Global maximum power point tracking algorithm for photovoltaic systems under partial shading conditions

Abstract

This paper presents a novel algorithm for tracking the true maximum power point (MPP) for a photovoltaic (PV) system under partial shading conditions using variable step size. At uniform irradiance, due to nonlinear VI characteristics of PV array, there exists a unique MPP at which the solar array produces the maximum output power. However, under partial shading conditions, there exist multiple peaks on VI and PV characteristics that give rise to local and global MPP's. In order to obtain the optimum output, global MPP must be tracked via an intelligent algorithm capable of distinction between local and global maximum power points. Further, the proposed algorithm must be robust and exhibiting fast response to ambient conditions. In this paper, a Photovoltaic system is explicitly modeled and by modifying the existing Perturbation and Observation (P&O) algorithm, a robust, optimized and efficient algorithm for the global maximum power point tracking (GMPPT) is formulated. The proposed algorithm is an extension of commonly used P&O method in which variable step size ensure fast convergence to GMPPT and power measurement of the PV array avoids false readings. Simulation results show that the newly formed algorithm has a greater degree of accuracy at constant and varying changing irradiance level under partial shading.