Multiobjective Underfrequency Load Shedding in an Autonomous System Using Hierarchical Genetic Algorithms

Load shedding schemes are important approaches for operators to maintain the power system in a stable and reliable condition when the system suffers from a severe disturbance. The underfrequency relay, which is one of the load shedding facilities, provides a protection to crucial facilities when the system frequency declines to prespecified settings. This paper determines the percentage of load allowed to be shed and crucial parameters, including the number of stages and delayed time, for the underfrequency relay (81L). The hierarchical genetic algorithm is employed to minimize the amount of shed load and maximize the lowest swing frequency. An autonomous system with diesel generators and wind-power generators is employed to illustrate the applicability of the proposed method.