CN109142974A - A kind of alternating current circuit one-end fault ranging method suitable for flexible direct current feed-in - Google Patents
A kind of alternating current circuit one-end fault ranging method suitable for flexible direct current feed-in Download PDFInfo
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- CN109142974A CN109142974A CN201811013492.2A CN201811013492A CN109142974A CN 109142974 A CN109142974 A CN 109142974A CN 201811013492 A CN201811013492 A CN 201811013492A CN 109142974 A CN109142974 A CN 109142974A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/02—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring length, width, or thickness
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Abstract
The invention belongs to field of relay protection in power; more particularly to a kind of alternating current circuit one-end fault ranging method suitable for flexible direct current feed-in; after including the following steps: that transmission system detects generation singlephase earth fault, the single-end electrical quantity of conventional AC power side is acquired.Discrete Fourier transform is carried out to electrical quantity in sampled data window and extracts fundamental component, phase-model transformation is carried out to fundamental component using symmetrical component method under frequency domain, obtains the order components of false voltage, electric current.Based on distributed parameter model, the false voltage along failure phase and negative sequence fault current distribution are calculated.The data group that false voltage, the negative sequence fault current of each distance along one group of failure phase under different moments are constituted is obtained under time domain, according to data group only the characteristics of fault point meets direct proportion linear relationship, one-variable linear regression is utilized to carry out fault localization.Present invention efficiently solves the problem that conventional failure distance measuring method is not suitable for, range accuracies and wide applicability with higher.
Description
Technical field
The invention belongs to field of relay protection in power, and in particular in hybrid AC/DC power transmission systems, flexible direct current
The fault distance-finding method of the alternating current circuit of feed-in.
Background technique
Monopolar grounding fault easily occurs for transmission line of alternation current, and short circuit current can seriously affect the safety and stability fortune of system
Row.Therefore, quick fault point and failure is removed, there is important meaning for the economy and reliability that improve system operation
Justice.Since there is no commutation failure problem, and flexible control and in terms of outstanding advantage, flexible direct current is defeated
Electricity plays key player in fields such as new-energy grid-connected, regional power grid interconnections.In the alternating current-direct current connection based on flexible DC transmission
Under net mode, in AC system fault characteristic value by converter Control strategy and the nonlinear influence of power electronic element, with
Conventional AC system is compared to a great difference is shown, so that the fault distance-finding method of conventional AC system needs to improve to cope with newly
Challenge.
Currently, the research for AC network measuring distance of transmission line fault under flexible direct current feed-in also rarely has document both at home and abroad
Report, existing fault distance-finding method can be divided into traveling wave method, intelligent algorithm and impedance method three classes.Traveling wave method is in fault localization
Aspect has many advantages, but such methods are high to the sample frequency of equipment, and that there are wavefront identifications is more difficult, anti-
The technical problems such as interference difference, range accuracy susceptible.Intelligent algorithm is suitable for the unknown electric system of processing parameter,
But such method is fixed against training process very much, and dares to trained database and be often difficult to obtain.Impedance method can be segmented
Based on Two-Terminal Electrical Quantities and to be based on two class of single-end electrical quantity, the impedance method based on Two-Terminal Electrical Quantities be limited to data it is synchronous and
Communication technology bring cost with high investment.Impedance method principle based on single-end electrical quantity is simple and is easily achieved, but range accuracy
Influence vulnerable to fault resstance and peer-to-peer system.
In order to ensure the safe operation of inverter, soft straight converter station is influenced by fault traversing control mode.Control system root
According to grid entry point positive sequence voltage fall degree in real time adjust output electric current size and phase so that its output fault current with change
It flows device exchange exit voltage and non-linear relation is presented.Once serious short trouble, and Voltage Drop occur for inverter proximal end
More than the regulating power of fault traversing control strategy, inverter, which can be latched, carrys out isolated DC side feedback stream, so that electrical based on both-end
The fault distance-finding method of amount fails.Meanwhile the hypothesis based on single-end electrical quantity distance measuring method same-phase is also further broken.Cause
This, propose the alternating current circuit one-end fault ranging method right and wrong for being suitable for flexible direct current feed-in often with there is practical meaning in engineering,
It is under flexible DC transmission and the overall situation of DC grid rise, hybrid AC/DC power transmission systems development is essential with the urgent of popularization
It asks.
Summary of the invention
The invention is directed to hybrid AC/DC power transmission systems, provides a kind of single-ended event in the alternating current circuit containing flexible direct current feed-in
Hinder distance measuring method, the boundary condition for relying on fault point exclusive carries out one-variable linear regression using least square method, to realize
Fault localization, more traditional one-end fault ranging method, the present invention consider that flexible direct current converter Control strategy on fault is compound
The influence that sequence net generates, so that only relying on single-end electrical quantity can be realized accurate fault localization.Technical solution of the present invention is such as
Under,
A kind of alternating current circuit one-end fault ranging method suitable for flexible direct current feed-in, including the following steps:
(1) after transmission system detects generation singlephase earth fault, the single-end electrical quantity of conventional AC power side is acquired.It is right
Electrical quantity carries out discrete Fourier transform and extracts fundamental component in sampled data window, using symmetrical component method to fundamental frequency under frequency domain
Component carries out phase-model transformation, obtains the order components of false voltage, electric current.
(2) it is based on distributed parameter model, calculates the false voltage along failure phase and negative sequence fault current distribution.
(3) false voltage, negative sequence fault current of each distance under different moments along one group of failure phase are obtained under time domain
The data group of composition utilizes one-variable linear regression according to data group only the characteristics of fault point meets direct proportion linear relationship
Carry out fault localization.
Preferably, step (3) concrete methods of realizing are as follows:
Flexible direct current inverter is influenced by control strategy, provides boundary condition for fault point:
In formula,For fault point residual voltage, RfFor the ground resistance at failure,For the negative phase-sequence electricity for flowing through fault branch
Stream；
Under time domain, define residual sum function H (x):
In formula, u (x, i) indicate failure phase line on apart from conventional AC power side bus x be under different moments therefore
Hinder voltage；i2(x, i) indicates the negative phase-sequence failure being on failure phase line apart from conventional AC power side bus x under different moments
Electric current；Indicate proportionality coefficient；I indicates one group of sampled data points under different moments；N indicates total sampled data points, u
(x, i) and i2(x, i) only meets formula (1) relationship in fault point, carries out one-variable linear regression using least square method, calculates
The residual sum function H (x) of each position along the line, taking corresponding to H (x) minimum value along linear distance x is exactly fault distance xf, realize event
Hinder ranging.
Compared with prior art, the present invention considers the influence of converter Control strategy on fault compound sequence network, proposes one
Kind is suitable for the novel fault distance measuring method of Ac/dc Power Systems, efficiently solves what conventional failure distance measuring method was not suitable for
Problem.This method range accuracy with higher, not by fault resstance, fault distance, inverter low voltage crossing strategy, adopt
The factors such as sample frequency and line distribution capacitance influence.In addition, this method has wide applicability, it is suitable for all configured with suppression
The AC system of flexible DC transmission and the inverse distributed power access of negative-sequence current control strategy processed.
Detailed description of the invention
Fig. 1 is the hybrid AC/DC power transmission systems of flexible direct current feed-in.
Fig. 2 is fault distance-finding method flow chart.
Specific embodiment
The present invention is described in further detail with example with reference to the accompanying drawing.Fig. 1 show a typical flexibility
Singlephase earth fault occurs for the hybrid AC/DC power transmission systems of direct current feed-in, AC power line road.
The fault distance-finding method of the alternating current circuit singlephase earth fault of positioning flexible direct current feed-in of the invention mainly includes
The three parts such as single-end electrical quantity decoupling, the calculating of the order components of false voltage and fault current distribution along the line, ranging criterion.
1. single-end electrical quantity decouples
There are electromagnetic induction between three phase line, accuracy when voltage and current distribution along calculating will affect,
Therefore conventional AC power side electrical quantity must be converted into mutually independent mold component by decoupling transition matrix.Symmetrical components
Method is a kind of mapping mode most commonly seen in accident analysis, and the positive sequence obtained after decomposition, negative phase-sequence and zero sequence are all a kind of moulds
Amount, symmetrical component transformation matrix TSAs shown in formula (1).
In formula, a indicates rotational component, a=ej120°。
The order components of false voltage and fault current, which are distributed, along 2. calculates
Based on distributed parameter model, the single-end electrical quantity of collected conventional AC power side bus is passed through into symmetrical components
Obtained order components are then substituted into formula (2) by method decoupling, calculate along line voltage, current distribution.
In formula, p=1,2,0 indicate corresponding order components；It indicates on failure phase line apart from conventional AC power side
False voltage order components at bus x；Indicate the failure electricity on failure phase line at conventional AC power side bus x
Flow order components；Indicate the voltage sequence components obtained after the single-end electrical quantity decoupling of conventional AC power side bus；It indicates to pass
The current sequence components obtained after the single-end electrical quantity decoupling of system AC power source side bus；ZcpIndicate the feature resistance under route order components
It is anti-；γpIndicate the propagation constant under route order components.
3. ranging criterion
It is influenced by flexible direct current converter Control strategy, the negative sequence network after system generation singlephase earth fault only includes to pass
System alternating current net side, forms a single-terminal network.The negative sequence component of fault point fault current is only provided by conventional AC side,
Influence of the inverter side fault message to fault point is eliminated from principle.Based on the feature, using the list of conventional AC side
Client information amount realizes accurate fault localization.Fault point boundary condition when singlephase earth fault are as follows:
In formula,Indicate fault point residual voltage；Indicate the positive-sequence component of fault point residual voltage；Indicate fault point
Locate the negative sequence component of residual voltage；Indicate the zero-sequence component of fault point residual voltage；RfIndicate the ground resistance at failure；It indicates
Flow through the negative-sequence current of fault branch.
The fault point boundary condition of formula (3) is transformed into forms of time and space by frequency domain, obtains formula (4):
U (x, i)=3Rfi2(x,i) (4)
In formula, u (x, i) indicate failure phase line on apart from conventional AC power side bus x be under different moments therefore
Hinder voltage；i2(x, i) indicates the negative phase-sequence failure being on failure phase line apart from conventional AC power side bus x under different moments
Electric current；I indicates one group of sampled data points under different moments.
Analysis is it is found that by u (x, i), i2The data group that (x, i) is constituted, only meets direct proportion linear relationship in fault point.
It is as follows to establish direct proportion linear model:
In formula, UiIndicate the data group being made of u (x, i)；I2iIt indicates by i2The data group that (x, i) is constituted.
According to formula (5), define residual sum function H (x):
In formula,Indicate proportionality coefficient；N indicates total sampled data points.
According to least square method, when H (x) being made to reach minimum, proportionality coefficientAre as follows:
In formula,Indicate the data group U that sampling obtainsiAverage value；Indicate the data group I that sampling obtains2i
Average value；i2(x,i)2Indicate i2Square of (x, i) value；It indicatesSquare of value.
Therefore by by Ui、i2(x, i) substitute into (6), (7) carry out one-variable linear regression, can calculate along each position it is residual
Difference and function H (x).Data group and the degree of fitting of formula (5) are higher, and H (x) is smaller.It is negative that converter Control system inhibits it to export
The transient process of sequence electric current, frequency domain descender line false voltage, the rounding error in current sequence components calculating process, in linear regression
Calculating error and practical application in mutual inductor progress of disease error that may be present etc., will affect the precision of distance measuring method.Cause
This, taking corresponding to H (x) minimum value along linear distance x is exactly fault distance xf, position of failure point is determined by ranging criterion (8):
H(xf)=min [H (x)] (8)
In conclusion it is as shown in Figure 2 to obtain fault distance-finding method flow chart.
Claims (2)
1. a kind of alternating current circuit one-end fault ranging method suitable for flexible direct current feed-in, including the following steps:
(1) after transmission system detects generation singlephase earth fault, the single-end electrical quantity of conventional AC power side is acquired.To sampling
Electrical quantity carries out discrete Fourier transform and extracts fundamental component in data window, using symmetrical component method to fundamental component under frequency domain
Phase-model transformation is carried out, the order components of false voltage, electric current are obtained.
(2) it is based on distributed parameter model, calculates the false voltage along failure phase and negative sequence fault current distribution.
(3) false voltage, negative sequence fault current of each distance under different moments along one group of failure phase is obtained under time domain to constitute
Data group carried out according to data group only the characteristics of fault point meets direct proportion linear relationship using one-variable linear regression
Fault localization.
2. distance measuring method according to claim 1, wherein step (3) concrete methods of realizing are as follows:
Flexible direct current inverter is influenced by control strategy, provides boundary condition for fault point:
In formula,For fault point residual voltage, RfFor the ground resistance at failure,For the negative-sequence current for flowing through fault branch；
Under time domain, define residual sum function H (x):
In formula, u (x, i) indicates to be in the electricity of the failure under different moments apart from conventional AC power side bus x on failure phase line
Pressure；i2(x, i) indicates that the negative phase-sequence failure being under different moments on failure phase line apart from conventional AC power side bus x is electric
Stream；Indicate proportionality coefficient；I indicates one group of sampled data points under different moments；N indicates that total sampled data is counted, u (x,
And i i)2(x, i) only meets formula (1) relationship in fault point, carries out one-variable linear regression using least square method, calculates edge
The residual sum function H (x) of line each position, taking corresponding to H (x) minimum value along linear distance x is exactly fault distance xf, realize failure
Ranging.
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| CN112595929A (en) * | 2020-12-09 | 2021-04-02 | 天津大学 | Monopole grounding fault location method suitable for true bipolar flexible direct system |
| CN112595928A (en) * | 2020-12-09 | 2021-04-02 | 天津大学 | Flexible-direct system ground fault distance measurement method suitable for monopolar ground operation |
| CN112986753A (en) * | 2021-02-22 | 2021-06-18 | 天津大学 | Flexible direct-current power grid double-end fault location method grounded through metal return line |
| CN113009275A (en) * | 2021-02-22 | 2021-06-22 | 天津大学 | Double-end fault location method for flexible direct-current access alternating-current hybrid line |
| CN113156259A (en) * | 2021-02-22 | 2021-07-23 | 天津大学 | Flexible direct-current power grid double-end fault location method based on Marti frequency-variable model |
| CN113176474A (en) * | 2021-05-08 | 2021-07-27 | 东南大学 | Double-end direct-current power distribution network fault positioning method based on current self-adaptive control |
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| CN112595928B (en) * | 2020-12-09 | 2022-07-05 | 天津大学 | Flexible-direct system ground fault distance measurement method suitable for monopolar ground operation |
| CN112595929B (en) * | 2020-12-09 | 2022-08-02 | 天津大学 | Monopole grounding fault location method suitable for true bipolar flexible direct system |
| CN112986753A (en) * | 2021-02-22 | 2021-06-18 | 天津大学 | Flexible direct-current power grid double-end fault location method grounded through metal return line |
| CN113009275A (en) * | 2021-02-22 | 2021-06-22 | 天津大学 | Double-end fault location method for flexible direct-current access alternating-current hybrid line |
| CN113156259A (en) * | 2021-02-22 | 2021-07-23 | 天津大学 | Flexible direct-current power grid double-end fault location method based on Marti frequency-variable model |
| CN113156259B (en) * | 2021-02-22 | 2022-08-30 | 天津大学 | Flexible direct-current power grid double-end fault location method based on Marti frequency-variable model |
| CN112986753B (en) * | 2021-02-22 | 2022-10-04 | 天津大学 | Flexible direct-current power grid double-end fault location method grounded through metal return line |
| CN113176474A (en) * | 2021-05-08 | 2021-07-27 | 东南大学 | Double-end direct-current power distribution network fault positioning method based on current self-adaptive control |
| CN113176474B (en) * | 2021-05-08 | 2022-08-02 | 东南大学 | Double-end direct-current power distribution network fault positioning method based on current self-adaptive control |
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