GMPP Estimator as a Global Solution for MPPT Algorithms Under Partial Shading Conditions

Abstract

The power versus voltage curve of a photovoltaic (PV) panel exhibits several maximum power points (MPPs) in a partial shading (PS) condition. Thus, it remains an optimization challenge to ensure that PV systems operate at their global MPP (GMPP). Scanning the output characteristics of the PV panels seems a general solution for this issue. However, applying a short circuit to the terminal of PV panels where there exists an electrolytic capacitor, has a detrimental effect on the lifetime of the system. To this end, in this article, a GMPP estimator is proposed as a global solution for conventional maximum power point tracking (MPPT) algorithms under PS conditions. The proposed technique improves existing simple MPPT algorithms with original approaches as follows: first, an accurate microscopic analysis of a PV characteristic in PS conditions is considered, second, an original definition of the dominant cells and modules in a PV panel is proposed that allows to reduce the PS patterns to a finite number, and third, the search area for the MPPT operation is reduced to find the accurate GMPP by proposing two voltage boundaries. The lower boundary corresponds to the GMPP under uniform shading condition that can be determined using a closed form formula, while the upper one refers to the GMPP of a dominant cell in a PV module that can be determined using an artificial intelligence technique. This can also help set the initial duty cycle in a convex area around the GMPP. The functionality of the proposed GMPP estimator is experimentally validated.