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S.a. Al-saleh - One of the best experts on this subject based on the ideXlab platform.
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Testing the Performance of a Resolution-Level MPPT Controller for PMG-Based Wind Energy Conversion Systems
IEEE Transactions on Industry Applications, 2017Co-Authors: S.a. Al-salehAbstract:This paper presents the development and performance evaluation of a maximum power point tracking (MPPT) controller for direct-drive variable-speed permanent magnet generator (PMG)-based wind energy conversion systems (WECSs). The developed MPPT controller is designed to vary the Resolution-Level $J$ of the wavelet modulation technique used to operate the generator-side $3\phi$ ac–dc power electronic converter (PEC). The variations of $J$ are created by two angles, $\theta _{I}$ and $\theta _{O}$ . The angle $\theta _{I}$ is defined to map the changes on the input side, while the angle $\theta _{O}$ is defined to map the changes on the output side of a $3\phi$ wavelet-modulated ac–dc PEC. The Resolution-Level MPPT is implemented for performance evaluation on a 3.6 kW PMG-based WECS when operated in grid connection. Test results show good accuracy and dynamic responses, along with minor sensitivity to the variations in system parameters and Levels of power delivery to the grid.
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IAS Annual Meeting - Resolution-Level MPPT controller for PMG-based wind energy conversion systems
2016 IEEE Industry Applications Society Annual Meeting, 2016Co-Authors: S.a. Al-salehAbstract:This paper presents the development and performance evaluation of a maximum power point tracking (MPPT) controller for direct-drive, variable-speed, permanent magnet generator (PMG)-based wind energy conversion systems (WECSs). The developed MPPT controller is designed to vary the Resolution-Level, J, of the wavelet modulation technique used to operate the generator-side 3φ ac-dc power electronic converter (PEC). The variations of J are created by two angles, θ I and θ O . The angle θ I is defined to map the changes on the input side, while the angle θ O is defined to map the changes on the output side of a 3φ wavelet modulated (WM) ac-dc PEC. The Resolution-Level MPPT is implemented for performance evaluation on a 3.6 kW PMG-based WECS when operated in grid-connection. Test results show good accuracy and dynamic responses, along with minor sensitivity to the variations in system parameters and Levels of power delivery to the grid.
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Optimal Resolution Level for Input–Output Control of $3\phi$ VS WM AC–DC Converters
IEEE Transactions on Industry Applications, 2014Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:The switching pulses of the wavelet modulation technique are generated as sets of dilated and shifted scale-based linearly combined synthesis wavelet functions. The duration and location of each switching pulse are set by the scale (Resolution Level) at which its associated synthesis wavelet function is generated. In this paper, a novel controller is developed and tested for three phase (3φ) voltage source (VS) six-pulse wavelet-modulated ac-dc converters. The proposed controller is structured to adjust the maximum value reached by the scale. This maximum value, J, is adjusted based on two angles. The first angle, θI, maps changes in the 3φ supply voltages to adjustments in J, while the second angle, θO, maps changes in the dc output voltage to adjustments in J. The net adjustment in J is optimized based on the mapped changes by θI and θO. The optimal Resolution-Level controller is implemented in order to evaluate its performances for operating 3φ VS six-pulse ac-dc converters. The performances of the proposed controller are tested when the converter is supplied with balanced, unbalanced, and distorted 3φ voltages for feeding static and dynamic loads. Test results demonstrate fast and accurate responses, stable functioning, and good dynamics to ensure that the output dc voltage follows its command value for different supply and loading conditions.
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Resolution-Level-Controlled WM Inverter for PMG-Based Wind Energy Conversion System
IEEE Transactions on Industry Applications, 2012Co-Authors: S.a. Al-saleh, R. AhshanAbstract:This paper presents the development, implementation, and performance testing of a permanent-magnet generator (PMG)-based wind energy conversion system (WECS) for grid-connected applications. The grid-connected operation is constructed using the new three-phase Resolution-Level-controlled wavelet-modulated inverter. The output of the wind generator is fed to a switch-mode ac-dc converter, where the dc voltage is controlled to ensure extracting power from the wind under variable wind speed conditions in order to meet the grid active and reactive power demands. The Resolution-Level control of the grid-side inverter is designed as a current controller for adjusting active and reactive powers delivered to the grid. The proposed WECS is implemented both in software and hardware for performance testing on a direct-drive 6-kW laboratory PMG operated with variable speed. Test results demonstrate that an accurate control of the dc voltage on the generator side ensures adjusting the generator speed to extract power at each wind speed in order to meet the demand active and reactive power delivery to the grid. Also, test results show significant abilities of the Resolution-Level controller to initiate fast and accurate adjustments in the active and reactive powers delivered to the grid in order to follow any changes in their demand values under variable wind speed.
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IAS - Optimized Resolution-Level for input-output control of 3ϕ VS WM AC-DC converters
2012 IEEE Industry Applications Society Annual Meeting, 2012Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:The switching pulses generated by the wavelet modulation technique represent sets of scaled and translated synthesis scale-based linearly-combined wavelet basis functions. The duration and location of each switching pulse are determined by the scale. In this paper, a novel controller is developed and tested for three phase, voltage source, 6-pulse wavelet modulated ac-dc converters. The proposed controller is structured to determine the maximum value of the scale j based on two phase shift angles. The first phase shift angle θ I is defined to adjust the generated switching pulses in response to changes in the converter input three phase voltages. The second phase shift angle θ O is defined to adjust the generated switching pulses in order to ensure the output dc voltage follows its command value. The optimized Resolution-Level controller is implemented for simulation and experimental testing for input three phase voltages with unbalances, as well as step changes in the command output dc voltage. Test results demonstrate fast responses, accurate adjustments and good dynamics to ensure the output dc voltage follows its command value regardless of the state of the 3ϕ input voltages.
Chien-ming Chou - One of the best experts on this subject based on the ideXlab platform.
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Applying Wavelet Decomposition Hydrological Time Series and the Optimization of Model Groups in Flood Forecasting
2014Co-Authors: Chien-ming ChouAbstract:Applying Wavelet Decomposition Hydrological Time Series and the Optimization of Model Groups in Flood Forecasting This study applies a redundant wavelet transform (WT) and an optimization of model groups to accurately forecast the flood of a watershed. Effective rainfall and direct runoff can be decomposed into detailed signals and an approximation by using a redundant WT. The AutoRegressive model with exogenous Input (ARX), nonlinear ARX (NARX), time-varying ARX, and time-varying NARX models are implemented in parallel at each Resolution Level, and the optimal model is selected as the forecasting model. The summation of the forecasting results obtained at various Resolution Levels yields the overall flood forecasting by applying the inverse WT. The first-stage validation results indicate that the optimalforecasting model at each Resolution Level for six events is timevarying NARX. The second-stage validation results show that the proposed approach is appropriate for modeling the rainfall-runoff process at each Resolution Level and estimating the overall runoff for small watersheds in Taiwan. The analytic results also confirm that the proposed wavelet-based method outperforms the conventional method, which uses data only at the original Resolution Level, because of the multi-Resolution analysis (MRA) property of the wavelet transform.
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A Threshold Based Wavelet Denoising Method for Hydrological Data Modelling
Water Resources Management, 2011Co-Authors: Chien-ming ChouAbstract:This work developed a novel framework for considering wavelet denoising in linear perturbation models (LPMs) and simple linear models (SLMs). Rainfall and runoff time series data were decomposed using wavelet transforms to acquire approximate and detailed rainfall and runoff signals, respectively, at various Resolution Levels. At each Resolution Level, threshold quantifications were performed by setting the values of a detailed signal below a certain threshold to zero. The denoised rainfall and runoff time series data were obtained from the approximation at the final Resolution Level and processed detailed signals using threshold quantification at all Resolution Levels of rainfall and runoff, respectively, by wavelet reconstruction. The data were then applied to the SLM and regarded as the smooth seasonal mean employed in the LPM. The noise, i.e., original time series value minus denoised time series value, was employed as the perturbation term in the LPM. Moreover, a linear relationship between input and output noise was assumed. The denoised runoff and estimated noise of runoff were summed to estimate overall runoff in the LPM. To verify the accuracy of the proposed method, daily rainfall–runoff data were analyzed for an upstream area of the Kee-Lung River. The analytical results demonstrate that wavelet denoising enhances rainfall–runoff modelling precision for the LPM.
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Applying multi-Resolution analysis to differential hydrological grey models with dual series
Journal of Hydrology, 2006Co-Authors: Chien-ming ChouAbstract:Summary This investigation proposes a new approach for modeling rainfall–runoff processes by wavelet-based multi-Resolution analysis. Firstly, a redundant wavelet transform is used to decompose the observed effective rainfall and direct runoff time series to obtain wavelet coefficients at each Resolution Level. Then, these wavelet coefficients are applied to model rainfall–runoff processes using differential hydrological grey models with dual series at each Resolution Level. The average of the estimated grey parameters at each Resolution Level not only provides information for validating the proposed approach, but also represents the average system characteristics at each Resolution Level. The summation of the forecast results at various Resolution Levels yields the overall forecast and reveals that this procedure is suitable for modeling the rainfall–runoff process.
M.a. Rahman - One of the best experts on this subject based on the ideXlab platform.
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Optimal Resolution Level for Input–Output Control of $3\phi$ VS WM AC–DC Converters
IEEE Transactions on Industry Applications, 2014Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:The switching pulses of the wavelet modulation technique are generated as sets of dilated and shifted scale-based linearly combined synthesis wavelet functions. The duration and location of each switching pulse are set by the scale (Resolution Level) at which its associated synthesis wavelet function is generated. In this paper, a novel controller is developed and tested for three phase (3φ) voltage source (VS) six-pulse wavelet-modulated ac-dc converters. The proposed controller is structured to adjust the maximum value reached by the scale. This maximum value, J, is adjusted based on two angles. The first angle, θI, maps changes in the 3φ supply voltages to adjustments in J, while the second angle, θO, maps changes in the dc output voltage to adjustments in J. The net adjustment in J is optimized based on the mapped changes by θI and θO. The optimal Resolution-Level controller is implemented in order to evaluate its performances for operating 3φ VS six-pulse ac-dc converters. The performances of the proposed controller are tested when the converter is supplied with balanced, unbalanced, and distorted 3φ voltages for feeding static and dynamic loads. Test results demonstrate fast and accurate responses, stable functioning, and good dynamics to ensure that the output dc voltage follows its command value for different supply and loading conditions.
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IAS - Optimized Resolution-Level for input-output control of 3ϕ VS WM AC-DC converters
2012 IEEE Industry Applications Society Annual Meeting, 2012Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:The switching pulses generated by the wavelet modulation technique represent sets of scaled and translated synthesis scale-based linearly-combined wavelet basis functions. The duration and location of each switching pulse are determined by the scale. In this paper, a novel controller is developed and tested for three phase, voltage source, 6-pulse wavelet modulated ac-dc converters. The proposed controller is structured to determine the maximum value of the scale j based on two phase shift angles. The first phase shift angle θ I is defined to adjust the generated switching pulses in response to changes in the converter input three phase voltages. The second phase shift angle θ O is defined to adjust the generated switching pulses in order to ensure the output dc voltage follows its command value. The optimized Resolution-Level controller is implemented for simulation and experimental testing for input three phase voltages with unbalances, as well as step changes in the command output dc voltage. Test results demonstrate fast responses, accurate adjustments and good dynamics to ensure the output dc voltage follows its command value regardless of the state of the 3ϕ input voltages.
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Development and Experimental Validation of Resolution-Level Controlled Wavelet-Modulated Inverters for Three-Phase Induction Motor Drives
IEEE Transactions on Industry Applications, 2011Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:This paper presents the development, implementation, and performances of a Resolution-Level vector controller (RLVC) for three-phase induction motor (IM) drive systems. The RLVC is structured to adjust the output voltages of a three-phase voltage-source wavelet-modulated inverter which is used to supply a three-phase IM. The objectives of the RLVC are established by controlling the quadrature axis component of the stator currents while maintaining a constant direct axis component of the stator currents. The complete IM drive system incorporating the RLVC is successfully implemented in real time for performance testing using a three-phase squirrel-cage IM. The performances of the proposed IM drive system are tested for sudden changes in load torque and command speed. Simulated and experimental performances demonstrate reliable, stable, fast, and accurate responses of the proposed controller under various operating conditions.
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Development and Experimental Testing of a 3o Resolution-Level Controlled WM Inverter-Fed Induction Motor
2007 IEEE Industry Applications Annual Meeting, 2007Co-Authors: S.a. Al-saleh, M.a. RahmanAbstract:This paper presents a novel speed control approach for inverter-fed three-phase (3Phi) induction motors. The proposed approach is called the Resolution-Level controller (RLC) that is realized for the 3Phi voltage-source (VS) wavelet-modulated (WM) inverters. The wavelet modulation technique generates switching pulses using a non-dyadic type multiResolution analysis (MRA) that is constructed by three scale-based linearly-combined scaling functions shifted by 2pi/3 from each other. Moreover, The change in the scale of the three synthesis scaling functions is based on the change of the sign of the first derivative of the reference-modulating signals. The three scaling functions have dual synthesis scaling functions that are responsible for reconstructing the three continuous-time reference-modulating signals from their nonuniform recurrent samples. The reconstruction processes are carried out by the three synthesis scaling functions to achieve 180-degrees conduction mode of the 3Phi inverter. The proposed RLC approach is based on adjusting the zero-crossing locations of the first derivative of the reference-modulating signals to change scales of successive dilated and shifted versions of the three synthesis scaling functions. This change in scales can be incorporated to adjust the speed of the induction motor to meet load changes. The complete drive incorporating the RLC is successfully implemented in real-time using a digital signal processor board dSPACE ds1102 DSP board to generate switching pulses to activate the inverter six IGBT switches. The IGBT inverter supplies a 1 hp, 1750 RPM, 208 V, 60 Hz, Y-connected 3Phi squirrel-cage induction motor that is tested for several speed and load variations. The test results demonstrate robust performance, simple implementation, significant dynamic responses and high ability to maintain high quality outputs.
Atilla Baskurt - One of the best experts on this subject based on the ideXlab platform.
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Hierarchical watermarking of semiregular meshes based on wavelet transform
IEEE Transactions on Information Forensics and Security, 2008Co-Authors: Kai Wang, Guillaume Lavoué, Florence Denis, Atilla BaskurtAbstract:This paper presents a hierarchical watermarking framework for semiregular meshes. Three blind watermarks are inserted in a semiregular mesh with different purposes: a geometrically robust watermark for copyright protection, a high-capacity watermark for carrying a large amount of auxiliary information, and a fragile watermark for content authentication. The proposed framework is based on wavelet transform of the semiregular mesh. More precisely, the three watermarks are inserted in different appropriate Resolution Levels obtained by wavelet decomposition of the mesh: the robust watermark is inserted by modifying the norms of the wavelet coefficient vectors associated with the lowest Resolution Level; the fragile watermark is embedded in the high Resolution Level obtained just after one wavelet decomposition by modifying the orientations and norms of the wavelet coefficient vectors; the high-capacity watermark is inserted in one or several intermediate Levels by considering groups of wavelet coefficient vector norms as watermarking primitives. Experimental results demonstrate the effectiveness of the proposed framework: the robust watermark is able to resist all common geometric attacks even with a relatively strong amplitude; the fragile watermark is robust to content-preserving operations, while being sensitive to other attacks of which it can also provide the precise location; the payload of the high-capacity watermark increases rapidly along with the number of watermarking primitives.
János Pipek - One of the best experts on this subject based on the ideXlab platform.
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Optimization of the prediction of second refined wavelet coefficients in electron structure calculations
Open Physics, 2016Co-Authors: Brigita Sziová, Szilvia Nagy, János PipekAbstract:AbstractIn wavelet-based solution of eigenvalue-type differential equations, like the Schrödinger equation, refinement in the Resolution of the solution is a costly task, as the number of the potential coefficients in the wavelet expansion of the solution increases exponentially with the Resolution.Predicting the magnitude of the next Resolution Level coefficients from an already existing solution in an economic way helps to either refine the solution,or to select the coefficients, which are to be included into the next Resolution Level calculations, or to estimate the magnitude of the error of the solution. However, after accepting a solution with a predicted refinement as a basis, the error can still be estimated by a second prediction, i.e., from a prediction to the second finer Resolution Level coefficients. These secondary predicted coefficients are proven to be oscillating around the values of the wavelet expansion coefficients of the exact solution. The optimal averaging of these coefficients is presented in the following paper using a sliding average with three optimized coefficients for simple, one-dimensional electron structures.
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On an economic prediction of the finer Resolution Level wavelet coefficients in electron structure calculations
Physical chemistry chemical physics : PCCP, 2015Co-Authors: Szilvia Nagy, János PipekAbstract:In wavelet based electron structure calculations introducing a new, finer Resolution Level is usually an expensive task, this is why often a two-Level approximation is used with very fine starting Resolution Level. This process results in large matrices to calculate with and a large number of coefficients to be stored. In our previous work we have developed an adaptively refining solution scheme that determines the indices, where refined basis functions are to be included, and later a method for predicting the next, finer Resolution coefficients in a very economic way. In the present contribution we would like to determine, whether the method can be applied for predicting not only the first, but also the other, higher Resolution Level coefficients. Also the energy expectation values of the predicted wave functions are studied, as well as the scaling behaviour of the coefficients in the fine Resolution limit.
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Error estimation of wavelet based modeling of electromagnetic waves in waveguides and resonators
The 2nd Middle East Conference on Antennas and Propagation, 2012Co-Authors: Andras Feher, Sz Nagy, János PipekAbstract:Wavelets provide an effective toolbox for solving differential equations by representing the continuous functions by their wavelet expansion coefficients and the corresponding differential equations by discrete matrix equations. The wavelet basis functions are organized into Resolution Levels of different frequency terms at different locations, and the main advantage of the wavelet expansion representation is that the Resolution Level can be different at different locations, if the solution function contains higher frequency terms in one place and restricted to lower frequencies at other places. Wavelet based differential equation solving methods can be adaptive, it is possible to refine the solution locally, if the precision is not sufficient at some regions. In the present work a simple method for estimating the next Resolution Level wavelet coefficients is presented. Predicting the approximate value of these coefficients makes it possible to select the minimal set of wavelet basis functions for the next Resolution Level solution in a computationally economic way, or in the last Resolution Levels it can substitute the next Level solution of the matrix equation.
