AN ENERGY-BASED APPROACH TO UNDERVOLTAGE LOAD SHEDDING

A novel effort to apply Lyapunov's energy methods towards developing a n energy based load shedding scheme in order to alleviate voltage inst ability is presented. An 'absolute' energy function is derived which e liminates the need to calculate the unstable equilibrium points (UEPs) and thus saves a considerable amount of computation time. The localiz ed and zonal nature of early voltage instability symptoms is studied a nd exploited. The functions are then used to generate three-dimensiona l (3-D) security region plots. Based on the proximity of the system st ate to the stability boundaries (that can be mapped on the 3-D plots), load shedding decisions can be carried out. The sensitivity of the de rived energy measure with respect to the real and reactive loads is al so calculated. From these sensitivity measures, a quantitative yardsti ck is obtained that determines the proportions of real and reactive lo ad to be shed. The method is computationally efficient and is easily i nterpreted, demonstrating a strong potential for real-time monitoring and control application.