Ant-Colony Optimization for Optimal Pump Scheduling

Abstract

This paper presents a method to solve the pump scheduling problem using Ant-colony optimisation. In the past, many researchers have attempted to solve the problem of optimal pump scheduling for complex water distribution systems. Despite the practical importance of the problem, many of the methods published have shortcomings range from lack of generality in the representation of state variables to excessively high computational effort. The present work considers the minimization of cost of pumping as the objective and incorporates the constraint on number of pump switches into the representation. The main emphasis of this work is on restricting the search space and reducing the number of function evaluations. Solutions to pump scheduling problem are, usually, encoded using a binary string showing the state (on/off) of each pump during each time interval. Using binary pump schedules and Ant-colony optimisation, a new method for optimal pump scheduling is developed. The representation of a solution is modified to restrict the number of pump switches to a specified value and to suit the application of Antcolony optimisation. A comparison of the results obtained using the proposed method was compared with those obtained using Evolutionary algorithms.