Toward a More Reliable System for Contingency Selection in Static Security Analysis of Electric Power Systems

Root event‐based dynamic space pruning algorithm for contingency screening of transmission system

“…When Loss(X) does not exceed Loss(X root i ), I(Loss(X)) = 1; otherwise, I(Loss(X)) = 0. Constraints (1), (2) and (5) describe the N − k subspace of root event X root i . Constraint (6) calculates the load loss of event X.…”

“…The screening of root events in the complement subspace is similar to the risk ranking issue in [21]. However, model (P2) is constructed with additional constraints (3) and (5) to form the N − k complement subspace according to the proposed space pruning principles.…”

“…In addition to (P3), two potential schemes described below can be considered to further accelerate the screening of the first root event. The first scheme is to use the simple severity indices [5] to select severe events as the initial guess for root events. Although these indices are not designed to screen contingencies that cause significant load loss, some root events can be found by solving the optimal load shedding problem for these events.…”

“…Case 5: The critical events are identified by the ant colony optimisation (ACO) algorithm in [5] that uses the line overloading index. The parameters of the ACO algorithm are set as that in [5], namely, quantity of ants = 3, knapsack size = 6, quantity of pheromone = 40, pheromone evaporation factor = 9%, number of iterations = 1000. Case 6: The Monte Carlo method is used to search for critical events that cause the load loss.…”

“…The impact of contingency events on the security and reliability of the transmission system has been studied in the past decade. Security analysis is performed with the severity indices of bus voltage and line overloading [3][4][5]. The contingency screening is to identify critical events that result in the severe violation of operational limits at the post-contingency scenarios.…”