Flexible steady-state security region of power system with uncertain load demand and soft security limits

This paper proposes a novel approach to calculate the steady-state security region of power systems with uncertain load demand and soft security limits. The fuzzy numbers are employed to express the uncertainty of load demands, and the confidence intervals are used to describe the different load variation states. A fuzzy linear optimization model is formulated to calculate the initial explicit security region for any load confidence interval. The final security region of a particular load confidence interval is the union of all initial security regions which confidence degrees are lower or equal than that particular confidence degree. Thus, the security region is flexibly changed with the load confidence degree. The numerical examples of IEEE 30-bus system are given to demonstrate the effectiveness of the proposed approach