Re-synchronization strategy for the synchronous power controller in HVDC systems

Frequency and voltage regulation are required to support the grid under different scenarios. In order to handle these scenarios, classical control strategies demand complex systems to fulfill these requirements. However, synchronous controllers are trending strategies to contribute with frequency and voltage regulation functionalities without the requirement of external elements. Among these strategies, the Synchronous Power Controller (SPC) is exceptional, due to its ability to operate a power converter in grid-forming or grid-feeding mode while providing grid supportive functionalities. Nevertheless, to avoid high power oscillations at the point of common coupling during grid connection, a grid synchronization strategy is mandatory. This paper proposes a synchronization strategy to adjust the angle, voltage amplitude and frequency of the converters controlled with the SPC. The proposed strategy has been simulated in an HVDC system with the SPC controlling the grid connected converter. Simulation results demonstrate the validity and effectiveness of the proposed strategy.