CN108054736B - A kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave - Google Patents
A kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave Download PDFInfo
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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
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Abstract
The multiterminal flexible direct current power grid DC line protection method based on voltage pole wave that the invention discloses a kind of; the voltage responsive characteristic of faulty line and non-fault line at line boundary when this method analyzes DC line fault; transient voltage pole wave characteristic amount is extracted using wavelet transformation tool, constructs the internal fault external fault identical criterion based on voltage pole wave amplitude value tag；It is interfered 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 relationship on two-wire line, failure pole identical criterion is constructed.Compared with other protection philosophies, this method movement speed 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 wave.
Background technique
As distributed power generation and DC load proportion rise year by year and the extensive use of power electronic devices,
Flexible direct current electrical power trans mission/distribution system based on voltage source converter by become future global energy internet development main trend 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 converter stations by electricity, and in terms of have clear superiority.For more
Flexible direct current power grid is held, it is a kind of " low inertia, underdamping " system that inertance element is less, can instant response when breaking down
Whole network, zooming fault current propose high requirement to the quick-action of DC line protection.Therefore, it studies
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 its fault current of flexible direct current power grid
Lifting speed is exceedingly fast, and requirement of the DC line to the protection Judging fault time needs more efficient and high speed generally within 3ms
Protection scheme, lot of domestic and foreign scholar have carried out numerous studies in the field.
The prior art utilizes wavelet transformation analysis tool, and the one-terminal data traveling wave for proposing Multi-end flexible direct current transmission route 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 transmission using traveling-wave protection and boundary protection thought, moves
Make speed quickly, but its sensitivity is seriously affected by transition resistance.
The prior art proposes the improvement traveling-wave protection based on pole wave 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 route, is realized inside and outside area using voltage derivative feature
The quick identification of failure, however influence of the DC line of flexible direct current power grid vulnerable to high-frequency interferencing signals such as lightning stroke and noises,
The guard method not can avoid the malfunction produced due to interference.
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 about multiterminal flexible direct current power grid DC line, respectively there is advantage and disadvantage, but still
There is no quick action, interfered etc. by transition resistance and thunder and lightning and influence and the method for high sensitivity.
Summary of the invention
The object of the invention is to solve the above problems, a kind of multiterminal flexible direct current power grid based on voltage pole wave is provided
DC line protection method, this method movement speed 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 adopts the following technical solutions, comprising:
The multiterminal flexible direct current power grid DC line protection method based on voltage pole wave that the invention discloses a kind of, including with
Lower step:
(1) voltage at real-time acquisition DC line protection element, current data；
(2) calculating of voltage pole wave is carried out according to collected voltage, current data；Monitoring voltage pole wave is mutated the 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 wave difference of two neighboring sampled point
Protect entry condition in road；If so, starting route protection, into next step；Otherwise, return step (1)；
(3) Startup time is protected according to step (2), extracts the voltage pole wave Sudden Changing Rate number after protection starts in setting time
According to carrying out wavelet transformation to it, obtain the multiple dimensioned high-low frequency weight of voltage pole wave；
(4) it carries out the internal fault external fault identification based on voltage pole wave height frequency component amplitude: if being identified as troubles inside the sample space, being transferred to
Step (5)；Otherwise, return 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 that lightning stroke is dry
It disturbs, compares positive and negative electrode line voltage distribution pole wave amplitude, carry out the differentiation of failure pole；Otherwise, return step (1)；
(6) after judgement is out of order extremely, protection issues trip command to failure polar curve circuit breaker.
Further, in the step (2), the method for calculating voltage pole wave specifically:
P (t)=Z Δ i (t)-Δ u (t)；
Wherein, Z is the wave impedance of route, Δ i (t) and Δ u (t) be respectively real-time current, voltage with normal operation when it is steady
The difference of state electric current, voltage, i.e. electric current, voltage failure component.
Further, in the step (2), the condition of route protection starting are as follows: the voltage pole wave of two neighboring sampled point
The absolute value of difference is greater than the setting valve of setting.
Further, if the voltage pole wave difference between continuous three sampled points is all satisfied the condition of route protection starting,
Then start route protection.
Further, in the step (3), wavelet transformation is carried out to voltage pole wave Sudden Changing Rate data, calculates voltage pole wave
Wavelet transformation jth layer low frequency component aj(k) and high fdrequency component dj(k), specifically:
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,
Specifically: determine that the criterion of troubles inside the sample space occurs are as follows:
Dj> Dset；
In formula, DsetIt is fixed threshold, according to the maximum transient voltage pole wave that protection may detect that when escaping external area error
Amplitude adjusting；DjIt is the jth layer detail coefficients d of transient voltage pole wave 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,
Specifically:
Wherein, kThFor fixed threshold, EHCorrespond to the sum of the high-frequency energy of the second to the 5th scale for transient voltage pole wave,
ELCorrespond to the low frequency energy of the 6th scale for transient voltage pole wave.
Further, in the step (5), the differentiation of failure pole is carried out specifically:
Define D in the ipsilateral protection element installation place anode of DC line and anode circuitjRatio are as follows:
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.
The invention has the advantages that:
(1) internal fault external fault is identified using the high fdrequency component of transient voltage pole wave, utilize voltage pole wave height low frequency energy ratio
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 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, practical value with higher.
Detailed description of the invention
Boundary 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-frequency characteristic for the transient voltage signal that Fig. 3 is protected when being external area error by fault point to regular link
Curve；
Fig. 4 is protection algorism flow chart of the invention；
Fig. 5 is tetra- end module multilevel converter 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 f1When cathode metal ground fault occurs, this route is protected
Protect R12The 3rd layer of detail coefficients d3 of the voltage pole wave and wavelet decomposition measured.
Fig. 7 (b) is flexible direct current power grid DC line L12Midpoint f1When interpolar metallic short circuit failure occurs, this route is protected
Protect R12The 3rd layer of detail coefficients d3 of the voltage pole wave and wavelet decomposition measured.
Fig. 8 is flexible direct current power grid DC line L12Midpoint f1When lightning stroke interference, lightning fault and short trouble occurs, protect
The voltage pole wave waveform that shield R12 is measured.
Fig. 9 (a) is fault point f outside flexible direct current power grid forward region4When cathode metal ground fault occurs, R is protected12It surveys
The 3rd layer of detail coefficients d3 of voltage pole wave and wavelet decomposition obtained.
Fig. 9 (b) is fault point f outside flexible direct current power grid forward region4When interpolar metallic short circuit failure occurs, R is protected12It surveys
The 3rd layer of detail coefficients d3 of voltage pole wave and wavelet decomposition obtained.
Specific embodiment:
The present invention will be further explained below with reference to the attached drawings.
The invention discloses a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave, such as Fig. 4
It is shown, comprising the following steps:
(1) each DC line protection of flexible direct current power grid acquires the voltage and current at protection element in real time；
(2) DC line protection device is by this route protection installation place voltage and current data of acquisition to carry out voltage
Pole wave calculates, and monitoring voltage pole wave is mutated the moment, at the time of the moment, that is, fault traveling wave reaches protection installation place；According to adjacent two
The pole wave difference of a sampled point judges whether to meet route protection entry condition；If so, starting route protection, entrance are next
Step；Otherwise, return step (1)；
Calculate the concrete mode of voltage pole wave p (t) are as follows:
P (t)=Z Δ i (t)-Δ u (t) (1)
In formula, Z is the wave impedance of route, Δ i (t) and Δ u (t) be respectively real-time current, voltage with normal operation when it is steady
The difference of state electric current, voltage, i.e. electric current, voltage failure component.
Protect start-up criterion are as follows:
| Δ P | > Δset (2)
In formula, Δ P=p (k)-p (k-1) is the pole wave difference in two sampling intervals, and k is sampled point；ΔsetFor adjusting
Value, can take 0.01Ue, UeFor the voltage rating of DC line.If the pole wave difference between continuous three sampled points meets formula (2),
Protection starting, differentiates into consequent malfunction.
(3) Startup time is protected according to step (2), extracts the voltage pole wave Sudden Changing Rate number after protection starts in setting time
According to carrying out wavelet transformation to it, obtain the multilayer low frequency component a of transient voltage pole wave signalj(k) and high fdrequency component dj(k)；
Setting time is 1ms, calculates voltage pole wave wavelet transformation jth layer low frequency component aj(k) and high fdrequency component dj(k)
Concrete mode are as follows:
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 be identified as in area therefore
Barrier, is transferred to step (5)；Otherwise, return 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 interfere know
It is other: if recognition result is not lightning stroke interference, to 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 step (1)；
(6) after judgement is out of order extremely, protection issues trip command to failure polar curve circuit breaker.
In step (4), the process that troubles inside the sample space occurs is determined are as follows:
The high fdrequency component for extracting transient voltage pole wave 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 wave that protection may detect that when escaping external area error
Amplitude adjusting；DjIt is the jth layer detail coefficients d of transient voltage pole wave 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 wave are as follows:
Boundary schematic diagram when being as shown in Figure 1 certain simple flexible direct current power grid DC line fault.UiIndicate AC line
The failure additional supply of fault point, U when ground 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 route 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, there is no variation, then fault 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
The protection installation place of route, fault transient voltage have passed through DC line and two current-limiting reactors, current limliting electricity when external area error
Anti- device forms the boundary of DC line, has an impact to the transmitting of transient voltage signal.
It is illustrated in figure 2 equivalent circuit diagram when DC line external area error, Z1And Z2It is the wave resistance of two DC lines respectively
It is anti-, LxFor current-limiting reactor inductance.It can be obtained from the figure that the transient fault to fault point to normal adjacent lines protection installation place is electric
Press the transmission function of signal are as follows:
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 slope has an apparent turning point in 200Hz or so.Before this point, the curve of low-frequency range
Slope is smaller, and amplitude is higher, shows that the decaying of low-band signal is weaker；After turning point, the slope of curve become it is original about
Twice, amplitude sharply declines, and illustrates that the signal decaying of high band is serious.Therefore, which has retardance high frequency letter
Number ability, and with the raising of signal frequency, retardation is stronger.
Therefore, if troubles inside the sample space occurs for DC line, since fault transient amount does not need to can be directly to by line boundary
Up to protection installation place, there is no the retardances by line boundary element for high fdrequency component；If external area error occurs for route, 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, EHCorrespond to the sum of the high-frequency energy of the second to the 5th scale for transient voltage pole wave,
ELCorrespond to the low frequency energy of the 6th scale for transient voltage pole wave, expression formula difference is as follows:
The principle for carrying out lightning stroke disturbance ecology is as follows:
Lightning wave high fdrequency component is abundant and low frequency component is weaker, when lightning stroke interference and lightning fault occur for route, route
On transient voltage signal contain a large amount of high fdrequency component, and the low frequency component that voltage signal contains when lightning fault will be much higher than
Low frequency component when lightning stroke interference.In addition, when common short trouble occurs for route, also containing a large amount of in transient voltage signal
Low frequency component.
The high-frequency energy and low frequency energy that can extract transient voltage pole wave as a result, according to the ratio between the two ηaIt is dry to constitute lightning stroke
Disturb identical criterion.Work as ηaGreater than threshold value kThWhen, judge that lightning stroke interference occurs, protection is failure to actuate；Work as ηaWhen 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 the differentiation of failure pole
Principle is as follows:
When monopole failure occurs, failure extremely on high-frequency voltage signal non-faulting polar curve road can be transmitted 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 wave will be significantly greater than
Non-faulting extremely on voltage pole wave, for ipsilateral protective device, the detected D on positive route and anode circuitjValue
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 wave that identical amplitude can be generated, for ipsilateral protective device, the D that is detected on positive route and anode circuitj
Value is answered of substantially equal.
Therefore positive and negative anodes circuit voltage pole wave amplitude D is utilizedjThe ratio between ηbConstitute failure pole identical criterion.Define DC line
D on ipsilateral protection installation place anode and anode circuitjRatio are as follows:
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 ηaGreater 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 that bipolar failure occurs.
Flexible direct current power system simulation model is constructed using PSCAD, simulating, verifying is carried out to mentioned method:
1) model and protection seting are established
According to Zhangbei County's flexible direct current network system topology and related parameter, ± 500kV has been built using PSCAD simulation software
The symmetrical bipolar DC grid model of four end MMC, as shown in Figure 5.Converter station uses double -loop control mode, and wherein Changping station is using fixed
DC voltage control, remaining converter station, which uses, determines active power controller；DC line is using overhead transmission line according to frequency model, each route
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 route L12On protection R12For, failure and the lightning stroke that various conditions are arranged in a model are dry
Disturb situation, the validity of the proposed transient voltage pole wave protection of simulating, verifying.This paper sample frequency is 20kHz, chooses protection starting
Data window of the sampled point of 1ms as wavelet transformation after preceding several sampled points and starting, 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.
R12Protected object be route L12, the movement threshold of each element should be adjusted first according to actual track structure.
a、DsetAdjusting.In order to realize the selectivity and sensitivity of protection, adjusting threshold may when need to escape external area error
The maximum D of appearancej.According to Fig. 5, fault point (f outside the forward region nearest from protection should be selected4) and reverse fault point (f5), thus
The bipolar failure of metallicity is set at two respectively, maximum D when two kinds of failure situations can be obtained according to emulation datajIt is 83.It examines
Need to be reliable motionless when the sensitivity protected when considering troubles inside the sample space and external area error, safety factor takes 1.2, determines setting valve
DsetIt is 100.
b、kThAdjusting.To determine the threshold value, in route L12Upper setting lightning stroke interference, lightning fault and short trouble,
Consider the case where being most disadvantageous in protection act, obtains η in various situationsaIt is worth size with the curve of change in location, such as Fig. 6 institute
Show, abscissa is the length that fault point distance protects installation place in figure.
As shown in fig. 6, the threshold value k of lightning stroke disturbance ecology criterion can be setThIt is 7.If ηaValue is greater than 7, then is determined as
Lightning stroke interference；If ηaValue is then determined as troubles inside the sample space less than 7.
2) troubles inside the sample space emulates
Monopolar grounding fault.In route L12On be respectively set anode and cathode monopole metallic earthing failure, fault point is
f1, from R12Installation place 100km, fault moment 1ms.Fig. 7 (a) be positive pole ground fault when R12The transient voltage pole wave detected
Waveform and its wavelet conversion coefficient d3, simulation result are shown in Table 2.
Monopole fault simulation result in 2nd area of table
By Fig. 7 (a) it is found that when monopole failure failure polar curve Lu Jibo variation it is obvious, high fdrequency component d3 also far more than non-therefore
Hinder pole.By data in table 2 it is found that protecting the D measured when plus earth failure and cathode ground faultjValue is much higher than setting valve
Dset, be struck by lightning identical criterion ηaLess than 7, failure pole identical criterion η when plus earth failurebGreater than 1.15, when cathode ground fault
Failure pole identical criterion ηbLess than 0.85, energy correct decision, which has, occurs certain pole monopole failure, and the differentiation result of mentioned method is quasi-
Really.
B, bipolar short trouble.Route L is set12Bipolar metallic short circuit failure, fault point f in generating region1, when failure
Carving is 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 |
By Fig. 7 (b) it is found that the fault transient process of two-wire line is identical when bipolar failure, waveform is almost the same.By table 3
Middle data are it is found that protect the D measured when intereelectrode short-circuit failurejValue is much higher than setting valve Dset, be struck by lightning identical criterion ηaLess than 7, therefore
Hinder pole identical criterion ηbGreater than 0.85 and less than 1.15, protection can correct decision have bipolar failure occur, mentioned 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.Route 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 wave, 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
The bill of lading looks pole wave up and down and protects anti-transition resistance ability with good performance and stronger.
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 when lightning fault
Respectively 15kA and 50kA.Since lightning current is mostly negative polarity, DC line mostly occurs in electrode line by the case where lightning stroke
On the road, therefore lightning stroke interference and lightning fault are set on electrode line road in emulation.To protection R12, in route L12Different positions
It sets and adjacent lines L24、L13The inside and outside lightning stroke interference in upper setting area, lightning fault, fault 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 contain high high fdrequency component, together
When lightning fault and short trouble low frequency component it is also very abundant.By emulating data in table 5 it is found that interfering 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 route, fault moment 1ms.Fig. 9 (a) and (b) are shown
R is protected when 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
By Fig. 9 (a), Fig. 9 (b) it is found that the voltage pole wave when external area error difference compared with troubles inside the sample space is obvious, in area therefore
Polar wave shape high fdrequency component rich in when barrier, and polar wave shape relative smooth when external area error, the width of high fdrequency component
It is worth lower.Data are emulated by table 6 it is found that either out-of-area line road failure or bus-bar fault, either monopole failure be still
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, mentioned 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, propose one
The high frequency content of transient voltage pole wave when failure occurs is utilized in transient voltage pole wave protection scheme of the kind based on one-terminal data, the program
Internal fault external fault is judged, while using the identification lightning stroke interference of the low-and high-frequency energy size relation of pole wave, finally according to positive and negative polar curve
The high frequency content size relation of Lu Jibo identifies failure pole.Protect the single ended data after only needing failure in 1ms, movement speed pole
Fastly.A large amount of simulation results show that the protection scheme can rapidly and accurately identify that internal fault external fault and lightning stroke interfere, and are appropriately determined
Failure pole has stronger anti-transition resistance ability, can be used 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 (3)
1. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave, which is characterized in that including following
Step:
(1) voltage at real-time acquisition DC line protection element, current data；
(2) calculating of voltage pole wave is carried out according to collected voltage, current data；Monitoring voltage pole wave is mutated the moment；According to phase
The pole wave difference of adjacent two sampled points judges whether to meet route protection entry condition；If so, starting route protection, under
One step；Otherwise, return step (1)；
The condition of route protection starting are as follows: the absolute value of the voltage pole wave difference of two neighboring sampled point is greater than the adjusting of setting
Value；If the voltage pole wave difference between continuous three sampled points is all satisfied the condition of route protection starting, start route protection；
(3) according to step (2) route protection Startup time, the voltage pole wave mutation after route protection starts in setting time is extracted
Data are measured, wavelet transformation is carried out to it, obtains the multiple dimensioned high-low frequency weight of voltage pole wave；
(4) it carries out the internal fault external fault identification based on voltage pole wave height frequency component amplitude: if being identified as troubles inside the sample space, being transferred to step
(5)；Otherwise, return step (1)；
Determine the criterion of generation troubles inside the sample space are as follows:
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
Adjusting；DjIt is the jth layer detail coefficients d of transient voltage pole wave p (k)j(k) maximum amplitude, is defined by the formula:
Dj=| dj(k)|max,k∈(1,n)；
(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, anode circuit voltage pole wave amplitude carry out the differentiation of failure pole；Otherwise, return step (1)；
The lightning stroke disturbance ecology based on voltage pole wave height low frequency energy ratio is carried out, specifically:
Wherein, kThFor fixed threshold, EHCorrespond to the sum of the high-frequency energy of the second to the 5th scale, E for transient voltage pole waveLFor
Transient voltage pole wave corresponds to the low frequency energy of the 6th scale；
Carry out the differentiation of failure pole specifically:
Define D in the ipsilateral protection element installation place anode of DC line and anode circuitjRatio are as follows:
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；
(6) after judgement is out of order extremely, protection issues trip command to failure polar curve circuit breaker.
2. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave as described in claim 1,
It is characterized in that, in the step (2), the method for calculating voltage pole wave specifically:
P (t)=Z Δ i (t)-Δ u (t)；
Wherein, Z is the wave impedance of route, stable state electricity when Δ i (t) and Δ u (t) are real-time current, voltage respectively and operate normally
The difference of stream, voltage, i.e. fault component.
3. a kind of multiterminal flexible direct current power grid DC line protection method based on voltage pole wave as described in claim 1,
It is characterized in that, in the step (3), wavelet transformation is carried out to voltage pole wave Sudden Changing Rate data, calculates voltage pole wave wavelet transformation
Jth layer low frequency component aj(k) and high fdrequency component dj(k), specifically:
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.
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| CN109119977B (en) * | 2018-09-20 | 2019-07-23 | 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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| CN112269102B (en) * | 2020-10-15 | 2023-05-02 | 合肥工业大学 | Method for detecting direct current short circuit fault of MMC-HVDC based on transient energy |
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| CN112881789B (en) * | 2021-04-08 | 2022-07-08 | 中车青岛四方机车车辆股份有限公司 | Overvoltage signal identification method, device, medium and vehicle |
| CN113381391B (en) * | 2021-05-21 | 2022-05-31 | 广西大学 | Single-end protection method for high-voltage direct-current transmission line |
| CN113612205B (en) * | 2021-07-09 | 2022-11-04 | 天津大学 | MMC-HVDC transient state quantity protection method capable of identifying lightning stroke interference |
| CN114825284A (en) * | 2021-11-30 | 2022-07-29 | 长沙理工大学 | Flexible direct-current power grid fault line isolation method, protection device and system based on forward shot pre-action of direct-current circuit breaker |
| CN114520500B (en) * | 2022-02-15 | 2023-01-17 | 山东大学 | Flexible direct current power grid power transmission line protection and lightning stroke recognition method and system |
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