Provided is a method of feeding electric power at a grid connection point into an electric power grid having a grid voltage using a converter-controlled feeder, in particular using a wind energy system and/or of a storage unit. The method includes feeding the electric power into the electric power grid in a normal operating mode when no grid fault or grid malfunction has been detected in the electric power grid, and switching to a fault mode when a grid fault or grid malfunction has been detected, in which the grid voltage is increased or decreased. In the normal operating mode an active current is fed in in order to feed active electric power into the grid and if the need arises a reactive electric power is additionally fed into the grid by a reactive current. The combination of the active and reactive currents results in an apparent current.