Integrated TCSC Modeling and POD Controller Optimization for Stability Improvement in SMIB System

AbstractThis paper presents a comprehensive framework for the modeling, control design, andnonlinear optimization of a thyristor-controlled series capacitor (TCSC) to enhance bothtransient and small-signal stability in power systems. A detailed mathematical model of theTCSC is developed using current-injection and equivalent-reactance formulations, enablingaccurate representation of its dynamic interaction with transmission lines. Three hierarchicalcontrollers—steady-state power flow regulator, transient stability controller, and poweroscillation damping (POD) controller—are designed to address multi-timescale stabilitychallenges. Modal analysis, including eigenvalue evaluation, participation factors, andresidue-based sensitivity, is performed to identify critical oscillatory modes and determine themost effective control pathways. To further improve damping performance under nonlinearoperating conditions, the POD controller parameters are optimized using sequential quadraticprogramming (SQP), integrating time-domain simulation feedback into the optimization loop.The proposed methodology is validated on a single machine infinite bus (SMIB) system,where results demonstrate significant improvements in damping ratio, reduction in oscillationamplitudes, and faster settling of rotor angle deviations following disturbances. The findingsconfirm that optimized TCSC control provides robust and effective mitigation ofelectromechanical oscillations, offering a scalable solution for enhancing stability in largerinterconnected power systems.