341 research outputs found
Effects of inertia on dynamic performance of wind turbines
No full textThe dynamic performance of wind turbines indicates that the power extracted from the wind is strongly related to the inertia of the system and characteristics of wind speed. In this paper, a simulation model of a wind turbine system has been developed to study the effects of inertia. Three aspects of the dynamic performance of wind turbines are investigated in the paper: the prediction of the trend of the natural time-constant versus power rating for wind turbines, the effects of shaft speed on the actual time constant and the power loss due to inertia under varying wind speed conditions.C. Tang, M. Pathmanathan, W.L. Soong and N. Ertugrulhttp://www.ee.unsw.edu.au/aupec2008
Investigation of phase advance modulation with surface permanent magnet generators
No full textPhase advance modulation of a semi-bridge switchedmode rectifier (SMR) has been shown to produce greater power than conventional SMR modulation, at a lower cost than an inverter. This paper investigates how these power improvements are affected by two generator parameters: stator inductance and resistance. These parameters were investigated by a simplified simulation model, which used the boost converter approximation of a semi-bridge SMR. The ratio of generator stator resistance to reactance was found to have a significant impact on the maximum amount of power which could be obtained by phase advance modulation, and the optimum modulation parameters required.M. Pathmanathan, W.L. Soong and N. Ertugru
Cetuximab associated dermal filler reaction
No full textA 52-year-old male patient with hyaluronic acid-based dermal fillers injected in his cheeks was diagnosed with glossotonsillary malignancy, and managed with concurrent cetuximab (epidermal growth factor receptor inhibitor) and radiation therapy. He developed significant inflammation around the dermal filler sites after first cycle of cetuximab which improved with dissolution of the dermal fillers with hyaluronidase. This suggests that cetuximab can lead to inflammation around the dermal filler sites, which can be treated with dissolution of the filler.No Full Tex
Output power capability of surface PM generators with switched-mode rectifiers
No full textSurface permanent magnet (SPM) machines operate with maximum output power for a given current when the induced voltage and the current are in phase. For an SPM generator this is obtained with a leading power-factor load. The inverter topology can achieve a leading input power-factor but this generally requires rotor position information. A lower-cost approach is to use a switched-mode rectifier (SMR) however with conventional modulation control its unity power factor operation results in a lower output power capability, particularly at low speeds. This paper examines performance of phase advance modulation methods to improve the lowspeed output power capability of SPM generators when operated with a SMR. A simplified phase advance modulation called zero-epsilon is proposed. Analytical and simulation approaches are used to understand the fundamental limitations, and the results are then confirmed experimentally.M. Pathmanathan, W.L. Soong and N. Ertugru
Comparison of AC/DC converters and the principles of a new control strategy in small-scale wind turbine systems
No full textThis paper provides a detailed comparison of AC/DC converters commonly used in small-scale wind turbine systems. The paper reviews the main AC/DC converter topologies first including rectifier, switch-mode rectifier and inverter, and provides their operational features and characteristics. Then based on the previous analytical and comparison studies, it describes a novel multi-mode control strategy, which aims to improve the performance of small-scale wind turbines over a wide operating speed range while considering trade-off between performance and control complexity in such converters.Lujie Chen, Wen. L. Soong, Mehanathan Pathmanathan and Nesimi Ertugrulhttp://aupec2012.org
Maximum-torque-per-ampere control of phase advance modulation of an SPM wind generator
No full textSurface permanent-magnet (SPM) machines are normally operated by controlling the d- and q-axis currents. This paper examines the control of SPM generators based on controlling the terminal voltage magnitude V and power-factor angle 8. This is well suited for generator operation when using a switched-mode rectifier and avoids the need for a rotor position sensor. The parameters required for generating a given value of torque with minimum phase current in order to minimize copper losses are derived in this paper. This will be achieved by controlling V and 8 to keep the d-axis current equal to zero at low speed, before switching to field-weakening control at higher speeds. Simulated and experimental results will be used to verify the control strategy and the efficiency achieved.Mehanathan Pathmanathan, Wen L. Soong and Nesimi Ertugru
Maximum torque per ampere control of phase advance modulation of a SPM wind generator
No full textSurface permanent magnet (PM) machines are normally operated by controlling the d-axis and q-axis currents. This paper examines the control of surface PM generators based on controlling the terminal voltage magnitude V and power-factor angle θ. This is well-suited for generator operation when using a switched-mode rectifier and avoids the need for a rotor position sensor. The parameters required for generating a given value of torque with minimum phase current in order to minimize copper losses are derived in this paper. This will be achieved by controlling V and θ to keep the d-axis current equal to zero at low speed, before switching to field-weakening control at higher speeds. Simulated and experimental results will be used to verify the control strategy, and the efficiency achieved.Mehanathan Pathmanathan, Wen Soong and Nesimi Ertugru
V-theta control of inverters used in SPM wind turbine generators
No full textThis paper examines a position sensorless modulation strategy, called V-θ control, for six-switch fully-controlled rectifiers (inverters) for surface permanent magnet (SPM) generators in small-scale wind turbines. In this strategy, the SPM generator torque is commanded by controlling the magnitude of the phase voltage and its phase shift with respect to the current waveform. Simulated results obtained using simplified and PWM inclusive simulation models were used to validate the analytical findings presented. Experimental results are shown comparing the proposed V-θ control method with both phase advance and conventional switched-mode rectifier (SMR) modulated AC/DC converters. The V-θ control was found to produce up to 22% more power at a given speed compared to phase advance modulation.Mehanathan Pathmanathan, Wen L. Soong, Nesimi Ertugru
The impact of light on vase life in (Anthurium andraeanum Hort.) cut flowers
No full textThe impact of light quality and quantity on vase life was investigated using Anthurium (Anthurium andraeanum Hort.). Cultivars ‘Spirit’ and ‘Honduras’, were chosen based on their contrasting vase life in previous studies, and designated as ‘Vshort’ and ‘Vlong’ respectively. Both cultivars were kept under three light regimes at 12 h day length: fluorescent lights of 40 μmol m-2 s-1, low intensity LEDs producing light at 40 μmol m-2 s-1 and high intensity LEDs producing light at 400 μmol m-2 s-1. Degradation, water uptake and hyperspectral reflectance were measured three times a week as the cut flowers degraded. Spadix necrosis was used to quantify cut flower degradation over time and to determine the vase life for each cultivar. Light regime had a significant impact on vase life and water uptake in Vlong but not in Vshort, with high intensity LEDs resulting in a marked increase in the vase life of Vlong. The rate of water uptake was higher for Vshort, while Vlong maintained moderate and steady water uptake over time, particularly under high intensity LEDs. The reflectance spectrums changed during spathe degradation, with different responses seen in each cultivar. Reflectance spectrums showed consistent changes in the ‘red dip index’ (R800-R685), with Vshort demonstrating an increase in reflectance of red light over time while Vlong increased its absorption of red light over time. Extension of vase life under high intensity light was cultivar-dependent, revealing a previously unknown interaction between light and vase life. The absence of any interaction in the short vase life cultivar suggests that this mechanism is linked to genotypic differences in vase life, while the contrasting reflectance profiles suggest that pigment turnover is important for regulating this mechanism
Langerhans cell histiocytosis of the optic chiasm
No full textLangerhans cell histiocytosis (LCH) is a rare disease with clonal proliferation of dendritic histiocytes forming a pseudotumoral growth. LCH occurs most frequently in infancy or early childhood. It can present either as a localized self-limiting form or as a diffuse form with multisystem involvement. Herein an unusual case of LCH involving the optic chiasm is presented. To the authors' knowledge, this is the first reported case of LCH presenting with visual disturbance. The clinical, radiological and histopathological findings are discussed
- …
