We already now that while changing the duty cycle of  DC/DC converter in order to track the MPP, the output voltage of  the converter is going to be changed as well.

So, the output voltage of the DC/DC converter will not be stable to supply a load or to charge a battery since we need a stable constant voltage to supply the load.

If the output of the dc/dc converter is constant, we can not get proper mppt operation. So, for example for higher irradiation condition, output voltage must increase which increasing the output power. For battery charging, more output voltage means more charge current. For dc motor load, again higher voltage means higher mechanical speed and higher power. In the attached figure dashed line shows constant power curve. For varying output voltage, at some point the input voltage corresponds to MPP. 

For battery charging the output voltage variation is limited.  So, first using buck converter for mppt and connecting boost converter to its output for voltage regulation can be used. Before using that you can try only a buck converter and see if mppt is okay for wide range of environmental conditions. Otherwise you can include boost converter.

The attached paper has 40 different way to implement MPPT and I think its useful for you.

Mohamed Azab ,

Abdulkadir Mühendis ,

MOHAMAD ARINAL BIN ABDUL HALIM

Thank you very much guys.

Dear Mohammed,

It is not possible to achieve MPPT for a load that requires a constant voltage supply to operate unless the power consumption of that load matches (or is very close) to the MPPT point of the PV.

The only way to achieve MPPT is to supply a constant voltage source (such as a battery) and vary the current into it by using a power converter. In a similar way, this can work with a constant current source and vary the voltage across it.

Michalis Florides Thank you,

It is challenging to achieve MPPT and voltage regulation at the same time unless the PV panel always operate near to MPP. However, using both MPPT algorithm and PI controller for generation of duty cycle to the boost switch. Refer to research articles of Kishore Chhatterjee sir or Vivek Agarwal Sir of IIT Bombay, India. They have used MPPT + PI

Hema Chander Thank you very much,

Hi,

The nature of many MPPT algorithms is based on perturbation applied to the duty cycle of power converters. Therefore, the output voltage and current have oscillations. However, there are methods to either reduce the steady-state oscillations [1] or get rid of them completely [2].

[1] J. Dadkhah and M. Niroomand, “Real-Time MPPT Optimization of PV Systems by Means of DCD-RLS Based Identification,” IEEE Trans. Sustain. Energy, vol. 10, no. 4, pp. 2114–2122, 2019.

[2] F. Paz and M. Ordonez, “Zero Oscillation and Irradiance Slope Tracking for Photovoltaic MPPT,” IEEE Trans. Ind. Electron., vol. 61, no. 11, pp. 6138–6147, 2014.

use DC-DC converter with suitable MPPT algorithm

Friends Thank you all ❤️.

Check the following papers:

Xiao, Weidong, William G. Dunford, Patrick R. Palmer, and Antoine Capel. "Application of centered differentiation and steepest descent to maximum power point tracking." IEEE Transactions on Industrial Electronics 54, no. 5 (2007): 2539-2549.

Subudhi, Bidyadhar, and Raseswari Pradhan. "A comparative study on maximum power point tracking techniques for photovoltaic power systems." IEEE Transactions on sustainable energy 4, no. 1 (2012): 89-98.