Use of system oscillation to locate the MPP of PV panels

Abstract

This letter proposes the use of system oscillation in a perturbation-based maximum power point (MPP) tracker to locate the MPP of photovoltaic (PV) panels. Instead of using an explicit perturbation source, the tracker controller is designed to make the overall system self-oscillate, so that the duty cycle of the main switch in the power conversion stage (PCS) is inherently modulated with a small-amplitude variation at a predefined frequency around the required steady-state value. The tracking mechanism is based on comparing the ac component (due to the variation of the duty cycle) and the average value of the input voltage of the PCS to determine the quiescent duty cycle. The proposed technique does not approximate the panel characteristics and can globally locate the MPP under wide insolation conditions. The tracking capability has been verified experimentally with a 10-W PV panel in a controlled setup. Performances at the steady state and during the large-signal change of the insolation level have been studied.