A global MPPT technique invoking partitioned estimation and strategic deployment of P&O to tackle partial shading conditions

This paper presents a new method of tracking global maximum power point (GMPP) under non-uniform irradiation of the photovoltaic (PV) array and also suitable under uniform irradiation. From a comprehensive analysis of the PV characteristic it was found that the slope of the PV characteristic was constant up to a voltage point just less than the maximum power point voltage. This constancy in slope was effectively utilized to estimate the maximum power which can be delivered by the PV array. The proposal in this paper was based on estimating the maximum PV power in various preplanned segments by measuring the slopes at different strategic points. These strategic points were decided based on the measured open circuit voltage of the PV array. After measuring the slopes at the strategic points, the estimation will be effected and the segment in which the global maximum power occurs was computed. Upon determination of the optimal segment, the conventional perturb and observe technique was deployed in the optimal segment to reach the global maximum power point. Once the GMPP was reached any change in the level of irradiation or irradiation pattern will be sensed by monitoring the PV array current. Computer Simulation and experimental evaluation were made and conformed that the proposed method of GMPP tracking worked effectively yielding excellent steady state tracking efficiency with no divergence.