Emission Constrained Thermal Unit Commitment Using Differential Evolution

Abstract

Unit commitment problem (UCP) is a nonlinear mixed integer optimization problem to schedule the operation of the generating units at minimum operating cost while satisfying the demand and other equality and inequality constrains. The UCP has to determine the on/off state of the generating units at each hour of the planning period and optimally dispatch the load and reserve among the committed units. Unit Commitment is the most significant optimization task in the operation of the power systems. During the last few years, emission control has become a problem of global concern due to the constantly increasing pollution of earth’s atmosphere. In order to reach the emission reduction targets imposed by the Kyoto Protocol, a limitation of the emissions produced by the generating units is needed. In this dissertation work Differential Evolution (DE) has been applied for the incorporation of the emission constraints in the solution of the thermal unit commitment problem. DE is simple but powerful and straightforward method for solving global optimization problems .The emission constraints are taken into account by integrating the cost of purchasing additional emission allowances, whenever the total system emissions exceed a predefined maximum limit, into the objective function of the unit commitment problem. Numerical simulations have proven the efficiency of the DE method.