Planning and Operation of Large Offshore Wind Farms in Areas with Limited Power Transfer Capacity

At many locations with excellent wind conditions the wind farm development is hindered by grid issues. Conservative assumptions are often applied that unnecessarily limits the wind power installation. This paper shows that significantly more wind power can be allowed by taking proper account of the wind power characteristics and facilitating coordinated power system operation. A systematic approach is developed for assessing grid integration of wind farms subject to grid congestions. The method is applied to a case of connecting offshore wind farms to regional grid with hydro generation (380 MW) and loads (75−350 MW). The tie to the main grid is via a corridor with limited capacity (420 MW). With conservative assumptions (i.e. no changes in scheduled hydro generation or control of wind power output) the wind power installation is limited to 115 MW. The system operation is simulated on an hourly basis for multiple years taking into account the stochastic variations of wind speed and hydro inflow as well as the geographical distribution of wind farms. The simulation uses a control strategy for coordinated power system operation that maximises wind penetration. By using the developed methodology the wind power capacity can be increased from 115 MW to at least 600 MW with relatively little income reduction from energy sales compared to a case with unlimited grid capacity. It is concluded that coordinated operation allows for the integration of surprisingly large amounts of wind power. In order to realize the increase in transfer capability, it is essential to take account of the power system flexibility and the stochastic and dispersed nature of wind power. The presented methodology facilitates this and represents a rational approach for power system planning of wind farms.