Provided is a method for exchanging electric power with an electricity supply grid that has a grid frequency using a converter-controlled generation unit that may be a wind power installation or a wind farm, at a grid connection point. The method includes exchanging electric power depending on a control function. The electric power includes active and reactive power and the control function controls the power depending on at least one state variable of the electricity supply grid. It is possible to switch between a normal control function and a support control function, different from the normal control function, as the control function. The normal control function is used when it has been recognized that the electricity supply grid is operating stably and the support control function is used when a grid fault or an end of the grid fault has been recognized.