Advanced Materials Research Vols. 512-515

Abstract: In this paper a new bucket configuration for Savonius wind generator is proposed. With the aim to increase the effect of the overlap ratio R_S on the wind turbine performances and to increase the amount of lift force able to produce torque and power, slotted blades are investigated by means of the Computational Fluid Dynamics analysis. The numerical analyses are performed by Comsol Multiphysics^® and the results obtained for a Savonius wind turbine with overlap only are compared to numerical and experimental benchmarks. Parametric analyses are performed, for fixed overlap ratio, by varying the slot angle β and the results show that for low angle β the Savonius rotor exploits improved performance at low tip speed ratio λ, evidencing a better starting torque. This circumstance is confirmed by the static analyses performed on the slotted blades in order to investigate the starting characteristic of the proposed Savonius wing generator configuration.

Abstract: A three dimensional numerical method and its computer codes, which are suitable to predict the process of horizontal axis wind turbine icing, are presented. The method is composed of the Multiple Reference Frame (MRF) method to calculate flowfield of air, an Eulerian method to compute collection efficiency and a three dimensional icing model companying with an iterative arithmetic for solving the model. Ice accretion on a 1.5 MW horizontal axis wind turbine is then computed with the numerical method, and characteristics of droplet collection efficiency and ice shape/type are obtained. The results show that ice on the hub and blade root is slight and it can be neglected comparing with ice near blade tip. From blade tip to root, ice becomes thinner and glaze ice may changes into rime ice.

Abstract: The fast development of wind power generation brings new requirements for wind turbine integration to grid. In order to improve the lower voltage ride through(LVRT) capability of fixed speed induction generator(FSIG) in wind power generating systems, the mathematic model of FSIG, supercapacitor(SC) and converter is built in DIgSILENT in this paper. A control strategy for FSIG and SC based on wind farms is proposed to enhance the terminal voltage of point of common coupling (PCC) after the clearance of an external short circuit fault. The simulation results show that the terminal voltage of PCC can be significantly improved when there is extra active and reactive power compensation available from SC.

Abstract: Fault feature extraction method based on Empirical Mode Decomposition (EMD) and fault diagnosis model based on Least Squares Support Vector Machines (LSSVM) were proposed after typical faults in drive train for wind turbines being analyzed. An experiment was designed to verify the validity of feature extraction method and the intelligent diagnosis model. The results showed that EMD can effectively extract fault characteristics of the drive train in wind turbines, the classification speed and diagnosis accuracy of LSSVM classifier based on radial basis function are better than the SVM, BPNN and other classifiers which are commonly used in practice.

Abstract: Effective wind power prediction on wind farm can not only guarantee safe operation of wind farm, but also increase wind power storage and utilization efficiency. This research combines mesoscale numerical weather prediction model with BP neural network model for the use of wind power prediction. WRF model is used to recalculate the meteorological elements of trial wind farm from Jun. 2008 to Jun. 2009, and the accuracy check result shows that the correlation coefficient between predicted value and corresponding measured value of wind speed reaches 0.72. Predictions accuracy of wind direction, air temperature, humidity and air pressure are also precise, which meets the requirement of building BP neural network prediction model. The BP neural network prediction models of output power of 40 wind turbines are established on trial wind farm one by one, to analyze the influence of data normalization method and neuron number at the hidden layer on prediction accuracy. The prediction test every 10 minutes, with the actual effect of 24 hours, is done for 26 days, and prediction accuracy test is conducted by using independent samples. The result shows that relative root mean square error of the output power of the single wind turbine from 24.8% to 32.6%, and the correlation coefficient between predicted value and measured value is from 0.45 to 0.68; relative root mean square error of the whole wind farm is 21.5%, and the correlation coefficient between predicted value and measured value is 0.74.

Abstract: Different types of wind turbine generate different noises in normal condition. A comparison of noises from local spot by means of modern acoustic measurement is carried out between 300W concentrated wind energy turbine and ordinary wind energy turbine, and conclusion is that the noises from the concentrated wind energy turbine are lower than that from the ordinary one. Besides, the main noises are from turbine blades and increase with the wind speed on both turbines.

Abstract: Doubly fed induction generator (DFIG) is now becoming one of most widely used wind turbines in global market for wind power generation, due to its outstanding advantages. However, the DFIG is sensitive to grid faults. The DFIG will have to be removed from the grid if there’s no protection appliance in it. Therefore, the crowbar protection is widely used in the world for improving the low voltage ride-through ability of wind turbines. This paper analysed the operating characteristics and short-circuit current of DFIG under symmetrical short-circuit fault with respect to different sags to grid voltage, which on the basis of DFIG wind turbine with crowbar protection. And the expressions of short-circuit current under symmetrical short-circuit fault for DFIG were derived. The effectiveness of the expression was simulated in PSCAD/EMTDC.

Abstract: Traditional decoupling control strategy of doubly-fed induction generator (DFIG) wind turbine makes little contribution to system inertia and do not participate in the system frequency control, the synchronization of large-scale wind power requires wind turbine have the ability to participate in the regulation of power system frequency. This paper adds a frequency control segment to traditional DFIG wind turbine and considers the doubly-fed wind turbine operating on the state of the super-synchronous speed, by analysis the effect of inertia and proportional control strategies, a fuzzy control strategy which combines the advantages of the former two control strategies is proposed, simulation results show that this control strategy can more effectively improve the system frequency response.

Abstract: Energy is an essential part in life. Currently wind power is the most technologically mature industry in new energy industry, possessed with the most mechanized prospect. The development of Indian wind power industry has gained remarkable achievements, with its wind turbines manufacturing capability and total installation capacity ranking front among current undeveloped countries. Power plants can use wind turbines rather than steam to generate electricity. Being in use with a large scale, wind power can have a significant effect on the growing global need for more energy and efforts to stop climate change. Effective government support, active technological research and international development path are the basic motives to promote the prosperity of Indian wind power industry. With reference to experience from India, enforcing planning, regulation and support and cultivating self innovative ability should be direct countermeasures for our own wind power industry development.

Abstract: Direct drive permanent magnet synchronous generator have the advantages of direct drive, simple structure, high efficiency and so on, in which make it become one of mainstream models within MW wind turbine presently. Making the direct drive permanent magnet wind power generation system as the main research object, based on the principle of the operating characteristics of direct drive permanent magnet synchronous wind generator ( DDPMG ), establish mathematical model of the whole system including wind turbine, direct drive permanent magnet synchronous generator and machine side converter, applying the method of stator flux orientation to make the study of vector control strategy, to build the simulation model of direct drive permanent magnet synchronous generator system with Matlab to simulate the operation of generator when wind speed changes by step, the results validate the reasonableness of the model and the correctness and feasibility of the control strategy.