US 12,142,923 B2
Method and apparatus for detecting low-frequency oscillations
Aramis Schwanka Trevisan, Aurich (DE)
Assigned to WOBBEN PROPERTIES GMBH, Aurich (DE)
Appl. No. 17/258,128
Filed by Wobben Properties GmbH, Aurich (DE)
PCT Filed Jul. 4, 2019, PCT No. PCT/EP2019/067974
§ 371(c)(1), (2) Date Jan. 5, 2021,
PCT Pub. No. WO2020/007970, PCT Pub. Date Jan. 9, 2020.
Claims priority of application No. 10 2018 116 445.9 (DE), filed on Jul. 6, 2018.
Prior Publication US 2021/0281071 A1, Sep. 9, 2021
Int. Cl. H02J 3/24 (2006.01); G05B 13/02 (2006.01); H02J 3/38 (2006.01); H02J 3/48 (2006.01); H02J 3/50 (2006.01); H02J 13/00 (2006.01)
CPC H02J 3/24 (2013.01) [G05B 13/024 (2013.01); H02J 3/381 (2013.01); H02J 3/48 (2013.01); H02J 3/50 (2013.01); H02J 13/00002 (2020.01); H02J 2203/20 (2020.01); H02J 2300/28 (2020.01)] 16 Claims
OG exemplary drawing
 
1. A method for detecting low-frequency oscillations in an electrical supply grid having a grid voltage associated with a nominal frequency, comprising:
capturing at least one electrical signal from the electrical supply grid, the capturing including detecting a three-phase voltage of the grid voltage;
transforming the three-phase voltage into a d/q representation;
evaluating the transformed three-phase voltage using wavelet analysis, including:
generating a time-dependent frequency pattern based on analyzing a correlation between the transformed three-phase voltage and a wavelet mother function;
detecting a presence of a low-frequency component and a fundamental component in the time-dependent frequency pattern; and
in response to detecting the presence of the low-frequency component and the fundamental component in the time-dependent frequency pattern, determining that a low-frequency oscillation is present,
wherein the method is performed at a grid connection point where a wind power installation or wind farm supplies electrical current to the electrical supply grid, and
wherein the at least one electrical signal is a voltage at the grid connection point or a voltage proportional to the voltage at the grid connection point.