Analysis of Interconnection Schemes for PV Systems Operating under Shadow Conditions

The output power of a PV system consisting of multiple strings and arrays of PV modules reduces drastically as shading increases on it. The shaded module in a string limits the output current of the entire string thereby reduces its output power. Different techniques are used for the optimal interconnection of modules in a PV system that not only helps in reducing the deteriorating effects of partial shading but also enhances the output power of the overall PV system. The performance and the cost analysis of different interconnection schemes including series-parallel (SP), honeycomb (HC), bridge-linked (BL), and total cross tied (TCT) with bypass diode are presented. Commonly existing shading patterns including diagonal (DI), short wide (SW), long wide (LW), short narrow (SN) and short wide (SW) are evaluated. Results show that TCT exhibits better output power under all shade patterns. For a typical 4×4 PV system operating under diagonal shading condition, 15.1% gain in output power can be achieved through TCT connection in comparison to conventional SP interconnection. Further, it has been found that the cost of extra conductors incurred due to TCT connection can be recovered through enhanced energy output within three quarters of the year.