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Photovoltaic systems that are partially shaded show changes in their I–V curve that makes its shape is different from that typically shown in unshaded PV panels. The effects of shading depend on several factors like electrical connections between elements or the geometry of the PV-cells. This paper presents a generalized, quick and simple method for modelling and simulating the electrical behaviour of PV installations under any shading situation which is mainly based in the Bishop modelling. So, the proposed method models PV-systems by discretizing currents and voltages in PV-cells which are connected in series and parallel associations (PV-cells, PV-groups, PV-modules, PV-strings and PV-array). For the PV-cell, a non-linear and implicit function which takes into account forward and reverse biasing is considered. Bypass diodes have also been included in the model. The relationship between discrete currents and voltages is established using the Newton–Raphson algorithm, analytical approximations and interpolation methods. The proposed method is used to provide a complete analysis of current, voltage and power in several PV systems under partial shading conditions. |
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