Operating Experience with Modulation of the Pacific HVDC Intertie

Implementation and operating experience with a control system which modulates power on the Pacific HVDC Intertie to damp oscillations on the parallel Pacific AC Intertie is described. This system significantly improves the damping of the Western interconnected power system, which has had a long history of periods of negatively damped oscillations. The successful operation of dc modulation was a key factor in permitting an increase in the rating of the Pacific AC Intertie from 2100 MW to 2500 MW. This uprating results in large economic and energy conservation benefits.