Large Scale Security Dispatching: an Exact Model

An exact optimal power flow model is presented for dispatching generation, transformer taps, and generator voltages to minimize operating costs while guaranteeing a steady state secure operating point after a contingency. A full ac power flow model is used, which permits including voltage and reactive power constraints in the optimization. The technique of this paper is unique in that all of the voltage and power constraints of all selected contingencies are enforced in a single optimization. No cycling between contingency evaluation and optimization is necessary in order to update the list of active constraints. Cases which have divergent power flow solutions are included in the problem with no difficulty. All non-islanding outages are guaranteed to converge to a feasible solution. The optimization algorithm solves a sequence of linearly constrained subproblems using a quasi-Newton search direction. The dispatching algorithm is tested on the IEEE 118 bus system power system.