Quadratic Approximation of PV Curve Path Based on Local Phasor Measurements, in Presence of Voltage Dependent Loads.

Drawing PV curve path by Continuation Power Flow (CPF) runs is the commonly used method for voltage stability studies. Although time-consuming, it can carefully determine the distance between the current operating point and the collapse point. To drive the power flow equations, the bus admittance matrix and the electrical characteristics of the generators and loads are needed. The presented method in this paper is based on this fact that, PV-curves are approximately quadratic functions and become exactly quadratic in close neighborhood of the collapse point. So, to draw the PV curve path at a load bus, the calculation of all points is not needed. Instead, using some points, the other points can be determined by the quadratic approximation of the PV curve path. The needed points can be determined using the local measurements of the voltage magnitude and the active power at the corresponding load bus. Now, having static load characteristics, the Saddle-Node Bifurcation (SNB) point can be predicted. The simulations performed on the IEEE 30-bus test system show that the voltage collapse point can be determined using only local measurements (the thing is usually claimed in model-based methods).