A FACTS technique for converting existing AC transmission into HVDC (and back)

Abstract

The paper brief is one out of the first approaches in Turkey to popularize HVDC-light transmissions. It deals with three areas. (1) Lab design and PSCAD modeling of a special bridge controlled AC-DC three load (star-delta) rectifier. It uses a group of 9 valves (instead of a group of 6 valves of common bridge), three lines of former AC transmission, the earth and three DC loads between the lines and earth (or a star-delta inverter). (2) Lab design and PSCAD modeling of a special controlled bridge DC-AC star-delta inverter between three DC source and AC network. It also uses a group of 9 valves (instead of common group of 6 valves), three input DC lines (and the earth) and three outputs AC transmission lines. (3) Comparison of the bridges construction and modeling results of traditional HVDC-light transmission (6 valves rectifier, traditional DC line and 6 valves inverter) and designed AC-DC-AC transmission (9 valves rectifier, AC line and 9 valves inverter). The proposed star-delta rectifier and inverter can be implemented in common electrical applications such as HVDC transmission, supply of isolated loads, asynchronous grid connection, infeed of small-scale distributed generators (DG), infeed to city centers, for DC grids, converting the AC lines into HVDC light lines, etc.