Evaluating Modelling Approaches for State-Dependent Environmental Constraints in Medium-Term Hydropower Scheduling

This paper addresses the inclusion of state - dependent environmental constraints in medium-term scheduling of hydropower plants with reservoirs. The reservoir handling and release plans of hydropower production can lead to dry river sections and lakes, create barriers for fish mitigation and impact terrestrial ecosystems. In Norway, many reservoirs are also used for recreational purposes. Environmental constraints are imposed to facilitate synergies in reservoir usage and ensure high enough water levels. Some environmental constraints are challenging to mathematically include in hydropower scheduling models, due to nonconvex characteristics or binary logic. State-dependent constraints can make the problem formulation nonconvex, and are therefore not included in existing scheduling tools. This paper compare different approaches for representing such constraints in medium to long-term scheduling models and evaluate the difference in optimality.