Advanced Materials Research Vols. 512-515

Abstract: The study of aerodynamic performance of vertical axis wind turbine is the basis of the VAWT design. The double disk multiple stream-tube, one of the numerical models for predicting the aerodynamic performance of the wind turbine, was used to calculate the aerodynamic performance of the Sandia DOE-17m VAWT. As shown in the comparison of the calculation results and the field test data, the DDMT model is efficient in predicting the aerodynamic performance. And then, a deep analysis of the inherent mechanisms that how the geometric parameters of wind turbine rotor like height to diameter ratio, solidity, chord and the number of blades affect the aerodynamic performance of turbine was made in the present work. The results will be the theoretical basis for the optimization of the design in aerodynamic performance of VAWT in the future work.

Abstract: World-wide demands for sustainable energy have brought increased attention to the improvement of wind turbine technology. Magnetic bearings promise to improve wind turbine performance by reducing frictional losses and mitigating vibration due to rotor imbalance and wind disturbances. However, testing must be performed to validate and quantify these advantages if magnetic bearings are to be used efficiently. Therefore, a practical testbed for a wind turbine with a magnetic bearing system has been developed, including the design of a passive rare earth magnetic bearing and fixture. This testbed will provide experimental vibration and efficiency data needed to extend past research in wind turbine modeling and design to include recent advances in magnetic bearing technology.

Abstract: Core of the topological optimization site selection of offshore wind farm is Delphi method. The paper divides the investigated experts into industry experts and professional experts, which respectively score the weighting coefficient and its value of the influence factors of offshore wind farm. The separate marking scheme can well develop the ability of experts, avoid the specialty bias and thereby improve the assessment accuracy. Another modification is to apply the accumulative vote method in the first stage of topological optimization site selection instead of designers’ own judgments, which gives a good solution to classify the disputed factors, and avoids fault or deviation due to the knowledge deficiency of designers. In addition, the data analysis results should be reassessed by the industry experts. And in company with the reassessment opinion the data analysis results are the basis for designers to determine the best sea area for offshore wind farm construction, which gives an extra guarantee for the scientific site selection.

Abstract: Based on field theory and air dynamics theory, two kinds of different curvature blade rotation of velocity and its distribution area were simulated, through the establishment of the three-dimensional flow model for the scenery tower fan blade generator and the adoption of RNGK-epsilon turbulence model. Then reach a conclusion from comparison: Smaller curvature leaf has a higher wind speed than the bigger one, which is easy to wind energy conversion under the common function of the force in the rotating area.

Abstract: Wind turbine gearbox is a key component to transmit power in wind turbine driveline. It is necessary for gearbox to have high reliability and durable quality, and so, it is obviously important to analyze the reliability of key components and the root of common failure. By means of RomaxWIND software, gearbox simulation model was built which is based on the flexible FE structures. Considering the effects of flexible FE structures, such as housing and ring gear, and capturing system effects, analysis is performed to estimate the performance of components under 20 years’ LDD, and the bearing and gear report were generated. Gear mesh misalignment is one of the major gearbox failure causes. In view of it, three different models were built for the analysis of mesh misalignment, the result reveal that the effect of flexible FE structures should not be ignored.

Abstract: The application of evaporative cooling technology in the cooling of large wind power generator is a new attempt in the discovery of wind power energy. In some particular circumstances, the air-cooling condenser must be adopted as the secondary cooler in the evaporative cooling system of large wind generator. For the cooling medium in the air-cooling condenser is the air and the distribution of temperature is uneven along the cooling tube, so it’s necessary to do deep research on it. Experiments are carried out to study the heat transfer characteristics of the air-cooling condenser used in the Close-loop Self-circulating (CLSC) evaporative cooling system. The temperature distribution and the heat transfer can be acquired from the experiment. Thorough study is carried out on restart up of the close-loop evaporative cooling system of the wind power generator. Experiments are done in the laboratory and real wind power generator, and it’s found that there is a critical point in the restart up of the generator. Only if the flow head overcome the critical point can the wind power generator restart automatically. The result shows that heat transfer can be enhanced by some special method and the air-cooling condenser can satisfy the demand of the cooling system.

Abstract: For the incompletion problem of sensors’ collected data in fault diagnosis of the wind power system, this article puts forward a kind of multiple level rules set based on rough set. First, let the sensors’ collected data go through Fourier transform and extract its feature attributes as well as discrete them. Establish the decision table of fault diagnosis according to attribute values. Then set out from the decision table to establish a multiple level set of nodes with diverse reduced levels and deduce the rules of each node, which has a corresponding belief level. When in reasoning and decision-making of the new data using the multiple level rules set, match the information of the new data with the rule of its corresponding node. Finally, achieve the fault diagnosis of wind power generation system by choosing comprehensive evaluation algorithm. The result of the diagnosis example shows the reliability and accuracy of this method in the diagnosis of fault types for wind power generation system.

Abstract: Mode analysis for wind turbine is more and more important with the large-scale direction development of wind turbines. Considering twist angle of blade, centrifugal force, weight of blade, weight of tower and nacelle, turbine inertia, traditional transfer matrix theory is amended and applied in the mode analysis of wind turbine in this paper. Applying amended transfer matrix theory, the mode analysis of a real wind turbine is made and the analysis results are compared with the calculation results from NREL Mode program. The comparison results show that amended transfer matrix theory takes wind turbine inertia into account and have higher accuracy.

Abstract: Development and utilization of renewable energy is important in optimize the power structure, save energy, protect environment, the development of low carbon economy has a positive role. Under the circumstances with wind machine price differ not big. The construction investment had little difference, under different capacity wind farm of the same capacity with different units. But when there is a bigger difference in wind machine price , it can be determination the rationality of the wind farm’s investment by the difference of the machine’ price preliminary. Also, it's available to estimate the whole investment. The wind farm 's permanent land area, according to the scale of wind farm, by estimating wind machines’, and the booster station, permanent land of transmission line and approach road area, then to determine the rationality of land area., on the basis of determining the wind farm project.

Abstract: Wind power is the most fast growing energy source in the world while its intermittency and uncertainty generate stability, reliability and power quality problems in the electric grid. A battery/supercapacitor Hybrid Energy Storage System (HESS) is integrated to the directly driven Wind Turbine Generation (WTG) system to achieve a better wind power output characteristic. When integrated to a grid connected WTG, the supercapacitor and battery respectively absorbs the high frequency part and low frequency part of the wind fluctuations. Feedback elements are added to achieve a better performance of this management algorithm. While for a HESS applied to the stand-alone WTG system, the supercapacitor supports the frequency of the isolated system after the islanded operation and PI controllers are used. The control models are developed by the User Definition (UD) module on Power System Analysis Software Package (PSASP). Simulations are carried out to verify the control strategies effective and feasible.