An economic dispatch algorithm of combined cycle units

The economic dispatch (ED) problem is defined as that of finding an optimal distribution of system load to the generators in order to minimize the total generation cost while satisfying the total demand and generating-capacity constraints. The different combinations of combustion turbines and steam turbines in a combined cycle (CC) unit produce multiple states and each state has its own unique cost curve. Therefore, in performing ED, we need to be able to shift between these cost curves. However, there is another, more serious problem: the cost curve is not convex for some of these states. As a result, ED of CC units must use special techniques like, for example: Complete Enumeration, Merit Order Loading, Genetic Algorithm (GA), Evolutionary Programming (EP), and Particle Swarm (PS) (see [1] and [2]). The three former techniques (GA, EP, and PS) involve a stochastic searching mechanism, and it should be noted that these heuristic methods do not always guarantee obtaining the globally optimal solution: they only provide an approximate solution for the non-convex optimization problem. In this paper we present a new technique for solving the ED problem of CC units. The technique, de-