Application of the equivalent area model to multi-area generation scheduling with tie-line constraints

Abstract

In this paper, a new method is proposed for solving the multi-area generation scheduling problem. The problem includes unit commitment and economic dispatch modules. The objective is to obtain an economic operation without violating various system constraints. This is a mixed integer-nonlinear optimization process. In the proposed method, an artificial neural network (ANN) is used to obtain the initial unit commitment schedule for every area, with the assumption that there are no transmission flows among areas. In order to get the minimum operation cost for the entire system while preserving constrained units, areas and tie-lines, an iterative procedure is used to coordinate unit combinations and energy dispatch schedules. An expert system is employed to modify the initial unit commitment pattern of each area by reducing the number of committed units to a minimum while satisfying the area constraints. To consider tie-line limitations and incorporate transmission losses in the economic dispatch, an equivalent model for each area combined with the equal incremental cost method (λ method) is adopted for computing the generation assigned to every area and the power allocated to all committed units. A four-area system with 26 thermal units in each area is used to test the algorithm. The algorithm is implemented on a PC/386 and the experimental results show that the method is reliable, fast and computationally efficient.