An Effective Load Shedding Scheme to Mitigate Voltage Collapse Using a Multi Objective Optimization Technique and BFO

Among different protection schemes that save power system stability against a variety of disturbances, load shedding is considered as an effective and last-resort tool to avoid voltage instability. This paper proposes a special protection system design to minimize the load curtailments necessary to restore the equilibrium of operating point with relaxation of both steady state and dynamic restrictions. An optimal load shedding approach is proposed to enhance voltage stability employing a combination of modal analysis and Bacterial Foraging Optimization (BFO). As a corrective control action after contingencies the proposed approach is organized as a multi-objective optimization problem which reveals the best location and the lowest level of load shedding for special protection systems (SPSs) in the direction of improving the voltage stability margin as well as the voltage profile. The load shedding activation time that mitigates power system voltage collapse in spite of load curtailment must be indicated by dynamic simulation to prevent both over load shedding and voltage instability. The proposed approach is applied to Gharb and Bakhtar areas of the Iranian transmission network for its annual peak load at 2011. Simulation results verify the effectiveness of the proposed scheme in comparison with the current scheme.