Abstract: A system and method are provided for enabling multi-functional support of an extant synchronous alternating current (AC) grid. At least one extant electricity source and at least one extant electricity sink are connected by two or more high-voltage direct current (HVDC) transmission circuits connected in turn in series with each other with at least one pair of HVDC circuits interconnected through an intervening high-voltage AC (HVAC) point of interconnection. One or more of the HVDC transmission circuits includes a 2-terminal or a multi-terminal transmission link. A 2-terminal HVDC circuit is dedicated to connecting with the electricity sources and sinks.

Abstract: A method of segmenting a power distribution network which comprises a plurality of AC power generating stations synchronously interconnected by AC power transmission paths is disclosed. The stations operate within associated market sectors and are subject to associated market rules. The method includes identifying all transmission paths which extend between differing ones of the sectors and, in each of said transmission paths so identified, segmenting the path by inserting a controllable DC link at a selected location in the path. Each of the sectors is then operated asynchronously. Power flow and counter-flow between the sectors is controlled by controlling the DC links.