% This program displays the plot for the PV curve given the PV equation of

% V2^2 = (V1^2/2 - B*PD*X) + sqrt(V1^4/4 - PD*X*(PD*X + B*V1^2))

%

% This program assumes certain initial values for this equation:

%     V1 = 1 (p.u.)

%     PD ranges from 0 to 1 (p.u.)

%     X = 0.8 and 1.2 (p.u.)

%

% This program then asks from the user a B value and solves for V2.

% V2 is then plotted against PD in a graph for both a two transmission

% line and a plot given a lost transmission line.



% Set initial for parameters.



x1 = 0.8;

x2 = 1.2;

x = (x1 * x2)/(x1 + x2);

v = 1.0;

p = linspace(0, 1, 100);



% Welcome user and describe program.



fprintf('\nThis program computes PV plots based on your input for B in the following \n');

fprintf('PV equation for a two transmission line system. \n\n');

fprintf('V2^2 = (V1^2/2 - B*PD*X) + sqrt(V1^4/4 - PD*X*(PD*X + B*V1^2))\n\n');



fprintf('This program also assumes the following initial values: \n');

fprintf('The reactance of the two lines are X = 0.8 and 1.2 p.u. \n');

fprintf('The voltage at the generator bus V1 = 1.0 p.u. \n');

fprintf('The value for the power delivered PD to the load ranges from 0.0 to 1.0 p.u. \n');



% Request from the user a value for B and verify that it is an integer

% between -1 and 1.



fprintf('\nPlease enter an enter a value for B. \n');

fprintf('This must be an integer between -1.0 and 1.0 \n');

fprintf('\nFor example you may begin by first setting B to zero to get a PV plot based solely \n');

fprintf('on the initial values. \n\n');



b = input(' ');



while (b < -1) | (b > 1)

   fprintf('\nThis number should be an integer between -1.0 and 1.0 \n');

   fprintf('Please re-enter an enter a value for B. \n\n');

   

   b = input(' ');

end



% Calculate and plot transmission line figures given intial parameters.



a1 = (v^2/2 - b.*p.*x) + sqrt(v^4/4 - p.*x.*(p*x + b*v^2));

a2 = (v^2/2 - b.*p.*x) - sqrt(v^4/4 - p.*x.*(p*x + b*v^2));

a3 = sqrt(a1);

a4 = sqrt(a2);



b1 = (v^2/2 - b.*p.*x1) + sqrt(v^4/4 - p.*x1.*(p*x1 + b*v^2));

b2 = (v^2/2 - b.*p.*x1) - sqrt(v^4/4 - p.*x1.*(p*x1 + b*v^2));

b3 = sqrt(b1);

b4 = sqrt(b2);



c1 = (v^2/2 - b.*p.*x2) + sqrt(v^4/4 - p.*x2.*(p*x2 + b*v^2));

c2 = (v^2/2 - b.*p.*x2) - sqrt(v^4/4 - p.*x2.*(p*x2 + b*v^2));

c3 = sqrt(c1);

c4 = sqrt(c2);



subplot(2, 1, 1), plot(p, a3, 'b-', p, a4, 'b-', p, b3, 'g:', p, b4, 'g:');

xlabel('PD (p.u.) with X = 0.8 p.u.');

ylabel('|V2| (p.u.)');

axis([0, 1, 0, 1.2]);



subplot(2, 1, 2), plot(p, a3, 'b-', p, a4, 'b-', p, c3, 'r:', p, c4, 'r:');

xlabel('PD (p.u.) with X = 1.2 p.u.');

ylabel('|V2| (p.u.)');

axis([0, 1, 0, 1.2]);



% Explain graph characteristics.



fprintf('\nThe first plot in the blue solid line shows the PV plot given the assumed initial values.\n');

fprintf('The second plot in the dashed green line shows the PV plot with X = 0.8 p.u. \n');

fprintf('The third plot in the dashed red line shows the PV plot with X = 1.2 p.u. \n\n');

fprintf('The second and third plots are the equivalent of transmission line failures. \n');



% Request from user if another plot is desired.

% Request from the user a new value for B and verify that it is an integer

% between -1 and 1.



fprintf('\nWould you like to see another PV plot with B adjusted to compensate for the \n');

fprintf('loss of the transmission line? \n');



fprintf('Please answer yes or no. \n\n');

z = input(' ', 's');

z1 = 'yes';



while strncmp(z, z1, 1) == 1

   

   

   fprintf('\nPlease enter an enter a value for B. \n');   

   fprintf('This can be any integer between -1.0 and 1.0 \n\n');

           

   r = input(' ');

   

   while (r < -1) | (r > 1)

      

      fprintf('\nThis number should be an integer between -1.0 and 1.0 \n');

      fprintf('Please re-enter an enter a value for B. \n\n');     

      r = input(' ');

      

   end

        

   % Calculate and plot new transmission line figures given new B.

      

   d1 = (v^2/2 - r.*p.*x1) + sqrt(v^4/4 - p.*x1.*(p*x1 + r*v^2));   

   d2 = (v^2/2 - r.*p.*x1) - sqrt(v^4/4 - p.*x1.*(p*x1 + r*v^2));   

   d3 = sqrt(d1);   

   d4 = sqrt(d2);

      

   e1 = (v^2/2 - r.*p.*x2) + sqrt(v^4/4 - p.*x2.*(p*x2 + r*v^2));   

   e2 = (v^2/2 - r.*p.*x2) - sqrt(v^4/4 - p.*x2.*(p*x2 + r*v^2));   

   e3 = sqrt(e1);

   e4 = sqrt(e2);

   

   subplot(2, 1, 1), plot(p, a3, 'b-', p, a4, 'b-', p, b3, 'g:', p, b4, 'g:', p, d3, 'r-.', p, d4, 'r-.');

   xlabel('PD (p.u.) with X = 0.8 p.u.');   

   ylabel('|V2| (p.u.)');   

   axis([0, 1, 0, 1.2]);   

      

   subplot(2, 1, 2), plot(p, a3, 'b-', p, a4, 'b-', p, c3, 'g:', p, c4, 'g:', p, e3, 'r-.', p, e4, 'r-.');

   xlabel('PD (p.u.) with X = 1.2 p.u.');   

   ylabel('|V2| (p.u.)');

   axis([0, 1, 0, 1.2]);

      

   % Explain graph characteristics.

   

   fprintf('\nThe first plot in the blue solid line shows the PV plot given the assumed initial \n');   

   fprintf('values. \n');   

   fprintf('The second plot in the dashed green line shows the PV plot with X = 0.8 and 1.2 p.u. \n');   

   fprintf('The third plot in the red dashes shows the adjusted PV plot based on your \n');   

   fprintf('inputted value for B against its respected transmission line. \n\n');

         

   fprintf('Would you like to try another value for B? \n');   

   fprintf('Please answer yes or no. \n\n');   

   z = input(' ', 's');

         

   end

   

end



% Request from user if another plot is desired using user inputted values.



fprintf('\nWould you like to see another example for a loss of a transmission line \n');

fprintf('and its associated PV plot based on your own inputted parameters \n');



fprintf('Please answer yes or no. \n\n');

w = input(' ', 's');

w1 = 'yes';



while strncmp(w, w1, 1) == 1

   

   % Request from user values for PV equation parameters.

   

   fprintf('\nPlease enter an enter a value for B. \n');

   fprintf('This must be an integer between -1.0 and 1.0 \n\n');

   b = input(' ');

   

   while (b < -1) | (b > 1)

      fprintf('\nThis number should be an integer between -1.0 and 1.0 \n');

      fprintf('Please re-enter an enter a value for B. \n\n');

   

      b = input(' ');

   end

   

   fprintf('\nThe values for PD will remain from 0.0 to 1.0 p.u. \n\n');   

   

   p = linspace(0, 1, 100);

   

   fprintf('\nPlease enter an enter a value for V1 in p.u. \n\n');

   v = input(' ');

   

   fprintf('\nPlease enter an enter a value for reactance for one of the two transmission lines. \n\n');

   x1 = input(' ');

   

   fprintf('\nPlease enter an enter a value for reactance for the second of the two transmission lines. \n\n');

   x2 = input(' ');

   

   x = (x1 * x2)/(x1 + x2);   

     

   % Calculate and plot transmission line figures given user inputted parameters.



   a1 = (v^2/2 - b.*p.*x) + sqrt(v^4/4 - p.*x.*(p*x + b*v^2));

   a2 = (v^2/2 - b.*p.*x) - sqrt(v^4/4 - p.*x.*(p*x + b*v^2));

   a3 = sqrt(a1);

   a4 = sqrt(a2);



   b1 = (v^2/2 - b.*p.*x1) + sqrt(v^4/4 - p.*x1.*(p*x1 + b*v^2));

   b2 = (v^2/2 - b.*p.*x1) - sqrt(v^4/4 - p.*x1.*(p*x1 + b*v^2));

   b3 = sqrt(b1);

   b4 = sqrt(b2);



   c1 = (v^2/2 - b.*p.*x2) + sqrt(v^4/4 - p.*x2.*(p*x2 + b*v^2));

   c2 = (v^2/2 - b.*p.*x2) - sqrt(v^4/4 - p.*x2.*(p*x2 + b*v^2));

   c3 = sqrt(c1);

   c4 = sqrt(c2);



   subplot(2, 1, 1), plot(p, a3, 'b-', p, a4, 'b-', p, b3, 'g:', p, b4, 'g:');

   xlabel('PD (p.u.) with X1');

   ylabel('|V2| (p.u.)');

   axis([0, 1, 0, 1.2]);



   subplot(2, 1, 2), plot(p, a3, 'b-', p, a4, 'b-', p, c3, 'r:', p, c4, 'r:');

   xlabel('PD (p.u.) with X2');

   ylabel('|V2| (p.u.)');

   axis([0, 1, 0, 1.2]);

   

   fprintf('\nThe first plot in the blue solid line shows the PV plot given your inputted values.\n');

   fprintf('The second and third plots in green and red are the equivalent of transmission line \n');

   fprintf('failures with x1 = %1.2f p.u. and x2 = %1.2f p.u. from your inputted reactance values. \n', x1, x2);

      

   % Request from user if another plot is desired using user inputted values.

   

   fprintf('\nWould you like to see another example for a loss of a transmission line \n');   

   fprintf('and its associated PV plot based on your own inputted parameters \n');

   

   fprintf('Please answer yes or no. \n\n');   

   w = input(' ', 's');   

   

end



fprintf(' \n');