Study of STATCOM control for power swings damping improvement

The inherent low-frequency inter-area oscillations in a power system are usually lightly-damped. FACTS provides an effect way to improve the damping of such swings since it is capable of regulating the elements in the transmission system directly. This paper, with the background of the first Chinese ±20 MVAr STATCOM development in Henan Power Grid, presents comprehensive analysis and design of STATCOM-based damping control system. Some possible local input signals for the damping controller are evaluated through controllability, observability and self-interaction gain calculations at first. The local voltage compensated by STATCOM output current and driving-point reactance is elected considering the power flow variation of Henan Power Grid in different seasons. The controller gain is tuned through root locus analysis. Simulations with different local inputs are carried out and the results are consistent with the analytical conclusions. A method for online driving-point reactance identification is also proposed to improve the robustness of the damping controller