Automatic Shading Detection System for Photovoltaic Strings

Partial shading is one of the main factors that affect the output power of series-parallel photovoltaic (PV) strings. However, physical irradiance measurement instruments (e.g. pyranometers and pyrheliometers) are seldom used in commercial PV systems due to their high cost. This paper proposes an automatic shading detection system for estimating the shading rate by using voltage sensors. The main features of the proposed method are the utilization of a reduced number of sensors, a simple switching control strategy and the high detection rate. The feasibility and effectiveness of the proposed shading detecting system is validated through experiments.