Unit commitment with transmission security and voltage constraints

In this paper, optimal power flow (with transmission security and voltage c onstraints) is incorporated in the unit commitment formulation. Using Bende rs decomposition, the formulation is decomposed into a master problem and a subproblem. The master problem solves unit commitment with prevailing cons traints, except transmission security and voltage constraints, by augmented Lagrangian relaxation. The subproblem minimizes violations of transmission security and voltage constraints for a commitment schedule given in the ma ster problem. Since transmission constraints are decoupled from voltage con straints in the subproblem, the subproblem could further be decomposed into two smaller subproblems. The resulting transmission subproblem minimizes t ransmission flow violations for the worst contingency case by adjusting uni t generation and phase shifter controls. The corresponding reactive subprob lem minimizes voltage constraints by reactive power generation and tap chan ging controls. In the case of transmission flow or voltage infeasibility, B enders cuts are produced for unit commitment rescheduling. The iterative pr ocess between the master problem and the subproblems provides a minimum pro duction cost solution for generation scheduling while satisfying the constr aints. A comprehensive unit commitment software package is developed using Visual C++. A 36-unit system in the IEEE-118 bus network is used to demonst rate the efficiency of the method.