Enhancing Stability of Long-distance Transmission System by TCSC and SSSC Distributed Control

Impact of controlled series compensation devices (TCSC and SSSC) and automatic generator control on small-signal stability indices and various steady-state operations for long-distance intersystem power transmission is investigated. Simultaneous coordination of TCSC and AVR/PSS power plant generator settings for wide range of operating conditions is carried out in order to obtain uniform parameters of control devices. Acceptable margin of aperiodic and oscillatory stability is obtained up to the limits applying only controlled series reactive power compensation. Additional feedbacks by intermediate substation phasors (WAMS data) in TCSC and SSSC control system is proposed. Practicability of implementing static series synchronous compensator for small-signal stability enhancement is analyzed. It is shown that oscillation damping of transients occurs faster, since control is carried out by series and shunt components.