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- there are no major transmission constraints within the area
- the area has some degree of homogenous hydrological characteristics
Optimization
Optimization in the EOPS model is obtained through the calculation of incremental water values in an aggregate-reservoir model of the system with the help of stochastic dynamic programming.
Once the water values are calculated, a detailed simulation is performed with all relevant details modelled. Here total system costs are minimized week by week for each weather scenario, combining a linear problem formulation with an advanced, rule based drawdown strategy to decide a best possible allocation of water between individual reservoirs.
The model also includes a medium term optimization module which can generate an individual endpoint water value description for use in short term scheduling. The endpoint description may be either in the form of individual water values or a set of linear constraints that couples the medium and short-term planning process. The medium term module is based on multi-scenario deterministic optimization, with a flexible planning period. A linear network flow algorithm is used for this purpose.
Running Modes
EOPS may run in two essentially different modes:
Isolated mode:
All relevant elements in the power system are modelled. An internal "market clearing price" will primarily depend on marginal costs of e.g. thermal power, dual fuel boilers, curtailment costs or other market options available, combined with the availability of hydropower. This mode is well suited for systems that operate isolated from other systems, or where exchange with other markets is either on a fixed price or fixed volume basis.
Market mode:
The system under consideration is connected to a power market. Prices in this market are exogenously given, e.g. by calculation with the EMPS model. This mode is used in deregulated markets, or in systems with major interaction with other power markets. In this mode both market price and inflow are modelled as stochastic variables. The producer is implicitly considered to be a price taker in the market.
Hydro Description
The hydro system is described using modules containing:
- A reservoir with attributes
- Storable and non-storable inflow
- Constraints on storage and water flow
- Waterways for overflow, bypass and production
- A power plant
Hundreds of plants in the same or different river basins may be modelled within the same system.
Some tasks EOPS may perform:
- Long term operational scheduling of hydro power
- Maintenance planning decisions
- Medium term scheduling – Calculating marginal water values and cuts for use in short term scheduling
- Analyzing the operational consequences of hydro plant outages
- Probability distribution of production potential and operational income
- Thermal power generation and availability of surplus power
- Analysis of overflow losses
- Reservoir operation
- Import from and export to other areas
- Analysis of energy shortages
- Calculation of market clearing prices in isolated systems
- Testing the quality of e.g. inflow statistics