Design of UPFC Sub-Synchronous Oscillation Damping Controller Based on Modal Control

Sub-synchronous oscillation (SSO) is a specific dynamic behavior due to the coupling of mechanic and electrical parts of power system, which is a severe stability problem. Unified Power Flow Controller (UPFC), as the most advanced FACTS device, can restrain the system oscillation effectively through proper design. In this paper, UPFC's ability to damp SSO was studied first. An UPFC damping controller design method based on the modal control method is then proposed. Analysis of examples show that the method proposed in this paper can effectively suppress the sub-synchronous oscillation of power system and improve the stability of the system.