A Coordination Scheme of FACTS-Based WADC to Improve Small Signal Stability with Transient Stability Constraints in Multi-machine System

With the advent of smart-grid technology, the wide application of FACTS (Flexible AC Transmission Systems)based damping controllers exerts influences on both small signal stability and transient stability. Traditional Modal Analysis (MA) method can hardly meet the requirements of online applications. According to the inter-area oscillation mode to be studied, the multi-machine system can be equivalent to a two-machine system, and the Wide-Area Measurement System (WAMS) supports real-time dynamic equivalents. This paper explores the electric torque analysis (ETA) method in the two-machine system and the criteria of stability. An online coordination scheme of SVC-based Wide-Area Damping Controller (WADC) to maximize the damping ratio of the interarea mode with the transient stability constraints is presented in this paper. The scheme is treated as an optimization issue and a plant growth simulation algorithm (PGSA) is employed to search for the optimal controller parameters. A 4-machine-2-area benchmark is used to verify the effectiveness and advantages of the proposed scheme for online applications.