scholarly journals Coupled vibration characteristics of a submarine propeller-shaft-hull system at low frequency

2019 ◽  
Vol 39 (2) ◽  
pp. 258-279
Author(s):  
Feng Chen ◽  
Yong Chen ◽  
Hongxing Hua
Keyword(s):  
Power Flow ◽  
Large Scale ◽  
Low Frequency ◽  
Vibration Characteristics ◽  
Propeller Shaft ◽  
Coupled Vibration ◽  
Transfer Path ◽  
Great Consistency ◽  
Frequency Excitation ◽  
Submarine Hull

The coupled longitudinal and transverse vibration characteristics of a submarine propeller-shaft-hull system at low frequency are studied in this paper. Two substructures, which are the propeller-shaft subsystem and the submarine hull, are first modelled using the finite element method. The two substructures are then connected through bearings, which are simplified as longitudinal and lateral springs and dampers. The modes, the natural frequencies and the coupled vibration characteristics of the two substructures and their synthesized system are simulated. An experiment studying the dynamic characteristics of a large-scale submarine test-rig is proceeded and compared with the numerical results, showing great consistency. Finally, transfer path analysis of the low frequency excitation forces using power flow method is discussed.

scholarly journals Research on Vibration Reduction Design of Foundation with Entangled Metallic Wire Material under High Temperature

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Yue Zhu ◽  
Yiwan Wu ◽  
Hongbai Bai ◽  
Zheyu Ding ◽  
Yichuan Shao
Keyword(s):  
High Temperature ◽  
Insertion Loss ◽  
Power Flow ◽  
Vibration Reduction ◽  
Low Frequency ◽  
Composite Foundation ◽  
Metallic Wire ◽  
Transfer Path ◽  
Wire Material ◽  
Full Speed

When the submarine is sailing at full speed, the power cabin has an abnormally high temperature. However, in the previous research on the vibration reduction design of the foundation, the influence of high temperature on the vibration characteristics of the foundation is not taken into account. In this paper, a new composite foundation with entangled metallic wire material (EMWM) is presented to reduce the vibration of the foundation. The energy transfer path of the foundation was obtained by the power flow method, and then the layout of EMWM was determined. The optimization of the constraining layer was carried out by modal analysis. The damping performance of the composite foundation with EMWM was validated by the thermal-vibration joint test. The results show that, at room temperature, the composite foundation has remarkable vibration reduction efficiency in the middle and high-frequency bands. The maximum insertion loss can reach 15.37 dB. The insertion loss varies with the location of the excitation point. As the temperature rises to 300°C, the insertion loss in the low-frequency band was improved, and the insertion loss is not influenced by the excitation position.

scholarly journals Analysis of Approaches for Modeling the Low Frequency Emission of LED Lamps

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1571 ◽  
Author(s):  
Adam J. Collin ◽  
Sasa Z. Djokic ◽  
Jiri Drapela ◽  
Zekun Guo ◽  
Roberto Langella ◽  
...  
Keyword(s):  
Distribution System ◽  
Power Flow ◽  
Large Scale ◽  
Low Voltage ◽  
Light Emitting Diode ◽  
Flow Analysis ◽  
Low Frequency ◽  
Future Evolution ◽  
Voltage Quality ◽  
Design Characteristics

Light emitting diode (LED) lamps are now an established lighting technology, which is becoming prevalent in all load sectors. However, LED lamps are non-linear electrical loads, and their impact on distribution system voltage quality must be evaluated. This paper provides a detailed analysis of time domain and frequency domain approaches for developing and evaluating models suitable for use in large scale steady-state harmonic power flow analysis of the low frequency (LF) emission of LED lamps. The considered approaches are illustrated using four general categories of LED lamps, which have been shown to cover the vast majority of LED lamps currently available on the market. The aim is an in-depth assessment of the ability of commonly applied models to represent the specific design characteristics of different categories of LED lamps. The accuracy of the models is quantitatively evaluated by means of laboratory tests, numerical simulations, and statistical analyses. This provides an example, for each LED lamp category, of comprehensive information about the overall accuracy that can be achieved in the general framework of large scale LF harmonic penetration studies, particularly in the assessment of voltage quality in low voltage networks and their future evolution.

Vibration transmission path analysis of underwater vehicle power plant based on TPA power flow

2021 ◽  
pp. 147509022110240
Author(s):  
Yang Yang ◽  
Guang Pan ◽  
Shaoping Yin ◽  
Ying Yuan
Keyword(s):  
Power Plant ◽  
Path Analysis ◽  
Power Flow ◽  
Sea Water ◽  
Low Frequency ◽  
Underwater Vehicle ◽  
Vibration Energy ◽  
Vibration Transmission ◽  
Transmission Path ◽  
Transfer Path

In order to obtain the energy contribution of all paths transmitting vibration from the underwater vehicle power plant to the outer shell, a new method named TPA (Transfer Path Analysis) power flow which combines classical TPA and power flow theory was proposed. Calculation results showed that isolators were the critical paths for transmitting vibration energy to the shell in low frequency band. In addition the main engine and sea water pump were critical vibration sources, which provided directions for reducing the vibration energy transmitted from vibration sources to the target body. To the best of our knowledge, this was the first time to assess the vibration transmission path of the underwater vehicle by TPA power flow method. This method can be employed in other works that need to evaluate the contribution of vibration energy.

scholarly journals Experiment Investigation of Bistable Vibration Energy Harvesting with Random Wave Environment

2021 ◽  
Vol 11 (9) ◽  
pp. 3868
Author(s):  
Qiong Wu ◽  
Hairui Zhang ◽  
Jie Lian ◽  
Wei Zhao ◽  
Shijie Zhou ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Energy Harvesting ◽  
Cantilever Beam ◽  
Large Scale ◽  
Low Frequency ◽  
Vibration Energy ◽  
Random Wave ◽  
Periodic Signal ◽  
Vibration Energy Harvesting ◽  
Motion Activity

The energy harvested from the renewable energy has been attracting a great potential as a source of electricity for many years; however, several challenges still exist limiting output performance, such as the package and low frequency of the wave. Here, this paper proposed a bistable vibration system for harvesting low-frequency renewable energy, the bistable vibration model consisting of an inverted cantilever beam with a mass block at the tip in a random wave environment and also develop a vibration energy harvesting system with a piezoelectric element attached to the surface of a cantilever beam. The experiment was carried out by simulating the random wave environment using the experimental equipment. The experiment result showed a mass block’s response vibration was indeed changed from a single stable vibration to a bistable oscillation when a random wave signal and a periodic signal were co-excited. It was shown that stochastic resonance phenomena can be activated reliably using the proposed bistable motion system, and, correspondingly, large-scale bistable responses can be generated to realize effective amplitude enlargement after input signals are received. Furthermore, as an important design factor, the influence of periodic excitation signals on the large-scale bistable motion activity was carefully discussed, and a solid foundation was laid for further practical energy harvesting applications.

scholarly journals Comparing Different Approaches for Solving Large Scale Power-Flow Problems With the Newton-Raphson Method

IEEE Access ◽  
2021 ◽  
Vol 9 ◽  
pp. 56604-56615
Author(s):  
Manolo D'orto ◽  
Svante Sjoblom ◽  
Lung Sheng Chien ◽  
Lilit Axner ◽  
Jing Gong
Keyword(s):  
Power Flow ◽  
Large Scale ◽  
Flow Problems ◽  
Newton Raphson ◽  
Raphson Method

scholarly journals A Full-Newton AC-DC Power Flow Methodology for HVDC Multi-Terminal Systems and Generic DC Network Representation

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1658
Author(s):  
Leandro Almeida Vasconcelos ◽  
João Alberto Passos Filho ◽  
André Luis Marques Marcato ◽  
Giovani Santiago Junqueira
Keyword(s):  
Power Systems ◽  
Direct Current ◽  
Power Flow ◽  
Large Scale ◽  
Flow Problem ◽  
Control Strategies ◽  
Problem Formulation ◽  
Expansion Planning ◽  
Dc Power ◽  
Power Flow Problem

The use of Direct Current (DC) transmission links in power systems is increasing continuously. Thus, it is important to develop new techniques to model the inclusion of these devices in network analysis, in order to allow studies of the operation and expansion planning of large-scale electric power systems. In this context, the main objective of this paper is to present a new methodology for a simultaneous AC-DC power flow for a multi-terminal High Voltage Direct Current (HVDC) system with a generic representation of the DC network. The proposed methodology is based on a full Newton formulation for solving the AC-DC power flow problem. Equations representing the converters and steady-state control strategies are included in a power flow problem formulation, resulting in an expanded Jacobian matrix of the Newton method. Some results are presented based on HVDC test systems to confirm the effectiveness of the proposed approach.

scholarly journals A Novel Methodology for Adaptive Coordination of Multiple Controllers in Electrical Grids

Mathematics ◽  
2021 ◽  
Vol 9 (13) ◽  
pp. 1474
Author(s):  
Ruben Tapia-Olvera ◽  
Francisco Beltran-Carbajal ◽  
Antonio Valderrabano-Gonzalez ◽  
Omar Aguilar-Mejia
Keyword(s):  
Power Systems ◽  
Power System ◽  
Electric Power ◽  
Large Scale ◽  
Short Circuit ◽  
Dynamic Performance ◽  
Low Frequency ◽  
Electric Power System ◽  
Design Stage ◽  
Positive Interaction

This proposal is aimed to overcome the problem that arises when diverse regulation devices and controlling strategies are involved in electric power systems regulation design. When new devices are included in electric power system after the topology and regulation goals were defined, a new design stage is generally needed to obtain the desired outputs. Moreover, if the initial design is based on a linearized model around an equilibrium point, the new conditions might degrade the whole performance of the system. Our proposal demonstrates that the power system performance can be guaranteed with one design stage when an adequate adaptive scheme is updating some critic controllers’ gains. For large-scale power systems, this feature is illustrated with the use of time domain simulations, showing the dynamic behavior of the significant variables. The transient response is enhanced in terms of maximum overshoot and settling time. This is demonstrated using the deviation between the behavior of some important variables with StatCom, but without or with PSS. A B-Spline neural networks algorithm is used to define the best controllers’ gains to efficiently attenuate low frequency oscillations when a short circuit event is presented. This strategy avoids the parameters and power system model dependency; only a dataset of typical variable measurements is required to achieve the expected behavior. The inclusion of PSS and StatCom with positive interaction, enhances the dynamic performance of the system while illustrating the ability of the strategy in adding different controllers in only one design stage.

scholarly journals Optimizing the Frequency Capping: A Robust and Reliable Methodology to Define the Number of Ads to Maximize ROAS

2021 ◽  
Vol 11 (15) ◽  
pp. 6688
Author(s):  
Jesús Romero Leguina ◽  
Ángel Cuevas Rumin ◽  
Rubén Cuevas Rumin
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Low Frequency ◽  
Digital Marketing ◽  
Optimal Frequency ◽  
Novel Technique ◽  
Maximum Threshold

The goal of digital marketing is to connect advertisers with users that are interested in their products. This means serving ads to users, and it could lead to a user receiving hundreds of impressions of the same ad. Consequently, advertisers can define a maximum threshold to the number of impressions a user can receive, referred to as Frequency Cap. However, low frequency caps mean many users are not engaging with the advertiser. By contrast, with high frequency caps, users may receive many ads leading to annoyance and wasting budget. We build a robust and reliable methodology to define the number of ads that should be delivered to different users to maximize the ROAS and reduce the possibility that users get annoyed with the ads’ brand. The methodology uses a novel technique to find the optimal frequency capping based on the number of non-clicked impressions rather than the traditional number of received impressions. This methodology is validated using simulations and large-scale datasets obtained from real ad campaigns data. To sum up, our work proves that it is feasible to address the frequency capping optimization as a business problem, and we provide a framework that can be used to configure efficient frequency capping values.

scholarly journals Predicting AC Optimal Power Flows: Combining Deep Learning and Lagrangian Dual Methods

2020 ◽  
Vol 34 (01) ◽  
pp. 630-637 ◽  
Author(s):  
Ferdinando Fioretto ◽  
Terrence W.K. Mak ◽  
Pascal Van Hentenryck
Keyword(s):  
Deep Learning ◽  
Power Systems ◽  
Power Flow ◽  
Optimal Power Flow ◽  
Large Scale ◽  
Renewable Energy Sources ◽  
Electrical Power ◽  
Practical Applications ◽  
Fundamental Building Block ◽  
Optimal Power

The Optimal Power Flow (OPF) problem is a fundamental building block for the optimization of electrical power systems. It is nonlinear and nonconvex and computes the generator setpoints for power and voltage, given a set of load demands. It is often solved repeatedly under various conditions, either in real-time or in large-scale studies. This need is further exacerbated by the increasing stochasticity of power systems due to renewable energy sources in front and behind the meter. To address these challenges, this paper presents a deep learning approach to the OPF. The learning model exploits the information available in the similar states of the system (which is commonly available in practical applications), as well as a dual Lagrangian method to satisfy the physical and engineering constraints present in the OPF. The proposed model is evaluated on a large collection of realistic medium-sized power systems. The experimental results show that its predictions are highly accurate with average errors as low as 0.2%. Additionally, the proposed approach is shown to improve the accuracy of the widely adopted linear DC approximation by at least two orders of magnitude.

Separatrix crossing and large scale diffusion in low-frequency three-wave systems

1998 ◽  
Vol 58 (3) ◽  
pp. 3768-3776 ◽  
Author(s):  
B. Weyssow ◽  
J. D. Reuss ◽  
J. Misguich
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Separatrix Crossing
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