Transmission line protection method and system based on power spectrum analysis, and medium

Abstract

The invention discloses a sending-out line protection method and system based on power spectrum analysis and a medium, and belongs to the field of relay protection, and the method comprises the steps: respectively obtaining current signals corresponding to the two ends of a system side and a wind power plant side, and judging whether a line fault exists or not based on the current signals, the current signal comprises a first current signal and a second current signal; if the line fault exists, power spectrums corresponding to the two ends of the system side and the wind power plant side are calculated respectively, the current power difference between the two ends of the system side and the wind power plant side is obtained based on the power spectrums, and the power spectrums comprise the first power spectrum and the second power spectrum; and if the current power difference value exceeds a preset threshold value, determining that the fault type is a fault in the sending-out line area, and starting a protection action of the sending-out line. The method can adapt to the complex fault current characteristics of the wind power plant, and ensures the accuracy and reliability of the transmission line protection method.

Description

Technical Field

[0001] This application relates to the field of relay protection, and in particular, to a transmission line protection method, system and medium based on power spectrum analysis. Background Art

[0002] The expansion of wind farm scale and technological progress have played an important role in the energy field, leading to a new trend of efficiently coupling wind farms with the distribution network. However, during the coupling process to the distribution network, the electrical characteristics on the wind farm side are significantly different from those of traditional power systems. Specifically, the current on the wind farm side is not static and constant, but is deeply affected by various complex factors such as wind speed, wind direction, and the operating state of wind turbines, thus showing great volatility and uncertainty. The cumulative effect of these factors undoubtedly poses unprecedented complex challenges to the protection work of the power system.

[0003] However, traditional power system protection methods mainly rely on changes in electrical quantities such as current, voltage, and impedance to judge internal and external faults. But after the widespread access of wind farms, the structure and characteristics of the power system have changed significantly. Specifically, on the one hand, the fault current of wind farms often shows a weak-feed characteristic, that is, when a fault occurs, the fault current provided by the wind farm is relatively small, which may lead to difficulty in accurately triggering traditional overcurrent protection and even misjudgment. On the other hand, the fault current of wind farms may also have a frequency shift characteristic, that is, the frequency of the fault current may deviate from the frequency range of the normal power system, which further increases the difficulty of judging faults by traditional protection methods. Therefore, in the face of the new challenges brought by the access of wind farms, traditional power system protection methods need to be improved and innovated accordingly to meet the development needs of new energy power systems and ensure the accuracy and reliability of protection methods.

[0004] Application content

[0005] This application provides a transmission line protection method, system and medium based on power spectrum analysis, belonging to the field of relay protection, which can solve the problem of difficult accurate triggering of overcurrent protection in the prior art, adapt to the complex fault current characteristics of wind farms, and ensure the accuracy and reliability of the transmission line protection method.

[0006] In a first aspect, this application provides a transmission line protection method based on power spectrum analysis, including:

[0007] Obtain the corresponding current signals at both ends of the system side and the wind farm side respectively, and judge whether there is a line fault based on the current signals, where the current signals include a first current signal and a second current signal;

[0008] If there is a line fault, calculate the corresponding power spectra at both ends of the system side and the wind farm side respectively, and obtain the current power difference at both ends of the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum;

[0009] If the current power difference exceeds a preset threshold, determine that the fault type is a fault within the outgoing line area, and initiate the protection action of the outgoing line.

[0010] In the embodiments of the present application, by respectively obtaining the current signals corresponding to both ends of the system side and the wind farm side, and judging whether there is a line fault based on the current signals, it is possible to accurately judge whether there is a line current fault on the system side and the wind farm side, which is convenient for further analyzing the line with the line current fault subsequently to determine the corresponding outgoing line protection method; by further analyzing the system side or the wind farm side with the line current fault, calculating the corresponding power spectra and the current power difference, it is possible to obtain the current power difference that accurately reflects the change of the fault current of the wind farm, and then it is convenient to effectively distinguish between faults within the area and faults outside the area subsequently, and accurately initiate the corresponding outgoing line protection method; by judging whether the current power difference exceeds a preset threshold, it is possible to effectively distinguish between faults within the area and faults outside the area, and accurately initiate the corresponding outgoing line protection method. Compared with the prior art, the present application can adapt to the complex fault current characteristics of the wind farm and ensure the accuracy and reliability of the outgoing line protection method.

[0011] Further, the judging whether there is a line fault based on the current signal specifically is:

[0012] Calculate the current difference between the third current signal corresponding to both ends of the system side and the wind farm side at the previous moment and the fourth current signal corresponding to the current moment;

[0013] Judge whether the current difference meets a preset condition. If the preset condition is met, there is a line fault.

[0014] In this way, by calculating the current mutation value, it is possible to judge whether the current signals corresponding to the system side and the wind farm side have current mutations, and then judge whether there is a line fault on the corresponding side, which can accurately judge whether there is a line current fault on the system side and the wind farm side, and is convenient for further analyzing the line with the line current fault subsequently to determine the corresponding outgoing line protection method.

[0015] Further, the respectively calculating the power spectra corresponding to both ends of the system side and the wind farm side specifically is:

[0016] Based on the current signals, respectively determine the covariance matrices corresponding to both ends of the system side and the wind farm side, where the covariance matrices include a first covariance matrix and a second covariance matrix;

[0017] Perform eigenvalue decomposition on the covariance matrix respectively to obtain the corresponding eigenvalues, and determine the corresponding noise matrices respectively based on the eigenvalues, where the noise matrices include a first noise matrix and a second noise matrix;

[0018] Based on the noise matrices and the preset direction response vector, obtain the corresponding power spectra at both ends of the system side and the wind farm side respectively, where the power spectra include a first power spectrum and a second power spectrum.

[0019] In this way, by further analyzing the system side or the wind farm side with line current faults, the corresponding power spectra can be accurately calculated, which is convenient for obtaining the current power difference that accurately reflects the change of the fault current in the wind farm, and then is convenient for effectively distinguishing internal faults and external faults subsequently, and accurately starting the corresponding transmission line protection method.

[0020] Further, the calculation formula for obtaining the corresponding power spectra at both ends of the system side and the wind farm side is specifically:

[0021]

[0022] In the formula, P A (f) is the first power spectrum corresponding to the system side, P B (f) is the second power spectrum corresponding to the wind farm side, a is the direction response vector, H is the transpose, f is the frequency, E A is the first noise matrix, E B is the second noise matrix, and a(f) is the value of the direction response vector at frequency f.

[0023] Further, obtaining the current power difference between the system side and the wind farm side based on the power spectra is specifically:

[0024] Obtain the power frequency and non-power frequency power corresponding to both ends of the system side and the wind farm side respectively;

[0025] Based on the power frequency and the non-power frequency power, obtain the first frequency difference and the second frequency difference corresponding to both ends of the system side and the wind farm side respectively;

[0026] Based on the first frequency difference and the second frequency difference, obtain the current power difference between the system side and the wind farm side.

[0027] In this way, by further analyzing the system side or the wind farm side with line current faults, calculating the corresponding power spectra and current power differences, the current power difference that accurately reflects the change of the fault current in the wind farm can be obtained, and then it is convenient for effectively distinguishing internal faults and external faults subsequently, and accurately starting the corresponding transmission line protection method.

[0028] In a second aspect, the present application provides a transmission line protection system based on power spectrum analysis, including: an acquisition module, a processing module, and a protection module;

[0029] The acquisition module is configured to respectively acquire current signals corresponding to both ends of the system side and the wind farm side, and determine whether there is a line fault based on the current signals, where the current signals include a first current signal and a second current signal;

[0030] The processing module is configured to, if there is a line fault, respectively calculate the power spectra corresponding to both ends of the system side and the wind farm side, and obtain the current power difference between the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum;

[0031] The protection module is configured to, if the current power difference exceeds a preset threshold, determine that the fault type is a fault within the transmission line area, and initiate the protection action of the transmission line.

[0032] In the embodiment of the present application, by respectively acquiring the current signals corresponding to both ends of the system side and the wind farm side, and determining whether there is a line fault based on the current signals, it is possible to accurately determine whether there is a line current fault on the system side and the wind farm side, facilitating subsequent further analysis of the line with a line current fault to determine the corresponding transmission line protection method; by further analyzing the system side or the wind farm side with a line current fault, calculating the corresponding power spectrum and current power difference, it is possible to obtain a current power difference that accurately reflects the change of the fault current in the wind farm, thereby facilitating subsequent effective distinction between in - zone faults and out - of - zone faults, and accurately initiating the corresponding transmission line protection method; by determining whether the current power difference exceeds a preset threshold, it is possible to effectively distinguish in - zone faults and out - of - zone faults, and accurately initiate the corresponding transmission line protection method. Compared with the prior art, the present application can adapt to the complex fault current characteristics of the wind farm, ensuring the accuracy and reliability of the transmission line protection method.

[0033] Further, the acquisition module includes: a calculation unit and a judgment unit;

[0034] The calculation unit is configured to calculate the current difference between the third current signal corresponding to both ends of the system side and the wind farm side at the previous moment and the fourth current signal corresponding to the current moment;

[0035] The judgment unit is configured to judge whether the current difference meets a preset condition, and if it meets the preset condition, there is a line fault.

[0036] Further, the processing module includes: a first processing unit, a second processing unit, and a third processing unit;

[0037] The first processing unit is configured to respectively determine covariance matrices corresponding to both ends of the system side and the wind farm side based on the current signal, where the covariance matrices include a first covariance matrix and a second covariance matrix;

[0038] The second processing unit is configured to respectively perform eigenvalue decomposition on the covariance matrices to obtain corresponding eigenvalues, and respectively determine corresponding noise matrices based on the eigenvalues, where the noise matrices include a first noise matrix and a second noise matrix;

[0039] The third processing unit is configured to respectively obtain power spectra corresponding to both ends of the system side and the wind farm side based on the noise matrices and a preset direction response vector, where the power spectra include a first power spectrum and a second power spectrum.

[0040] Further, the processing module further includes: an acquisition unit, a fourth processing unit, and a fifth processing unit;

[0041] The acquisition unit is configured to respectively acquire the power frequency and non-power frequency power corresponding to both ends of the system side and the wind farm side;

[0042] The fourth processing unit is configured to respectively obtain a first frequency difference and a second frequency difference corresponding to both ends of the system side and the wind farm side based on the power frequency and the non-power frequency power;

[0043] The fifth processing unit is configured to obtain the current power difference between both ends of the system side and the wind farm side based on the first frequency difference and the second frequency difference.

[0044] In a third aspect, the present application further provides a computer-readable storage medium, characterized in that the computer-readable storage medium includes a stored computer program, where when the computer program runs, it controls the device where the computer-readable storage medium is located to execute a transmission line protection method based on power spectrum analysis as described in the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a circuit schematic diagram of a wind farm coupled with a distribution network provided by the present application;

[0046] Figure 2 is a flowchart of an embodiment of a transmission line protection method based on power spectrum analysis provided by the present application;

[0047] Figure 3 is a diagram showing the current difference between both ends of the system side and the wind farm side provided by the present application;

[0048] Figure 4 is a diagram showing the frequency difference between both ends of the system side and the wind farm side provided by the present application;

[0049] Figure 5 It is a schematic diagram of the current power difference between the system side and the wind farm side provided by this application;

[0050] Figure 6 It is a schematic structural diagram of an embodiment of a transmission line protection system based on power spectrum analysis provided by this application. Specific embodiments

[0051] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of this application.

[0052] It should be understood that the step numbers used in the text are only for convenience of description and do not limit the order of execution of the steps.

[0053] It should be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0054] The terms "include" and "comprise" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0055] The term " / and / " refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0056] The expansion of wind farm scale and technological progress play an important role in the energy field, promoting the efficient coupling of wind farms and distribution networks. However, the electrical characteristics of wind farms are significantly different from those of traditional power systems. Its current is affected by factors such as wind speed and wind direction, showing large volatility and uncertainty, bringing complex challenges to the protection work of power systems. Traditional power system protection methods mainly rely on changes in current, voltage and impedance to judge faults. However, after the widespread access of wind farms, the structure and characteristics of power systems have changed significantly. The fault current of wind farms often shows weak feed characteristics, which may lead to the failure of traditional overcurrent protection; at the same time, the fault current may have frequency shift characteristics, increasing the difficulty of fault judgment. Therefore, traditional protection methods need to be improved and innovated to meet the development needs of new energy power systems and ensure the accuracy and reliability of protection methods.

[0057] Next, the nouns involved in this application are parsed:

[0058] Covariance matrix, in statistics and probability theory, each element of the covariance matrix is the covariance between the vector elements, which is a natural generalization from scalar random variables to high-dimensional random vectors.

[0059] Eigendecomposition, also known as spectral decomposition, is an important concept in linear algebra, which decomposes a square matrix A into the form of eigenvalues and eigenvectors.

[0060] MUSIC (Multiple Signal Classification), multiple signal classification, is a class of spatial spectrum estimation algorithms. Its idea is to perform eigen-decomposition on the covariance matrix (Rx) of the received data to separate the signal subspace and the noise subspace, and use the orthogonality between the signal direction vector and the noise subspace to construct a spatial scanning spectrum for global search of spectral peaks, so as to realize the parameter estimation of the signal.

[0061] Based on this, the embodiments of this application provide a transmission line protection method, system and medium based on power spectrum analysis, which can adapt to the complex fault current characteristics of the wind farm and ensure the accuracy and reliability of the transmission line protection method.

[0062] A transmission line protection method, system and medium based on power spectrum analysis provided by the embodiments of this application are specifically described through the following embodiments. First, the transmission line protection method based on power spectrum analysis in the embodiments of this application is described.

[0063] The transmission line protection method based on power spectrum analysis provided by the embodiments of this application relates to the field of power system communication. The transmission line protection method based on power spectrum analysis provided by the embodiments of this application can be applied to terminals, servers, or software running on terminals or servers. In some embodiments, the terminal can be a smart phone, a tablet computer, a notebook computer, a desktop computer, etc.; the server can be configured as an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server providing basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN, and big data and artificial intelligence platforms; the software can be an application implementing a transmission line protection method based on power spectrum analysis, etc., but is not limited to the above forms.

[0064] This application can also be used in numerous general-purpose or special-purpose computer system environments or configurations. For example: personal computers, server computers, handheld or portable devices, tablet devices, multiprocessor systems, microprocessor-based systems, set-top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments including any of the above systems or devices, and so on. This application can be described in the general context of computer-executable instructions executed by a computer, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. This application can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected through a communication network. In a distributed computing environment, program modules can be located in local and remote computer storage media including storage devices.

[0065] Please refer to Figure 1 , Figure 1 which is a circuit schematic diagram of a wind farm coupled to a distribution network. In this diagram, the wind farm converts wind energy into electrical energy, and its output voltage and current vary according to conditions such as wind speed. Then, through a step-up substation, the low-voltage electrical energy generated by the wind farm is stepped up to the voltage level of the distribution network, and then the electrical energy is sent into the distribution network (i.e., the system power supply in the figure) through the outgoing line. When the wind farm is connected to the distribution network, certain current and voltage changes will occur at the connection point. Therefore, through circuit diagram analysis, the voltage and current values of each node can be calculated to evaluate the impact of the wind farm on the distribution network.

[0066] Please refer to Figure 2 , Figure 2 which is a flowchart of an embodiment of a protection method for an outgoing line based on power spectrum analysis provided by this application, including steps S101 to S103;

[0067] Step S101: Obtain the corresponding current signals at both the system side and the wind farm side respectively, and determine whether there is a line fault based on the current signals. Among them, the current signals include a first current signal and a second current signal;

[0068] It can be understood that a current transformer (CT) can be installed on the power line on the system side (usually the grid connection point or substation) to convert the large current into a smaller secondary current. Subsequently, a high-precision current measurement instrument or data acquisition device is selected to collect the corresponding first current signal I A (t) on the system side; a current measurement device is installed on the power line on the wind farm side (including but not limited to the collector line, the outlet of the step-up transformer, etc.) to collect the corresponding second current signal I B (t) on the wind farm side.

[0069] When the first current signal I corresponding to the system side is collected A (t) and the second current signal I corresponding to the wind farm side B (t), it is necessary to calculate the third current signal I corresponding to both ends of the system side and the wind farm side at the previous moment A (t - 1) and the current difference between the fourth current signal I corresponding to the current moment B (t - 1), that is, ΔI A = I A (t) - I A (t - 1); ΔI B = I B (t) - I B (t - 1), where ΔI A and ΔI B are respectively the current difference of the first current signal on the system side and the second current difference on the wind farm side, I A (t) and I A (t - 1) are respectively the first current signal and the third current signal corresponding to the system side at time t and time t - 1, I B (t) and I B (t - 1) are respectively the second current signal and the fourth current signal corresponding to the wind farm side at time t and time t - 1. Subsequently, it is respectively determined whether the current difference ΔI of the first current signal A and the second current difference ΔI B meet the preset conditions, that is, whether they exceed the preset fault threshold. If it exceeds the preset fault threshold, it is considered that the corresponding current signal has a current mutation, and then it is determined that there is a line fault. If there is a line fault, it is necessary to further analyze the current signal; if it does not exceed the preset fault threshold, there is no line fault, and it is necessary to continuously monitor the current signals at both ends of the system side and the wind farm side. Among them, the schematic diagram of the current difference at both ends of the system side and the wind farm side is as shown in Figure 3 .

[0070] In this way, by calculating the current mutation value, it is possible to determine whether the current signals corresponding to the system side and the wind farm side have current mutations, and then determine whether there are line faults on the corresponding sides, and it is possible to accurately judge whether there are line current faults on the system side and the wind farm side, which is convenient for further analyzing the line with line current faults subsequently to determine the corresponding outgoing line protection method.

[0071] Step S102, if there is a line fault, calculate the power spectra corresponding to both ends of the system side and the wind farm side respectively, and obtain the current power difference between both ends of the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum;

[0072] It is understandable that if there is a line fault, for the current signals corresponding to both the system side and the wind farm ends within the time window (i.e., the first current signal I A (t) and the second current signal I B (t)), the corresponding first power spectrum P A (f) and the second power spectrum P B (f) are calculated using the super-resolution power spectrum algorithm. Among them, the super-resolution power spectrum algorithm can be but is not limited to the music algorithm. The specific calculation process is as follows: First, based on the current signals, the covariance matrices corresponding to both the system side and the wind farm side are determined respectively. Among them, the covariance matrix includes the first covariance matrix R A and the second covariance matrix R B . The calculation formulas for the covariance matrices are respectively: In the formula, R A is the first covariance matrix, n is the amount of data, I A = [I A (t1), I A (t2), …, I A (t n )] is the first current signal, H represents matrix transpose, R B is the second covariance matrix, I B = [I B (t1), I B (t2), …, I B (t n )] is the second current signal. Secondly, the eigenvalue decompositions are respectively performed on the covariance matrices (i.e., the first covariance matrix R A and the second covariance matrix R B ) to obtain the corresponding eigenvalues, and the corresponding noise matrices are determined respectively based on the eigenvalues. Among them, the eigenvalues include the first eigenvalue v i and the second eigenvalue e i . The relevant formulas for the eigenvalue decomposition of the covariance matrix are: R A = AR A A H + s 2 I, R B = BR B B H + s 2 I. In the formula, R A is the first covariance matrix, R B is the second covariance matrix, A and B are both signal basis matrices, H is the conjugate transpose operator of the matrix, s 2 is the intensity of the noise, I is the identity matrix, which is used to ensure the dimension adaptation of matrix operations; the calculation formulas for the relevant decomposition results are: A H vi = 0, i = D + 1, D + 2, ..., M, B H e i = 0, i = D + 1, D + 2, ..., M, where v i is the first eigenvalue; D is the dimension of the signal subspace, representing the number of eigenvectors of the effective signal, satisfying D ≤ M; M is the dimension of the covariance matrix, representing the size of the signal vector; i is the index of the eigenvector, used to distinguish different eigenvectors. Then, based on the eigenvalue (i.e., the first eigenvalue v i and the second eigenvalue e i ), the corresponding noise matrices are constructed, namely the first noise matrix E A and the second noise matrix E B , where the expression of the noise matrix is: E A = [v D+1 , v D+2 ,... v M , E B = [e D+1 , e D+2 ,... e M . Finally, based on the noise matrix E and the preset direction response vector a, the corresponding power spectra P(f) at both ends of the system side and the wind farm side are obtained respectively, where the power spectrum includes the first power spectrum P A (f) and the second power spectrum P B (f). The calculation formula for obtaining the corresponding power spectra at both ends of the system side and the wind farm side is specifically:

[0073]

[0074] where P A (f) is the first power spectrum corresponding to the system side, P B (f) is the second power spectrum corresponding to the wind farm side, H is the transpose, f is the frequency, E A is the first noise matrix, E B is the second noise matrix, a(f) is the value of the direction response vector at frequency f, a is the direction response vector, and the expression is: a(f) = [1 e -jf … e -j(M-1)f , where j is the imaginary unit.

[0075] In this way, by further analyzing the system side or the wind farm side with line current faults, the corresponding power spectra can be accurately calculated, facilitating the subsequent acquisition of the current power difference that accurately reflects the change of the fault current in the wind farm, and further facilitating the subsequent effective discrimination between in-zone faults and out-of-zone faults and accurately starting the corresponding transmission line protection method.

[0076] After obtaining the corresponding power spectra on the system side and the wind farm side (i.e., the first power spectrum P A (f) and the second power spectrum P B (f)), the current power difference ΔP between the two ends of the system side and the wind farm side can be obtained based on the power spectra. Specifically: First, obtain the power frequency f 工 corresponding to both ends of the system side and the wind farm side and the non-power frequency power respectively; Second, based on the power frequency f 工 and the non-power frequency power, obtain the corresponding first frequency difference ΔP A and the second frequency difference ΔP B between the two ends of the system side and the wind farm side respectively. The schematic diagram of the frequency difference between the two ends of the system side and the wind farm side is as shown in Figure 4 . The calculation formula is: In the formula, ΔP A is the first frequency difference corresponding to the system side, P A (f) is the first power spectrum, P B (f) is the second frequency difference corresponding to the wind farm side, P B (f) is the second power spectrum, and f 工 is the power frequency. Finally, based on the first frequency difference ΔP A and the second frequency difference ΔP B , obtain the current power difference ΔP between the two ends of the system side and the wind farm side, that is, ΔP = ΔP A - ΔP B . Among them, the schematic diagram of the current power difference between the two ends of the system side and the wind farm side is as shown in Figure 5 .

[0077] In this way, by further analyzing the system side or the wind farm side with line current faults, calculating the corresponding power spectra and current power differences, the current power differences that can accurately reflect the changes in the fault current of the wind farm can be obtained, which is convenient for effectively distinguishing internal faults and external faults in the subsequent process and accurately starting the corresponding transmission line protection method.

[0078] Step S103, if the current power difference exceeds the preset threshold, determine that the fault type is an internal fault in the transmission line area and start the protection action of the transmission line.

[0079] It is understandable that after obtaining the current power difference ΔP between the system side and the wind farm side, it is necessary to determine whether the current power difference ΔP exceeds a preset threshold λ. If the current power difference ΔP exceeds the preset threshold λ, that is, ΔP>λ, it is determined that the fault type is a fault within the outgoing line area, and the protection action of the outgoing line is started, that is, the circuit breakers at both ends of the transmission line act to disconnect the transmission line from the system; if the current power difference ΔP does not exceed the preset threshold λ, that is, ΔP≤λ, it is determined that the fault type is a fault outside the outgoing line area, and the protection action is not started.

[0080] In the embodiment of the present application, by respectively obtaining the current signals corresponding to both ends of the system side and the wind farm side, and judging whether there is a line fault based on the current signals, it is possible to accurately judge whether there is a line current fault on the system side and the wind farm side, which is convenient for further analyzing the line with the line current fault subsequently to determine the corresponding outgoing line protection method; by further analyzing the system side or the wind farm side with the line current fault, calculating the corresponding power spectrum and current power difference, it is possible to obtain the current power difference that accurately reflects the change of the fault current of the wind farm, and then it is convenient to effectively distinguish the in-area fault and the out-of-area fault subsequently, and accurately start the corresponding outgoing line protection method; by judging whether the current power difference exceeds the preset threshold, it is possible to effectively distinguish the in-area fault and the out-of-area fault, and accurately start the corresponding outgoing line protection method. Compared with the prior art, the present application can adapt to the complex fault current characteristics of the wind farm, ensuring the accuracy and reliability of the outgoing line protection method.

[0081] Please refer to Figure 6 , Figure 6 FIG. is a schematic structural diagram of an embodiment of an outgoing line protection system based on power spectrum analysis provided by the present application, including an acquisition module 100, a processing module 200, and a protection module 300;

[0082] The acquisition module 100 is used to respectively obtain the current signals corresponding to both ends of the system side and the wind farm side, and judge whether there is a line fault based on the current signals, where the current signals include a first current signal and a second current signal;

[0083] It is understandable that a current transformer (CT) can be installed on the power line on the system side (usually the grid access point or substation) to convert the large current into a smaller secondary current, and then a high-precision current measuring instrument or data acquisition device is selected to collect the first current signal I A (t) corresponding to the system side; a current measuring device is installed on the power line on the wind farm side (including but not limited to the collector line, the outlet of the step-up transformer, etc.) to collect the second current signal I B (t) corresponding to the wind farm side.

[0084] The acquisition module 100 includes: a calculation unit and a judgment unit; specifically, the calculation unit is configured to calculate the current difference between the third current signal corresponding to the system side and the wind farm side at the previous moment and the fourth current signal corresponding to the current moment; the judgment unit is configured to judge whether the current difference meets a preset condition, and if the preset condition is met, there is a line fault.

[0085] When the first current signal I A corresponding to the system side and the second current signal I B corresponding to the wind farm side are collected, it is necessary to calculate the current difference between the third current signal I A corresponding to the system side and the wind farm side at the previous moment and the fourth current signal I B corresponding to the current moment, that is, ΔI A =I A (t)-I A (t - 1); ΔI B =I B (t)-I B (t - 1), where ΔI A and ΔI B are the current differences of the first current signal on the system side and the second current difference on the wind farm side respectively, I A (t) and I A (t - 1) are the first current signal and the third current signal corresponding to the system side at time t and time t - 1 respectively, I B (t) and I B (t - 1) are the second current signal and the fourth current signal corresponding to the wind farm side at time t and time t - 1 respectively. Subsequently, it is judged whether the current difference ΔI A of the first current signal and the second current difference ΔI B meet the preset conditions, that is, whether they exceed the preset fault threshold. If the preset fault threshold is exceeded, it is considered that the corresponding current signal has a current mutation, and then it is determined that there is a line fault. If there is a line fault, the current signal needs to be further analyzed; if the preset fault threshold is not exceeded, there is no line fault, and the current signals at both ends of the system side and the wind farm side need to be continuously monitored. Among them, the schematic diagram of the current difference at both ends of the system side and the wind farm side is as Figure 3 shown.

[0086] In this way, by calculating the current mutation value, it is possible to judge whether the current signals corresponding to the system side and the wind farm side have current mutations, and then judge whether there are line faults on the corresponding sides, which can accurately judge whether there are line current faults on the system side and the wind farm side, and facilitate subsequent further analysis of the lines with line current faults to determine the corresponding outgoing line protection method.

[0087] The processing module 200 is configured to calculate the power spectra corresponding to both ends of the system side and the wind farm side respectively if there is a line fault, and obtain the current power difference between the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum.

[0088] The processing module 200 includes: a first processing unit, a second processing unit, and a third processing unit; specifically, the first processing unit is configured to respectively determine the covariance matrices corresponding to both ends of the system side and the wind farm side based on the current signal, where the covariance matrices include a first covariance matrix and a second covariance matrix; the second processing unit is configured to respectively perform eigenvalue decomposition on the covariance matrices to obtain the corresponding eigenvalues, and determine the corresponding noise matrices based on the eigenvalues, where the noise matrices include a first noise matrix and a second noise matrix; the third processing unit is configured to respectively obtain the power spectra corresponding to both ends of the system side and the wind farm side based on the noise matrices and a preset direction response vector, where the power spectra include a first power spectrum and a second power spectrum.

[0089] It can be understood that if there is a line fault, the current signals corresponding to both ends of the system side and the wind farm within the time window (i.e., the first current signal I A (t) and the second current signal I B (t)) are used to calculate the corresponding first power spectrum P A (f) and second power spectrum P B (f) by using the super-resolution power spectrum algorithm. Among them, the super-resolution power spectrum algorithm can be but is not limited to the music algorithm. The specific calculation process is as follows: First, the covariance matrices corresponding to both ends of the system side and the wind farm side are respectively determined based on the current signal, where the covariance matrices include a first covariance matrix R A and a second covariance matrix R B , and the calculation formulas of the covariance matrices are respectively: In the formula, R A is the first covariance matrix, n is the amount of data, I A = [I A (t1), I A (t2), …, I A (t n )] is the first current signal, H represents matrix transpose, R B is the second covariance matrix, I B = [I B (t1), I B (t2), …, I B (t n)] is the second current signal. Secondly, perform eigenvalue decomposition on the covariance matrix (i.e., the first covariance matrix R A and the second covariance matrix R B ) respectively to obtain the corresponding eigenvalues, and determine the corresponding noise matrices based on the eigenvalues. Among them, the eigenvalues include the first eigenvalue v i and the second eigenvalue e i . The relevant formula for eigenvalue decomposition of the covariance matrix is: R A = AR A A H + s 2 I, R B = BR B B H + s 2 I. In the formula, R A is the first covariance matrix, R B is the second covariance matrix, A and B are both signal basis matrices, H is the conjugate transpose operator of the matrix, s 2 is the intensity of the noise, I is the identity matrix, which is used to ensure the dimension adaptation of matrix operations; the calculation formula for the relevant decomposition results is: A H v i = 0, i = D + 1, D + 2,..., M, B H e i = 0, i = D + 1, D + 2,..., M. In the formula, v i is the first eigenvalue; D is the dimension of the signal subspace, representing the number of eigenvectors of the effective signal, satisfying D ≤ M; M is the dimension of the covariance matrix, representing the size of the signal vector; i is the index of the eigenvector, which is used to distinguish different eigenvectors. Then, based on the eigenvalues (i.e., the first eigenvalue v i and the second eigenvalue e i ), construct the corresponding noise matrices, that is, the first noise matrix E A and the second noise matrix E B . Among them, the expression of the noise matrix is: E A = [v D+1 , v D+2 ,... v M , E B = [e D+1 , e D+2 ,... e M . Finally, based on the noise matrix E and the preset direction response vector a, obtain the corresponding power spectra P(f) at both ends of the system side and the wind farm side. Among them, the power spectra include the first power spectrum P A (f) and the second power spectrum P B (f). The calculation formula for obtaining the corresponding power spectra at both ends of the system side and the wind farm side is specifically:

[0090]

[0091]

[0092] Wherein, P A (f) is the first power spectrum corresponding to the system side, P B (f) is the second power spectrum corresponding to the wind farm side, H is the transpose, f is the frequency, E A is the first noise matrix, E B is the second noise matrix, a(f) is the value of the direction response vector at frequency f, a is the direction response vector, and the expression is: a(f) = [1 e -jf …e -j(M-1)f , wherein, j is the imaginary unit.

[0093] In this way, by further analyzing the system side or the wind farm side where there is a line current fault, the corresponding power spectrum can be accurately calculated, which is convenient for subsequently obtaining the current power difference that accurately reflects the change of the fault current in the wind farm, and further convenient for subsequently effectively distinguishing between internal faults and external faults and accurately starting the corresponding transmission line protection method.

[0094] The processing module 200 further includes: an acquisition unit, a fourth processing unit, and a fifth processing unit; specifically, the acquisition unit is used to respectively acquire the power frequency and non-power frequency power corresponding to both the system side and the wind farm side; the fourth processing unit is used to respectively obtain the first frequency difference and the second frequency difference corresponding to both the system side and the wind farm side based on the power frequency and the non-power frequency power; the fifth processing unit is used to obtain the current power difference between the system side and the wind farm side based on the first frequency difference and the second frequency difference.

[0095] When the power spectra corresponding to the system side and the wind farm side (i.e., the first power spectrum P A (f) and the second power spectrum P B (f)) are obtained, the current power difference ΔP between the system side and the wind farm side can be obtained based on the power spectra. Specifically: First, the power frequency f 工 and the non-power frequency power corresponding to both the system side and the wind farm side are respectively acquired; Second, the first frequency difference ΔP 工 and the second frequency difference ΔP A corresponding to both the system side and the wind farm side are respectively obtained based on the power frequency f B and the non-power frequency power. The schematic diagram of the frequency difference between the system side and the wind farm side is as shown in Figure 4 , and the calculation formula is: Wherein, ΔPA is the first frequency difference corresponding to the system side, P A (f) is the first power spectrum, P B (f) is the second frequency difference corresponding to the wind farm side, P B (f) is the second power spectrum, f 工 is the industrial frequency. Finally, based on the first frequency difference ΔP A and the second frequency difference ΔP B , the current power difference ΔP between the system side and the wind farm side is obtained, that is, ΔP = ΔP A -ΔP B , where the schematic diagram of the current power difference between the system side and the wind farm side is as shown in Figure 5 shown.

[0096] In this way, by further analyzing the system side or the wind farm side with line current faults, calculating the corresponding power spectrum and current power difference, the current power difference that can accurately reflect the change of the fault current in the wind farm can be obtained, which is convenient for effectively distinguishing internal faults and external faults in the subsequent stage and accurately starting the corresponding transmission line protection method.

[0097] The protection module 300 is used to determine that the fault type is an internal fault of the transmission line and start the protection action of the transmission line if the current power difference exceeds a preset threshold.

[0098] It can be understood that after obtaining the current power difference ΔP between the system side and the wind farm side, it is necessary to determine whether the current power difference ΔP exceeds the preset threshold λ. If the current power difference ΔP exceeds the preset threshold λ, that is, ΔP > λ, it is determined that the fault type is an internal fault of the transmission line, and the protection action of the transmission line is started, that is, the circuit breakers at both ends of the transmission line act to cut off the transmission line from the system; if the current power difference ΔP does not exceed the preset threshold λ, that is, ΔP ≤ λ, it is determined that the fault type is an external fault of the transmission line, and the protection action is not started.

[0099] In the embodiments of the present application, by separately obtaining the current signals corresponding to both the system side and the wind farm side, and determining whether there is a line fault based on the current signals, it is possible to accurately determine whether there is a line current fault on the system side and the wind farm side, facilitating subsequent further analysis of the line with a line current fault to determine the corresponding outgoing line protection method; by further analyzing the system side or the wind farm side with a line current fault, calculating the corresponding power spectrum and the current power difference, a current power difference that accurately reflects the change of the fault current in the wind farm can be obtained, thereby facilitating subsequent effective discrimination between internal faults and external faults and accurately activating the corresponding outgoing line protection method; by determining whether the current power difference exceeds a preset threshold, internal faults and external faults can be effectively discriminated and the corresponding outgoing line protection method can be accurately activated. Compared with the prior art, the present application can adapt to the complex fault current characteristics of the wind farm and ensure the accuracy and reliability of the outgoing line protection method.

[0100] The device embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separated, that is, they may be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the method in this embodiment.

[0101] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the outgoing line protection method based on power spectrum analysis as described in the first embodiment above is implemented.

[0102] Those of ordinary skill in the art can understand that all or part of the processes of implementing the method in the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the above method embodiments. Among them, the storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0103] The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present application. It should be understood that the above are only specific embodiments of the present application and are not used to limit the protection scope of the present application.

[0104] It is particularly pointed out that for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A transmission line protection method based on power spectrum analysis, characterized in that, Including: Obtain the current signals corresponding to both ends of the system side and the wind farm side respectively, and determine whether there is a line fault based on the current signals, where the current signals include a first current signal and a second current signal; If there is a line fault, calculate the power spectra corresponding to both ends of the system side and the wind farm side respectively, and obtain the current power difference between both ends of the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum; If the current power difference exceeds a preset threshold, determine that the fault type is a fault within the outgoing line area, and initiate the protection action of the outgoing line.

2. The transmission line protection method based on power spectrum analysis according to claim 1, characterized in that, The determination of whether there is a line fault based on the current signals is specifically: Calculate the current difference between the third current signal corresponding to both ends of the system side and the wind farm side at the previous moment and the fourth current signal corresponding to the current moment; Judge whether the current difference meets a preset condition. If the preset condition is met, there is a line fault.

3. The transmission line protection method based on power spectrum analysis according to claim 1, characterized in that, The calculation of the power spectra corresponding to both ends of the system side and the wind farm side respectively is specifically: Based on the current signals, determine the covariance matrices corresponding to both ends of the system side and the wind farm side respectively, where the covariance matrices include a first covariance matrix and a second covariance matrix; Perform eigenvalue decomposition on the covariance matrices respectively to obtain the corresponding eigenvalues, and determine the corresponding noise matrices based on the eigenvalues, where the noise matrices include a first noise matrix and a second noise matrix; Based on the noise matrices and a preset direction response vector, obtain the power spectra corresponding to both ends of the system side and the wind farm side respectively, where the power spectra include a first power spectrum and a second power spectrum.

4. The transmission line protection method based on power spectrum analysis according to claim 3, wherein The calculation formula for obtaining the power spectra corresponding to both ends of the system side and the wind farm side is specifically: Wherein, P A (f) is the first power spectrum corresponding to the system side, P B (f) is the second power spectrum corresponding to the wind farm side, a is the direction response vector, H is the transpose, f is the frequency, E A is the first noise matrix, E B is the second noise matrix, and a(f) is the value of the direction response vector at the frequency f.

5. The transmission line protection method based on power spectrum analysis according to claim 1, characterized in that, The obtaining of the current power difference between both ends of the system side and the wind farm side based on the power spectra is specifically: Obtain the power frequency and non-power frequency power corresponding to both ends of the system side and the wind farm side respectively; Based on the power frequency and the non-power frequency power, obtain the first frequency difference and the second frequency difference corresponding to both ends of the system side and the wind farm side respectively; Based on the first frequency difference and the second frequency difference, obtain the current power difference between both ends of the system side and the wind farm side.

6. A transmission line protection device based on power spectrum analysis, characterized in that, Including: An acquisition module, a processing module, and a protection module; The acquisition module is used to obtain the current signals corresponding to both ends of the system side and the wind farm side respectively, and determine whether there is a line fault based on the current signals, where the current signals include a first current signal and a second current signal; The processing module is used to calculate the power spectra corresponding to both ends of the system side and the wind farm side respectively if there is a line fault, and obtain the current power difference between both ends of the system side and the wind farm side based on the power spectra, where the power spectra include a first power spectrum and a second power spectrum; The protection module is used to determine that the fault type is a fault within the outgoing line area if the current power difference exceeds a preset threshold, and initiate the protection action of the outgoing line.

7. The transmission line protection device based on power spectrum analysis according to claim 6, characterized in that, The acquisition module includes: a calculation unit and a judgment unit; The calculation unit is configured to calculate the current difference between the third current signal corresponding to the system side and the wind farm side at the previous moment and the fourth current signal corresponding to the current moment. The judgment unit is configured to judge whether the current difference meets a preset condition. If the preset condition is met, a line fault exists.

8. The transmission line protection device based on power spectrum analysis according to claim 6, characterized in that, The processing module includes: a first processing unit, a second processing unit, and a third processing unit. The first processing unit is configured to respectively determine covariance matrices corresponding to the system side and the wind farm side based on the current signal, where the covariance matrix includes a first covariance matrix and a second covariance matrix. The second processing unit is configured to respectively perform eigenvalue decomposition on the covariance matrix to obtain corresponding eigenvalues, and respectively determine corresponding noise matrices based on the eigenvalues, where the noise matrix includes a first noise matrix and a second noise matrix. The third processing unit is configured to respectively obtain power spectra corresponding to the system side and the wind farm side based on the noise matrix and a preset direction response vector, where the power spectrum includes a first power spectrum and a second power spectrum.

9. The outgoing line protection device based on power spectrum analysis according to claim 6, wherein The processing module further includes: an acquisition unit, a fourth processing unit, and a fifth processing unit. The acquisition unit is configured to respectively acquire the power frequency and the non-power frequency power corresponding to the system side and the wind farm side. The fourth processing unit is configured to respectively obtain a first frequency difference and a second frequency difference corresponding to the system side and the wind farm side based on the power frequency and the non-power frequency power. The fifth processing unit is configured to obtain the current power difference between the system side and the wind farm side based on the first frequency difference and the second frequency difference.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored computer program, wherein when the computer program runs, it controls the device where the computer-readable storage medium is located to execute a transmission line protection method based on power spectrum analysis according to any one of claims 1 to 5.

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