Unit commitment in thermal power systems with long-term energy constraints

A method is described for optimizing short-term unit commitment considering energy constraints obtained from a long-term optimization. The constraints arise because, for example, many electrical utilities must fulfil energy supply contracts with other utilities or with fuel suppliers, and energy prices may change during the year or depend on the consumed electric energy. The presented method solves this complex task in two steps. The first step calculates a long-term, e.g. yearly, operation schedule with daily energies allocated to each unit. These daily energy constraints of the long-term optimization are then incorporated in the second step for the daily unit commitment. Special attention is given to the coordination between long-term and short-term optimization