i dunno why it run until 4th iteration then stopped...can anybody help me? it did not give any error...

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

[Geoff]

Please at least edit this question, highlight all the code and hit the 'code' button in the toolbar. Also, define 'stopped'. Did it give an error message, or did the loop complete cleanly (despite unexpectedly)?

Answer 1

[Richard Brown]

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)

[Dennis Ting]

thank you for ur guidance...it work...thank you...

Answer 2

[Richard Brown]

You're going to struggle to get someone to answer (let alone read) this question.

I would suggest using the debugger to step through your code one line at a time (to do this, click on a line of code and hit F12, next time you run it will stop here and you can advance it a line at a time using F10) and see if the values at each line are what you expect.

Answer 3

[Richard Brown]

It stops because dv1 drops below its threshhold, causing the loop to quit.

[Dennis Ting]

so what should i do to modify it? i am new to matlab...

[Walter Roberson]

Why do you need to modify it? What do you want to have happen if one of the values drops below the threshold?

[Dennis Ting]

i am doing the load flow analysis, need to find the value of voltage by using the gauss seidel...but with this, i havent get a constant voltage then the loop already stop...