RISS 검색 - 국내학술지논문

1
Numerical analysis of the spatial distribution of equivalent wind speeds in large-scale wind turbines

Shuting Wan,Lifeng Cheng,Xiaoling Sheng 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2
The effects of wind shear and the tower shadow contribute to periodic fluctuations in the wind speed and aerodynamic torque, which cause several problems. This study develops an equivalent wind speed model for large-scale, n-bladed wind turbines that includes the wind shear and the tower shadow effects. The comprehensive model is used to derive the disturbance components of wind speed caused by wind shear, the tower shadow, their synthesis, and the equivalent wind speed and to delineate their spatial distributions in the rotor disk area. Simulation results reveal that the effects of wind shear, the tower shadow, and the equivalent wind speed on the disturbance components fluctuate periodically and are closely related to the wind turbine correlation parameters, such as the rotor radius, hub center height, tower radius, distance from the tower midline to the blade, wind shear exponent, and blade number.
2
Compound fault diagnosis of bearings using improved fast spectral kurtosis with VMD

Shuting Wan,Xiong Zhang,Longjiang Dou 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11
The fast spectrum kurtosis (FSK) algorithm can adaptively identify resonance bands of a signal, and fault characteristics can be extracted by analyzing the selected frequency bands. However, in practical applications, the bearing failure may be composed of various faults (inner ring/outer ring/rolling element) and the faults may be located in different resonant bands. Due to the interference between different fault components and noise, the weak components may be submerged when FSK is used to deal with compound fault signals. To improve the accuracy of an FSK processing compound fault located in different resonance bands, an improved FSK method combined with the variational mode decomposition (VMD) is proposed. First, the parameters (number of components K / penalty factor a ) in the VMD decomposition are selected, and the original compound fault signal is preprocessed by VMD decomposition, so that the original signal is decomposed into K variational intrinsic mode function (VIMF) components. The resonance center bands of these signals are different from each other, so the different fault information is located in different VIMF. Finally, each VIMF component is calculated by FSK. Through the simulated and experimental analysis, the method can accurately identify the resonance bands, and identify the weak fault characteristics of compound bearing fault.
3
The FERgram: A rolling bearing compound fault diagnosis based on maximal overlap discrete wavelet packet transform and fault energy ratio

Shuting Wan,Bo Peng 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1
Compound fault features of the rolling bearing are difficult to separate and extract. To address this problem, the present paper proposed a diagnosis algorithm, namely FERgram, on the base of maximal overlap discrete wavelet packet transform (MODWPT) and fault energy ratio (FER). First, a group of frequency band signals are gained after MODWPT processing the initial vibration signal. Second, FER is chosen as the evaluation index, and then the FER values of each frequency band signal are calculated and used to generate FERgram. The frequency band signal with the maximum FER value containing plentiful fault information is chosen for envelope analysis. Finally, the fault type is determined by contrasting the prominent frequency component of the envelope spectrum with the fault feature frequency. The feasibility and superiority of the FERgram method are verified by four signals and four comparison methods. The results show that the FERgram method can effectively extract and accurately diagnose the compound fault of rolling bearing.
4
Blade aerodynamic asymmetry fault analysis and diagnosis of wind turbines with doubly fed induction generator

Xiaoling Sheng,Shuting Wan,Lifeng Cheng,Yonggang Li 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.10
The blade aerodynamic asymmetry fault must be detected early due to its important effect on wind turbines. This paper develops a fault diagnosis approach based on the current and power characteristics of a Doubly fed induction generator (DFIG). First, the blade aerodynamic characteristics and the influence on the nacelle and tower vibration under an aerodynamic asymmetry fault are analysed and an improved Blade element moment (BEM) method considering the blade, nacelle and tower vibration is proposed to calculate the aerodynamic torque. Then, the electrical characteristics of the DFIG are analysed. The output power is shown to decrease with oscillation when aerodynamic asymmetry occurs. In addition, the same modulation harmonic frequency as the blade rotating frequency exists in the stator and the rotor current. Finally, simulations under constant and stochastic wind conditions via MATLAB/Simulink show the effectiveness of the proposed method in this paper.

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