CN116973674A - Asymmetric fault section positioning method, device and system for new energy access power distribution network - Google Patents
Asymmetric fault section positioning method, device and system for new energy access power distribution network Download PDFInfo
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Abstract
A method, a device and a system for positioning an asymmetric fault section of a new energy access power distribution network, wherein the method comprises the following steps: forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and negative sequence component parameters of line loads under an offline condition, and extracting corresponding rows of measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix; calculating the negative sequence voltage of each sparse measurement point through FFT, and adding the negative sequence equivalent impedance into the sensing matrix to modify the sensing matrix in real time; solving the negative sequence injection current of all virtual nodes by using the perception matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point; and regarding the nodes corresponding to the first two maximum values in the negative sequence injection current as the nodes at the two ends of the fault section, thereby realizing the positioning of the fault section. When the asymmetric fault occurs in the power distribution network containing the distributed new energy access, the fault section positioning can be realized by only needing a small amount of measurement point voltage data, and the influence of the fault grounding resistance and the measurement noise is small.
Description
Technical Field
The invention relates to the technical field of power system analysis, in particular to a method, a device and a system for positioning an asymmetric fault section of a new energy access power distribution network.
Background
The distribution network with distributed new energy access has the characteristics of complex topological structure, numerous branches, small power supply radius, hybrid connection of overhead lines and cable lines and the like, and if a permanent fault occurs, the fault cannot be rapidly and accurately positioned, the recovery time of the system is prolonged, and the power supply quality is affected. The impedance method, the traveling wave method, the S signal injection method and the like are mature to be applied to fault location of a power transmission network, accurate location of fault positions on long-distance power transmission lines can be achieved, and the method is not suitable for power distribution networks with relatively complex topologies, so that research on fault location methods based on wide-area measurement data is of great significance.
Fault location methods based on wide area measurement data, i.e. determining a fault section by analyzing electrical measurements collected by intelligent electrical devices (Intelligent Electric Device, IEDs) installed at multiple locations in the power grid at the time of a fault. Currently, studies on positioning methods based on wide area measurement data are mainly classified into three categories: positioning methods using fault indicators, positioning methods based on voltage sags and positioning methods by means of intelligent algorithms. The positioning method using the fault indicator is simple in principle and easy to implement, but the positioning area range is large, the exact fault line cannot be pointed out, and the fault detection time is still long; the positioning method based on the voltage sag is characterized in that the voltage sag data of each node before and after the fault is compared with the voltage data obtained by simulation in advance, the best matching fault condition is found to realize positioning, but the actual fault types are various and the transition resistances are different, all conditions cannot be considered in advance, and the positioning method is not general; existing positioning methods with intelligent algorithms require a large amount of data to pre-train, and require a large amount of recalculation once the load situation changes.
To sum up, the existing fault locating methods all require a large amount of measuring points or data to achieve fault section location, and are not suitable for asymmetric faults. Therefore, research on a method for positioning an asymmetric fault section of the new energy access power distribution network is necessary, and technical support is provided for rapid troubleshooting of engineering.
Disclosure of Invention
In order to solve the problems, the invention provides a method, a device and a system for positioning an asymmetric fault section of a new energy access power distribution network.
The technical scheme adopted by the invention is as follows:
the asymmetric fault section positioning method for the new energy access distribution network is characterized by comprising the following steps of:
forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of line loads under an offline condition, and extracting corresponding rows of measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix;
taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculating negative sequence voltage of each sparse measurement point through FFT, and adding negative sequence equivalent impedance into a position corresponding to a new energy access node in the sensing matrix to modify the sensing matrix in real time;
forming an underdetermined equation set by using the sensing matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements in the underdetermined equation set, and solving the negative sequence injection current of all virtual nodes by using a matching pursuit algorithm;
and regarding the nodes corresponding to the first two maximum values in the negative sequence injection current of all the virtual nodes as nodes at two ends of the fault section, thereby realizing the positioning of the fault section.
Further, forming a negative sequence node impedance matrix according to a topological structure of the power distribution network and a negative sequence component parameter of line load under the offline condition, and extracting a corresponding row of a measuring node in the negative sequence node impedance matrix to generate a sensing matrix, which specifically comprises the following steps:
for a power distribution network with n nodes, a negative sequence node impedance array Z is formed by a topological structure and parameters n×n ：
The diagonal line elements are negative sequence impedance of all lines and loads connected at the corresponding nodes, and the non-diagonal line elements are negative values of the negative sequence impedance of the lines between the two nodes corresponding to the corner mark numbers;
selecting M nodes in all nodes to install measuring equipment, wherein M is less than n, and arranging a node negative sequence impedance array Z n×n Corresponding rows of the matrix are extracted to form a sensing matrix Z M ：
Further, taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, and calculating negative sequence voltages of each sparse measurement point through FFT, wherein the method specifically comprises the following steps: and calculating fundamental power frequency voltage amplitude of the sparse measuring point through FFT, and calculating and extracting negative sequence voltage of the sparse measuring point through a symmetrical component method.
Further, the fundamental power frequency voltage amplitude of the sparse measuring point is calculated through FFT, and the calculation formula is as follows:
wherein ,the fundamental voltage component obtained by FFT calculation, M is the number of data points for Fourier decomposition, v (n) is the measured discrete voltage data, and j is an imaginary unit;
the negative sequence voltage of the sparse measuring point is extracted by a symmetrical component method, and the calculation formula is as follows:
wherein ,for negative sequence voltage, a is a phase shift operator, multiplying the phasor by the phasor means advancing the phase of the phasor by 120 DEG, the square a 2 Multiplication with the phasor means that the phasor is phase advanced by 240 °,/for example>For A phase voltage>For B phase voltage, ">Is the C phase voltage;
the negative sequence equivalent impedance is calculated by dividing the voltage at the outlet of the distributed new energy source by the output current of the distributed new energy source, and the calculation formula is as follows:
wherein ,ZdRES2 Is distributed new energy negative sequence equivalent impedance,is the negative sequence voltage at the outlet of the distributed new energy source, < > or->And outputting negative sequence current for the distributed new energy.
Further, the set of under-determined equations is as follows:
U M ＝Z M ·I(6)
wherein ,UM And (3) calculating the amplitude values of all elements in the above formula for the M-dimension point negative sequence voltage vector and the I virtual n-dimension node negative sequence current injection vector.
Further, the solving the negative sequence injection current of all the virtual nodes by using the matching pursuit algorithm specifically includes: and taking the voltage measured value as the weighted summation of all column vectors of the sensing matrix, and determining the weight of each base vector to solve the true solution when searching the current solution vector, so as to find the node negative sequence injection current vector I.
An asymmetric fault section positioning device for new energy access to a power distribution network, comprising:
the sensing matrix generation module is used for forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of the line load under the off-line condition, and extracting corresponding rows of the measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix;
the negative sequence voltage calculation and sensing matrix modification module is used for taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculating the negative sequence voltage of each sparse measurement point through FFT, and adding negative sequence equivalent impedance into a position corresponding to a new energy access node in the sensing matrix so as to modify the sensing matrix in real time;
the negative sequence injection current calculation module is used for forming an underdetermined equation set by utilizing the perception matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements in the underdetermined equation set, and solving the negative sequence injection current of all virtual nodes by utilizing a matching pursuit algorithm;
and the fault section positioning and positioning module is used for taking the nodes corresponding to the first two maximum values in the negative sequence injection current of all the virtual nodes as the nodes at the two ends of the fault section, so that the fault section positioning is realized.
Further, the sensing matrix generation module is specifically configured to:
for a power distribution network with n nodes, a negative sequence node impedance array Z is formed by a topological structure and parameters n×n ：
The diagonal line elements are negative sequence impedance of all lines and loads connected at the corresponding nodes, and the non-diagonal line elements are negative values of the negative sequence impedance of the lines between the two nodes corresponding to the corner mark numbers;
selecting M nodes in all nodes to install measuring equipment, wherein M is less than n, and arranging a node negative sequence impedance array Z n×n Corresponding rows of the matrix are extracted to form a sensing matrix Z M ：
Further, the negative sequence voltage calculating and sensing matrix modifying module takes three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculates the negative sequence voltage of each sparse measurement point through FFT, and specifically comprises the following steps: and calculating fundamental power frequency voltage amplitude of the sparse measuring point through FFT, and calculating and extracting negative sequence voltage of the sparse measuring point through a symmetrical component method.
Further, the fundamental power frequency voltage amplitude of the sparse measuring point is calculated through FFT, and the calculation formula is as follows:
wherein ,the fundamental voltage component obtained by FFT calculation, M is the number of data points for Fourier decomposition, v (n) is the measured discrete voltage data, and j is an imaginary unit;
the negative sequence voltage of the sparse measuring point is extracted by a symmetrical component method, and the calculation formula is as follows:
wherein ,for negative sequence voltage, a is a phase shift operator, multiplying the phasor by the phasor means advancing the phase of the phasor by 120 DEG, the square a 2 Multiplication with the phasor means that the phasor is phase advanced by 240 °,/for example>For A phase voltage>For B phase voltage, ">Is the C phase voltage;
the negative sequence equivalent impedance is calculated by dividing the voltage at the outlet of the distributed new energy source by the output current of the distributed new energy source, and the calculation formula is as follows:
wherein ,ZdRES2 Is distributed new energy negative sequence equivalent impedance,is the negative sequence voltage at the outlet of the distributed new energy source, < > or->And outputting negative sequence current for the distributed new energy.
Further, the set of under-determined equations is as follows:
U M ＝Z M ·I(6)
wherein ,UM And (3) calculating the amplitude values of all elements in the above formula for the M-dimension point negative sequence voltage vector and the I virtual n-dimension node negative sequence current injection vector.
Further, the negative sequence injection current calculation module solves the negative sequence injection current of all the virtual nodes by using a matching pursuit algorithm, and specifically includes: and taking the voltage measured value as the weighted summation of all column vectors of the sensing matrix, and determining the weight of each base vector to solve the true solution when searching the current solution vector, so as to find the node negative sequence injection current vector I.
An asymmetric fault section positioning system for new energy access to a power distribution network, comprising: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is used for reading executable instructions stored in the computer readable storage medium and executing the asymmetric fault section positioning method for accessing the new energy into the power distribution network.
The invention has the following beneficial effects:
when an asymmetric fault occurs in the power distribution network containing distributed new energy access, the fault section can be positioned only by a small amount of measurement point voltage data, and the influence of the fault grounding resistance and measurement noise is small; in addition, the invention can be realized based on the current IEC 61850 standard, has lower requirement on channels and is compatible with the existing distribution network communication system.
Drawings
FIG. 1 is a flow chart of a method for locating an asymmetrical fault section of a new energy access power distribution network according to the present invention;
FIG. 2 is a topology diagram of a 69 node power distribution network at a certain 10kV voltage level;
FIG. 3 is a schematic diagram of virtual negative sequence current equivalence of nodes at two ends of a fault region;
FIG. 4 is a block diagram of an algorithm flow of the fault locating method according to the present invention;
FIG. 5 is a schematic representation of the virtual current reconstruction result threshold setting;
FIG. 6 is a plot of the results of a fault on lines 43-44 that occurred in the AC two phase via 10Ω ground resistance;
FIG. 7 is a graph showing the results of a positioning of a BC two-phase through 25Ω ground resistance fault on lines 17-18 under 40dB noise condition;
fig. 8 is a graph showing the results of locating phase a ground faults through 15 Ω resistor after random changes in line parameters in lines 32-33.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Fig. 1 is a flowchart of a method for locating an asymmetric fault section of a new energy access power distribution network according to an embodiment of the present invention, including the following steps:
step (1): forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of line loads under an offline condition, and extracting corresponding rows of measuring nodes in the negative sequence node impedance matrix to generate a perception matrix; the method specifically comprises the following steps: the method for forming the negative sequence node impedance matrix can refer to the formation of a general node impedance matrix, namely diagonal elements are negative sequence impedance of all lines and loads connected at corresponding nodes, and non-diagonal elements are negative values of negative sequence impedance of the lines between two nodes corresponding to corner mark numbers;
for a power distribution network with n nodes, a negative sequence node impedance array Z is formed by a topological structure and parameters n×n ：
Because the matching pursuit algorithm cited in the invention can realize the effect of reconstructing virtual negative sequence current by using the measurement data of few measuring points, only M (M < n) nodes in all nodes are selected to install measurement equipment, and the node negative sequence impedance array Z n×n Corresponding rows of the matrix are extracted to form a sensing matrix Z M ：
Step (2): three-phase voltage data of each sparse measurement point with a certain window length in a fault steady state are taken, fundamental power frequency voltage amplitude values of each sparse measurement point are calculated through FFT, then negative sequence voltage of the sparse measurement point is extracted through a symmetrical component method, negative sequence equivalent impedance is calculated by dividing voltage at a distributed new energy outlet by output current of the voltage, and the negative sequence equivalent impedance is added to a position corresponding to a new energy access node in the sensing matrix so as to modify the sensing matrix in real time;
the calculation formula for calculating the fundamental voltage of the sparse measuring point through FFT is as follows:
wherein ,the fundamental voltage component obtained by FFT calculation, M is the number of data points for Fourier decomposition, v (n) is the measured discrete voltage data, and j is an imaginary unit;
the calculation formula for extracting the negative sequence voltage of the sparse measurement point by the symmetrical component method is as follows:
wherein ,as a negative sequence voltage, a=e jω120° ，/>For A phase voltage>For B phase voltage, ">Is the C phase voltage;
the calculation formula for calculating the negative sequence equivalent impedance by dividing the voltage at the outlet of the distributed new energy source by the output current of the distributed new energy source is as follows:
wherein ,ZdRES2 Is distributed new energy negative sequence equivalent impedance,is the negative sequence voltage at the outlet of the distributed new energy source, < > or->Outputting negative sequence current for the distributed new energy;
and adding the negative sequence equivalent impedance of each distributed new energy into the corresponding position of the new energy access node in the sensing matrix so as to modify the sensing matrix in real time.
Step (3): forming a underdetermined equation set by using the perception matrix obtained in the steps (1) and (2) and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements, and solving the negative sequence injection current of all virtual nodes by using a matching pursuit algorithm;
wherein the set of under-determined equations is as follows:
U M ＝Z M ·I (6)
wherein ,UM And (3) calculating the amplitude values of all elements in the above formula for the M-dimension point negative sequence voltage vector and the I virtual n-dimension node negative sequence current injection vector.
In order to explain that the processing mode does not affect the fault location result, the following is a brief description of the principle:
impedance matrix at node Z n×n The elements associated with nodes l and m satisfy the following relationship:
in the formula ,k1 ≠k 2 And i is the upstream node of the area between the nodes l and m, and j is the downstream node of the area between the nodes l and m.
Thus, although there are n equations in the node voltage equation after the fault, a large number of redundant equations are actually contained in the node voltage equation, and the node voltage equation essentially consists of the following two equations only:
after taking the absolute value, the above formula can be written as:
for the above system of equations, if the number of equations is equal to the number of unknowns, then it is certainly possibleTo solve to I l * and Im * Therefore, the equation set U=ZI can be solved only by the fact that the upstream and downstream of the area between the nodes l and m are provided with measuring points, and U is U for taking the amplitude value M Z is the Z of the amplitude M I is a virtually reconstructed negative sequence current vector. The best configuration in practice is to install voltage measurement devices at the head end and each end node of the distribution network.
The matching pursuit algorithm in the step (3) has accurate reconstruction capability for sparse target vectors, and the sparse measurement point negative sequence voltage (M-dimensional data) obtained in the step (2) can be regarded as virtual node negative sequence current (n-dimensional data, M < n) passing through a sensing matrix Z in combination with the matching pursuit algorithm M Mapping the obtained. According to the matching pursuit algorithm, the voltage measurement value is regarded as the weighted summation of all column vectors of the perception matrix, and when the current solution vector is searched, the real solution of the current solution vector can be solved by determining the weight of all base vectors, and the sufficiently sparse negative sequence current vector I is found.
Step (4): and (3) injecting current according to the reconstructed virtual negative sequence in the step (3), and regarding the nodes corresponding to the first two maximum values as the nodes at the two ends of the fault section, thereby realizing the positioning of the fault section.
In the step (4), the reconstruction result of the node negative sequence current vector obtained in the step (3) does not always contain only two non-zero elements, so that according to simple numerical comparison, the nodes corresponding to the two maximum value elements are determined to be the nodes at the two ends of the line where the fault is located, and the fault section can be obtained. If the obtained node is an adjacent node, the line between the nodes fails; if not, the areas in between are regarded as fault areas.
Fig. 2 is a topology diagram of a 69-node power distribution network with a certain 10kV voltage level, and distributed new energy sources are respectively connected to the nodes 1, 26, 34, 53, 55 and 57. And voltage measuring means are arranged on nodes 1, 26, 34, 38, 40, 53, 55, 57 and 68.
Fig. 3 is an equivalent schematic diagram of virtual negative sequence current at two nodes of a fault area, when an asymmetric fault occurs in the distribution network, the fault point can be regarded as a negative sequence current source, and the negative sequence current source can be equivalent to the virtual negative sequence current source at two nodes of the fault area, and the two virtual current sources affect the negative sequence voltage of the node through the joint action of the node impedance matrix. Therefore, the negative sequence voltage of each node can be obtained by multiplying the node impedance matrix and the node virtual negative sequence injection current vector, and then the row corresponding to the voltage measuring point is extracted to form a new equation set:
in the formula ,Il 、I m The virtual negative sequence current of the nodes at two ends of the fault area is represented, and the influence of the virtual negative sequence current on the negative sequence voltage is the same as that brought by the actual negative sequence current.
The node impedance matrix contains characteristics that the amplitude value of the known elements of the equation set does not affect positioning. Therefore, the elements of the equation are taken to obtain U=Z.I, U is the negative sequence voltage amplitude vector of the M-dimensional measuring point, Z is the M×n-dimensional sensing matrix, and I is the negative sequence current vector of the n-dimensional virtual node to be solved, and the method is specifically as follows:
the above equation is a system of underdetermined equations, there are infinite sets of solutions, and the matching pursuit theory can obtain a sufficiently sparse solution, i.e., the required vector I, from the infinite sets of solutions. The matching tracking technology has accurate reconstruction capability for the sufficiently sparse target vector, so the equation can be solved by the matching tracking technology, and the purpose of fault region positioning is realized by utilizing the reconstruction current vector I, namely, the region between the nodes corresponding to the non-zero elements is faulty.
Fig. 4 is a fault locating flow chart provided by the invention, and the locating steps after faults occur in the power distribution network are as follows:
1) Before a fault occurs, obtaining a negative sequence node impedance matrix offline from a topological structure of the power distribution network and line load parameters, and obtaining a perception matrix Z from the distribution condition of the IED;
2) After the fault occurs, a fault positioning program is started, and three-phase voltage data acquired by the IED are calculated to obtain a measuring point negative sequence voltage U through FFT and a symmetrical component method;
3) Substituting the sensing matrix Z and the measuring point negative sequence voltage U into a BCS algorithm to reconstruct a virtual node negative sequence current I;
4) The data window is slid until the data within the entire acquired sample has been processed.
Experiments are carried out by using the power distribution network shown in fig. 2, 2 fault points are arranged on each wiring, 134 fault positions are provided, and positioning performances under the conditions of different fault types and different transition resistances are considered, wherein positioning results are shown in table 1. The results in table 1 show that in the absence of noise, about 90% of the fault points can be precisely located to the actual fault zone; the remaining about 10% of the fault points are located in adjacent lines, and the locating performance of the method is very good.
TABLE 1
Considering the effect of noise on the method, the positioning results of the positioning case under 40dB of gaussian white noise condition are shown in table 2. The statistical result shows that the positioning result under the condition is still accurate, and the method has certain noise resistance.
TABLE 2
Fig. 5 shows a case of setting a threshold value of a reconstruction result of a virtual current, in which the virtual node negative sequence current injection obtained by reconstruction in an actual application is not strictly zero at a non-fault node position, but is displayed as a smaller non-zero value, in this case, a threshold value needs to be set to distinguish the reconstruction values corresponding to the nodes at two ends of a fault section and the rest of the nodes, through a large number of experiments, the threshold value is set to be the ratio of the second largest reconstruction value to the maximum value (i.e., the third largest value) in the rest of the reconstruction values, and the threshold value is set to 4.163, i.e., the reconstruction value with the ratio greater than the value is set as an effective positioning result.
Fig. 6 shows the result of locating the fault of the AC two-phase ground resistor of 10Ω on the lines 43-44, and can intuitively determine that the fault has occurred on the lines 43-44.
Fig. 7 shows the result of locating the fault of the AC two-phase through 25Ω ground resistance on the line 17-18 under the 40dB noise condition, and it can be intuitively judged that the fault has occurred on the line 17-18.
Fig. 8 shows the determination of the occurrence of a phase a ground fault through a 15 Ω resistor on the line 32-33 after the change of the line parameters, and the visual determination of the occurrence of a fault on the line 32-33 can be made from the graph, so that the positioning section is accurate. The way to randomly change the line parameters is: the resistance and inductance of each line are respectively adjusted to 0.95 to 1.05 times of the original value. The result shows that: only a small number of fault points can be positioned in adjacent areas, so that the fault positioning method has certain fault tolerance.
The embodiment of the invention also provides an asymmetric fault section positioning device of the energy access distribution network, which comprises the following steps:
the sensing matrix generation module is used for forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of the line load under the off-line condition, and extracting corresponding rows of the measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix;
the negative sequence voltage calculation and sensing matrix modification module is used for taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculating the negative sequence voltage of each sparse measurement point through FFT, and adding negative sequence equivalent impedance into a position corresponding to a new energy access node in the sensing matrix so as to modify the sensing matrix in real time;
the negative sequence injection current calculation module is used for forming an underdetermined equation set by utilizing the perception matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements in the underdetermined equation set, and solving the negative sequence injection current of all virtual nodes by utilizing a matching pursuit algorithm;
and the fault section positioning and positioning module is used for taking the nodes corresponding to the first two maximum values in the negative sequence injection current of all the virtual nodes as the nodes at the two ends of the fault section, so that the fault section positioning is realized.
Another embodiment of the present invention provides an asymmetric fault section positioning system for accessing new energy into a power distribution network, including: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is configured to read executable instructions stored in the computer readable storage medium, and execute the asymmetric fault section positioning method for accessing new energy into the power distribution network according to the first aspect.
Another embodiment of the present invention provides a non-transitory computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method for positioning an asymmetric fault section of a new energy access distribution network according to the first aspect.
It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical aspects of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the above embodiments, it should be understood by those of ordinary skill in the art that: modifications and equivalents may be made to the specific embodiments of the invention without departing from the spirit and scope of the invention, which is intended to be covered by the claims.
Claims (13)
1. The asymmetric fault section positioning method for the new energy access distribution network is characterized by comprising the following steps of:
forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of line loads under an offline condition, and extracting corresponding rows of measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix;
taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculating negative sequence voltage of each sparse measurement point through FFT, and adding negative sequence equivalent impedance into a position corresponding to a new energy access node in the sensing matrix to modify the sensing matrix in real time;
forming an underdetermined equation set by using the sensing matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements in the underdetermined equation set, and solving the negative sequence injection current of all virtual nodes by using a matching pursuit algorithm;
and regarding the nodes corresponding to the first two maximum values in the negative sequence injection current of all the virtual nodes as nodes at two ends of the fault section, thereby realizing the positioning of the fault section.
2. The method for positioning an asymmetric fault section of a new energy access power distribution network according to claim 1, wherein the forming a negative sequence node impedance matrix according to a topology structure of the power distribution network and a negative sequence component parameter of a line load under the offline condition, and extracting a corresponding row of measurement nodes in the negative sequence node impedance matrix to generate a sensing matrix specifically comprises:
for a power distribution network with n nodes, a negative sequence node impedance array Z is formed by a topological structure and parameters n×n ：
The diagonal line elements are negative sequence impedance of all lines and loads connected at the corresponding nodes, and the non-diagonal line elements are negative values of the negative sequence impedance of the lines between the two nodes corresponding to the corner mark numbers;
selecting M nodes in all nodes to install measuring equipment, wherein M is less than n, and arranging a node negative sequence impedance array Z n×n Corresponding rows of the matrix are extracted to form a sensing matrix Z M ：
3. The method for positioning an asymmetric fault section of a new energy access power distribution network according to claim 1, wherein the method is characterized in that three-phase voltages of each sparse measurement point with a certain window length in a fault steady state are taken, and negative sequence voltages of each sparse measurement point are calculated through FFT, and specifically comprises the following steps: and calculating fundamental power frequency voltage amplitude of the sparse measuring point through FFT, and calculating and extracting negative sequence voltage of the sparse measuring point through a symmetrical component method.
4. The method for locating an asymmetrical fault section of a new energy access power distribution network according to claim 3, wherein the fundamental power frequency voltage amplitude of the sparse measurement point is calculated by FFT, and the calculation formula is as follows:
wherein ,the fundamental voltage component obtained by FFT calculation, M is the number of data points for Fourier decomposition, v (n) is the measured discrete voltage data, and j is an imaginary unit;
the negative sequence voltage of the sparse measuring point is extracted by a symmetrical component method, and the calculation formula is as follows:
wherein ,for negative sequence voltage, a is a phase shift operator, multiplying the phasor by the phasor means advancing the phase of the phasor by 120 DEG, the square a 2 Multiplication with the phasor means that the phasor is phase advanced by 240 °,/for example>For A phase voltage>For B phase voltage, ">Is the C phase voltage;
the negative sequence equivalent impedance is calculated by dividing the voltage at the outlet of the distributed new energy source by the output current of the distributed new energy source, and the calculation formula is as follows:
wherein ,ZdRES2 Is distributed new energy negative sequence equivalent impedance,is the negative sequence voltage at the outlet of the distributed new energy source,and outputting negative sequence current for the distributed new energy.
5. The method for locating an asymmetrical fault section of a new energy access power distribution network according to claim 1, wherein the set of underdetermined equations is as follows:
U M ＝Z M ·I(6)
wherein ,UM And (3) calculating the amplitude values of all elements in the above formula for the M-dimension point negative sequence voltage vector and the I virtual n-dimension node negative sequence current injection vector.
6. The method for locating an asymmetrical fault section of a new energy access power distribution network according to claim 1, wherein the method for solving the negative sequence injection current of all virtual nodes by using a matching pursuit algorithm comprises the following steps: and taking the voltage measured value as the weighted summation of all column vectors of the sensing matrix, and determining the weight of each base vector to solve the true solution when searching the current solution vector, so as to find the node negative sequence injection current vector I.
7. An asymmetric fault section positioning device for new energy access to a power distribution network, which is characterized by comprising:
the sensing matrix generation module is used for forming a negative sequence node impedance matrix according to the topological structure of the power distribution network and the negative sequence component parameters of the line load under the off-line condition, and extracting corresponding rows of the measuring nodes in the negative sequence node impedance matrix to generate a sensing matrix;
the negative sequence voltage calculation and sensing matrix modification module is used for taking three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculating the negative sequence voltage of each sparse measurement point through FFT, and adding negative sequence equivalent impedance into a position corresponding to a new energy access node in the sensing matrix so as to modify the sensing matrix in real time;
the negative sequence injection current calculation module is used for forming an underdetermined equation set by utilizing the perception matrix added with the negative sequence equivalent impedance and the negative sequence voltage of the sparse measurement point, taking the absolute values of all known elements in the underdetermined equation set, and solving the negative sequence injection current of all virtual nodes by utilizing a matching pursuit algorithm;
and the fault section positioning and positioning module is used for taking the nodes corresponding to the first two maximum values in the negative sequence injection current of all the virtual nodes as the nodes at the two ends of the fault section, so that the fault section positioning is realized.
8. The asymmetric fault section positioning device of a new energy access distribution network according to claim 7, wherein the sensing matrix generation module is specifically configured to:
for a power distribution network with n nodes, a negative sequence node impedance array Z is formed by a topological structure and parameters n×n ：
The diagonal line elements are negative sequence impedance of all lines and loads connected at the corresponding nodes, and the non-diagonal line elements are negative values of the negative sequence impedance of the lines between the two nodes corresponding to the corner mark numbers;
selecting M nodes in all nodes to install measuring equipment, wherein M is less than n, and arranging a node negative sequence impedance array Z n×n Corresponding rows of the matrix are extracted to form a sensing matrix Z M ：
9. The asymmetric fault section positioning device for accessing new energy into a power distribution network according to claim 7, wherein the negative sequence voltage calculating and sensing matrix modifying module takes three-phase voltages of each sparse measurement point with a certain window length in a fault steady state, calculates the negative sequence voltage of each sparse measurement point through FFT, and specifically comprises: and calculating fundamental power frequency voltage amplitude of the sparse measuring point through FFT, and calculating and extracting negative sequence voltage of the sparse measuring point through a symmetrical component method.
10. The asymmetric fault section positioning device for new energy access to a power distribution network according to claim 9, wherein the fundamental wave power frequency voltage amplitude of the sparse measurement point is calculated through FFT, and the calculation formula is as follows:
wherein ,the fundamental voltage component obtained by FFT calculation, M is the number of data points for Fourier decomposition, v (n) is the measured discrete voltage data, and j is an imaginary unit;
the negative sequence voltage of the sparse measuring point is extracted by a symmetrical component method, and the calculation formula is as follows:
wherein ,for negative sequence voltage, a is a phase shift operator, multiplying the phasor by the phasor means advancing the phase of the phasor by 120 DEG, the square a 2 Multiplication with the phasor means that the phasor is phase advanced by 240 °,/for example>For A phase voltage>For B phase voltage, ">Is the C phase voltage;
the negative sequence equivalent impedance is calculated by dividing the voltage at the outlet of the distributed new energy source by the output current of the distributed new energy source, and the calculation formula is as follows:
wherein ,ZdRES2 Is distributed new energy negative sequence equivalent impedance,is the negative sequence voltage at the outlet of the distributed new energy source,and outputting negative sequence current for the distributed new energy.
11. The asymmetric fault section locating device for a new energy access distribution network according to claim 7, wherein the set of underdetermined equations is as follows:
U M ＝Z M ·I(6)
wherein ,UM And (3) calculating the amplitude values of all elements in the above formula for the M-dimension point negative sequence voltage vector and the I virtual n-dimension node negative sequence current injection vector.
12. The asymmetric fault section positioning device of a new energy access power distribution network according to claim 7, wherein the negative sequence injection current calculation module solves a negative sequence injection current of all virtual nodes by using a matching pursuit algorithm, and specifically comprises: and taking the voltage measured value as the weighted summation of all column vectors of the sensing matrix, and determining the weight of each base vector to solve the true solution when searching the current solution vector, so as to find the node negative sequence injection current vector I.
13. An asymmetric fault section positioning system for new energy access to a power distribution network, comprising: a computer readable storage medium and a processor;
the computer-readable storage medium is for storing executable instructions;
the processor is configured to read executable instructions stored in the computer readable storage medium and execute the asymmetric fault section locating method for accessing new energy into the power distribution network according to any one of claims 1 to 6.
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