Discretized model for partially shaded PV arrays composed of PV panels with overlapping bypass diodes

There are two typical configurations of bypass diodes used in PV-cell connection: nonoverlapped and overlapped. This paper presents a generalized method for electrical modeling of PV panels with overlapping bypass diodes to analyze nonuniform irradiance situations. The proposed model is based on piecewise polynomial functions, which use a discrete set of data to model PV cells under several shading situations and bypass diode connections. Analyzing electrical connections, the remaining PV array elements are modeled. In the case of a single PV panel, a Newton-Raphson method is used to derive its piecewise polynomial functions. The proposed method is used to provide a complete analysis of current, voltage, and power in PV arrays under partial shading conditions. From the results, it was verified that some elements of a PV array can act as loads under nonuniform irradiance.