Tight MIP Formulations of the Power-Based Unit Commitment Problem

Abstract

This paper provides the convex hull description for the basic operation of slow- and quick-startunits in power-based unit commitment (UC) problems. The basic operating constraints that are modeled forboth types of units are: 1) generation limits and 2) minimum up and down times. Apart from this, the startupand shutdown processes are also modeled, using 3) startup and shutdown power trajectories for slow-startunits, and 4) startup and shutdown capabilities for quick-start units. In the conventional UC problem, powerschedules are used to represent the staircase energy schedule; however, this simplification leads to infeasibleenergy delivery, as stated in the literature. To overcome this drawback, this paper provides a power-basedUC formulation drawing a clear distinction between power and energy. The proposed constraints can be usedas the core of any power-based UC formulation, thus tightening the final mixed-integer programming UCproblem. We provide evidence that dramatic improvements in computational time are obtained by solvingdifferent case studies, for self-UC and network-constrained UC problems.QS 2014</p