Estimating the Voltage Stability Margin Using PMU Measurements

This paper presents a new method based on phasor measurement units (PMUs) for the estimation of voltage stability margin in a power system to increase operator's situational awareness. The method assumes a PMU measurement preprocessing technique as a priori in order to eliminate data inconsistency and uncertainty caused by random load disturbances. The measurements are then used in the computation of voltage stability margin based on the coupled single-port Thevenin equivalent model and the cubic spline extrapolation technique. Moreover, some practical operating constraints such as the generator reactive power limits are taken into account for practical assessment of the method's performance. Extensive case studies conducted on several standard IEEE test systems are used to demonstrate the effectiveness of the proposed method.