Stability of both voltage and frequency in power systems is the basis of the electricity generation. Load shedding is one the last strategies to stabilize a power system. However, the conventional load shedding schemes do not consider the reactive power as a direct participation in load shedding, which is essential for the voltage stability. To fill this gap, we propose a new combinational under frequency load shedding (UFLS) and under voltage load shedding (UVLS), considering reactive and active power simultaneously, and using non-dominated sorting genetic algorithm (NSGA II) in this paper. The location of bus loads, the reactive power and the active power consumption at each bus are used as GA control variables. This method is tested on the modified IEEE 39-bus system. The results of simulations validate the proficiency of proposed method in stabilizing the frequency and voltage of the power system.

Keywords: Power system stability, Under frequency load shedding, Under voltage load shedding, Genetic algorithm