Effects of the Sharpness of Shadows on the Mismatch Losses of PV Generators under Partial Shading Conditions Caused by Moving Clouds

Abstract

Photovoltaic (PV) generators are composed of seriesand parallel-connected PV modules. PV generators can be exposed to mismatch power losses when operating under nonhomogeneous conditions, such as partial shading due to moving clouds. In this paper, the effects of the sharpness of shadows on the mismatch losses of PV generators are studied under partial shading conditions caused by moving clouds. The effects are studied with three different movement directions of shadows: parallel, perpendicular and diagonal to the strings of PV generator arrays. The studied configurations of PV generators are series-parallel (SP), total-cross-tied (TCT) and multi-string (MS). The sharpness of a shadow is modelled by the width of the transition region on the edge of the shadow where the irradiance decreases from the clear sky to the fully shaded value. The work has been conducted by using an experimentally verified MATLAB Simulink model of a PV module based on the well-known one-diode model of a PV cell. The simulations show that the sharpness of shadows has a substantial effect on the amount of mismatch losses. Mismatch losses were also found to be very sensitive to the direction of the movement of shadows, the array size and the configuration of the generator.