Non-Linear Programming Based Optimal Power Flow (N-OPF) for Bulk Transmission Grid: Modeling and Comparative Study

Optimal power flow is generally formulated as a non-convex and non-linear programming (NLP) problem. Traditionally, the OPF problem is solved in transmission systems through approximations and/or relaxation techniques. Such methods lead to infeasible and inaccurate solutions. This paper provides a numerical analysis of the performance of different NLP OPF formulations, such as the Interior Point Method (IPM), Sequential Quadratic Programming (SQP), and Alternating Direction Method of Multipliers (ADMM) in terms of, feasibility, optimality, and scalability. The performances are evaluated using small (IEEE 9 bus and 14 bus), medium (IEEE 30 bus, 39 bus, and 57 bus), and large (IEEE 118 bus) test cases.