So far, numerous scientific works have been developed by
researchers dealt with the optimal operation scheduling under
different loading conditions and objectives. At first, conventional
economic scheduling has been proposed as a solution for the
optimization problem through finding an optimal set of generators
to satisfy load demand and operational constraints in an economical manner [6e8]. Due to the environmental concerns and
pollutants emission from traditional fossil fuel units, singleobjective optimization could no longer be satisfactory in the
mentioned problem. To involve emission as a separate goal, multiobjective optimization techniques have been developed in articles
in order to choose a definite number of units for supplying the load
under a certain condition taking into account minimum levels of
cost and emission for grid operation [9e13]. Recently, evolutionary
algorithms such as GA (Genetic Algorithm), PSO (Particle Swarm
Optimization) and so on have been increasingly proposed for
solving the optimization problem because of their inherent
nonlinear mapping, simplicity and powerful search capabilities
[13e18]. Hybrid approaches such as Fuzzy-based evolutionary