Coordinated control of multi-terminal VSC-HVDC transmission for large offshore wind farms

Future offshore wind farms will have large power ratings and will be situated much further offshore than current projects. An outstanding issue to be solved is long distance transmission of bulk, fluctuant and widely dispersed wind power to onshore AC grid. The main objective of this paper is to investigate the coordinated control scheme of multi-terminal VSC-HVDC (MTDC) transmission for large offshore wind farms. Five MTDC topologies are sorted out from North Sea Super Grid network and a four-terminal topology is adopted for control scheme investigation, which is related to power delivery control and fault ride through control. The control effect and power system stability is evaluated by two dynamic simulation cases based on PSCAD/EMTDC, which correspond to wind power fluctuation and disconnection of one grid side converter station.