Advanced Controls of HVDC Interconnection for Ancillary Services Support

This paper proposes advanced controls to improve ancillary services of High Voltage Direct Current (HVDC) interconnections. The converters control is a synchronverter-based control (SHVDC). The main goal is to improve the SHVDC controls to comply with the Grid Code Requirements (GCR) set by the Tunisian grid operator, the Tunisian Company of Electricity and Gas (STEG). Two control strategies are proposed. A local/decentralized control and a global/centralized control. The local control regulates voltage and frequency at the HVDC converters point of connection (PoC) to the grid. Frequency and voltage controls are based on conventional droop controls. The centralized control responds to control signals, emanating from the transmission system operator, to render the SHVDC system participate in the grid support as conventional generators. The proposed controls feature operation with energy reserves, emergency control and P/Q ramp-ups and ramp-downs controls. Centralized and decentralized controls are successfully implemented and tested on the HVDC interconnection between Tunisia and Italy.