Model-free angle stability assessment using wide area measurements

Abstract

A power system experiences different disturbances frequently where stability assessment is important for reliable operation. Synchronized data, from various buses, provided by wide area measurement system are resourceful for real-time stability analysis. Following a disturbance, generator rotors swing differently. Such rotor swings can be fast or slow based on the disturbance and system conditions, and may die down gradually (stable) or go on increasing (unstable). Therefore, rotor angle stability assessment is important for proper system operation. In this work, slow and fast swings are classified based on the relative rotor angle trend of the most disturbed generator pair. A predictive approach using auto-regression technique is used for stability assessment of fast swing. For slow swing, an index is proposed using Prony analysis. The proposed method identifies if the system is stable or moving towards instability, well in advance of actual instability point, enabling the system operator to take actions for preventing system collapse. No power system model is used, making the method fast and free from modelling errors. The proposed method is tested for New England 39 bus system, IEEE 118 bus system and 233 bus North Eastern Indian grid and found to be accurate. Comparative results with available method indicate the strength of the proposed method.