Comprehensive Study of Partially Shaded PV Modules With Overlapping Diodes

Bypass diodes are usually connected in PV modules to reduce the impact of partial shading. There are two configurations of the bypass diodes used in commercially available PV modules: non-overlapping bypass diodes, in which each diode is separately connected to a unique group of series PV cells, and overlapping bypass diodes, in which the diodes are connected to mutual PV cells. Because almost all PV studies are based on non-overlapping configuration, the effects of the diodes are well understood. On the other hand, a complete analysis for the effects of the overlapped bypass diodes on the performance of the PV module has not been yet systematically disclosed. Moreover, there is still no available mathematical formulation to model such PV modules without the use of circuit simulations. This paper first derives a mathematical modeling approach to simulate overlapped PV modules and then provides a comprehensive study and analysis for the effect of overlapped bypass diodes on the electrical response of PV module under a wide variety of possible shading levels to fully understand their effects and impact. Moreover, it reveals their effects on partial shading power losses, and on the hot spot formation, which both have not yet been investigated in the literature of overlapped PV modules. Their possible negative effects on the efficiency of micro inverters are also illustrated. The results are validated both using Matlab Simulink and experimentally.