Structural imbalances in the Nordic power system — Causes, future expectations and remedies

Structural (or deterministic) imbalances are caused by the lack of coherence between on the one hand continuously varying demand and on the other hand scheduled changes of generation at the hour shifts. In the Nordic system this is exacerbated by fast ramping HVDC interconnections and a large share of fast reacting hydro plants. The analysis is focused on the effect of the expected doubling of the HVDC interconnection capacity between the Nordic and continental systems. The paper uses model calculations to estimate the present "raw" imbalances, i.e. the gross imbalances that would occur without control actions. First results for the 2012 system are shown and the effect of reducing the Market Clearing Period to 15 minutes is analyzed. Subsequently the expected 2020 situation is analyzed. With increased ramping, as desired by the market, the results show a significant increase in imbalances. Finally it is shown how a reduction to a 15 minutes Market Clearing Period improves the situation in 2020.