scholarly journals Real-time harmonic identification under varying grid conditions

2021 ◽  
Vol 18 (1) ◽  
pp. 29-48
Author(s):  
Evgeniia Bulycheva ◽  
Sergey Yanchenko
Keyword(s):  
Pulse Sequence ◽  
Voltage Distortion ◽  
Grid Simulation ◽  
Time Harmonic ◽  
Non Linear ◽  
Novel Method ◽  
Sequence Generator ◽  
Grid Voltage Distortion ◽  
Measurement Approach ◽  
Invasive Measurement

One of the challenges of the power quality management is a need for reliable harmonic identification in grids with multiple non-linear loads. This paper proposes a novel method to accurately determine time-varying harmonic contributions of non-linear loads to the total grid voltage distortion. The use of the invasive measurement approach and ternary pulse sequence as a stimuli guarantees an accurate assessment of harmonic contribution with the account for timevariating harmonic impacts. The application of proposed approach is demonstrated by means of time-domain grid simulation with implemented white-box model of a pulse sequence generator. Statistical estimation of the accuracy of the proposed approach as well as comparison with typical harmonic identification methods justify its effectiveness under non-stationary network conditions.

Novel method for bearing performance degradation assessment – A kernel locality preserving projection-based approach

2013 ◽  
Vol 228 (3) ◽  
pp. 548-560 ◽  
Author(s):  
Chuang Sun ◽  
Zhousuo Zhang ◽  
Zhengjia He ◽  
Zhongjie Shen ◽  
Binqiang Chen ◽  
...  
Keyword(s):  
Test Data ◽  
Performance Degradation ◽  
Inner Product ◽  
Data Sets ◽  
Degradation Index ◽  
Locality Preserving Projection ◽  
Locality Preserving ◽  
Non Linear ◽  
Linear Information ◽  
Novel Method

Bearing performance degradation assessment is meaningful for keeping mechanical reliability and safety. For this purpose, a novel method based on kernel locality preserving projection is proposed in this article. Kernel locality preserving projection extends the traditional locality preserving projection into the non-linear form by using a kernel function and it is more appropriate to explore the non-linear information hidden in the data sets. Considering this point, the kernel locality preserving projection is used to generate a non-linear subspace from the normal bearing data. The test data are then projected onto the subspace to obtain an index for assessing bearing degradation degrees. The degradation index that is expressed in the form of inner product indicates similarity of the normal data and the test data. Validations by using monitoring data from two experiments show the effectiveness of the proposed method.

GPR-based novel approach for non-linear aerodynamic modelling from flight data

2018 ◽  
Vol 123 (1259) ◽  
pp. 79-92
Author(s):  
A. Kumar ◽  
A. K. Ghosh
Keyword(s):  
Aerodynamic Force ◽  
Equations Of Motion ◽  
Gaussian Process Regression ◽  
Likelihood Estimation ◽  
Flight Data ◽  
Novel Approach ◽  
Non Linear ◽  
Research Aircraft ◽  
Novel Method ◽  
Aerodynamic Modelling

ABSTRACTIn this paper, a Gaussian process regression (GPR)-based novel method is proposed for non-linear aerodynamic modelling of the aircraft using flight data. This data-driven regression approach uses the kernel-based probabilistic model to predict the non-linearity. The efficacy of this method is examined and validated by estimating force and moment coefficients using research aircraft flight data. Estimated coefficients of aerodynamic force and moment using GPR method are compared with the estimated coefficients using maximum-likelihood estimation (MLE) method. Estimated coefficients from the GPR method are statistically analysed and found to be at par with estimated coefficients from MLE, which is popularly used as a conventional method. GPR approach does not require to solve the complex equations of motion. GPR further can be directed for the generalised applications in the area of aeroelasticity, load estimation, and optimisation.

scholarly journals Experimental assessment of harmonic contributions using a ternary pulse sequence

2021 ◽  
Vol 18 (3) ◽  
pp. 271-289
Author(s):  
Evgeniia Bulycheva ◽  
Sergey Yanchenko
Keyword(s):  
Real Time ◽  
Pulse Sequence ◽  
Wide Band ◽  
Voltage Source ◽  
Time Interval ◽  
Time Frequency ◽  
Grid Impedance ◽  
Set Up ◽  
Grid Voltage Distortion ◽  
Operational Modes

Harmonic contributions of utility and customer may feature significant variations due to network switchings and changing operational modes. In order to correctly define the impacts on the grid voltage distortion the frequency dependent impedance characteristic of the studied network should be accurately measured in the real-time mode. This condition can be fulfilled by designing a stimuli generator measuring the grid impedance as a response to injected interference and producing time-frequency plots of harmonic contributions during considered time interval. In this paper a prototype of a stimuli generator based on programmable voltage source inverter is developed and tested. The use of ternary pulse sequence allows fast wide-band impedance measurements that meet the requirements of real-time assessment of harmonic contributions. The accuracy of respective analysis involving impedance determination and calculation of harmonic contributions is validated experimentally using reference characteristics of laboratory test set-up with varying grid impedance.

scholarly journals A Novel Approach to Model a Gas Network

2019 ◽  
Vol 9 (6) ◽  
pp. 1047 ◽  
Author(s):  
Ali Ekhtiari ◽  
Ioannis Dassios ◽  
Muyang Liu ◽  
Eoin Syron
Keyword(s):  
Linear System ◽  
End Users ◽  
Load Flow ◽  
Electrical Network ◽  
Flow Equations ◽  
Gas Network ◽  
Wide Range ◽  
Non Linear ◽  
Novel Method ◽  
Non Linear System

The continuous uninterrupted supply of Natural Gas (NG) is crucial to today’s economy, with issues in key infrastructure, e.g., Baumgarten hub in Austria in 2017, highlighting the importance of the NG infrastructure for the supply of primary energy. The balancing of gas supply from a wide range of sources with various end users can be challenging due to the unique and different behaviours of the end users, which in some cases span across a continent. Further complicating the management of the NG network is its role in supporting the electrical network. The fast response times of NG power plants and the potential to store energy in the network play a key role in adding flexibility across other energy systems. Traditionally, modelling the NG network relies on nonlinear pipe flow equations that incorporate the demand (load), flow rate, and physical network parameters including topography and NG properties. It is crucial that the simulations produce accurate results quickly. This paper seeks to provide a novel method to solve gas flow equations through a network under steady-state conditions. Firstly, the model is reformulated into non-linear matrix equations, then the equations separated into their linear and nonlinear components, and thirdly, the non-linear system is solved approximately by providing a linear system with similar solutions to the non-linear one. The non-linear equations of the NG transport system include the main variables and characteristics of a gas network, focusing on pressure drop in the gas network. Two simplified models, both of the Irish gas network (1. A gas network with 13 nodes, 2. A gas network with 109 nodes) are used as a case study for comparison of the solutions. Results are generated by using the novel method, and they are compared to the outputs of two numerical methods, the Newton–Raphson solution using MATLAB and SAINT, a commercial software that is used for the simulation of the gas network and electrical grids.

scholarly journals Sequential Diffusion Spectra as a Tool for Studying Time-Dependent Translational Molecular Dynamics: A Cement Hydration Study

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 68
Author(s):  
Igor Serša
Keyword(s):  
Molecular Dynamics ◽  
Porous Structure ◽  
Time Scales ◽  
Cement Hydration ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Model Parameters ◽  
Signal Attenuation ◽  
Wide Range ◽  
Novel Method

The translational molecular dynamics in porous materials are affected by the presence of the porous structure that presents an obstacle for diffusing molecules in longer time scales, but not as much in shorter time scales. The characteristic time scales have equivalent frequency ranges of molecular dynamics, where longer time scales correspond to lower frequencies while the shorter time scales correspond to higher frequencies of molecular dynamics. In this study, a novel method for direct measurement of diffusion at a given frequency of translational molecular dynamics is exploited to measure the diffusion spectra, i.e., distribution of diffusion in a wide range of frequencies. This method utilizes NMR modulated gradient spin-echo (MGSE) pulse sequence to measure the signal attenuation during the train of spin-echoes formed in the presence of a constant gradient. From attenuation, the diffusion coefficient at the frequency equal to the inverse double inter-echo time is calculated. The method was employed to study the white cement hydration process by the sequential acquisition of the diffusion spectra. The measured spectra were also analyzed by the diffusion spectra model to obtain the time-dependence of the best-fit model parameters. The presented method can also be applied to study other similar systems with the time evolution of porous structure.

scholarly journals A chaotic pulse sequence generator based on the tent map

2015 ◽  
Vol 12 (16) ◽  
pp. 20150530-20150530 ◽  
Author(s):  
Tong-Feng Zhang ◽  
Shou-Liang Li ◽  
Rong-Jun Ge ◽  
Min Yuan ◽  
Guan Gui ◽  
...  
Keyword(s):  
Pulse Sequence ◽  
Tent Map ◽  
Sequence Generator

Non-Invasive Measurement of In-Vivo Elasticity of Skeletal Muscles with MR-Elastography

2007 ◽  
Vol 342-343 ◽  
pp. 901-904
Author(s):  
Yu Bong Kang ◽  
T. Oida ◽  
Duk Young Jung ◽  
A. Fukuma ◽  
T. Azuma ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Skeletal Muscles ◽  
Soft Tissues ◽  
Viscosity Coefficient ◽  
Non Invasive ◽  
Novel Method ◽  
Human Calf ◽  
Invasive Measurement

In order to evaluate the mechanical properties of the human skeletal muscles, the elasticity and viscosity of the human calf muscles were measured with Magnetic Resonance Elastography (MRE). MRE is a novel method to measure the mechanical properties of living soft tissues in vivo quantitatively by observing the strain waves propagated in the object. In this study, the shear modulus and viscosity coefficient were measured with MRE. The shear modulus was 3.7 kPa in relaxed state, and increased with increasing the muscle forces. Interestingly, the viscosity was changed with the vibration frequency applied to the muscles, that was 4.5 Pa·s at 100Hz vibration and 2.4 Pa·s at 200Hz vibration. This shows clearly the visco-elastic property.

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