Reservoir ramping constraints#
Reservoir ramping constraints limits the volume change of a given reservoir between specified time periods. Constraints on maximum up and down regulation are handle separately and can be time dependent.
The constraint limiting reservoir changes on a given reservoir l at time t, are of the form given in the equation below. Where V is reservoir volume,\(\Deltaπ_{π,t}^{up}\) , and \(\Deltaπ_{π,t}^{down}\) is respectively maximum up-regulation and down-regulation for reservoir l at time t:
Note that this constraint also include slack variables to ensure that a feasible solutions always are found. The slack variables have high costs and are only used if necessary.
Limits on change can either be specified as volume change per time interval or as Meter Above Sea level (MASL) change per time interval. MASL change per time interval requires a reservoir curve description (volume as function of MASL) for the specific reservoir. Maximum reservoir change between hours (load period) will only be used if sequential (-sekv) option is used. If not sequential (-sekv) option is used maximum ramping is maximum change between weeks, the model will then recalculate input.
Ramping constrains are included in the cuts/water values. Because the new ramping constraints only affect reservoir volume which already has a cut coefficient , the change only affects the calculation of existing cut coefficients. The only change is adding the dual value for the ramping constrains to the old coefficient: