MATLAB: I dunno why it run until 4th iteration then stopped…can anybody help me? it did not give any error…

debugging

clc
fprintf('\n\n')
Vb=230e3;
Sb=100e6;
Zb=Vb^2/Sb;
%  From  To    R       X
ldata=[1 2 12.333/Zb  0.0933*2*pi*60/Zb
       1 4  8.256/Zb  0.1056*2*pi*60/Zb
       2 3  6.328/Zb  0.0833*2*pi*60/Zb
       2 6 15.696/Zb  0.1696*2*pi*60/Zb
       3 5  5.839/Zb  0.0771*2*pi*60/Zb
       4 5 10.581/Zb  0.1129*2*pi*60/Zb
       4 7  5.993/Zb  0.0537*2*pi*60/Zb
       4 8  9.673/Zb  0.1055*2*pi*60/Zb
       5 8  7.996/Zb  0.1299*2*pi*60/Zb
       6 7 16.395/Zb  0.1753*2*pi*60/Zb
       6 8  5.839/Zb  0.0771*2*pi*60/Zb
       7 8  6.566/Zb  0.0818*2*pi*60/Zb]
    fb=ldata(:,1);
    tb=ldata(:,2);
    R=ldata(:,3);
    X=ldata(:,4);
    nbranch=length(ldata(:,1));
    nbus=max(max(fb),max(tb));
    Z=R+i*X;
    y=ones(nbranch,1)./Z;
    Y=zeros(nbus,nbus);
    ydata=[ldata(:,1),ldata(:,2),y];
    for k=1:nbranch;    
        if fb(k) > 0 && tb(k) > 0
            Y(fb(k),tb(k))=Y(fb(k),tb(k))-y(k);
            Y(tb(k),fb(k))=Y(fb(k),tb(k));
        end
    end
    for n=1:nbus;
        for k=1:nbranch;
            if fb(k)==n||tb(k)==n
            Y(n,n)=Y(n,n)+y(k);
            else end
        end
    end 
y12=ydata(1,3);
y14=ydata(2,3);
y23=ydata(3,3);
y26=ydata(4,3);
y35=ydata(5,3);
y45=ydata(6,3);
y47=ydata(7,3);
y48=ydata(8,3);
y58=ydata(9,3);
y67=ydata(10,3);
y68=ydata(11,3);
y78=ydata(12,3);
s1pu=-(125+i*100)/100;
p3pu=200/100;
s5pu=-(100+i*85)/100;
s6pu=-(150+i*100)/100;
s7pu=-(80+i*75)/100;
s8pu=-(130+i*115)/100;
v1=1.00;
v2=1.03;
v3=1.02;
v4=1.04;
v5=1.00;
v6=1.00;
v7=1.00;
v8=1.00;
dv1=10;
dv3=10;
dv5=10;
dv6=10;
dv7=10;
dv8=10;
iter=0;
disp('iter    v1     v3      v5      v6      v7       v8       abs(dv1)   abs(dv3)   abs(dv5)   abs(dv6)   abs(dv7)   abs(dv8)')
while abs(dv1)>=0.00001 && abs(dv3)>=0.00001 && abs(dv5)>=0.00001 && abs(dv6)>=0.00001 && abs(dv7)>=0.00001 && abs(dv8)>=0.00001 && iter<100
    iter=iter+1;
      v11=(conj(s1pu)/conj(v1)+y12*v2+y14*v4)/(y12+y14);
      dv1=v11-v1;
      v1=v11;
      Q3=-imag(conj(v3)*(v3*(y23+y35)-y23*v2-y35*v5));
      v31=(((p3pu-i*Q3)/conj(v3))+y23*v2+y35*v5)/(y23+y35);
      vr3=sqrt(abs(v3)^2-(imag(v31)^2));
      VR3=vr3+i*imag(v31);
      dv3=VR3-v3;
      v3=VR3;
      v51=(conj(s5pu)/conj(v5)+y35*v3+y45*v4+y58*v8)/(y35+y45+y58);
      dv5=v51-v5;
      v5=v51;
      v61=(conj(s6pu)/conj(v6)+y26*v2+y67*v7+y68*v8)/(y26+y67+y68);
      dv6=v61-v6;
      v6=v61;
      v71=(conj(s7pu)/conj(v7)+y47*v4+y67*v6+y78*v8)/(y47+y67+y78);
      dv7=v71-v7;
      v7=v71;
      v81=(conj(s8pu)/conj(v8)+y48*v4+y58*v5+y68*v6+y78*v7)/(y48+y58+y68+y78);
      dv8=v81-v8;
      v8=v81;
      fprintf('%g',iter),disp([v1,v3,v5,v7,v8,abs(dv1),abs(dv3),abs(dv5),abs(dv6),abs(dv7),abs(dv8)]);
  end    
v=[v1,v2,v3,v4,v5,v6,v7,v8];
for i=1:8;
    if imag(v(i))>=0
    fprintf('v%g=%2.4f+%2.4f*i pu \n',i,real(v(i)),imag(v(i)));
    else
    fprintf('v%g=%2.4f%2.4f*i pu \n',i,real(v(i)),imag(v(i)));    
    end
end

Best Answer

OK, with the disclaimer that what you have there isn't a particularly optimal way to write this code, you can fix your problem by replacing all of the && in the while line with || - your code is exiting when one component of the solution has converged, you should be watching for the worst component to have converged. (Oh, but don't modify the && for the iter expression). i.e.:
while iter < 100 && (abs(dv1)>=0.00001 || abs(dv3)>=0.00001 || abs(dv5)>=0.00001 || abs(dv6)>=0.00001 || abs(dv7)>=0.00001 || abs(dv8)>=0.00001)
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