Numerical Analysis of Renewable Generation Variability for Energy Storage Smoothing Applications

With the increasing penetration of Wind Turbine (WT) and Photovoltaic (PV) generation, there is a rising concern about the problems associated to power variability and how the system can be operated to mitigate its effects. Energy Storage Systems (ESSs) can be used to limit or smooth variability while maximizing the generation of renewable energy. However, existing references to the problems caused by power variability are not clear on the technical requirements of smoothing algorithms. This paper reviews existing information, including academic research, technical reports and international grid codes, on the problems caused by power variability and how they can be numerically evaluated in terms of severity, probability and time range of variations. The effects in power variability of smoothing algorithms according to existing evaluation methods is analyzed in a hybrid plant case study. Keywords— Energy Storage Systems (ESSs), Wind Energy, Smoothing control, Ramp-rate, Power Quality, Energy Management System, Frequency fluctuations.