Mohammad Reza Jannati Oskuee - Phd Student, Electrical Engineering Department, Azarbaijan Shahid Madani University, Tabriz, Iran
Karim Roshan Milani - MSc at Electrical Engineering, East Azarbaijan Electric Power Distribution Company, Tabriz, Iran
Sajad Najafi - Associate Professor, Electrical Engineering Department, Azarbaijan Shahid Madani University, Tabriz, Iran

Economic load dispatch (ELD) problem is to find the optimal generation of power by various power plants respect to the operation costs; it means that conventional ELD only aims to minimize the total fuel costs but no concern made for environmental protection requirements. But, regards to stricter regulations on environmental issues, some strategies must be devised in order to reduce the pollutant emissions produced by fossil-fueled electric power plants. In this regards, emission reduction must be defined as an objective function. Also, with considering the transmission system losses the solution to the ELD problem can improve real power dispatch. In order to minimize the power loss, another objective is defined for this purpose. So, in this paper in order to operate the power plants in the best possible condition multi-objective functions are proposed and have been solved using NSGA II (Non-Dominated Sorting Genetic Algorithm). Also in this paper, the valve-point loading effects are modeled. One of the most important advantages of the proposed multi-objective formulation is that it obtains several non-dominated solutions. However, there is a paucity of objective methodologies for ranking the obtained non-dominated solutions. So, in this paper, Data envelopment analysis (DEA) is suggested for the purpose. In other words, in this paper firstly NSGA II is applied to the ELD problem, and then the obtained non-dominated solutions are prioritized by DEA. The significant advantage of using DEA is that, there is no need to impose the decision maker's idea into the model. And ranking is done, based on the efficiencies of the non-dominated solutions. So, using DEA gives a realistic view of solutions and the provided results are for all, not for a specific decision maker.

Economic Load Dispatch, Multi-Objective, Environmental Issues, Transmission Loss, valve-point effect, Data Envelopment Analysis, Objective approach