121,997 research outputs found
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
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
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
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
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
Human papillomavirus immunisation of adolescent girls: improving coverage through multisectoral collaboration in Malaysia
No full textBuang SN, Ja’afar S, Pathmanathan I, Saint VA. Human papillomavirus immunisation of adolescent girls: improving coverage through multisectoral collaboration in Malaysia. BMJ. 2018;363: k4602.Saidatul Buang and colleagues report on collaborative efforts to introduce HPV vaccination in Malaysia and increase coverag
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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
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