The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform
Dongmei Chen - One of the best experts on this subject based on the ideXlab platform.
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Optimal Control of a Wind Turbine With a Variable Ratio Gearbox for Maximum Energy Capture and Prolonged Gear Life
Journal of Solar Energy Engineering, 2014Co-Authors: Mohamed L. Shaltout, John F. Hall, Dongmei ChenAbstract:An optimal control approach for a wind turbine drivetrain with a Variable Ratio gearbox is presented. The objective is to find the optimum shifting sequence of the Variable Ratio gearbox in order to maximize power geneRation and extend gear life. The employment of a Variable Ratio gearbox enhances the capabilities of the wind turbine to cope with wind speed variations. Based on the authors' preliminary study, the gear Ratios of the Variable Ratio gearbox were carefully selected to maximize the wind energy capture. In this paper, a new control approach is proposed to achieve both extended gear service life and optimal energy harvesting. This new approach finds the gear shifting sequence that will minimize the tangential force on the gear tooth while maximizing the wind energy capture. The wind turbine drivetrain with a Variable Ratio gearbox is modeled and simulation results based on recorded wind data of different wind classes are presented and compared.
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Performance of a 100 kW wind turbine with a Variable Ratio Gearbox
Renewable Energy, 2012Co-Authors: John F. Hall, Dongmei ChenAbstract:A Variable Ratio Gearbox (VRG) can be used in the drivetrain of a small to medium-size wind turbine to improve aerodynamic efficiency. Currently, all commercially-available wind turbines operate using a fixed-gear Ratio between the turbine rotor and electrical generator. A VRG allows wind turbines, with a constant-speed generator, to discretely vary rotor speed and to achieve greater aerodynamic efficiency. The authors’ previous results demonstrate the viability of the VRG design. This research quantifies the gain in efficiency for a VRG-enabled wind turbine based on wind data from representing all seven wind classifications. A method is also presented to identify turbine sites that provide the VRG with the greatest opportunities to increase production. The overall findings suggest that the VRG can benefit all wind turbines, irrespective of wind class, with some wind profiles in the study experiencing gains greater than 10%.
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Wind energy conversion with a Variable-Ratio gearbox: design and analysis
Renewable Energy, 2011Co-Authors: John F. Hall, Dongmei Chen, Christine A. Mecklenborg, Siddharth B. PratapAbstract:Variable-speed wind turbines are able to adapt to low wind speeds and therefore have greater efficiency than fixed-speed turbines during partial-load opeRation. Unfortunately, the high cost and low reliability of the electronics that enable variation in speed have discouraged this mode of opeRation for distributed wind turbines. Alternatively, a Variable-Ratio Gearbox (VRG) can be integrated into the fixed-speed wind turbine to facilitate opeRation with a discrete set of Variable speeds that boost efficiency. The VRG concept is based upon mature technology taken from the automotive industry and is characterized by low cost and high reliability. In this paper, a model-based design methodology is introduced to study the performance gain of integrating a VRG into a fixed-speed stall-regulated wind turbine system. The results demonstrate how this device can improve the efficiency of the fixed-speed turbine in the partial-load region and the potential to use the VRG to limit power in the full-load region where pitch control is often used.
John F. Hall - One of the best experts on this subject based on the ideXlab platform.
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Optimal Control of a Wind Turbine With a Variable Ratio Gearbox for Maximum Energy Capture and Prolonged Gear Life
Journal of Solar Energy Engineering, 2014Co-Authors: Mohamed L. Shaltout, John F. Hall, Dongmei ChenAbstract:An optimal control approach for a wind turbine drivetrain with a Variable Ratio gearbox is presented. The objective is to find the optimum shifting sequence of the Variable Ratio gearbox in order to maximize power geneRation and extend gear life. The employment of a Variable Ratio gearbox enhances the capabilities of the wind turbine to cope with wind speed variations. Based on the authors' preliminary study, the gear Ratios of the Variable Ratio gearbox were carefully selected to maximize the wind energy capture. In this paper, a new control approach is proposed to achieve both extended gear service life and optimal energy harvesting. This new approach finds the gear shifting sequence that will minimize the tangential force on the gear tooth while maximizing the wind energy capture. The wind turbine drivetrain with a Variable Ratio gearbox is modeled and simulation results based on recorded wind data of different wind classes are presented and compared.
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Performance of a 100 kW wind turbine with a Variable Ratio Gearbox
Renewable Energy, 2012Co-Authors: John F. Hall, Dongmei ChenAbstract:A Variable Ratio Gearbox (VRG) can be used in the drivetrain of a small to medium-size wind turbine to improve aerodynamic efficiency. Currently, all commercially-available wind turbines operate using a fixed-gear Ratio between the turbine rotor and electrical generator. A VRG allows wind turbines, with a constant-speed generator, to discretely vary rotor speed and to achieve greater aerodynamic efficiency. The authors’ previous results demonstrate the viability of the VRG design. This research quantifies the gain in efficiency for a VRG-enabled wind turbine based on wind data from representing all seven wind classifications. A method is also presented to identify turbine sites that provide the VRG with the greatest opportunities to increase production. The overall findings suggest that the VRG can benefit all wind turbines, irrespective of wind class, with some wind profiles in the study experiencing gains greater than 10%.
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Wind energy conversion with a Variable-Ratio gearbox: design and analysis
Renewable Energy, 2011Co-Authors: John F. Hall, Dongmei Chen, Christine A. Mecklenborg, Siddharth B. PratapAbstract:Variable-speed wind turbines are able to adapt to low wind speeds and therefore have greater efficiency than fixed-speed turbines during partial-load opeRation. Unfortunately, the high cost and low reliability of the electronics that enable variation in speed have discouraged this mode of opeRation for distributed wind turbines. Alternatively, a Variable-Ratio Gearbox (VRG) can be integrated into the fixed-speed wind turbine to facilitate opeRation with a discrete set of Variable speeds that boost efficiency. The VRG concept is based upon mature technology taken from the automotive industry and is characterized by low cost and high reliability. In this paper, a model-based design methodology is introduced to study the performance gain of integrating a VRG into a fixed-speed stall-regulated wind turbine system. The results demonstrate how this device can improve the efficiency of the fixed-speed turbine in the partial-load region and the potential to use the VRG to limit power in the full-load region where pitch control is often used.
R I Macdonald - One of the best experts on this subject based on the ideXlab platform.
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theory of Variable Ratio power splitters using multimode interference couplers
IEEE Photonics Technology Letters, 1999Co-Authors: Neil Lagali, M R Paiam, R I MacdonaldAbstract:In this letter, we analyze the integrated optical N/spl times/N generalized Mach-Zehnder interferometer (GMZI) employing multimode interference (MMI) couplers. A transfer matrix is used to derive analytic expressions for the intensity distribution at the output ports of the GMZI as a function of the phase shifts applied to the arms. These expressions form a system of nonlinear equations which are numerically solved for the phase shifts, enabling a new interpretation of the GMZI as a Variable-Ratio power splitter. The performance of the GMZI has been simulated, and it is found that the power splitting Ratio is tolerant to both the accuracy of the applied phase shifts and to fluctuations in wavelength.
Bernard Kippelen - One of the best experts on this subject based on the ideXlab platform.
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Variable Ratio power splitters using computer generated planar holograms on multimode interference couplers
Optics Letters, 2009Co-Authors: Shuo Yen Tseng, Seungkeun Choi, Bernard KippelenAbstract:Variable-Ratio power splitters using computer-generated planar holograms on multimode interference couplers are analyzed. The coherent wave at the device input is transformed to the desired output using numerically calculated refractive index perturbations on multimode channel waveguides at half the beat length. Devices are fabricated on the silicon-on-insulator platform and characterized at a wavelength of 1.55 μm. Power-splitting Ratios are varied by changing the hologram etch depth and the hologram length.
Neil Lagali - One of the best experts on this subject based on the ideXlab platform.
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theory of Variable Ratio power splitters using multimode interference couplers
IEEE Photonics Technology Letters, 1999Co-Authors: Neil Lagali, M R Paiam, R I MacdonaldAbstract:In this letter, we analyze the integrated optical N/spl times/N generalized Mach-Zehnder interferometer (GMZI) employing multimode interference (MMI) couplers. A transfer matrix is used to derive analytic expressions for the intensity distribution at the output ports of the GMZI as a function of the phase shifts applied to the arms. These expressions form a system of nonlinear equations which are numerically solved for the phase shifts, enabling a new interpretation of the GMZI as a Variable-Ratio power splitter. The performance of the GMZI has been simulated, and it is found that the power splitting Ratio is tolerant to both the accuracy of the applied phase shifts and to fluctuations in wavelength.
