LargeScaleSecurity Dispatching: anExactModel

An exactoptimalpower flow model is presented for dispatching generation, transformer taps, and generatorvoltagesto minimizeoperatingcosts while guaranteeing a steady state secure operatingpoint after a contingency. A full ac power flow model is used,which permitsincludingvoltage and reactive power constraintsin the optimization.The technique of thispaper is uniquein thatall of the voltageand power constraintsof all selectedcontingenciesare enforcedin a singleoptimization.No cyclingbetween contingencyevaluationand optimizationis necessary in order to updatethe list of active constraints. Cases whichhave divergentpower flow solutions are includedin the problem with no difficulty. All non-islanding outagesare guaranteedto converge to a feasiblesolution.The optimization algorithmsolves a sequence of linearlyconstrainedsubproblemsusing a quasi-Newtonsearch direction. The dispatching algorithmis testedon the IEEE 118 bus system power system.