Dear Mohamed Tawfiky,

I suggest to you links and attached files in topics.

-Maximum Power Point Tracking Using Sliding Mode Control for ...

ijeee.iust.ac.ir/article-1-523-en.pdf

-A Review: Implementation of Maximum Power Point Tracking ...

https://www.ijareeie.com/upload/2015/.../89_A_Review_online_.p...

- Comparative assessment of maximum power point tracking ...

www.sciencedirect.com/science/article/pii/S2468025716300425

-Download as PDF - InTech

www.intechopen.com/download/pdf/13973

Best regards

thank you very much prof mohamed

Dear Mohamed,

To calculate the derivative of the line current, you can use various robust techniques like Sliding Mode [1], Algebraic Method [2], Homogeneous method [3] etc. 

In our article, we have used these differentiators for derivative estimation purpose. You can consult [4] for discrete time equations of the above differentiators. You can directly use these equations for real time estimation purpose in a micro-controller for example. 

1. Levant, A. (1998). Robust exact differentiation via sliding mode technique. automatica, 34(3), 379-384.

2. Mboup, M., Join, C., & Fliess, M. (2009). Numerical differentiation with annihilators in noisy environment. Numerical algorithms, 50(4), 439-467.

3. Perruquetti, W., Floquet, T., & Moulay, E. (2008). Finite-time observers: application to secure communication. IEEE Transactions on Automatic Control, 53(1), 356-360.

4. Ahmed, Hafiz, et al. "A fault detection method for automatic detection of spawning in oysters." IEEE Transactions on Control Systems Technology 24.3 (2016): 1140-1147.

Try to find with several points of the nail function, I recommend curve fitting, then look for its derivative, greetings

Dear Sir,

I suggest to you using the  tracking differentiator found in this paper

http://thesai.org/Downloads/Volume7No10/Paper_32-On_the_Improved_Nonlinear_Tracking_Differentiator.pdf

DEAR SIR MOHAMED

HOPE BELOW SLIDE COULD HELP

BEST WISHES

DR MOHAMAD ARINAL

http://dr-mohamad-arinal.simplesite.com/432957824

http://ernie-coffee-printing.simplesite.com/