Hydro and thermal scheduling by the decoupling method

The increased relevance of importing hydropower into some countries and utilities necessitates the application of planning tools that can adequately represent and analyse this new situation. The paper describes the decoupling method, which will permit the extension of an existing all-thermal optimization based scheduling program so that the role of importing of hydropower may be analysed. The advantage of this method is that the thermal system may be represented in considerable detail (with e.g. unit commitment, combined heat and power units and networks) and that the thermal system solution method is largely irrelevant. Therefore most utilities should be able to extend an existing all-thermal tool with a hydro part. The theoretical foundation of the decoupling method is described and the method is illustrated by examples.