Control Strategies for Multi-Terminal DC Offshore–Onshore Grids Under Disturbance and Steady State Using Flexible Universal Branch Model

As the transition to clean energy accelerates, wind energy plays a crucial role in power generation, particularly in remote onshore and offshore locations. The integration of hybrid AC/DC networks with multi-terminal high-voltage direct current (MTHVDC) systems enhances power transfer capability and reliability. However, maintaining stable operation under both normal and disturbed conditions remains challenging. This paper applies the Flexible Universal Branch Model (FUBM) to hybrid AC/DC networks incorporating MTHVDC, providing a unified framework for power flow analysis. Unlike conventional methods that separately analyze AC and DC systems, the FUBM enables simultaneous modeling of both, improving computational efficiency and accuracy. Additionally, the paper introduces advanced control strategies to regulate active power transfer from offshore wind farms to onshore grids while maintaining voltage stability. The proposed approach is validated under steady-state and disturbance scenarios, including converter outages, within the CIGRE B4 system, which is a complex multi-terminal network interconnected with numerous converters. The results demonstrate the effectiveness of the FUBM in ensuring stable operation, offering new insights into unified power flow modeling. This study lays the groundwork for future advancements in AC/DC power systems with MTHVDC integration.