A decomposition approach to nonlinear multi-area generation scheduling with tie-line constraints using expert systems

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Abstract
This paper presents a decomposition approach to multi- area generation scheduling problem. The objective is to mini- mize the operation cost of the entire system while satisfying the network constraints. Previous techniques did not consider the non-linear characteristics of generators, the topological connec- tions of power pools, or tie line limits. As this is a large-scale mixed integer-nonlinear optimization process, we use a two-layer decomposition to solve the problem. In the first decomposition, the problem is divided into several subproblems during the study period. The information that the problem sends to each sub- problem is the load demands of all areas at the corresponding hour and the output of the subproblem is the system operation cost at that time. The coordination factor of this layer of decom- position is the operation cost of the system in the given period, which should be minimum. The second layer of decomposition divides the previous subproblems further corresponding to con- trol areas in the power pool. The subproblem for each area receives system X and returns the area A. The coordinator at this level is the difference between systcni X and area X which should be zero except for areas that reach their generation limits. The interchange transactions among areas represent the trans- portation problem, embedded within the non-linear optimiza- tion process. The equivalent system concept has been adopted and the transmission losses are included in this study. A four- area system with each area consisting of 26 units is used to test the efficiency of the proposed algorithm.