Two-Tests Procedure to Determine the Equivalent Circuit's Parameters of Half-Cells in Commercial PV Modules under Sunlight and Partial Shading

The performance of photovoltaic (PV) generators can be modelled using electrical equivalent circuits with a variable number of parameters. This paper is included in a line of research aiming to develop an automatic acquisition system based on the equivalent circuit's parameters for fault detection in PV plants. In this context, the estimation of the parameters in the case of partial shading is fundamental to distinguish between suboptimal operation or faulty conditions. This work proposes a methodology to estimate the equivalent circuit's parameters of irradiated and shaded cells for commercial PV modules with half-cell technology. The procedure is based on experimental tests performed at Politecnico di Torino (Italy) on two commercial modules and ten single-string mini-modules. The results permit evaluating the effect of shading on the equivalent circuit's parameters of the cells, and the shaded cells exhibit higher reverse saturation current and series resistance, along with a lower shunt resistance.