The ANALYIS OF SEPIC CONVERTER OF MAXIMUM POWER POINT TRACKING OF PV ARRAYS

Abstract

There exists a variety of maximum power point tracking (MPPT) techniques, each having its own merits
and demerits. Under partial-shading conditions, the conventional tracking techniques fail to guarantee
successful tracking of the global maximum power, ie the conventional MPPT methods such as perturb
and observe and incremental conductance may converge on local maximum power point resulting in
significant reduction of power generated. This paper discusses about an improved technique for tracking
global maximum power point of photovoltaic arrays that has better performance under partial shading
conditions. The first stage in this method is to find out global maximum power point among the local
maxima. Once the global maximum power point is found then by adjusting the duty ratio, the voltage
corresponding to maximum power can be found out. The control is then transferred to perturb and
observe algorithm stage. This technique could be applied for both stand alone and grid connected PV
system. A comparison study between a SEPIC converter and a buck boost converter with the above
mentioned algorithm has also been carried out in order to verify the performance of both the converters.
The above mentioned converters have been designed for 150W at a switching frequency of 10 KHz.
Modified algorithm has been simulated using MATLAB/Simulink and results are obtained. Partial
shading condition was modelled in MATLAB/Simscape and analysed the solar array characteristics under
various shading conditions. From the simulation results it was found that the SEPIC converter is much
more efficient and is highly suitable for photo voltaic applications.