Maximum Power Point Tracking Scheme for PV Systems Operating Under Partially Shaded Conditions

TLDR

Photovoltaic arrays under partial shading exhibit multiple steps and peaks in their I‑V and P‑V curves, making maximum‑power‑point tracking difficult and causing most existing schemes to fail at extracting the global peak. This work introduces a novel algorithm designed to track the global power peak in partially shaded PV systems. The algorithm, grounded in extensive analysis of PV characteristics, operates with a DC‑DC converter and a feedforward controller that uses the algorithm’s reference voltage to accelerate convergence toward the MPP. Experimental and simulation results show that the proposed controller reduces tracking time to roughly one‑tenth of that achieved by conventional controllers.

Abstract

Current-voltage and power-voltage characteristics of large photovoltaic (PV) arrays under partially shaded conditions are characterized by multiple steps and peaks. This makes the tracking of the actual maximum power point (MPP) [global peak (GP)] a difficult task. In addition, most of the existing schemes are unable to extract maximum power from the PV array under these conditions. This paper proposes a novel algorithm to track the global power peak under partially shaded conditions. The formulation of the algorithm is based on several critical observations made out of an extensive study of the PV characteristics and the behavior of the global and local peaks under partially shaded conditions. The proposed algorithm works in conjunction with a DC-DC converter to track the GP. In order to accelerate the tracking speed, a feedforward control scheme for operating the DC-DC converter is also proposed, which uses the reference voltage information from the tracking algorithm to shift the operation toward the MPP. The tracking time with this controller is about one-tenth as compared to a conventional controller. All the observations and conclusions, including simulation and experimental results, are presented.