CN106816871B - State similarity analysis method for power system - Google Patents

Abstract

The invention provides a method for analyzing state similarity of a power system, which comprises the following steps: the network analysis calculation determines the progression of the multilevel topology analysis, the topology analysis is carried out on the members of the rule set F determined according to the progression of the topology analysis, the key information is extracted from the abstract result of the multilevel topology analysis, and the similarity between the states is determined according to the distance between the state vector and the different state vectors calculated according to the distance function. The technical scheme provided by the method adopts a method for analyzing the similarity of the power grid state data, and the similarity between different power grid states is rapidly quantized.

Description

State similarity analysis method for power system

Technical Field

The invention belongs to the technical field of electric power automation, and particularly relates to a method for analyzing state similarity of an electric power system.

Background

The basis of smart grids is power system analysis, which relies on grid state data. Because the investment scale of the current power grid construction is continuously increased, the construction speed is continuously accelerated, and the power grid operation control is required to be developed towards the direction of refinement and intellectualization. The scale of the power grid data is larger and larger, and the method only depends on the improvement of the algorithm and the improvement of the computing power and is increasingly unable to do the best in the aspect of improving the speed of network analysis.

The traditional method for judging whether the data are the same can be easily judged by comparing data files. However, in many cases, it is not only necessary to determine whether the data is the same, but also to determine whether the data content is similar. The earliest requirement for data similarity judgment originates from the internet field, and the main purpose of the requirement is to serve as a basis for judging the duplication of webpage content. When faced with massive amounts of data, a series of very different situations often occur. For example, processing data requires a larger storage space than that required for rapid quantitative analysis of similarity between data files, and processing data requires as little computation as possible. Although the similarity of data is more difficult, the technical steps are similar, mainly: sampling and compressing the data file to form a simplified description data set of the file content; quantifiable similarities of different data sets are compared by means of a similarity comparison algorithm. The state of the power system describes the power grid information of the power grid at a certain moment, and the similarity analysis is basically consistent with the steps. However, data describing the state of the power system are mainly structural data and have mutual power flow equation constraints, and data analyzed and calculated by the power network particularly has self-generating characteristics, so that a method for quantifying similarity of the state of the power system needs to be provided, so that the method is more effective in obtaining many aspects of similarity analysis of a sample space, a sample expression mode and a sample space of the power system.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a power system state similarity analysis method which is used for quantitatively analyzing the similarity of the power system power grid states. The method is different from the traditional comparison technology of the power system state, when a large amount of power grid state data are faced, the power grid state data can be simplified into a state vector carrying power grid state characteristics, then the distance between two state vectors is calculated through a function meeting local sensitivity, and the similarity of two different power grid state data is represented through the distance.

A method of power system state similarity analysis, the method comprising:

I. the network analysis calculation determines the number of stages of the multilevel topology analysis;

II. Performing topology analysis on members of a rule set F determined according to the progression of the topology analysis;

III, extracting key information from an abstract result of the multilevel topological analysis and forming a state vector;

IV, determining the similarity between the states according to the distances of different state vectors calculated by the distance function.

Further, the step I comprises:

i-1, inputting a power grid topology model;

and I-2, constructing a topological graph formed by the physical nodes and the connecting branches thereof.

Further, the topology map includes:

a first-level topological graph formed by the physical nodes and the connection branches thereof;

merging the physical nodes with the branch impedance of zero and then connecting the branches to form a second-level topological graph;

and combining the units or loads accessed to the same bus in the same station, and simplifying a third-level topological graph formed by the calculated nodes and the connecting branches thereof.

Further, when the plant station has a group phenomenon, the plant stations are merged, and the nodes and the connection branches of the merged plant station form a fourth-level topological graph.

Further, the topological graph is abstracted according to requirements to form a topological graph at a higher level.

Further, the step II includes: respectively carrying out k-level topology analysis on N levels of the power system according to members of a rule set F shown in the following formula, and carrying out the topology analysis result W shown in the following formula_kReserving;

the rule set F ═ { F ═ F₁，……，F_kL where the function F_i：W_i→W_i+1I < k }, and the topology analysis result W_k＝{U₁，U₂……，U_k|U₁∪U₂∪U₃……∪U_k＝V，U_i∩U_jPhi, i ≦ k, j ≦ k, i ≠ j }, where V is a non-empty set of vertices of the grid topology model graph.

Further, the step III comprises the following steps:

III-1, extracting the apparent power of the branch from the result of the multilevel topological analysis abstraction;

III-2, sequencing the apparent power of the branches according to voltage grades from high to low or sequencing the apparent power of the branches according to power from high to low to construct an L table;

III-3, constructing a new Ln list according to the first n selected power grid scales and similarity quantization precision;

III-4, let List Ln ═ L₁,L₂,…Ln]Conversion to vector Pn ═ (P)₁,P₂… Pn), where Pi is the apparent power level of the corresponding branch Li.

Further, the similarity between the states in the step IV is shown as the following formula:

wherein, P_xAnd P_yVectors, P, of two power system states, respectively_x＝(p_x1，p_x2，…，p_xn)，P_y＝(p_y1，p_y2，…，p_yn)。

An apparatus for a power system state similarity analysis method, the apparatus comprising:

the acquisition module is used for acquiring different power grid state data;

the state estimation module is connected with the acquisition module and used for carrying out state estimation on the power grid state data;

the calculation module is connected with the state estimation module and used for calculating the similarity between the states of the two power grids;

and the output module is connected with the calculation module and used for outputting the calculation result.

Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:

1. the technical scheme provided by the invention can quickly judge the fluctuation range of the state change of the power grid all day long, and can quickly determine whether to start the power grid analysis and calculation according to the fluctuation size.

2. The technical scheme provided by the invention can be used for rapidly searching the given power grid state data in the whole period, and rapidly identifying the power grid state data at similar or same time.

3. According to the technical scheme provided by the invention, the analysis and calculation times of the power grid can be reduced according to the similarity of the state data of the power grid, and the real-time calculation efficiency of the power grid is greatly improved.

4. The technical scheme provided by the invention classifies massive power grid state data according to the similarity of the power grid states, not according to time periods.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a 2-dimensional graph of pairwise comparison of grid states in an embodiment;

fig. 3 is a 3-dimensional graph of the grid state pairwise comparison in the embodiment.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings. In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The mathematical expression is as follows:

1) the multi-level topology model may be represented using a mathematical model, which is described as follows:

(1) presence map G ═<V,E>Wherein V ═ d₁,……,d_n}，E＝{(d_i,d_j)|d_i∈V,d_j∈V,d_i≠d_j}

(2) Presence set U_k≠φ，

Satisfy U₁∪U₂∪U₃……∪U_m＝V，U_i∩U_jPhi, where k ≦ m, i ≦ m, j ≦ m, i ≠ j;

(3) presence set W_k＝{U₁，U₂……，U_k|U₁∪U₂∪U₃……∪U_k＝V，U_i∩U_j＝φ，i≦k，j≦k，i≠j}

(4) Presence rule set F ═ F₁，……，F_kL where the function F_i：W_i→W_i+1，i＜k}；

The multilevel topology analysis is to partially merge nodes and branches in a topology graph so as to achieve the realization of different levels of the same power network topology.

2) The function for calculating the distance between two state vectors needs to satisfy the following two conditions:

①, if d (x, y) ≦ d1, the probability that f (x) ≦ f (y) is at least P1, i.e., P (f) (x) ≦ f (y) ≧ P1;

② if d (x, y) ≧ d2, the probability of f (x) ═ f (y) is at most P2, i.e., P (f) (x) ≦ P2;

where x and y are state vectors, d (x, y) is a distance function of the state vectors, f (x) and f (y) are states characterized by the state vectors, P (f) (x) (f) (y)) is a probability that the two states characterized by x and y are equal, P1 and P2 are probability values, d1 and d2 are distance values, and P1> P2>0, d2> d 1.

The distance functions which can satisfy the above two conditions are many, and the cosine similarity function is adopted to judge the distance between two vectors x and y:

wherein x is (x)₁,x₂,…，x_n)，y＝(x₁,x₂,…，x_n)，

<x,y>＝x₁y₁+x₂y₂+…+x_ny_n

Fig. 1 shows an implementation process of the present invention:

according to the description of the mathematical model, the specific implementation flow of the similarity analysis of the power system states in the invention is as follows:

1) determining the grade number of the multilevel topology analysis according to the requirement of network analysis, calculation and analysis;

2) determining a rule set F used in the topology analysis according to the progression of the topology analysis, wherein the membership of the rule set is determined by the progression determined in the first step;

3) carrying out topology analysis according to members of the rule set F in sequence, and reserving the result of the topology analysis;

extracting key information from the result of the multilevel topological analysis abstraction and forming a state vector;

4) and calculating the distances of different state vectors through a distance function, and obtaining the similarity between the two states by the function.

An embodiment of a power system state similarity analysis method: for two different power grid state data, a power grid model abstracted to a required level is obtained through multi-level topological analysis, then power grid state key information is extracted to form a power grid state vector, and the distance between the two state vectors is calculated through a distance function of the power grid state vector, so that the similarity of the two different power grid states is represented.

The similarity analysis method for the power system state in the method comprises the following steps:

step one, determining the grade number of multi-grade topology analysis according to the requirement of network analysis, calculation and analysis;

the number of stages of the specific multi-stage topology analysis is related to related network analysis application and power grid state data, and a proper number of stages can be determined according to requirements of analysis speed, storage scale and the like. The higher the abstract level, the smaller the storage space, the faster the analysis speed, but the more the power system state information is lost. When modeling the power system, the most detailed diagram can be regarded as a diagram formed by the physical nodes and the connecting branches thereof, and the diagram is a first-level diagram. When the physical nodes with the branch impedance of zero are combined, a graph formed by the calculation nodes and the connection branches thereof is formed, and the graph is a second-level graph. When the units or loads accessed to the same bus in the same station are combined, a graph formed by simplified computing nodes and connecting branches thereof is formed, and the graph is a third-level graph. When the power plant group exists and the like, the stations can be merged, and a graph formed by the nodes of the merged stations and the connecting branches thereof is formed, and the graph is a fourth-level graph.

Extracting key information from a result of multilevel topological analysis abstraction and forming a state vector;

the key information is extracted from the abstract topological graph, and the method specifically comprises the following steps:

2.1 extracting branch lists and apparent powers of corresponding branches from the results of the multilevel topology analysis abstraction;

2.2, sorting the apparent power of the branches from high to low according to the voltage level, and sorting the branches with the same voltage level from high to low according to the power to form a list L;

2.3 according to the power grid scale and the precision requirement of similarity quantization, selecting the first n list elements as a new list Ln; (generally, the n value is determined according to 30% of the number of the elements in the list L; if the related application has high requirement on the accuracy of the power grid, the value can be up to more than 50%, and if the required information is not lost, all the elements in the list L can be directly selected)

2.4 convert the list Ln ═ L1, L2, … Ln ] to the vector Pn ═ P1, P2, … Pn, where Pi is the apparent power level of the corresponding branch Li;

and step three, calculating the distances of different state vectors through a distance function, and obtaining the similarity between the two states by the function.

After obtaining the vectors Px and Py of the two power system states, the similarity of the two power system state samples is represented by the cosine theorem of the vectors. The similarity size range is [0,1], and the closer the calculation result is to 1, the more approximate the two power system states are.

Wherein, P_xAnd P_yVectors, P, of two power system states, respectively_x＝(p_x1，p_x2，…，p_xn)，P_y＝(p_y1，p_y2，…，p_yn)。

The device used by the power system state similarity analysis method comprises the following steps:

the acquisition module is used for acquiring different power grid state data;

the state estimation module is connected with the acquisition module and used for carrying out state estimation on the power grid state data;

the calculation module is connected with the state estimation module and used for calculating the similarity between the states of the two power grids;

and the output module is connected with the calculation module and used for outputting the calculation result.

For a specific calculation method, reference may be made to the descriptions of the above method embodiments, and details are not repeated here.

The method comprises the steps of taking a power grid state estimation result of a provincial power grid in 24 hours every 5 minutes all day as calculation data, comparing similarity of 288 power grid state data every two with the data size of 491MB, calculating 82944 times in total through similarity calculation, calculating the time duration of 81 seconds through computer calculation, and finally obtaining effect graphs as shown in the attached figures 2 and 3.

From fig. 2 and 3, the regions from dark to light in color indicate that the similarity is large to small. It can be seen that the closer the data satisfies the common sense regularity, the more similar the time. It can be seen from the figure that there are 3 periods of roughly smooth operation of the power grid throughout the day, and the calculation times of power grid analysis can be reduced in the time region. At intervals of 3 zones, there is a period of time of intense fluctuation, which should enhance grid analysis times and grid monitoring.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.

Claims (8)

1. A method for analyzing state similarity of a power system, the method comprising:

I. the network analysis calculation determines the number of stages of the multilevel topology analysis;

II. Performing topology analysis on members of a rule set F determined according to the progression of the topology analysis;

III, extracting branch lists and apparent powers of corresponding branches from abstract results of the multilevel topological analysis and forming state vectors;

IV, determining the similarity between the states according to the distances of different state vectors calculated by the distance function.

2. The method for analyzing the similarity of the states of the power system according to claim 1, wherein the step I comprises the following steps:

i-1, inputting a power grid topology model;

and I-2, constructing a topological graph formed by the physical nodes and the connecting branches thereof.

3. The method according to claim 2, wherein the topological graph comprises:

a first-level topological graph formed by the physical nodes and the connection branches thereof;

merging the physical nodes with the branch impedance of zero and then connecting the branches to form a second-level topological graph;

and combining the units or loads accessed to the same bus in the same station, and simplifying a third-level topological graph formed by the calculated nodes and the connecting branches thereof.

4. The method according to claim 3, wherein the plant stations are merged when the cluster phenomenon occurs in the plant stations, and the nodes and the connecting branches of the merged plant stations form a fourth-level topological graph.

5. The method for analyzing similarity of states of a power system according to claim 4, wherein the topological graph is abstracted according to requirements to form a higher-level topological graph.

6. The method for analyzing the similarity of the states of the power system according to claim 1, wherein the step II comprises the following steps: respectively carrying out k-level topology analysis on N levels of the power system according to members of a rule set F shown in the following formula, and carrying out the topology analysis result W shown in the following formula_kReserving;

the rule set F ═ { F ═ F₁，……，F_kL where the function F_i：W_i→W_i+1I < k }, and the topology analysis result W_k＝{U₁，U₂……，U_k|U₁∪U₂∪U₃……∪U_k＝V，U_i∩U_jPhi, i ≦ k, j ≦ k, i ≠ j }, where V is a non-empty set of vertices of the grid topology model graph.

7. The method for analyzing the similarity of the states of the power system according to claim 1, wherein the step III comprises the following steps:

III-1, extracting the apparent power of the branch from the result of the multilevel topological analysis abstraction;

III-2, sequencing the apparent power of the branches according to voltage grades from high to low or sequencing the apparent power of the branches according to power from high to low to construct an L table;

III-3, constructing a new Ln list according to the first n list elements selected by the power grid scale and the similarity quantization precision;

III-4, let List Ln ═ L₁,L₂,…Ln]Conversion to vector Pn ═ (P)₁,P₂… Pn), where Pi is the apparent power level of the corresponding branch Li.

8. The method according to claim 1, wherein the similarity between the states in the step IV is represented by the following formula:

wherein, P_xAnd P_yVectors, P, of two power system states, respectively_x＝(p_x1，p_x2，…，p_xn)，P_y＝(p_y1，p_y2，…，p_yn)。

Images