CN115128395A - Voltage sag source positioning method and device - Google Patents

Abstract

The invention discloses a method and a device for positioning a voltage sag source, wherein the method comprises the following steps: constructing impedance matrixes of a plurality of network nodes on the electric network line, and setting a plurality of monitoring points based on the impedance matrixes; respectively extracting observable line sets of each monitoring point, and determining a first fault line set corresponding to the observable line of each monitoring point; judging whether a voltage sag source is positioned at the upstream or the downstream of a monitoring point according to the reactive change condition of the monitoring point, and determining a second fault line set corresponding to the voltage sag source; taking intersection of the first fault line set and the second fault line set, and determining a third fault line set corresponding to the voltage sag source; and determining the position of the voltage sag source by adopting a sparrow search algorithm according to the third fault line set. The technical scheme of the invention comprehensively utilizes multiple criteria of the observable domain of the monitoring point, the dip source direction and the like, eliminates the influence of non-fault points as much as possible, can effectively improve the fault positioning efficiency and improve the accuracy of the positioning result.

Description

A method and device for locating a voltage sag source

technical field

The invention relates to the technical field of power failures, in particular to a method and device for locating a voltage sag source.

Background technique

Voltage sag is a frequently encountered phenomenon in the power system. Voltage sag has become an important power quality problem, which has aroused the common concern of power companies and power users all over the world. The failure of the transmission system or distribution system in the utility grid is the main cause of voltage sags. Accurately locating the location of the sag fault source, on the one hand, helps both parties to distinguish sag responsibilities and coordinate disputes; on the other hand, it can greatly shorten the fault clearance time of the power company and improve the reliability of power supply. Most of the traditional voltage sag source location methods are based on the impedance at the monitoring point and the changes in the measured voltage, current, power and other information to determine the location of the fault is upstream or downstream of the monitoring point. Judgment of the specific location of the sag source.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, on the one hand, the present invention provides a method for locating a voltage sag source, including:

Construct impedance matrices of several network nodes on the power grid line according to the electrical parameters of the power grid, and set up several monitoring points on the power grid line based on the impedance matrix;

For each of the monitoring points, according to the monitoring point number after monitoring the voltage sag, extract the observable line set of each monitoring point, and take the intersection of the observable line sets between the monitoring points to determine the the first set of faulty lines corresponding to the observable lines of each monitoring point;

For each of the monitoring points, it is determined that the voltage sag source is located upstream or downstream of the monitoring point according to the reactive power change of the monitoring point, and the voltage sag source is extracted according to the judgment result of the orientation of the voltage sag source. The corresponding upstream line or downstream line on the power grid line, and taking the intersection of the fault lines of each monitoring point to determine the second fault line set corresponding to the voltage sag source;

Taking the intersection of the first faulty line set and the second faulty line set, and determining a third faulty line set corresponding to the voltage sag source;

Determine the monitoring point number corresponding to the voltage sag source according to the third fault line set, and take the minimum sum of the error value between the theoretical calculated value of the post-fault voltage corresponding to the monitoring point number and the actual observed value as the goal, and use the sparrow search method. An algorithm determines the location of the source of the voltage sag.

First, construct the impedance matrix of several network nodes on the power grid line according to the electrical parameters of the power grid, and set up several monitoring points on the power grid line based on the impedance matrix, including:

Establish a functional relationship between the fault distance on the power grid line and the monitoring point on the power grid line and the sag amplitude of the monitoring point, and the process is as follows:

If the system experiences a three-phase symmetrical short-circuit fault at node n, the voltage at node m can be given by the fault at node n:

表示节点m故障前的电压，ΔV_mn表示节点n故障引起节点m电压的变化量；in,

represents the voltage of node m before the failure, ΔV _mn represents the change of the voltage of node m caused by the failure of node n;

The three-phase voltage drop at node m caused by the failure of node n is:

表示节点n故障前的电压，Z_mn表示节点m与节点n之间的互阻抗，Z_nn表示节点n的自阻抗。where V _sag (m,n) represents the voltage sag of node m when the node fails,

represents the voltage at node n before the fault, Z _mn represents the mutual impedance between node m and node n, and Z _nn represents the self-impedance of node n.

In practice, the probability of failure at a node is very small. Most short-circuit faults occur along lines. The fault occurs at point p in the middle of the line, as shown in Figure 1. The fault occurs at position p along the line causing the voltage sag at node k to be calculated as follows:

The new impedance due to this fault location p will be calculated from node k.

Z _kp = (1-λ)×Z _km +λ×Z _kn

Z _pp =(1-λ) ² ×Z _mm +λ ² ×Z _nn +2λ(1-λ)×Z _mn +λ(1-λ)×z _mn

Among them, L _mn represents the distance between two connected nodes m and n in the network;

_Lmp represents the distance between node m and fault point p;

Z _kp represents the transmission impedance between node k and fault point p;

Z _pp represents the self-impedance of fault point p;

Z _mn represents the mutual impedance between node m and node n.

The voltage before the fault at point p is

By combining the above equations, the relationship between the voltage at node k and the fault distance can be solved. The above deduces the relationship between the voltage amplitude of each busbar in the system and the fault distance when a three-phase short-circuit fault occurs. The relationship between bus voltage amplitude and fault distance can still be derived.

Secondly, the critical fault points on each line of the monitoring points corresponding to different fault types are analyzed under the preset threshold. The process of solving the critical failure point is as follows:

When a short-circuit fault occurs in the system, the node voltage in the system will decrease accordingly. If the voltage of a certain node decreases to a predetermined threshold, it is regarded as a critical fault point. The position of the node can be obtained by combining the relational expressions of the distance between the previous node and the fault point.

f(λ)=U _sag (λ)-U _t =0

where U _t represents a preset voltage threshold. This formula can be solved iteratively using the New Zealand method.

where k represents the number of iterations, and f'(λ _k ) represents the derivative of f(λ _k ).

However, since f(λ _k ) is a relatively complex nonlinear function, the process of derivation of it will be difficult. In order to obtain faster convergence speed and more accurate results, a more optimal iterative algorithm is used here. The formula is:

When an asymmetric fault occurs in the system, the amplitudes of the three-phase voltages of the nodes are not the same. In this regard, this paper stipulates that when the voltage amplitude of any one of the three phases decreases to the threshold U _t , it means that a voltage transient occurs at this point. sag, that is, the smallest phase of the three-phase voltage amplitude is used as the basis for determining the voltage sag.

At this time, the expression of the equivalent amplitude of the voltage sag is:

U _sageq =min(U _sagA (λ),U _sagB (λ),U _sagC (λ))

From the above formula, the critical fault point of the node can be obtained when an asymmetric fault occurs.

Finally, on the basis of obtaining the critical fault points of the monitoring points on each line corresponding to different fault types, the observable matrix of each monitoring point is determined and the limited monitoring points are arranged reasonably and effectively.

The node MRA (Monitor Reach Area, MRA) is the observable area of the node, which refers to the fault area that can be monitored by a monitoring point when a short-circuit fault occurs in a line in the system that can cause a voltage sag at a monitoring point. The arrangement of voltage sag monitoring points must meet the observability of the whole network fault, which requires reasonable and effective configuration of limited monitoring points, so that their combined MRA can cover the whole network. The MRA matrix formed by the combination of each monitoring point can be expressed as:

In the formula, the total number of nodes in the system is represented by N, the total number of fault points in the system is represented by P, and the voltage of node i when the fault point j fails is represented by U _ij . When U _ij is lower than the set threshold U _t , M _(i,j) =1, which means that a voltage sag occurs at node i. When different types of short-circuit faults occur, the MRA of each monitoring point will also change, and the observable matrices M ⁽¹⁾ and M ^{( 1,1)} , M ⁽²⁾ , M ⁽³⁾ .

Assuming that there are N nodes in the network, an N-dimensional state variable x can be used to represent the setting of monitoring points in the network

If there is an important load node in the network, when the node must set the monitoring point, its corresponding element can always be set to 1 in the configuration process. The configuration of voltage sag monitoring points is optimized with the minimum total number of monitoring points. When a short-circuit fault occurs in the network, at least b monitoring points must have voltage sags. This application divides the monitoring point configuration model into two parts: objective function and constraint condition. The objective function is represented by minf(x), which is equal to the sum of the state quantities of all nodes. Constraints ensure that all short-circuit faults in the entire network can be observed.

Objective function:

Restrictions:

的故障点数，b₁、b₂、b₃、b₄分别对应不同故障类型所设定的最少能发生电压暂降的监测点个数。监测点的配置模型实际是一个整数 (0-1)线性规划的问题，可以使用MATLAB中的YALMIP工具箱对配置模型进行求解，从而得到电压暂降监测点的配置方案。确定监测点配置方案后，根据监测到暂降的监测点编号，分别提取各监测点的可观测线路集J_Lm，并取交集，最终得到根据监测点可观测线路提取出的第一故障线路集J_L。P ⁽¹⁾ , P ^{(1, 1)} , P ⁽²⁾ , P ⁽³⁾ in the formula correspond to the observable matrices respectively

The number of fault points, b ₁ , b ₂ , b ₃ , and b ₄ correspond to the minimum number of monitoring points that can cause voltage sags set by different fault types, respectively. The configuration model of monitoring points is actually an integer (0-1) linear programming problem. The configuration model can be solved by using the YALMIP toolbox in MATLAB to obtain the configuration scheme of voltage sag monitoring points. After the monitoring point configuration scheme is determined, according to the monitoring point number of the monitored sag, the observable line set J _Lm of each monitoring point is extracted respectively, and the intersection is taken, and finally the first fault line set extracted according to the observable lines of the monitoring point is obtained. J _L.

According to the reactive power change of the monitoring point, it is determined that the voltage sag source is located upstream or downstream of the monitoring point. downstream lines, and take the intersection of the fault lines at each monitoring point to determine the second set of fault lines corresponding to the voltage sag source, including:

According to the electrical parameter corresponding to each of the monitoring points on the power grid line, extract the upstream and downstream power grid lines corresponding to the monitoring point;

Each monitoring point in the grid line is analyzed (theoretical or simulation analysis), and the lines located upstream and downstream are extracted and stored. For monitoring point m, let its upstream line sequence be J _Vup-m , and its downstream line sequence be J _Vdown-m . Then, according to the change of reactive power at the monitoring point, determine whether the sag source is located upstream or downstream. Let the reactive power before the sag at the monitoring point m be Q _m , and the reactive power during the sag be Q _fm , it can be judged by the following formula.

Finally, for each monitoring point m, according to the judgment result of its sag source azimuth, extract its corresponding upstream or downstream line, and take the intersection of the possible lines of each monitoring point, and finally get the second line extracted according to the sag azimuth judgment. Fault line set J _V .

The monitoring point number corresponding to the voltage sag source is determined according to the third fault line set, and the sum of the error value between the theoretical calculated value and the actual observed value of the post-fault voltage corresponding to the monitoring point number is the minimum, and the The sparrow search algorithm determines the location of the voltage sag source, including:

After determining the monitoring point number corresponding to the voltage sag source according to the third fault line set, using the sparrow search algorithm to determine the position of the voltage sag source includes the following steps:

First, set the optimization variables as follows, taking the fault occurrence branch l (discrete type), the relative distance λ from the fault point to the first section of the fault branch (continuous type) and the transition resistance R _f (continuous type) as the optimization variables;

Secondly, the goal is to minimize the sum of the error value between the theoretical calculated value of the post-fault voltage at the monitoring point and the actual observed value, specifically:

Among them, Δu _m (l,λ, R _f ) is the voltage error value at the mth monitoring point on the faulty branch l, when the relative distance from the branch head end is λ and the transition resistance is R _f ; M is the monitoring point number of points.

In another aspect, the present application provides a voltage sag source locating device, comprising:

a power grid network construction module, configured to construct impedance matrices of several network nodes on the power grid line according to the electrical parameters of the power grid, and set several monitoring points on the power grid line based on the impedance matrix;

The first fault line set determination module is used for each of the monitoring points, according to the monitoring point number after monitoring the voltage sag, to extract the observable line set of each monitoring point respectively, and to analyze the difference between the monitoring points. Take the intersection of the observable line sets, and determine the first fault line set corresponding to the observable lines of each monitoring point;

The second fault line set determination module is configured to, for each of the monitoring points, determine that the voltage sag source is located upstream or downstream of the monitoring point according to the reactive power change of the monitoring point, and determine the azimuth of the voltage sag source according to the monitoring point. As a result, the upstream line or downstream line corresponding to the voltage sag source on the power grid line is extracted, and the intersection of the fault lines at each monitoring point is taken to determine the second fault line set corresponding to the voltage sag source;

A third fault line set determination module, configured to take an intersection of the first fault line set and the second fault line set, and determine a third fault line set corresponding to the voltage sag source;

A voltage sag source determination module, configured to determine the monitoring point number corresponding to the voltage sag source according to the third fault line set, and use the error value between the theoretical calculated value and the actual observed value of the post-fault voltage corresponding to the monitoring point number The sum of the minimum is the target, and the sparrow search algorithm is used to determine the location of the voltage sag source.

On the other hand, an embodiment of the present invention also provides an electronic device, the electronic device includes a processor, a memory, and a computer program stored on the memory and capable of running on the processor, the computer program being The processor implements the steps of the method for locating a voltage sag source when executed.

The technical scheme of the present invention constructs impedance matrices of several network nodes on the power grid line according to the electrical parameters of the power grid, and sets up several monitoring points on the power grid line based on the impedance matrix; After the number of the monitoring points, the observable line sets of each monitoring point are extracted respectively, and the intersection of the observable line sets between the monitoring points is obtained, and the first fault line set corresponding to the observable lines of each monitoring point is determined. ; For each of the monitoring points, determine that the voltage sag source is located upstream or downstream of the monitoring point according to the reactive power change situation of the monitoring point, and extract the voltage sag source on the power grid line according to the judgment result of the voltage sag source orientation. Corresponding upstream line or downstream line, and taking the intersection of fault lines at each monitoring point to determine the second fault line set corresponding to the voltage sag source; taking the intersection of the first fault line set and the second fault line set, and determining the The third fault line set corresponding to the voltage sag source; the monitoring point number corresponding to the voltage sag source is determined according to the third fault line set, and the error value between the theoretical calculated value and the actual observed value of the post-fault voltage corresponding to the monitoring point number is determined. The minimum sum is the goal, and the sparrow search algorithm is used to determine the location of the voltage sag source. The technical scheme of the present invention comprehensively utilizes multiple criteria such as the observable area of the monitoring point and the azimuth of the sag source, and eliminates the influence of non-fault points as much as possible, which can effectively improve the efficiency of fault location and the accuracy of the location result.

Description of drawings

1 is a flowchart of steps of a method for locating a voltage sag source according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a power grid line fault distance definition provided by an embodiment of the present invention;

3 is a schematic diagram of the configuration of a power grid monitoring point according to an embodiment of the present invention;

4 is a flowchart of a method for locating a voltage sag source;

FIG. 5 is a flowchart of a method for accurately locating a fault point according to an embodiment of the present invention;

Detailed ways

Since grid fault is the main cause of sag, the location of sag source is mostly the location of grid fault point. At this time, various methods that can realize grid fault location can also be used for sag fault source positioning. The methods of power grid fault location can be roughly divided into two categories: one is the wide-area fault section location that widely uses multiple line terminals or fault indicators, which is suitable for regional power grids with a high level of automation; the other is the use of a small number of feeders. The fault location method, which calculates the fault distance from the exported electrical quantity information, is suitable for power grids with low automation level. Since the power quality monitoring point is a limited node in the power grid, the location of the voltage sag fault source needs to adopt the ranging method. Such methods mainly include traveling wave method, impedance method, method based on power flow calculation, method based on fault distance distribution function, and intelligent algorithm based on data processing. The traveling wave method requires the installation of an expensive and precise measuring device, and the cost is high, and its accuracy will be disturbed when the network structure is complex. The impedance method is simple in principle and low in investment, but is easily affected by line impedance, load and power supply parameters. The method based on power flow calculation needs to estimate the power flow, fault resistance, load power, etc. before the fault, and the accuracy of the estimation will affect the accuracy of the positioning result. The location method based on the distribution function of the fault distance generally finds the fault section by fitting methods such as the least squares method and pattern recognition, but the fitting method generally has a large error with the actual fault distance. Intelligent algorithms based on data processing require a large amount of actual fault information to train algorithm rules, but the data available for learning and training are limited in practice. Therefore, there is an urgent need for a sag fault location method that can meet the requirements of location accuracy and has lower requirements for monitoring node configuration, improve the practicability and robustness of location theory research, and assist in the operation and maintenance of faults in practical engineering.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

FIG. 1 is a flowchart of steps of a method for locating a voltage sag source provided by an embodiment of the present invention, and the method includes the following steps:

Step 101: Construct impedance matrices of several network nodes on the power grid line according to electrical parameters of the power grid, and set up several monitoring points on the power grid line based on the impedance matrix;

Based on the IEEE33 node distribution network model parameters, the network node impedance matrix is formed, and the voltage of the monitoring point at the time of each node fault is calculated through the voltage sag matrix. Then, according to the relationship between the monitoring point voltage and the set threshold value, it is judged whether the fault point is observable. , form a node depression matrix, and then optimize the monitoring point configuration scheme. The configuration model of monitoring points is actually an integer (0-1) linear programming problem. The configuration model can be solved by using the YALMIP toolbox in MATLAB to obtain the configuration scheme of voltage sag monitoring points.

Step 102: For each of the monitoring points, according to the monitoring point number after monitoring the voltage sag, extract the observable line set of each monitoring point respectively, and obtain the intersection of the observable line sets between the monitoring points. , determining the first fault line set corresponding to the observable lines of each monitoring point;

After the monitoring point configuration scheme is determined, according to the monitoring point number of the monitored sag, the observable line set J _Lm of each monitoring point is extracted respectively, and the intersection is taken, and finally the first fault line set extracted according to the observable lines of the monitoring point is obtained. J _L.

Step 103: For each of the monitoring points, determine that the voltage sag source is located upstream or downstream of the monitoring point according to the reactive power change of the monitoring point, and extract the voltage sag source according to the determination result of the orientation of the voltage sag source. The drop source is on the corresponding upstream line or downstream line on the power grid line, and the intersection of the fault lines at each of the monitoring points is taken to determine the second fault line set J _L corresponding to the voltage sag source;

Step 2: Build a standard IEEE33 node distribution network simulation model based on MATLAB-SIMULINK. FIG. 2 is a schematic diagram of a power grid line fault distance definition provided by an embodiment of the present invention, and FIG. 3 is a power grid monitoring point provided by an embodiment of the present invention. The configuration diagram of the embodiment of the present invention configures monitoring points at a total of 6 nodes No. 1, No. 2, No. 5, No. 19, No. 23, and No. 26. For each monitoring point, determine whether the sag source is located upstream or downstream of the monitoring point according to its reactive power change, and take the intersection of the possible lines of each monitoring point, so as to obtain the second fault line set extracted according to the sag azimuth judgment. J _V ;

Step 104, taking the intersection of the first faulty line set and the second faulty line set, and determining a third faulty line set corresponding to the voltage sag source;

Step 3: In order to eliminate the influence of non-fault points as much as possible, a sag fault source location method based on multiple criteria is proposed by combining the observable domain of monitoring points with the upstream and downstream location methods of voltage sag sources, flow chart As shown in Figure 4. Take the intersection of the first faulty line set _JL obtained in step 1 and the second faulty line set JV obtained in step 2, and finally obtain the third _faulty line set J that needs to be investigated;

Step 105: Determine the monitoring point number corresponding to the voltage sag source according to the third fault line set, with the goal of minimizing the sum of the error value between the theoretical calculated value of the post-fault voltage and the actual observed value corresponding to the monitoring point number, The location of the voltage sag source is determined using a sparrow search algorithm.

Based on the third fault line set J, the preliminary position of the fault source can be obtained. After determining the monitoring point number corresponding to the voltage sag source, the improved sparrow search algorithm is used to further solve the precise location of the fault source. The method flow of the precise location of the fault point is shown in FIG. Using the sparrow search algorithm to determine the location of the voltage sag source includes the following steps:

First, set the optimization variables as follows, taking the fault occurrence branch l (discrete type), the relative distance λ from the fault point to the first section of the fault branch (continuous type) and the transition resistance R _f (continuous type) as the optimization variables;

Secondly, the goal is to minimize the sum of the error value between the theoretical calculated value of the post-fault voltage at the monitoring point and the actual observed value, specifically:

Among them, Δu _m (l,λ, R _f ) is the voltage error value at the mth monitoring point on the faulty branch l, when the relative distance from the branch head end is λ and the transition resistance is R _f ; M is the monitoring point number of points.

Since this method is greatly affected by network parameters, when the network scale is large, in order to reduce the influence of inaccurate network parameters on the results, the weight can be calculated according to the amplitude of the lowest phase of the three-phase voltage at each monitoring point. Low, the greater the weight, which is equivalent to the lower the voltage of the monitoring point, the greater the attached weight, to amplify the voltage of the monitoring point closer to the fault point as much as possible, while reducing the monitoring point farther away from the fault point. interference with positioning results. When the network scale is small, the weight of each monitoring point can take 1.

In this case, rewrite the expression as

In the formula, w is the weight, which can be adjusted according to the actual situation, and its value ranges from 0 to 1.

Constraints are

In the formula, R _lim is the upper limit of the transition resistance, which is set to 100Ω in the present invention.

For the above hybrid optimization problem, the improved sparrow search algorithm (MSSSA) is used to solve the problem, and the exact location of the fault source can be known by solving the value of λ.

The Improved Sparrow Search Algorithm (MSSSA) is improved on the basis of the Sparrow Search Algorithm (SSA). It uses the Circle map to initialize the individual positions of sparrows, which increases the diversity of the initial population. Combined with the butterfly flight mode in the butterfly optimization algorithm (BOA), the position update strategy of the finder is improved, and the global exploration ability of the algorithm is enhanced. Therefore, compared with the Sparrow Search Algorithm (SSA), it has better convergence and solution accuracy, and the global optimization ability is greatly improved.

选取每次迭代中位置最好的一部分麻雀作为发现者，一般占到种群的10％～20％，剩下的作为加入者，而侦察者则在整个种群中随机选取10％～20％。The principle of the sparrow search algorithm is as follows: Assuming that there are N sparrows in the D-dimensional solution space, the position of the i-th sparrow in the D-dimensional solution space is X _i =[x _i1 ,x _i2 ,...,x _id ], and its fitness value is

A part of the sparrows with the best position in each iteration is selected as the discoverer, which generally accounts for 10% to 20% of the population, and the rest are selected as joiners, while the scout randomly selects 10% to 20% of the entire population.

The finder's location update formula is as follows:

表示第i个麻雀在第j维的位置，α∈(0,1)是一个随机数，

为预警值，

为安全值，Q是服从正态分布的随机数，L为1×d且元素值全为1的矩阵。当R₂＜ST时，表示周围没有天敌，发现者将进行广泛搜索。反之，则代表发现捕食者，此时所有麻雀都要飞往其他安全地方觅食。Among them, t represents the current iteration number, and j=1,2,...,d. iter _max represents the maximum number of iterations,

represents the position of the i-th sparrow in the j-th dimension, α∈(0,1) is a random number,

is the warning value,

is a safe value, Q is a random number that obeys a normal distribution, and L is a 1×d matrix with all 1s. When R ₂ <ST, it means that there are no natural enemies around, and the finder will conduct extensive searches. On the contrary, it means that a predator is found, and all sparrows must fly to other safe places to feed.

The update formula of the joiner's position is as follows:

表示第t+1次迭代发现者最优位置，A为1×d且元素随机赋值值为1或-1的矩阵，且A⁺＝A^T(AA^T)^-1。当 i＞N/2时，位置较差的加入者处于十分饥饿的状态，此时需要飞往其他的地方觅食。Among them, X _worst represents the global worst position in the t-th iteration,

Represents the optimal position of the finder in the t+1th iteration, A is a 1×d matrix with elements randomly assigned values of 1 or -1, and A ⁺ = ^AT (AA ^T ) ^-1 . When i>N/2, the participants with poor positions are in a very hungry state and need to fly to other places for food.

The scout position update formula is as follows:

为当前全局最优位置，β为步长控制参数，是一个均值为0，方差为1的正态分布随机数。

是一个随机数，f_i表示个体适应度值，f_g为最佳适应度值，f_ω为最差适应度值，ε为最小常数，防止分母为零的情况出现。in,

is the current global optimal position, and β is the step size control parameter, which is a normally distributed random number with a mean of 0 and a variance of 1.

is a random number, f _i represents the individual fitness value, f _g is the best fitness value, f _ω is the worst fitness value, and ε is the minimum constant to prevent the denominator from being zero.

The sparrow population is initialized using the Circle chaotic map, and its expression is as follows:

where i is the dimension.

The location update strategy in the global search phase of BOA is introduced to improve the location update formula of the finder in SSA. The improved location update method is as follows:

In the improved position update formula, on the one hand, in each iteration, the sparrow individual will communicate with the optimal individual, so as to make full use of the information of the current optimal solution and improve the defect of lack of information exchange between individuals in the original algorithm; On the other hand, the introduction of BOA expands the search space to a certain extent.

FIG. 4 shows a flowchart of a method for locating a voltage sag source provided by an embodiment of the present invention. A possible fault line set of the voltage sag source, that is, the first fault line set J _L , is extracted according to the observable lines at the monitoring point, Judging and extracting the possible faulty line set of the voltage sag source according to the sag azimuth, that is, the second faulty line set J _V , and taking the intersection of the first fault line set J _L and the second fault line set J _V to obtain the voltage sag source The set of possible faulty lines J (the third set of faulty lines). The method proposed in the invention can comprehensively utilize multiple criteria such as the observable area of monitoring points, sag source orientation, fault type, etc., to eliminate the influence of non-fault points as much as possible, and effectively improve the efficiency of fault location and the accuracy of location results. Firstly, the set of possible faulty lines J _L extracted from the observable lines of the monitoring point is obtained through the analysis of the observable domain of the monitoring point, and the set of possible faulty lines J _V extracted by judging the upstream and downstream directions of the sag source is taken as the sum of J _L and J _V . The intersection yields the set J of possible faulty lines. In addition, an improved sparrow search algorithm (MSSSA) is used to find the exact location of the fault source, which avoids the cyclic traversal process of possible fault points. It uses the Circle map to initialize the individual positions of sparrows, which increases the diversity of the initial population. Combined with the butterfly flight mode in the butterfly optimization algorithm (BOA), the position update strategy of the finder is improved, and the global exploration ability of the algorithm is enhanced. Therefore, compared with the Sparrow Search Algorithm (SSA), it has better convergence and solution accuracy, and the global optimization ability is greatly improved. Compared with other algorithms, it has the characteristics of high search accuracy and strong robustness.

In another aspect, the present application provides a voltage sag source locating device, comprising:

a power grid network construction module, configured to construct impedance matrices of several network nodes on the power grid line according to the electrical parameters of the power grid, and set several monitoring points on the power grid line based on the impedance matrix;

The first fault line set determination module is used for each of the monitoring points, according to the monitoring point number after monitoring the voltage sag, to extract the observable line set of each monitoring point respectively, and to analyze the difference between the monitoring points. Take the intersection of the observable line sets, and determine the first fault line set corresponding to the observable lines of each monitoring point;

The second fault line set determination module is configured to, for each of the monitoring points, determine that the voltage sag source is located upstream or downstream of the monitoring point according to the reactive power change of the monitoring point, and determine the azimuth of the voltage sag source according to the monitoring point. As a result, the upstream line or downstream line corresponding to the voltage sag source on the power grid line is extracted, and the intersection of the fault lines at each monitoring point is taken to determine the second fault line set corresponding to the voltage sag source;

A third fault line set determination module, configured to take an intersection of the first fault line set and the second fault line set, and determine a third fault line set corresponding to the voltage sag source;

A voltage sag source determination module, configured to determine the monitoring point number corresponding to the voltage sag source according to the third fault line set, and use the error value between the theoretical calculated value and the actual observed value of the post-fault voltage corresponding to the monitoring point number The sum of the minimum is the target, and the sparrow search algorithm is used to determine the location of the voltage sag source.

The voltage sag source locating device provided by the embodiment of the present invention can comprehensively utilize multiple criteria such as the observable area of the monitoring point, the sag source orientation, and the fault type, eliminate the influence of non-fault points as much as possible, and effectively improve the efficiency of fault locating and the The accuracy of the positioning results.

On the other hand, an embodiment of the present invention also provides an electronic device, the electronic device includes a processor, a memory, and a computer program stored on the memory and capable of running on the processor, the computer program being The processor implements the steps of the method for locating a voltage sag source when executed.

Although preferred embodiments of the embodiments of the present invention have been described, additional changes and modifications to these embodiments may be made by those skilled in the art once the basic inventive concepts are known. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications that fall within the scope of the embodiments of the present invention.

Finally, it should also be noted that in this document, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply these entities or that there is any such actual relationship or sequence between operations. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article or terminal device comprising a list of elements includes not only those elements, but also a non-exclusive list of elements. other elements, or also include elements inherent to such a process, method, article or terminal equipment. Without further limitation, an element defined by the phrase "comprises a..." does not preclude the presence of additional identical elements in the process, method, article or terminal device comprising said element.

A method for locating a voltage sag source and a device for locating a voltage sag source provided by the present invention have been described above in detail. In this paper, specific examples are used to illustrate the principles and implementations of the present invention. The description is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation and application scope. However, the contents of this specification should not be construed as limiting the present invention.

Claims (8)

1. A method for locating a voltage sag source, comprising:

constructing impedance matrixes of a plurality of network nodes on a power grid line according to electrical parameters of a power grid, and setting a plurality of monitoring points on the power grid line based on the impedance matrixes;

for each monitoring point, respectively extracting an observable line set of each monitoring point according to the number of the monitoring point after voltage sag is monitored, taking an intersection of the observable line sets among the monitoring points, and determining a first fault line set corresponding to the observable line of each monitoring point;

for each monitoring point, judging whether a voltage sag source is positioned at the upstream or the downstream of the monitoring point according to the reactive power change condition of the monitoring point, extracting corresponding upstream lines or downstream lines of the voltage sag source on a power grid line according to the judgment result of the position of the voltage sag source, taking intersection of fault lines of the monitoring points, and determining a second fault line set corresponding to the voltage sag source;

taking an intersection of the first fault line set and the second fault line set, and determining a third fault line set corresponding to the voltage sag source;

and determining a monitoring point number corresponding to the voltage sag source according to the third fault line set, and determining the position of the voltage sag source by adopting a sparrow search algorithm by taking the minimum sum of the error values of the theoretical calculated value of the voltage after the fault corresponding to the monitoring point number and the actual observed value as a target.

2. The method according to claim 1, wherein the step of constructing an impedance matrix of a plurality of network nodes on the grid line according to the electrical parameters of the grid and setting a plurality of monitoring points on the grid line based on the impedance matrix comprises:

establishing a functional relation between the fault distance between the fault point on the power grid line and the monitoring point on the power grid line and the sag amplitude of the monitoring point, wherein the process is as follows:

if the system has a three-phase symmetric short-circuit fault at node n, the voltage at node m may be given by the fault occurring at node n:

wherein,

representing the voltage before failure, Δ V, of node m _mn Representing the amount of change in the voltage at node m due to a fault at node n;

the condition that the three-phase voltage at the node m is reduced due to the fault of the node n is as follows:

wherein, V _sag (m, n) represents the voltage sag of node m at the time of node failure,

representing the voltage before failure of node n, Z _mn Representing the mutual impedance between node m and node n, Z _nn Representing the self-impedance of node n.

3. The method of claim 2, comprising:

when a fault point on the grid line is located at a point p between the node m and the node n, the voltage sag of the node k caused by the fault point p on the grid is calculated as follows:

the new impedance generated by fault location p is calculated from node k,

Z _kp ＝(1-λ)×Z _km +λ×Z _kn

Z _pp ＝(1-λ) ² ×Z _mm +λ ² ×Z _nn +2λ(1-λ)×Z _mn +λ(1-λ)×z _mn

wherein L is _mn Representing the distance between two associated nodes m and n in the network;

L _mp represents the distance between node m and the point of failure p;

Z _kp represents the transmission impedance between node k and fault point p;

Z _pp represents the self-impedance of the fault point p;

Z _mn representing the mutual impedance between node m and node n.

The voltage before p-point failure is

The relationship between the voltage at the node k and the fault distance can be solved by the simultaneous expression.

4. The method according to claim 1, wherein the step of constructing an impedance matrix of a plurality of network nodes on the grid line according to the electrical parameters of the grid and setting a plurality of monitoring points on the grid line based on the impedance matrix comprises:

the matrix formed by the monitoring points is as follows:

wherein, the total number of nodes on the power grid line is represented by N, the total number of fault points of the power grid is represented by P, and the voltage of the node i when the fault point j has a fault is represented by U _ij Indicates when U is _ij Below a set threshold U _t Time M _(i,j) 1 indicates that a voltage sag has occurred at node i.

5. The method according to claim 1, wherein for each monitoring point, determining whether the voltage sag source is located upstream or downstream of the monitoring point according to the reactive change condition of the monitoring point, extracting corresponding upstream or downstream lines of the voltage sag source on the power grid line according to the determination result of the voltage sag source position, and determining a second fault line set corresponding to the voltage sag source by taking an intersection of fault lines of each monitoring point, includes:

extracting upstream and downstream power grid lines corresponding to the monitoring points according to the electrical parameters corresponding to each monitoring point on the power grid lines;

for theMonitoring point m, with its upstream line sequence J _Vup-m And the downstream line sequence is J _Vdown-m Before the temporary drop of the monitoring point m occurs, the idle work is Q _m The idle work in the temporary reduction process is Q _fm According to the reactive change condition of the monitoring point m, the voltage sag source is judged to be positioned at the upstream or the downstream of the monitoring point m,

and for each monitoring point, extracting corresponding upstream or downstream lines according to the judgment result of the voltage sag source position, and determining a second fault line set corresponding to the voltage sag source by taking intersection of possible lines of each monitoring point.

6. The method for positioning the voltage sag source according to claim 1, wherein the determining, according to the third faulty line set, a monitoring point number corresponding to the voltage sag source, and determining, by using a sparrow search algorithm, a position of the voltage sag source with a target of a minimum sum of error values between theoretical calculated values of post-fault voltages and actual observed values corresponding to the monitoring point number, comprises:

after the monitoring point number corresponding to the voltage sag source is determined according to the third fault line set, the step of determining the position of the voltage sag source by adopting a sparrow search algorithm comprises the following steps:

firstly, the optimization variables are set as follows, namely a fault occurrence branch l (discrete type), a relative distance lambda (continuous type) between a fault point and a first section of the fault branch and a transition resistance R _f (continuous type) as an optimization variable;

secondly, the sum of the error value of the theoretical calculation value of the voltage after the fault at the monitoring point and the actual observation value is minimum as a target, specifically

Wherein, Δ u _m (l,λ,R _f ) The relative distance between the upper part of the fault branch and the head end of the fault branch is lambda, and the transition resistance is R _f The voltage error value at the mth monitoring point; m is the number of monitoring points.

7. A voltage sag source positioning device, comprising:

the power grid network construction module is used for constructing impedance matrixes of a plurality of network nodes on a power grid line according to electrical parameters of a power grid, and setting a plurality of monitoring points on the power grid line based on the impedance matrixes;

the first fault line set determining module is used for respectively extracting observable line sets of the monitoring points according to the monitoring point numbers after the voltage sag is monitored for the monitoring points, taking intersection sets of the observable line sets among the monitoring points, and determining a first fault line set corresponding to the observable line sets of the monitoring points;

the second fault line set determining module is used for judging whether a voltage sag source is positioned at the upstream or the downstream of each monitoring point according to the reactive power change condition of the monitoring point, extracting the corresponding upstream line or the downstream line of the voltage sag source on the power grid line according to the judgment result of the position of the voltage sag source, taking the intersection of the fault lines of each monitoring point and determining a second fault line set corresponding to the voltage sag source;

a third faulty line set determining module, configured to take an intersection of the first faulty line set and the second faulty line set, and determine a third faulty line set corresponding to the voltage sag source;

and the voltage sag source determining module is used for determining a monitoring point number corresponding to the voltage sag source according to the third fault line set, and determining the position of the voltage sag source by adopting a sparrow searching algorithm by taking the minimum sum of the error value of the theoretical calculated value of the voltage after the fault corresponding to the monitoring point number and the actual observed value as a target.

8. An electronic device comprising a processor, a memory, and a program or instructions stored on the memory and executable on the processor, the program or instructions when executed by the processor implementing the steps of the method of any of claims 1-6.

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