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//Chapter 6
//Example 6.5
//page 210
//To find bus voltages and Reactive power injected using GS iterations
clear;clc;
//Ybus matrix from the network
Ybus=[3-9*%i -2+6*%i -1+3*%i 0;
-2+6*%i 3.666-11*%i -0.666+2*%i -1+3*%i
-1+3*%i -0.666+2*%i 3.666-11*%i -2+6*%i
0 -1+3*%i -2+6*%i 3-9*%i]
//Case(i)
//////////////////////////////////////////////////////
//Pi Qi Vi Remarks Bus no//
P1=0; Q1=0; V1=1.04; //Slack bus 1
P2=0.5; Q2=0.2; V2=1.04; //PVbus 2
P3=-1.0; Q3=0.5; V3=1; //PQbus 3
P4=0.3; Q4=-0.1; V4=1; //PQbus 4
/////////////////////////////////////////////////////
printf('\nCase(i) When 0.2<Q2<1 pu and running for 1 iteration,we get \n\n');
Q2min=0.2;Q2max=1;
n=1;
for i=1:n
if Q2<Q2min then
Q2=Q2min;
V2=(1/Ybus(2,2))*(((P2-%i*Q2)/conj(V2))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4);
elseif Q2>Q2max then
Q2=Q2max;
V2=(1/Ybus(2,2))*(((P2-%i*Q2)/conj(V2))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4);
else
Q2=-imag(conj(V2)*Ybus(2,1)*V1+conj(V2)*(Ybus(2,2)*V2+Ybus(2,3)*V3+Ybus(2,4)*V4));
[mag,delta2]=polar((1/Ybus(2,2))*(((P2-%i*Q2)/(conj(V2)))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4));
V2=abs(V2)*(cos(delta2)+%i*sin(delta2));
end
V3=(1/Ybus(3,3))*(((P3-%i*Q3)/conj(V3))-Ybus(3,1)*V1-Ybus(3,2)*V2-Ybus(3,4)*V4);
V4=(1/Ybus(4,4))*(((P4-%i*Q4)/conj(V4))-Ybus(4,1)*V1-Ybus(4,2)*V2-Ybus(4,3)*V3);
end
printf('Q2=');disp(Q2);printf('pu');
printf('\n\n\ndelta2=');disp(abs(delta2));printf('rad');
printf('\n\n\nV1=');disp(V1);printf('pu');
printf('\n\n\nV2=');disp(V2);printf('pu');
printf('\n\n\nV3=');disp(V3);printf('pu');
printf('\n\n\nV4=');disp(V4);printf('pu');
// case(ii)
printf('\n\n\nCase(ii) When 0.25<Q2<1 pu and running for 1 iteration,we get \n\n');
//////////////////////////////////////////////////////
//Pi Qi Vi Remarks Bus no//
P1=0; Q1=0; V1=1.04; //Slack bus 1
P2=0.5; V2=1.04; //PVbus 2
P3=-1.0; Q3=0.5; V3=1; //PQbus 3
P4=0.3; Q4=-0.1; V4=1; //PQbus 4
/////////////////////////////////////////////////////
Q2min=0.25;Q2max=1;
n=1;
for i=1:n
if Q2<Q2min then
Q2=Q2min;
V2=(1/Ybus(2,2))*(((P2-%i*Q2)/conj(V2))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4);
elseif Q2>Q2max then
Q2=Q2max;
V2=(1/Ybus(2,2))*(((P2-%i*Q2)/conj(V2))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4);
else
Q2=-imag(conj(V2)*Ybus(2,1)*V1+conj(V2)*(Ybus(2,2)*V2+Ybus(2,3)*V3+Ybus(2,4)*V4));
[mag,delta2]=polar((1/Ybus(2,2))*(((P2-%i*Q2)/(conj(V2)))-Ybus(2,1)*V1-Ybus(2,3)*V3-Ybus(2,4)*V4));
V2=abs(V2)*(cos(delta2)+%i*sin(delta2));
end
V3=(1/Ybus(3,3))*(((P3-%i*Q3)/conj(V3))-Ybus(3,1)*V1-Ybus(3,2)*V2-Ybus(3,4)*V4);
V4=(1/Ybus(4,4))*(((P4-%i*Q4)/conj(V4))-Ybus(4,1)*V1-Ybus(4,2)*V2-Ybus(4,3)*V3);
end
printf('Q2=');disp(Q2);printf('pu');
printf('\n\n\nV1=');disp(V1);printf('pu');
printf('\n\n\nV2=');disp(V2);printf('pu');
printf('\n\n\nV3=');disp(V3);printf('pu');
printf('\n\n\nV4=');disp(V4);printf('pu');
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