high insulation level and difficulties in design and transportation for large capacity transformers
bipolar connection are adopted in voltage source converter based high voltage direct current(VSC-HVDC)projects
which is firstly introduced in ±320 kV/1 000 MW Xiamen VSC-HVDC project. Taking Xiamen project as an example
the study on system design for large-capacity VSC-HVDC project with bipolar connection is presented. Firstly
the single line diagram is optimized for multiple operation modes
in order to improve system reliability. Secondly
as the margin for main equipment is generally small in large capacity VSC-HVDC project
main circuit parameters are calculated accurately so that small-capacity insulated gate bipolar transistor(IGBT)can support large-capacity power transfer. Finally
the transient characteristics of VSC-HVDC systems with both kinds of connections are compared. The conclusion is that the transient overvoltage decreases while the transient current increases. The safety of IGBT under overcurrent is guaranteed by adopting the accurate analytical transient current calculation method and the optimized layout design. The practical work is done to show the feasibility and effectivity of the proposed design method.