Analysis of the PV-to-PV architecture with a bidirectional Buck-Boost converter under shading conditions

Differential power processing (DPP) architectures have been emerging as a promising strategy for mitigating the harmful effects of the photovoltaic (PV) string mismatches. In this strategy, DPP converters are connected in parallel with the PV string to improve the energy harvesting. However, in some situations, the position, intensity of shading, and the length of the string negatively influence the performance of such architectures. In this context, this work presents a novel mathematical approach that enables analyzing the effect of such aspects in the output power and efficiency of the PV-to-PV architecture. The set of derived equations allows determining the values of the currents flowing through the DPP converters that compose the PV-to-PV architecture. An important aspect is validated by the mathematical analysis, proving that the shading position on the PV-to-PV architecture directly impacts the phenomenon known as diverted current accumulation. To the best of the authors' knowledge, this issue has not yet been assessed in the literature. Besides, this study is of major importance because it influences the losses in the power converters of the DPP structure. The assessment of various shading positions on the PV-to-PV architecture reveals that, in specific positions, the currents that flow through the converters are significantly reduced. For the set of situations analyzed, an improved energy harvesting from the PV-to-PV architecture and efficiency over 95% are verified.