Abstract
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.
Highlights
Due to its cleanliness and sustainability, the exploitation of solar energy in the world via solar photovoltaic PV systems has been escalating over past years [1]–[3]
PV systems are divided into two categories: homogeneous PV systems in which all PV units in a PV system receive the same levels of irradiance and temperature, and non-homogeneous PV systems in which PV units in a PV system work on dissimilar irradiances or temperatures
This study reveals that the PV module with overlapping bypass diodes generates higher local power when both bypass diodes are forward biased, and this generated power rises with an increment of shading level
Summary
Due to its cleanliness and sustainability, the exploitation of solar energy in the world via solar photovoltaic PV systems has been escalating over past years [1]–[3]. The effect of bypass diodes, in the non-overlapped configuration, on the behavior and characteristics of partially shaded PV modules have been thoroughly examined in many studies [12], [18]–[24] They lead to the appearance of multiple power peaks in the PV output power curve and form misleading power losses, they contribute to the reduction in mismatch power losses. The hot spots development in PV modules with overlapped bypass diodes has not been yet considered a vast number of papers address its formation and impact on the performance of PV module in the non-overlapped configuration [10], [29], [30] This manuscript meets the gap in the literature and conducts a comprehensive investigation to study the effects of overlaps didoes configuration on the development of output characteristics curves under all possible shading scenarios.
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