基于MKL方法的短期風電功率預測研究
發(fā)布時間：2018-11-22 13:31
【摘要】：支持向量機(Support Vector Machine,SVM)等核學習方法是解決非線性問題的一種有效方法,在短期風電功率預測中已有成功的應用。多核學習(Multiple Kernel Learning,MKL)作為一種的新型核學習方法,通過核權(quán)值系數(shù)將具有不同特性的核函數(shù)進行組合,其核權(quán)值系數(shù)使得核函數(shù)的選擇問題轉(zhuǎn)化為核權(quán)值系數(shù)的分布問題,且核權(quán)值系數(shù)的稀疏性能增強決策函數(shù)可解釋性,其不同核函數(shù)組合形成的再生希爾伯特空間使模型具有更強的泛化能力與魯棒性。為了進一步提高短期風電功率預測模型的性能,以MKL方法為主線,研究其在短期風電功率直接預測與間接預測方面的應用。本文的主要研究內(nèi)容如下:(1)分析了用于數(shù)據(jù)預處理的經(jīng)驗模態(tài)分解方法(Empirical Mode Decomposition,EMD)和經(jīng)驗小波變換方法(Empirical Wavelet Transform,EWT)的基本原理及其實現(xiàn)步驟,并通過ECG(Electrocardiograph,心電圖)標準數(shù)據(jù)集對其進行對比分析,實驗結(jié)果表明,EWT分解得到模態(tài)信號分量數(shù)量明顯少于EMD得到的模態(tài)信號分量數(shù)量且EMD分解得到的模態(tài)分量存在明顯的模態(tài)混疊現(xiàn)象。在SVM理論的基礎(chǔ)上,對基于半無限線性規(guī)劃的多核學習及MKL-wrapper算法和MKL-chunking算法進行了深入研究,并簡要闡述了Simple MKL方法的基本原理及其具體實現(xiàn)步驟。(2)分析了某大型風電場輸出功率不同季節(jié)中的季節(jié)周期性和時間連續(xù)性的特點,并從不同季節(jié)中隨機選取四個具有不同特性測試周的風電功率數(shù)據(jù)作為測試集;將自適應分解預處理方法EWT與由MKL-wrapper、MKL-chunking、Simple MKL算法實現(xiàn)的MKL方法結(jié)合,形成一種新的組合預測方法,即EWT-MKL方法;將不同MKL方法應用于不同季節(jié)的短期風電功率直接預測實例中,在同等條件下,并與SVM方法進行對比。實驗結(jié)果表明,MKL預測模型的精度優(yōu)于SVM方法,而不同算法實現(xiàn)的EWT-MKL組合預測模型的效果最好,不同季節(jié)測試集中MKL模型的核參數(shù)及懲罰函數(shù)在取值范圍內(nèi)的隨機取值及其實驗結(jié)果表明,MKL具有較強的泛化能力且其對參數(shù)的選擇具有較強的魯棒性。(3)分析了不同“風速-功率”特性曲線求解方法對風速-功率轉(zhuǎn)換精度的影響;將不同算法實現(xiàn)的MKL預測方法及EWT-MKL組合預測方法應用于某風電場平均風速的短期預測;結(jié)合“風速-功率”特性曲線實現(xiàn)短期風電功率間接預測,并在同等條件下與小波支持向量機(Wavelet Support Vector Machines,WSVM)方法進行對比。實驗結(jié)果表明,在短期風電功率間接預測中,不同算法實現(xiàn)的EWT-MKL組合預測模型的精度明顯高于MKL、SVM及WSVM等方法,而MKL預測模型的精度優(yōu)于SVM方法建立的預測模型。
[Abstract]:Support Vector Machine (Support Vector Machine,SVM) is an effective method to solve nonlinear problems and has been successfully applied in short-term wind power prediction. As a new kernel learning method, multi-kernel learning (Multiple Kernel Learning,MKL) combines kernel functions with different characteristics through kernel weight coefficients, and the kernel weight coefficients transform the selection of kernel functions into the distribution of kernel weight coefficients. The sparse property of the kernel weight coefficient enhances the interpretability of the decision function, and the reproducing Hilbert space formed by the combination of different kernel functions makes the model have stronger generalization ability and robustness. In order to further improve the performance of short-term wind power prediction model, the application of MKL method in direct and indirect prediction of short-term wind power is studied. The main contents of this paper are as follows: (1) the basic principle and implementation steps of empirical mode decomposition (Empirical Mode Decomposition,EMD) and empirical wavelet transform (Empirical Wavelet Transform,EWT) for data preprocessing are analyzed. The experimental results show that the number of modal signal components obtained by EWT decomposition is obviously less than that obtained by EMD, and the modal components obtained by EMD decomposition have obvious modal aliasing phenomenon. On the basis of SVM theory, the multi-core learning based on semi-infinite linear programming, MKL-wrapper algorithm and MKL-chunking algorithm are studied. The basic principle of Simple MKL method and its realization steps are briefly described. (2) the characteristics of seasonal periodicity and time continuity in different seasons of output power of a large wind farm are analyzed. Four wind power data with different characteristic test weeks were randomly selected from different seasons as the test set. Combining the adaptive decomposition preprocessing method (EWT) with the MKL method realized by MKL-wrapper,MKL-chunking,Simple MKL algorithm, a new combined prediction method, EWT-MKL method, is formed. The different MKL method is applied to the direct prediction of short-term wind power in different seasons. Under the same conditions, the method is compared with the SVM method. The experimental results show that the precision of MKL prediction model is better than that of SVM method, and the effect of EWT-MKL combination prediction model realized by different algorithms is the best. The random values of the kernel parameters and penalty functions of the MKL model in different season test sets are obtained in the range of values and the experimental results show that, MKL has strong generalization ability and strong robustness to parameter selection. (3) the influence of different "wind speed power" characteristic curve solving method on the precision of wind speed power conversion is analyzed. The MKL forecasting method and the EWT-MKL combination forecasting method realized by different algorithms are applied to the short-term prediction of the average wind speed of a wind farm. Combined with the characteristic curve of "wind speed and power", indirect prediction of short-term wind power is realized, and compared with wavelet support vector machine (Wavelet Support Vector Machines,WSVM) method under the same conditions. The experimental results show that the accuracy of EWT-MKL combination prediction model implemented by different algorithms is obviously higher than that of MKL,SVM and WSVM methods in indirect prediction of short-term wind power, while the accuracy of MKL prediction model is better than that of SVM method.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM614
[Abstract]:Support Vector Machine (Support Vector Machine,SVM) is an effective method to solve nonlinear problems and has been successfully applied in short-term wind power prediction. As a new kernel learning method, multi-kernel learning (Multiple Kernel Learning,MKL) combines kernel functions with different characteristics through kernel weight coefficients, and the kernel weight coefficients transform the selection of kernel functions into the distribution of kernel weight coefficients. The sparse property of the kernel weight coefficient enhances the interpretability of the decision function, and the reproducing Hilbert space formed by the combination of different kernel functions makes the model have stronger generalization ability and robustness. In order to further improve the performance of short-term wind power prediction model, the application of MKL method in direct and indirect prediction of short-term wind power is studied. The main contents of this paper are as follows: (1) the basic principle and implementation steps of empirical mode decomposition (Empirical Mode Decomposition,EMD) and empirical wavelet transform (Empirical Wavelet Transform,EWT) for data preprocessing are analyzed. The experimental results show that the number of modal signal components obtained by EWT decomposition is obviously less than that obtained by EMD, and the modal components obtained by EMD decomposition have obvious modal aliasing phenomenon. On the basis of SVM theory, the multi-core learning based on semi-infinite linear programming, MKL-wrapper algorithm and MKL-chunking algorithm are studied. The basic principle of Simple MKL method and its realization steps are briefly described. (2) the characteristics of seasonal periodicity and time continuity in different seasons of output power of a large wind farm are analyzed. Four wind power data with different characteristic test weeks were randomly selected from different seasons as the test set. Combining the adaptive decomposition preprocessing method (EWT) with the MKL method realized by MKL-wrapper,MKL-chunking,Simple MKL algorithm, a new combined prediction method, EWT-MKL method, is formed. The different MKL method is applied to the direct prediction of short-term wind power in different seasons. Under the same conditions, the method is compared with the SVM method. The experimental results show that the precision of MKL prediction model is better than that of SVM method, and the effect of EWT-MKL combination prediction model realized by different algorithms is the best. The random values of the kernel parameters and penalty functions of the MKL model in different season test sets are obtained in the range of values and the experimental results show that, MKL has strong generalization ability and strong robustness to parameter selection. (3) the influence of different "wind speed power" characteristic curve solving method on the precision of wind speed power conversion is analyzed. The MKL forecasting method and the EWT-MKL combination forecasting method realized by different algorithms are applied to the short-term prediction of the average wind speed of a wind farm. Combined with the characteristic curve of "wind speed and power", indirect prediction of short-term wind power is realized, and compared with wavelet support vector machine (Wavelet Support Vector Machines,WSVM) method under the same conditions. The experimental results show that the accuracy of EWT-MKL combination prediction model implemented by different algorithms is obviously higher than that of MKL,SVM and WSVM methods in indirect prediction of short-term wind power, while the accuracy of MKL prediction model is better than that of SVM method.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TM614
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