Network-free voltage stability assessment of power systems using phasor measurements

In this paper two different methods to estimate the proximity of the system to the Maximum Loading Point (MLP) are proposed. They are compared with a specific method recently published that uses the Cubic Spline Extrapolation (CSE) for estimating the MLP. All three methods are based on tracking the Thévenin Equivalent (TE) of the system as seen from the load buses using data from Phasor Measurement Units (PMUs). The main advantages of this class of methods are their simplicity and computational efficiency since they are independent from network's model and they are only based on local measurements, making them a very good option for both Wide-Area Monitoring Systems (WAMS) and local applications. The methods are intended to be used in real time environments, and take into account some operational aspects like system's conditioning and nonlinearities introduced by reactive power generation limits.