Hybrid HVAC–HVDC Grids: Review on Techno-Economic, Societal, and Regulatory Aspects

Nowadays, there is a growing trend towards converting existing transmission infrastructure to hybrid high-voltage alternating current (HVAC) and high-voltage direct current (HVDC) systems, driven primarily by the need for increased power transmission capability and lower operational costs. However, as HVAC grids are becoming more complex with the integration of advanced energy storage systems and power electronics, and as HVDC systems are increasingly deployed to efficiently transmit power from both onshore and offshore renewable sources over long distances or to facilitate interconnections across countries and regions, the implementation of such hybrid grids faces substantial technical, regulatory, and economic challenges. In this context, the primary objective of this work is to review the existing technical and regulatory aspects of HVAC–HVDC systems and to identify gaps that may hinder their effective implementation. Finally, it aims to highlight the benefits of such grids, as well as to examine the key needs and barriers associated with their deployment.