OffshoreDC: Electricity market and power flow impact of wind power and DC grids in the Baltic Sea

This report analyses offshore wind power development and offshore grid options in the Baltic Sea region. 27 GW of offshore wind power was assumed to be built in the Baltic Sea. The approach in this study links offshore wind power plant clustering, onshore connection point determination, offshore grid structure optimisation, unit commitment and economic dispatch simulation and power flow calculation together. The study compares the investment costs of different offshore grid topologies as well as the impacts of the offshore grids on the total operational costs of the power system, electricity production per fuel type, wind power curtailment and CO2 emissions. Annual electricity transmissions between regions as well as power flows in selected one-hour snapshots are studied as well. The results show that additional interconnections between price regions are clearly beneficial in the Baltic Sea region. Multi-terminal offshore grids may beat offshore grids consisting of two-terminal links in profitability, provided that high voltage direct current (HVDC) circuit breakers are available and their price is low enough. Annual electricity transmissions were generally from north to south and from east to west in the modelled area, which consisted of Nordic and Baltic countries, Germany and Poland. In power flow calculation, loop flows, which were not captured with the unit commitment and economic dispatch model, were detected inside and between Norway and Sweden. The grid model did not allow loop flows in Central Europe to be investigated.