Medley Multiobjective Harmony Search Algorithm: Application on a water resources management problem

During the last years multiobjective optimization has attracted the interest of those involved in the optimization field. Real problems usually involve the simultaneous optimization of several objectives, a fact that makes multiobjective optimization a priority. In 2001 Harmony Search Algorithm (HSA), a new optimization technique was presented. This novel metaheuristic is based on the observation that the aim of music creation is the quest of the perfect state of harmony. This quest is relevant to the optimization procedures that seek the optimum solutions. Since then, HSA was used successfully in various single – objective optimization problems and from 2010 and on, applications of HSA in multiobjective optimization (MO–HSA) increase in numbers. In the present paper MO–HSA is implemented towards the optimization of a pump scheduling, multiobjective problem. Additionally, Medley HSA, a powerful multiobjective variant, is introduced by the authors and compared to the traditional method. The application concerns the optimum management of a pumping station which consists of five pumps. The objectives include the simultaneous minimization of the energy consumption and the electric energy’s consumption peak and the minimization of the pumps’ wear. At the same time the pumped quantity must satisfy the demands of the urban area. The problem was solved for three different sizes of reservoirs. Varying the size of the reservoir causes a change in the search space and the Pareto – front. Moreover a sensitivity analysis of both Algorithms was made, based on the number of iterations/run. The optimal solutions that both methods detected are presented in 3D graphs along with analysis, comparison and comments.