I. Introduction
The electricity sector is going through a green revolution, powered by the uptake of renewables and retirement of fossil-fuel-based generation. In this scenario, solar photovoltaic (PV) systems are among the largest contributors to the renewable energy mix, thanks to the key role of power electronic converters. Modeling and control of converters is an established yet ever-growing topic among industrial and academic circles, which initially focused on dc–dc converters and then delved into dc–ac converters. Despite the early achievements, small-signal models of dc–dc converters were formally revisited in the presence of a PV input only in the mid 2000s. In [1] and [2], it was found that the dynamic resistance of the PV source heavily affects the converter transient performance and PV voltage regulation. Later, the authors in [3]–[8] revealed stability issues in PV interfacing current-controlled buck converters caused by the variability of dynamic and static resistance of the PV source.