An Adaptive Perturb and Observe Maximum Power Point Tracking System for Photovoltaic Arrays

This paper presents a maximum power point (MPP) hardware tracking system based on an adaptive Perturb and Observe (PAO) algorithm. Under a given solar and temperature condition the search for the MPP starts with a large perturbation step. When a drop in the delivered power is detected, the size of the step is halved and the direction of duty cycle change is reversed. Eventually the MPP will be tracked by small perturbation step (e.g. 1/ 255). When tracking at a maximum and a sudden change occurs in the atmospheric conditions, the system will try to reach the new MPP, with an adaptive perturbation step size that is allowed to increase after 4 consecutive increases or decrease in the duty cycle leading to increase in power delivery. This adaptive PAO algorithm forces the system to respond fairly quickly to any changes in the solar radiation or temperature level irrespective of where the previous operating point MPP was and without deteriorating the tracking efficiency. A tracking efficiency of about 96% was achieved using a very simple controller.