Applied Mechanics and Materials Vols. 291-294

Abstract: A small multi-blade wind turbine is an alternative technology in order to electricity generating for use in a household because of the construction is cheap. From the study, the performance calculations by simulation program show that a number of blade at 12 blades is the optimum value for applying to this wind turbine that give maximum power coefficient of 0.29 at a tip speed ratio of 1.2. The results from the test run of wind rotor connected with generator in the wind tunnel at a wind velocity of 2 m/s, 3 m/s and 4 m/s, the system give the electric power of 2.5 W, 4.25 W and 4.49 W respectively.

Abstract: Renewable energy resources such as wind energy have a disadvantage that the quality of output power is lower than that of fossil fuel resources. To solve this problem, pumped storage power system with Archimedean screw is designed. The structure and principle of operation are introduced and the advantages and disadvantages are discussed according to the theory and the simulation. In this paper, comparison has been done by collecting and analyzing the data and simulated the system on different condition to show the differences of the two types of pumps working on the pumped storage system.

Abstract: Field experimental study is performed on a 33 kW horizontal axis wind turbine with rotor diameter of 14.8 m. The distribution of pressure is gathered by disposed 191 taped pressure sensors span-ward on seven particular sections of a blade. The results will provide a comparative basis to wind tunnel experiment and numerical calculation of the flow of the wind turbine.

Abstract: Three-dimensional flow around a horizontal-axis wind turbine has been investigated with LES method coupled with sliding mesh and experimental measurement. The boundary conditions are set as the same as those of the experiment. The images of the pressure distribution, flow rate distribution, turbulent intensity, velocity vector and vortices of the wind turbine are presented to show the three-dimensional flow characteristics around the wind turbine. The relationship between flow and sound is further studied by analyzing the flow parameters pulsation spectrum to get the sound pressure level. LES results are compared with the wind-tunnel measurements collected with PIV, and good agreement is observed. The results serve as a reference for optimum design of the wind turbine with high functional performance and low level noise generation.

Abstract: In this paper, the effects of the shape of three types of the blade on power coefficient of Savonius rotors are studied by simulating the model using numerical simulation under the same conditions. For this purpose, three spherical rotors with different configurations but identical number of stages and blades, aspect ratio and overlap keeping the identical projected area of each rotor are constructed. The geometries of blade of the three rotors are a plane, a semi-circle and a quarter of sphere. The building data are calculated on the basis of the nominal wind velocity V= 10m/s and the speed ratio λ= 0.3 with an industrial flow simulation code (ANSYS-Fluent). The result shows that the rotor with semicircular blades has a higher value of power coefficient in comparison with other rotors.

Abstract: Considering the randomness of wind speed and wind direction, the partial wake effect between wind turbines (WTs) in complex terrain was analyzed and a multiple wake model in complex terrain was established. Taking the power output characteristic of WT into consideration, a wind farm reliability model which considered the outages of connection cables was presented. The model is implemented in MATLAB using sequential Monte Carlo simulation and the results show that this model corrects the power output of wind farm, while improving the accuracy of wind farm reliability model.

Abstract: Aiming at operation problems of DFIG under grid fault condition, the improved control strategy of coordinating control rotor converter and Crowbar circuit switching logic for enhancing LVRT ability is proposed. The over-current cause on the stator and rotor of DFIG under grid fault is analyzed and complete improved control strategy flow chart is given during entire voltage dip. Experimental verification results show that adopting this improved control strategy can effectively suppress the generator stator and rotor over-current and over-voltage, enhance wind turbine operation ability, and provide important theoretical basis and reference for large-scale wind turbine to respond to grid transient fault.

Abstract: In order to accurately obtain the influence of rotational effect on fluctuating component of turbulent wind acted on wind turbine, rotational Fourier spectrum with considering rotational effect of rotor was deduced. Physical nature of the rotational Fourier spectrum embodied by coherence function and phase lag was indicated. Auto power spectral density and cross power spectral density of rotational Fourier spectrum with introducing phase lag were proposed. The spectrum matrix constructed by the module of rotational Fourier spectrum was decomposed with Cholesky's method, according to the spectrum representation method with introducing phase lag, the random turbulent wind speed field was generated by superposing a set of cosine functions. Finally, an example involving simulation of the longitudinal turbulent wind velocity time series of a 1.5 MW three-bladed pitch regulated wind turbine was investigated. The target spectrum and simulated spectrum were compared. The result shows that the proposed algorithm is more accurate to simulate the fluctuating wind velocity of rotational blade.

Abstract: This paper describes the classical individual pitch control algorithm. Firstly, transform the out-of-plane bending moment of each blade in the rotational coordinate to the hub loads proportional to the tilt and yaw moment in the fixed coordinate. Secondly, design the PI controllers to minimize the load. And then attach the increment pitch angle to the collective one. Simulations in the Bladed show that the individual pitch control can minimize the loads not only in hub tilt and yaw, but also in blade root.

Abstract: This paper presents wind energy conversion model, drive shaft’s dual-mass model and generator’s transient mathematical model for the transient analysis of fixed speed asynchronous wind generators, and analyzes the transient characteristics of the wind generators under the condition of low voltage fault. The control principles of two dynamic reactive power compensation equipments as static var compensator (SVC) and static synchronous compensator (STATCOM) are introduced. Take a wind farm consists of fixed speed asynchronous wind generators as an example, the two compensation equipments are simulated in PowerFactory/DIgSILENT to compare the effort of them on enhancing the low voltage ride-through capability of the wind farm.