After occurrence of some disturbances in power system that causes the sever imbalance between generation power and electrical load, the power system frequency begins to decrease. To prevent power system frequency instability and stop the frequency decay below the power system allowable frequency limitation, load shedding schemes should be utilized by applying under frequency load shedding relays. In this paper, power system behavior is modeled as a mathematical mixed integer programing (MIP), moreover the parameters that are required for UFLS relays setting are determined optimally in order to minimize the load shedding amount throughout power system in compliance with certain restrictions. The obtained results have been verified by Simulation studies.

Keywords: Under frequency load shedding, Optimization, Mixed integer program, Disturbance, Frequency stability.

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