  Increased power demands, push for economics and limited investment in grid
infrastructure have led utilities to operatepower systems closer to their
stability limits. Voltage instability may trigger cascade tripping, wide-area
voltage collapse and powerblackouts. Real-time voltage stability monitoring
possible with deployment of phasor measurement units (PMUs) is essential totake
proactive control actions and minimize the impact on system. This paper
presents a novel online algorithm for a) hybridperturbation analysis-based
voltage stability monitoring (HPVSM), b) including Q-limit in voltage stability
index and c) real timesecurity analysis using voltage stability index. HPVSM
based voltage stability index is computed using the data obtained fromlinear
state estimator and PMU measurements. Typically measurement-based schemes
ignore the impact of generator Q-limitsand security analysis is not feasible.
The proposed HPVSM based index considers the impact of generator Q-limits
violationsby anticipating the critical generators using real-time PMU
measurements. Contingencies are ranked using the proposed voltagestability
index for security analysis. Results simulated for the 9-bus WECC, IEEE 14, 57
and 118 bus systems highlights thesuperiority of the proposed method in real
time voltage stability and security analysis

Systems and Control;Systems and Control