CN112147460A - Hybrid direct current transmission line protection method, system and storage medium thereof - Google Patents
Hybrid direct current transmission line protection method, system and storage medium thereof Download PDFInfo
- Publication number
- CN112147460A CN112147460A CN202010925511.XA CN202010925511A CN112147460A CN 112147460 A CN112147460 A CN 112147460A CN 202010925511 A CN202010925511 A CN 202010925511A CN 112147460 A CN112147460 A CN 112147460A
- Authority
- CN
- China
- Prior art keywords
- line
- mode voltage
- fault
- calculating
- current transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005540 biological transmission Effects 0.000 title claims abstract description 83
- 238000000034 method Methods 0.000 title claims abstract description 34
- 238000003860 storage Methods 0.000 title claims abstract description 18
- 230000006835 compression Effects 0.000 claims abstract description 71
- 238000007906 compression Methods 0.000 claims abstract description 71
- 230000001360 synchronised effect Effects 0.000 claims abstract description 55
- 238000004364 calculation method Methods 0.000 claims description 16
- 238000004590 computer program Methods 0.000 claims description 10
- 238000005516 engineering process Methods 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 3
- 230000035945 sensitivity Effects 0.000 abstract description 4
- 230000009466 transformation Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 11
- 238000012545 processing Methods 0.000 description 6
- 230000001052 transient effect Effects 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 230000006870 function Effects 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 238000009499 grossing Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000021615 conjugation Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000035772 mutation Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000011426 transformation method Methods 0.000 description 1
- 238000013519 translation Methods 0.000 description 1
Images
Classifications
-
- 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
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0084—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring voltage only
Abstract
The invention discloses a method and a system for protecting a hybrid direct-current transmission line and a storage medium thereof, aiming at solving the technical problems of insufficient accuracy and sensitivity of line protection in the prior art. It includes: calculating fault components of line mode voltages at two ends of the line according to voltages at two ends of the direct current transmission line after protection is started; calculating the high-frequency and low-frequency energy ratio of line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient; and judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio. The invention can improve the reliability and sensitivity of the series-parallel direct current transmission system line protection.
Description
Technical Field
The invention relates to a method and a system for protecting a hybrid direct-current transmission line and a storage medium thereof, belonging to the technical field of power transmission and distribution.
Background
In order to integrate the advantages of a Line comutered Converter based High Voltage Direct Current (LCC-HVDC) transmission system and a Voltage Source Converter based flexible Direct Current (VSC-HVDC) transmission system based on a thyristor technology, a hybrid Direct Current transmission system becomes an important development direction of a transmission system. One implementation of a hybrid dc power transmission system is: the method comprises the following steps that an LCC is adopted at a sending end, and a receiving end is in series-parallel connection with a plurality of Voltage Source Converters (VSCs) to carry out direct-current transmission; the hybrid direct-current power transmission system provides a more flexible and faster power transmission mode, improves the voltage stability of an alternating-current system on the inversion side, reduces the probability of phase commutation failure, and can give consideration to economic and technical benefits. The relay protection level of the hybrid direct-current transmission system, particularly the line, has great influence on the stability and the safety of the operation of the power system, so that the research on the rapid protection technology of the hybrid direct-current transmission system has important theoretical significance and practical application value.
The conventional direct-current transmission line protection is generally divided into main protection and backup protection, wherein the main protection is provided with traveling wave protection and differential undervoltage protection, and the backup protection is longitudinal current differential protection. One important condition for implementation of the traveling wave protection scheme is extraction and analysis of fault transient information. The fault transient signal is a nonlinear and non-stationary transient signal with mutation property, and tools such as wavelet transformation, S transformation, Hilbert-Huang transformation and the like with time-frequency analysis are suitable for analyzing and processing the fault transient signal, wherein the wavelet transformation has the advantages of numerous mathematical analysis methods, and the fault transient signal has better time-frequency resolution capability and is widely applied.
However, the existing traveling wave protection of the direct current transmission line still has the following disadvantages: 1) as single-side electric quantity protection, the protection range of the existing traveling wave protection cannot protect the whole length of a line, and the protection is difficult to detect high-resistance ground faults on the line; 2) the existing travelling wave signal extraction mainly adopts a wavelet transformation method, but the transient wave surges of each fault determined by the fault position and the length of a power transmission line are not mutually independent and even have aliasing, which can influence the precision of extracting frequency components; 3) the primary structure of the hybrid direct-current transmission system is greatly different from that of the conventional direct-current transmission system, and the conventional direct-current line protection method is difficult to be applied to the hybrid direct-current transmission line.
Disclosure of Invention
The invention provides a method, a system and a storage medium for protecting a hybrid direct-current transmission line, which aim to solve the problems of the hybrid direct-current transmission line protection in the prior art, extract high-frequency energy and low-frequency energy in voltage fault components by using synchronous compression wavelet transformation, respectively calculate the ratio of the high-frequency energy to the low-frequency energy in the voltage fault components at two ends of the line, compare the ratio of the high-frequency energy to the low-frequency energy with a threshold value, identify whether the direct-current transmission line has faults or not and identify fault areas, and perform corresponding protection actions.
In order to solve the technical problems, the invention adopts the following technical means:
in a first aspect, the invention provides a hybrid direct current transmission line protection method based on synchronous compression wavelet transform, which is characterized by comprising the following steps:
step A, calculating fault components of line mode voltages at two ends of a line according to voltages at two ends of a direct current transmission line;
b, calculating a synchronous compression wavelet coefficient according to the fault component of the line mode voltage;
step C, calculating the high-frequency and low-frequency energy ratio of line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient;
and D, judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio.
With reference to the first aspect, further, the step a specifically includes the following steps:
a01, acquiring positive and negative voltage signals at two ends of the direct current transmission line in real time, and calculating fault components of the positive and negative voltages at the two ends of the line after protection is started;
step A02, decoupling the two-pole lines coupled with each other into a mutually independent single-phase system by adopting a phase-mode conversion technology, and calculating the fault component of the line-mode voltage, wherein the specific calculation formula is as follows:
wherein, Δ ul1(t) represents the line mode voltage fault component, Deltau, at the head end of the DC transmission line at time tl2(t) represents the line mode voltage fault component at the end of the DC transmission line at time t, Delauup1(t) represents the fault component of the positive voltage at the head end of the line at time t, Deltauq1(t) represents the fault component of the line head end negative voltage at time t, Delauup2(t) represents the fault component of the line terminal positive voltage at time t, Δ uq2(t) represents the fault component of the line end cathode voltage at time t.
With reference to the first aspect, further, the calculation formula of the wavelet coefficients of the synchronous compression in step B is as follows:
wherein, Ts(omega, b) represents synchronous compression wavelet coefficient corresponding to fault component of line mode voltage, delta omega is frequency interval, akRepresenting the k-th scale factor, ωx(a, b) represents the instantaneous frequency corresponding to the fault component of the line mode voltage, [ omega ] represents the center frequency of the line mode voltage, Wx(a, b) wavelet coefficients corresponding to fault components of line mode voltage (Δ a)kRepresents the difference between the kth scale factor and the kth-1 scale factor, (Δ a)k＝ak-ak-1And k is a positive integer.
With reference to the first aspect, further, step B specifically includes the following steps:
step B01, respectively selecting n center frequencies of the high frequency band of the line head end line mode voltage
And n center frequencies of a low frequency band
Wherein j is 1 … n;
step B02, calculating the line mode voltage fault component delta u of the head end of the linel1(t) simultaneous compression wavelet coefficients for high band center frequency:
calculating line mode voltage fault component delta u of line head endl1(t) simultaneous compression wavelet coefficients for the low band center frequency:
step B03, respectively selecting n center frequencies of the high frequency band of the line mode voltage at the tail end of the line
And n center frequencies of a low frequency band
Step B04, calculating line mode voltage fault component delta u at the end of the linel2(t) simultaneous compression wavelet coefficients for high band center frequency:
calculating line mode voltage fault component delta u at tail end of linel2(t) simultaneous compression wavelet coefficients for the low band center frequency:
with reference to the first aspect, further, step C specifically includes the following steps:
step C01, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the head end of the line, wherein the specific formula is as follows:
wherein E is1hRepresenting the high frequency energy of the line mode voltage at the head of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E1lLow frequency energy representing line mode voltage at the head of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C02, calculating the ratio R of the high frequency energy and the low frequency energy of the line mode voltage at the head end of the line1：
R1＝E1h/E1l (6)
Step C03, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the end of the line, wherein the specific formula is as follows:
wherein E is2hThe high frequency energy representing the line mode voltage at the end of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E2lLow frequency energy representing line mode voltage at the end of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C04, calculating the ratio R of the high frequency energy and the low frequency energy of the line mode voltage at the end of the line2：
R2＝E2h/E2l (9)
With reference to the first aspect, further, the specific operations of step D are as follows:
setting two threshold values RsetHAnd RsetLWherein R issetH＞RsetL；
Respectively reacting R with1And R2And a threshold value RsetHAnd RsetLComparing, and judging the fault occurrence area of the direct current transmission line according to the criteria as follows:
the first criterion is as follows: if R is1＞RsetHOr R2＞RsetHIf the fault occurs in the line area, the line protection acts;
the second criterion: if R issetH≥R1＞RsetLAnd R issetH≥R2＞RsetLIf the fault occurs in the line area, the line protection acts;
the third criterion is as follows: if R is1And R2And if the first criterion and the second criterion are not met, judging that the fault occurs outside the line area, and the line protection does not act.
In a second aspect, the present invention provides a hybrid dc power transmission line protection device based on synchronous compression wavelet transform, the device comprising:
the fault component calculation module is used for calculating the fault components of the line mode voltages at the two ends of the line according to the voltages at the two ends of the direct current transmission line;
the synchronous compression wavelet transform module is used for calculating a synchronous compression wavelet coefficient according to the fault component of the line mode voltage;
the energy ratio calculation module is used for calculating the high-frequency and low-frequency energy ratio of the line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient;
and the fault area judging module is used for judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio.
In a third aspect, the invention provides a hybrid direct current transmission line protection device based on synchronous compression wavelet transform, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of the first aspect.
In a fourth aspect, the invention proposes a computer-readable storage medium having stored thereon a computer program which, when being executed by a processor, carries out the steps of the method according to the first aspect.
The following advantages can be obtained by adopting the technical means:
the invention provides a method and a system for protecting a hybrid direct-current transmission line and a storage medium thereof, the method and the system use the measurement information of two ends of the line in the hybrid direct-current transmission system, and compared with the single-side electric quantity protection, the method and the system can improve the reliability of the line protection of the hybrid direct-current transmission system, and simultaneously, the method and the system adopt synchronous compression wavelet transformation to more accurately extract high-frequency energy and low-frequency energy of signals, thereby improving the protection sensitivity. When judging whether a fault occurs or not and a fault occurrence area, the criterion provided by the invention fully utilizes the single-end quantity and the double-end quantity, can effectively solve the problems of the existing direct-current line protection and ensures the accuracy of judgment.
Drawings
Fig. 1 is a schematic structural diagram of a hybrid dc power transmission system according to an embodiment of the present invention.
Fig. 2 is a flowchart of steps of a hybrid dc transmission line protection method based on synchronous compression wavelet transform according to the present invention.
Fig. 3 is a flowchart of a hybrid dc transmission line protection method based on synchronous compression wavelet transform according to the present invention.
Fig. 4 is a schematic structural diagram of a hybrid dc transmission line protection device based on synchronous compression wavelet transform according to the present invention.
In the figure, 1 is a smoothing reactor, 2 is a direct current filter, 3 is a direct current transmission line, 4 is a direct current protection system, 501 is a fault component calculation module, 502 is a synchronous compression wavelet transformation module, 503 is an energy ratio calculation module, and 504 is a fault region discrimination module.
Detailed Description
The technical scheme of the invention is further explained by combining the accompanying drawings as follows:
fig. 1 is a schematic structural diagram of a hybrid dc transmission system according to an embodiment of the present invention, a transmission end of the transmission system employs a grid commutation converter type (LCC type) conventional dc converter station, a reception end high end employs a grid commutation converter type (LCC type) conventional dc converter station, a reception end low end employs a plurality of voltage source converter (VSC type) flexible dc converter stations, and the plurality of flexible dc converter stations (VSC type) are connected in parallel and then connected in series with the conventional dc converter station. In the figure, 1 is a smoothing reactor, 2 is a direct current filter, 3 is a direct current transmission line, and 4 is a direct current protection system.
For the power transmission system in fig. 1, the invention provides a hybrid direct current power transmission line protection method based on synchronous compression wavelet transform, as shown in fig. 2 and 3, specifically comprising the following steps:
step A, calculating the fault components of the line mode voltages at the two ends of the line according to the voltages at the two ends of the direct current transmission line, and specifically operating as follows:
step A01, acquiring positive and negative voltage signals at two ends of the direct current transmission line in real time, and calculating fault components of the positive and negative voltages at the two ends of the line after the protection is started, namely calculating the difference value between the positive and negative voltages at the two ends of the line at the current moment t and the positive and negative voltages at the two ends of the line at the steady state moment.
Step A02, decoupling the two-pole lines coupled with each other into a mutually independent single-phase system by adopting a phase-mode conversion technology, and calculating the fault component of the line-mode voltage, wherein the specific calculation formula is as follows:
wherein, Δ ul1(t) represents the line mode voltage fault component, Deltau, at the head end of the DC transmission line at time tl2(t) represents the line mode voltage fault component at the end of the DC transmission line at time t, Delauup1(t) represents the fault component of the positive voltage at the head end of the line at time t, Deltauq1(t) represents the fault component of the line head end negative voltage at time t, Delauup2(t) represents the fault component of the line terminal positive voltage at time t, Δ uq2(t) represents the fault component of the line end cathode voltage at time t.
And B, calculating the synchronous compression wavelet coefficient according to the fault component of the line mode voltage.
The derivation process of the synchronous compression wavelet coefficient is as follows:
1) and performing continuous wavelet transformation on the fault component of the line mode voltage by using a given mother wavelet function phi to obtain a wavelet coefficient:
wherein, Wx(a, b) wavelet coefficients corresponding to fault components of line mode voltage, a being scale factor, b being translation factor, x (t) being fault components of line mode voltage, i.e. x (t) { Δ u ═ t)l1(t),Δul2(t), t being the time,
representing solving wavelet functions
And (6) conjugation.
2) And calculating the instantaneous frequency according to the wavelet coefficient:
wherein, ω isx(a, b) represents the instantaneous frequency corresponding to the fault component of the line mode voltage, i is in imaginary units,
is Wx(a, b) first order partial derivatives of b.
3) Determining a frequency interval delta omega, selecting the central frequency omega of the line mode voltage, and compressing the wavelet coefficient in a time-frequency plane into a neighborhood of the central frequency omega, wherein the neighborhood in the invention is
4) Considering that the computer discretizes the scale factor a in the process of calculating the synchronous compression coefficient, let (Δ a)k＝ak-ak-1Wherein (Δ a)kRepresents the difference between the k scale factor and the k-1 scale factor, akDenotes the k scale factor, ak-1Represents the k-1 scale factor, akA classic value-taking method is ak＝2kAnd k is a positive integer.
The calculation formula of the synchronous compression wavelet coefficient is as follows:
wherein, Ts(ω, b) represents the simultaneous compressed wavelet coefficients corresponding to the fault component of the line mode voltage.
The synchronous compression can compress the diffusion region of the wavelet transform coefficient in the frequency/scale direction to a region with omega, can improve the time-frequency aggregation of the analysis result, and is suitable for accurately extracting the energy of different frequency bands of the fault signal.
The step B specifically comprises the following steps:
step B01, respectively selecting n center frequencies of the high frequency band of the line head end line mode voltage
And n center frequencies of a low frequency band
Wherein j is 1 … n,
the jth center frequency of the high band representing the line mode voltage at the head of the line,
and j-th center frequency of a low frequency band of line mode voltage at the head end of the line is represented.
Step B02, calculating the line mode voltage fault component delta u of the head end of the line according to the formulas (12) to (14)l1(t) simultaneous compression wavelet coefficients for high band center frequency:
wherein the content of the first and second substances,
high-frequency-band jth center frequency representing line mode voltage at head end of line
Synchronously compressing wavelet coefficients; calculating the line mode voltage fault component delta u of the head end of the line according to the formulas (12) to (14)l1(t) simultaneous compression wavelet coefficients for the low band center frequency:
wherein the content of the first and second substances,
low-frequency-band jth central frequency representing line mode voltage at head end of line
The wavelet coefficients are compressed synchronously.
Step B03, respectively selecting n center frequencies of the high frequency band of the line mode voltage at the tail end of the line
And n center frequencies of a low frequency band
Wherein the content of the first and second substances,
the jth center frequency of the high band representing the line mode voltage at the end of the line,
the jth center frequency of the low band representing the line mode voltage at the end of the line.
Step B04, calculating line end line mode voltage fault component delta u according to formulas (12) to (14)l2(t) simultaneous compression wavelet coefficients for high band center frequency:
wherein the content of the first and second substances,
high band jth center frequency representing line mode voltage at line end
Synchronously compressing wavelet coefficients; calculating line end line mode voltage fault component delta u according to formulas (12) to (14)l2(t) simultaneous compression wavelet coefficients for the low band center frequency:
wherein the content of the first and second substances,
low band jth center frequency representing line mode voltage at end of line
The wavelet coefficients are compressed synchronously.
Step C, calculating the high-frequency and low-frequency energy ratio of line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient; the specific operation is as follows:
step C01, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the head end of the line, wherein the specific formula is as follows:
wherein E is1hRepresenting the high frequency energy of the line mode voltage at the head of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E1lLow frequency energy representing line mode voltage at the head of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C02, calculating the high frequency energy and the low frequency energy of the line mode voltage at the head end of the lineRatio of R1：
R1＝E1h/E1l (17)
Step C03, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the end of the line, wherein the specific formula is as follows:
wherein E is2hThe high frequency energy representing the line mode voltage at the end of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E2lLow frequency energy representing line mode voltage at the end of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C04, calculating the ratio R of the high frequency energy and the low frequency energy of the line mode voltage at the end of the line2：
R2＝E2h/E2l (20)
D, judging a fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio; the specific operation is as follows:
considering that when a fault occurs in a zone, the fault can be at any position on a direct current line, and the line can generate certain attenuation effect on high frequency quantity, the fault is arrangedTwo threshold values RsetHAnd RsetLWherein R issetH＞RsetL。
Respectively reacting R with1And R2And a threshold value RsetHAnd RsetLAnd comparing, and judging the fault occurrence area of the direct current transmission line according to the criterion.
Taking the hybrid direct-current transmission system in the embodiment of the invention as an example, when a fault occurs outside a direct-current line area, a filter and a smoothing reactor at the head end and the tail end of the direct-current line can generate an obvious attenuation effect on a high-frequency component in a voltage fault component, and the ratio of the high-frequency energy to the low-frequency energy at the head end and the tail end of the line is generally very small; when a fault occurs in a direct current line area, high-frequency components in fault components are not subjected to a filter and a smoothing reactor, attenuation is small, and the ratio of high-frequency energy to low-frequency energy at the head end and the tail end of the corresponding line is generally large.
The criteria in the present invention according to the above analysis are specifically as follows:
the first criterion is as follows: if R is1＞RsetHOr R2＞RsetHIf the fault occurs in the line area, the line protection acts;
the second criterion: if R issetH≥R1＞RsetLAnd R issetH≥R2＞RsetLIf the fault occurs in the line area, the line protection acts;
the third criterion is as follows: if R is1And R2And if the first criterion and the second criterion are not met, judging that the fault occurs outside the line area, and the line protection does not act.
The invention also provides a hybrid direct-current transmission line protection device based on synchronous compression wavelet transformation, which comprises a fault component calculation module 501, a synchronous compression wavelet transformation module 502, an energy ratio calculation module 503 and a fault region judgment module 504, wherein the fault component calculation module is used for calculating the fault component of line mode voltage at two ends of a line according to the voltage at two ends of the direct-current transmission line after protection is started, as shown in fig. 4; the synchronous compression wavelet transformation module is used for calculating a synchronous compression wavelet coefficient according to the fault component of the line mode voltage, and specifically comprises the following operations: processing fault components of line mode voltage by utilizing continuous wavelet transformation, calculating wavelet coefficients and instantaneous frequency, and compressing the wavelet coefficients in a time-frequency plane to a field of central frequency to obtain synchronous compressed wavelet coefficients; the energy ratio calculation module is used for calculating the high-frequency and low-frequency energy ratio of the line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient; and the fault area judging module is used for judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio.
The invention also provides a hybrid direct-current transmission line protection device based on synchronous compression wavelet transform, which comprises a processor and a storage medium; a storage medium to store instructions; the processor is used for operating according to the instruction to execute the steps of the hybrid direct current transmission line protection method based on the synchronous compression wavelet transform.
The invention also proposes a computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of a hybrid direct current transmission line protection method based on a synchronous compressive wavelet transform according to the invention.
Compared with the prior art, the invention has the following advantages: 1. the method and the device use the measurement information of two ends of the line in the hybrid direct-current transmission system, and can improve the reliability of the line protection of the hybrid direct-current transmission system relative to the single-side electric quantity protection; 2. the high-frequency energy and the low-frequency energy of the signals are more accurately extracted by adopting synchronous compression wavelet transform, so that the protection sensitivity is improved; 3. when judging whether a fault occurs or not and a fault occurrence area, the criterion provided by the invention fully utilizes the single-end quantity and the double-end quantity, can effectively solve the problems of the existing direct-current line protection and ensures the accuracy of judgment.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A hybrid direct current transmission line protection method based on synchronous compression wavelet transform is characterized by comprising the following steps:
step A, calculating fault components of line mode voltages at two ends of a line according to voltages at two ends of a direct current transmission line;
b, calculating a synchronous compression wavelet coefficient according to the fault component of the line mode voltage;
step C, calculating the high-frequency and low-frequency energy ratio of line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient;
and D, judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio.
2. The hybrid direct-current transmission line protection method based on the synchronous compression wavelet transform according to claim 1, wherein the step A specifically comprises the following steps:
a01, acquiring positive and negative voltage signals at two ends of the direct current transmission line in real time, and calculating fault components of the positive and negative voltages at the two ends of the line after protection is started;
step A02, decoupling the two-pole lines coupled with each other into a mutually independent single-phase system by adopting a phase-mode conversion technology, and calculating the fault component of the line-mode voltage, wherein the specific calculation formula is as follows:
wherein, Δ ul1(t) represents the line mode voltage fault component, Deltau, at the head end of the DC transmission line at time tl2(t) represents the line mode voltage fault component at the end of the DC transmission line at time t, Delauup1(t) represents the fault component of the positive voltage at the head end of the line at time t, Deltauq1(t) represents the fault component of the line head end negative voltage at time t, Delauup2(t) represents the fault component of the line terminal positive voltage at time t, Δ uq2(t) represents the fault component of the line end cathode voltage at time t.
3. The hybrid direct-current transmission line protection method based on synchronous compression wavelet transform according to claim 2, wherein the calculation formula of the synchronous compression wavelet coefficient in step B is as follows:
wherein, Ts(omega, b) represents synchronous compression wavelet coefficient corresponding to fault component of line mode voltage, delta omega is frequency interval, akRepresenting the k-th scale factor, ωx(a, b) represents the instantaneous frequency corresponding to the fault component of the line mode voltage, [ omega ] represents the center frequency of the line mode voltage, Wx(a, b) wavelet coefficients corresponding to fault components of line mode voltage (Δ a)kRepresents the difference between the kth scale factor and the kth-1 scale factor, (Δ a)k＝ak-ak-1And k is a positive integer.
4. The hybrid direct-current transmission line protection method based on the synchronous compression wavelet transform according to claim 3, wherein the step B specifically comprises the following steps:
step B01, respectively selecting n center frequencies of the high frequency band of the line head end line mode voltage
And n center frequencies of a low frequency band
Wherein j is 1 … n;
step B02, calculating the line mode voltage fault component delta u of the head end of the linel1(t) for high band center frequenciesSimultaneous compression of wavelet coefficients of rate:
calculating line mode voltage fault component delta u of line head endl1(t) simultaneous compression wavelet coefficients for the low band center frequency:
step B03, respectively selecting n center frequencies of the high frequency band of the line mode voltage at the tail end of the line
And n center frequencies of a low frequency band
Step B04, calculating line mode voltage fault component delta u at the end of the linel2(t) simultaneous compression wavelet coefficients for high band center frequency:
calculating line mode voltage fault component delta u at tail end of linel2(t) simultaneous compression wavelet coefficients for the low band center frequency:
5. the hybrid direct-current transmission line protection method based on synchronous compression wavelet transform according to claim 4, wherein the step C specifically comprises the following steps:
step C01, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the head end of the line, wherein the specific formula is as follows:
wherein E is1hRepresenting the high frequency energy of the line mode voltage at the head of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E1lLow frequency energy representing line mode voltage at the head of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C02, calculating the ratio R of the high frequency energy and the low frequency energy of the line mode voltage at the head end of the line1：
R1＝E1h/E1l
Step C03, calculating the high frequency energy and the low frequency energy according to the synchronous compression wavelet coefficient of the line mode voltage at the end of the line, wherein the specific formula is as follows:
wherein E is2hThe high frequency energy representing the line mode voltage at the end of the line,
indicating the jth center frequency of the high band
Synchronous compression of wavelet coefficients, E2lLow frequency energy representing line mode voltage at the end of the line,
indicating the jth center frequency of the low band
Synchronously compressing wavelet coefficients;
step C04, calculating the ratio R of the high frequency energy and the low frequency energy of the line mode voltage at the end of the line2：
R2＝E2h/E2l
6. The hybrid direct-current transmission line protection method based on the synchronous compression wavelet transform according to claim 5, wherein the specific operations of step D are as follows:
setting two threshold values RsetHAnd RsetLWherein R issetH＞RsetL；
Respectively reacting R with1And R2And a threshold value RsetHAnd RsetLComparing, and judging the fault occurrence area of the direct current transmission line according to the criteria as follows:
the first criterion is as follows: if R is1＞RsetHOr R2＞RsetHIf the fault occurs in the line area, the line protection acts;
the second criterion: if R issetH≥R1＞RsetLAnd R issetH≥R2＞RsetLIf the fault occurs in the line area, the line protection acts;
the third criterion is as follows: if R is1And R2If neither the first criterion nor the second criterion is satisfied, the determination is madeAnd when the break fault occurs outside the line area, the line protection does not act.
7. A hybrid direct current transmission line protection device based on synchronous compression wavelet transform is characterized by comprising:
the fault component calculation module is used for calculating the fault components of the line mode voltages at the two ends of the line according to the voltages at the two ends of the direct current transmission line;
the synchronous compression wavelet transform module is used for calculating a synchronous compression wavelet coefficient according to the fault component of the line mode voltage;
the energy ratio calculation module is used for calculating the high-frequency and low-frequency energy ratio of the line mode voltages at two ends of the line according to the synchronous compression wavelet coefficient;
and the fault area judging module is used for judging the fault occurrence area of the direct current transmission line according to the high-frequency energy ratio and the low-frequency energy ratio.
8. A hybrid direct current transmission line protection device based on synchronous compression wavelet transform is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 6.
9. Computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010925511.XA CN112147460B (en) | 2020-09-04 | Hybrid direct current transmission line protection method, system and storage medium thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010925511.XA CN112147460B (en) | 2020-09-04 | Hybrid direct current transmission line protection method, system and storage medium thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN112147460A true CN112147460A (en) | 2020-12-29 |
| CN112147460B CN112147460B (en) | 2024-04-26 |
Family
ID=
Citations (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964515A (en) * | 2010-08-27 | 2011-02-02 | 昆明理工大学 | Method for converting boundary element by extra-high voltage direct current transmission line mode voltage S |
| CN102005740A (en) * | 2010-10-29 | 2011-04-06 | 昆明理工大学 | Extra-high voltage direct current line boundary element method adopting polar wave wavelet energy ratio |
| CN102005739A (en) * | 2010-08-27 | 2011-04-06 | 昆明理工大学 | Method for identifying extra-high voltage direct current transmission line area inside and outside fault wavelet energy |
| CN102156246A (en) * | 2011-03-24 | 2011-08-17 | 昆明理工大学 | Wavelet energy entropy detecting method for recognizing faults of ultra-high voltage direct-current transmission line |
| KR101317561B1 (en) * | 2012-05-16 | 2013-10-11 | 용인송담대학교 산학협력단 | Method for detecting ground fault of power line using wavelet transform |
| CN103529332A (en) * | 2013-10-28 | 2014-01-22 | 昆明理工大学 | Ultra-high voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics |
| WO2014089899A1 (en) * | 2012-12-10 | 2014-06-19 | 国家电网公司 | Distribution network phase-to-earth fault location method and location device based on transient signal wavelet transformation |
| CN104377667A (en) * | 2014-11-06 | 2015-02-25 | 上海交通大学 | High-voltage direct-current line pilot protection method based on boundary energy |
| CN105790239A (en) * | 2016-05-19 | 2016-07-20 | 山东大学 | High-voltage direct-current power transmission line non-unit protection method based on S transformation |
| CN106019076A (en) * | 2016-05-16 | 2016-10-12 | 西安理工大学 | Fault distance detecting method for high-voltage DC transmission line |
| WO2017024618A1 (en) * | 2015-08-13 | 2017-02-16 | 国家电网公司 | Hybrid line fault point positioning method based on single-end electrical quantity and comprehensive transient travelling wave characteristic analysis |
| CN108896869A (en) * | 2018-06-22 | 2018-11-27 | 国网天津市电力公司 | A kind of HVDC transmission line lightning stroke interference identification method based on S-transformation |
| CN109119977A (en) * | 2018-09-20 | 2019-01-01 | 山东大学 | Multiterminal flexible direct current power grid DC line fast protection method and system based on single ended voltage |
| CN111313386A (en) * | 2020-03-26 | 2020-06-19 | 华南理工大学 | Multi-terminal hybrid high-voltage direct-current line transient protection method and system |
| CN111463764A (en) * | 2020-05-14 | 2020-07-28 | 山东大学 | Direct-current transmission line protection method based on initial voltage traveling wave frequency domain attenuation rate |
Patent Citations (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964515A (en) * | 2010-08-27 | 2011-02-02 | 昆明理工大学 | Method for converting boundary element by extra-high voltage direct current transmission line mode voltage S |
| CN102005739A (en) * | 2010-08-27 | 2011-04-06 | 昆明理工大学 | Method for identifying extra-high voltage direct current transmission line area inside and outside fault wavelet energy |
| CN102005740A (en) * | 2010-10-29 | 2011-04-06 | 昆明理工大学 | Extra-high voltage direct current line boundary element method adopting polar wave wavelet energy ratio |
| CN102156246A (en) * | 2011-03-24 | 2011-08-17 | 昆明理工大学 | Wavelet energy entropy detecting method for recognizing faults of ultra-high voltage direct-current transmission line |
| KR101317561B1 (en) * | 2012-05-16 | 2013-10-11 | 용인송담대학교 산학협력단 | Method for detecting ground fault of power line using wavelet transform |
| WO2014089899A1 (en) * | 2012-12-10 | 2014-06-19 | 国家电网公司 | Distribution network phase-to-earth fault location method and location device based on transient signal wavelet transformation |
| CN103529332A (en) * | 2013-10-28 | 2014-01-22 | 昆明理工大学 | Ultra-high voltage direct current transmission line lightning stroke interference recognition method based on voltage relevancy and wavelet transformation transient state energy distribution characteristics |
| CN104377667A (en) * | 2014-11-06 | 2015-02-25 | 上海交通大学 | High-voltage direct-current line pilot protection method based on boundary energy |
| WO2017024618A1 (en) * | 2015-08-13 | 2017-02-16 | 国家电网公司 | Hybrid line fault point positioning method based on single-end electrical quantity and comprehensive transient travelling wave characteristic analysis |
| CN106019076A (en) * | 2016-05-16 | 2016-10-12 | 西安理工大学 | Fault distance detecting method for high-voltage DC transmission line |
| CN105790239A (en) * | 2016-05-19 | 2016-07-20 | 山东大学 | High-voltage direct-current power transmission line non-unit protection method based on S transformation |
| CN108896869A (en) * | 2018-06-22 | 2018-11-27 | 国网天津市电力公司 | A kind of HVDC transmission line lightning stroke interference identification method based on S-transformation |
| CN109119977A (en) * | 2018-09-20 | 2019-01-01 | 山东大学 | Multiterminal flexible direct current power grid DC line fast protection method and system based on single ended voltage |
| CN111313386A (en) * | 2020-03-26 | 2020-06-19 | 华南理工大学 | Multi-terminal hybrid high-voltage direct-current line transient protection method and system |
| CN111463764A (en) * | 2020-05-14 | 2020-07-28 | 山东大学 | Direct-current transmission line protection method based on initial voltage traveling wave frequency domain attenuation rate |
Non-Patent Citations (2)
| Title |
|---|
| 张安安: ""基于行波瞬时振幅的高压直流输电线路故障测距方法研究"", 《智慧电力》, 20 February 2020 (2020-02-20) * |
| 陈争光: "" 基于双树复小波变换的混合直流输电线路行波保护方法"", 《电网技术》, 11 July 2019 (2019-07-11) * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108107321B (en) | Fault waveform comparison method for power system | |
| WO2019080238A1 (en) | Time-domain calculation method for voltage traveling wave differential protection of flexible direct-current transmission line | |
| CN111948493A (en) | MMC-HVDC direct current transmission line fault positioning method | |
| CN112615359B (en) | AC-DC hybrid power grid pilot protection method and system based on voltage waveform comparison | |
| CN108599114A (en) | A kind of high voltage ac/dc combined hybrid system alternating current circuit transient state direction protection method | |
| CN106526422B (en) | Processing method of fault traveling wave of flexible direct current transmission line | |
| CN105375528A (en) | Assessment method of single-phase non-isolation photovoltaic grid connected system for parasitic capacitance to ground | |
| CN110850230B (en) | Method for extracting interpolar short circuit fault characteristic quantity of direct current distribution network based on multi-wavelet theory | |
| CN112582978B (en) | Leakage protection method and device and charging pile | |
| CN112505488B (en) | Double-end fault wave recording and distance measuring method for power transmission line | |
| CN110907753B (en) | HHT energy entropy based MMC-HVDC system single-ended fault identification method | |
| CN112147460B (en) | Hybrid direct current transmission line protection method, system and storage medium thereof | |
| CN113376477A (en) | Flexible direct-current power grid single-end protection method based on traveling wave energy spectrum matrix similarity | |
| CN112147460A (en) | Hybrid direct current transmission line protection method, system and storage medium thereof | |
| Ankar et al. | Wavelet-ANN based fault location scheme for bipolar CSC-based HVDC transmission system | |
| CN111766470B (en) | Fault positioning method and system for high-voltage direct-current transmission line and direct-current transmission line | |
| CN112083280A (en) | Method for identifying fault interval of hybrid multi-terminal direct-current power transmission system | |
| CN109672152B (en) | Pilot protection method for high-voltage direct-current transmission line based on current-conductivity correlation | |
| CN114204525B (en) | Pilot protection method for direct-current transmission line and application thereof | |
| CN115833124A (en) | Converter station direct current near-zone resonance risk assessment method, device, equipment and medium | |
| CN109995005B (en) | Direct-current transmission line pilot protection method based on trigger angle change rate mean value | |
| CN113341273A (en) | Broadband measurement method, device and system for extra-high voltage direct current fault detection | |
| CN111521909B (en) | Complex-structure power grid fault single-terminal location method based on line zero-mode wave velocity difference | |
| CN114578184A (en) | Direct-current transmission line double-end traveling wave frequency difference ratio fault location method and system | |
| CN113655339A (en) | Fault positioning method and device for direct-current transmission line protection system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |