Newton-Raphson load flow model for hybrid multi-terminal HVDC systems consisting of voltage sourced converters and line commutated converters

This paper deals with a power flow model of a multi-terminal high voltage direct current (MTDC) transmission network consisting of both line commutated converters (LCCs) as well as voltage sourced converters (VSCs). Here, the DC and AC system equations, representing steady state, are solved simultaneously for better convergence. The method is tested on IEEE 57-bus test system and also on WSCC 9-bus system. In WSCC 9- bus system, an AC/DC system configuration (here called ´HVDC gateway´) consisting of HVDC lines connecting two AC grids, an offshore wind farm and an offshore load is considered.