An Improved Time-Frequency Analysis Method based on the Energy Gridding for Offshore Wind Turbines

摘要

The Hilbert-Huang transform (HHT) has been used in many fields fortime-frequency analysis of the non-linear and non-stationary signal. Butwhen implementing the HHT to analyze the measurement signals fromactual offshore wind turbines, due to the large rigidity and weak waveenergy, the results will suffer a serious mode-mixing problem andcontain a lot of noises which will lead to a bad result. In this paper, a newtime-frequency analysis method based on the Hilbert transform isintroduced, the Intrinsic mode functions (IMF) obtained by empiricalmode decomposition (EMD) is redefined by introducing a combinationof state-space model and energy gridding. To demonstrate the proposedmethod, one numerical example of three slow varying frequencycomponents was used. Specifically, a field test on an offshore windturbine located in the Putuo of Zhejiang Province of China is introduced,and measured data are used to verify the effectiveness of the proposedmethod. The result demonstrates that the proposed method has a betterperformance when implemented on the offshore wind turbines.