Wind turbine and method for detecting low-frequency oscillations in an electrical supply grid

A method for detecting low-frequency oscillations in an electrical supply grid having a line voltage and associated with a rated line frequency, comprising:

• recording at least one series of measurements having a plurality of measurement points of a grid variable over a measurement time period for performing a frequency analysis on the at least one series of measurements;
• multiplying each measurement point of the at least one series of measurements by a time-dependent sinusoidal test function for the measurement time period to obtain a product for each measurement point, wherein the test function has a test frequency and a test angle as phase angle;
• summing a plurality of products of the plurality of measurement points to produce a product sum, wherein summing the plurality of products includes retaining a plurality of signs of the plurality of products, respectively;
• and
• determining, based on the product sum, whether the at least one series of measurements has a low-frequency oscillation having an oscillation frequency in a region of the test frequency and a phase angle in a region of the test angle, wherein the oscillation frequency is below the rated line frequency.