CN108054736A - A kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple - Google Patents
A kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple Download PDFInfo
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- CN108054736A CN108054736A CN201711207344.XA CN201711207344A CN108054736A CN 108054736 A CN108054736 A CN 108054736A CN 201711207344 A CN201711207344 A CN 201711207344A CN 108054736 A CN108054736 A CN 108054736A
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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
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
Abstract
The invention discloses a kind of multiterminal flexible direct current power grid DC line protection methods based on voltage pole ripple; faulty line and voltage responsive characteristic of the non-fault line at line boundary when this method analyzes DC line fault; using wavelet transformation instrument extraction transient voltage pole wave characteristic amount, the internal fault external fault identical criterion based on voltage pole wave amplitude value tag is constructed；It is disturbed for lightning stroke, establishes the lightning stroke identical criterion of voltage pole wave height low frequency energy ratio；According to the voltage pole wave amplitude relation on two-wire line, failure pole identical criterion is constructed.Compared with other protection philosophies, this method responsiveness is very fast, avoids the influence of lightning stroke disturbance, and anti-transition resistance ability is stronger, high sensitivity.
Description
Technical field
The present invention relates to multiterminal flexible direct current power grid DC line protection technical fields more particularly to one kind to be based on voltage pole
The multiterminal flexible direct current power grid DC line protection method of ripple.
Background technology
As distributed power generation and DC load proportion rise and the extensive use of power electronic devices year by year,
Flexible direct current electrical power trans mission/distribution system based on voltage source converter by as the main trend of future global energy internet development it
One.Wherein multiterminal flexible direct current power grid is the research application hot spot in direct current transportation field, it realizes multiple feed and falls more
Point is saved the operating cost in the case of more current conversion stations, and possesses clear superiority in power supply reliability etc. by electricity.For more
Flexible direct current power grid is held, inertance element is less, is a kind of " low inertia, underdamping " system, can instant response when breaking down
Whole network, zooming fault current propose the quick-action of DC line protection high requirement.Therefore, study
The superfast route protection of multiterminal flexible direct current power grid has important engineering value.
High-voltage dc transmission electrical domain has mainly been continued to use in research currently for the Main Protection of multiterminal flexible direct current power grid
Protection scheme, including two class principle of traveling-wave protection and differential under-voltage protection.But due on flexible direct current power grid its fault current
Lifting speed is exceedingly fast, and requirement of the DC line to the protection Judging fault time is generally within 3ms, it is necessary to more efficient and high speed
Protection scheme, lot of domestic and foreign scholar have carried out numerous studies in the field.
The prior art utilizes wavelet transformation analysis instrument, it is proposed that the one-terminal data traveling wave of Multi-end flexible direct current transmission circuit is protected
Shield scheme, but for influence factors such as transition resistance, abort situation the considerations of is less.
The prior art proposes the guard method for flexible DC power transmission using traveling-wave protection and boundary protection thought, moves
Make speed quickly, but its sensitivity is seriously affected be subject to transition resistance.
The prior art proposes the improvement traveling-wave protection based on pole ripple change rate, has studied sample rate to protection sensitivity
It influences, however, to ensure that the sensitivity of the protection scheme, for the more demanding of sample rate.
The border-differential that the prior art is formed by reactor between circuit, is realized using voltage derivative feature inside and outside area
The quick identification of failure, however the AC line Louis of flexible direct current power grid is influenced by high-frequency interferencing signals such as lightning stroke and noises,
The guard method can not be avoided due to the malfunction of interference production.
The prior art propose using multiple one-terminal datas carry out fault distinguishing protection scheme, including electric current, voltage it is small
Wave system number and voltage derivative, protection reliability is higher, but algorithm is complicated.
The prior art proposes the overhead transmission line ultra- high speed protection scheme based on voltage change ratio, and protection data window only has
0.25ms, protection speed is exceedingly fast, but does not account for the influence of lightning stroke interference.
The prior art proposes a kind of Multi-end flexible direct current transmission short-time energy protection scheme based on difference current, has
Absolute selectivity, but since the both-end amount of the Sustainable use DC line carries out fault distinguishing, the quick-action of protection is poor.
It can be seen that the existing guard method on multiterminal flexible direct current power grid DC line, respectively there is advantage and disadvantage, but still
There is no quick action, the method from the influences such as transition resistance and thunder and lightning interference and high sensitivity.
The content of the invention
The purpose of the present invention is exactly to solve the above problems, and provides a kind of multiterminal flexible direct current power grid based on voltage pole ripple
DC line protection method, this method responsiveness is very fast, avoid lightning stroke disturbance influence, and anti-transition resistance ability compared with
By force, high sensitivity.
To achieve the above object, the present invention uses following technical proposals, including：
The invention discloses a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple, including with
Lower step：
(1) voltage at real-time acquisition DC line protection element, current data；
(2) according to collect voltage, current data carry out voltage pole ripple calculating；It the monitoring voltage pole ripple mutation moment, should
At the time of moment, that is, fault traveling wave reaches protection installation place；Judge whether to meet line according to the pole ripple difference of two neighboring sampled point
Protect entry condition in road；If so, start route protection, into next step；Otherwise, return to step (1)；
(3) Startup time, the voltage pole ripple Sudden Changing Rate number after extraction protection startup in setting time are protected according to step (2)
According to carrying out wavelet transformation to it, obtain the multiple dimensioned high-low frequency weight of voltage pole ripple；
(4) the internal fault external fault identification based on voltage pole wave height frequency component amplitude is carried out：If being identified as troubles inside the sample space, it is transferred to
Step (5)；Otherwise, return to step (1)；
(5) the lightning stroke disturbance ecology based on voltage pole wave height low frequency energy ratio is carried out：If recognition result is not dry for lightning stroke
It disturbs, compares positive and negative electrode line voltage distribution pole wave amplitude, carry out failure pole differentiation；Otherwise, return to step (1)；
(6) judge after being out of order extremely, protect and trip command is sent to failure polar curve circuit breaker.
Further, in the step (2), the method for calculating voltage pole ripple is specially：
P (t)=Z Δ i (t)-Δ u (t)；
Wherein, Z is the wave impedance of circuit, and Δ i (t) and Δ u (t) are steady when being real-time current, voltage and normal operation respectively
The difference of state electric current, voltage, i.e. electric current, voltage failure component.
Further, in the step (2), the condition that route protection starts is：The voltage pole ripple of two neighboring sampled point
The absolute value of difference is more than the setting valve of setting.
Further, if the voltage pole ripple difference between continuous three sampled points is satisfied by the condition of route protection startup,
Then start route protection.
Further, in the step (3), wavelet transformation is carried out to voltage pole ripple Sudden Changing Rate data, calculates voltage pole ripple
Wavelet transformation jth layer low frequency component aj(k) and high fdrequency component dj(k), it is specially：
In formula, k is sampled point, and n is data window length, and h and g are respectively low-pass filter and high-pass filter.
Further, in the step (4), the internal fault external fault identification based on voltage pole wave height frequency component amplitude is carried out,
Specially：Judge occur troubles inside the sample space criterion be：
Dj＞ Dset；
In formula, DsetIt is fixed threshold, according to the maximum transient voltage pole ripple that protection may detect that when escaping external area error
Amplitude is adjusted；DjIt is the jth layer detail coefficients d of transient voltage pole ripple p (k)j(k) maximum amplitude, is defined by the formula：
Dj=| dj(k)|max,k∈(1,n)；
Further, in the step (5), the lightning stroke disturbance ecology based on voltage pole wave height low frequency energy ratio is carried out,
Specially：
Wherein, kThFor fixed threshold, EHThe sum of high-frequency energy for corresponding to the second to the 5th scale for transient voltage pole ripple,
ELCorrespond to the low frequency energy of the 6th scale for transient voltage pole ripple.
Further, in the step (5), carrying out the differentiation of failure pole is specially：
Define DC line homonymy protection element installation place anode and negative line road DjRatio be：
In formula, DjpThe D detected for electrode line roadjValue, DjnThe D detected for negative line roadjValue.
Failure pole identical criterion is as follows：
In formula, η1And η2It is the threshold value of setting.
Advantageous effect of the present invention：
(1) using the high fdrequency component identification internal fault external fault of transient voltage pole ripple, voltage pole wave height low frequency energy ratio is utilized
Value identification lightning stroke interference, using the failure pole of the two poles of the earth voltage pole wave height frequency component amplitude identification troubles inside the sample space, in the sampling of 20kHz
Only need the data window of 1ms that judgement can be completed under frequency, quick-action is strong；
(2) under various failure primary condition it is reliable, rapidly identify troubles inside the sample space, transition resistance, lightning stroke interference and
The factors such as abort situation have little to no effect Protection criteria, and reliability and sensitivity is high；
(3) recognition methods principle is simple, clear, and identification is accurate, is easy to Project Realization, has higher practical value.
Description of the drawings
Border schematic diagram when Fig. 1 is certain simple flexible direct current power grid DC line fault；
Equivalent circuit diagram when Fig. 2 is DC line external area error；
The transmission function amplitude versus frequency characte for the transient voltage signal that Fig. 3 is protected when being external area error by trouble point to regular link
Curve；
Fig. 4 is the protection algorism flow chart of the present invention；
Fig. 5 is tetra- end module multilevel converters of ± 500kV symmetrically bipolar DC grid model；
Fig. 6 is lightning stroke identical criterion ηaValue is with distance change curve；
Fig. 7 (a) is flexible direct current power grid DC line L12Midpoint f1During generation cathode metal earth fault, this circuit is protected
Protect R12The 3rd layer of detail coefficients d3 of the voltage pole ripple and wavelet decomposition measured.
Fig. 7 (b) is flexible direct current power grid DC line L12Midpoint f1During generation interpolar metallic short circuit failure, this circuit is protected
Protect R12The 3rd layer of detail coefficients d3 of the voltage pole ripple and wavelet decomposition measured.
Fig. 8 is flexible direct current power grid DC line L12Midpoint f1When generation lightning stroke interference, lightning fault and short trouble, protect
The voltage pole ripple waveform that shield R12 is measured.
Fig. 9 (a) is trouble point f outside flexible direct current power grid forward region4During generation cathode metal earth fault, R is protected12It surveys
The 3rd layer of detail coefficients d3 of voltage pole ripple and wavelet decomposition obtained.
Fig. 9 (b) is trouble point f outside flexible direct current power grid forward region4During generation interpolar metallic short circuit failure, R is protected12It surveys
The 3rd layer of detail coefficients d3 of voltage pole ripple and wavelet decomposition obtained.
Specific embodiment：
The invention will be further described below in conjunction with the accompanying drawings.
The invention discloses a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple, such as Fig. 4
It is shown, comprise the following steps：
(1) each DC line protection of flexible direct current power grid gathers the voltage and current at protection element in real time；
(2) DC line protection device by this route protection installation place voltage and current data of acquisition carrying out voltage
Pole ripple calculates, the monitoring voltage pole ripple mutation moment, at the time of the moment, that is, fault traveling wave reaches protection installation place；According to adjacent two
The pole ripple difference of a sampled point judges whether to meet route protection entry condition；If so, starting route protection, entrance is next
Step；Otherwise, return to step (1)；
Calculate voltage pole ripple p (t) concrete mode be：
P (t)=Z Δ i (t)-Δ u (t) (1)
In formula, Z is the wave impedance of circuit, and Δ i (t) and Δ u (t) are steady when being real-time current, voltage and normal operation respectively
The difference of state electric current, voltage, i.e. electric current, voltage failure component.
Protection start-up criterion be：
| Δ P | ＞ Δsset (2)
In formula, Δ P=p (k)-p (k-1), be two sampling intervals pole ripple difference, k is sampled point；ΔsetTo adjust
Value, can take 0.01Ue, UeFor the rated voltage of DC line.If the pole ripple difference between continuous three sampled points meets formula (2),
Protection starts, and differentiates into consequent malfunction.
(3) Startup time, the voltage pole ripple Sudden Changing Rate number after extraction protection startup in setting time are protected according to step (2)
According to carrying out wavelet transformation to it, obtain the multilayer low frequency component a of transient voltage pole ripple signalj(k) and high fdrequency component dj(k)；
Setting time is 1ms, calculates voltage pole ripple wavelet transformation jth layer low frequency component aj(k) and high fdrequency component dj(k)
Concrete mode is：
In formula, k is sampled point, and n is data window length, and h and g are respectively low-pass filter and high-pass filter.
(4) protection is carried out based on voltage pole wave height frequency component amplitude DjInternal fault external fault identification：If it is identified as event in area
Barrier, is transferred to step (5)；Otherwise, return to step (1)；
(5) if being identified as troubles inside the sample space, protection is carried out based on voltage pole wave height low frequency energy ratio ηaLightning stroke interference know
Not：If recognition result is not lightning stroke interference, compare positive and negative electrode line voltage distribution pole wave amplitude, protection is carried out based on positive and negative anodes circuit
Voltage pole wave height frequency component amplitude ratio ηbFailure pole differentiate；Otherwise, return to step (1)；
(6) judge after being out of order extremely, protect and trip command is sent to failure polar curve circuit breaker.
In step (4), the process for judging troubles inside the sample space occurs is：
The high fdrequency component of extraction transient voltage pole ripple is brought using discrete wavelet transformer, passes through voltage pole wave amplitude DjSize is known
Other internal fault external fault；
Dj＞ Dset (4)
In formula, DsetIt is fixed threshold, according to the maximum transient voltage pole ripple that protection may detect that when escaping external area error
Amplitude is adjusted；DjIt is the jth layer detail coefficients d of transient voltage pole ripple p (k)j(k) maximum amplitude, is defined by the formula：
Dj=| dj(k)|max,k∈(1,n) (5)
Internal fault external fault recognition principle based on voltage pole ripple is：
Border schematic diagram when being certain simple flexible direct current power grid DC line fault as shown in Figure 1.UiRepresent AC line
The failure additional supply of fault point, U during earth fault occur for roadoFor the voltage-to-ground of the DC line protection installation place
(i.e. the voltage-to-ground in current-limiting reactor line side), Uo' be adjacent DC line protection installation place voltage-to-ground.It can by figure
Know, after breaking down, the traveling wave propagated to DC line both ends is generated from failure additional voltage source, since traveling wave passes through wave resistance
Catadioptric can occur for the place of resistance, and for this circuit troubles inside the sample space, the fault transient voltage that this route protection detects is only
By DC line, wave impedance is the wave impedance of DC line, is not changed, then trouble point to this route protection installation place
The transmission function of transient voltage signalThe U that wireline inspection arrivesoWith UiIt is little compared to variation；For adjacent lines
The protection installation place on road, fault transient voltage have passed through DC line and two current-limiting reactors, current-limiting reactor during external area error
Device forms the border of DC line, and the transmission of transient voltage signal is had an impact.
It is illustrated in figure 2 equivalent circuit diagram during DC line external area error, Z1And Z2It is the wave resistance of two DC lines respectively
It is anti-, LxFor current-limiting reactor inductance.Trouble point can obtain to the transient fault electricity of normal adjacent lines protection installation place by figure
Pressure signal transmission function be：
It is illustrated in figure 3 the amplitude-versus-frequency curve of transmission function G ' (s).As seen from the figure, the amplitude-frequency of transmission function G ' (s) is bent
Line is in monotone decreasing characteristic, and there are one apparent turning points in 200Hz or so for slope.Before this point, the curve of low-frequency range
Slope is smaller, and amplitude is higher, shows that the attenuation of low-band signal is weaker；After turning point, the slope of curve become it is original about
Twice, amplitude drastically declines, and illustrates that the signal attenuation of high band is serious.Therefore, which has retardance high frequency letter
Number ability, and with the rise of signal frequency, retardation is stronger.
Therefore, if troubles inside the sample space occurs for DC line, since fault transient amount need not be can be directly to by line boundary
Up to protection installation place, high fdrequency component is not blocked be subject to line boundary element；If external area error occurs for circuit, failure is temporary
State amount reaches protection installation place and is required to through boundary element, and deep fades can occur for high fdrequency component.It thus can be by comparing
The size of fault transient high fdrequency component realizes the identification to DC line internal fault external fault.
In step (5), voltage pole wave height low frequency energy ratio η is calculateda：
In formula, kThFor fixed threshold, EHThe sum of high-frequency energy for corresponding to the second to the 5th scale for transient voltage pole ripple,
ELCorrespond to the low frequency energy of the 6th scale for transient voltage pole ripple, expression formula difference is as follows：
The principle for carrying out lightning stroke disturbance ecology is as follows：
Lightning wave high fdrequency component is enriched and low frequency component is weaker, when lightning stroke interference and lightning fault occur for circuit, circuit
On transient voltage signal contain substantial amounts of high fdrequency component, and the low frequency component that voltage signal contains during lightning fault will be far above
Low frequency component during lightning stroke interference.In addition, when common short trouble occurs for circuit, also containing substantial amounts of in transient voltage signal
Low frequency component.
The high-frequency energy and low frequency energy of transient voltage pole ripple are can extract as a result, according to the ratio between the two ηaIt is dry to form lightning stroke
Disturb identical criterion.Work as ηaMore than threshold value kThWhen, judge lightning stroke interference occurs, protection is failure to actuate；Work as ηaDuring less than threshold value, sentence
It is disconnected that troubles inside the sample space occurs.
In step (5), compare positive and negative electrode line voltage distribution pole wave height frequency component amplitude DjSize carries out failure pole differentiation
Principle is as follows：
When monopole failure occurs, failure extremely on high-frequency voltage signal non-faulting polar curve road can be transferred to because of coupling
On, but its numerical value is smaller compared with failure polar curve road.Therefore, in monopole failure failure extremely on voltage pole ripple will be significantly greater than
Non-faulting extremely on voltage pole ripple, for homonymy protective device, the detected D on anode circuit and negative line roadjValue
It can differ larger；When intereelectrode short-circuit failure occurs, since positive and negative polarities line fault process is consistent, theoretically on two-wire line
The transient voltage pole ripple of identical amplitude can be generated, for homonymy protective device, anode circuit and the D that detects of negative line roadj
Value should be of substantially equal.
Therefore positive and negative anodes line voltage distribution pole wave amplitude D is utilizedjThe ratio between ηbForm failure pole identical criterion.Define DC line
Homonymy protects installation place anode and negative line road DjRatio be：
In formula, DjpThe D detected for electrode line roadjValue, DjnThe D detected for negative line roadjValue.
Then failure pole identical criterion is as follows：
In formula, η1And η2For fixed threshold, η is taken1=1.15, η2=0.85.
Work as ηaMore than fixed threshold η1When, judge that anode breaks down；Work as ηaLess than fixed threshold η2When, judge that cathode is sent out
Raw failure；Work as ηaIn η1With η2Between when, judge bipolar failure occurs.
Flexible direct current power system simulation model is built using PSCAD, simulating, verifying is carried out to institute's extracting method：
1) model and protection seting are established
Related parameter is had according to Zhangbei County's flexible direct current network system topological sum, ± 500kV has been built using PSCAD simulation softwares
The symmetrical bipolar DC grid models of four end MMC, as shown in Figure 5.Current conversion station uses double -loop control mode, and wherein Changping station is using fixed
DC voltage control, remaining current conversion station, which uses, determines active power controller；DC line is using overhead transmission line according to frequency model, each circuit
Parameter it is as shown in table 1.
1 DC line parameter of table
| DC line | Length/km | Current-limiting reactor inductance/mH |
| L12 | 205.9 | 200 |
| L13 | 49.6 | 300 |
| L24 | 188.1 | 200 |
| L34 | 208.4 | 200 |
As shown in figure 5, with circuit L12On protection R12Exemplified by, set the failure of various conditions and lightning stroke dry in a model
Situation is disturbed, simulating, verifying puies forward the validity of transient voltage pole ripple protection.This paper sample frequencys are 20kHz, choose protection and start
Data window of the sampled point of 1ms as wavelet transformation after preceding several sampled points and startup, in order to improve the reliability of protection philosophy
With the sensitivity of criterion, the feature for choosing wavelet transformation third layer detail coefficients d3 herein as internal fault external fault identical criterion is believed
Number, corresponding frequency band 625-1250Hz.
R12Protection object be circuit L12, the action threshold of each element should be adjusted first according to actual track structure.
a、DsetAdjust.In order to realize the selectivity of protection and sensitivity, adjusting may when threshold need to escape external area error
The maximum D of appearancej.According to Fig. 5, trouble point (f outside the forward region nearest from protection should be selected4) and reverse fault point (f5), therefore
The bipolar failure of metallicity is set at two respectively, the D of maximum when can obtain two kinds of failure situations according to emulation datajFor 83.It examines
Need to be reliable motionless when considering the sensitivity protected during troubles inside the sample space and external area error, safety factor takes 1.2, determines setting valve
DsetFor 100.
b、kThAdjust.To determine the threshold value, in circuit L12It is upper that lightning stroke interference, lightning fault and short trouble are set,
Consider to be most disadvantageous in the situation of protection act, obtain it is various in the case of ηaIt is worth curve of the size with change in location, such as Fig. 6 institutes
Show, abscissa is the length of trouble point distance protection installation place in figure.
As shown in fig. 6, the threshold value k of lightning stroke disturbance ecology criterion can be setThFor 7.If ηaValue is more than 7, then is determined as
Lightning stroke interference；If ηaValue is less than 7, then is determined as troubles inside the sample space.
2) troubles inside the sample space emulates
Monopolar grounding fault.In circuit L12Upper to set anode and cathode monopole metallic earthing failure respectively, trouble point is
f1, from R12Installation place 100km, fault moment 1ms.R when Fig. 7 (a) is plus earth failure12The transient voltage pole ripple detected
Waveform and its wavelet conversion coefficient d3, simulation result are shown in Table 2.
Monopole fault simulation result in 2nd area of table
From Fig. 7 (a), the Lu Jibo variations of failure polar curve are apparent during monopole failure, high fdrequency component d3 also far more than non-therefore
Hinder pole.The D measured is protected from data in table 2, when plus earth failure and cathode earth faultjValue is far above setting valve
Dset, lightning stroke identical criterion ηaLess than 7, failure pole identical criterion η during plus earth failurebMore than 1.15, during cathode earth fault
Failure pole identical criterion ηbLess than 0.85, energy correct decision, which has, occurs certain pole monopole failure, and the differentiation result of institute's extracting method is accurate
Really.
B, bipolar short trouble.Circuit L is set12Bipolar metallic short circuit failure, trouble point f in generating region1, during failure
It carves as 1ms.R is protected at this time12Shown in the transient voltage polar wave shape and its wavelet conversion coefficient d3 such as Fig. 7 (b) detected, emulation
It the results are shown in Table 3.
Monopole fault simulation result in 3rd area of table
| Fault type | Position | D3p | D3n | ηa | ηb | Recognition result |
| Intereelectrode short-circuit | f1 | 351.5 | 351.5 | 3.00 | 1.00 | Bipolar failure |
From Fig. 7 (b), the fault transient process of two-wire line is identical during bipolar failure, and waveform is basically identical.By table 3
Middle data are understood, the D measured is protected during intereelectrode short-circuit failurejValue is far above setting valve Dset, lightning stroke identical criterion ηaLess than 7, therefore
Hinder pole identical criterion ηbMore than 0.85 and less than 1.15, protection can correct decision have bipolar failure occur, institute's extracting method is sentenced
Other result is accurate.
3) simulation and analysis of different faults primary condition
Troubles inside the sample space analysis of Influential Factors.Circuit L is set12Troubles inside the sample space investigates different faults distance, different transition resistances
Influence to Protection criteria.Fault condition and simulation result are shown in Table 4, R in tablefFor fault resistance.
Internal fault simulation result under 4 different distance of table and transition resistance
The simulation result of table 4, which shows that transition resistance and fault distance generate the amplitude of pole ripple, centainly to be influenced, but for
Monopole and interpolar failure through 300 Ω transition resistances occur for line end, and Protection criteria still has enough sensitivity.Therefore, institute
Bill of lading looking somebody up and down pole ripple protection has good performance and stronger anti-transition resistance ability.
4) lightning stroke interference is emulated with fault lightning stroke
Lightning stroke simulation model uses general biexponential model, setting lightning stroke interference and amplitude of lightning current during lightning fault
Respectively 15kA and 50kA.Since lightning current is mostly negative polarity, the situation that DC line is struck by lightning mostly occurs in electrode line
On the road, therefore lightning stroke interference and lightning fault are set on electrode line road in emulation.To protecting R12, in circuit L12Different positions
It puts and adjacent lines L24、L13The inside and outside lightning stroke interference in upper setting area, lightning fault, trouble point f6、f1、f7、f2、f3, wherein f6With
F7 is from protection R12Respectively 10km and 200km, generation moment are 1ms.Fig. 8 gives R12Detect lightning stroke interference, lightning stroke in area
The typical polar wave shape of failure, and compared with the typical waveform of area's internal short-circuit failure, other simulation results are shown in Table 5.
The lightning stroke simulation result of table 5
As shown in Figure 8, lightning stroke interference and lightning fault mutation waveform are very sharp, all containing high high fdrequency component, together
When lightning fault and short trouble low frequency component it is also very abundant.From emulating data in table 5, disturbed for being struck by lightning inside and outside area
And lightning fault, each Protection criteria can correct response, simulation result show this method can effectively identify lightning stroke interference, have compared with
High reliability.
5) external area error emulates
Respectively in adjacent DC line L24、L13With plus earth and bipolar short trouble are set on adjacent dc bus, therefore
Barrier point is f2、f3、f4And f5, wherein f2、f3In the exit of respective circuit, fault moment 1ms.Fig. 9 (a) and (b) are shown
R is protected during external area error12Detect most typical transient voltage polar wave shape and its wavelet conversion coefficient d3, external area error
Simulation result is shown in Table 6.
6 external area error simulation result of table
From Fig. 9 (a), Fig. 9 (b), the voltage pole ripple during external area error difference compared with troubles inside the sample space is apparent, in area therefore
Polar wave shape during barrier contains abundant high fdrequency component, and polar wave shape relative smooth during external area error, the width of high fdrequency component
It is worth relatively low.Data, either out-of-area line road failure or bus-bar fault, either monopole failure are emulated still from table 6
Bipolar failure protects the D measuredjValue is far below setting valve Dset, energy correct decision is external area error, and protection can reliably not
Dynamic, institute's extracting method differentiates that result is accurate.
The borderline properties that the present invention is shown using flexible direct current power grid DC line both ends current-limiting reactor, it is proposed that one
The high frequency content of transient voltage pole ripple when kind of the transient voltage pole ripple protection scheme based on one-terminal data, the program make use of the failure to occur
Judge internal fault external fault, while using the low-and high-frequency energy magnitude relationship identification lightning stroke interference of pole ripple, finally according to positive and negative polar curve
The high frequency content magnitude relationship identification failure pole of Lu Jibo.Protection only needs the single ended data in 1ms, responsiveness pole after failure
Soon.A large amount of simulation results show that the protection scheme can rapidly and accurately identify that internal fault external fault is disturbed with lightning stroke, are appropriately determined
Failure pole has stronger anti-transition resistance ability, can be as the main protection of multiterminal flexible direct current power grid DC line.
Above-mentioned, although the foregoing specific embodiments of the present invention is described with reference to the accompanying drawings, not protects model to the present invention
The limitation enclosed, those skilled in the art should understand that, based on the technical solutions of the present invention, those skilled in the art are not
Need to make the creative labor the various modifications or changes that can be made still within protection scope of the present invention.
Claims (8)
- A kind of 1. multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple, which is characterized in that including following Step：(1) voltage at real-time acquisition DC line protection element, current data；(2) according to collect voltage, current data carry out voltage pole ripple calculating；The monitoring voltage pole ripple mutation moment；According to phase The pole ripple difference of adjacent two sampled points judges whether to meet route protection entry condition；If so, start route protection, under One step；Otherwise, return to step (1)；(3) according to step (2) route protection Startup time, the voltage pole ripple mutation after extraction route protection starts in setting time Data are measured, wavelet transformation is carried out to it, obtains the multiple dimensioned high-low frequency weight of voltage pole ripple；(4) the internal fault external fault identification based on voltage pole wave height frequency component amplitude is carried out：If being identified as troubles inside the sample space, step is transferred to (5)；Otherwise, return to step (1)；(5) the lightning stroke disturbance ecology based on voltage pole wave height low frequency energy ratio is carried out：If recognition result is not lightning stroke interference, than Calibration, cathode circuit voltage pole wave amplitude carry out failure pole differentiation；Otherwise, return to step (1)；(6) judge after being out of order extremely, protect and trip command is sent to failure polar curve circuit breaker.
- 2. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (2), the method for calculating voltage pole ripple is specially：P (t)=Z Δ i (t)-Δ u (t)；Wherein, Z is the wave impedance of circuit, stable state electricity when Δ i (t) and Δ u (t) are real-time current, voltage and normal operation respectively Stream, the difference of voltage, i.e. fault component.
- 3. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (2), the condition that route protection starts is：The voltage pole ripple difference of two neighboring sampled point it is exhausted To being worth the setting valve more than setting.
- 4. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as claimed in claim 3, It is characterized in that, if the voltage pole ripple difference between continuous three sampled points is satisfied by the condition of route protection startup, starts line It protects on road.
- 5. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (3), wavelet transformation is carried out to voltage pole ripple Sudden Changing Rate data, calculates voltage pole ripple wavelet transformation Jth layer low frequency component aj(k) and high fdrequency component dj(k), it is specially：In formula, k is sampled point, and n is data window length, and h and g are respectively low-pass filter and high-pass filter.
- 6. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (4), in the step (4), carries out the internal fault external fault based on voltage pole wave height frequency component amplitude Identification, specially：Judge occur troubles inside the sample space criterion be：Dj＞ Dset；In formula, DsetIt is fixed threshold, according to the maximum transient voltage pole wave amplitude that protection may detect that when escaping external area error It adjusts；DjIt is the jth layer detail coefficients d of transient voltage pole ripple p (k)j(k) maximum amplitude, is defined by the formula：Dj=| dj(k)|max,k∈(1,n)。
- 7. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (5), carries out the lightning stroke disturbance ecology based on voltage pole wave height low frequency energy ratio, be specially：Wherein, kThFor fixed threshold, EHThe sum of high-frequency energy for corresponding to the second to the 5th scale for transient voltage pole ripple, ELFor Transient voltage pole ripple corresponds to the low frequency energy of the 6th scale.
- 8. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole ripple as described in claim 1, It is characterized in that, in the step (5), carrying out the differentiation of failure pole is specially：Define DC line homonymy protection element installation place anode and negative line road DjRatio be：In formula, DjpThe D detected for electrode line roadjValue, DjnThe D detected for negative line roadjValue.Failure pole identical criterion is as follows：In formula, η1And η2It is the threshold value of setting.
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| CN109119977A (en) * | 2018-09-20 | 2019-01-01 | 山东大学 | Multiterminal flexible direct current power grid DC line fast protection method and system based on single ended voltage |
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