US 11,658,490 B2
Wind energy system and method for identifying low-frequency oscillations in an electrical supply network
Kai Busker, Groβefehn (DE); Angelo Mendonca, Wilhelmshaven (DE); and Aramis Schwanka Trevisan, Aurich (DE)
Assigned to Wobben Properties GmbH, Aurich (DE)
Appl. No. 17/258,130
Filed by Wobben Properties GmbH, Aurich (DE)
PCT Filed Jul. 5, 2019, PCT No. PCT/EP2019/068107
§ 371(c)(1), (2) Date Jan. 5, 2021,
PCT Pub. No. WO2020/008036, PCT Pub. Date Jan. 9, 2020.
Claims priority of application No. 10 2018 116 446 (DE), filed on Jul. 6, 2018.
Prior Publication US 2021/0159705 A1, May 27, 2021
Int. Cl. H02J 3/46 (2006.01); H02J 3/38 (2006.01); G05B 15/02 (2006.01); H02J 3/24 (2006.01)
CPC H02J 3/381 (2013.01) [G05B 15/02 (2013.01); H02J 3/241 (2020.01); H02J 3/46 (2013.01); H02J 2300/28 (2020.01)] 19 Claims
OG exemplary drawing
 
1. A method for identifying low-frequency oscillations in an electrical supply network having a line voltage associated with a nominal line frequency, the method comprising:
detecting at least one electrical signal of the electrical supply network as at least one test signal;
filtering and/or transforming the at least one test signal into at least one check signal;
obtaining a gradient signal by:
temporally differentiating the at least one check signal, or
obtaining a difference of temporally separated values of the at least one check signal;
determining whether the gradient signal meets a predetermined criterion; and
in response to determining that the gradient signal meets the predetermined criterion, identifying a presence of a low-frequency oscillation, wherein:
transforming the at least one test signal into the at least one check signal includes transforming the line voltages of the electrical supply network in three phases and current fed into the electrical supply network in three phases into a voltage signal, an active power signal and a reactive power signal as a voltage check signal, an active power check signal or a reactive power check signal,
temporally differentiating the at least one check signal includes temporally differentiating the voltage check signal, the active power check signal and the reactive power check signal to obtain a voltage gradient signal, an active power gradient signal and a reactive power gradient signal, respectively, or obtaining the difference of the temporally separated values of the at least one check signal includes obtaining a difference of temporally separated values of the voltage check signal, the active power check signal and the reactive power check signal to obtain the voltage gradient signal, the active power gradient signal and the reactive power gradient signal, respectively,
the voltage gradient signal, the active power gradient signal and the reactive power gradient signal are checked for the presence of the low-frequency oscillation, and
the presence of the low-frequency oscillation is identified in response to the low-frequency oscillation being found at least in the voltage gradient signal and the active power gradient signal or in the voltage gradient signal and the reactive power gradient signal.