An innovative approach to generations scheduling in large-scale hydro-thermal power systems with fuel constrained units

A methodology for short-term unit commitment is proposed. The development of the solution method is based on the Lagrangian relaxation approach. Thermal, fuel-constrained, and hydro units are modeled in the formulation of the problem, and restrictions on fuel and water utilization as well as limits on the storage levels of reservoirs are included. This procedure is especially applicable to systems whose unit commitment solution is sensitive to changes in the Lagrangian multipliers. In this regard, the method incorporates the following special features. First, a set of upper bounds is added to limit the excess in the spinning reserves at different periods during the search for a feasible suboptimal solution. Second, a revised economic dispatch algorithm is introduced in the final stage of the method. This algorithm identifies unnecessarily committed units in the generation schedule of a large power network and provides the solution for the economic allocation of system demand among the committed units