function [Y,Z,Gt,Bt]=Trans2Model(para_trans2,SB)
% Trans2Model computes the model of two windings Transformer which
% the input format is para_trans2=[2,n1,n2, Pk,Uk,P0,I0,Sn,[U1 U2],[UB1
% UB2],[Umin Umax],step]

Pk=para_trans2(4); Uk=para_trans2(5); P0=para_trans2(6); I0=para_trans2(7);
Sn=para_trans2(8); U=para_trans2(9:10); UB=para_trans2(11:12);  

Rt=(Pk*U(2)^2)/(1000*Sn^2);
Xt=(Uk*U(2)^2)/(100*Sn);

if nargout>2
    Gt=P0/(1000*U(2)^2);
    Bt=(I0*Sn)/(100*U(2)^2);
end

Rt=Rt*SB/UB(2)^2;
Xt=Xt*SB/UB(2)^2;
if nargout>2
   Gt=Gt*UB(2)^2/SB;
   Bt=Bt*UB(2)^2/SB;
end

k=U(1)*UB(2)/(U(2)*UB(1));
Y=zeros(1,2);
Z=k*(Rt+i*Xt);
Yt=1./(Rt+i*Xt);
if nargout>4
    Y(1)=(Gt-i*Bt)+(1-k)*Yt/k^2;%the side of higher voltage of the two-windings transformer;
else
    Y(1)=(1-k)*Yt/k^2;
end

Y(2)=(k-1)*Yt/k; %the side of lower voltage of the two-windings transformer;