function ddg=func_ddg(PGi,PVi,Busnum,RestraintCount,Loadi,PD,QD)

ddg1=sparse(size(PVi,1)+size(PGi,1)+Loadi*2+Busnum,RestraintCount);
t1=sparse(length(Loadi),size(PVi,1)+size(PGi,1)+Busnum)
ddg2=sparse(length(Loadi),diag(-2./PD.^2-2*(QD.^2-PD.^2)/(PD.^2+QD.^2)));
ddg3=diag(2*(PD.^2-QD.^2)/(PD.^2+QD.^2));
ddg4=sparse(Busnum,RestraintCount);
ddg=[ddg1;ddg2;ddg3;ddg4];
end