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From: Ismael Ochoa on 17 Jul 2010 09:40
I wrote the following file to solve DAE with ode15s. the value of "A" changes during at 3 s.But, I can not see the transient just in the variable x(:,4). why?:

function SDAEPP2
clear all; close all; clc
A=0.2;
x0=zeros(4,1);
x0(4) = 1; %V3
M=diag([1 1 0 0]);
options=odeset('Mass',M);
tspan=[0 3];
events = 0;
[t,x]=ode15s(@DAEpscad2,tspan,x0,options);
%%
A=0.4;
tspan=[3 5];
events = [events 1];
nout=length(t);
x0=x(nout,:);
htry=t(end)-t(end-1);
[tsg,xsg]=ode15s(@DAEpscad2,tspan,x0,odeset(options,'InitialStep',htry));
t=[t;tsg];
x=[x;xsg];
subplot (231) ; plot(t,x(:,1)*180/pi); grid on; title('x1: delta 2');
subplot (232) ; plot(t,x(:,2)); grid on; title('x2: W(t)');
subplot (233) ; plot(t,x(:,3)*180/pi); grid on; title('x3: delat 3');
subplot (234) ; plot(t,x(:,4)); grid on; title('x4: V3');

function dxdt=DAEpscad2(t,x)
ZBac=345^2/100;
V2=382.8672/345;
V1=0.6235;
d1=0;
ZL=1j*(A*2*pi*50)/ZBac;
%Matriz [Y]
y13=1/ZL;
y31=1/ZL;
Y11=y13; Y12=0; Y13=-y13;
Y21=0; Y22=25.843-1j*96.1397 ; Y23=-25.843 + 1j*96.139;
Y31=-y31; Y32=-25.843+1j*96.139; Y33=25.843 - 1j*96.139+y31;
YF=[Y11 Y12 Y13
Y21 Y22 Y23
Y31 Y32 Y33];
Y=abs(YF);
th=angle(YF);

Pm0=2.285911; H = 3; D = 0.25; wB=2*pi*50;

dxdt = zeros(4,1);
dxdt(1) = x(2);
dxdt(2) = wB/(2*H) * ( Pm0 - (V2^2*Y(2,2) * cos(th(2,2)) + V2 * x(4)* Y(2,3) * cos(th(2,3)+x(3)-x(1))) - D * x(2));
dxdt(3) = + V1 * x(4) * Y(3,1) * cos(th(3,1) + d1 - x(3))...
+ x(4) * V2 * Y(3,2) * cos(th(3,2) + x(1) - x(3)) + x(4)^2 * Y(3,3) * cos(th(3,3));
dxdt(4) = - x(4) * V1 * Y(3,1) * sin(th(3,1)+d1-x(3)) - x(4) *V2 * Y(3,2) * sin(th(3,2) + x(1) - x(3)) -x(4)^2 * Y(3,3) * sin(th(3,3));
end

end
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