Hybrid HVDC system for power transmission to island networks

A hybrid system, comprising a line commutated thyristor high-voltage direct current (HVdc) converter and a static VAR compensator, is proposed in this paper for the connection of networks with no synchronous generation to a main grid. The proposed system combines the robust performance and low capital cost and power loss of a line-commutated HVdc converter, with the fast dynamic performance of a voltage-source-converter (VSC)-based transmission system. The paper describes the principles and control strategies of the proposed system. PSCAD/EMTDC simulations are presented to demonstrate the robust performance and to validate the proposed system during various operating conditions such as black-start, variations of load or generation, and ac fault conditions.