I. Introduction
The objective of the unit commitment problem (UCP) is to determine the optimal scheduling of the generating units along with their generation levels at minimum operating costs while satisfying the system and unit constraints. The decision variables include the binary unit commitment (UC) variables and real-valued economic dispatch (ED) variables. The UC variables describe the ON/OFF status while the ED variables indicate the generation levels of the generators at each hour of the planning period. The dimension of the problem increases rapidly with longer planning time and increased size of the power system. Solving this high dimensional problem is a challenging task.