Gomis-Bellmunt, O.; Liang, J.; Ekanayake, J.; King, R.; Jenkins, N. "Topologies of multiterminal HVDC-VSC transmission for large offshore wind farms" Electric power-systems Research 81, 2, pp. 271 - 281. 2011 DOI: 10.1016/j.epsr.2010.09.006