Design of a combined converter-switch for converting existing AC transmission into HVDC (and back)

摘要

The paper brief is one out of the first approaches in Turkey to popularize VSC Transmission. It deals with: (1) lab design and PSCAD modeling of a special bridge controlled AC-DC three load (star-delta) rectifier. It uses 9 group of valves (instead of 6 group 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 9 group of valves (instead of common 6 group valves), three input DC lines (and the earth) and three outputs AC transmission lines. Comparison of the bridges construction and modeling results of traditional VSC 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 VSC transmission, etc.