Direct connection of generators to hvdc converters: main characteristics and comparative advantages - Campos Barros, J G; Reis, Lineu Belico dos; Arrillaga, J; Bowles, J P; Kanngiesser, K W; Ingram, L; Daldegan, J; Ellery, E H; Goosen, P V; Joeijmakers, M J; Ivarson, C; Lima, A C G (Electra, 1993)