Voltage Stability Enhancement Using Local Measurements in Active Distribution Networks

The continuous increase in load demand and high penetration of renewable energy sources have driven electric distribution systems to operate close to their voltage stability boundaries. Hence monitoring voltage stability limits in distribution networks is essential to determine any required preventive or corrective remedial action. This paper presents a new method for voltage stability assessment of distribution networks using local measurements. In contrast to existing methods in the literature, which rely on phasor measurement units (PMUs) that are not usually available in distribution systems, to estimate Thevenin Equivalent (TE) for the power system, the proposed method uses the available measurements from smart meters without exclusively relying on PMUs to determine TE. The system equivalent is then used to derive a voltage stability index (VSI). The operating and security constraints at the node of interest are represented in the complex voltage plane which also allows the consideration of additional constraints such as the maximum and minimum voltages. The proposed method is implemented to a 17-Bus test system. The proposed indicator shows a linear behavior making it easier to estimate the distance to voltage instability and the magnitude of the required remedial action. Margins to maximum loadability can be easily estimated. The required reactive support to keep a specified level of voltage stability can also be determined with high accuracy.