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Ichikawa, Yoshimichi; Nishioka, Michio; Takami, Hideo; Kimura, Sigeo
2001 Wind Engineering
The aim of the present study is to contribute to the operation and control of wind turbines situated in mountainous areas, which often suffer from over-speed due to highly gusty mountainous winds with high shear. By adding an electric load-brake to conventional pitch control we can suppress over-speed and increase power production.
2001 Wind Engineering
Blade-tip-speed ratio feedback control is applied to a wind turbine driven, grid connected, three phase, induction generator whose wound rotor winding is connected to a rectifier via slip rings. Power from the rotor winding flows through the rectifier to a switch-mode, step-up, DC to DC converter to re-charge a bank of batteries. The switch in the DC to DC converter has a variable duty cycle, and this design feature is used in a feedback control loop. A dynamic model of the complete system is presented along with simulation results.
Fupeng, Huo; Yuhong, Li; Zuoyi, Chen
2001 Wind Engineering
Suggestions for improving the efficiency and life expectancy of wind turbine blades are proposed in this paper. A new airfoil shape with wide leading edge nose and large camber has been investigated by numerical simulation with a range of attack angles. The results show that the lift-drag ratio of the airfoil is greater than that of the conventional airfoil at large attack angles (α>20°). Changing the local roughness on blade surfaces to improve the wind turbine performance is discussed in the paper. A new mechanism and method of analysing life expectancy of a blade with flow induced vibration in oscillating flow has been given. It is proved that the damping of blade material and structure has great influence on the endurance lifetime of blades. The investigation indicates further that the equilibrium amplitude of vibration greatly influences the lifetime of blades. Changing the damping characteristic of a blade may significantly vary its equilibrium amplitude, so extending the life expectancy of blades. This paper provides the foundations for further study.
2001 Wind Engineering
This paper analyses wind speed data for five typical sites in Hong Kong in terms of site terrain, wind conditions and wind power potential. For onshore and offshore wind power resources, the annual, monthly and diurnal wind speeds are assessed, and the annual mean power densities for the five sites are also calculated. These may be used for optimum sitting of wind sites in Hong Kong, which is also discussed for practical application. The characteristics and power output of a chosen wind turbine on one island are modelled and analysed as a case study to assess the wind power potential. The capacity factor of the modelled wind turbine reaches nearly 0.36, which is considered significant for wind power application. The example demonstrates that the sites on islands with good exposure are attractive for generating wind power, and that therefore offshore should be considered.
2001 Wind Engineering
As the wind speed increases from zero, small turbines will cut-in only when the aerodynamic torque acting on the blades exceeds the resistive torque of the generator and drive system. This Note describes the use of standard blade element theory to calculate the cut-in wind speed, at which rotation commences, using the apparent near-universality of aerofoil lift and drag at high incidence. The starting torque is shown to depend on the “chord-pitch” integral that, in turn, is a function only of the blade geometry. This integral is evaluated for two small blades designed by the author for which the cut-in wind speed has been determined. In both cases, the calculations considerably over-estimate the actual cut-in speed and some possible reasons for this are advanced.
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