Efficient Global Maximum Power Point Tracking Strategy for PV Systems

Abstract

Nowadays, research is focused on optimizing the efficiency of photovoltaic power generation, especially under partial shading or other disruptive events leading to mismatch losses. During most of these events, multiple local maximum power points may occur in the power-voltage characteristics of the PV array, and conventional Maximum Power Point Tracking (MPPT) methods may therefore fail to operate the PV array at the global maximum power point. On the other hand, scanning the entire voltage range requires much time, which results in PV power losses. In terms of reducing the scanning voltage range and improving the tracking performance, this paper proposes a novel Global MPPT (GMPPT) strategy based on a nonlinear controller. The characteristics of a PV array, under such disruptive events, are first analyzed and then the working principle of the proposed strategy elements is described. A dynamic model of the dc-dc converter, interfacing the PV array with the load, is considered in order to ensure better control accuracy and rapidity. The proposed scanning process and the design of the nonlinear controller are then described in detail. In order to validate the designed control strategy, a numerical simulation is carried out using a PV array powered battery charging system. Tracking performances, achieved using the proposed GMPPT method, are then compared with those of a previously proposed one. Simulation results have shown that the proposed strategy is significantly faster and more accurate, thus confirming its viability and efficiency.