scholarly journals Fast frequency response of inverter-based resources and its impact on system frequency characteristics

2020 ◽  
Vol 3 (5) ◽  
pp. 475-485
Author(s):  
Lining Su ◽  
Xiaohui Qin ◽  
Shang Zhang ◽  
Yantao Zhang ◽  
Yilang Jiang ◽  
...  
Keyword(s):  
Frequency Response ◽  
Frequency Characteristics ◽  
System Frequency

scholarly journals Detection and localization of multiple small damages in beam

2021 ◽  
Vol 13 (1) ◽  
pp. 168781402098732
Author(s):  
Ayisha Nayyar ◽  
Ummul Baneen ◽  
Syed Abbas Zilqurnain Naqvi ◽  
Muhammad Ahsan
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Signal To Noise Ratio ◽  
Moving Average ◽  
A Priori ◽  
Damage Index ◽  
High Signal ◽  
Frequency Range ◽  
Spatial Locality ◽  
System Frequency

Localizing small damages often requires sensors be mounted in the proximity of damage to obtain high Signal-to-Noise Ratio in system frequency response to input excitation. The proximity requirement limits the applicability of existing schemes for low-severity damage detection as an estimate of damage location may not be known  a priori. In this work it is shown that spatial locality is not a fundamental impediment; multiple small damages can still be detected with high accuracy provided that the frequency range beyond the first five natural frequencies is utilized in the Frequency response functions (FRF) curvature method. The proposed method presented in this paper applies sensitivity analysis to systematically unearth frequency ranges capable of elevating damage index peak at correct damage locations. It is a baseline-free method that employs a smoothing polynomial to emulate reference curvatures for the undamaged structure. Numerical simulation of steel-beam shows that small multiple damages of severity as low as 5% can be reliably detected by including frequency range covering 5–10th natural frequencies. The efficacy of the scheme is also experimentally validated for the same beam. It is also found that a simple noise filtration scheme such as a Gaussian moving average filter can adequately remove false peaks from the damage index profile.

A low-order system frequency response model

1990 ◽  
Vol 5 (3) ◽  
pp. 720-729 ◽  
Author(s):  
P.M. Anderson ◽  
M. Mirheydar
Keyword(s):  
Frequency Response ◽  
Order System ◽  
Response Model ◽  
System Frequency ◽  
Low Order
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