Disclosure of Invention
The invention mainly aims to provide a photovoltaic power station solar irradiance short-term prediction technical method based on an optimal graph structure, and aims to solve the problems that the existing irradiance prediction method does not consider the influence of irradiance conditions in the adjacent range of a target station on the target station and the prediction effect is poor due to insufficient mining of space-time information of a historical irradiance sequence.
In order to achieve the above purpose, the invention provides a photovoltaic power station solar irradiance short-term prediction method based on an optimal graph structure, which comprises the following steps:
s10, constructing a space-time associated station of a target station through geographic range and azimuth information;
step S20, acquiring historical irradiance time series data of a target station and each time-space associated station;
step S30, calculating the correlation between the space-time correlation field station and the target field station data, and screening space-time correlation field stations with high correlation;
step S40, constructing graph structure data according to the space-time associated field stations obtained by screening;
and S50, establishing a graph neural network prediction model taking graph structure data as input to realize irradiance short-term prediction.
Further, the step S10 includes:
step S101, intercepting the geographic space range of the area where the target station is located, wherein other stations in the range are space-time associated stations.
Step S102, longitude and latitude coordinate information of the space-time correlation station is obtained.
The longitude and latitude coordinate information of a plurality of time-space associated stations is refined and generated by utilizing an automatic grid generation algorithm.
Further, the step S20 includes:
step S201, using a satellite cloud image-irradiance mapping method, mapping historical irradiance time series data of a target station and each space-time associated station from the satellite cloud image.
Step S202, training a data deviation correction model by using the target station data, and performing deviation correction on irradiance of the time-associated station.
Further, the step S30 includes:
step S301, normalized mutual information N is utilized MI A correlation between the target station and each spatio-temporal associated station historical irradiance data is calculated.
Step S302, each time-space associated station is divided into N MI The values are sorted from big to small, only the top 1/3 of the sorting is retained.
Further, the step S40 includes:
step S401, constructing different graph structure data according to the space-time associated stations obtained by screening, wherein the graph structure data consists of a node characteristic matrix and an adjacent matrix, the node characteristic matrix consists of a target station and historical irradiance data of each space-time associated station, and the adjacent matrix is a connection relation determined according to the correlation among the station data.
In step S402, the graph structure data is optimal graph structure data obtained based on graph connectivity evaluation.
Calculating a complex network topology statistical index according to the adjacency matrix; the complex network topology statistical indexes comprise average degree, average aggregation coefficient, average shortest path distance among nodes, average node betweenness centrality and network connectivity.
And weighting and calculating the statistical indexes of each complex network topology to obtain the comprehensive evaluation index of the graph connectivity.
And (3) calculating a graph connectivity comprehensive evaluation index of the constructed graph structure data in the step S401, when the comprehensive evaluation index is larger than a threshold value, considering the graph connectivity comprehensive evaluation index as the optimal graph structure data, otherwise, returning to the step S401 for circulation until the optimal graph structure data is constructed.
Further, the step S50 includes:
step S501, performing normalization processing on the historical irradiance data of each station in the node feature matrix in the graph structure data.
Step S502, a graph neural network prediction model is built by taking graph structure data as input and irradiance as output.
Step S503, the graph structure data is input into a graph neural network prediction model, and the output irradiance prediction result is subjected to inverse normalization processing to obtain a final target station irradiance prediction result.
The invention also provides a storage medium for storing a computer program which is executed by a processor to realize the photovoltaic power station solar irradiance short-term prediction method based on the optimal graph structure.
The beneficial effects of the invention are as follows:
(1) The solar irradiance short-term prediction method can fully consider the space-time correlation influence of the weather irradiance condition of the adjacent range of the target prediction station on the target station under the condition of missing surrounding weather data, and the influence of surrounding factors on the target station is often ignored by the person skilled in the art.
(2) The solar irradiance short-term prediction method disclosed by the invention only needs to utilize the historical irradiance time sequence to realize short-term prediction of irradiance, is easy to realize, is beneficial to improving the short-term prediction precision of irradiance, is beneficial to providing technical support for planning and site selection of photovoltaic power stations, and is also beneficial to carrying out reasonable energy storage guidance on the built photovoltaic power stations.
(3) The solar irradiance short-term prediction method considers irradiance of the adjacent range stations, compared with other consideration methods, the space-time correlation stations in the method are purposefully and autonomously constructed and screened, have stronger space-time correlation with the target stations, and provide graph connectivity indexes based on complex network topology indexes to select optimal graph structure data.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Detailed Description
It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1, the invention provides a photovoltaic power station solar irradiance prediction method based on an optimal graph structure, which comprises the following steps:
s10, constructing a space-time associated station of a target station through geographic range and azimuth information;
step S20, acquiring historical irradiance time series data of a target station and each time-space associated station;
step S30, calculating the correlation between the space-time correlation field station and the target field station data, and screening space-time correlation field stations with high correlation;
step S40, constructing graph structure data according to the space-time associated field stations obtained by screening;
and S50, establishing a graph neural network prediction model taking graph structure data as input to realize irradiance short-term prediction.
The constructing the space-time associated field station of the target field station through the geographic range and the azimuth information in the step S10 includes:
step S101, intercepting the geographic space range of the area where the target station is located, wherein other stations in the range are space-time associated stations. Taking a target station as a center, intercepting a rectangular area, calculating four vertex coordinates of the rectangular area, and calculating the rectangular area according to the following formulas (1) - (6).
left-top=(lat+dlat,lon-dlon) (3)
left-bottom=(lat-dlat,lon-dlon) (4)
right-top=(lat+dlat,lon+dlon) (5)
right-bottom=(lat-dlat,lon+dlon) (6)
Wherein R represents the geographical distance between the vertex and the target station, R=150 km is taken in the invention, R is taken as Ground (floor) = 6378.137km denotes the earth radius, lon is the target station longitude, lat is the target station latitude, in degrees,the radian is converted into an angle, dlon and dlat represent the offset of longitude and latitude, left-top, left-bottom, right-top and right-bottom represent the coordinates of four vertexes of a rectangular frame respectively, and other field stations in the rectangular frame are space-time switchesThe station is a real photovoltaic power station or a virtual power station, because the station can be assumed to be a photovoltaic power station as long as the station has coordinate information and corresponding irradiance time series data.
Step S102, longitude and latitude coordinate information of the space-time correlation station is obtained. And (3) generating longitude and latitude coordinate information of a plurality of space-time associated stations in a refining mode by using an automatic grid generation algorithm in the geographic space range of the area generated in the step S101 and taking the target station as the center according to different distances and different azimuth angles.
The step of obtaining historical irradiance time series data of the target station and each space-time associated station in the step S20 includes:
step S201, using a satellite cloud image-irradiance mapping method, mapping historical irradiance time series data of a target station and each space-time associated station from the satellite cloud image. By adopting the satellite cloud image-irradiance mapping method in the patent application 202111336372.8, longitude and latitude coordinates of the target station and the space-time correlation station obtained in the step S102 are input, and historical irradiance time series data of the corresponding position is output.
Because the data obtained by mapping has deviation from the actual value, deviation correction and data quality control are required.
Step S202, training a data deviation correction model by using the target station data, and performing deviation correction on irradiance of the time-associated station. Taking the irradiance mapping value and the temperature information of the target station as input, taking the irradiance actual value of the target station as output, and training by using an SVM model to obtain a data deviation correction model; and correcting the deviation of irradiance mapping values of other space-time related stations by using a data deviation correction model obtained by training, and further carrying out an abnormal data analysis preprocessing process on the irradiance mapping values to remove data with larger deviation and complement missing values in order to improve the prediction accuracy.
The step S30 of calculating the correlation between the space-time correlation station and the target station data and screening the space-time correlation station with high correlation includes:
step S301, normalized mutual information N is utilized MI Calculation ofCorrelation between the target station historical irradiance data obtained in step S20 and each spatiotemporal correlated station historical irradiance data. The calculation formula is as follows:
p r (N MI (X,Y)≥τ)=2/3
where X and Y are input data of historical irradiance of the target station and the spatio-temporal associated station, pr (·) is a probability function, and pr (X, Y) is a joint probability. N (N) MI The higher the value, the stronger the correlation.
Step S302, each time-space associated station is divided into N MI The values are sorted from big to small, only the top 1/3 of the sorting is retained. Or choose N MI The time-space correlation station with a value greater than the threshold value can be valued according to the actual situation and the experience of the person skilled in the art.
Referring to fig. 2, the result of correlation analysis of historical irradiance data of a space-time correlation station and a target station constructed based on a solar irradiance short-term prediction model of an optimal diagram structure is shown. The abscissa indicates the reference numerals of the respective stations, wherein 0 indicates the target station, and the color in each cell represents the correlation calculation result between the two stations, and the deeper the color, the stronger the correlation.
The step S40 of constructing the optimal diagram structural data according to the space-time associated field station obtained by the screening includes:
step S401, constructing different graph structure data according to the space-time associated stations obtained by screening, wherein the graph structure data consists of a node characteristic matrix and an adjacent matrix, the node characteristic matrix consists of a target station and historical irradiance data of each space-time associated station, and the adjacent matrix is a connection relation determined according to the correlation among the station data.
A graph neural network is a neural network that can process graph structure data. A graph typically contains nodes and edges, each node having its own attributes or characteristics, while edges represent relationships between nodes. Only if irradiance data is converted into map structure data can irradiance be predicted using a map neural network model. The stations are thus considered nodes, with the correlation of irradiance data between stations as an attribute of the edge.
By selecting different data and setting different thresholds, different graph structure data are constructed, and the adjacency matrix is a connection relation determined according to the correlation between the station data, which may not be limited to the following definition:
in the formula (8), N MI (i, j) represents N between historical irradiance data for photovoltaic field station i and photovoltaic field station j MI The correlation coefficient epsilon represents the threshold value of the correlation coefficient, in the invention, half of the average value of the correlation matrix between stations is used as the threshold value, and can be set according to practical conditions, when the correlation coefficient between two photovoltaic power stations is smaller than the threshold value, the two photovoltaic power stations are considered to be not connected, and at the moment, the element A in the adjacent matrix is set ij Is 0.
In step S402, the graph structure data is optimal graph structure data obtained based on graph connectivity evaluation.
And calculating a complex network topology statistical index according to the adjacency matrix. The complex network topology statistical indexes include, but are not limited to, average degree, average aggregation coefficient, average shortest path distance between nodes, average node betweenness centrality and network connectivity, and the calculation formulas of the indexes are as follows:
equation (9) is an average degree calculation formula, where N is the total number of nodes in the network, and the number k of adjacent sides connected with node i i Called the degree of the node. Intuitively, the greater the degree of a node, the more important that node is. The degree of all nodes in the network is averaged to obtain the average degree DC of the network.
Equation (10) is an average aggregation coefficient calculation formula assuming nodes i and k i The individual nodes are directly connected, then for an undirected network this k i The maximum number of edges that may exist between individual nodes is k i While the number of actually existing edges is M i Whereby the aggregation factor is defined as C i AC is the average concentration factor.
Formula (11) is an average shortest path distance calculation formula among nodes, wherein G is a set of all nodes, N is the total number of nodes in the network, and the distance d between two nodes i and j in the network ij Is defined as the number of edges of the shortest path connecting the two nodes. For an undirected network, defining the average shortest path distance L between nodes as the distance d between node pairs in the network ij Average value of (2):
equation (12) is an average node betweenness centrality calculation formula, and the node betweenness is the proportion of the number of the nodes passing through all the shortest paths in the network. Wherein N is jl Representing the shortest path number, N, between nodes j and l jl (i) Representing the number of shortest paths between nodes j and l through node i. BC (BC) type i Represents node bets, and BC represents average node bets centrality.
Equation (13) is a calculation formula of network connectivity,for node-connectivity of node pair (i, j) in the network, the minimum number of nodes (except i, j) in the network that are to be removed such that node pair (i, j) (i+notejand i, j are not adjacent) are not connected. Connectivity of the graph network is represented by the average of node-connectivity for all non-adjacent node pairs in the network.
And weighting and calculating the statistical indexes of each complex network topology to obtain the comprehensive evaluation index of the graph connectivity. And (3) performing dimension reduction by using a principal component analysis method, representing all connectivity evaluation indexes by using a plurality of effective principal components with smaller quantity and higher contribution rate, determining weight coefficients corresponding to each effective principal component item by using an entropy weight method, and finally obtaining the graph connectivity comprehensive evaluation indexes according to each weight coefficient. The calculation formula is as follows, wherein k 1 +k 2 +k 3 +k 4 +k 5 =1。
GC=k 1 ·DC+k 2 ·AC+k 3 ·L+k 4 ·BC+k 5 ·K (14)
And (3) calculating a graph connectivity comprehensive evaluation index of the constructed graph structure data in the step S401, when the comprehensive evaluation index is larger than a threshold value, considering the graph connectivity comprehensive evaluation index as the optimal graph structure data, otherwise, returning to the step S401 for circulation until the optimal graph structure data is constructed. For example, the threshold may be taken as 10.
In the step S50, the step of establishing a graph neural network prediction model using graph structure data as input to implement irradiance prediction includes:
step S501, performing normalization processing on the historical irradiance data of each station in the node feature matrix in the graph structure data.
In order to accelerate the training speed of the prediction model and improve the prediction precision, the historical irradiance data of each corresponding station in the node characteristic matrix in the graph structure data is required to be normalized according to the following formula, and the data is kept between 0 and 1:
wherein,X i and X i ' is the original data and normalized data, X min And X max Is the minimum and maximum values in the sample. The normalization process includes both irradiance data for the target site and irradiance data for the spatio-temporal associated site for use in subsequently building the predictive model.
Step S502, a graph neural network prediction model is built by taking graph structure data as input and irradiance as output. Dividing the graph structure data sequence in the step S401 or the optimal graph structure data sequence in the step S402 into a training set and a test set according to the proportion of 7:3, taking time sequence data of three days of graph structure history as input on the training set, taking irradiance data of a target station and each space-time associated station in one future day as output, setting initialization parameters for a short-term irradiance prediction model based on a graph neural network, and training, wherein the prediction model has four layers of networks, including a graph learning layer, two graph convolution layers and one output layer.
Step S503, the graph structure data is input into a graph neural network prediction model, and the output irradiance prediction result is subjected to inverse normalization processing to obtain a final target station irradiance prediction result.
To illustrate the effectiveness of the method, the irradiance value of a certain photovoltaic power station 2020.5.1-2020.5.5 of inner Mongolia is predicted by the method, and the comparison result of the predicted value and the actual value is shown in fig. 3. As can be seen from FIG. 3, the irradiance prediction method of the invention has ideal effect and higher prediction accuracy through practical tests.
The embodiment of the invention also provides a storage medium for storing a computer program which is executed by a processor to realize the solar irradiance short-term prediction method of the photovoltaic power station.
In summary, the irradiance short-term prediction method of the embodiment of the invention is beneficial to providing technical support for planning and locating photovoltaic power stations, meanwhile, the method is also beneficial to reasonable energy storage guidance for the built photovoltaic power station, promotes benign healthy development in the field of photovoltaic power generation and ensures safe and stable operation of a power system.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.