Provided is a method for feeding electric power into an electricity supply grid having a grid voltage at a grid frequency having a grid nominal frequency. Feeding the electric power is performed by a converter-controlled feeding-in device, which may be a wind farm or a wind turbine. The feeding-in device feeds in an infeed current as electric AC current having a frequency, a phase, an infeed voltage and a fed-in power. The infeed voltage may be set. The method includes estimating a converter proportion in a grid section of the electricity supply grid that represents a ratio of power fed in by way of converters to overall fed-in power and controlling the infeed of the electric power depending on the estimated converter proportion.