CN107526002B - A kind of HVDC circuit fault distance measurement based on concentric relaxation principle - Google Patents
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Abstract
The invention proposes a kind of HVDC circuit fault distance measurements based on concentric relaxation principle, to solve HVDC DC line fault quick positioning question.The present invention carries out the determination of instantaneous energy ratio using the voltage signal at route both ends through the low frequency component data of WAVELET PACKET DECOMPOSITION, the range function of instantaneous energy ratio and fault distance is constructed accordingly, to realize the positioning of failure.The present invention is influenced influence that is smaller, while can be avoided fault resistance by noise is measured；It the time that measurement end is reached due to not needing measurement traveling wave, is not influenced by synchronised clock；The start and stop that range function calculating is controlled using the index of arrangement entropy difference ratio, can be to avoid the influence disturbed in the case of non-faulting.The present invention simply easily realizes, can accurately realize that DC line fault positions, have stronger practicability and robustness；There is certain reference value to DC line fault ranging.
Description
Technical field
The present invention relates to the technical fields of DC line fault positioning, and in particular to a kind of based on concentric relaxation principle
HVDC circuit fault distance measurement.
Background technique
Important way of the D.C. high voltage transmission as conveying electric energy and bulk power grid interconnection, influence of the failure to power grid are huge
Greatly.In order to ensure the reliability of power supply, the rapid rush-repair of direct current transmission line fault, the fault location of DC power transmission line are realized
It is key factor.Currently, fault distance-finding method is broadly divided into travelling wave ranging and non-travelling wave ranging two major classes, travelling wave ranging is extensive
The method for applying the fault location in AC/DC Power System, is divided into single end distance measurement and both-end distance measuring again.According to travelling wave ranging
Principle it is found that its ranging accuracy dependent on wavefront accurately identify and velocity of wave and wave head reach the measurement end moment
Accurate measurement.The identification of wave head is influenced by factors such as line parameter circuit value, transition resistances.It is multiple at frequency dividing due to containing in traveling wave
The wave velocity difference of the wave of rate, different frequency is larger, therefore the determination of specific frequency velocity of wave is also relatively difficult.For traveling wave
Both-end distance measuring at the time of reaching both ends due to needing to measure traveling wave respectively, will receive the influence of both ends synchronised clock, if surveying
Amount two, end clock is inconsistent, then will lead to positioning and very big error occur.Existing research scholar respectively regarding to the issue above into
It has gone research, has achieved some important research achievements, the characteristics of due to travelling wave ranging inherently, therefore, it is difficult to from essence
On improved.In addition to this, travelling wave ranging is also influenced by sample frequency, proposes very high requirement to sample devices.
In recent years, non-travelling wave ranging thought has obtained certain development, achieves some important research achievements.Based on point
The voltage's distribiuting feature of cloth parameter model of power transmission system realizes that fault location is measured asynchronous and line parameter circuit value by both ends
Probabilistic influence.The difference of voltage time domain waveform based on route different faults point, by calculate voltage related coefficient come
It determines abort situation, is similarly subjected to the influence of the Parameter uncertainties of route.On this basis, existing scholar establishes non-containing measuring
The probabilistic distributed time domain fault location equation of synchronous and line parameter circuit value.Separately there is scholar according to fault traveling wave spectral characteristic
There is corresponding relationship with fault distance, natural frequency deviation angle crucial in fault localization is solved using Artificial Neural Network
To realize the positioning of failure.The two method implements relatively complicated afterwards.Just generally speaking, current non-travelling wave ranging method can
Operability is not strong.
Summary of the invention
For existing ultra-high-tension power transmission line traveling wave fault location, wavefront is difficult to, larger by transition Resistance Influence,
And to the technical problem that sample devices requires high and existing non-travelling wave ranging operability not strong, the present invention proposes that one kind is based on
The HVDC circuit fault distance measurement of concentric relaxation principle is thought on the basis of non-travelling wave ranging research method by concentric relaxation
The inspiration thought realizes the positioning of failure using the method for route both ends instantaneous energy ratio, by can be realized under multifactor impact
The accurate positionin of failure has stronger practicability and robustness.
In order to solve the above-mentioned technical problem, the technical scheme is that a kind of HVDC line based on concentric relaxation principle
Road fault distance-finding method, its step are as follows:
Step 1: successively between the N number of Along ent position setting metallic earthing failure of HVDC DC line, adjacent two o'clock
Between be divided into 10km；
Step 2: rectifier terminal and inversion end in transmission line of electricity are measured respectively based on Wide Area Measurement System and obtain HVDC biography
The voltage traveling wave signal of N number of fault point in defeated line, is obtained 2N voltage traveling wave signal；
Step 3: 2N voltage traveling wave signal is decomposed respectively using wavelet packet decomposition algorithm；
Step 4: after 5 layers of WAVELET PACKET DECOMPOSITION, the low frequency component of 2N voltage traveling wave signal of extraction, i.e., the 5th layer the 0th
Wavelet coefficient
Step 5: the wavelet packet coefficient of the low frequency component of each voltage traveling wave signal is calculated separatelyEnergy:
In formula, m is variable, and l is the number of wavelet packet coefficient, and 2N energy is obtained；
Step 6: the inverter side of N number of Along ent position and the energy ratio of rectification side are calculated separately, N number of energy ratio is obtained
Value k1, k2..., kN；
The energy ratio of inverter side and rectification side are as follows:
In formula, subscript n value be 1,2 ... N, R1、R2It is greater than 0 number；EIFor the instantaneous energy that inverter side measures, ERFor
The instantaneous energy that rectification side measures；
Step 7: one group of data { (k of N number of data point is formed1, d1), (k2, d2) ..., (k2, dN)}；Wherein, d1,
d2... ..., dNFor the distance of the DC line of N number of Along ent positional distance rectification side；
Step 8: it is carried out curve fitting using least square fitting to the data that step 7 obtains, obtains fault localization letter
Number:
D=f (k)；
Wherein, d is fault distance, and f (k) is the energy ratio k of inverter side and rectification side and the function of fault distance.
Judge whether to break down according to the situation of change of arrangement entropy, however, it is determined that break down, then carry out ranging；If no
It is failure, is the microvariations of a normal operation, then without ranging, comprising the following steps:
Step 1: measuring voltage traveling wave signal in the rectifier terminal of transmission line of electricity and inversion end based on Wide Area Measurement System, if
When arranging the index of entropy ratio greater than+15%, then it is determined as system and failure has occurred, utilize fault localization function measurement fault bit
It sets；
Step 2: the voltage traveling wave signal of abort situation rectification side and inverter side is decomposed using wavelet packet decomposition algorithm, is mentioned
The low frequency component of the voltage traveling wave signal of rectification side and inverter side after 5 layers of WAVELET PACKET DECOMPOSITION is taken, and calculates the instantaneous energy of inverter side
Measure EIWith the instantaneous energy E of rectification sideR；
Step 3: inverter side instantaneous energy E is calculatedIWith rectification side instantaneous energy ERRatio obtain energy ratio k, will
Amount brings fault localization function: d=f (k) into than k, obtains fault localization distance d, fault point.
The fast method of the wavelet packet decomposition algorithm are as follows:
Wherein, k ' is time location parameter, and f (t) is a time signal,Indicate i-th of wavelet packet system on jth layer
Number, H, G indicate wavelet decomposition filter, and H is related with scaling function, and G is related with wavelet function；
The restructing algorithm of wavelet packet decomposition algorithm are as follows:
Wherein, j=0,1 ..., n indicate Decomposition order；I=1,2 ..., 2j-1,2j；H, g indicates wavelet reconstruction filter.
The index of the arrangement entropy difference ratio are as follows:
In formula, pec is the arrangement entropy of magnitude of current time series, and T is current cycle, IdFor the electric current letter measured when failure
Number, (t1,t1+ nT) it is electric current from t1Moment is to t1The magnitude of current time sequential value at+nT moment.
The present invention is based on thoughts loose with one heart, propose AC line voltage traveling wave inverter side and rectification under specific frequency
Side instantaneous energy obtains fault localization function by curve matching than realizing Fault Locating Method, in PSCAD emulation platform pair
The various faults state of four machines, two region AC/DC parallel transmission system is emulated, and has stronger practicability and robustness.
The present invention obtains amplitude attenuation characteristic, the substantially relationship directly proportional to frequency, the higher component of frequency by amplitude-frequency characteristic
Decay bigger；The determination of instantaneous energy ratio is carried out using the low frequency component data of WAVELET PACKET DECOMPOSITION, and generally measures noise all
High frequency, thus the present invention by measure noise influenced it is smaller；Fault location is realized based on instantaneous energy ratio method, is avoided
The influence of fault resistance；Fault location is realized according to measurement DC line both ends electric quantity information, when not needing measurement
Between, it is not influenced by synchronised clock；The present invention simply easily realizes, can accurately realize that DC line fault positions, and robustness
Preferably；There is certain reference value to DC line fault ranging.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
It obtains other drawings based on these drawings.
Fig. 1 is flow chart of the invention.
Fig. 2 is the schematic diagram of concentric relaxation principle.
Fig. 3 is five layers of WAVELET PACKET DECOMPOSITION figure.
Fig. 4 is the 5th layer of the 0th wavelet packet coefficient that WAVELET PACKET DECOMPOSITION obtains.
Fig. 5 is four machines, two region AC/DC Power System figure.
Fig. 6 is instantaneous energy ratio k and DC power transmission line d curve matching figure.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, those of ordinary skill in the art are obtained every other under that premise of not paying creative labor
Embodiment shall fall within the protection scope of the present invention.
The basic thought of the concentric loose criterion of electric power system fault is: the electric system of stable operation is considered as calmness
The water surface, failure are regarded as in coccolith investment water.Stone evokes the ripples from level to level centered on putting into point, shadow caused by failure
The amplitude just as ripples is rung, as the increase of distance successively reduces.The criterion has been successfully applied to electric system forced oscillation
In positioning, the concentric Relaxation Law of dissipation energy distribution has been derived.Electric power system fault and electric system forced oscillation are in property
On belong to the disturbance of electric system, there is certain similitude.It is straight to realize that the present invention is based on the thoughts of concentric relaxation criterion
The positioning of Flow Line failure.Relaxation criterion is as shown in Figure 2 in the schematic diagram of fault location with one heart.
For ripples, ideally, the damping action of ripples transmission process is not considered, then the energy that every layer of ripples include
Be it is equal, i.e., the energy of first layer ripples should be equal to the energy of every layer of ripples formed in diffusion process.Based on the theory come
It analyzes DC line fault traveling wave to propagate, traveling wave circulation way and ripples have similitude and difference after DC line fault occurs
Property.Similitude refers to: after failure occurs, traveling wave will be centered on abort situation to external diffusion.Difference mainly has two o'clock:
1) ripples propagation is that all directions are propagated around, and fault traveling wave is due to only having route to be situated between as propagation
Matter, therefore can only be propagated to both ends.If not considering damping action both, i.e., do not decay, for ripples, energy density
Reduce with the increase of the number of plies of ripples, i.e.,In formula, e is energy density, and E is gross energy, and S is ripples
Area.Then for line fault traveling wave, attenuation is equally disregarded, ideally measure and reach the instantaneous energy at both ends and answer phase
Deng being analogous to the concept of Water wave energy density, line fault traveling wave energy density is constant.
2) ripples oscillation only forms a kind of wave of characteristic initially using oscillation center as the center of circle.And line fault initially generates
Traveling wave there is thousands of radio-frequency component, due to the difference of fault traveling wave frequency, decay in communication process and distort not
Together.
Under actual conditions, since route has damping action, the instantaneous energy that measuring terminals measure at both ends generally not phase
It is that the position occurred with failure has certain relationship Deng, the ratio of the two.For uniform transmission line of electricity, if the lucky position of failure
In DC line midpoint, then the instantaneous row wave energy measured by rectification side and inverter side is equal；Since route causes traveling wave energy
Decaying, if failure is located at the midpoint of logicalnot circuit, the instantaneous row wave energy ratio measured by rectification side and inverter side is not 1.By
Contain the wave of multiple frequencies in fault traveling wave, the wave attenuation of various frequencies is again different, therefore the ratio that both causes and failure away from
From relationship it is very complicated.The amplitude-frequency characteristic obtained by transmission function, the present invention choose relatively stable low frequency band frequency conduct
Data are analyzed, the instantaneous energy of the frequency band is calculated.
As shown in Figure 1, a kind of HVDC circuit fault distance measurement based on concentric relaxation principle, its step are as follows:
Step 1: metallic earthing failure successively is set in HVDC DC line N number of Along ent position, is obtained for measuring
The voltage signal of failure.10km is divided between adjacent two o'clock.
The position mark of N number of Along ent is K1、K2、……、KN, corresponding distance, i.e., apart from the AC line of rectification side
Road distance is labeled as d1, d2... ..., dN。
Step 2: rectifier terminal and inversion end in transmission line of electricity are measured respectively based on Wide Area Measurement System and obtain HVDC biography
The voltage traveling wave signal of N number of fault point in defeated line, is obtained 2N voltage traveling wave signal.
Step 3: 2N voltage traveling wave signal is decomposed respectively using wavelet packet decomposition algorithm.
If f (t) is a time signal,Indicate i-th of wavelet packet on jth layer, referred to as wavelet packet coefficient.Wavelet packet point
The fast algorithm of solution are as follows:
Wherein, k ' is time location parameter, and H, G indicate wavelet decomposition filter, and H is related with scaling function, G and small echo letter
Number is related.Restructing algorithm are as follows:
Wherein, j=0,1 ..., n indicate Decomposition order；I=1,2 ..., 2j-1,2j；H, g indicates wavelet reconstruction filter.
It is illustrated in figure 3 five layers of WAVELET PACKET DECOMPOSITION figure.
Step 4: after 5 layers of WAVELET PACKET DECOMPOSITION, the low frequency component of voltage traveling wave signal is extracted.
As shown in figure 4, extracting the 5th layer of the 0th wavelet coefficient, useIt indicates.
Step 5: the energy of the wavelet packet coefficient of the low frequency component of voltage traveling wave signal is calculated separately.
The energy of the wavelet packet coefficient of the low frequency component of each voltage traveling wave signal are as follows:
In formula, m is variable, and l is the number of wavelet packet coefficient, and 2N energy is obtained.
Step 6: the inverter side of N number of Along ent position and the energy ratio of rectification side are calculated separately, N number of energy ratio is obtained
Value k1, k2..., kN。
The energy ratio of inverter side and rectification side are as follows:
In formula, subscript n indicates fault point, and value 1,2 ... N, R are greater than 0 real number.EIThe wink measured for inverter side
Shi Nengliang, ERThe instantaneous energy measured for rectification side.
Step 7: one group of data { (k of N number of data point is formed1, d1), (k2, d2) ..., (kN, dN)}。
By N number of energy ratio k1, k2..., kNWith distance d1, d2... ..., dNCorrespond composition data group { (k1, d1),
(k2, d2) ..., (kN, dN)}。
Step 8: being carried out curve fitting using least square fitting data group, obtains fault localization function:
D=f (k) (5)
Least square fitting is carried out according to the function in the tool box matlab, directly two groups of data input fittings are obtained,
Instantaneous energy ratio k and DC power transmission line d curve matching are as shown in Figure 6.
Arrangement entropy is that it is micro- to be able to reflect signal by the variation of entropy for the average entropy parameter of One-dimension Time Series complexity
Small variation can preferably reflect the failure that electric system is grounded by transition resistance.Its algorithm principle: a time sequence
Every a line regards a reconstruct component as in the matrix x obtained after column X phase space reconfiguration, matrix x, shares l.X is reconstructed into square
Reconstruct component in battle array re-starts arrangement according to ascending order, and the vector X (i) of any one time series composition can be obtained
To a group code sequence S (l), the probability P of each symbol sebolic addressing appearance is calculated1,P2,…,Pl, the l kind of time series X (i) is not
With symbol sebolic addressing arrangement entropy (PE) according to Shannon entropy formal definition be Hp, value range is 0≤Hp≤ 1, it is worth bigger
More irregularly, signal when normal operation is all comparison rule to representation signal sequence, is worth typically small, therefore passes through the change of value
Change, can be realized the detection of failure.
The present invention is by the variation of arrangement entropy to determine whether breaking down, however, it is determined that breaks down, then carries out ranging；
If not failure, the only microvariations of a normal operation, then without ranging.The following steps are included:
Step 1: using the index of arrangement entropy ratio.It is defined as follows:
In formula, pec is the arrangement entropy of magnitude of current time series, and T is current cycle, IdFor the electric current letter measured when failure
Number, (t1,t1+ nT) it is electric current from t1Moment is to t1The magnitude of current time sequential value at+nT moment.For the quantitative identification system failure,
The present invention further defines arrangement entropy difference than index:
Step 2: when arrangement entropy difference is than index K2When greater than+15%, then it can be determined as system and failure has occurred, then utilize
Fault localization function measurement abort situation；The voltage of abort situation rectification side and inverter side is decomposed using wavelet packet decomposition algorithm
Travelling wave signal, extracts the low frequency component of the voltage traveling wave signal of rectification side and inverter side after 5 layers of WAVELET PACKET DECOMPOSITION, and calculates inversion
The instantaneous energy E of sideIWith the instantaneous energy E of rectification sideR；.
Step 3: calculating inverter side instantaneous energy EIWith rectification side instantaneous energy ERRatio obtain energy ratio k, by energy
Fault localization function: d=f (k) is brought into than k, obtains fault localization distance d, obtains fault localization as a result, fault point.
In order to verify effectiveness of the invention and robustness, to more under four machines, two region AC/DC parallel transmission system structure
Kind fault condition is emulated, as shown in figure 5, two district systems are by a direct current, two exchanges are connected system structure.Area
Domain 1 and region 2 are respectively there are two equivalent potential source, when steady-state operation, alternating current circuit list transmission back power Pac1=Pac2=103MW,
Direct current transmission active power is Pdcref=198MW, load PL1=302MW, load PL2=556MW.Control mode is fixed for rectification side
Current control, the control of inverter side constant voltage.The factor of consideration include fault resistance, measure noise, the combination of two kinds of factors with
And the variation of control mode.
1) without measurement noise metallic earthing fault simulation.
1 analysis of simulation result of table
By the simulation result of table 1 it is found that the present invention under different electric network compositions all have stronger robustness.
2) 1 (C of DC control control mode1): rectification side constant current control, the control of inverter side constant voltage；DC control side
2 (C of formula2), rectification side constant current control, inverter side determines the control of the angle δ.
2 analysis of simulation result of table
It can be obtained by table 2, which is not influenced by hvdc control mode, and robustness is stronger.
When due to breaking down in real system operation, the signal of measurement may be simultaneously by two kinds of factors or many factors
It influences.Therefore, it when the present invention selects failure containing transition resistance, containing noise is measured in signal, measures noise and is selected as respectively being distributed
Type, standard deviation are 0.005 (per unit value).Simulation result is shown in Table 3.
3) as shown in table 3 containing measurement noise and transition resistance impact analysis simultaneously.
3 analysis of simulation result of table
The present invention still can be realized the standard of failure under by multifactor impact it can be seen from the simulation result of table 3
Determine position, it was demonstrated that robustness of the invention.
The present invention acquires the Bode diagram of route by the method that transmission function recognizes, by dividing Bode diagram amplitude-frequency characteristic
Analysis, the data decaying for obtaining low frequency component is smaller, therefore amplitude energy is larger, therefore using the data of the frequency band as event
The instantaneous energy ratio k of inverter side and rectification side when barrier；Traveling wave voltage signal is decomposed using the method for WAVELET PACKET DECOMPOSITION, finally
Seek k value.In the N number of Along ent position of route, failure is respectively set, finds out the corresponding relationship of N group k value and line length d, uses
The method of data fitting, obtains the functional relation of k and d, i.e. fault localization function.Finally, by PSCAD to four machines two
The various faults state of region AC/DC parallel transmission system is emulated, and the feasibility and robustness of this method are demonstrated.
The foregoing is merely illustrative of the preferred embodiments of the present invention, is not intended to limit the invention, all in essence of the invention
Within mind and principle, any modification, equivalent replacement, improvement and so on be should all be included in the protection scope of the present invention.
Claims (3)
1. a kind of HVDC circuit fault distance measurement based on concentric relaxation principle, which is characterized in that its step are as follows:
Step 1: being successively arranged metallic earthing failure in the N number of Along ent position of HVDC DC line, between adjacent two o'clock between
It is divided into 10km；
Step 2: rectifier terminal and inversion end in transmission line of electricity are measured respectively based on Wide Area Measurement System and obtain HVDC transmission line
In N number of fault point voltage traveling wave signal, 2N voltage traveling wave signal is obtained；
Step 3: 2N voltage traveling wave signal is decomposed respectively using wavelet packet decomposition algorithm；
Step 4: after 5 layers of WAVELET PACKET DECOMPOSITION, the low frequency component of 2N voltage traveling wave signal, i.e. the 5th layer of the 0th small echo are extracted
Coefficient
Step 5: the wavelet packet coefficient of the low frequency component of each voltage traveling wave signal is calculated separatelyEnergy:
In formula, m is variable, and l is the number of wavelet packet coefficient, and 2N energy is obtained；
Step 6: calculating separately the inverter side of N number of Along ent position and the energy ratio of rectification side, obtains N number of energy ratio k1,
k2..., kN；
The energy ratio of inverter side and rectification side are as follows:
In formula, subscript n value be 1,2 ... N, knIt is greater than 0 real number；EIFor the instantaneous energy that inverter side measures, ERFor rectification
The instantaneous energy that side measures；
Step 7: one group of data { (k of N number of data point is formed1, d1), (k2, d2) ..., (kN, dN)}；Wherein, d1, d2... ...,
dNFor the distance of the DC line of N number of Along ent positional distance rectification side；
Step 8: it is carried out curve fitting using least square fitting to the data that step 7 obtains, obtains fault localization function:
D=f (k)；
Wherein, d is fault distance, and f (k) is the energy ratio k of inverter side and rectification side and the function of fault distance；
Judge whether to break down according to the situation of change of arrangement entropy, however, it is determined that break down, then carry out ranging；If not therefore
Barrier, is the microvariations of a normal operation, then without ranging, comprising the following steps:
Step 1: voltage traveling wave signal being measured in the rectifier terminal of transmission line of electricity and inversion end based on Wide Area Measurement System, if arrangement entropy
When the index of poor ratio is greater than+15%, then it is determined as system and failure has occurred, utilize fault localization function measurement abort situation；
Step 2: decomposing the voltage traveling wave signal of abort situation rectification side and inverter side using wavelet packet decomposition algorithm, extract 5 layers
The low frequency component of the voltage traveling wave signal of rectification side and inverter side after WAVELET PACKET DECOMPOSITION, and calculate the instantaneous energy E of inverter sideIWith
The instantaneous energy E of rectification sideR；
Step 3: calculating inverter side instantaneous energy EIWith rectification side instantaneous energy ERRatio obtain energy ratio k, by energy ratio k
It brings fault localization function: d=f (k) into, obtains fault localization distance d, fault point.
2. the HVDC circuit fault distance measurement according to claim 1 based on concentric relaxation principle, which is characterized in that institute
State the fast method of wavelet packet decomposition algorithm are as follows:
Wherein, k is time location parameter, and f (t) is a time signal,Indicate i-th of wavelet packet coefficient on jth layer, H, G
Indicate wavelet decomposition filter, H is related with scaling function, and G is related with wavelet function；
The restructing algorithm of wavelet packet decomposition algorithm are as follows:
Wherein, j=0,1 ..., n indicate Decomposition order；I=1,2 ..., 2j-1,2j；H, g indicates wavelet reconstruction filter.
3. the HVDC circuit fault distance measurement according to claim 1 based on concentric relaxation principle, which is characterized in that institute
State the index of arrangement entropy difference ratio are as follows:
In formula, pec is the arrangement entropy of magnitude of current time series, and T is current cycle, IdFor the current signal measured when failure,
(t1,t1+ nT) it is electric current from t1Moment is to t1The magnitude of current time sequential value at+nT moment.
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