Damping local and inter-area oscillations with synchronous compensators: a fundamental study

Abstract

The increase in the penetration of inverter-based generation in current power systems is reducing their short circuit currents and inertia. Synchronous compensators are being proposed and installed to address those issues. Recent events in the Continental European system have shown that the security of the power system may be at risk due to poorly damped inter-area oscillations. Synchronous compensators have also been proposed to damp electromechanical oscillations.This paper contains a fundamental study of the contribution of synchronous compensators to damping local and inter-area oscillations based on eigenvalue analysis of the small-signal model of simple power system models.Three power system models are considered. The first power system consists of a synchronous compensator connected to an infinite bus through its step-up transformer and a transmission line. The eigenvalue analysis shows that the electromechanical oscillation of the synchronous compensator cannot be affected by a power system stabilizer (PSS).The second power system consists of a synchronous generator in parallel with a synchronous compensator. The eigenvalue analysis confirms that although the joint electromechanical oscillation of both synchronous machines against the infinite grid can be damped by installing a PSS in the synchronous compensator, the most effective location of the PSS is the synchronous generator.The third power system is aimed at assessing the impact of synchronous compensators in the damping of inter-area oscillations in the presence of inverter-based generation. The eigenvalue analysis of the third power system shows that the synchronous compensator should be equipped with a PSS.