Coordinated Optimal Power Flow and Control of a DC Overlay Grid over Asynchronous AC grids

Power systems are shifting towards a sustainable and interconnected future, where renewable power is transmitted over long distances to demand centers. This paper proposes a High Voltage Direct Current (HVDC) grid over a 6-zone AC/DC grid inspired by the European power system. The test case is analyzed with Optimal Power Flow (OPF) and Electromagnetic Transient (EMT) models in normal operations and for two contingency scenarios, namely loss of an HVDC link in the meshed AC/DC grid and loss of a radial HVDC link both in a congested hour. The results show how the HVDC grid helps avoid load curtailment when a link is lost in its meshed part. Furthermore, a robust control philosophy to maintain the power balance in hybrid AC/DC grids is discussed.