Dear Ashraful haider,

This is not right as you felt. Before i answer your question i would like that you describe to us how did you simulate the I-V characteristics at L1.

Thank You sir. At first in my masters thesis work I have obtained the experimented curve from a research paper.From that curve from the slopes at Voc and Isc i have got Rs and Rsh. Using the values of Rs and Rsh I have simulated the I-V curve using the solar cell I-V equations. Then by changing the value of n i have fitted the experimental curve and simulated curve, That is the way i have simulated the curve at L1. Thank you sir in advance

Dear Ashraful haider,

Well!,

Since you have the same solar cell, then there are parameters which do not change with illumination. These parameters are the dark cell parameters which are: The reverse saturation current I0, the ideality factor n of the solar cell diode, the series resistance and  the the the shunt resistance.The parameter which will changes with  the illumination is the the photo current Iph. Fortunately, it is proportional  to the illumination level L. That is Iph at L= Iph at 1000 w/m^2 X L / 1000, where L is the new illumination. In your example it will be 0.7 Iph at 1000 w/m^2 .

Now all the parameters of the the new illuminated i-v curve are known and we can calculate and plot it.

You can get more information from the Link:https://www.researchgate.net/publication/236002879_A_course_on_photo-voltaic_array_systems?ev=prf_pub

wish you success.

Book A course on photo-voltaic array systems

Thank You sir. but in some research paper i have found that with the change in illumination level parameters like diode ideality factor, series and shunt resistance, reverse saturation current I0 also change. I am attaching the paper with my answer.It will be helpful for me if you give me a solution. Thank you sir for your assistance.

Thank You Mr Belhaouas Nasreddine. If I face any problem surely I will contact with You

Dear Ashraful haider,

Would you please read the the paper in the following link: https://www.researchgate.net/publication/3062547_A_distributed_SPICE-model_of_a_solar_cell?ev=prf_pub

. With this paper  you get insight about the model parameters of the solar cell and how could you measure them directly.

The method of Illuminated I-V curve fitting of the solar cells results in different values of the dark current parameters, I0, Rs , Rsh and Rs because you fit only the dark characteristics of the solar cell near the photo current. therefore, as the photocurrent decreases at lower illumination, I0, Rs ,and Rs   increase as observed from the dark i-v curve.

Unfortunately there are no theoretical dependence of these parameters on the photo current. However they could be considered fairly constant  

 at the practical illumination levels at the working conditions of the solar cells  as from e. g. 700 through 1000 w/ m^2.to 1400. The parameters can be considered constant.

Please read the paper and the comment and then we discuss the matter further.

Article A distributed SPICE-model of a solar cell

As Abdelhalim Zekry said these parameters can be considered constant for wide range of illumination. And if you are doing a MATLAB simulation there are many methods to plot IV and PV curves at different illumination levels. Also for ploting these we can neglect Rse and Rsh. You can find many papers on these topics. I am not sure if you are having problem with any of these. If you are then message me i will give the details.

Best of Luck 

Thank you sir.i have gone through your paper and some idea about the static and dynamic parameters. clearly rs,rsh,n and Io are dark parameters. during illuminated fitting we are fitting the dark parameters. now sir my question is suppose i have simulated the curves at 200,300 w/m^2 etc level from the 1000w/m^2 level.surely there will be some change of the parametrs.is there any way through which i can extract the parameters rs,rsh,n from the simulated curves at 200,300 w/m^2? as i am using the same parameters of 1000w/m^2 to simulate curves at  200,300 w/m^2 so is there will be any change in parameters? i dont think so

waiting for your assistance sir

Dear Dr. Ashraful Haider.

No, If you extract the parameters rs,rsh,and n from your simulated i-v curves assuming the sane values of the parameters at 1000 w/cm^2, then you well get the same values again proving that your calculations is correct.

To solve this problem you can measure the dark characteristics and from it you can determine I0, n, Rs, andRsh as i did in my paper 

or you can measure the illuminated I-V characteristics at the the required illumination levels and determine these parameters as you did at 1000 w/cm^2.

Then you make simulation assuming constant parameters say at the 1000 w/cm^2

and compare then with the measured curves. So, you can verify the validity of nearly constant dark parameters.

This my proposal to you.

You do not need to measure the solar cells yourself. You can use any published set of curves to prove your approach.

I am ready to discuss any further matter with you

wish you success. 

Thank you sir for your wise approach. now I will search for any published set of data at different set of illumination levels and will apply the same approach as i did for 1000w/m^2 illumination.

Sir one thing to know as I have simulated the curve at 1000w/m^2 and if i simulate the curve at Iph=0 then i will get the dark curve.Then if i apply your method to find the parameters will those be same to the parameters that I have simulated at 1000w/m^2 or different?

Thank you sir for your assistance.

Dear dr Ashraful Haider,

The dark characteristics can be directly measured as i did in my paper

or it can be constructed using the dark diode equation:

Id= Io( exp ((V- Id Rs)/ nVt) -1) + V/Rsh

If you want to calculate it from the parameters extracted from the illuminated curves, you have to divide the I-V curves into ranges according to the illumination level.

for example from 0 to L1, using the extracted parameters at L1

Then from L1 to L2,using the extracted parameters at L2

Then from L2 to L3,using the extracted parameters at L3

........................... etc. to the final current range according to your divisions.

This is the procedure to calculate the dark current from the set of the parameters at the different illumination levels.

I hope i answered your question.

wish you success.

heye you can even go for signal builder block in simulink and use different illumination settings....

Thank you sir for your wise advise.I will follow your approach.If I face any problem surely I will knock You.Once again thank you sir

Mr.Ashraf, Have you fixed your problem? 

Mr Sulthan yes i have found a solution to my problem. From a set of practical values at different illumination level i have simulated the curves and extracted the parameters.

Dear Ashraful, Go through my profile, may be my thesis can help you.

Thanks