This paper describes the control design of the Santo Tome' back-to-bac
k HVDC link. The Santo Tome' HVDC converter will be the second dc link
asynchronously connecting the Argentina and Brazil power systems. Thi
s paper focuses on the design of the reactive power control, automatic
power control, load frequency control, power modulation control, auto
matic frequency control, and automatic synchronizing control functions
of the 50 MW dc link. Time simulation and frequency domain results ar
e included to illustrate the system response and verify the adequacy o
f the controllers performance in achieving stable operating conditions
.