Adaptive Scheme for Minimal Load Shedding Utilizing Synchrophasor Measurements to Ensure Frequency and Voltage Stability

Abstract

This article presents a new scheme for load curtailment in the power system under critical contingencies that may pose a threat to the frequency and voltage stability of the system. The proposed scheme is based on a two-stage load-shedding strategy. In the first stage, disturbances have been classified based on the computed value of the disturbance power, and the load-shedding requirement in the system has been assessed based on the frequency stability, as well as dynamic voltage stability, conditions. The scheme assumes the availability of real-time data from a synchrophasor-based wide area monitoring and control system. A dynamic voltage stability criterion has been developed in this stage using a voltage stability risk index to assess the voltage stability in real time. Suitable locations for the load curtailments have been chosen according to the voltage stability risk index, which is calculated at each load bus. After the system attains transient stability, the second stage of the proposed scheme determines the optimal redispatching of generators for recovering the loads as much as possible, which had been curtailed in the first stage following the contingency. Performance of the proposed scheme has been tested on a 10-machine, New England 39-bus system, and the results are compared with a conventional under-frequency load-shedding scheme and an adaptive load-shedding scheme.