Frequency control of power grids has become a relevant research topic due to the increasing penetration of renewable energy sources, changing system structure, and the integration of new storage systems, controllable loads and power electronics technologies. The advances in control, communication, and computation technologies also contribute to the development of new techniques and solutions. This paper provides an updated review of most important frequency stability concerns, applied modern control strategies, and existing challenges for the integration of renewable energy sources. The paper also discusses the current trends, recent achievements, and new research directions.
