A Model-Free Approach for Emergency Damping Control Using Wide Area Measurements

Rescheduling methods for mitigation of poorly damped power swings depend on a model-based evaluation of eigenvalue sensitivities and are slow to implement. This paper proposes an approach for an online model-free implementation of modulation-type control using Wide Area Measurement System (WAMS). Such a control measure can act as a primary line of defense before the slower rescheduling-type measures are taken. The proposed control measure utilizes special properties of swing modes derived analytically from a simplified system model to 1) synthesize a modal feedback signal as the input to the controller and 2) tune the controller parameters for adequate damping improvement, in a model-independent manner for certain FACTS devices and HVDC links. For a power system stabilizer (damping controller in a synchronous machine excitation system), the extent of model information required is limited to that of the well-known GEP(s) transfer function and inertia constant of the concerned synchronous machine. Case studies with detailed system models provide the necessary proof-of-concept.