Wide-Area Measurement-Based Voltage Stability Assessment by Coupled Single-Port Models

Abstract

As the power system becomes more stressed and the penetration of intermittent renewable energies increase, voltage stability assessment (VSA) becomes a key concern for maintaining and enhancing the security of bulk power systems. Physically, the phenomenon of voltage instability is indeed caused by an uncontrollable drop in system voltage after being subjected to a disturbance. This deterioration may ultimately result in voltage collapse that has been responsible for several blackout incidents. So far, a vast number of methods ranging from simple static techniques to complex dynamic methods have been proposed for performing VSA. More recently, with wide deployment of synchronized phasor measurement units (PMUs), PMU-based wide area measurement system (WAMS) has attracted lots of interests from both academia and industry. In this chapter, recent developments of measurement-based coupled single-port models will be presented for VSA. Generally speaking, the concept of the coupled single-port model is to decouple a mesh power grid into several single-port local equivalent models with considering extra coupling impedances. By collecting real-time PMU measurements in each individual load bus, the reactive power response derived from the extended Ward-type equivalent model can be applied to eliminate the reactive power mismatch of the existing single-port model. Meanwhile, these parameters of the Thevenin equivalent circuit in the existing single-port model will be modified by a mitigation factor to improve the model accuracy of VSA. Since the proposed method is simple, several voltage stability indicators can be easily extended with slight modifications. Simulations are conducted on two test systems, including IEEE 57-bus and IEEE 118-bus test systems, to validate the accuracy of the proposed method.