A Vision of HVDC Key Role Toward Fault-Tolerant and Stable AC/DC Grids

Massive off-shore wind integration in the European power system and the necessity to increase the power flows between asynchronous areas and inside continental Europe, call for HVDC transmission development and multiterminal-HVDC-based transmission. HVDC technology is highly controllable, but also sensitive to faults and degraded modes. Achieving an efficient and robust AC/DC transmission system requires to develop a vision of HVDC role and functionalities in different situations. In addition to HVDC converter core control functions and DC grid protection strategies, a coordinated DC grid control layer is beneficial to supervise control modes toward overall AC/DC transmission system security and stability, as well as to ensure converter controls interoperability. This article offers a vision of what a robust AC/DC network can be, based on control and protection strategies that can be implemented via HVDC converter capabilities.