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Interaction between the EMPS, EOPS and SHOP models

The EMPS model calculates water values for regional subsystems in a large interconnected power system, and simulates optimal operation for a number of hydrological years. The model may be used by large companies, operating on a nationwide or interstate basis, or by e.g. governmental bodies, concerned with national operation and planning issues.

The EMPS model includes a mid-term optimization module which can generate an individual endpoint water value description for use in SHOP. The endpoint description is given by a set of linear constraints the couples the medium and short-term planning process. The optimisation is based on a multi-scenario deterministic optimisation with a flexible planning period.

An essential result from the EMPS model, especially in deregulated markets, is the simulated market clearing or spot price for all hydrological years. This is often used as a statistical spot price forecast.

Because creation and maintenance of a nationwide or even multinational model requires substantial resources, this may not be a viable option for companies operating in a single area. If this area has interconnections with a larger market, the interaction may be described by a spot price forecast and transmission capacity. The EOPS model may then be used for system optimization and simulation. Spot prices may be simulated by a system operator, a governmental agency, a consulting firm etc. using the EMPS model. The underlying assumption is that the individual company is “small” compared to the market, and cannot influence the spot price by its actions.

In the same way as the EMPS model, the EOPS models can generate an endpoint water value description for individual reservoirs for use in SHOP.

SDDP (Stochastic Dual Dynamic Programming) based versions
SINTEF Energy Research also has a SDDP based model (ProdRisk) that solves the same problem as the EOPS model. In addition this model may also include functionality for risk management and dynamic hedging.  ProdRisk is used by several companies for medium-term (seasonal) scheduling.

Samplan is a SDDP based version of the EMPS model.

The SDDP based versions include all the physical details of the hydro system directly into the optimisation and does not include heuristics and rule based methods as the standard versions. The choice between SDDP based versions and standard versions are mainly a trade-off between accuracy and computation time.


  • EMPS is currently used for price forecasting, hydro scheduling and investment analysis by almost all of the major players (producers, consultants and TSO’s ) in the NordPool market area.
  • EOPS is used on a regular basis for operation planning purposes by approximately 25 medium sized power producers in Norway.
  • EOPS has been used for expansion planning in Norway for most of the major hydro projects since 1980. It has recently been used for projects in Vietnam, Nepal and Iceland.
  • SHOP, the newest product, has been taken into use by several power companies in Norway and Sweden. It has also been implemented as part of control centre software in other parts of the world.

Models are available on Windows and Unix platforms.