A generalised approach for efficient computation of look ahead security constrained optimal power flow

We consider a generalised comprehensive Look-ahead Security-constrained Optimal Power Flow (LASCOPF) formulation under the N−1 contingency criterion over multiple dispatch intervals. We observe that the number of decision variables varies quadratically with the number of intervals. To improve scalability, we propose a reduced LASCOPF formulation for which the number of decision variables varies only linearly. We extend these formulations to the N−k contingency criterion. For reduced LASCOPF we observe that the number of decision variables varies with the number of k-permutations of contingencies. To improve scalability, we propose a formulation that is further reduced to vary only with the number of k-combinations. Also, we show that our formulations can be extended simply to model recovery from the corresponding outages. Furthermore, we present LASCOPF under the N−1 contingency criterion using DC and AC power flow under generator contingencies. We prove that, barring borderline cases, solving the reduced formulation is equivalent to solving the comprehensive formulation. We extend these results to the N−k contingency criterion. Finally, we present numerical results on the IEEE 14 bus, IEEE 30 bus and IEEE 300 bus test cases, and the 1354 bus part of the European power system using AC power flow to demonstrate the computational advantage of the reduced formulations under the N−1 and N−2 contingency criteria.