Power system scheduling with coupled transactions

The purchasing and selling of power among electric utilities are important activities because proper transactions can result in significant cost savings. Transaction decisions, however, are difficult to make since transactions are coupled with the scheduling of generators, making the problem very complicated. Furthermore, decisions have to be made in almost real time in view of the competitiveness of the power market. In this paper, integrated transaction and scheduling is analyzed from a purchase utility´s viewpoint for a power system consisting of thermal units and two coupled transactions. A separable problem formulation is constructed, and a three-level Lagrangian relaxation framework is developed to solve the problem. Numerical results based on Northeast Utilities data sets show that the algorithm is efficient, and near-optimal solutions are obtained