应用介绍

这个程序可以获取单机系统故障之前，故障期间，故障清除之后的功率角曲线，等面积法应用在这里去找到单机系统到稳态的临界间隙角

if exist('Pm')~=1

Pm = input('Generator output power in p.u. Pm = '); else, end

if exist('E')~=1

E = input('Generator e.m.f. in p.u. E = '); else, end

if exist('V')~=1

V = input('Infinite bus-bar voltage in p.u. V = '); else, end

if exist('X1')~=1

X1 = input('Reactance before Fault in p.u. X1 = '); else, end

if exist('X2')~=1

X2 = input('Reactance during Fault in p.u. X2 = '); else, end

if exist('X3')~=1

X3 = input('Reactance aftere Fault in p.u. X3 = '); else, end

Pe1max = E*V/X1; Pe2max=E*V/X2; Pe3max=E*V/X3;

delta = 0:.01:pi;

Pe1 = Pe1max*sin(delta); Pe2 = Pe2max*sin(delta); Pe3 = Pe3max*sin(delta);

d0 =asin(Pm/Pe1max); dmax = pi-asin(Pm/Pe3max);

cosdc = (Pm*(dmax-d0)+Pe3max*cos(dmax)-Pe2max*cos(d0))/(Pe3max-Pe2max);

  if abs(cosdc) > 1

  fprintf('No critical clearing angle could be found.\n')

  fprintf('system can remain stable during this disturbance.\n\n')

  return

  else, end

dc=acos(cosdc);

if dc > dmax

fprintf('No critical clearing angle could be found.\n')

  fprintf('System can remain stable during this disturbance.\n\n')

  return

  else, end

Pmx=[0  pi-d0]*180/pi; Pmy=[Pm Pm];

x0=[d0 d0]*180/pi; y0=[0 Pm]; xc=[dc dc]*180/pi; yc=[0 Pe3max*sin(dc)];

xm=[dmax dmax]*180/pi; ym=[0 Pe3max*sin(dmax)];

d0=d0*180/pi; dmax=dmax*180/pi; dc=dc*180/pi;

x=(d0:.1:dc);

y=Pe2max*sin(x*pi/180);

y1=Pe2max*sin(d0*pi/180);

y2=Pe2max*sin(dc*pi/180);

x=[d0 x dc];

y=[Pm y Pm];

xx=dc:.1:dmax;

h=Pe3max*sin(xx*pi/180);

xx=[dc xx  dmax];

hh=[Pm h  Pm];

delta=delta*180/pi;

if X2 == inf

fprintf('\nFor this case tc can be found from analytical formula. \n')

H=input('To find tc enter Inertia Constant H, (or 0 to skip) H = ');

   if H ~= 0

   d0r=d0*pi/180; dcr=dc*pi/180;

   tc = sqrt(2*H*(dcr-d0r)/(pi*60*Pm));

   else, end

else, end

%clc

fprintf('\nInitial power angle     = %7.3f \n', d0)

fprintf('Maximum angle swing     = %7.3f \n', dmax)

fprintf('Critical clearing angle = %7.3f \n\n', dc)

if X2==inf & H~=0

fprintf('Critical clearing time  = %7.3f sec. \n\n', tc)

else, end

h = figure; figure(h);

fill(x,y,'m')

hold;

fill(xx,hh,'c')

plot(delta, Pe1,'-', delta, Pe2,'r-',  delta, Pe3,'g-', Pmx, Pmy,'b-', x0,y0, xc,yc, xm,ym), grid

Title('Application of equal area criterion to a critically cleared system')

xlabel('Power angle, degree'), ylabel(' Power, per unit')

text(5, 1.07*Pm, 'Pm')

text(50, 1.05*Pe1max,['Critical clearing angle = ',num2str(dc)])

axis([0 180  0 1.1*Pe1max])

hold off;