1 简介
一种基于原子搜索算法优化BP神经网络的风电功率预测方法,从风电功率预测系统的数据处理模块中获取预测参考数据;对参考数据建立BP神经网络的预测模型,并采用多种群编码对应BP神经网络的不同结构,每个种群分别对神经网络权值阈值编码,生成不同长度的个体,用遗传算法中选择,交叉,变异操作进化优化每个种群,最后判断收敛条件并选择最优个体;再对BP神经网络初始化,用学习率可变的动量BP算法进一步训练网络直至收敛,利用该网络对风电功率进行预测;最后,还反复利用预测值,在一轮预测中进行多次预测实现了跨时间间隔的多步预测.本发明预测精度提高,计算时间减少,稳定性增强.
具体模型参考底下文献。
2 部分代码
%--------------------------------------------------------------------------
% GSA code v1.0.
%--------------------------------------------------------------------------
% Atom Search Optimization.
function [X_Best,Fit_XBest,Functon_Best]=ASO(alpha,beta,Fun_Index,Atom_Num,Max_Iteration)
% Dim: Dimension of search space.
% Atom_Pop: Population (position) of atoms.
% Atom_V: Velocity of atoms.
% Acc: Acceleration of atoms.
% M: Mass of atoms.
% Atom_Num: Number of atom population.
% Fitness: Fitness of atoms.
% Max_Iteration: Maximum of iterations.
% X_Best: Best solution (position) found so far.
% Fit_XBest: Best result corresponding to X_Best.
% Functon_Best: The fitness over iterations.
% Low: The low bound of search space.
% Up: The up bound of search space.
% alpha: Depth weight.
% beta: Multiplier weight
alpha=50;
beta=0.2;
Iteration=1;
[Low,Up,Dim]=Test_Functions_Range(Fun_Index);
% Randomly initialize positions and velocities of atoms.
if size(Up,2)==1
Atom_Pop=rand(Atom_Num,Dim).*(Up-Low)+Low;
Atom_V=rand(Atom_Num,Dim).*(Up-Low)+Low;
end
if size(Up,2)>1
for i=1:Dim
Atom_Pop(:,i)=rand(Atom_Num,1).*(Up(i)-Low(i))+Low(i);
Atom_V(:,i)=rand(Atom_Num,1).*(Up(i)-Low(i))+Low(i);
end
end
% Compute function fitness of atoms.
for i=1:Atom_Num
Fitness(i)=Test_Functions(Atom_Pop(i,:),Fun_Index,Dim);
end
Functon_Best=zeros(Max_Iteration,1);
[Max_Fitness,Index]=min(Fitness);
Functon_Best(1)=Fitness(Index);
X_Best=Atom_Pop(Index,:);
% Calculate acceleration.
Atom_Acc=Acceleration(Atom_Pop,Fitness,Iteration,Max_Iteration,Dim,Atom_Num,X_Best,alpha,beta);
% Iteration
for Iteration=2:Max_Iteration
Functon_Best(Iteration)=Functon_Best(Iteration-1);
Atom_V=rand(Atom_Num,Dim).*Atom_V+Atom_Acc;
Atom_Pop=Atom_Pop+Atom_V;
for i=1:Atom_Num
% Relocate atom out of range.
TU= Atom_Pop(i,:)>Up;
TL= Atom_Pop(i,:)<Low;
Atom_Pop(i,:)=(Atom_Pop(i,:).*(~(TU+TL)))+((rand(1,Dim).*(Up-Low)+Low).*(TU+TL));
%evaluate atom.
Fitness(i)=Test_Functions(Atom_Pop(i,:),Fun_Index,Dim);
end
[Max_Fitness,Index]=min(Fitness);
if Max_Fitness<Functon_Best(Iteration)
Functon_Best(Iteration)=Max_Fitness;
X_Best=Atom_Pop(Index,:);
else
r=fix(rand*Atom_Num)+1;
Atom_Pop(r,:)=X_Best;
end
% Calculate acceleration.
Atom_Acc=Acceleration(Atom_Pop,Fitness,Iteration,Max_Iteration,Dim,Atom_Num,X_Best,alpha,beta);
end
Fit_XBest=Functon_Best(Iteration);
3 仿真结果
4 参考文献
[1]苑严伟, 张小超, & 毛文华. (2009). 基于bp模型的蝗虫密度预测系统的研究. 农机化研究(5), 5.
[2]陈天恩, 陈皓勇, 张浩, 陈盼, 侯荆州, & 叶荣. 一种基于遗传算法优化bp神经网络的风电功率预测方法. CN, CN101706335 A.
