Abstract: A method for detecting low-frequency oscillations, in particular subsynchronous resonances, in a grid is provided. The method includes recording a series of measurements, having measurement points, of a grid variable over a measurement time period, for performing a frequency analysis and multiplying the series a time-dependent sinusoidal test function for the same measurement time period. The test function is characterized by a test frequency and a test angle as phase angle. The series for each measurement point is multiplied by the test function in order to obtain a test product for each measurement point. The method includes adding the test products taking into consideration the mathematical sign thereof to give a product sum, and evaluating, depending on the product sum, whether the series of measurements has a low-frequency oscillation having a frequency in the region of the test frequency and a phase angle in the region of the test angle.

Abstract: A method for attenuating low-frequency oscillations in an electrical power supply grid by means of a feed device which feeds into the electrical power supply grid, in particular a wind power installation, wherein the electrical power supply grid has a grid voltage and a grid frequency, comprising the following steps: picking up a grid signal having the low-frequency oscillations, splitting a total frequency range of the grid signal in which oscillations to be attenuated are to be expected into a plurality of partial frequency ranges, each having a lower and an upper range frequency, performing in each case one frequency analysis of the grid signal for each partial frequency range in order to identify in each case one or more oscillations having an oscillation frequency in the partial frequency range, if present, identifying a low-frequency oscillation to be attenuated as target oscillation depending on the frequency analyses of all of the partial frequency ranges, detecting the target oscillation at least acc

Abstract: A method for attenuating low-frequency oscillations in an electrical power supply grid by means of a feed device which feeds into the electrical power supply grid, in particular a wind power installation, wherein the electrical power supply grid has a grid voltage and a grid frequency, comprising the following steps: picking up a grid signal having the low-frequency oscillations, splitting a total frequency range of the grid signal in which oscillations to be attenuated are to be expected into a plurality of partial frequency ranges, each having a lower and an upper range frequency, performing in each case one frequency analysis of the grid signal for each partial frequency range in order to identify in each case one or more oscillations having an oscillation frequency in the partial frequency range, if present, identifying a low-frequency oscillation to be attenuated as target oscillation depending on the frequency analyses of all of the partial frequency ranges, detecting the target oscillation at least acc

Abstract: A method for detecting low-frequency oscillations, in particular subsynchronous resonances, in a grid is provided. The method includes recording a series of measurements, having measurement points, of a grid variable over a measurement time period, for performing a frequency analysis and multiplying the series a time-dependent sinusoidal test function for the same measurement time period. The test function is characterized by a test frequency and a test angle as phase angle. The series for each measurement point is multiplied by the test function in order to obtain a test product for each measurement point. The method includes adding the test products taking into consideration the mathematical sign thereof to give a product sum, and evaluating, depending on the product sum, whether the series of measurements has a low-frequency oscillation having a frequency in the region of the test frequency and a phase angle in the region of the test angle.