As a new generation of DC transmission technology,voltage source converter based high voltage direct current(VSC-HVDC)system is being developed and applied worldwide.The engineering technology,engineering application and future development for VSC-HVDC are summarized and analyzed,respectively.A comprehensive technical analysis is made of VSC-HVDC including main circuit design,converter topology,control and protection system,VSC-HVDC cable,converter valve testing etc.to point out the technical barriers and future development directions.This paper also gives an overview of the application and status quo of VSC-HVDC projects in the world.With an eye to the characteristics and demands of future grid development,the engineering application trend of VSC-HVDC projects is demonstrated,which shows that the VSC-HVDC technology has a critical role to play in future grid development.