CN117761465A - Short-circuit fault positioning method for photovoltaic-containing power distribution network - Google Patents
Short-circuit fault positioning method for photovoltaic-containing power distribution network Download PDFInfo
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Abstract
The invention discloses a method for positioning short-circuit faults of a photovoltaic-containing power distribution network. When the short-circuit fault of the power distribution network is distinguished and identified, the main node of the fault section is different from fault information uploaded by feeder terminal units at the sub-nodes, the section is judged to be the fault section, a network description matrix and a fault information matrix are established based on a matrix algorithm, the network description matrix and the fault information matrix are added to obtain a fault judgment matrix, fault positioning criteria are formed by utilizing the characteristics of the fault section, and the positioning of the fault section of the power distribution network containing the photovoltaic is realized. And establishing a switching function suitable for fault positioning of the photovoltaic power distribution network, and combining a matrix algorithm with a modified sine and cosine algorithm to search an optimal solution so as to realize accurate positioning of a fault section. The method can greatly improve the fault positioning speed of the power distribution network, has higher accuracy and certain fault tolerance, can effectively avoid time and labor consumption when on-site operation and maintenance personnel line inspection, and improves the power supply reliability of the power distribution network.
Description
Technical Field
The invention relates to the technical field of power distribution network fault positioning, in particular to a short-circuit fault positioning method for a photovoltaic-containing power distribution network.
Background
With the rapid development of the distributed power generation technology, the distributed power supply is generally directly connected to the power distribution network due to the constraint of geographic positions, and the power distribution network is used as a key link directly connected with power loads in power generation, transmission, transformation and distribution of a power system, so that the connection of the distributed power supply is beneficial to improving the power supply reliability of power users. However, the access of distributed power sources also presents new challenges for the operation of the distribution network. More than 85% of fault power failures in the power system are caused by power distribution network faults, the traditional radiation type power distribution network is changed into a complex network with multiple power sources due to the access of the distributed power sources, and the relay protection setting, fault positioning and power supply recovery scheme of the traditional power distribution network can be disabled due to the dynamic switching and the random characteristic of output power in the running process of the distributed power sources. Therefore, a fault locating method for the distribution network with the distributed power supply needs to be studied intensively.
The prior art has the following defects:
the traditional fault section positioning method for the distribution network with the distributed power supply can realize the positioning of the fault section of the distribution network only when the output power of the distributed power supply is kept constant. In practice, the distributed power supply is affected by weather, environment and other factors, and the output power changes randomly. When a short-circuit fault occurs in the Korean distributed power distribution network, if the output power of the distributed power supply is smaller and the provided fault overcurrent does not reach the FTU setting value, the fault information uploaded by the FTU may be missed in a large scale, so that the power distribution network section positioning method based on the FTU fails.
Disclosure of Invention
The invention aims to provide a short-circuit fault positioning method for a photovoltaic-containing power distribution network, which aims to solve the defects in the background technology.
In order to achieve the above object, the present invention provides the following technical solutions: the fault positioning method for the photovoltaic power distribution network comprises the following steps of:
s1: distinguishing the difference of fault information uploaded by the FTU at the main node and the sub node of the fault section of the power distribution network;
s2: establishing a network description matrix and a fault information matrix based on a matrix algorithm;
s3: adding the network description matrix and the fault information matrix to obtain a fault judgment matrix, and forming a fault positioning criterion by utilizing the fault section characteristics;
s4: establishing a switching function suitable for fault location of the photovoltaic-containing power distribution network;
s5: and combining a matrix algorithm with a modified sine and cosine algorithm to search an optimal solution, so as to realize accurate positioning of the fault section.
In a preferred embodiment: in step S1, the mechanism for uploading fault information by the FTU is as follows:
s1.1: determining a setting value through calculating a main power supply of the system and upstream and downstream photovoltaic short-circuit currents;
s1.2: the current amplitude of the FTU flowing through a certain place is larger than the setting value, namely the FTU monitors fault overcurrent; the fault overcurrent direction is distinguished, and the direction from a main power supply of the system to the tail end of a feeder line or a photovoltaic power supply is specified to be the positive direction of the whole network;
s1.3: according to whether fault overcurrent is detected or not and whether the fault overcurrent direction is consistent with the positive direction of the whole network or not, each FTU in the DG-containing power distribution network is provided with three working modes of '-1, 0 and 1': when a short-circuit fault occurs in the photovoltaic power distribution network, if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is consistent with the positive direction of the whole network, the FTU uploads information to a power distribution main station as 1; if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is opposite to the positive direction of the whole network, uploading information to be "-1"; if a certain FTU does not detect the fault overcurrent, the upload information is "0".
In a preferred embodiment: in step S2, establishing a network description matrix and a fault information matrix based on a matrix algorithm includes the following steps:
s2.1: according to the graph theory related knowledge, taking the whole power distribution network as a graph, taking all the circuit breakers, the sectionalizing switches and the interconnecting switches in the power distribution network as nodes, and establishing a network description matrix D;
s2.2: defining a main node as a node i, a sub-node as a node j, and setting a non-diagonal element D in a network description matrix D ij Otherwise, set it to 0, and set diagonal elements in the network description matrix D to 0;
s2.3, setting a main node as a node i and a child node as a node j in the fault information matrix G, wherein diagonal elements of the fault information matrix G are fault information uploaded by FTU at each node in the power distribution network respectively, and non-diagonal elements are all set to 0.
In a preferred embodiment: in step S3, establishing a fault determination matrix and forming a fault location criterion according to the fault section characteristics includes the following steps:
s3.1: performing matrix addition operation on the network description matrix D and the fault information matrix G to obtain a fault judgment matrix P, wherein off-diagonal elements of the fault judgment matrix P represent topological connection relations among nodes in the power distribution network, and diagonal elements of the off-diagonal elements represent whether fault overcurrent flows through the nodes in the power distribution network;
s3.2: and constructing a matrix algorithm fault positioning criterion according to the characteristics of different uploading fault information of the main node FTU and the sub node FTU of the fault section.
In a preferred embodiment: in step S3.2, the conditions for constructing the fault locating criteria of the matrix algorithm are as follows:
s3.2.1: main nodei. When the double-end feeder line section formed by the child nodes j has a short circuit fault, if the distribution network has a single fault: if p ii =1, all p ij =1 i +.j, p jj =0 or-1; if multiple faults occur in the power distribution network: if p ii =0, all p ij =1 i +.j, p jj ＝-1；
S3.2.2: when a short circuit fault occurs in a terminal feeder line section formed by the main node i, if a single fault occurs in the power distribution network: if p ii =1, all p ij ＝1 i≠j。
In a preferred embodiment: in step S3.2, further including performing fault location of the photovoltaic-containing power distribution network according to a matrix algorithm, including:
s3.2.3: establishing a network description matrix D containing a photovoltaic power distribution network and a fault information matrix G, and adding the two matrixes to obtain a fault judgment matrix P;
s3.2.4: judging which nodes together form a T-joint section by searching non-diagonal elements in the fault judging matrix P line by line;
s3.2.5: for each T-joint section, obtaining fault information uploaded by FTU at a main node and two sub-nodes forming the T-joint section by searching diagonal elements in a fault judgment matrix P;
s3.2.6: comparing the fault information uploaded by the FTU at the main node of the T-joint section with the fault information uploaded by the FTU at the two sub-nodes respectively, and judging the state of the T-joint section twice according to a matrix algorithm fault positioning criterion;
s3.2.7: if the judging result of the two section states is consistent, the section state of the T-joint section can be directly obtained; if the fault information is inconsistent, judging the section state of the T-joint section according to the fault information uploaded by the FTU at the main node of the T-joint section;
s3.2.8: if the FTU uploading information at the main node of the T-joint section is 1, the T-joint section is a normal section; if the upload information is "0", the T-junction zone is a faulty zone.
In a preferred embodiment: in the step 3.2 of the process,
step S3.2.4 specifically includes: according to the first fault judgment matrix PJudging whether a T-joint section exists or not according to the number of off-diagonal elements with the value of 1 in the i rows; the judgment principle is as follows: if the row has only one off-diagonal element p ij The section formed by the nodes corresponding to the row number i and the column number j is a non-T-joint section, i corresponds to the main node of the section, and j corresponds to the sub-node of the section; if there are two off-diagonal elements p in the row ij ＝p ik The section formed by the nodes corresponding to the row number i and the column number j and k is a T-joint section, i corresponds to the main node of the T-joint section, and j and k respectively correspond to the sub-nodes of the T-joint section;
in step S3.2.6: if the section formed by the main node and the sub node is a non-T-joint section, judging the state of the non-T-joint section once by using a matrix algorithm fault positioning criterion, namely the correct section state;
if the section formed by the main node and the sub node is a T-joint section, judging the state of the T-joint section twice by using a matrix algorithm fault positioning criterion; if the two judging results of the T-joint section state are consistent, the T-joint section state is the judging state; if not, according to the fault information p uploaded by the FTU at the main node of the T-joint section ii And judging the state of the T-joint section.
In a preferred embodiment: in step S4, a switching function suitable for fault location of the photovoltaic-containing power distribution network is established as follows:
s4.1: setting a switching function model suitable for fault location of the photovoltaic power distribution network;
s4.2: definition of the calculated value of the switching functionTotal number of feeder sections N in the upstream and downstream region of switch j 1 、N 2 The method comprises the steps of carrying out a first treatment on the surface of the Nth zone upstream of switch j 1 Status x of each feeder line section l (n 1 ) Nth in the upstream region of switch j 2 Status x of each feeder line section l (n 2 ) Normally "1", and failure "0"; power supply access coefficient K of switch j up and down stream 1 、K 2 ；
S4.3: when the upper and lower power supplies of the switch j are respectively and directly connected with the switch j, namely, the power supplies continuously supply power to the switch j, the value is 1, and when the upper and lower power supplies are respectively separated from a passage between the switch j by a fault point, the value is 0;
s4.4: define the number S of upstream and downstream of the switch j 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the Status of switch j to feeder section experienced on its upstream power pathStatus of switch j to feeder section seen on its downstream power supply path +.>
In a preferred embodiment: in step S5, the matrix algorithm and the modified sine and cosine algorithm are combined to search the optimal solution, so as to realize accurate positioning of the fault section, which specifically includes the following steps:
s5.1: all feeder line sections obtained from the fault positioning result of the matrix algorithm are called as suspected fault sections, and the number of the suspected fault sections is determined;
s5.2: if the number of the suspected fault sections is only 1, the fact that the matrix algorithm fault positioning result is correct is indicated, and a fault positioning method based on an improved sine and cosine algorithm is not needed;
s5.3: if the number of the suspected fault sections is not less than 2, a true fault section is found out from the suspected fault sections by using a modified sine and cosine algorithm.
In a preferred embodiment: in step 5.3, the steps based on the modified sine and cosine algorithm are as follows:
s5.3.1: constructing an expected function of the suspected fault section and writing a fitness function;
s5.3.2: setting a population rule module, initializing all individual positions in the population by random 0 or 1, and setting iteration times and algorithm parameters;
s5.3.3: and calculating fitness values of all individuals in the initial population once according to the objective function, and recording the optimal individual positions.
S5.3.4: binary conversion is carried out on the sinusoidal algorithm, the position of the population is updated, each individual fitness value of the population is recalculated, the fitness value of the optimal position recorded last time is compared, and if the fitness value of the t+1st time is smaller than the fitness value of the t time, the optimal position and the fitness value of the population are replaced and used as the basis of the next update;
s5.3.5: judging whether an iteration termination condition is met, if so, outputting an optimal individual and a fitness value thereof in the population, wherein the position of the optimal individual is the actual running state of each section of the power distribution network, and if not, continuing to execute the step S5.3.4 until the maximum iteration times are reached;
s5.3.6: and determining a fault interval according to the individual position information, namely the running state of the power distribution network.
In the technical scheme, the invention has the technical effects and advantages that:
when the short-circuit fault of the power distribution network is distinguished and identified, the fault information uploaded by the FTU at the main node and the sub node of the fault section is different, the section is judged to be the fault section, a network description matrix and a fault information matrix are established based on a matrix algorithm, the network description matrix and the fault information matrix are added to obtain a fault judgment matrix, and fault positioning criteria are formed by utilizing the characteristics of the fault section, so that the positioning of the fault section of the power distribution network containing the photovoltaic is realized. On the basis, aiming at the problem that the fault positioning capacity of a matrix algorithm is poor when the fault information uploaded by the FTU is incomplete, a switching function suitable for fault positioning of the photovoltaic power distribution network is established, and the matrix algorithm and the modified sine and cosine algorithm are combined to search an optimal solution, so that accurate positioning of a fault section is realized. The method can greatly improve the fault positioning speed of the power distribution network, has higher accuracy and certain fault tolerance, can effectively avoid time and labor consumption when on-site operation and maintenance personnel line inspection, and improves the power supply reliability of the power distribution network.
Drawings
Fig. 1 is a flowchart of a method for positioning a short-circuit fault of a power distribution network including photovoltaic according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, 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.
Referring to fig. 1, the method for positioning a short-circuit fault of a photovoltaic-containing power distribution network according to the embodiment includes the following steps:
s1: distinguishing the difference of fault information uploaded by the FTU at the main node and the sub node of the fault section of the power distribution network;
s2: establishing a network description matrix and a fault information matrix based on a matrix algorithm;
s3: adding the network description matrix and the fault information matrix to obtain a fault judgment matrix, and forming a fault positioning criterion by utilizing the fault section characteristics;
s4: establishing a switching function suitable for fault location of the photovoltaic-containing power distribution network;
s5: and combining a matrix algorithm with a modified sine and cosine algorithm to search an optimal solution, so as to realize accurate positioning of the fault section.
According to the method, when the power distribution network has short-circuit faults through distinguishing and identifying, the fault information uploaded by the FTU at the main node and the sub node of the fault section is different, the fault section is judged to be the fault section, a network description matrix and a fault information matrix are established based on a matrix algorithm, the network description matrix and the fault information matrix are added to obtain a fault judgment matrix, fault positioning criteria are formed by utilizing the characteristics of the fault section, and the positioning of the fault section of the power distribution network containing the photovoltaic is realized. On the basis, aiming at the problem that the fault positioning capacity of a matrix algorithm is poor when the fault information uploaded by the FTU is incomplete, a switching function suitable for fault positioning of the photovoltaic power distribution network is established, and the matrix algorithm and the modified sine and cosine algorithm are combined to search an optimal solution, so that accurate positioning of a fault section is realized.
In a preferred embodiment, in step S1, the FTU uploads the fault information mechanism as follows:
s1.1: calculating the minimum short-circuit current provided by a main power supply of the system and the upstream photovoltaic of the FTU and the minimum reverse short-circuit current provided by the downstream photovoltaic of the FTU, wherein the minimum short-circuit current and the minimum reverse short-circuit current are the setting values of the FTU;
s1.2: the current amplitude of the FTU flowing through a certain place is larger than the setting value, namely the FTU monitors fault overcurrent; meanwhile, the fault overcurrent direction is distinguished, and the direction from a main power supply of the system to the tail end of a feeder line or a photovoltaic power supply is specified to be the positive direction of the whole network;
s1.3: according to whether fault overcurrent is detected or not and whether the fault overcurrent direction is consistent with the positive direction of the whole network or not, each FTU in the DG-containing power distribution network is provided with three working modes of '-1, 0 and 1': when a short-circuit fault occurs in the photovoltaic power distribution network, if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is consistent with the positive direction of the whole network, the FTU uploads information to a power distribution main station as 1; if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is opposite to the positive direction of the whole network, uploading information to be "-1"; if a certain FTU does not detect the fault overcurrent, the upload information is "0".
In a preferred embodiment, in step S2, the establishing of the network description matrix and the fault information matrix based on the matrix algorithm comprises the steps of:
s2.1: according to the graph theory related knowledge, taking the whole power distribution network as a graph, taking all the circuit breakers, the sectionalizing switches and the interconnecting switches in the power distribution network as nodes, and establishing a network description matrix D;
s2.2: defining a main node as a node i, a sub-node as a node j, and setting a non-diagonal element D in a matrix D ij Otherwise, set it to 0, and the diagonal elements in matrix D are all set to 0;
s2.3, setting a main node as a node i in a fault information matrix G, a child node as a node j, wherein diagonal elements of the matrix G are fault information uploaded by FTU at each node in the power distribution network respectively, and non-diagonal elements are all set to 0.
In a preferred embodiment, in step S3, establishing the fault determination matrix and forming the fault location criterion based on the fault section characteristics comprises the steps of:
s3.1: performing matrix addition operation on the network description matrix D and the fault information matrix G to obtain a fault judgment matrix, wherein off-diagonal elements of the fault judgment matrix P represent topological connection relations among nodes in the power distribution network, and diagonal elements of the off-diagonal elements represent whether fault overcurrent flows through the nodes in the power distribution network;
s3.2: and constructing a matrix algorithm fault positioning criterion according to the characteristics of different uploading fault information of the main node FTU and the sub node FTU of the fault section.
In a preferred embodiment, in step S3.2, the construction matrix algorithm fault localization criteria are as follows:
s3.2.1: when a short circuit fault occurs in a double-end feeder line section formed by the main node i and the sub node j, if a single fault occurs in the power distribution network: if pii=1, all p ij =1 (i+.j), there are pjj =0 or-1; if multiple faults occur in the power distribution network: if pii=0, all p ij =1 (i+.j), p jj ＝-1；
S3.2.2: when a short circuit fault occurs in a terminal feeder line section formed by the main node i, if a single fault occurs in the power distribution network: if pii=1, all p ij ＝0(i≠j)。
In a preferred embodiment, in step S3.2, the matrix algorithm fault localization is as follows:
s3.2.3: establishing a network description matrix D containing a photovoltaic power distribution network and a fault information matrix G, and adding the two matrixes to obtain a fault judgment matrix P;
s3.2.4: judging which nodes together form a T-joint section by searching non-diagonal elements in the fault judging matrix P line by line;
s3.2.5: for each T-joint section, obtaining fault information uploaded by FTU at a main node and two sub-nodes forming the T-joint section by searching diagonal elements in a fault judgment matrix P;
s3.2.6: comparing the fault information uploaded by the FTU at the main node of the T-joint section with the fault information uploaded by the FTU at the two sub-nodes respectively, and judging the state of the T-joint section twice according to a matrix algorithm fault positioning criterion;
s3.2.7: if the judging result of the two section states is consistent, the section state of the T-joint section can be directly obtained; if the fault information is inconsistent, judging the section state of the T-joint section according to the fault information uploaded by the FTU at the main node of the T-joint section;
s3.2.8: if the FTU uploading information at the main node of the T-joint section is 1, the T-joint section is a normal section; if the upload information is "0", the T-junction zone is a faulty zone.
The implementation method specifically comprises the following steps:
s3.2.9: based on the step 3.1, forming a network description matrix D and a fault information matrix G according to the topological connection relation among all nodes in the power distribution network and fault information uploaded by the FTU, and adding the two matrixes to obtain a fault judgment matrix P;
s3.2.10: judging whether a T-joint section exists or not according to the number of off-diagonal elements with the value of 1 in the ith row of the fault judgment matrix P; the judgment principle is as follows: if the row has only one off-diagonal element p ij The section formed by the nodes corresponding to the row number i and the column number j is a non-T-joint section, i corresponds to the main node of the section, and j corresponds to the sub-node of the section; if there are two off-diagonal elements p in the row ij ＝p ik The section formed by the nodes corresponding to the row number i and the column number j and k is a T-joint section, i corresponds to the main node of the T-joint section, and j and k respectively correspond to the sub-nodes of the T-joint section;
s3.2.11: based on the step S3.2.10, if the section formed by the main node and the sub node is a non-T-joint section, the state of the non-T-joint section is judged once by using a matrix algorithm fault positioning method, namely the correct section state;
s3.2.12: on the basis of the step S3.2.10 judgment, if the section formed by the main node and the sub node is a T-joint section, judging the state of the non-T-joint section twice by using a matrix algorithm fault positioning method;
s3.2.13: based on the determination in step S3.2.12, if the two determinations of the state of the T-junction segment are consistent, the state of the T-junction segment is the determination state; if not, according to the fault information p uploaded by the FTU at the main node of the T-joint section ii Judging the state of the T-joint section;
s3.2.14: based on step S3.2.13, if the FTU uploads the information p at the T-junction block master node i ii If the T joint section is 1, judging that the T joint section is a normal section; if upload information p ii If the T-joint section is 0, the T-joint section can be judged to be a fault section;
s3.2.15: and judging whether all N rows of elements of the fault judgment matrix P are analyzed. If the analysis is not completed, the process goes to the step S3.2.10 to continue the analysis of the next row; and if the analysis is finished, outputting all fault sections, and ending the fault positioning.
In a preferred embodiment, in step S4, a switching function suitable for fault localization of the photovoltaic-containing power distribution network is established as follows:
s4.1: setting a switching function model suitable for fault location of the photovoltaic power distribution network;
s4.2: definition of the calculated value of the switching functionTotal number of feeder sections N in the upstream and downstream region of switch j 1 、N 2 The method comprises the steps of carrying out a first treatment on the surface of the Nth zone upstream of switch j 1 Status x of each feeder line section l (n 1 ) Nth in the upstream region of switch j 2 Status x of each feeder line section l (n 2 ) Normally "1", and failure "0"; power supply access coefficient K of switch j up and down stream 1 、K 2 ；
S4.3: when the upper and lower power supplies of the switch j are respectively and directly connected with the switch j, namely, the power supplies continuously supply power to the switch j, the value is 1, and when the upper and lower power supplies are respectively separated from a passage between the switch j by a fault point, the value is 0;
s4.4: define the number S of upstream and downstream of the switch j 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the Status of switch j to feeder section experienced on its upstream power pathStatus of switch j to feeder section seen on its downstream power supply path +.>
In a preferred embodiment, in step S5, the principle of fault location of the photovoltaic-containing power distribution network by combining the matrix algorithm with the modified sine and cosine algorithm is as follows:
s5.1: all feeder line sections obtained from the fault positioning result of the matrix algorithm are called as suspected fault sections, and the number of the suspected fault sections is determined;
s5.2: if the number of the suspected fault sections is only 1, the fact that the matrix algorithm fault positioning result is correct is indicated, and a fault positioning method based on an improved sine and cosine algorithm is not needed;
s5.3: if the number of the suspected fault sections is not less than 2, the fact that multiple faults can occur in the power distribution network containing the photovoltaic power is indicated, and the fault positioning misjudgment of a matrix algorithm is also possible, so that a real fault section needs to be found out from the suspected fault sections by using a modified sine and cosine algorithm.
In a preferred embodiment, in step 5.3, the modified sine and cosine based algorithm steps are as follows:
s5.3.1: constructing an expected function of the suspected fault section and writing a fitness function;
s5.3.2: setting a population rule module, initializing all individual positions in the population by random 0 or 1, and setting iteration times and algorithm parameters;
s5.3.3: and calculating fitness values of all individuals in the initial population once according to the objective function, and recording the optimal individual positions.
S5.3.4: binary conversion is carried out on the sinusoidal algorithm, the position of the population is updated, each individual fitness value of the population is recalculated, the fitness value of the optimal position recorded last time is compared, and if the fitness value of the t+1st time is smaller than the fitness value of the t time, the optimal position and the fitness value of the population are replaced and used as the basis of the next updating.
S5.3.5: judging whether an iteration termination condition is met, if so, outputting an optimal individual and a fitness value thereof in the population, wherein the position of the optimal individual is the actual running state of each section of the power distribution network, and if not, continuing to execute the step S5.3.4 until the maximum iteration times are reached;
s5.3.6: and determining a fault interval according to the individual position information, namely the running state of the power distribution network.
Binary conversion is carried out on the basis of the improved sine and cosine algorithm, and the specific implementation process is as follows:
first, pass r according to equation (1) before each update 4 Generating a random number and comparing with a threshold value of 0.5 to select whether to update the position by using a cosine function or a sine function。
For facilitating subsequent analysis, define V i t ：
And finally binarizing the individual position by adopting a sigmoid function (4). The binary conversion rule of the individual position is shown in formula (5).
After binary conversion, the algorithm is easy to be trapped into local optimization, so that the improved sine and cosine algorithm needs to keep a stagnation disturbance strategy in fault location of the power distribution network. The binary conversion rule of the new individual position generated by the Lewy disturbance update formulas (6) and (7) is shown as formula (8).
Substituting the running state information of each section of the power distribution network into an objective function for analysis and solving, comparing various possible running states, wherein the running state with the smallest result value is the most likely actual running state, and the running mode determines the position where the fault point can be found.
Claims (10)
1. A method for positioning short-circuit faults of a photovoltaic-containing power distribution network is characterized by comprising the following steps of: the method comprises the following steps:
s1: distinguishing the difference of fault information uploaded by the FTU at the main node and the sub node of the fault section of the power distribution network;
s2: establishing a network description matrix and a fault information matrix based on a matrix algorithm;
s3: adding the network description matrix and the fault information matrix to obtain a fault judgment matrix, and forming a fault positioning criterion by utilizing the fault section characteristics;
s4: establishing a switching function suitable for fault location of the photovoltaic-containing power distribution network;
s5: and combining a matrix algorithm with a modified sine and cosine algorithm to search an optimal solution, so as to realize accurate positioning of the fault section.
2. The fault location method for a photovoltaic-containing power distribution network according to claim 1, wherein: in step S1, the mechanism for uploading fault information by the FTU is as follows:
s1.1: determining a setting value through calculating a main power supply of the system and upstream and downstream photovoltaic short-circuit currents;
s1.2: the current amplitude of the FTU flowing through a certain place is larger than the setting value, namely the FTU monitors fault overcurrent; the fault overcurrent direction is distinguished, and the direction from a main power supply of the system to the tail end of a feeder line or a photovoltaic power supply is specified to be the positive direction of the whole network;
s1.3: according to whether fault overcurrent is detected or not and whether the fault overcurrent direction is consistent with the positive direction of the whole network or not, each FTU in the DG-containing power distribution network is provided with three working modes of '-1, 0 and 1': when a short-circuit fault occurs in the photovoltaic power distribution network, if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is consistent with the positive direction of the whole network, the FTU uploads information to a power distribution main station as 1; if a certain FTU detects fault overcurrent and the direction of the fault overcurrent is opposite to the positive direction of the whole network, uploading information to be "-1"; if a certain FTU does not detect the fault overcurrent, the upload information is "0".
3. The fault location method for a photovoltaic-containing power distribution network according to claim 2, wherein: in step S2, establishing a network description matrix and a fault information matrix based on a matrix algorithm includes the following steps:
s2.1: according to the graph theory related knowledge, taking the whole power distribution network as a graph, taking all the circuit breakers, the sectionalizing switches and the interconnecting switches in the power distribution network as nodes, and establishing a network description matrix D;
s2.2: defining a main node as a node i, a sub-node as a node j, and setting a non-diagonal element D in a network description matrix D ij Otherwise, set it to 0, and set diagonal elements in the network description matrix D to 0;
s2.3, setting a main node as a node i and a child node as a node j in the fault information matrix G, wherein diagonal elements of the fault information matrix G are fault information uploaded by FTU at each node in the power distribution network respectively, and non-diagonal elements are all set to 0.
4. A method for locating faults in a photovoltaic-containing power distribution network as claimed in claim 3, wherein: in step S3, establishing a fault determination matrix and forming a fault location criterion according to the fault section characteristics includes the following steps:
s3.1: performing matrix addition operation on the network description matrix D and the fault information matrix G to obtain a fault judgment matrix P, wherein off-diagonal elements of the fault judgment matrix P represent topological connection relations among nodes in the power distribution network, and diagonal elements of the off-diagonal elements represent whether fault overcurrent flows through the nodes in the power distribution network;
s3.2: and constructing a matrix algorithm fault positioning criterion according to the characteristics of different uploading fault information of the main node FTU and the sub node FTU of the fault section.
5. A method for locating faults in a photovoltaic-containing power distribution network as claimed in claim 3, wherein: in step S3.2, the conditions for constructing the fault locating criteria of the matrix algorithm are as follows:
s3.2.1: when a short circuit fault occurs in a double-end feeder line section formed by the main node i and the sub node j, if a single fault occurs in the power distribution network: if p ii =1, all p ij =1 i +.j, p jj =0 or-1; if multiple faults occur in the power distribution network: if p ii =0, all p ij =1 i +.j, p jj ＝-1；
S3.2.2: when a short circuit fault occurs in a terminal feeder line section formed by the main node i, if a single fault occurs in the power distribution network: if p ii =1, all p ij ＝1 i≠j。
6. The fault location method for a photovoltaic-containing power distribution network according to claim 5, wherein: in step S3.2, further including performing fault location of the photovoltaic-containing power distribution network according to a matrix algorithm, including:
s3.2.3: establishing a network description matrix D containing a photovoltaic power distribution network and a fault information matrix G, and adding the two matrixes to obtain a fault judgment matrix P;
s3.2.4: judging which nodes together form a T-joint section by searching non-diagonal elements in the fault judging matrix P line by line;
s3.2.5: for each T-joint section, obtaining fault information uploaded by FTU at a main node and two sub-nodes forming the T-joint section by searching diagonal elements in a fault judgment matrix P;
s3.2.6: comparing the fault information uploaded by the FTU at the main node of the T-joint section with the fault information uploaded by the FTU at the two sub-nodes respectively, and judging the state of the T-joint section twice according to a matrix algorithm fault positioning criterion;
s3.2.7: if the judging result of the two section states is consistent, the section state of the T-joint section can be directly obtained; if the fault information is inconsistent, judging the section state of the T-joint section according to the fault information uploaded by the FTU at the main node of the T-joint section;
s3.2.8: if the FTU uploading information at the main node of the T-joint section is 1, the T-joint section is a normal section; if the upload information is "0", the T-junction zone is a faulty zone.
7. The fault location method for a photovoltaic-containing power distribution network according to claim 6, wherein: in the step 3.2 of the process,
step S3.2.4 specifically includes: judging whether a T-joint section exists or not according to the number of off-diagonal elements with the value of 1 in the ith row of the fault judgment matrix P; the judgment principle is as follows: if the row has only one off-diagonal element p ij The section formed by the nodes corresponding to the row number i and the column number j is a non-T-joint section, i corresponds to the main node of the section, and j corresponds to the sub-node of the section; if there are two off-diagonal elements p in the row ij ＝p ik The section formed by the nodes corresponding to the row number i and the column number j and k is a T-joint section, i corresponds to the main node of the T-joint section, and j and k respectively correspond to the sub-nodes of the T-joint section;
in step S3.2.6: if the section formed by the main node and the sub node is a non-T-joint section, judging the state of the non-T-joint section once by using a matrix algorithm fault positioning criterion, namely the correct section state;
if the section formed by the main node and the sub node is a T-joint section, judging the state of the T-joint section twice by using a matrix algorithm fault positioning criterion; if the two judging results of the T-joint section state are consistent, the T-joint section state is the judging state; if not, according to the fault information p uploaded by the FTU at the main node of the T-joint section ii And judging the state of the T-joint section.
8. The fault location method for a photovoltaic-containing power distribution network according to claim 4, wherein: in step S4, a switching function suitable for fault location of the photovoltaic-containing power distribution network is established as follows:
s4.1: setting a switching function model suitable for fault location of the photovoltaic power distribution network;
s4.2: definition of the calculated value of the switching functionTotal number of feeder sections N in the upstream and downstream region of switch j 1 、N 2 The method comprises the steps of carrying out a first treatment on the surface of the Region upstream of switch jN of (v) 1 Status x of each feeder line section l (n 1 ) Nth in the upstream region of switch j 2 Status x of each feeder line section l (n 2 ) Normally "1", and failure "0"; power supply access coefficient K of switch j up and down stream 1 、K 2 ；
S4.3: when the upper and lower power supplies of the switch j are respectively and directly connected with the switch j, namely, the power supplies continuously supply power to the switch j, the value is 1, and when the upper and lower power supplies are respectively separated from a passage between the switch j by a fault point, the value is 0;
s4.4: define the number S of upstream and downstream of the switch j 1 、S 2 The method comprises the steps of carrying out a first treatment on the surface of the Status of switch j to feeder section experienced on its upstream power pathStatus of switch j to feeder section seen on its downstream power supply path +.>
9. The fault location method for a photovoltaic-containing power distribution network according to claim 5, wherein: in step S5, the matrix algorithm and the modified sine and cosine algorithm are combined to search the optimal solution, so as to realize accurate positioning of the fault section, which specifically includes the following steps:
s5.1: all feeder line sections obtained from the fault positioning result of the matrix algorithm are called as suspected fault sections, and the number of the suspected fault sections is determined;
s5.2: if the number of the suspected fault sections is only 1, the fact that the matrix algorithm fault positioning result is correct is indicated, and a fault positioning method based on an improved sine and cosine algorithm is not needed;
s5.3: if the number of the suspected fault sections is not less than 2, a true fault section is found out from the suspected fault sections by using a modified sine and cosine algorithm.
10. The fault location method for a photovoltaic-containing power distribution network according to claim 5, wherein: in step 5.3, the steps based on the modified sine and cosine algorithm are as follows:
s5.3.1: constructing an expected function of the suspected fault section and writing a fitness function;
s5.3.2: setting a population rule module, initializing all individual positions in the population by random 0 or 1, and setting iteration times and algorithm parameters;
s5.3.3: and calculating fitness values of all individuals in the initial population once according to the objective function, and recording the optimal individual positions.
S5.3.4: binary conversion is carried out on the sinusoidal algorithm, the position of the population is updated, each individual fitness value of the population is recalculated, the fitness value of the optimal position recorded last time is compared, and if the fitness value of the t+1st time is smaller than the fitness value of the t time, the optimal position and the fitness value of the population are replaced and used as the basis of the next update;
s5.3.5: judging whether an iteration termination condition is met, if so, outputting an optimal individual and a fitness value thereof in the population, wherein the position of the optimal individual is the actual running state of each section of the power distribution network, and if not, continuing to execute the step S5.3.4 until the maximum iteration times are reached;
s5.3.6: and determining a fault interval according to the individual position information, namely the running state of the power distribution network.
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| CN118395291B (en) * | 2024-06-27 | 2024-10-22 | 南京邮电大学 | Two-stage fault positioning method for active power distribution network online fault positioning |
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