CN108448549B - Flexible direct current line protection method based on current-limiting reactor measurement power - Google Patents

Flexible direct current line protection method based on current-limiting reactor measurement power Download PDF

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CN108448549B
CN108448549B CN201810434904.3A CN201810434904A CN108448549B CN 108448549 B CN108448549 B CN 108448549B CN 201810434904 A CN201810434904 A CN 201810434904A CN 108448549 B CN108448549 B CN 108448549B
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current
line
limiting reactor
measurement power
flexible direct
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CN108448549A (en
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陈卫
李世龙
陈德树
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

The invention discloses a kind of flexible direct current system line protection methods based on current-limiting reactor measurement power, comprising: for a DC line, obtains it and measures electric current;For being installed on the current-limiting reactor of DC line one end, according to its inductance and measurement electric current, the measurement power of the induced voltage and current-limiting reactor that generate on current-limiting reactor is calculated;If measuring power is greater than adjusting threshold value, DC line is cut off by the protective relaying device of DC line the same end;Otherwise, the protective relaying device of DC line the same end is failure to actuate;Identical judgement is performed both by for the current-limiting reactor at DC line both ends and controls corresponding protective relaying device movement;For two DC lines, identical route protection operation is executed.The present invention can effectively improve the quick-action and reliability of route protection, and provide reliable adjusting foundation for adjusting threshold value.

Description

Flexible direct current line protection method based on current-limiting reactor measurement power
Technical field
The invention belongs to electric power system and its automation fields, are measured more particularly, to one kind based on current-limiting reactor The flexible direct current line protection method of power.
Background technique
The high pressure AC and DC system that the structure and operation mechanism of flexible direct current system make its line fault aspect ratio traditional Failure is increasingly complex, and therefore, the route protection of flexible direct current system is one of the key element of flexible direct current system development.Mesh Before, flexible direct current route protection is mainly referred from the traveling-wave protection in conventional high-tension direct current system.After traveling-wave protection utilizes failure The travelling wave signal generated after line fault passes through emulation establishing protective criterion.Failure equivalent can be thought according to superposition theorem after failure A reverse fault component is superimposed at point, voltage and current traveling wave is propagated with the speed of the approximate light velocity to route both ends, this traveling wave is Anti- traveling wave.Traveling-wave protection applies to flexible DC transmission route mostly as main protection.Traveling-wave protection utilizes transient information structure At, can fast movement after a failure, but lack complete strict theoretical foundation in adjusting, and will receive transition resistance influence, In addition, to protective device sample rate, there are also higher requirements.
Full control power electronic devices in flexible direct current system inverter due to being limited by technical level, it is unbearable compared with Big failed shorted electric current.Therefore the traveling-wave protection for applying to conventional high-tension DC line is deposited in terms of quick-action and reliability In defect, the performance requirement of flexible direct current system route protection can not be fully met.
Summary of the invention
In view of the drawbacks of the prior art and Improvement requirement, the present invention provides a kind of based on current-limiting reactor measurement power Flexible direct current system line protection method, it is intended to solve existing flexible direct current system line protection method quick-action and reliability The problem of insufficient and adjusting threshold value lacks reliable adjusting foundation.
To achieve the above object, according to one aspect of the present invention, it provides a kind of based on current-limiting reactor measurement power Flexible direct current system line protection method, include the following steps:
(1) it for a DC line, obtains it and measures electric current
(2) for being installed on the current-limiting reactor of DC line one end, according to its inductance L and measurement electric currentIt calculates The induced voltage generated on to current-limiting reactorAnd the measurement power of current-limiting reactor is further calculated
(3) if measurement powerGreater than adjusting threshold value sset, then determine that failure is located at the inside of the DC line;If Measure powerLess than or equal to adjusting threshold value sset, then determine that failure is located at the outside of DC line;
(4) if failure is located at the inside of DC line, then by being installed on DC line with current-limiting reactor by determining The protective relaying device of the same end cuts off DC line;Otherwise, the relay of DC line the same end is installed on current-limiting reactor Protective device is failure to actuate;
(5) for being installed on the current-limiting reactor at DC line both ends, step (2)~(4) are executed respectively;
(6) for the positive DC route of flexible direct current system and negative DC route, step (1)~(5) are executed respectively, To realize the protection to two DC lines.
Further, in step (3), threshold value s is adjustedsetAdjusting foundation are as follows:
sset=krel×send
Wherein, krelFor safety factor, sendCurrent-limiting reactor measures power when for DC line end DC bus fault Maximum value, and measure power maximum value sendIt is to be obtained by carrying out modeling analysis to the discharge loop after DC line fault It arrives.
Further, rule of thumb, safety factor krelValue range be 1.1~1.3.
Further, in step (2), induced voltageCalculation formula are as follows:
Further, in step (2), power is measuredCalculation formula are as follows:
In general, contemplated above technical scheme through the invention, can obtain it is following the utility model has the advantages that
(1) the flexible direct current system line protection method provided by the invention based on current-limiting reactor measurement power, from event The angle that power shifts after barrier is set out, and judges the position of line fault point according to the measurement power of current-limiting reactor, and control phase The protective relaying device answered is acted to realize the protection to DC line.On the one hand, putting after DC line internal fault is formed Electrical circuit time constant is minimum, and the power of current-limiting reactor can reach peak value in a very short period of time, and therefore, this method can The position for judging fault point rapidly after line fault generation, effectively increases the quick-action of route protection.On the other hand, direct current When line-internal failure and external fault, the measurement power of corresponding current-limiting reactor is by apparent difference, according to current limliting electricity The measurement power of anti-device judges the specific location of fault point, can effectively improve the accuracy of breakdown judge, and further increase The reliability of route protection.
(2) the flexible direct current system line protection method provided by the invention based on current-limiting reactor measurement power, passes through DC line end DC bus fault time limit galvanic electricity is obtained to modeling analysis is carried out to the discharge loop after DC line fault The maximum value of anti-device measurement power, and the thus adjusting foundation of construction adjusting threshold value, thus mention to adjust the adjusting of threshold value Reliable theoretical foundation has been supplied, and has further improved the reliability of route protection.
(3) the flexible direct current system line protection method provided by the invention based on current-limiting reactor measurement power, for All current-limiting reactors on one DC line are performed both by identical fault verification and are controlled according to judgement result corresponding Protective relaying device movement.The judgement result of multiple current-limiting reactors is almost the same on same DC line, it is thus possible to superfluous Remaining mode protects same DC line, has further ensured the reliability of route protection.
In general, the flexible direct current system route protection side provided by the invention based on current-limiting reactor measurement power Method effectively increases the quick-action and reliability of route protection, and provides reliable adjusting foundation for adjusting threshold value.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of existing flexible HVDC transmission system;
Fig. 2 is the topological comparative diagram of two kinds of inverters of existing flexible direct current system;(a) for two level VSC-HVDC's Inverter topology diagram;(b) the inverter topological diagram for being MMC-HVDC;
Fig. 3 is the flexible direct current system route protection side provided in an embodiment of the present invention that power is measured based on current-limiting reactor The flow chart of method;
Fig. 4 is the equivalent discharge loop figure after flexible direct current system line-internal failure;
Fig. 5 is current-limiting reactor measurement changed power three-dimensional figure after flexible direct current system line-internal failure;
Fig. 6 is the equivalent discharge loop figure after flexible direct current system direct current bus-bar fault;
Fig. 7 is current-limiting reactor measurement changed power curve figure after flexible direct current system direct current bus-bar fault;
Fig. 8 is equivalent circuit diagram after MMC-HVDC failure;It (a) is the equivalent circuit diagram of preliminary abbreviation;It (b) is furtherization The equivalent circuit diagram of discharge loop after letter.
Specific embodiment
In order to make the objectives, technical solutions, and advantages of the present invention clearer, with reference to the accompanying drawings and embodiments, right The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and It is not used in the restriction present invention.As long as in addition, technical characteristic involved in the various embodiments of the present invention described below Not constituting a conflict with each other can be combined with each other.
Flexible HVDC transmission system used at present can be divided into according to the difference of inverter topology based on voltage source converter VSC-HVDC and MMC-HVDC based on modularization multi-level converter.Typical VSC-HVDC flexible direct current system structural representation Figure is as shown in Figure 1, wherein GNAnd GMFor the AC power source in flexible direct current system, TNAnd TMFor converter power transformer, C1~C4It is straight Bus shunt capacitor is flowed, L is DC line current-limiting reactor, TL1And TL2Respectively flexible DC transmission route anode and Anode circuit.MMC-HVDC and VSC-HVDC inverter topological variation comparison diagram is as shown in Figure 2.Fig. 2 (a) indicates two level VSC- The inverter topology diagram of HVDC exchanges each corresponding upper and lower bridge arm only one IGBT full-controlled device, each IGBT and diodes in parallel composition, cut-offs it by trigger signal and controls.The big electricity in two in parallel of DC bus side Hold, is conducive to the stabilization for exporting DC voltage.Fig. 2 (b) is the inverter topological diagram of MMC-HVDC, and SM indicates converter bridge arm Submodule, each bridge arm are composed in series by several submodules, are furthermore also in series with reactor on bridge arm.Different from VSC- Without bulky capacitor in parallel on the DC bus of HVDC, MMC-HVDC.In addition to shunt capacitance at converter structure and bus, the two direct current Line construction is identical.
At the both ends of each DC line, it is mounted on a current-limiting reactor and a protective relaying device;Current limliting Reactor is the physical boundary of flexible direct current route, and betiding the failure between the current-limiting reactor of route both ends is internal event Barrier needs tripping route both ends breaker to realize fault clearance.Other failures are flexible direct current route external fault, and route both ends are disconnected Road device should not act.
Flexible direct current system line protection method provided by the invention based on current-limiting reactor measurement power, such as Fig. 3 institute Show, includes the following steps:
(1) it for a DC line, obtains it and measures electric current
(2) for being installed on the current-limiting reactor of DC line one end, according to its inductance L and measurement electric currentIt calculates Obtain the induced voltage generated on current-limiting reactorAnd the measurement power of current-limiting reactor is further calculated
(3) if measurement powerGreater than adjusting threshold value sset, then determine that failure is located at the inside of the DC line;If Measure powerLess than or equal to adjusting threshold value sset, then determine that failure is located at the outside of DC line;
(4) if failure is located at the inside of DC line, then by being installed on DC line with current-limiting reactor by determining The protective relaying device of the same end cuts off DC line;Otherwise, the relay of DC line the same end is installed on current-limiting reactor Protective device is failure to actuate;
(5) for being installed on the current-limiting reactor at DC line both ends, step (2)~(4) are executed respectively;
(6) for the positive DC route of flexible direct current system and negative DC route, step (1)~(5) are executed respectively, To realize the protection to two DC lines.
After line failure, by taking VSC-HVDC as an example, equivalent discharge loop is as shown in Figure 4.Wherein R1And L1Respectively event Hinder point to the positive equivalent resistance and inductance (comprising current-limiting reactor inductance and line inductance) between the DC bus of the side M, R2And L2 Respectively anode circuit equivalent resistance and inductance (including current-limiting reactor inductance and line inductance), R3And L3Respectively fault point To the positive route equivalent resistance and inductance (including current-limiting reactor inductance and line inductance) between the DC bus of the side N, RfFor The transition resistance of fault point, RG1And RG2Respectively ground resistance, Uc1~Uc4For DC line two sides positive and negative anodes bus electricity in parallel Discharge loop can be divided into three parts as shown in Figure 4 after monopole failure inside DC line by the voltage in sense.With flexible straight It is analyzed for the positive and negative electrode current of the side Flow Line M, positive electrode current and cathodal current mainly have discharge loop 1 and discharge loop Loop current in 2 determines.The loop current for solving circuit 1 and circuit 2 need to write the differential equation to three discharge loops whole column, Circuit 1 can be arranged and write equation:
Circuit 2 can be arranged and write equation:
Circuit 3 can be arranged and write equation:
Wherein, ipFor the positive electrode current of the side DC line M, iNFor the side DC line M cathodal current, ipNFor DC line N The positive electrode current in side;
To simplify the calculation, in the case where transition resistance and ground resistance are zero, direct current after positive electrode fault can be respectively obtained The positive electrode current general solution of the side route M are as follows:
Wherein:
The primary condition of discharge loop 1 are as follows:
Uc1(0-) it is capacitor C1 Initial Voltage Value before failure, Ip(0-) it is electrode line road PRE-FAULT CURRENT initial value.
And then available A1、A2Expression formula:
By A1、A2Bring formula (4) into, this makes it possible to obtain positive line current iPAnalytical expression are as follows:
Wherein:
Model is established for discharge loop shown in Fig. 4, is adjusted with verifying in line protection method provided by the present invention Threshold value adjusts the reliability of foundation, and design parameter is as shown in table 1:
1 system parameter of table
In the system parameter shown in table 1, Uc1(0)、Uc2(0)、Uc3(0)And Uc4(0)Respectively Uc1~Uc4It is first before failure Initial value.
Based on the model established, the three of changed power situation on the current-limiting reactor after the generation of DC line internal fault It is as shown in Figure 5 to tie up surface chart.Time shaft is the time change after DC line internal fault occurs.As shown in Figure 5, when flexible straight In streaming system when no fault occurs, the power on electric current reactor is zero.After DC line internal fault occurs, current-limiting reactor Power on device can reach peak value in a short time.Fault point closer, current-limiting reactor at a distance from route head end protection installation place The maximum value of produced power is bigger on device.When DC line internal fault betides route head end, produced on current-limiting reactor Raw maximum power is 600MVA.When DC line internal fault betides DC line end, the measurement of current-limiting reactor Power is 73MVA.
By taking positive DC route N side bus failure as an example, the equivalent discharge loop after failure is as shown in fig. 6, Re1And Le1Point Positive equivalent resistance and inductance not between the DC bus of fault point to the side M (include current-limiting reactor inductance and line electricity Sense), Re2And Le2Respectively anode circuit equivalent resistance and inductance (including current-limiting reactor inductance and line inductance), ReGIt is big Ground resistance.It can arrange and write differential equation group similar with DC line internal fault current-limiting reactor after DC bus fault is measured Power is calculated.On the left of the positive route of the flexible HVDC transmission system shown in Fig. 1 for current-limiting reactor, positive route point Changed power situation Fa Sheng not be measured as shown in two curves in Fig. 7 after the short circuit of left and right side DC bus.AC line When the external fault of road, current-limiting reactor measures the maximum value of power in 40MVA or so.After being significantly less than DC line internal fault Current-limiting reactor measures power minimum (73MVA).Therefore route protection criterion can be constructed using this difference.
For MMC-HVDC, equivalent circuit diagram is as shown in Figure 8 after DC Line Fault.Preliminary abbreviation equivalent circuit diagram such as Fig. 8 (a) It is shown, CL1-CL6The equivalent electric capacitor of each phase upper and lower bridge arm when occurring for failure, with submodule number input by fifty-fifty bridge arm It is related, but the equivalent total capacitance of each phase bridge arm is identical.L1~L6For bridge arm current-limiting reactor, Lp, LnRespectively anode and negative line Road current-limiting reactor, ZLFor line equivalent impedance.Discharge loop can still be equivalent to rlc circuit after further abbreviation, such as Fig. 8 (b) It is shown, wherein CeqTo simplify the equivalent capacity in circuit, LeqTo simplify the equivalent inductance in circuit.It is known initial by solving The differential equation of condition can solve be out of order after route current-limiting reactor measurement power.When position of failure point difference, shown in Fig. 7 etc. Effect discharge loop in equivalent line impedance change, and other parameters be then it is fixed, determined by MMC-HVDC system parameter. Discharge loop after the VSC-HVDC failure of comparison previous analysis, still after failure from the perspective of capacitive energy transfer.Although Bridge arm reactor is increased in the discharge loop of MMC-HVDC system, it can distribution to being obtained on route current-limiting reactor after failure Performance number impacts, but proportionate relationship between the two is fixed.In DC line area and on current-limiting reactor after external area error Measurement power has notable difference, consistent with VSC-HVDC analysis result.
Based on above-mentioned analysis, it is known that the flexible direct current system line provided by the present invention based on current-limiting reactor measurement power Road guard method, by female to DC line end direct current is obtained to the discharge loop progress modeling analysis after DC line fault The maximum value of current-limiting reactor measurement power when line failure, and the thus adjusting foundation of construction adjusting threshold value, can be reliable The position for determining fault point in flexible direct current system, to improve the reliability of route protection.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to The limitation present invention, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should all include Within protection scope of the present invention.

Claims (3)

1. a kind of flexible direct current system line protection method based on current-limiting reactor measurement power, which is characterized in that including such as Lower step:
(1) it for a DC line, obtains it and measures electric current
(2) for being installed on described DC line one end current-limiting reactor, according to its inductance L and the measurement electric currentIt calculates Obtain the induced voltage generated on the current-limiting reactorAnd the measurement power of the current-limiting reactor is further calculated
(3) if the measurement powerGreater than adjusting threshold value sset, then determine that failure is located at the inside of the DC line;If The measurement powerLess than or equal to adjusting threshold value sset, then determine that failure is located at the outside of the DC line;
(4) if by determining, failure is located at the inside of the DC line, then described by being installed on the current-limiting reactor The protective relaying device of DC line the same end cuts off the DC line;Otherwise, with the be installed on institute of the current-limiting reactor The protective relaying device for stating DC line the same end is failure to actuate;
(5) for being installed on the current-limiting reactor at the DC line both ends, step (2)~(4) are executed respectively;
(6) for the positive DC route of flexible direct current system and negative DC route, step (1)~(5) are executed, respectively with reality Now to the protection of two DC lines.
2. the flexible direct current system line protection method as described in claim 1 based on current-limiting reactor measurement power, special Sign is, in the step (3), adjusts threshold value ssetAdjusting foundation are as follows:
sset=krel×Send
Wherein, krelFor safety factor, sendCurrent-limiting reactor measures power when for the DC line end DC bus fault Maximum value, and it is described measurement power maximum value sendIt is by carrying out modeling point to the discharge loop after DC line fault What analysis obtained.
3. the flexible direct current system line protection method as described in claim 1 based on current-limiting reactor measurement power, special Sign is, in the step (2), induced voltageCalculation formula are as follows:And measurement powerCalculation formula Are as follows:
CN201810434904.3A 2018-05-09 2018-05-09 Flexible direct current line protection method based on current-limiting reactor measurement power Active CN108448549B (en)

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JPH1118278A (en) * 1997-06-20 1999-01-22 Hitachi Ltd Bipolar direct current transmission system
CN105305575A (en) * 2015-10-27 2016-02-03 中国科学院电工研究所 Charging method of flexible direct current power transmission converter valve testing device
CN106058828B (en) * 2016-07-18 2018-05-15 天津大学 A kind of multiterminal flexible direct current power network line direction pilot protection method
CN106684837A (en) * 2016-12-13 2017-05-17 华北电力大学 Range-finding protection method of flexible DC line
CN107039993B (en) * 2017-04-20 2019-12-27 国网福建省电力有限公司 Power band-turning control method for symmetrical bipolar flexible direct-current transmission converter
CN107370174A (en) * 2017-06-29 2017-11-21 国家电网公司 A kind of HVDC transmission system simplifies modeling method
CN107681682B (en) * 2017-10-25 2020-10-09 国家电网公司 Alternating current-direct current system equivalence method based on WARD equivalence

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