Solar cell data fitting

[solardude]

Hi,

I am trying to use labview for non-linear data fitting of current-potential curves from a solar cell.

The equation I need to use comes from the one diode equivalent circuit of solar cells, that is:

I = Iph - Is*exp(q(Vo-Rs*I)/nkt-1) - (Vo-Rs*I)/Rp

To make it look more friendly, it is of the form:

y = A - B*exp(C*(x-Rs*y)-1) - (x-Rs*y)/Rp

I want to extract Rs and Rp, which are the series and parallel resistance of the cell.
Problem is that it is not an easily solved equation, and a simple least squares fitting method will not work.

Are there any VIs in Labview that could heplp me for fiting my data with this equation?

Thanks,

Aurelien

[Kenny_K]

Do you have any sample data that could be plotted to try and get a curve fit or maybe some values that can be plugged into the equation???  Jsut makes it easier to evaluate and try to get a curve fit.

If you dont want to post your data, there are numerous VIs in the Analyze>Mathmatics>Curve Fitting section on the functions pallette that you can try to play around with.  They are very useful.

Kenny

[devchander]

Hi Aurelien,

I designed a software that controls a solar cell tet bed and derieves all the parameters from VI , P V curves of teh tested solar cell

Right now I do not recall what equation/parameters did i use to derieve the Rs and Rp, but i remeber using a simplified equation.

Just hold on till i search for those equations and get back to you

Regards

Dev

[Henrik_Volkers]

maybe try the Nonlinear Lev-Mar Fit (Not in Base Package) located @ mathematics, curve fitting

[chtan23]

hey Solar dude ,

How the progression on your problem ?

I am doin something similar as well.

Maybe you could help me with mine ...

Or show me what you have done so far