Optimization of SO2 and NOx Emissions in Thermal Plants

This paper presents an environmental dispatch algorithm in a hydrothermal system and addresses the problem of minimization of emissions of SO2 and NOx caused by the operation of thermal plants. Several models have been used to represent the emissions function. In this paper, we first construct a quadratic model for both emissions: E(P)=α+β P+γ P2, where P is the power generated and the parameters were computed via the least-square criteria from several tests at thermal plants. We shall see that the problem consists in the minimization of a functional F(z) within the set of piecewise C1 functions that satisfy boundary conditions and non-holonomic inequality constraints. An optimal control technique is applied and Pontryagin’s theorem is employed. The algorithm proposed is easily implemented using the Mathematica Package and is applied to a sample system to illustrate the results obtained.