The modern electric utility industry is currently more
and more attention to HVDC transmission as a practical
alternative to HVAC transmission. It is useful supplement to
rapid and smooth power flow control, more economical choice
and small power loss for long transmission systems. An electric
power system with DC links requires a special analysis for power
flow study that takes their characteristics into account. This
paper presents an AC-DC load flow algorithm to solve a power
flow problem with DC links. This algorithm is tested using
medium and long transmission standard test systems. Digital
results using the proposed sequential method are compared w ith
a previous work. The effect of load change in HVDC control
parameters is studied. A comparison between HVAC and HVDC
transmission systems based on power losses are also performed.