英语翻译

英语翻译
I.INTRODUCTION
WORLDWIDE transmission systems are undergoing
continuous change stemming mainly from the strong
increase in power transfers between systems,opening of the
market for delivery of cheaper energy to customers,and economic
and ecological constraints which delay the building
of new transmission facilities.Since the construction of new
transmission lines cannot keep pace with the growing power
plant capacity and energy demand,operators are looking at
ways to utilize the existing power lines more efficiently,operating
the grid in ways not originally envisioned.The need
for more efficient power systems management,and the fast
development of power electronics based on new and powerful
semiconductor devices,have given rise to innovative technologies,
such as voltage source converters (VSC)-based FACTS
controllers [1].
Among the VSC-based controllers commissioned and installed
in several transmission systems around the world,
the VSC-HVDC system,also called HVDC-Light® or
HVDC-Plus®,is a recent technology which has demonstrated
to be successful in enhancing the power system’s controllability
[2].In contrast to traditional HVDC transmission,which
uses phase-commutated converters,HVDC links using voltage
source converters can not only control active power flow but
also provide an independent voltage regulation to the connected
ac system because the surplus or deficit in reactive power can
be accommodated by the VSC.The first project at Näs Head
on the Southern tip of Gotland started operation in November
1999.This has been followed by several VSC-HVDC projects
around the world.Examples of such installations can be found
in Sweden,Australia,the U.S.,México,and Norway [2].