Dynamics Constrained Optimization of Electrical Power Systems
The prevalent method in the power industry to ensure an economic and secure operation is to solve a nonlinear optimization problem, commonly referred to as ‘AC Optimal Power Flow’ in the power system parlance. An optimal power flow solution ensures ‘steady state security’, i.e., the current operating point and the operating point(s) post some equipment outage(s) do not violate any operational constraints. However, it does not provide any information about ‘dynamic security’, i.e., the ability of the system to withstand transients or dynamics ensuing large disturbances, for example short-circuit faults. Dynamic security is a concern for system planning and operations experts because of significant higher penetrations of renewable energy resources, most of which are electronically coupled to the grid, are expected in the future. This situation presents new technical challenges, particularly in the reduction of system inertia through the displacement of conventional generation resources during light load periods.
In this work, we present the solution of the AC optimal power flow incorporating system dynamics. The analysis of power system dynamics involves the solution of differential-algebraic model of the power system. Resultantly, our problem has a DAE-constrained optimization formulation. Our solution approach uses an aggregation of constraints on system dynamics to reduce the dimensionality of the problem, and sensitivity calculation via adjoints. Preliminary results on a test 9-bus power system are presented.