Flexibility and regulation capability of hydropower systems to balance large amounts of wind power : Influence of plant properties and hydrological conditions

The vast expansion of wind power in Sweden has raised questions about the regulation capability of existing hydropower resources. In this paper, the flexibility and relative regulation contribution of two large regulated rivers subject to increasing wind power penetration and different hydrological conditions is analysed through model-based simulations. A 28-day scenario is simulated using detailed models of the two hydropower systems, normally used at Vattenfall for day-ahead production planning. Numeric measures are introduced to measure flexibility and regulation contribution and two properties that characterise a good regulation plant are identified. It is found that the flexibility of a plant is correlated to the discharge factor and that the relative regulation contribution is nearly proportional to the available regulating power. Further it is found that large inflow of water reduces the flexibility in plants or reaches with a small discharge factor