A state-of-the-art review of adaptive, predictive, synergistic, and degradation-aware power variability smoothing techniques in photovoltaic power plants

The variability of renewable energy (RE) sources, like photovoltaic power plants (PVPPs), presents a major challenge in the decarbonization of electrical power grids. Extensive literature exists on variability smoothing techniques in PVPP, both with and without battery energy storage systems (BESS). However, some of these techniques may lead to energy losses and opportunity costs, while others may require larger BESS capacities to perform effectively. Additionally, improper control settings can result in increased BESS cycling and degradation. Moreover, certain techniques may only provide control for ramp-up events and not ramp-down events. With all these tradeoffs, this paper provides an up-to-date review of the PVPP output smoothing techniques and the challenges associated with their implementation, as well as the grid codes imposed to mitigate the impact of PVPP variability on the power grid. This paper also proposes state-of-the-art features that facilitate seamless grid integration of PVPPs. It proposes adaptive smoothing techniques responsive to dynamic weather conditions and BESS health diagnostics; proactive smoothing, which predicts rather than merely reacts to ramp events; synergistic smoothing, where multiple RE systems collaborate to overcome the limitations of individual systems; and degradation-aware smoothing, which considers BESS health in its decision-making. Finally, the paper identifies promising research directions in this field.