EMPS model strategy and calibration

In the strategy part, the expected value of the water stored in the reservoirs (water value) is computed as a function of the reservoir level and time. This water value methodology is based on stochastic dynamic programming. The water value calculation requires a very simplified model representation of the hydropower system. In order to achieve acceptable computation time, the hydropower system has to be aggregated, into a single equivalent power plant as well as a single equivalent reservoir (the aggregate model) for each modelled area. Still, the computation time would be unacceptable for a system consisting of more than two hydropower areas. Thus, the process must be split into several individually smaller tasks.

The strategy part in the EMPS model is based on water value calculations for each decoupled area Fig. 1. The reciprocal coupling between the areas is considered in an iteration process, where the calculated water values are used as the decision basis for simulations of the entire coupled system.

The parameters affecting the water values are not automatically computed based on the
simulation results from the previous iteration. They must be calibrated by the user.
This is done by tuning the load (firm power) and occasional power market scaling
correction factors, using rules described later in this section.

Fig. 1: Calibration process of the EMPS model.