In this paper, the possibility of a generating system, which associates a variable speed wind turbine and a flywheel energy storage system, to participate to the ancillary services is investigated. The connection to a power grid of a farm including three of them is considered. A solution is proposed to allow wind generators to work as voltage sources with the help of a frequency droop. It is shown that the power generated by these systems can be controlled by fixing the power set point when they are connected to the grid, and that, in case of islanding, they can share the global load of the isolated network.