Voltage sag source location method and system based on positive sequence sag disturbance reactive power

Abstract

The present invention discloses a voltage sag source positioning method and system based on positive sequence sag disturbance reactive power. The voltage sag source positioning method comprises the following steps: S10: acquiring three-phase voltage and three-phase current data of each monitoring point; S20: calculating the positive sequence sag disturbance reactive power, and determining the sag line according to its polarity; S30: establishing a voltage sag precise positioning model; S40: solving the voltage sag precise positioning model by improving the whale optimization algorithm, and accurately determining the voltage sag source position. The voltage sag source positioning method is less constrained by the power grid structure, load model and measurement accuracy, has high positioning accuracy and small calculation amount.

Description

Technical Field

[0001] The present invention relates to the field of voltage sag source positioning, and in particular to a voltage sag source positioning method and system based on positive sequence sag disturbance reactive power. Background Art

[0002] With the development of economy and the progress of science and technology, more and more nonlinear loads and impact loads are connected to the power grid, causing serious power quality problems, affecting the safe production of all walks of life and the normal life of the people. According to surveys, voltage sag has become one of the most serious power quality problems. In order to reduce economic losses and quickly control voltage sag problems, the location of the voltage sag source must be accurately located first.

[0003] Some of the existing voltage sag positioning methods can only perform upstream and downstream positioning relative to the monitoring point, and the range is large; some methods use intelligent algorithms to solve the positioning model, but they need to process the data of all nodes in the entire network, which requires a large amount of calculation; in addition, the existing methods are greatly constrained by measurement accuracy, power grid structure, and load model, which in turn affects the accuracy of positioning. Summary of the invention

[0004] In response to the problems and needs raised above, this solution proposes a method and system for locating the source of voltage sag based on the reactive power of positive-sequence sag disturbance. Due to the adoption of the following technical features, the above technical objectives can be achieved and many other technical effects can be brought about.

[0005] An object of the present invention is to provide a method for locating a voltage sag source based on a positive sequence sag disturbance reactive power, comprising the following steps:

[0006] S10: Acquire three-phase voltage and three-phase current data of each monitoring point;

[0007] S20: Calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity;

[0008] S30: Establishing a voltage sag accurate positioning model;

[0009] S40: The voltage sag precise positioning model is solved by improving the whale optimization algorithm to accurately determine the location of the voltage sag source.

[0010] In addition, the voltage sag source locating method based on positive sequence sag disturbance reactive power according to the present invention may also have the following technical features:

[0011] In an example of the present invention, in step S20, calculating the positive sequence sag disturbance reactive power includes:

[0012] S21: Decompose the power system into a normal operating state network under the action of system power only and a sag component fault network under the action of sag disturbance voltage only by using the superposition principle, and calculate the three-phase sag disturbance voltage and current at the monitoring point according to the three-phase voltage and current data measured at the monitoring point;

[0013] S22: Decompose the positive-sequence sag component fault network from the sag component fault network by using the symmetrical component method, and calculate the three-phase positive-sequence sag disturbance voltage and current at the monitoring point;

[0014] S23: Calculate the positive sequence sag disturbance reactive power at the monitoring point. The calculation formula is as follows:

[0015]

[0016] In the formula, Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc They are the three-phase positive-sequence temporary drop disturbance current at the monitoring point respectively.

[0017] In an example of the present invention, in step S20, determining the temporarily-sagging line according to its polarity comprises the following steps:

[0018] The upstream and downstream relationship of the voltage sag source relative to the monitoring point is determined according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point;

[0019] By analyzing the distribution of each monitoring point in the power system, the voltage sag line can be determined.

[0020] In one example of the present invention, the objective function of the voltage sag precise positioning model is determined to be as follows:

[0021]

[0022] In the formula, ||||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistor.

[0023] In one example of the present invention, the constraint condition of the objective function is:

[0024]

[0025] In the formula, R fmax is the maximum value of the positive sequence transition resistance.

[0026] In one example of the present invention, the improved whale optimization algorithm includes an improvement on the spiral update position, and the formula of the improved spiral update position is as follows:

[0027]

[0028] In the formula, iter is the current iteration number, iter max is the maximum number of iterations, X * (iter) is the current global optimal whale position, X(iter) is the current whale position, X(iter+1) is the updated whale position, b is the spiral shape parameter, and l is a random number between [-1,1].

[0029] Another object of the present invention is to provide a voltage sag source location system based on positive sequence sag disturbance reactive power, comprising:

[0030] A data acquisition module configured to obtain three-phase voltage and three-phase current data of each monitoring point;

[0031] A power calculation module configured to calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity;

[0032] A model building module is configured to build a voltage sag accurate positioning model;

[0033] The position calculation module is configured to solve the voltage sag precise positioning model by improving the whale optimization algorithm to accurately determine the location of the voltage sag source.

[0034] In one example of the present invention, the power calculation module includes:

[0035] The first disturbance calculation unit is configured to use the superposition principle to decompose the power system into a normal operating state network only under the action of the system power supply and a sag component fault network only under the action of the sag disturbance voltage, and calculate the three-phase sag disturbance voltage and current at the monitoring point according to the three-phase voltage and current data measured at the monitoring point;

[0036] A second disturbance calculation unit is configured to decompose a positive-sequence sag component fault network from a sag component fault network by using a symmetrical component method, and calculate a three-phase positive-sequence sag disturbance voltage and current at a monitoring point;

[0037] The disturbance reactive power calculation unit is configured to calculate the positive sequence sag disturbance reactive power at the monitoring point, and the calculation formula is as follows:

[0038]

[0039] In the formula, Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc They are the three-phase positive-sequence temporary drop disturbance current at the monitoring point respectively.

[0040] In one example of the present invention, the power calculation module further includes:

[0041] A voltage sag source position determination unit is configured to determine the upstream and downstream relationship of the voltage sag source relative to the monitoring point according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point;

[0042] The voltage sag line determination unit is configured to determine the voltage sag line by analyzing the distribution positions of the monitoring points in the power system.

[0043] In one example of the present invention, the model building module includes:

[0044] The objective function unit is configured to minimize the sum of the difference spectral norms between the calculated value of the positive sequence sag disturbance reactive power at the monitoring point and the actual measured value, and determine the objective function of the voltage sag precise positioning model as follows:

[0045]

[0046] In the formula, ||||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistor.

[0047] The best embodiment for carrying out the present invention will be described in more detail below with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings of the embodiments of the present invention, wherein the drawings are only used to illustrate some embodiments of the present invention, but not to limit all embodiments of the present invention thereto.

[0049] Figure 1It is a flow chart of a method for locating a voltage sag source based on positive sequence sag disturbance reactive power according to an embodiment of the present invention;

[0050] Figure 2 4 is a circuit diagram of a positive sequence sag component fault network according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the technical solution of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described in conjunction with the drawings of specific embodiments of the present invention. The same figure marks in the drawings represent the same parts. It should be noted that the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons of ordinary skill in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not necessarily indicate a quantity limitation. Words such as "include" or "comprise" mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Words such as "connect" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0053] According to a first aspect of the present invention, a method for locating a voltage sag source based on positive sequence sag disturbance reactive power is provided. Figure 1 As shown, the following steps are included:

[0054] S10: Acquire three-phase voltage and three-phase current data of each monitoring point;

[0055] S20: Calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity;

[0056] S30: Establishing a voltage sag accurate positioning model;

[0057] S40: The voltage sag precise positioning model is solved by improving the whale optimization algorithm to accurately determine the location of the voltage sag source.

[0058] In an example of the present invention, in step S20, calculating the positive sequence sag disturbance reactive power includes:

[0059] S21: Decompose the power system into a normal operating state network under the action of system power only and a sag component fault network under the action of sag disturbance voltage only by using the superposition principle, and calculate the three-phase sag disturbance voltage and current at the monitoring point according to the three-phase voltage and current data measured at the monitoring point;

[0060] S22: Decompose the positive-sequence sag component fault network from the sag component fault network using the symmetrical component method, and calculate the three-phase positive-sequence sag disturbance voltage and current at the monitoring point; Figure 2 As shown, Z s1 , Z s2 are the equivalent internal impedance of each phase on the power supply side and the load side, Z L1 , Z L2 are the impedance of each phase line between the sag source f and the monitoring points M1 and M2, Δu fa , Δu fb , Δu fc It is the three-phase positive-sequence temporary sag disturbance voltage at the temporary sag point.

[0061] S23: Calculate the positive sequence sag disturbance reactive power at the monitoring point. The calculation formula is as follows:

[0062]

[0063] In the formula, Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc They are the three-phase positive-sequence temporary drop disturbance current at the monitoring point respectively.

[0064] In an example of the present invention, in step S20, determining the temporarily-sagging line according to its polarity comprises the following steps:

[0065] The upstream and downstream relationship of the voltage sag source relative to the monitoring point is determined according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point;

[0066] By analyzing the distribution of each monitoring point in the power system, the voltage sag line can be determined.

[0067] In one example of the present invention, the objective function of the voltage sag precise positioning model is determined to be as follows:

[0068]

[0069] In the formula, ||||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistor.

[0070] In one example of the present invention, the constraint condition of the objective function is:

[0071]

[0072] In the formula, R fmax is the maximum value of the positive sequence transition resistance.

[0073] In one example of the present invention, the improved whale optimization algorithm includes an improvement on the spiral update position, and the formula of the improved spiral update position is as follows:

[0074]

[0075] In the formula, iter is the current iteration number, iter max is the maximum number of iterations, X * (iter) is the current global optimal whale position, X(iter) is the current whale position, X(iter+1) is the updated whale position, b is the spiral shape parameter, and l is a random number between [-1,1].

[0076] It can be understood that the implementation steps of WOA are as follows: a) Initialization, whale population size N, maximum number of iterations T max , the position X of each individual in the whale population i (i=1, 2, 3, …, n); b) calculate the corresponding fitness value of each whale, select the n vectors with the smallest fitness value as the initial population position, record the optimal fitness value and the corresponding position vector, and update the parameters a (control parameter), A (coefficient vector), C (coefficient vector), l (random number between [-1, 1]), and p (random number between [0, 1]); c) when p<0.5 and |A|<1, update the individual position according to formula (2); d) when p<0.5 and |A|≥1, update the individual position according to formula (10); e) when p≥0.5, update the individual position according to the above formula; f) calculate the fitness and update the current optimal solution; g) if the termination condition is met, output the optimal individual, that is, the optimal solution found by the algorithm, otherwise, return to step c);

[0077] Specifically, in the early stage of hunting, since the position of the optimal individual in the search space is unknown, WOA assumes that the current best candidate solution is the target prey. After defining the best search agent, other search agents update their positions to the best search agent. The position update expression is as follows:

[0078] D1= |C·X*(t)- X(t) | (1)

[0079] X(t+1) = X*(t)-A·D1 (2)

[0080] Where: t is the current iteration number; X* is the position vector of the current best solution; X is the position vector of the individual whale; D1 is the distance between the individual whale and the prey; || is the absolute value; · is the element-by-element multiplication; A and C are coefficient vectors used to control the swimming mode of the whale, and there is

[0081] A = 2a·ra (3)

[0082] C = 2·r (4)

[0083] a = 2-2t / Tmax (5)

[0084] In order to simulate the bubble net attack behavior of humpback whales with mathematical models, two mechanisms, shrinking and surrounding and spiral position update, are designed. a) Shrinking and surrounding mechanism. In the iterative process, this behavior is achieved by reducing the value of a in equation (3) from 2 to 0, at which time A fluctuates in [-a, a]. When A is a random value of [-1, 1], the whale can be located anywhere between the original position and the current optimal position. Figure 2 It shows the possible positions between (X, Y) and (X*, Y*) in two-dimensional space when 0≤A≤1. b) Spiral position update mechanism. First, the distance from the whale individual (X, Y) to the prey (X*, Y*) is calculated, and then a spiral equation is used to simulate the spiral motion of the humpback whale. The mathematical expression of the spiral equation is as follows:

[0085] D2= |X*(t)-X(t)| (6)

[0086] X(t+ 1) = D2·ebl·cos(2πl)+ X*(t) (7)

[0087] Where: D2 is the distance from the individual whale to its prey; b is a constant used to define the shape of the logarithmic spiral; l is a random number in [-1, 1].

[0088] When a humpback whale approaches its prey, its shrinking and surrounding and spiraling position updating behaviors are performed simultaneously. In order to simulate this bubble net attack, it is assumed that the humpback whale has a 50% probability of shrinking and surrounding and spiraling position updating. The mathematical model is described as follows:

[0089]

[0090] Where: p is a random number in [0, 1].

[0091] In this stage, the whale population conducts global exploration. When |A|≥1, the whale population no longer updates its position based on the current optimal solution, but updates its position based on a randomly selected whale. The purpose is to increase the search range and find the optimal solution to maintain the diversity of the population. Therefore, only a small change to equations (1) and (2) is needed to obtain the mathematical model of this stage.

[0092] Drand= |C·Xrand-X(t)| (9)

[0093] X(t + 1) = Xrand-A·Drand (10)

[0094] Where: Xrand represents the position vector of a whale randomly selected from the group; Drand represents the distance from the randomly selected whale to the prey.

[0095] The voltage sag source location method of the present invention has the following beneficial effects:

[0096] 1. The advantages of judging the temporary sag line according to the polarity of the reactive power disturbance caused by the positive sequence temporary sag are: it is less affected by the network structure of the power system and is not affected by the short-circuit fault type and load model.

[0097] 2. Advantages of establishing a precise positioning model for voltage sag: the positioning model is simple, the calculation amount is small, the solution time is short, and the positioning efficiency is high.

[0098] 3. Advantages of introducing a variable spiral factor: The variable spiral factor g is designed with reference to the mathematical model of the spiral. It changes from large to small as the number of iterations increases. The search path is dynamically adjusted during the algorithm search process, thereby further enhancing the algorithm's global optimization and convergence capabilities.

[0099] According to the second aspect of the present invention, a voltage sag source positioning system based on positive sequence sag disturbance reactive power comprises:

[0100] A data acquisition module configured to obtain three-phase voltage and three-phase current data of each monitoring point;

[0101] A power calculation module configured to calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity;

[0102] A model building module is configured to build a voltage sag accurate positioning model;

[0103] The position calculation module is configured to solve the voltage sag precise positioning model by improving the whale optimization algorithm to accurately determine the location of the voltage sag source.

[0104] The voltage sag source positioning system of the present invention is less constrained by the power grid structure, load model and measurement accuracy, has high positioning accuracy and small calculation amount.

[0105] In one example of the present invention, the power calculation module includes:

[0106] The first disturbance calculation unit is configured to use the superposition principle to decompose the power system into a normal operating state network only under the action of the system power supply and a sag component fault network only under the action of the sag disturbance voltage, and calculate the three-phase sag disturbance voltage and current at the monitoring point according to the three-phase voltage and current data measured at the monitoring point;

[0107] The second disturbance calculation unit is configured to decompose the positive-sequence sag component fault network from the sag component fault network by using a symmetrical component method, and calculate the three-phase positive-sequence sag disturbance voltage and current at the monitoring point; Figure 2 As shown, Z s1 , Z s2 are the equivalent internal impedance of each phase on the power supply side and the load side, Z L1 , Z L2 are the impedance of each phase line between the sag source f and the monitoring points M1 and M2, Δu fa , Δu fb , Δu fc It is the three-phase positive-sequence temporary sag disturbance voltage at the temporary sag point.

[0108] The disturbance reactive power calculation unit is configured to calculate the positive sequence sag disturbance reactive power at the monitoring point, and the calculation formula is as follows:

[0109]

[0110] In the formula, Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc They are the three-phase positive-sequence temporary drop disturbance current at the monitoring point respectively.

[0111] In one example of the present invention, the power calculation module further includes:

[0112] A voltage sag source position determination unit is configured to determine the upstream and downstream relationship of the voltage sag source relative to the monitoring point according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point;

[0113] The voltage sag line determination unit is configured to determine the voltage sag line by analyzing the distribution positions of the monitoring points in the power system.

[0114] In one example of the present invention, the model building module includes:

[0115] The objective function unit is configured to minimize the sum of the difference spectral norms between the calculated value of the positive sequence sag disturbance reactive power at the monitoring point and the actual measured value, and determine the objective function of the voltage sag precise positioning model as follows:

[0116]

[0117] In the formula, ||||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistor.

[0118] The voltage sag source locating system of the present invention has the following beneficial effects:

[0119] 1. The advantages of judging the temporary sag line according to the polarity of the reactive power disturbance caused by the positive sequence temporary sag are: it is less affected by the network structure of the power system and is not affected by the short-circuit fault type and load model.

[0120] 2. Advantages of establishing a precise positioning model for voltage sag: the positioning model is simple, the calculation amount is small, the solution time is short, and the positioning efficiency is high.

[0121] 3. Advantages of introducing a variable spiral factor: The variable spiral factor g is designed with reference to the mathematical model of the spiral. It changes from large to small as the number of iterations increases. The search path is dynamically adjusted during the algorithm search process, thereby further enhancing the algorithm's global optimization and convergence capabilities.

[0122] The exemplary implementation scheme of the method and system for locating the voltage sag source based on the positive-sequence sag disturbance reactive power proposed in the present invention is described in detail above with reference to the preferred embodiments. However, those skilled in the art will appreciate that, without departing from the concept of the present invention, various modifications and variations can be made to the above-mentioned specific embodiments, and various technical features and structures proposed in the present invention can be combined in various ways without exceeding the protection scope of the present invention, which is determined by the appended claims.

Claims

1. A method for locating voltage sag sources based on positive sequence sag disturbance reactive power, characterized in that: The steps include: S10: Acquire three-phase voltage and three-phase current data of each monitoring point; S20: Calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity; S30: Establishing a voltage sag accurate positioning model; S40: The voltage sag precise positioning model is solved by improving the whale optimization algorithm to accurately determine the location of the voltage sag source.

2. The method for locating voltage sag sources based on positive sequence sag disturbance reactive power according to claim 1, characterized in that: In step S20, calculating the positive sequence sag disturbance reactive power includes: S21: Using the superposition principle, the power system is decomposed into a normal operating state network under the action of system power only and a sag component fault network under the action of sag disturbance voltage only. The three-phase sag disturbance voltage and current at the monitoring point are calculated based on the three-phase voltage and current data measured at the monitoring point. S22: Decompose the positive-sequence sag component fault network from the sag component fault network using the symmetrical component method, and calculate the three-phase positive-sequence sag disturbance voltage and current at the monitoring point; S23: Calculate the positive sequence sag disturbance reactive power at the monitoring point. The calculation formula is as follows: Where Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc are the three-phase positive sequence sag disturbance currents at the monitoring point respectively.

3. The method for locating voltage sag sources based on positive sequence sag disturbance reactive power according to claim 1, characterized in that: In step S20, determining the sag circuit according to its polarity includes the following steps: The upstream and downstream relationship of the voltage sag source relative to the monitoring point is determined according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point; By analyzing the distribution of each monitoring point in the power system, the voltage sag line can be determined.

4. The method for locating voltage sag sources based on positive sequence sag disturbance reactive power according to claim 1, characterized in that: Taking the minimum sum of the difference spectral norms between the calculated value and the actual measured value of the reactive power of the positive sequence sag disturbance at the monitoring point as the goal, the objective function of the voltage sag precise positioning model is determined as follows: Where, || ||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistance.

5. The method for locating voltage sag sources based on positive sequence sag disturbance reactive power according to claim 4, characterized in that: The constraints of the objective function are: Where R fmax is the maximum value of the positive sequence transition resistance.

6. The method for locating voltage sag sources based on positive sequence sag disturbance reactive power according to claim 1, characterized in that: The improved whale optimization algorithm includes an improvement to the spiral update position. The formula for the improved spiral update position is as follows: Where iter is the current number of iterations, iter max is the maximum number of iterations, X * (iter) is the current global optimal whale position, X(iter) is the current whale position, X(iter+1) is the updated whale position, b is the spiral shape parameter, and l is a random number between [-1,1].

7. A voltage sag source location system based on positive sequence sag disturbance reactive power, characterized in that: include: a data acquisition module configured to acquire three-phase voltage and three-phase current data of each monitoring point; a power calculation module configured to calculate the reactive power of the positive sequence sag disturbance and determine the sag line according to its polarity; A model building module is configured to build a voltage sag accurate positioning model; The position calculation module is configured to solve the voltage sag precise positioning model by using the improved whale optimization algorithm to accurately determine the position of the voltage sag source.

8. The voltage sag source location system based on positive sequence sag disturbance reactive power according to claim 7, characterized in that: The power calculation module includes: a first disturbance calculation unit configured to decompose the power system into a normal operating state network under the action of system power only and a sag component fault network under the action of sag disturbance voltage only, using the superposition principle, and calculate the three-phase sag disturbance voltage and current at the monitoring point based on the three-phase voltage and current data measured at the monitoring point; A second disturbance calculation unit is configured to decompose a positive-sequence sag component fault network from a sag component fault network using a symmetrical component method, and calculate the three-phase positive-sequence sag disturbance voltage and current at a monitoring point; The disturbance reactive power calculation unit is configured to calculate the positive sequence sag disturbance reactive power at the monitoring point. The calculation formula is as follows: Where Δu ma , Δu mb , Δu mc are the three-phase positive sequence sag disturbance voltage at the monitoring point, Δi ma , Δi mb , Δi mc are the three-phase positive sequence sag disturbance currents at the monitoring point respectively.

9. The voltage sag source location system based on positive sequence sag disturbance reactive power according to claim 7, characterized in that: The power calculation module also includes: a voltage sag source location determination unit configured to determine an upstream and downstream relationship of a voltage sag source relative to a monitoring point according to the polarity of the positive-sequence sag disturbance reactive power: if the positive-sequence sag disturbance reactive power at the monitoring point is negative, the voltage sag source is downstream of the monitoring point; if the positive-sequence sag disturbance reactive power at the monitoring point is positive, the voltage sag source is upstream of the monitoring point; The voltage sag line determination unit is configured to determine the voltage sag line by analyzing the distribution positions of the monitoring points in the power system.

10. The voltage sag source location system based on positive sequence sag disturbance reactive power according to claim 7, characterized in that: The model building module includes: The objective function unit is configured to minimize the sum of the difference spectral norms between the calculated value of the positive sequence sag disturbance reactive power and the actual measured value at the monitoring point, and determine the objective function of the voltage sag precise positioning model as follows: Where, || ||2 represents the spectral norm, They represent the calculated value and actual measured value of the reactive power of the positive sequence sag disturbance at each monitoring point; λ is the sag distance ratio; R f is the transition resistance.

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