CN115293415A - Multi-wind-farm short-term power prediction method considering time evolution and space correlation - Google Patents

Multi-wind-farm short-term power prediction method considering time evolution and space correlation Download PDF

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CN115293415A
CN115293415A CN202210900738.8A CN202210900738A CN115293415A CN 115293415 A CN115293415 A CN 115293415A CN 202210900738 A CN202210900738 A CN 202210900738A CN 115293415 A CN115293415 A CN 115293415A
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李丹
甘月琳
杨帆
缪书唯
方泽仁
梁云嫣
胡越
王奇
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China Three Gorges University CTGU
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Abstract

The invention discloses a multi-wind-farm short-term power prediction method considering time evolution and space correlation, which is mainly divided into four modules: the input module collects and preprocesses data, and the target is historical power and meteorological prediction data of a multi-wind farm in a target area; the time evolution mode tracking module respectively extracts a time sequence and a multi-periodicity time evolution mode of historical wind power data through the gated circulation unit and the multi-core convolution layer; the spatial correlation mode attention module introduces a time-varying mode attention mechanism to endow correlation weights to different time evolution modes of the multi-spatial variable; and finally, the output module outputs the day-ahead prediction scene of the power of the multiple wind power plants. According to the method, the time evolution mode of the wind power sequence is completely considered by constructing the time-space fusion multi-wind-farm short-term power prediction model with deep learning capability, the defect that the space dependency relationship is extracted statically by various existing models is overcome, and the purposes of improving prediction precision and robustness are achieved.

Description

Multi-wind-farm short-term power prediction method considering time evolution and space correlation
Technical Field
The invention belongs to the field of renewable energy power generation and comprehensive consumption, and particularly relates to a multi-wind-farm short-term power prediction method considering time evolution and space correlation.
Background
In recent years, the installed wind power capacity and the proportion of the installed wind power capacity on the power generation side in China are continuously increased, the wind power consumption and the wind abandon problem in large-scale wind power integration are increasingly highlighted due to the natural strong randomness and uncertainty of wind power. The accurate short-term wind power prediction can effectively deal with the inherent randomness and volatility of the wind power, and provides basis for the dispatching operation and the optimization decision of the power system, so that the safe and economic operation after large-scale wind power integration is ensured. Therefore, the research on the short-term wind power prediction technology has important practical significance.
At present, the research on wind power prediction is more and more intensive at home and abroad, and a prediction method system is continuously perfected and expanded. Compared with a single wind power plant, the power prediction of multiple wind power plants has the challenges of multidimensional input variables, complex space-time relation and mutual interleaving. Because the meteorological evolution process has space-time continuity, the wind speed or wind power between wind power plants in the region is closely related. The multi-wind power plant not only has a plurality of different time evolution modes, but also has spatial correlation among the different time evolution modes. The spatial and temporal correlation of the power of the multiple wind power plants is utilized to realize information sharing reciprocity, and the prediction precision and efficiency of the power of the multiple wind power plants can be effectively improved.
In the prior art, a deep learning method applied to multi-wind farm short-term power prediction mainly includes: convolutional Neural Network (CNN), recurrent Neural Network (RNN) and their variants, can be used for extraction of the temporal or spatial correlation of wind-power sequences. For example, an ultrashort-term wind power prediction method based on data driving and deep learning discloses: and extracting the space-time characteristics of the wind power plants by adopting a multi-scale convolution neural network and a GRU (generalized regression Unit), and mining the space-time correlation between adjacent wind power plants. However, in the short-term wind power prediction problem, factors influencing the prediction accuracy not only include the time sequence and spatial correlation of historical wind power data, but also include the potential periodic characteristics of wind power in the time evolution process, and under the combined action of wind processes with different time scales, the wind power sequence may contain periods with various time scales, but the prior art documents only consider the multi-periodicity of wind power places, and do not extract the periodic characteristics or only extract the single-period characteristics; in addition, most of the existing wind power prediction models including the model are static extraction of multi-wind-power-plant space correlation, and the difference and the dynamics of the multi-wind-power-plant power time evolution mode cannot be deeply excavated.
Disclosure of Invention
The method aims to introduce GRUs and multi-core convolution layers, and deeply excavate time sequence information and potential multi-period characteristics of a multi-wind power plant so as to extract a complete time evolution mode of a wind power sequence; meanwhile, a time-varying mode attention mechanism is adopted, the correlation of different time evolution modes of multiple spatial variables is dynamically noticed, and the accurate and effective prediction of the short-term power of the multiple wind power plants is realized.
The technical scheme of the invention is as follows:
a multi-wind-farm short-term power prediction method considering time evolution and space correlation comprises the following steps:
step 1: collecting prediction input data, and collecting historical power data and multi-dimensional meteorological prediction data of a plurality of wind power plants of a target wind power base in a small scale;
step 2: data preprocessing, namely respectively carrying out normalization operation on various data serving as input variables and output variables according to the characteristics of the data;
and step 3: the method comprises the steps of dividing a data set into a training set, a verification set and a test set, firstly, extracting wind power multi-periodicity characteristics by Fourier decomposition based on historical wind power data of the training set, and recording the period length T which is obvious 1 ,T 2 ,...,T u Determining the convolution kernel size of the multi-kernel convolution layer;
and 4, step 4: wind power at d historical moments before the forecasting moments of a plurality of wind power plants and meteorological data forecasting value normalized data at s forecasting moments form a multi-dimensional characteristic input variable, and a depth space-time fusion forecasting model is established by taking wind power values of the s forecasting moments of the plurality of wind power plants as output variables;
and 5: setting model hyper-parameters, initializing weight and bias, setting a loss function, training a deep space-time fusion network to obtain optimal weight and bias parameters, and searching the optimal hyper-parameters of an optimal model by using a grid through a verification set sample;
step 6: and inputting the test sample into a depth space-time fusion model with the optimal hyper-parameters, and performing inverse normalization on the output prediction result to obtain the power prediction result of the multi-wind-field at each moment of the prediction day.
In step 1, the acquired input data consists of l-dimensional known characteristics of n wind power plants at w moments before a prediction moment t, and X belongs to R n×w×l (ii) a For each wind farm there is an input vector x t =[P t-d ,P t-d+1 ,...,P t-1 ,Q t ,Q t+1 ,...,Q t+s-1 ]∈R l In which P is t-d ,P t-d+1 ,...,P t-1 Respectively the wind power, Q, of the previous d historical moments t ,Q t+1 ,...,Q t+s-1 And respectively the multi-dimensional meteorological forecast data of the next s forecast moments.
Step 2, respectively carrying out normalization processing on the wind power data and the meteorological data acquired in the step 1, wherein the power data are normalized to an interval [0,1 ] by taking the rated capacity of each wind power plant as a reference]Wind speed, temperature using the maximum and minimum normalization method, wind directionAdopting a sin/cos trigonometric function normalization method; the wind power before and after normalization is set as x 1 And
Figure BDA0003770852740000021
wind speed and temperature of x 2 And
Figure BDA0003770852740000022
wind direction data is x 3 And
Figure BDA0003770852740000023
the maximum value and the minimum value of the wind speed and the temperature sample are x respectively max 、x min Rated capacity of wind power is x N The specific normalization formula is as follows:
Figure BDA0003770852740000024
in step 3, based on actual measurement data of small-scale average total wind power of a plurality of wind power plants in a target area of a training set, fourier transform is carried out on the actual measurement data, an amplitude-frequency curve is drawn, the possible difference of periodic laws of wind power in different seasons is considered, multiple seasons and few seasons are divided according to the output characteristic of a wind turbine generator, the periodic laws of the seasons are respectively counted, the proportion of frequency components corresponding to points with larger amplitudes in the amplitude-frequency curve in an original sequence is larger, the frequency points are converted into periods according to sampling frequency, and the multi-period value T of the wind power can be obtained 1 ,T 2 ,…,T u This provides a reference for the subsequent setting of the hyper-parameters of the model.
Step 4, after input and output data are determined, a depth space-time fusion model is established, and the step 4 comprises the following substeps:
step 4.1: the depth space-time fusion model firstly sends an input matrix into a Gated Recurrent Unit (GRU), extracts the time sequence information of historical wind power data, and at time t, the GRU receives the current state x t And hidden state h at the previous moment t-1 Output of the network h t Formed by the dynamic control of the update gate and the reset gate. Definition and inputThe associated weight matrix W r ,W u ,W z (ii) a Weight matrix R associated with cyclic concatenation r ,R u ,R z Offset vector b r ,b u ,b z σ is sigmoid activation function, tanh is hyperbolic tangent function, which is a dot product. GRU firstly passes through the hidden state h at the last moment t-1 And input x of the current time t To obtain two gating states, where r t To reset the gate, z t To update the gate:
r t =σ(W r x t +R r h t-1 +b r )
z t =σ(W z x t +R z h t-1 +b z )
after obtaining the gating signal, the reset gating is used to obtain the hidden state after reset, then the hidden state is spliced with the input and the data range is [ -1,1 ] through the activation function tanh]To obtain
Figure BDA0003770852740000031
Figure BDA0003770852740000032
Then selectively forgetting the hidden state transmitted at the previous moment and selectively memorizing the hidden state information containing the current moment to obtain h t The update expression is:
Figure BDA0003770852740000033
step 4.2: through multi-core convolution layer pair, the hidden state matrix [ h ] obtained after GRU processing t-w+1 ,h t-w+2 ,...,h t-1 ]The row vectors of (a) are processed (w represents the time window length) to extract the multi-periodicity characteristics of the multi-wind farm. Firstly, carrying out convolution operation on row vectors of a hidden state matrix h in k channels by using convolution kernels with u sizes to obtain k different characteristic graphs f map The calculation formula is as follows:
Figure BDA0003770852740000034
where is the convolution operation, i denotes the ith row vector of the matrix h, concat denotes the feature concatenation operation, K denotes the convolution kernel, with the subscripts denoting the different sizes of the convolution kernel (T) 1 ,T 2 ,…,T u Representing the length of the convolution kernel, 1 representing the width of the convolution kernel) and a channel, and then downsampling (down) the feature map into several sub-blocks through a sliding window to obtain a new feature map f' map (k) In that respect The calculation formula is as follows:
Figure BDA0003770852740000035
in order to fuse the multi-channel and multi-size convolution operation characteristic diagram, the output vectors of the pooling layer are spliced in the channel direction to obtain
Figure BDA0003770852740000036
The calculation formula is as follows:
Figure BDA0003770852740000041
the last step of the multi-core convolutional layer is to linearly map the stitched feature map into a row vector H of a new state matrix H i The calculation formula is as follows:
Figure BDA0003770852740000042
W f and b f Representing the weights and biases of the mapping process.
Step 4.3: after the time sequence and multi-periodicity time evolution mode information of the wind power sequence is obtained through two steps of processing in steps 4.1 and 4.2, a time-varying mode attention mechanism is used for processing a new hidden state matrix H obtained through GRU and a multi-core convolution layer so as to extract related information of space variables with different time evolution modes, a scoring function f for evaluating the correlation is defined firstly, and the obtained attention weight is normalized, wherein the calculation formula is as follows:
f(H i ,h t )=(H i ) T W a h t
a i =σ(f(H i ,h t ))
wherein W a The weight matrix is obtained through neural network training, and sigma represents a sigmoid activation function; then, the ith row vector (containing time evolution mode information) in the hidden state matrix H and the obtained attention weight a i A weighted sum is performed, which is calculated as follows:
Figure BDA0003770852740000043
m represents the number of hidden layer neurons.
Step 4.4: finally integrating the characteristic vector v through a dropout layer and a full connection layer t And h t To obtain the final predicted result
Figure BDA0003770852740000044
The calculation formula is as follows:
h′ t =W h h t +W v dropout(v t )
Figure BDA0003770852740000045
W h ,W v ,W y and representing the corresponding weight matrix, which is also obtained by training the neural network.
Step 5, after the deep space-time fusion model is established in the step 4, setting hyper-parameters such as the number m of neurons, the length w of a sample time window, the number g of layers of a time sequence network GRU, the number k of multi-core convolution layer channels and the size of convolution kernels; initializing weight and bias, selecting a training sample, taking a mean square error as a loss function, and training a model by adopting an Adam optimization algorithm to obtain optimal weight and bias parameters; then inputting the sample of the verification set into the trained deep space-time fusion model, and optimizing the optimal hyper-parameters of the model according to verification errors by adopting grid search, wherein the optimization ranges of some main hyper-parameters are as follows: the number of neurons m {16,32,64,100,128,200,300}; the convolution channel number k is {16,24,32,48}; the number of layers g of the time sequence network is 1,2, 3.
Step 6, inputting the test sample into a depth space-time fusion model with the optimal hyper-parameters, and performing inverse normalization on the output prediction result to obtain the power prediction result of each wind power plant at each moment of the prediction day
Figure BDA0003770852740000046
Wherein n is the number of wind farms and s is a time step predicted later.
Compared with the prior art, the invention has the beneficial effects that:
1) The method considers the time evolution and space related information of multiple wind power plants, simultaneously outputs short-term power prediction results of the multiple wind power plants and multiple time steps, is favorable for realizing grid-connected operation of large-scale wind power data, and has positive influence on the safe and stable operation of a power grid;
2) The method deeply excavates the potential multi-period characteristics of the multi-wind power plant, and combines the extracted multi-period multi-core convolutional layer with the GRU unit for capturing the time sequence dependency relationship, so that the model has the capability of learning the complete time evolution rule of the multi-wind power plant;
3) According to the method, a time-varying mode attention mechanism is introduced, the spatial correlation of multiple wind power plants and multiple time-varying modes is dynamically extracted along with the time, the defect that the spatial dependency of the existing multiple models is extracted statically is overcome, and the prediction stability is enhanced;
4) The practical calculation result shows that the method is reasonable in structure, good in performance on the practical wind power data set, and better in prediction accuracy and robustness compared with the current other hot prediction models.
5) The method not only completely considers the time sequence and periodic time evolution modes of the wind power sequence, but also dynamically takes the spatial correlation information of various time evolution modes of different spatial variables into account, thereby dynamically calculating the spatial correlation of multiple wind power plants; and finally, outputting the power predicted value of each moment of the multi-wind-farm predicted day which simultaneously meets the requirements of time sequence, periodicity and spatial correlation.
Drawings
FIG. 1 is a multi-wind farm short-term power prediction process based on a deep space-time fusion model.
Fig. 2 is a fourier transform amplitude-frequency diagram.
FIG. 3 is a schematic diagram of a gated cycle cell.
FIG. 4 is a diagram illustrating a multi-core convolution operation.
FIG. 5 is a comparison graph of No. 3 wind power plant prediction curve and actual curve in the embodiment of the invention
FIG. 6 is a MAPE error comparison graph (%)
FIG. 7 is an RMSE error comparison graph (MW) of prediction results of different prediction methods of 18 wind power plants in the embodiment of the invention
FIG. 8 is a comparison graph of prediction errors for different cycle characteristics according to an embodiment of the present invention.
Detailed description of the preferred embodiments
The invention provides a multi-wind-farm short-term power prediction framework based on a deep space-time fusion network, which comprises an input module, a time evolution mode tracking module, a space correlation mode attention module and an output module. The input module is used for collecting and preprocessing data, and the objects are historical power data and meteorological prediction data of a multi-wind farm in a target area; the time evolution mode tracking module respectively extracts a time sequence and a multi-periodicity time evolution mode of historical wind power data through the gated circulation unit and the multi-core convolution layer; the spatial correlation mode attention module introduces a time-varying mode attention mechanism to endow correlation weights to different time evolution modes of multiple spatial variables, and can realize transverse comparison of the different time evolution modes of the multiple spatial variables while longitudinally tracking a time evolution rule; and finally, the output module outputs the multi-wind-farm power day-ahead prediction scene which simultaneously meets the requirements of time sequence, periodicity and spatial correlation.
As shown in fig. 1, the method for predicting the short-term power of multiple wind farms based on the deep space-time fusion model includes the following steps:
step 1: acquiring hour-level historical power data and external meteorological information data of a plurality of target wind power plants in a target area, wherein original input data are composed of l-dimensional known characteristics of n wind power plants at w moments before a prediction moment t, and X belongs to R n×w×l . For each wind farm there is an input vector x t =[P t-d ,P t-d+1 ,...,P t-1 ,Q t ,Q t+1 ,...,Q t+s-1 ]∈R l In which P is t-d ,P t-d+1 ,...,P t-1 Respectively the wind power, Q, of the previous d historical moments t ,Q t+1 ,...,Q t+s-1 Multi-dimensional meteorological forecast data (such as wind speed, wind direction and air temperature) of the last s forecast moments respectively;
step 2: carrying out normalization processing on the wind power data and the meteorological data acquired in the step 1, wherein the power data are normalized to an interval [0,1 ] by taking the rated capacity of each wind power plant as a reference]Wind speed and temperature adopt a maximum and minimum normalization mode, and wind direction adopts a sin/cos trigonometric function normalization method; the wind power before and after normalization is set as x 1 And
Figure BDA0003770852740000061
wind speed and temperature of x 2 And
Figure BDA0003770852740000062
wind direction data is x 3 And
Figure BDA0003770852740000063
the maximum and minimum values of the wind speed and the temperature sample are x respectively max 、x min Rated capacity of wind power is x N The specific normalization formula is as follows:
Figure BDA0003770852740000064
Figure BDA0003770852740000065
Figure BDA0003770852740000066
and step 3: dividing input data into a training set, a verification set and a test set according to the proportion of 80%, 10% and 10%, performing Fourier transform on actual measurement data of the small-scale average total wind power of a plurality of wind power plants in a target area based on the training set, and drawing an amplitude-frequency curve as shown in FIG. 2. Considering that the periodic laws of wind power in different seasons may have differences, dividing multiple seasons and few seasons according to the output characteristics of the wind turbine generator and respectively counting the periodic laws, wherein the frequency component corresponding to the point with the larger amplitude in the amplitude-frequency curve occupies a larger proportion in the original sequence, and converting the frequency points into the period according to the sampling frequency to obtain the multi-period value T of the wind power 1 ,T 2 ,…,T u This provides a reference for the setting of the model hyper-parameters (multi-kernel convolution kernel size) afterwards;
and 4, step 4: starting to build a deep spatiotemporal fusion model after determining the input and output data, said step 4 comprises the following sub-steps:
step 4.1: the deep space-time fusion model firstly sends an input matrix into a GRU (generalized regression Unit), extracts time sequence information of historical wind power data, and at time t, the GRU receives a current state x t And hidden state h at the previous moment t-1 Output of the network h t Formed by the dynamic control of the update gate and the reset gate. Defining an input-dependent weight matrix W r ,W u ,W z (ii) a Weight matrix R associated with cyclic concatenation r ,R u ,R z Offset vector b r ,b u ,b z σ is sigmoid activation function, tanh is hyperbolic tangent function, which is a dot product. GRU firstly passes through the hidden state h at the last moment t-1 And input x at the current time t To obtain two gating states, where r t To reset the gate, z t To update the door:
r t =σ(W r x t +R r h t-1 +b r )
z t =σ(W z x t +R z h t-1 +b z )
after obtaining the gating signal, the reset gating is used to obtain the reset hidden state, and then the hidden state is spliced with the input and the data range is [ -1,1 ] by activating the function tanh]To obtain
Figure BDA0003770852740000067
Figure BDA0003770852740000068
Then selectively forgetting the hidden state transmitted at the previous moment and selectively memorizing the hidden state information containing the current moment to obtain h t The update expression is:
Figure BDA0003770852740000071
step 4.2: through the multi-core convolution layer pair, the hidden state matrix [ h ] obtained after GRU processing t-w+1 ,h t-w+2 ,...,h t-1 ]The row vectors of (a) are processed (w represents the time window length) to extract the multi-periodicity characteristics of the multi-wind farm. Firstly, convolution operation is carried out on row vectors of a hidden state matrix h in k channels by using convolution cores with u sizes to obtain k different characteristic diagrams f map The calculation formula is as follows:
Figure BDA0003770852740000072
where is the convolution operation, i denotes the ith row vector of the matrix h, concat denotes the feature concatenation operation, K denotes the convolution kernel, with the subscripts denoting the different sizes of the convolution kernel (T) 1 ,T 2 ,…,T u Representing the length of the convolution kernel, 1 representing the width of the convolution kernel) and a channel, and then downsampling (down) the feature map into several sub-blocks through a sliding window to obtain a new feature map f' map (k) .1. The The calculation formula is as follows:
Figure BDA0003770852740000073
in order to fuse the multi-channel and multi-size convolution operation characteristic diagram, the output vectors of the pooling layer are spliced in the channel direction to obtain
Figure BDA0003770852740000074
The calculation formula is as follows:
Figure BDA0003770852740000075
the last step of the multi-core convolutional layer is to linearly map the stitched feature map into a row vector H of a new state matrix H i The calculation formula is as follows:
Figure BDA0003770852740000076
W f and b f Representing the weights and biases of the mapping process.
Step 4.3: after the time evolution mode information of the wind power sequence is obtained through the two steps of processing in the steps 4.1 and 4.2, a time-varying mode attention mechanism is used for processing a new hidden state matrix H obtained through the GRU and the multi-core convolution layer so as to extract related information of space variables with different time evolution modes. Firstly, defining a scoring function f for evaluating the correlation, and carrying out normalization operation on the obtained attention weight, wherein the calculation formula is as follows:
f(H i ,h t )=(H i ) T W a h t
a i =σ(f(H i ,h t ))
wherein W a The weight matrix is obtained by neural network training, and sigma represents a sigmoid activation function; then, the ith row vector (containing time evolution mode information) in the hidden state matrix H and the obtained attention weight a i A weighted sum is performed, which is calculated as follows:
Figure BDA0003770852740000081
m represents the number of hidden layer neurons.
Step 4.4: finally integrating the characteristic vector v through a dropout layer and a full connection layer t And h t To obtain the final predicted result
Figure BDA0003770852740000082
The calculation formula is as follows:
h′ t =W h h t +W v dropout(v t )
Figure BDA0003770852740000083
W h ,W v ,W y and representing the corresponding weight matrix, which is also obtained by training the neural network.
And 5: setting hyper-parameters such as the number m of neurons, the length w of a sample time window, the number g of the layers of a time sequence network GRU, the number k of multi-core convolution layer channels and the size of a convolution kernel after the deep space-time fusion model is established; initializing weight and bias, selecting a training sample, taking a mean square error as a loss function, and training the model by adopting an Adam optimization algorithm to obtain optimal weight and bias parameters; inputting the sample of the verification set into a trained deep space-time fusion model, and optimizing the optimal hyper-parameters of the model according to verification errors by adopting grid search, wherein the optimization ranges of some main hyper-parameters are as follows: the number of neurons m {16,32,64,100,128,200,300}; the convolution channel number k is {16,24,32,48}; the number of time sequence network layers g is {1,2,3};
step 6: will measureInputting the sample book into a depth space-time fusion model with optimal hyper-parameters, and performing inverse normalization on the output prediction result to obtain the power prediction result of each wind power plant at each moment of the prediction day
Figure BDA0003770852740000084
Wherein n is the number of wind farms and s is the time step predicted later.
In this embodiment, the hourly actual measurement power data of 18 wind power plants 2016 of a domestic target wind power base is used as an analysis object, the input of the prediction model is the hourly historical wind power one week ahead of time and the meteorological prediction data (including predicted values of wind speed, wind direction and air temperature per hour) of a prediction day, and the multi-wind-plant power prediction result of the next 24 hours is output. The present embodiment uses the Mean Absolute Percentage Error (MAPE) and the Root Mean Square Error (RMSE) to evaluate the prediction accuracy, and their calculation formula is as follows:
Figure BDA0003770852740000085
Figure BDA0003770852740000086
in the formula: n is the number of test samples; y is i And
Figure BDA0003770852740000087
and respectively predicting the actual value and the predicted value of the wind power of the ith sampling point on the day.
Fig. 5 is a comparison graph of a predicted curve and an actual curve of a wind farm 9 in the embodiment of the present invention, which shows that the method of the present invention performs best in the wind farm and simulates a fluctuation trend of wind power more accurately. And simultaneously has smaller overall error and smaller single-point prediction error. Fig. 6 and 7 are a MAPE error comparison graph and an RMSE error comparison graph of prediction results of different prediction methods for 18 wind farms according to an embodiment of the present invention, respectively, and it can be seen that the method of the present invention has the best prediction accuracy for prediction of the day-ahead wind power. Compared with time sequence neural networks such as TCN, GRU and LSTM, the average improvement rate of MAPE (Imp) of DSTFM is 9.99%, 8.80% and 7.87%, respectively, which shows that only considering the time sequence characteristics of wind power is not enough, and the spatial correlation between a complete time evolution mode and a multi-wind farm needs to be considered. The GRU-CNN is added with a convolution kernel capable of extracting input space characteristics, so that the model has the capability of extracting space-time information, compared with the model, the MAPE average value of the DSTFM is reduced by 5.17%, and the effectiveness of dynamically capturing the space correlation of multiple wind fields and multiple time-varying modes by applying a time-varying mode attention mechanism is reflected. It can also be seen from fig. 6 that MAPE of each model shows difference in different wind farms due to different geographical locations of the multiple wind farms. The MAPE for all models at wind farms No. 4 and 8 is relatively large, indicating that these two windfarms have poor predictability of power. Nevertheless, DSTFM still maintains strong robustness to a plurality of wind farms with different predictability.
FIG. 8 is a comparison graph of the influence of different periodic characteristics of wind power on the prediction result, and three schemes of not considering the periodic characteristics, only considering a single period and considering multi-period combination are compared. The prediction error of the multicycle combination DSTFM model is minimum, and the MAPE error is reduced by 0.75% compared with the period without consideration, which indicates the necessity of taking the periodicity of the wind power data into consideration. Compared with 3 models only considering the monocycle characteristics, the MAPE improvement rate of the model is 0.51%, 0.40% and 0.57% respectively in the cases of 24h, 38h and 80 h. Although the prediction error of the monocycle model is lower than that of a model without introducing the cycle characteristic, the improvement effect is limited. And the stability of the model has a decline potential along with the period extension, which shows that the sensitivity of the model to the time evolution mode change in the period range is poor when the period is longer. And the multi-period combination model can give consideration to the sensitivity to different long and short period characteristics, so that higher prediction accuracy can be obtained.

Claims (7)

1. The method for predicting the short-term power of the multiple wind farms by considering time evolution and space correlation is characterized by comprising the following steps of:
step 1: collecting prediction input data, and collecting historical power data and multi-dimensional meteorological prediction data of a plurality of wind power plants of a target wind power base in a small scale;
step 2: data preprocessing, namely respectively carrying out normalization operation on various data serving as input variables and output variables according to the characteristics of the data;
and 3, step 3: the method comprises the steps of dividing a data set into a training set, a verification set and a test set, firstly, extracting wind power multi-periodicity characteristics based on historical wind power data of the training set by means of Fourier decomposition, and recording the period length T which is obvious 1 ,T 2 ,...,T u Determining the convolution kernel size of the multi-kernel convolution layer;
and 4, step 4: wind power at d historical moments before the forecasting moments of a plurality of wind power plants and meteorological data forecasting value normalized data at s forecasting moments form a multi-dimensional characteristic input variable, and a depth space-time fusion forecasting model is established by taking wind power values of the s forecasting moments of the plurality of wind power plants as output variables;
and 5: setting model hyper-parameters, initializing weight and bias, setting a loss function, training a deep space-time fusion network to obtain optimal weight and bias parameters, and searching the optimal hyper-parameters of an optimal model by using a grid through a verification set sample;
step 6: and inputting the test sample into a depth space-time fusion model with the optimal hyper-parameters, and performing inverse normalization on the output prediction result to obtain the power prediction result of the multi-wind-field at each moment of the prediction day.
2. The method of claim 1, wherein: in step 1, the acquired input data consists of l-dimensional known characteristics of n wind power plants at w moments before a prediction moment t, and X belongs to R n×w×l (ii) a For each wind farm there is an input vector x t =[P t-d ,P t-d+1 ,...,P t-1 ,Q t ,Q t+1 ,...,Q t+s-1 ]∈R l In which P is t-d ,P t-d+1 ,...,P t-1 Respectively the wind power, Q, of the previous d historical moments t ,Q t+1 ,...,Q t+s-1 And respectively the multi-dimensional meteorological forecast data of the next s forecast moments.
3. The method of claim 1, wherein: step 2, respectively carrying out normalization processing on the wind power data and the meteorological data acquired in the step 1, wherein the power data are normalized to an interval [0,1 ] by taking the rated capacity of each wind power plant as a reference]Wind speed and temperature adopt a maximum and minimum normalization mode, and wind direction adopts a sin/cos trigonometric function normalization method; the wind power before and after normalization is set as x 1 And
Figure FDA0003770852730000011
wind speed, temperature x 2 And
Figure FDA0003770852730000012
wind direction data is x 3 And
Figure FDA0003770852730000013
the maximum value and the minimum value of the wind speed and the temperature sample are x respectively max 、x min Rated capacity of wind power is x N The specific normalization formula is as follows:
Figure FDA0003770852730000014
4. the method of claim 1, wherein: in step 3, based on actual measurement data of the small-scale average total wind power of a plurality of wind power plants in a target area of a training set, fourier transform is carried out on the actual measurement data, an amplitude-frequency curve is drawn, the possible difference of periodic laws of wind power in different seasons is considered, multiple seasons and few seasons are divided according to the output characteristics of the wind power generation set, the periodic laws are respectively counted, the occupation ratio of frequency components corresponding to points with larger amplitudes in the amplitude-frequency curve in an original sequence is larger, the frequency points are converted into periods according to sampling frequency, and the multi-period value T of the wind power can be obtained 1 ,T 2 ,…,T u This provides a reference for the subsequent setting of the hyper-parameters of the model.
5. The method of claim 1, wherein: step 4, after input and output data are determined, a depth space-time fusion model is established, and the step 4 comprises the following substeps:
step 4.1: the deep space-time fusion model firstly sends an input matrix into a Gated Recurrent Unit (GRU), extracts time sequence information of historical wind power data, and the GRU receives a current state x at a time t t And hidden state h at the previous moment t-1 Output of the network h t Formed by dynamic control of the update gates and reset gates, defining a weight matrix W associated with the inputs r ,W u ,W z (ii) a Weight matrix R associated with cyclic concatenation r ,R u ,R z Offset vector b r ,b u ,b z σ is sigmoid activation function, tanh is hyperbolic tangent function, Δ is dot product, GRU passes through hidden state h at the previous moment t-1 And input x of the current time t To obtain two gating states, where r t To reset the gate, z t To update the gate:
r t =σ(W r x t +R r h t-1 +b r )
z t =σ(W z x t +R z h t-1 +b z )
after obtaining the gating signal, the reset gating is used to obtain the reset hidden state, and then the hidden state is spliced with the input and the data range is [ -1,1 ] by activating the function tanh]To obtain
Figure FDA0003770852730000021
Figure FDA0003770852730000022
Then selectively forget the hidden state transferred at the previous moment and selectively carry out hidden state information containing the current momentMemorize to obtain h t The update expression is:
Figure FDA0003770852730000023
step 4.2: through the multi-core convolution layer pair, the hidden state matrix [ h ] obtained after GRU processing t-w+1 ,h t-w+2 ,...,h t-1 ]In order to extract the multi-periodicity characteristics of the multi-wind power plant, firstly convolution operation is carried out on the row vectors of a hidden state matrix h in k channels by using convolution kernels with u sizes to obtain k different characteristic diagrams f map The calculation formula is as follows:
Figure FDA0003770852730000024
where is the convolution operation, i denotes the ith row vector of the matrix h, concat denotes the feature concatenation operation, K denotes the convolution kernel, with the subscripts denoting the different sizes and channels of the convolution kernel, specifically T 1 ,T 2 ,…,T u Represents the length of the convolution kernel, and 1 represents the width of the convolution kernel; then, a plurality of sub-blocks divided by the feature map are subjected to down-sampling operation through a sliding window, namely down operation in the following formula, so as to obtain a new feature map f map (k) The calculation formula is as follows:
Figure FDA0003770852730000031
in order to fuse multi-channel and multi-size convolution operation characteristic graphs, output vectors of the pooling layer are spliced in the channel direction to obtain
Figure FDA0003770852730000032
The calculation formula is as follows:
Figure FDA0003770852730000033
the last step of the multi-core convolutional layer is to linearly map the stitched feature map into a row vector H of a new state matrix H i The calculation formula is as follows:
Figure FDA0003770852730000034
W f and b f Weights and biases representing the mapping process;
step 4.3: after the time sequence and multi-periodicity time evolution mode information of the wind power sequence is obtained through two steps of processing in steps 4.1 and 4.2, a time-varying mode attention mechanism is used for processing a new hidden state matrix H obtained through GRU and a multi-core convolution layer so as to extract related information of space variables with different time evolution modes, a scoring function f for evaluating the correlation is defined firstly, and the obtained attention weight is normalized, wherein the calculation formula is as follows:
f(H i ,h t )=(H i ) T W a h t
a i =σ(f(H i ,h t ))
wherein W a The weight matrix is obtained through neural network training, and sigma represents a sigmoid activation function; then, the ith row vector containing time evolution mode information in the hidden state matrix H and the obtained attention weight a i A weighted sum is performed, which is calculated as follows:
Figure FDA0003770852730000035
m represents the number of hidden layer neurons;
step 4.4: finally integrating the characteristic vector v through a dropout layer and a full connection layer t And h t To obtain the final prediction result
Figure FDA0003770852730000038
The calculation formula is as follows:
Figure FDA0003770852730000036
Figure FDA0003770852730000037
W h ,W v ,W y and representing the corresponding weight matrix, which is also obtained by training the neural network.
6. The method of claim 1, wherein: step 5, after the deep space-time fusion model is established in the step 4, setting hyper-parameters such as the number m of neurons, the length w of a sample time window, the number g of layers of a time sequence network GRU, the number k of multi-core convolution layer channels and the size of convolution kernels; initializing weight and bias, selecting a training sample, taking a mean square error as a loss function, and training the model by adopting an Adam optimization algorithm to obtain optimal weight and bias parameters; inputting the sample of the verification set into a trained deep space-time fusion model, and optimizing the optimal hyper-parameters of the model according to verification errors by adopting grid search, wherein the optimization ranges of some main hyper-parameters are as follows: the number of neurons m {16,32,64,100,128,200,300}; the convolution channel number k is {16,24,32,48}; the number of layers g of the time sequence network is 1,2, 3.
7. The method of claim 1, wherein: step 6, inputting the test sample into a depth space-time fusion model with the optimal hyper-parameters, and performing inverse normalization on the output prediction result to obtain the power prediction result of each wind power plant at each moment of the prediction day
Figure FDA0003770852730000041
Wherein n is the number of wind farms and s is the time step predicted later.
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