Maximum-Power-Point Tracking for Photovoltaic Arrays with Partial-Shading Detection

Abstract

In this paper, an approach to maximum-power-point tracking (MPPT) for photovoltaic (PV) arrays with partial-shading detection is demonstrated. The proposed MPPT algorithm consists of the incremental conductance (IncCond) technique with step-size variation, the partial-shading detection, and the scan for global maximum power point (GMPP) with search area restriction. The variable step size for MPPT relied on the change in array power and current. Inspection of irradiance condition was performed, so that the scan for GMPP over a voltage range occurred only if the partial shading was detected. Two partial-shading detection criteria were developed: the array was assumed to be partially shaded if just either of these two criteria was satisfied. Then, the array short-circuit current and open-circuit voltage under the present weather condition were also used for the search area restriction. After one side of the search area boundaries had been reached and the necessity of scan towards the other side was confirmed, the array operating point was then moved directly to its initial position to avoid retracing the route of search. Following the completion of scan, the array operating point was moved directly to the recorded GMPP without steady-state oscillation. In comparison to the two previously published algorithms, simulation results of the proposed MPPT technique indicated that the search area of GMPP could be narrowed by at least 20% under partial-shading conditions, and the tracking could be accelerated by about 90% under uniform irradiance.