Modeling of photovoltaic modules under common shading conditions

Abstract

Common shading conditions will lead to power loss and even result in hotspots, which may influence the reliability of photovoltaic (PV) systems. Therefore, it is necessary to model for PV modules under common shading conditions. Existing methods ignore the change of shunt resistance when the cell is shaded, leading to some errors of the I–V curve and P–V curve. In this paper, a physically explicable parallel circuit based on the single-diode model is proposed for the shaded cell. The parameters of shaded region and unshaded region are estimated respectively based on the shading proportion and transmittance. The shunt resistance of the shaded cell can be accurately estimated by the proposed method. The electrical model of PV module under common shading conditions is developed. Extensive experiments are conducted: PV modules are shaded by area-measurable shade cloth with regular shape to analyze I–V characteristics. PV modules are also shaded by uniformly accumulated dust, and leaf/soil/shadow with arbitrary shape and location to simulate the situation in real PV station. Experimental results verify that the I–V curve and P–V curve simulated by the proposed electrical model are more consistent with the measured results compared with the existing method.