On Embedded Energy Storage for High Penetration of Wind Power

It is recognised that to enable high penetration of wind power it is essential for modern wind farms to meet some technical requirements. These requirements are specified, or planned to be included, in grid codes by some utilities around the world. In this paper it is shown that having an Embedded Energy Storage (EES) unit, a battery bank, in a wind turbine can help to meet these requirements and to reduce the overall wind farm development and system integration costs. After a review of wind power integration and power system load frequency control, two cases are presented. These are based on (a) the statistics of the wind speeds measured at Dunstaffnage, Scotland, (b) the manufacturers' data for two turbine generators, and (c) some mild assumptions used for the calculations. In the first case, for the same amount of wind energy annual output and a specified frequency control requirement: the delta production constraint, a wind farm of 50 wind turbines can be replaced by 10 wind turbines with an EES in each of them plus 33 ordinary wind turbines. In the second case, again for the same amount of wind energy annual output, wind turbines with EESs can meet the absolute power constraint and at the same time the ratings of transformers, transmission lines and other equipments associated with a wind farm development can be reduced, leading to a significant reduction in costs. Wind farms with such wind turbines can also provide some vital support in an emergency, for example, the event in Denmark on the 8th January 2005, when the total wind power output dropped suddenly from the scheduled 1843MW to 126MW, due to the shut down of most wind turbines under strong winds.