A limited information distribution network fault locating method based on voltage deviation calculation

Abstract

The application discloses a limited information distribution network fault positioning method based on voltage calculation deviation, mainly comprising the following steps: firstly, constructing a node impedance matrix according to the structure and parameters of a distribution network; judging whether a short-circuit fault occurs in the distribution network according to a distribution network node monitoring system based on a small number of monitoring points; when the fault occurs, solving a node current equation through a basis pursuit algorithm according to a small number of measured point data obtained by the monitoring system, and judging a fault interval according to an observed reconstructed node current vector; then, a fault positioning method based on the relationship between a calculated value and a measured value of a downstream node voltage of a fault interval is proposed according to the relationship between the calculated value and the measured value of the downstream node voltage of the fault interval, preliminary fault positioning is realized, the full node voltage value of the system after the fault is back calculated according to the reconstructed node current vector, the fault position is further positioned by using the calculated deviation of the downstream node voltage of the fault interval, and finally, the distribution network fault positioning is realized by combining the measured information and the reconstructed information.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power system relay protection, and particularly relates to a limited information distribution network fault location method based on voltage calculation deviation. BACKGROUND

[0002] Quick and accurate fault section location of distribution network is the premise of timely isolating fault area and restoring power supply in non-fault area, and is of great significance to improving system reliability. According to statistics, more than 80% of power grid faults occur in distribution network. With a large number of distributed power sources connected to the distribution network, the distribution network becomes a source network with bidirectional flow of normal operating power and fault current, which makes fault section location complicated, and the traditional positioning algorithm is no longer applicable. At the same time, the traditional fault location method needs to meet the strict synchronization and high sampling frequency of data, and the device meeting the two conditions is expensive, which makes it difficult for many fault location methods to be used in practice. Therefore, it is an urgent technical problem to study a new fault section location technology of distribution network that meets accuracy. SUMMARY

[0003] In order to solve the technical problems in the background art, the present application provides a limited information distribution network fault location method based on voltage calculation deviation. The full node information can be obtained by basis pursuit compressed sensing algorithm according to the data information measured by a small number of measuring devices in the distribution network, so as to accurately perform fault ranging according to voltage calculation deviation.

[0004] In order to achieve the above technical purpose, the technical scheme of the present application is as follows:

[0005] A limited information distribution network fault location method based on voltage calculation deviation, comprising the following steps: (1) collecting the topological structure and related parameters of the distribution network, and constructing a node impedance matrix of the distribution network;

[0006] (2) constructing a node monitoring system of the distribution network based on a small number of monitoring points, and monitoring the voltage and current signals of a small number of nodes of the distribution network in real time;

[0007] (3) judging whether the distribution network has a fault or not by monitoring the line voltage of the monitoring node;

[0008] (4) when the distribution network has a fault, calculating the positive sequence line voltage change value of each monitoring node;

[0009] (5) reconstructing the node current vector and the node current value by using the basis pursuit compressed sensing algorithm, and judging the fault section according to the reconstructed node current vector;

[0010] (6) using the original monitoring point data of the downstream nodes of the monitoring point in the fault section to obtain the fault position by the voltage calculation deviation method;

[0011] (7) The fault post full node voltage value of the system is obtained by back propagation using the reconstructed node current vector;

[0012] (8) The fault location of the reconstructed information is obtained by calculating the voltage calculation deviation of the downstream node in the fault interval;

[0013] (9) The measured point information and the reconstructed information in steps (6) and (8) are combined;

[0014] (10) The accurate fault location is performed.

[0015] Optionally, in step (4), when the power distribution network fails, the measured point fault voltage and the measured point fault current are obtained when the system fails, the positive sequence voltage data of the system fault steady state period and the normal operation period are used to obtain the corresponding node positive sequence line voltage change amount modulus , wherein the positive sequence voltage change amount modulus of the jth node is calculated as follows:

[0016] ;

[0017] In the formula, is the positive sequence measured voltage before the failure of the jth node, is the positive sequence measured voltage after the failure of the jth node.

[0018] Optionally, in step (5), the underdetermined node injection fault current equation is constructed, the compressed sensing algorithm based on basis pursuit is used for calculation, and the reconstructed node current vector and the node current calculation value I are obtained.

[0019] ;

[0020] In the formula, is the reconstructed node current vector, is the node impedance matrix of the normal operation of the power distribution network, is the positive sequence fault voltage change amount.

[0021] The reconstructed node current vector is observed to determine the fault interval.

[0022] ;

[0023] is an n x 1 matrix, wherein the non-zero elements , occupy the order i and j, which are the fault interval nodes, and thus the fault interval is i-j.

[0024] Optionally, step (6) first calculates the voltage calculation deviation of the downstream measuring point of the measuring point interval where the fault interval is located using the original measuring point data, and the smaller the voltage calculation deviation is, the closer the corresponding position is to the fault point; the voltage calculation deviation of the downstream node of the measuring point interval is as follows:

[0025]

[0026] wherein, , is a natural number from 1 to ; is the ratio of the length of the measuring device interval where the fault interval is located to the required accuracy; is the voltage calculation deviation of the downstream node q of the nearest measuring device interval on both sides of the fault interval p-q, , are the measured voltages of node q before and after the fault, is the line impedance between node p and the fault point f, , is the element value of the node impedance matrix between node p and node q when the system is normally running.

[0027] Optionally, step (8) calculates the voltage calculation deviation of the downstream node of the fault interval by the following formula, and the smaller the voltage calculation deviation is, the closer the corresponding position is to the fault point;

[0028]

[0029] wherein, , is a natural number from 1 to ; is the ratio of the length of the interval where the fault point is located to the required accuracy; is the voltage calculation deviation of node j, is the system node impedance matrix after the fault considering the fault node, is the system node current matrix after the fault considering the fault node, is the full node voltage value after the fault , , is the element value of the node impedance matrix between node i and node j when the system is normally running, , is the equivalent impedance between node 0 and node i, is the line impedance between node i and the fault point f.

[0030] Optionally, step (9) combines the results in steps (6) and (8) to further locate the fault by the following formula:​​

[0031] ;

[0032] wherein, is the voltage calculation deviation calculated using the original measured point data, is the voltage calculation deviation calculated using the compressed sensing algorithm reconstructed data, , respectively are the lengths of line ij and line pq; a, b are respectively the weights of the two results.

[0033] Optionally, step (10) obtains the position s when the voltage calculation deviation D is the smallest, at this time, the proportion of the fault distance between the fault point and node i in the fault interval is ;

[0034] wherein s is a natural number from 1 to m; m is the ratio of the length of the interval where the fault point is located to the required accuracy.

[0035] The beneficial effects brought by the above technical scheme are:

[0036] The present application provides a new method for distribution network fault positioning by using a small amount of measured point data in the distribution network through voltage calculation deviation. The present application can effectively solve the problems of inaccurate fault positioning, high cost of measuring devices and the like in the distribution network. The present application is widely applicable, and it has been verified that changing the position of the fault point, the power grid parameters, the fault type and the like will not affect the accuracy of the fault positioning by the present application. The present application can accurately position the fault positioning, effectively reduce the power outage range, and improve the safety, economy and reliability of the operation of the distribution network. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0038] Figure 1 is a flowchart of the present application;

[0039] Figure 2 is an IEEE33 node topology diagram;

[0040] Figure 3 is a reconstructed node vector diagram when AB two-phase short circuit occurs at 20% of section 12-13;

[0041] Figure 4 is a voltage calculation deviation diagram at downstream measuring point 17 when AB two-phase short circuit occurs at 20% of section 12-13;

[0042] Figure 5 The voltage calculation deviation schematic diagram at the fault interval downstream node 13 when the AB two-phase short circuit occurs at 20% of the section 12-13;

[0043] Figure 6 The voltage calculation deviation schematic diagram when the AB two-phase short circuit occurs at 20% of the section 12-13;

[0044] Figure 7 The positioning result and error schematic diagram when different fault types are set at 20% of each section of the IEEE33 node. DETAILED DESCRIPTION

[0045] The application will be further described in detail below with reference to the drawings.

[0046] The application provides a limited information distribution network fault positioning method based on voltage calculation deviation, as shown in the accompanying drawings, comprising the following steps: Figure 1

[0047] Step (1) collects the distribution network topology structure and related parameters, and constructs a distribution network node impedance matrix.

[0048] In the embodiment of the application, the topology structure of the distribution network is collected, the topology structure related data is collected, the branch admittance between each node, the admittance between each node and the zero potential, the total number of nodes N are collected, and all nodes in the topology structure are numbered; the node impedance matrix of the distribution network is constructed according to the topology structure and the line parameters of the distribution network , and the modulus value of all elements in is taken to obtain the node impedance modulus value matrix .

[0049] .

[0050] .

[0051] N is the total number of nodes in the topology structure of the distribution network, is the self-admittance of the i th node, is the mutual admittance between the i th node and the j th node, is the self-impedance of the i th node, is the mutual impedance between the i th node and the j th node, is the branch admittance between the i th node and the zero potential node, is the branch admittance between the i th node and the j th node.

[0052] Step (2) constructs a distribution network node monitoring system based on a small number of monitoring points, and monitors the voltage and current signals of a small number of nodes of the distribution network in real time. ​

[0053] In the embodiment of the present application, a few monitoring point based power distribution network node monitoring system is constructed based on the installed muPMU device, and the voltage and current signals of a few nodes of the power distribution network are monitored in real time; the monitoring point positions that must be installed in the power distribution network are: the nodes at the outlet of the reference power supply of the power distribution network; the nodes with three branches and above; and the end nodes in the topology structure of the power distribution network.

[0054] Step (3) judges whether the power distribution network has a fault by monitoring the line voltage of the nodes.

[0055] In the embodiment of the present application, whether the power distribution network has a fault is judged according to the following formula:

[0056]

[0057] In the formula, is the minimum value of the line voltage of the jth node, is the setting value, and is taken as , is the rated line voltage of the system.

[0058] Step (4) calculates the positive sequence line voltage variation modulus of each monitoring node when the power distribution network has a fault.

[0059] In the embodiment of the present application, when the power distribution network has a fault, the fault voltage of the monitoring point when the system has a fault and the fault current of the monitoring point are obtained, the positive sequence voltage data of the system in the steady state period and the normal operation period are used to obtain the corresponding node positive sequence line voltage variation modulus , wherein the calculation method of the positive sequence voltage variation modulus of the jth node is shown in the following formula:

[0060]

[0061] In the formula, is the positive sequence measurement voltage before the fault of the jth node, is the positive sequence measurement voltage after the fault of the jth node.

[0062] Step (5) reconstructs the node current vector and the node current value by using the basis pursuit compressed sensing algorithm, and judges the fault interval according to the reconstructed node current vector.

[0063] In the embodiment of the present application, the underdetermined node injection fault current equation is constructed, the compressed sensing algorithm based on the basis pursuit is used for calculation, the reconstructed node current vector and the node current calculation value I are obtained.

[0064]

[0065] In the formula, ​​​reconstructing a node current vector, a node impedance matrix in normal operation of the distribution network, a positive sequence fault voltage variation;

[0066] observing the reconstructed node current vector judging the fault section;

[0067]

[0068] is an n x 1 matrix, wherein the non-zero elements , The order i and j of the non-zero elements are nodes in the fault section, and thus the fault section is i-j.

[0069] Step (6) uses the original measurement point data of the downstream nodes of the measurement point section where the fault section is located to calculate the fault position of the measurement point information by using the voltage calculation deviation method.

[0070] In the embodiment of the application, considering the instability of the compressed sensing algorithm, the voltage calculation deviation of the downstream measurement points of the measurement point section where the fault section is located is calculated using the original measurement point data, and the smaller the voltage calculation deviation is, the closer the corresponding position is to the fault point; the voltage calculation deviation of the downstream nodes of the measurement point section is as follows:

[0071]

[0072] wherein, , is a natural number from 1 to ; is the ratio of the length of the measurement device section where the fault section is located to the required accuracy; is the voltage calculation deviation of the downstream node q of the nearest measurement device section on the two sides of the fault section p-q, , are the measured voltages of node q before and after the fault, is the line impedance between node p and the fault point f, , is the element value of the node impedance matrix between node p and node q in normal operation.

[0073] Step (7) uses the reconstructed node current vector to back-propagate to obtain the fault post-full node voltage value of the system .

[0074] Step (8) calculates the fault position of the reconstructed information by calculating the voltage calculation deviation of the downstream nodes of the fault section.

[0075] ​​In the embodiment of the present application, the voltage calculation deviation of the downstream node of the fault interval is calculated by the following formula, and the smaller the voltage calculation deviation is, The corresponding position is closer to the fault point.

[0076] ;

[0077] Among them, , is a natural number from 1 to , is the ratio of the length of the interval where the fault point is located to the required accuracy; is the voltage calculation deviation of node j, is the system node impedance matrix considering the fault node after the fault occurs, is the system node current matrix considering the fault node after the fault occurs, is the full node voltage value after the fault , , is the element value of the node impedance matrix between node i and node j when the system is normally running, , is the equivalent impedance between node 0 and node i, is the line impedance between node i and the fault point f.

[0078] Step (9) combines the measuring point information and the reconstruction information in steps (6) and (8).

[0079] In the embodiment of the present application, the results in steps (6) and (8) are combined to further locate the fault by the following formula:

[0080] ;

[0081] Among them, is the voltage calculation deviation calculated by using the original measuring point data, is the voltage calculation deviation calculated by using the reconstruction data of the compressed sensing algorithm, , are the lengths of lines ij and pq respectively; a and b are the weights of the two results respectively.

[0082] Step (10) is to locate the accurate fault.

[0083] In the embodiment of the present application, the position s at which the voltage calculation deviation D is the smallest is obtained, and at this time, the proportion of the fault distance between the fault point and node i to the fault interval is ;

[0084] Among them, s is a natural number from 1 to m; m is the ratio of the length of the interval where the fault point is located to the required accuracy.

[0085] The application is illustrated below by examples.

[0086] An IEEE33 node simulation diagram is built in MATLAB / SIMULINK, and the line topology is shown in Figure 2 The sampling frequency of the simulation is 4k Hz, the reference voltage of the power supply network first end is 12.66k V, the neutral point is directly grounded in operation, and the total load of the network is 5084.26+j2547.32kVA. There are totally 33 nodes, 32 branches and 5 tie switch branches in the system. For the area between node 0 and node 1, the line impedance is very small, and can be regarded as the equivalent impedance of the power supply. Measurement points are installed at 7 positions of the 1st, 2nd, 5th, 17th, 21st, 24th and 32nd nodes. When the node admittance matrix is generated, the reference node 0 needs to be removed, so the power saving admittance matrix is 32-order, and the area that can be located is the 32 areas contained by nodes 1 to 33 in the distribution network;

[0087] In the embodiment of the application, as shown in Figure 3 A fault point is set at 20% of the section 12-13 in the example of the application, and the fault type is AB two-phase short circuit, at this time, the positive sequence fault voltage variation measured by the 7 measurement devices is obtained by the basis pursuit algorithm. As can be seen from Figure 3 , the nodes 12 and 13 are non-zero elements, so the fault occurs in the section 12-13.

[0088] From the topological structure of the distribution network, it can be seen that the two devices on both sides of the section 12-13 exist at the nodes 5 and 17, so the data at the downstream node 17 is used for the next positioning. The positioning accuracy is set to 0.1% of the line length.

[0089] In the embodiment of the application, as can be seen from Figure 4 , the proportion corresponding to the minimum voltage calculation deviation of the downstream node of the measurement point interval is 55.5%, that is, the fault position is 55.5% of the measurement point section 5-17, which is converted to 18.774% of the section 12-13, and the relative error of the distance measurement is 1.226%.

[0090] In the embodiment of the application, as can be seen from Figure 5 , the proportion corresponding to the minimum voltage calculation deviation of the downstream node of the fault interval is 24.1%, that is, the fault position is 24.1% of the fault section 12-13, and the relative error of the distance measurement is 4.1%.

[0091] Combining the above two fault criteria, the fault section 12-13 accounts for 0.075503 of the measurement point section 5-17, so a=0.075503 and b=0.924491, as shown in Figure 6 , the accurate voltage calculation deviation is obtained.

[0092] FromFigure 6 The fault location is accurately known to be at 23.7% of the section 12-13, and the relative error of distance measurement is 3.7%, which proves that the positioning effect of the application is accurate.

[0093] In the embodiment of the application, Figure 7 It can be known that the positioning method is not affected by the fault location and the fault type, which shows that the fault positioning method is effective.

Claims

1. A method for fault location in a power distribution network with limited information based on voltage calculated deviation, characterized in that: It comprises the following steps: Step (1) Collect the distribution network topology and related parameters, and construct the distribution network node impedance matrix; Step (2) Construct a distribution network node monitoring system based on a small number of monitoring points to monitor the voltage and current signals of a small number of nodes in the distribution network in real time; Step (3) Determine whether a fault occurs in the distribution network by monitoring the line voltage of the nodes; Step (4) When a fault occurs in the distribution network, calculate the positive sequence line voltage change value of each monitoring node; Step (5) Use the basis pursuit compressed sensing algorithm to reconstruct the node current vector and the node current value, and determine the fault interval according to the reconstructed node current vector; Step (6) Use the original monitoring point data of the downstream nodes in the fault interval to calculate the fault position by the voltage calculation deviation method; Step (7) Use the reconstructed node current vector to back-propagate the full node voltage value of the system after the fault; Step (8) Calculate the fault position by the reconstructed information by calculating the voltage calculation deviation of the downstream nodes in the fault interval; Step (9) Combine the monitoring point information and the reconstructed information in steps (6) and (8); Step (10) Accurately locate the fault.

2. The method for fault location of a power distribution network with limited information based on voltage calculated deviation according to claim 1, characterized in that: Step (4) When a fault occurs in the distribution network, the monitoring point fault voltage and the monitoring point fault current of the system are obtained, and the positive sequence voltage data of the system during the fault steady state period and the normal operation period are used to obtain the corresponding node positive sequence line voltage change value, wherein the positive sequence voltage change value of the jth node is calculated as shown in the following formula: ； In the formula: is the positive sequence measured voltage before the jth node fault, is the positive sequence measured voltage after the jth node fault.

3. The method of claim 1, wherein the method further comprises: Step (5) constructs the underdetermined node injection fault current equation, and calculates the reconstructed node current vector by using the compressive sensing algorithm based on basis pursuit and the calculated node current I; ； In the formula, is the reconstructed node current vector, is the node impedance matrix in normal operation of the distribution network, is the positive sequence fault voltage variation; Observe the reconstructed node current vector to determine the fault interval; ； is an n x 1 matrix with non-zero elements , The order i and j are fault interval nodes, so the fault interval is i-j.

4. The method of claim 1, wherein the method further comprises: Step (6) Considering the instability of the compressed sensing algorithm, the voltage calculation deviation of the downstream measuring points in the fault section is first calculated using the original measuring point data. The smaller the voltage calculation deviation, the better. The closer the corresponding location is to the fault point, the more accurate the following formula is: the voltage calculation deviation of the downstream node of the measurement point interval. ； wherein, , is a natural number from 1 to ; is the ratio of the length of the measurement device interval in which the fault interval is located to the required accuracy; is the voltage calculation bias of the downstream node q of the nearest measurement device interval on both sides of the fault interval p-q, , are the measured voltages of node q before and after the fault, respectively, is the line impedance between node p and the fault point f, , is the element value of the node impedance matrix between node p and node q in normal operation.

5. The method of claim 1, wherein the method further comprises: Step (8) calculates the voltage calculation deviation of the downstream node of the fault section by the following formula, the smaller the voltage calculation deviation, The corresponding position is closer to the fault point. ； wherein, , is a natural number from 1 to , is the ratio of the length of the interval in which the fault point is located to the required accuracy; is the voltage calculation deviation of node j, is the system node impedance matrix considering the fault node after the fault occurs, is the system node current matrix considering the fault node after the fault occurs, is the full node voltage value after the fault , , is the element value of the node impedance matrix between node i and node j when operating normally, , shows the equivalent impedance between node 0 and node i, is the line impedance between node i and the fault point f.

6. The method of claim 1, wherein the method further comprises: Step (9) Combine the results in steps (6) and (8) to further locate the fault by the following formula: ； wherein, the voltage calculated deviation for step (6) using raw measurement point p and q data, the voltage calculated deviation for step (8) using compressed sensing algorithm reconstruction data, , respectively the length of line ij and line pq; a, b are the weight of the two results respectively.

7. The method of claim 1, wherein the method further comprises: Step (10) obtains the position s at which the voltage calculation deviation D is the smallest, at which time the proportion of the fault distance between the fault point and the node i in the fault interval is ; Where s is a natural number from 1 to m; m is the ratio of the length of the interval where the fault point is located to the required accuracy.

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