Secure and optimal operation of hybrid AC/DC grids with large penetration of offshore wind

This study focuses on the the reliability of HVDC grids, analysing the secure and optimal operation of transmission systems consisting of both HVDC (High Voltage Direct Current) and HVAC (High Voltage Alternating Current) interconnections, with high penetration of offshore wind, taking into account the system spinning reserves. While AC systems are usually operated N-1, it is not clear which should be the criteria for operating DC grids. The consequences of operating a DC grid with different levels of security are addressed and the expected cost of operation and wind power curtailment over one year are determined, taking into account the probability of failure of the different power system components. A study case, based on the CIGRE HVDC Test System, is presented, showing the system response to the outage of different elements and its effect on the cost of operation. Generic wind profiles and representative AC generation parks are used to model the system behaviour over a complete year.