US 11,899,050 B2
Wind turbine and method for detecting low-frequency oscillations in an electrical supply grid
Aramis Schwanka Trevisan, Aurich (DE); and Kaveh Malekian Boroujeni, Bremen (DE)
Assigned to Wobben Properties GmbH, Aurich (DE)
Appl. No. 17/270,820
Filed by Wobben Properties GmbH, Aurich (DE)
PCT Filed Aug. 23, 2019, PCT No. PCT/EP2019/072601
§ 371(c)(1), (2) Date Feb. 23, 2021,
PCT Pub. No. WO2020/039077, PCT Pub. Date Feb. 27, 2020.
Claims priority of application No. 10 2018 120 768.9 (DE), filed on Aug. 24, 2018.
Prior Publication US 2021/0341523 A1, Nov. 4, 2021
Int. Cl. G01R 23/177 (2006.01); H02J 3/24 (2006.01); H02J 3/38 (2006.01)
CPC G01R 23/177 (2013.01) [H02J 3/241 (2020.01); H02J 3/381 (2013.01); H02J 2300/28 (2020.01)] 19 Claims
OG exemplary drawing
 
1. 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.