CN113437734B - Fault protection method and device suitable for wind power plant output line - Google Patents
Fault protection method and device suitable for wind power plant output line Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/24—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to undervoltage or no-voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/34—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system
- H02H3/353—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors of a three-phase system involving comparison of phase voltages
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/381—Dispersed generators
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/76—Power conversion electric or electronic aspects
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Abstract
The invention discloses a fault protection method and a device suitable for a transmission line of a wind power plant, wherein the method comprises the steps of collecting three-phase voltage data and three-phase current data of a transmission line protection installation position in real time; judging whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value; if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging the certain phase as a fault phase; and calculating the voltage drop degree and the three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value. And when the fault is not serious, the distance protection criterion based on steady-state power frequency quantity action is selected, and when the fault is serious, the transient protection criterion based on wavelet transformation is switched, so that the fault isolation can be accelerated by switching the criterion under the condition of the serious fault.
Description
Technical Field
The invention belongs to the technical field of line protection of a new energy grid-connected power system, and particularly relates to a fault protection method and device suitable for a wind power plant output line.
Background
With the increasing development and utilization rate of renewable new energy, the situation that wind power is intensively connected into a power system is more and more common, and the number of lines sent out by the wind power system is greatly increased. The wind power plant transmission line has particularity, on one hand, a new energy power supply grid-connected converter cannot bear overlarge current impact, so that the fault needs to be rapidly removed under the condition of the transmission line fault through relay protection, and on the other hand, due to control strategies such as internal fault suppression and the like of a fan, the fault characteristics different from those of a traditional rotating synchronous machine power supply can be generated during the fault, and the correct action of the relay protection is challenged.
The existing wind power transmission line protection method basically only uses steady-state power frequency information after the fault, the adaptability of a wind power transmission line adopting power electronic equipment for grid connection is still doubtful, and besides the reduction of protection sensitivity, the protection reliability under a special scene also has a potential false action rejection risk; meanwhile, the existing protection method does not fully utilize fault transient state quantity information, so that the action performance of the outgoing line protection is improved by coordinating the characteristics of the transient state and the steady state.
Disclosure of Invention
The invention provides a fault protection method and a fault protection device suitable for a wind power plant outgoing line, which are used for solving at least one of the technical problems.
In a first aspect, the present invention provides a fault protection method for a wind farm outgoing line, including: acquiring and sending three-phase voltage data and three-phase current data at a line protection installation position in real time; judging whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value; if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging the certain phase to be a fault phase; calculating a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value or not; if the voltage drop degree and the three-phase voltage unbalance degree are not larger than the setting value, adopting a distance protection criterion based on a steady-state power frequency component, and performing protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range; and if the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value, judging a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation, and if the fault is in a protection area of a transmission line, performing protection action.
In a second aspect, the present invention provides a fault protection device for a wind farm outgoing line, comprising: the acquisition module is configured to acquire and send out three-phase voltage data and three-phase current data at a line protection installation position in real time; the first judgment module is configured to judge whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value; the starting module is configured to protect starting and judge that a certain phase is a fault phase if the sum of current data in any period of the certain phase in the three-phase current data is greater than a setting value; the second judgment module is configured to calculate a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data and judge whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value; the third judgment module is configured to adopt a distance protection criterion based on a steady-state power frequency component if the voltage drop degree and the three-phase voltage unbalance degree are not greater than a setting value, and perform protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range; and the fourth judgment module is configured to judge a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation if the voltage drop degree or the three-phase voltage unbalance is greater than a setting value, and perform protection action if the fault is in a protection area of the transmission line.
In a third aspect, an electronic device is provided, comprising: the system comprises at least one processor and a memory which is in communication connection with the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to execute the steps of a method for fault protection of a wind farm outgoing line according to any embodiment of the invention.
In a fourth aspect, the present invention also provides a computer-readable storage medium having stored thereon a computer program comprising program instructions which, when executed by a computer, cause the computer to perform the steps of a method for fault protection of a transmission line of a wind farm according to any of the embodiments of the present invention.
According to the fault protection method and device suitable for the wind power plant output line, the fault severity is judged according to the detected voltage drop degree and the three-phase unbalance degree, fault judgment can be accurately carried out, and therefore the reliability of protection action is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a flowchart of a fault protection method applicable to a transmission line of a wind farm according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a simulation model of a protection scheme for an outgoing line of a wind power system according to an embodiment of the present invention;
fig. 3 is a waveform comparison diagram before and after morphological filtering of a fault acquisition signal according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an action condition of a power frequency distance protection criterion according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an action condition of a fault criterion in a wind power transmission line area according to an embodiment of the present invention;
FIG. 6 is a block diagram of a fault protection device suitable for a transmission line of a wind farm according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a flow chart of a method for fault protection of a wind farm outgoing line according to the present application is shown.
As shown in fig. 1, a fault protection method for a wind farm outgoing line includes the following steps:
and S101, acquiring and sending three-phase voltage data and three-phase current data of a line protection installation position in real time.
In this embodiment, the a-phase, b-phase, c-phase current and voltage information at the line protection installation site are collected and sent out to obtain a voltage and current sampling array
And
：
in the formula,
for the number of sample array storage, the recommended sampling frequency is 20kHz, namely the number of sample points in 20ms of each power frequency cycle is 400, then the value of p is 2 times of the number of sample points of each cycle, namely corresponding to 800, thus, the sample array stores 2 cycles of sample data in total,
is composed of
、
Or
。
Step S102, judging whether the sum of current data in any period of a certain phase in the three-phase current data is larger than a setting value.
In this embodiment, when
When the sum of the current sampling values of any phase cycle in the array is greater than the setting value, the protection is started, namely:
in the formula,
the current data is sampled for the a-phase,
the data is sampled for the b-phase current,
the data is sampled for the c-phase current,
≤
≤i，
∈Z，
the number of current sampling points in each period is recommended to be 400, i is more than or equal to n +1 and less than or equal to p, and i belongs to Z;
for setting the current value, set to
。
Wherein,
the maximum sampling value of the corresponding phase current in each cycle is obtained when the line normally runs.
And step S103, if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging that the certain phase is a fault phase.
In this embodiment, determining that the certain phase is a faulty phase specifically includes: to pair
The array carries out sequence component decomposition by using a symmetrical component method, if the ratio of the zero-sequence current to the positive-sequence current is greater than a setting value, the array is judged to be a ground fault, namely:
。
in the formula,
is a zero-sequence current, and is a zero-sequence current,
the positive sequence current is adopted, and the delta is a setting threshold which is taken as 10 percent. If the above formula is not satisfied, it is determined as an inter-phase fault.
And step S104, calculating a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value.
In this embodiment, the expression for calculating the voltage sag λ and the three-phase voltage unbalance ζ is:
，
in the formula,
to the extent of the voltage drop-off,
is the effective value of the rated voltage of the line,
for the filtered voltage data
The effective value calculated by the fourier algorithm is used,
the voltage of the three phases is not balanced,
are respectively by voltage data
Calculating the effective values of the line voltages between the ab phases, the bc phase and the ca phase,
is a voltage operator.
Integrated voltage drop
And three-phase voltage unbalance
Judging the severity of the fault, wherein the judging conditions are as follows:
。
namely, as long as one of the calculated voltage drop degree and the calculated three-phase unbalance degree is more than 50%, the serious fault is immediately judged; otherwise, judging the fault as a non-serious fault.
And S105, if the voltage drop degree and the three-phase voltage unbalance degree are not greater than the setting value, adopting a distance protection criterion based on a steady-state power frequency component, and performing protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range.
In this embodiment, when it is determined that a ground fault occurs at a certain point of the transmission line, the corresponding intra-zone action criterion is:
in the formula,
in order to be the ground distance impedance,
the value is 0.8 for setting coefficient,
is the positive sequence impedance of the whole length of the protected line,Kis a zero-sequence compensation coefficient, and the zero-sequence compensation coefficient,
，
for the zero sequence impedance of the whole length of the protected line,
for the filtered voltage data
The real part calculated by the fourier algorithm is used,
for the filtered voltage data
Virtual computed using Fourier algorithmA part of the device for measuring the temperature of the object,
to the filtered current data
The real part calculated by the fourier algorithm is used,
to the filtered current data
The imaginary part calculated using the fourier algorithm,Kis a zero-sequence compensation coefficient, and the zero-sequence compensation coefficient,
is composed of filtered current data
And calculating the obtained zero sequence phasor.
When a phase-to-phase fault occurs at a certain position of the sending-out line, the corresponding in-zone action criterion is as follows:
in the formula,
is the impedance of the distance between the phases,
to fault line voltage
The real part calculated by the fourier algorithm is used,
to fault line voltage
The imaginary part calculated using the fourier algorithm,
for fault line currents
The real part calculated by the fourier algorithm is used,
for fault line currents
The imaginary part calculated using a fourier algorithm.
And S106, if the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value, judging a fault range according to the high-frequency transient state energy after the fault by adopting a transient state protection criterion based on wavelet transformation, and if the fault is in a protection area of a transmission line, performing protection action.
In the present embodiment, the current data after filtering is filtered
And (3) performing continuous wavelet transformation:
wherein e is a scale factor and takes the value of [1,
]，
is a translation factor, and the value is not more than 0
≤e，
Is a Morlet mother wavelet and is a Morlet mother wavelet,
is a coefficient matrix after continuous wavelet transform,
is a first variable, 1 is less than or equal to
≤
，
∈Z，
The number is saved for the sample array.
The frequency intervals of 0-30kHz and 30-60 kHz are divided respectively. Divided frequency interval
All are as follows:
。
at 0-60 kHz-
Calculating wavelet transform coefficient in frequency interval
Comprises the following steps:
in the formula,
is the conjugate fourier function of the Morlet mother wavelet function,
is the second variable, 0 ≦
≤ 60kHz/
，
∈Z，
Is a third variable that is a function of,
×
≤
≤ （
+1）×
，
∈Z。
calculating low frequency energy coefficients
And coefficient of high frequency energy
：
Wherein [ ] is a rounded-down operation.
Based on low frequency energy coefficients
And coefficient of high frequency energy
The criterion for constructing the fault in the wind power transmission line area is as follows:
in the formula,
the value is a set value, and the value range is 15% -25%. If the above equation is not satisfied, it is determined as an out-of-area fault.
In summary, the method of the application judges the fault severity according to the detected voltage drop degree and three-phase unbalance degree, can accurately judge the fault, and accordingly improves the reliability of protection action.
Please refer to fig. 2, which shows a schematic diagram of a simulation model of a wind power system outgoing line protection scheme according to the present application.
FIG. 2 shows a wind power plant constructed based on a PSCAD simulation platform and a wind power plant constructed based on the PSCAD simulation platformAnd (5) an outgoing line simulation model. Wherein,
、
respectively a first fault point and a second fault point, and the wind power clusters 1, 2 and 3 are called together
And each fan of the doubly-fed wind power plant is connected to a 35kV bus bar through a box transformer substation (690V/35 kV), and the voltage is increased to 110kV through a main transformer to an AB section of a sending-out line. The rated line voltage of a large power grid connected with the line AB is 110kV, and the rated operation frequency is 50 Hz. The total power of wind power output is 90 MW. The total length of the outgoing line AB is 50km, and the resistance and the inductance of the positive sequence line with unit length are respectively 0.115 omega/km and 1.052 mH/km; the resistance and the inductance of the zero sequence line with unit length are respectively 0.315 omega/km and 3.773 mH/km. The protection installation is close to wind power system exit at wind-powered electricity generation send out line. The implementation of the embodiments of the present invention will now be described by taking the segment AB of the DFIGs transmission line as an example.
Example 1
Installing relay protection equipment at a position, close to an outlet of an electric field end, of a sending line of a wind power plant, carrying out high-frequency sampling on three-phase voltage and current at 20kHz, wherein the sampling number n per period is 400, and Gaussian white noise with the signal-to-noise ratio of 20dB is added to simulate signal noise pollution, so that a voltage and current sampling array is obtained
And
。
set at 60% of the position of the feeding line AB at the time of 3s
And a BC phase-to-phase fault with the transition resistance of 50 omega occurs, at the moment, the protection device performs protection starting and fault type judgment in real time according to the acquired data, and the BC phase-to-phase fault is calculated as follows:
thus protecting the boot. And then carrying out sequence component decomposition on the current sampling array Im, judging the fault type, and calculating:
and therefore, a phase-to-phase fault is determined.
Determining the definition domain of the structural element STR as
The definition domains of fault phase and phase current are
. Filtering the sampling signals of the phase voltage and the phase current of the fault phase after the fault, taking the average value of two times of form open-close cascade operation as the output, and obtaining the filtering output of the voltage signal as
The filtered output of the current signal is
. Fig. 3 shows the comparison of the waveforms of the fault phase voltage and current before and after filtering, which shows that the used morphological cascade filtering method has excellent denoising effect.
For the filtered voltage data
Calculating the effective voltage value of the protection installation position by adopting a Fourier algorithm, and calculating the voltage drop degree according to the effective voltage value
And three-phase voltage unbalance
：
The fault is thus determined to be a non-critical type of fault.
Using a distance protection criterion fault range based on a steady state power frequency component:
and (3) adopting data 20ms after fault starting, and adopting a mode of calculating interphase impedance to carry out fault segmentation because the phase judgment result is interphase fault:
therefore, the protection is cut off quickly when the fault is determined to be an in-zone fault. Fig. 4 shows the behavior of the power frequency distance protection criterion. In FIG. 4, the magnitude of the intermediate impedance rapidly increases and then remains stable after the 3s fault occurs, and the magnitude of the intermediate impedance is always smaller than that of the intermediate impedance
That is, it means that it is determined as an intra-area failure.
Example 2
Installing relay protection equipment at a position, close to an outlet of an electric field end, of a sending line of a wind power plant, carrying out high-frequency sampling on three-phase voltage and current at 20kHz, wherein the sampling number n per period is 400, and Gaussian white noise with the signal-to-noise ratio of 20dB is added to simulate signal noise pollution, so that a voltage and current sampling array is obtained
And
。
is arranged at 30% of the position of the delivery line AB at the moment of 3s
The three-phase short circuit fault with the transition resistance of 3 omega is generated, at the moment, the protection device performs protection starting and fault type judgment in real time according to the collected data, and the three-phase short circuit fault is calculated as follows:
thus protecting the boot. Then sampling array for current
Performing sequence component decomposition, judging the fault type, and calculating:
and therefore is discriminated as a phase-to-phase fault.
Determining the definition domain of the structural element STR as
The definition domains of the fault phase voltage and the phase current are
. Filtering the sampling signals of the phase voltage and the phase current of the fault phase after the fault, taking the average value of two times of form open-close cascade operation as the output, and obtaining the filtering output of the voltage signal as
The filtered output of the current signal is
。
For the filtered voltage data
Calculating the voltage of the protection installation position by adopting Fourier algorithmEffective value and calculating the voltage drop degree according to the effective value
And three-phase voltage unbalance
：
And thus determines the fault as a critical type fault.
The data of the fault phase current 2.5ms after the fault is adopted to carry out wavelet transformation on the data to obtain the low-frequency energy coefficient
0.27, high frequency energy coefficient
The criterion of the fault in the wind power transmission line area is 0.65:
therefore, the protection is cut off quickly when the fault is determined to be an in-zone fault. Fig. 5 shows the action condition of the fault criterion in the wind power transmission line area. In FIG. 5
Increases rapidly after the 3s fault occurs and its value is greater than the set value of 25%
That is, it means that it is determined as an intra-area failure.
In summary, the embodiment verifies the correctness and feasibility of the invention, the fault protection method suitable for the wind power plant output line can accurately judge the fault, improves the reliability of the protection action, and can accelerate the fault isolation by criterion switching under the condition of serious fault.
Referring to fig. 6, a block diagram of a fault protection device suitable for a wind farm outgoing line is shown.
As shown in fig. 6, the fault protection device 200 includes an acquisition module 210, a first determination module 220, a starting module 230, a second determination module 240, a third determination module 250, and a fourth determination module 260.
The acquisition module 210 is configured to acquire and send three-phase voltage data and three-phase current data of a line protection installation position in real time;
the first judging module 220 is configured to judge whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value;
the starting module 230 is configured to protect starting and determine that a certain phase is a fault phase if the sum of current data in any period of the certain phase in the three-phase current data is greater than a setting value;
the second judging module 240 is configured to calculate a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judge whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value;
a third judging module 250 configured to perform a protection action when the calculated inter-phase distance impedance or the calculated ground distance impedance is within a preset range by using a distance protection criterion based on a steady-state power frequency component if the voltage drop degree and the three-phase voltage unbalance are not greater than a setting value;
and the fourth judging module 260 is configured to judge a fault range according to the magnitude of high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation if the voltage drop degree or the three-phase voltage unbalance is greater than a setting value, and perform a protection action if the fault is in a protection area of the transmission line.
It should be understood that the modules recited in fig. 6 correspond to various steps in the method described with reference to fig. 1. Thus, the operations and features described above for the method and the corresponding technical effects are also applicable to the modules in fig. 6, and are not described again here.
In other embodiments, an embodiment of the present invention further provides a computer-readable storage medium, where computer-executable instructions are stored, and the computer-executable instructions may execute the fault protection method applicable to the outgoing line of the wind farm in any of the method embodiments described above;
as one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions configured to:
acquiring and sending three-phase voltage data and three-phase current data at a line protection installation position in real time;
judging whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value;
if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging the certain phase to be a fault phase;
calculating a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value or not;
if the voltage drop degree and the three-phase voltage unbalance degree are not larger than the setting value, adopting a distance protection criterion based on a steady-state power frequency component, and performing protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range;
and if the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value, judging a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation, and if the fault is in a protection area of a transmission line, performing protection action.
The computer-readable storage medium may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created from use of a fault protection device suitable for a wind farm outgoing line, and the like. Further, the computer-readable storage medium may include high speed random access memory, and may also include memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the computer readable storage medium optionally includes memory remotely located from the processor, and these remote memories may be connected over a network to a fault protection device adapted for use with the wind farm outgoing lines. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 7, the electronic device includes: a processor 310 and a memory 320. The electronic device may further include: an input device 330 and an output device 340. The processor 310, the memory 320, the input device 330, and the output device 340 may be connected by a bus or other means, as exemplified by the bus connection in fig. 7. The memory 320 is the computer-readable storage medium described above. The processor 310 executes various functional applications and data processing of the server by running nonvolatile software programs, instructions and modules stored in the memory 320, namely, the method for fault protection of the wind farm outgoing line is realized. Input device 330 may receive entered numerical or character information and generate key signal inputs related to user settings and functional controls of the fault protection device suitable for the wind farm transmission line. The output device 340 may include a display device such as a display screen.
The electronic device can execute the method provided by the embodiment of the invention, and has the corresponding functional modules and beneficial effects of the execution method. For technical details that are not described in detail in this embodiment, reference may be made to the method provided by the embodiment of the present invention.
As an embodiment, the electronic device is applied to a fault protection device suitable for a wind farm outgoing line, and is used for a client, and the fault protection device comprises: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to cause the at least one processor to:
acquiring and sending three-phase voltage data and three-phase current data at a line protection installation position in real time;
judging whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value;
if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging the certain phase to be a fault phase;
calculating a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value or not;
if the voltage drop degree and the three-phase voltage unbalance degree are not larger than the setting value, adopting a distance protection criterion based on a steady-state power frequency component, and performing protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range;
and if the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value, judging a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation, and if the fault is in a protection area of a transmission line, performing protection action.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods of the various embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. A fault protection method suitable for a wind power plant outgoing line is characterized by comprising the following steps:
acquiring and sending three-phase voltage data and three-phase current data at a line protection installation position in real time;
judging whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value;
if the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value, starting protection, and judging the certain phase to be a fault phase;
calculating a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data, and judging whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value or not;
if the voltage drop degree and the three-phase voltage unbalance degree are not larger than the setting value, adopting a distance protection criterion based on a steady-state power frequency component, and performing protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range;
and if the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value, judging a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation, and if the fault is in a protection area of a transmission line, performing protection action.
2. The fault protection method suitable for the wind power plant transmission line according to claim 1, characterized in that after protection starting, the collected three-phase voltage data and three-phase current data are preprocessed based on an on-off and an on-off cascade filter algorithm after the fault occurs.
3. The method according to claim 1, wherein the step of determining that the certain phase is the fault phase specifically comprises:
performing sequence component decomposition on the three-phase current data, and judging whether the ratio of the zero-sequence current to the positive-sequence current is greater than a preset value;
if the ratio of the zero-sequence current to the positive-sequence current is larger than a preset value, determining that the certain phase is a ground fault;
and if the ratio of the zero-sequence current to the positive-sequence current is not greater than a preset value, determining that the certain phase is an interphase fault.
4. The fault protection method suitable for the wind power plant transmission line according to claim 1, wherein the expressions for calculating the voltage sag degree and the three-phase voltage unbalance degree are as follows:
in the formula,
to the extent of the voltage drop-off,
is the effective value of the rated voltage of the line,
for the filtered voltage data
The effective value calculated by the fourier algorithm is used,
the voltage of the three phases is not balanced,
are respectively by voltage data
Calculating the effective values of the line voltages between the ab phases, the bc phase and the ca phase,
is a voltage operator.
5. The fault protection method suitable for the wind power plant transmission line according to claim 1, wherein the step of performing protection when the calculated inter-phase distance impedance or the ground distance impedance is within a preset range by using a distance protection criterion based on a steady-state power frequency component comprises:
carrying out full-wave Fourier transform and symmetrical component transform on three-phase current data and three-phase voltage data of a power frequency period after the fault transient process;
calculating a ground distance impedance based on the converted three-phase current data and the converted three-phase voltage data
And phase distance impedance
Wherein the ground distance impedance is calculated
The expression of (a) is:
in the formula,
for the filtered voltage data
The real part calculated by the fourier algorithm is used,
for the filtered voltage data
The imaginary part calculated using the fourier algorithm,
to the filtered current data
The real part calculated by the fourier algorithm is used,
to the filtered current data
The imaginary part calculated using the fourier algorithm,Kis a zero-sequence compensation coefficient, and the zero-sequence compensation coefficient,
is composed of filtered current data
Calculating the obtained zero sequence phasor;
calculating interphase distance impedance
The expression of (a) is:
in the formula,
to fault line voltage
The real part calculated by the fourier algorithm is used,
to fault line voltage
The imaginary part calculated using the fourier algorithm,
for fault line currents
The real part calculated by the fourier algorithm is used,
for fault line currents
An imaginary part calculated by adopting a Fourier algorithm;
when the calculated inter-phase distance impedance or the calculated grounding distance impedance is in a preset range, namely falls into an impedance circle, judging as an in-zone fault, and performing protection action; otherwise, an out-of-range fault is declared.
6. The method for fault protection of a wind farm outgoing line according to claim 1, wherein the determining the fault range according to the magnitude of the high frequency transient energy after the fault by using the transient protection criterion based on the wavelet transform comprises:
processing a current signal 2.5ms after the fault based on synchronous extrusion wavelet transform to obtain a component corresponding to the frequency of 0-30kHz and a component corresponding to the frequency of 30kHz-60 kHz;
respectively calculating energy coefficients associated with the 0-30kHz frequency corresponding component and the 30kHz-60kHz frequency corresponding component;
judging whether the ratio of the energy coefficient related to the component corresponding to the frequency of 30kHz-60kHz to the total energy coefficient is higher than a set value or not;
if the ratio of the energy coefficient related to the component corresponding to the frequency of 30kHz-60kHz to the total energy coefficient is higher than a set value, determining that the fault is in the sending-out line area;
and if the ratio of the energy coefficient related to the component corresponding to the frequency of 30kHz-60kHz to the total energy coefficient is not higher than a set value, judging that the fault is outside the sending line area.
7. A fault protection device suitable for a wind farm outgoing line, comprising:
the acquisition module is configured to acquire and send out three-phase voltage data and three-phase current data at a line protection installation position in real time;
the first judgment module is configured to judge whether the sum of current data in any period of a certain phase in the three-phase current data is greater than a setting value;
the starting module is configured to protect starting and judge that a certain phase is a fault phase if the sum of current data in any period of the certain phase in the three-phase current data is greater than a setting value;
the second judgment module is configured to calculate a voltage drop degree and a three-phase voltage unbalance degree based on the three-phase voltage data and judge whether the voltage drop degree or the three-phase voltage unbalance degree is greater than a setting value;
the third judgment module is configured to adopt a distance protection criterion based on a steady-state power frequency component if the voltage drop degree and the three-phase voltage unbalance degree are not greater than a setting value, and perform protection action when the calculated inter-phase distance impedance or grounding distance impedance is within a preset range;
and the fourth judgment module is configured to judge a fault range according to the high-frequency transient energy after the fault by adopting a transient protection criterion based on wavelet transformation if the voltage drop degree or the three-phase voltage unbalance is greater than a setting value, and perform protection action if the fault is in a protection area of the transmission line.
8. An electronic device, comprising: at least one processor, and a memory communicatively coupled to the at least one processor, wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any of claims 1 to 6.
9. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method of any one of claims 1 to 6.
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Application publication date: 20210924 Assignee: JIANGXI KANGWEI ELECTRICAL TECHNOLOGY Co.,Ltd. Assignor: STATE GRID JIANGXI ELECTRIC POWER COMPANY LIMITED Research Institute Contract record no.: X2023980033846 Denomination of invention: A fault protection method and device suitable for transmission lines in wind farms Granted publication date: 20211231 License type: Common License Record date: 20230320 |