereby having important significance for ensuring the safe and continuous operation of a sound system and improving the reliability of the direct-current power grid.
The main polar line connection covers main primary equipment in a polar line area, and the main primary equipment comprises a modular multilevel converter, a direct current breaker, a bridge arm reactor, a direct current isolation and grounding switch, a measuring device, a lightning arrester, a wall bushing and other primary equipment, and the arrangement type and the relative position of each voltage and current measuring device need to be disclosed. The determination of the change-over switch in the neutral line region is closely related to the reliability, flexibility and economy of the operation of the whole power system and the converter station, and three basic requirements of the reliability, the flexibility and the economy are met: (1) and (6) reliability. The design scheme should ensure that the flexible direct current grid system has high reliability. (2) Flexibility. The design scheme should meet the flexibility requirements during normal operation and during overhaul and extension. (3) And (4) economy. The design scheme has simple stress requirement so as to save primary equipment. Meanwhile, the scheme occupies small area.
The determination of the main electrical wiring needs to consider an insulation matching principle, the requirement of controlling and protecting electrical quantity measuring points, the switching of a switch operation mode and a maintenance state, the starting and charging of a system and the like. After the polar line electric main connection determines the specific schemes of key equipment such as switches, another key problem to be solved is how to complete the online maintenance of the direct current circuit breaker by using the configured switches without influencing the normal operation of the rest part of the direct current power grid. However, the existing technical means do not relate to a switching scheme and a direct current breaker online maintenance method in a bipolar flexible direct current network pole line area with a metal return line.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a bipolar flexible dc power grid line electrical main connection system and a dc circuit breaker online maintenance method, which can rapidly switch on and off in a current conversion due to fault without affecting the normal operation of the remaining dc power grid, save the number of dc circuit breakers, and have low cost of primary equipment.
In order to achieve the purpose, the invention adopts the following technical scheme: a bipolar flexible direct current grid polar line electric main wiring system is arranged in a valve hall and comprises an electric main wiring circuit from an alternating current side to a polar line, an electric main wiring circuit from the alternating current side to a neutral line, an electric main wiring circuit from an inverter to a direct current bus bar, a direct current breaker wiring circuit connected with an outdoor polar line 1 and a direct current breaker wiring circuit connected with an outdoor polar line 2; one end of the alternating current side transmission line is connected with one end of the electric main wiring circuit from the alternating current side to the polar line through a first alternating current side wall bushing, and the other end of the electric main wiring circuit from the alternating current side to the polar line is connected to one side of the direct current bus bar through the electric main wiring circuit from the converter to the direct current bus bar; the other end of the alternating-current side power transmission line is connected with one end of an electric main wiring circuit from the alternating-current side to the neutral line through a second alternating-current side wall bushing, and the other end of the electric main wiring circuit from the alternating-current side to the neutral line is connected with the neutral line area through the neutral line wall bushing; two direct current breaker wiring circuit one end all with direct current busbar opposite side is connected, two the direct current breaker wiring circuit other end is respectively through first polar line wall bushing and second polar line wall bushing and outdoor polar line 1 electric main wiring circuit, outdoor polar line 2 electric main wiring circuit connection.
Further, the electric main wiring circuit from the alternating current side to the pole line comprises a first grounding switch QS01, a direct current measuring device CT1, a direct current arrester LV1, a converter upper bridge arm valve tower, a direct current arrester CBH, a voltage measuring device PT1 and a direct current measuring device CT 3; one end of the direct current measuring device CT1 is connected with one end of the alternating current side transmission line, and the first grounding switch QS01 is connected between the direct current measuring device CT1 and the alternating current side transmission line in parallel; the other end of the direct current measuring device CT1 is connected with one end of the direct current measuring device CT3 through an upper bridge arm valve tower of the converter, and the other end of the direct current measuring device CT3 is connected with an electric main wiring circuit from the converter to a direct current bus bar; the direct current arrester LV1 is arranged on a line between the direct current measuring device CT1 and the converter upper bridge arm valve tower, and the direct current arrester CBH and the voltage measuring device PT1 are sequentially arranged on a line between the converter upper bridge arm valve tower and the direct current measuring device CT3 in parallel.
Further, the converter to dc bus electrical main connection circuit comprises a first double ground knife disconnector Q1 with a first ground knife QS11 and a second ground knife QS12, a dc bus fast disconnector CB1, a second double ground knife disconnector Q2 with a third ground knife QS21 and a fourth ground knife QS22, and a start circuit; one end of the first ground knife QS11, one end of the second ground knife QS12, one end of the third ground knife QS21 and one end of the fourth ground knife QS22 are all connected in parallel on a line between the other end of the direct current measuring device CT3 and the direct current bus bar; on a line between the other end of the direct current measuring device CT3 and the direct current bus bar; the direct current bus quick isolating switch CB1 is arranged between the second ground switch QS12 and the third ground switch QS21, and the starting circuit is connected in parallel to two ends of the direct current bus quick isolating switch CB 1.
Further, the starting circuit comprises a disconnecting switch Q3 without a grounding knife, a direct current side starting resistor R1 and a direct current device CT4 which are connected in series in sequence.
Further, the main electrical connection circuit from the ac side to the neutral line comprises a second earthing switch QS02, a dc measuring device CT2, a dc arrester LV2, a converter lower arm valve tower, a dc arrester CBN1 and a third earthing switch QS 03; one end of the direct current measuring device CT2 is connected with the other end of the alternating current side power transmission line, and a second grounding switch QS02 is connected between the direct current measuring device CT2 and the alternating current side power transmission line in parallel; the other end of the direct current measuring device CT2 is connected with a neutral line area through the converter lower bridge arm valve tower; the direct current arrester LV2 is arranged on a line between the direct current measuring device CT2 and the converter lower arm valve tower, and the direct current arrester CBN1 and a third grounding switch QS03 are sequentially arranged on a line between the converter lower arm valve tower and the neutral line area in parallel.
Further, the direct current breaker connection circuit connected with the outdoor pole line 1 and the direct current breaker connection circuit connected with the outdoor pole line 2 both comprise a direct current breaker DCCB1, a direct current breaker overhaul circuit, a direct current lightning arrester DB1, a fourth grounding switch QS04 and a direct current measuring device CT 5; the direct current breaker overhauling circuit is connected with the direct current breaker DCCB 1; one end of the direct current breaker DCCB1 is connected with the other side of the direct current bus bar, and the other end of the direct current breaker DCCB1 is connected with the outdoor polar line electric main wiring circuit through the direct current measuring device CT 5; the direct current lightning arrester DB1 and a fourth grounding switch QS04 are arranged on the line of the other end of the direct current breaker DCCB1 and the direct current measuring device CT5 in parallel.
Further, the dc breaker service circuit includes a fifth ground switch QS3, a disconnector Q3 with a single ground switch QS3, a disconnector Q4 without a ground switch, a sixth ground switch QS5 and a disconnector Q5 with a single ground switch QS 5; a disconnecting switch Q3 with a single grounding knife QS3 is connected in series to a line between the direct current breaker DCCB1 and the direct current bus bar, and a fifth grounding knife QS3 is connected in parallel to a line between the disconnecting switch Q3 with the single grounding knife QS3 and the direct current breaker DCCB 1; a disconnecting switch Q5 with a single ground knife QS5 is connected in series to a line between the dc circuit breaker DCCB1 and the dc current measuring device CT5, and a sixth ground knife QS5 is connected in parallel to a line between a disconnecting switch Q5 with a single ground knife QS5 and the dc circuit breaker DCCB 1; the disconnector Q4 without ground switch is connected across disconnector Q3 with single ground switch QS3 and disconnector Q5 with single ground switch QS 5.
Further, the dc current measuring device CT5 is a bushing structure, and is disposed in the first pole wire wall bushing B3.
Further, a first grounding switch QS01 in the electric main wiring circuit from the ac side to the pole line, and a second grounding switch QS02 and a third grounding switch QS03 in the electric main wiring circuit from the ac side to the neutral line are all sidewall type grounding switches.
The utility model provides a bipolar flexible direct current electric wire netting polar electricity owner wiring on-line maintenance method based on above-mentioned system, this method carries out on-line maintenance to direct current circuit breaker, and it includes the following step: 1) closing the isolating switch Q4 without the ground knife; 2) opening the dc breaker DCCB 1; 3) disconnecting an isolating switch Q3 with a single grounding knife QS3 and an isolating switch Q5 with a single grounding knife QS 5; 4) closing a fifth earthing switch QS3 and a sixth earthing switch QS 5; 5) in the maintenance process of the DC circuit breaker DCCB1, pole line current flows from a bypass isolating switch Q4 without a grounding switch, and the on-line maintenance and transmission power of the pole line DC circuit breaker are not interrupted.
Due to the adoption of the technical scheme, the invention has the following advantages: 1. the flexible direct-current power grid polar line region electric main wiring system has the advantages of small quantity of required equipment, compact configuration, optimized occupied area, high economical efficiency and the like, and has popularization significance. 2. The bipolar rapid switch configuration scheme with the direct-current bus can be used for rapidly switching on and off the current conversion on line due to faults without influencing the normal operation of the residual direct-current power grid, so that the number of direct-current circuit breakers is saved, and the cost of primary equipment is low. The flexible operation mode conversion and maintenance requirements are met, and meanwhile, the reliability of the flexible direct current power grid can be met. 3. The invention provides the method for carrying out the on-line maintenance of the direct current breaker by using the configured switch, does not influence the normal operation of the rest direct current power grid, and has the characteristics of simple and easy steps, clearness and the like. In conclusion, the invention can be widely applied to the application occasions of the bipolar flexible direct current power grid with the metal return wire.
Drawings
FIG. 1 is a schematic diagram of the overall structure of a bipolar flexible DC power grid;
FIG. 2 is a schematic diagram of the polar electrical main wiring system of the present invention;
FIG. 3 is a schematic diagram of a three-phase structure of a modular multilevel converter based on half-bridge sub-modules;
fig. 4 is a prior art conventional dc circuit breaker configuration method;
fig. 5 is a method for configuring a dc bus fast switch according to the present invention.
Detailed Description
As shown in fig. 1, in order to realize that the exiting of any line or commutation unit does not affect the normal operation of the remaining elements of the dc power grid in the overall structure of the bipolar flexible dc power grid, the pole line high voltage dc circuit breaker is essential. In view of the fact that a high-voltage direct-current circuit breaker, particularly a direct-current circuit breaker above 500kV, has no design operation experience, the possible failure rate is high in actual operation, and the normal operation of the rest system is not influenced as much as possible by overhauling during failure. Therefore, a reasonable arrangement of the disconnecting switches near the dc circuit breaker is needed based on this principle to facilitate the maintenance. The invention is described in detail below with reference to the figures and examples.
As shown in fig. 2, the present invention provides a bipolar flexible dc grid pole line electrical main wiring system, which is provided in a valve hall, and includes an electrical main wiring circuit from an ac side to a pole line, an electrical main wiring circuit from an ac side to a neutral line, an electrical main wiring circuit from an inverter to a dc bus bar, a dc breaker wiring circuit connected to an outdoor pole line 1, and a dc breaker wiring circuit connected to an outdoor pole line 2. One end of the ac-side power transmission line is connected to one end of an electric main wiring circuit from the ac side to the pole line through a first ac-side wall bushing B1 (three phases a, B, and c), and the other end of the electric main wiring circuit from the ac side to the pole line is connected to one side of the dc bus through an electric main wiring circuit from the inverter to the dc bus. The other end of the ac side power line is connected to one end of the main electrical connection circuit from the ac side to the neutral line via a second ac side wall bushing B2, and the other end of the main electrical connection circuit from the ac side to the neutral line is connected to the neutral line region via a neutral line wall bushing B5. One ends of the two direct current breaker wiring circuits are connected with the other side of the direct current bus bar, and the other ends of the two direct current breaker wiring circuits are respectively connected with an outdoor polar line 1 electric main wiring circuit and an outdoor polar line 2 electric main wiring circuit through a first polar line wall bushing B3 and a second polar line wall bushing B4.
In the above embodiment, preferably, the main electrical connection circuit from the ac side to the pole line includes a first grounding switch (grounding switch) QS01 (three phases a, b, and c), a dc measurement device CT1 (three phases a, b, and c), a dc arrester LV1 (three phases a, b, and c), an upper bridge arm valve tower of the converter (three phases a, b, and c), a dc arrester CBH, a voltage measurement device PT1, and a dc current measurement device CT 3. One end of a direct current measuring device CT1 is connected with one end of an alternating current side power transmission line, and a first grounding switch QS01 is connected between the direct current measuring device CT1 and the alternating current side power transmission line in parallel; the other end of the direct current measuring device CT1 is connected with one end of a direct current measuring device CT3 through an upper bridge arm valve tower of the converter, and the other end of the direct current measuring device CT3 is connected with an electric main wiring circuit from the converter to a direct current bus bar. A direct current arrester LV1 is arranged on a line between the direct current measuring device CT1 and an upper bridge arm valve tower of the converter, and one end of the direct current arrester LV1 is grounded; a direct current arrester CBH and a voltage measuring device PT1 are sequentially arranged in parallel on a line between an upper bridge arm valve tower of the converter and the direct current measuring device CT3, and one end of the direct current arrester CBH and one end of the voltage measuring device PT1 are both grounded; the voltage measuring device PT1 is used for measuring the pole line voltage for dc over-voltage and under-voltage protection.
And a direct current voltage measuring device PT2 is also arranged on one side of the direct current bus and used for measuring the voltage of the direct current bus.
In the above embodiments, it is preferable that the electric main connection circuit from the inverter to the dc bus bar includes a first ground switch QS11, a second ground switch QS12, a first double-ground-knife-included isolation switch Q1 (the ground switches are a first ground switch QS11 and a second ground switch QS12, respectively), a dc bus fast isolation switch CB1 (the CB1 is an ac circuit breaker with dc withstand voltage capability), a third ground switch QS21, a fourth ground switch QS22, a second double-ground-knife-included isolation switch Q2 (the ground switches are a third ground switch QS21 and a fourth ground switch QS22, respectively), and a start circuit. One end of a first ground knife QS11, one end of a second ground knife QS12, one end of a third ground knife QS21 and one end of a fourth ground knife QS22 are all connected in parallel on a circuit between the other end of the DC current measuring device CT3 and the DC bus bar, and the other end of the first ground knife QS11, the other end of the second ground knife QS12, the other end of the third ground knife QS21 and the other end of the fourth ground knife QS22 are all grounded. On the line between the other end of the direct current measuring device CT3 and the direct current bus bar; a direct current bus quick isolating switch CB1 is arranged between the second grounding knife QS12 and the third grounding knife QS21, and the starting circuit is connected in parallel at two ends of the CB 1.
The starting circuit comprises a disconnecting switch Q3 without a grounding knife, a direct current side starting resistor R1 and a direct current device CT4 which are sequentially connected in series.
In the above embodiments, preferably, the main electrical connection circuit from the ac side to the neutral line includes a second earthing switch (earthing switch) QS02 (three phases a, b, and c), a dc measuring device CT2 (three phases a, b, and c), a dc arrester LV2 (three phases a, b, and c), a converter lower arm valve tower (three phases a, b, and c), a dc arrester CBN1, and a third earthing switch (earthing switch) QS 03. One end of the direct current measuring device CT2 is connected with the other end of the alternating current side power transmission line, and a second grounding switch QS02 is connected between the direct current measuring device CT2 and the alternating current side power transmission line in parallel; the other end of the direct current measuring device CT2 is connected with the neutral line area through a converter lower bridge arm valve tower. A direct current arrester LV2 is arranged on a line between the direct current measuring device CT2 and the converter lower bridge arm valve tower, and one end of the direct current arrester LV2 is grounded; and a direct current arrester CBN1 and a third grounding switch QS03 are sequentially arranged in parallel on a line between a converter lower bridge arm valve tower and a neutral wire area, and one ends of the direct current arrester CBN1 and one end of the third grounding switch QS03 are both grounded.
In a preferred embodiment, the configuration of the measurement device needs to be consistent with the control protection design. The direct current measuring device CT1 and the direct current measuring device CT2 measure bridge arm currents, are used for bridge arm overcurrent protection and form current differential protection with the direct current measuring device CT 3.
In the above embodiments, it is preferable that the dc breaker connection circuit connected to the outdoor pole line 1 and the dc breaker connection circuit connected to the outdoor pole line 2 have the same structure, and the dc breaker connection circuit connected to the outdoor pole line 1 is taken as an example and described in detail. The direct current breaker wiring circuit connected with the outdoor pole wire 1 comprises a direct current breaker DCCB1, a direct current breaker overhaul circuit, a direct current lightning arrester DB1, a fourth grounding switch QS04 and a direct current measuring device CT 5. The direct current breaker overhaul circuit is connected with a direct current breaker DCCB 1; one end of a direct current breaker DCCB1 is connected with the other side of the direct current bus bar, and the other end of the direct current breaker DCCB1 is connected with an outdoor polar line 1 electric main wiring circuit through a direct current measuring device CT 5. A direct current lightning arrester DB1 and a fourth grounding switch QS04 are arranged in parallel on a line between the other end of the direct current breaker DCCB1 and the direct current measuring device CT5, and one ends of the direct current lightning arrester DB1 and one end of the fourth grounding switch QS04 are both grounded.
In a preferred embodiment, the dc breaker service circuit includes a fifth ground knife QS3, a disconnector Q3 with a single ground knife QS3, a disconnector Q4 without a ground knife, a sixth ground knife QS5 and a disconnector Q5 with a single ground knife QS 5. A disconnecting switch Q3 with a single grounding knife QS3 is connected in series to a line between the direct current breaker DCCB1 and the direct current bus bar, and a fifth grounding knife QS3 is connected in parallel to a line between the disconnecting switch Q3 with the single grounding knife QS3 and the direct current breaker DCCB 1. A disconnecting switch Q5 with a single grounding knife QS5 is connected in series on a line between the DC circuit breaker DCCB1 and the DC current measuring device CT5, and a sixth grounding knife QS5 is connected in parallel on a line between a disconnecting switch Q5 with a single grounding knife QS5 and the DC circuit breaker DCCB 1; one ends of the fifth grounding knife QS3 and the sixth grounding knife QS5 are grounded. A disconnector Q4 without a earthing switch is bridged across disconnector Q3 with single earthing switch QS3 and disconnector Q5 with single earthing switch QS 5.
In a preferred embodiment, the dc measuring devices CT5 and CT6 are of a bushing type construction, disposed within the first pole wall bushing B3 and the second pole wall bushing B4, respectively.
In the above embodiments, the converter is based on a modular multilevel converter (as shown in fig. 3).
In the above embodiments, the selection of the disconnecting switch, the grounding switch and the circuit breaker should take safety and economic principles into consideration: (1) in order to ensure the overhaul safety of personnel, electrical appliances and buses, obvious electrical breaking points and grounding points are provided during overhaul; (2) the number and the positions of the grounding switches are reasonably arranged, and the economical efficiency is ensured. In the main connection circuit, the grounding switches QS01, QS02 and QS03 are all side wall type grounding switches.
In the above embodiments, the arrangement of the dc arresters LV1, LV2 needs to be consistent with the conclusion of the insulation matching study. The dc arresters LV1, LV2 in the valve hall adopt the following configuration and spatial arrangement for protecting critical equipment: the direct current arrester mainly protects the operation impact between the converter valve and the bridge arm reactance, and the faults needing to be researched comprise other bridge arm faults, antipodal bridge arm faults, valve top faults and the impact of converter transformer valve side faults on the point.
In the above embodiments, the outdoor-pole-1 electric main connection circuit is the same as the outdoor-pole-2 electric main connection circuit, and the outdoor-pole-1 electric main connection circuit is taken as an example to be described in detail. The outdoor pole line 1 electric main connection circuit comprises a direct current limiting reactor SR1, a pole line RI capacitor C1, a current measuring device CT7, a direct current measuring device CT9, a seventh grounding switch QS91, an eighth grounding switch QS92, a third isolating switch Q9 with double grounding switches, a direct current lightning arrester DL11, a direct current voltage measuring device PT3 and a direct current lightning arrester DL 21. One end of a direct current limiting reactor SR1 is connected with the direct current measuring device CT5, and the other end of the direct current limiting reactor SR1 is sequentially connected with the direct current measuring device CT9 and a third isolating switch Q9 with double ground knives in series and is connected with the station 1 through a third isolating switch Q9 with double ground knives. A branch consisting of a polar RI capacitor C1 and a current measuring device CT7 connected in series is arranged in parallel on a line between the dc current measuring device CT9 and the dc current limiting reactor SR1, and one end of the branch is grounded. A direct current arrester DL11 is connected in parallel on a line between the direct current measuring device CT9 and the third double-ground-blade-included isolating switch Q9, a seventh ground blade QS91 and an eighth ground blade QS92 are respectively connected in parallel at two ends of the third double-ground-blade-included isolating switch Q9, and one ends of the direct current arrester DL11, the seventh ground blade QS91 and the eighth ground blade QS92 are grounded. And a direct-current voltage measuring device PT3 and a direct-current lightning arrester DL21 are arranged in parallel on a connecting line of the isolating switch Q9 with the third double-grounding-pole and the station 1, and one ends of the direct-current voltage measuring device PT3 and the direct-current lightning arrester DL21 are grounded.
In summary, when the converter exits operation due to a fault, the operation of the remaining dc power grid should not be affected. A conventional dc breaker configuration system is shown in fig. 4, i.e. a dc breaker is required to be configured in a converter branch on one side of a dc bus bar, because the dc breaker is expensive and the solution is not economical. Compared with the conventional scheme, the invention has the improvement that as shown in fig. 5, the direct current breaker of the current converter branch is changed into a direct current bus fast switch which is an alternating current breaker with direct current voltage withstanding capability. The two ends of the direct current bus fast switch are both provided with grounding switches, and the grounding switches are used for providing obvious grounding points during maintenance and providing a discharge path for charges stored in equipment such as a valve. A direct current bus fast switch is adopted between the current converter and the direct current bus. Such advantages are mainly reflected in: 1) the direct-current bus fast switch has certain voltage resistance and arc discharge capacity, so that the converter has an online switching function, and the direct-current bus fast switch has better economical efficiency compared with a conventional direct-current circuit breaker scheme; 2) the action time (opening) of the breaker is about 40ms, and the power failure time caused by the converter fault is greatly shortened.
Based on the main connection system, the invention also provides an online maintenance method for the main connection of the polar electricity of the bipolar flexible direct-current power grid, which aims at the online maintenance of the direct-current circuit breaker and takes the maintenance of the direct-current circuit breaker DCCB1 as an example, and the method comprises the following steps:
1) closing the isolating switch Q4 without the ground knife;
2) opening the dc breaker DCCB 1;
3) disconnecting an isolating switch Q3 with a single grounding knife QS3 and an isolating switch Q5 with a single grounding knife QS 5;
4) closing a fifth earthing switch QS3 and a sixth earthing switch QS 5;
5) in the maintenance process of the DC circuit breaker DCCB1, pole line current flows from a bypass isolating switch Q4 without a grounding switch, and the on-line maintenance and transmission power of the pole line DC circuit breaker are not interrupted.
In summary, the flexible dc power grid line electrical main wiring system provided in this embodiment meets the requirements of different modes of switching, insulation matching requirements, control protection measurement requirements, and the like; the system has the characteristics of less required equipment, high economy and the like; the direct current bus rapid switching scheme saves a direct current breaker, has low equipment manufacturing cost, has the advantages of simplicity, clarity, convenience, easiness and the like in the direct current breaker online maintenance step, and accordingly improves the reliability and the availability of the flexible direct current power grid. The method has important development significance for the development of the flexible direct-current power grid.
The above embodiments are only for illustrating the present invention, and the structure, size, arrangement position and steps of each component can be changed, and on the basis of the technical scheme of the present invention, the improvement and equivalent transformation of the individual components and steps according to the principle of the present invention should not be excluded from the protection scope of the present invention.
Claims (7)
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| CN110896225B (en) * | 2019-11-29 | 2021-08-03 | 南方电网科学研究院有限责任公司 | Method and device for online putting third station of multi-terminal conventional direct-current power transmission system into operation and storage medium |
| CN111211544B (en) * | 2020-02-03 | 2021-07-27 | 国家电网有限公司 | A valve side main equipment configuration and transformer grounding system and using method thereof |
| CN111162558B (en) * | 2020-02-03 | 2021-11-23 | 国家电网有限公司 | Main wiring system of back-to-back symmetrical single-pole flexible-straight system and selection method thereof |
| CN112688288B (en) * | 2020-12-25 | 2024-12-20 | 中国电力工程顾问集团中南电力设计院有限公司 | Overvoltage control and protection method for submodules in symmetrical bipolar flexible DC transmission system |
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