I am using fsolve and receiving errors
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I have the following function which i am defining some of the parameters as follows:
function F = solar5d(x)
q = 1.60217662*10^-19;
k = 1.38064852*10^-23;
T = 298.15; % Temperature in degrees 25. This one is in Kelvin.
Ns = 72;
Np = 1;
Voc = 44.6;
Vm = 35.43;
Isc = 5.43;
Im = 4.95;
n = 1.086;
These are my unknown parameters i am looking for:
Iph = x(1);
Io = x(2);
Rs = x(3);
Rp = x(4);
Vt = x(5);
The following are the six questions i have to solve the system:
F(1) = Vt - n*k*T/q;
F(2) = Np*Iph - Np*Io*(exp(Voc/Ns*Vt)-1) - (Np*Voc)/(Ns*Rp);
F(3) = Np*Iph - Np*Io*(exp((Isc*Rs)/(Np*Vt)) - 1) - (Isc*Rs)/Rp - Isc;
F(4) = Np*Iph - Np*Io*(exp(((Vm/Ns)+(Im*Rs)/Np)/Vt) - 1) - Np*((((Vm/Ns)+((Im*Rs)/Np))/Rp)) - Im;
F(5) = (((Np/Ns*Vt)*Io*(exp((Vm + ((Im*Ns*Rs)/Np))/Ns*Vt)) + (1/(Ns*Rp)/Np))/(1 + (Rs*Vt)*Io*(exp((Vm + ((Im*Ns*Rs)/Np))/Ns*Vt)) + (Rs/Rp))) - (Im/Vm);
F(6) = (((-Np/Ns*Vt)*Io*(exp(Voc/Ns*Vt)) - (1/Ns*Rp/Np)) / (1 + (Rs/Vt)*Io*(exp(Voc/Ns*Vt)) + (Rs/Rp))) + 1/Rs;
end
But i am receiving the following error:
Warning: Trust-region-dogleg algorithm of FSOLVE cannot handle
non-square systems; using Levenberg-Marquardt algorithm instead.
> In fsolve (line 298)
Error using levenbergMarquardt (line 16)
Objective function is returning undefined values at initial point.
fsolve cannot continue.
Error in fsolve (line 397)
levenbergMarquardt(funfcn,x,verbosity,options,defaultopt,f,JAC,caller,
...
Please could you help me to solve my problem??
Thanks in advance.
Regards,
Charalampos
2 Comments
Walter Roberson
on 24 Nov 2017
You did not happen to show you call to fsolve, with your initial conditions.
Answers (2)
Torsten
on 24 Nov 2017
Add
disp(F)
at the end of solar5d.
I suspect that the array F contains Inf, NaN or something similar.
Take care that your initial values for the variables don't produce division by zero or undefined expressions.
Best wishes
Torsten.
7 Comments
Are Mjaavatten
on 24 Nov 2017
It seems that you try to solve an overdetermined system. You have six equations in five unknowns. You should re-examine your problem to see if one of your equations is superfluous.
Also, it is good practice (although not strictly necessary) to pre-allocate memory to F: Insert the command
F = zeros(6,1) % Or zeros(5,1)?
before you define the components of F.
9 Comments
Are Mjaavatten
on 24 Nov 2017
Did you check that fsolve converged at all? If so, if you plug the resulting x into solar5d the result should be a set of very small numbers. Solving a set of nonlinear equations is not always easy. In the general case, a solution may not even exist.
If you have some knowledge of what the solution should be, try with a starting vector close to this estimate. It may also be a good idea to double-check that your equations and parameters are all correct
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