Subhourly unit commitment with feasible energy delivery constraints

Unit commitment (UC) is one of the most important daily tasks that independent system operators or regional transmission organizations must accomplish in the electric power market. In the conventional UC problem, especially under a deregulated power system, the power schedule is usually taken as an energy schedule. However, this simplification may preclude the realization of the feasible energy delivery in real cases owing to the violation of ramping limits, as shown in the literature. If the power system integrates large-scale wind energy, the above “infeasible” energy delivery problem will be worsened, since wind power output will increase the variability of the “net-load” balanced by the thermal units. In this paper, a new UC model is provided that includes the consideration of “feasible” energy delivery under large-scale wind integration. The proposed model can give not only the optimal and feasible energy schedule to thermal units but also a precise ramping process for implementing this schedule. The problem is formulated as a mixed-integer linear programming problem; a 5-unit and a 36-unit system with 25% wind integration are used to test the proposed model. Finally, the numerical results support the conclusions above effectively.