An Analytical Adaptive Load Shedding Scheme Against Severe Combinational Disturbances

Abstract

To diminish damaging consequences of power system major disturbances, under frequency load shedding (UFLS) plans are devised so as to prevent power networks from collapse. Since load shedding scenarios in conventional UFLS plans are specified regardless to voltage stability criteria, they cannot bring desired outcomes at the event of severe and combinational contingencies. In these circumstances, the location of load drops, in addition to their amounts, should be determined as well. This paper presents a two-unit wide-area adaptive load shedding scheme based on synchrophasors. In the first unit, an adaptive precise system frequency response (SFR) model is developed, by the help of which, the appropriate amount of load rejections is determined such that the dynamic and steady state frequency limitations are fulfilled. Incorporation of both static and dynamic loads into the adaptive SFR model results in a negligible error in calculations. Specifying the best location of load drops based on suitable voltage stability criteria is the main task of the second unit. These two units are executed in a parallel way; the computational burden of the proposed approach is thus tractable for real world applications. The new method is successfully testified in the IEEE 39-bus system and Khorasan network.