Geir Warland

Long-term hydro-thermal scheduling including network constraints

This paper presents a method for treating transmission network bottlenecks in a stochastic hydro-thermal scheduling model. The model is designed for long- and medium-term scheduling of hydro-thermal power system operation, where decisions are made for aggregated regional subsystems or areas. The aggregate area representation allows simulation of large hydro systems with a relatively high degree of detail, thus making the model well suited for comprehensive studies on a national and international scale.

Handling balancing power in a power market with a large share of hydropower

This paper presents a model well suited for analysis of power systems with a large share of new renewable in combination with hydropower and pumped-storage hydro. The model is designed for a detailed hydropower representation and can be used with hourly time resolution. The model solves the detailed dispatch of hydropower in two steps. First it uses a heuristic model for weekly decisions where the goal is to find the target for end reservoir levels. Then the problem is re-solved as a formal optimization problem where the goal is to fully utilize the flexibility in the hydropower system within the week.

Hydrothermal scheduling in Norway using stochastic dual dynamic programming; a large-scale case study

We test the stochastic dual dynamic programming (SDDP) approach on a system an order of magnitude larger than previously published studies. The analysis shows that the SDDP-approach can be applied to very large system sizes to solve the hydropower scheduling problem through formal optimisation and obtain individual decision variables for every reservoir. However, this can be very time-consuming compared to other existing models based on other principles. The results from our SDDP-based model compare favorably to an aggregation-disaggregation model which is in operational use in the power market when using statistical inflow series as input to the models.

Simulating equilibrium prices in oligopoly power markets

One of the main objectives of deregulation has been to achieve more efficient power systems. Exercise of market power can significantly increase prices in the power market thereby reducing the efficiency. This makes it important for regulatory bodies to survey and intervene if the market is malfunctioning. In hydropower systems this is extra difficult to reveal because the resource for the supply side is stochastic in its nature. In this paper a method for simulation of the price establishment in power systems is suggested. The characteristics of this model are discussed using the English power market as a case.

Verification of a model for handling of pumped storage for large scale market balancing

With an increasing amount of intermittent renewable energy sources, such as wind and solar energy, there will also be an increasing demand for balancing power. Hydropower, and pumped storage in particular, can be an efficient way of providing the needed flexibility. Hydropower scheduling, particularly for large power systems with large amounts of hydropower, is a very complex task. Therefore there are few models that really are capable of handling detailed analysis in large power systems like the Nordic or European. In this paper we present a simple test-case where two different models suitable for analysis of balancing power are compared. The first model, called ProdRisk, is based on state of the art SDDP-methodology and is used as the reference model. Calculation time, however, limits the number of reservoirs this model can handle satisfactorily. The second model, called ReOpt, is an improvement of an extensively used market power simulator capable of handling real size power markets. Both models are designed for detailed hydropower representation and are both capable of handling pumped storage, but the first model has a mathematically more correct representation of the stochastic optimization. The main idea of this paper is to illustrate the potential ReOpt has for analyzing the use of hydropower and pumped storage as balancing power in large power systems.