海上风力发电液力调速控制系统分析

液力调速行星齿轮装置通过改变液力变矩器导叶开度,可以将变化的风速恒速输出,使得风轮追踪最佳风轮速度,提高海上风能利用率,保证同步发电机的转速维持同步转速,使发电频率稳定,不需要变频装置,提高风电机组的可靠性。建立海上风电机组传动系统的数学模型,分析液力调速行星齿轮装置参数对海上风电机组系统性能的影响规律。根据海上风电机组的运行特点和要求设计液力调速齿轮控制系统。

Dynamic Characteristics Analysis of the Offshore Wind Turbine Blades

The topic of offshore wind energy is attracting more and more attention as the energy crisis heightens.The blades are the key components of offshore wind turbines,and their dynamic characteristics directly determine the effectiveness of offshore wind turbines.With different rotating speeds and blade length,the rotating blades generate various centrifugal stiffening effects.To directly analyze the centrifugal stiffening effect of blades,the Rayleigh energy method (REM) was used to derive the natural frequency equation of the blade,including the centrifugal stiffening effect and the axial force calculation formula.The axial force planes and the first to third order natural frequency planes which vary with the rotating speed and length were calculated in three-dimensional coordinates.The centrifugal stiffening coefficient was introduced to quantitatively study the relationship between the centrifugal stiffening degree and the rotating speed,and then the fundamental frequency correction formula was built based on the rotating speed and the blade length.The analysis results show that the calculation results of the fundamental frequency correction formula agree with the theoretical calculation results.The error of calculation results between them is less than 0.5%.

Direct Power Control of Variable Wind Speed Based on the Doubly Fed Asynchronous Machine

In this work, the authors propose the study of a wind speed variable based on the DFAM （double fed asynchronous machine）. The model of the turbine is drawn from the classical equations describing the operation of a variable wind speed. The torque generated by the turbine is applied to the DFAM directly connected on the network side and the stator via a bidirectional converter side rotor. This configuration allows velocity variations of ±30% around the synchronous speed and the converter is then sized to one third of the rated power of the machine. The DFAM is controlled by a control vector ensuring operation of the wind turbine power coefficient maximum.

Study of a Particular Stack Performance in a Building in Italy

This paper describes a particular stack performance realized in a building （school） at real scale by computation of the wind induced ventilation and a comparison of the stack performance （airflow rate extracted and wind speed） respect to other systems （wind catcher, wind jetter and wind turbine） are also showed. The realization of the system, actually working, shows the synergy between a plant design and installation using traditional energy sources with innovative engineering techniques providing for the use of integrative energy. In this case, the wind action plays an important role for the conditioning of the school, integrating and giving a significant energetic contribution to the air cooling system. The school building （a nursery） has been built in Modena and is actually working.

A Mathematical Model for the Velocity Profile Internally to a Conical Diffuser

The use of diffusers around the horizontal-axis wind turbines has been widely studied since the diffuser improves the power coefficient of the turbine and it is often called DAWTs （diffuser augmented wind turbines）.Turbines using diffuser are called DWATs （Diffuser Augmented Turbines）,and have efficiency bigger than the Betz limit （maximum energy flow extracted = 59.26%）. Thus, this study presents a mathematical model describing the behavior of the velocity profile internally to a diffuser according to the characteristics of flow and geometry of a conical diffuser. The results are compared with experimental data and show good agreement.

Study on Blade Surface Flow around Wind Turbine by Using LDV Measurements

This paper has attempted to study a mechanism of three-dimensional flow around a horizontal axis wind turbine(HAWT) rotor blade. An experimental study of the flow phenomenon in the vicinity of the wind turbine blade is a challenging endeavor. In this research, the HAWT model with 2.4 m diameter was tested in the large wind tunnel. The flow around the rotating blade surface was measured simultaneously for three velocity components, and two probes were used for the synchronized measurement of three-dimensional flow components. The local velocity was detected for the single seeding particle measured in the point where three pairs of laser beams intersected. Blade sections of interest in this study are composed of radial positions r/R = 0.3, 0.5 and 0.7. Optimum and low tip speed ratio flow characteristics were also compared. The velocity flow vector, skin friction coefficient and bound circulation were calculated from LDV measurements, and the experimental research showed reasonably and clearly the experimental results.

Interaction between the atmospheric boundary layer and a standalone wind turbine in Gansu—Part I： Field measurement

Experiments and numerical simulations of the wake field behind a horizontal-axis wind turbine are carried out to investigate the interaction between the atmospheric boundary layer and a stand-alone wind turbine. The tested wind turbine（33 k W） has a rotor diameter of 14.8 m and hub height of 15.4 m. An anti-icing digital Sonic wind meter, an atmospheric pressure sensor, and a temperature and humidity sensor are installed in the upstream wind measurement mast. Wake velocity is measured by three US CSAT3 ultrasonic anemometers. To reflect the characteristics of the whole flow field, numerical simulations are performed through large eddy simulation（LES） and with the actuator line model. The experimental results show that the axial velocity deficit rate ranges from 32.18% to 63.22% at the three measuring points. Meanwhile, the time-frequency characteristics of the axial velocities at the left and right measuring points are different. Moreover, the average axial and lateral velocity deficit of the right measuring point is greater than that of the left measuring point. The turbulent kinetic energy（TKE） at the middle and right measuring points exhibit a periodic variation, and the vortex sheet-pass frequency is mostly similar to the rotational frequency of the rotor. However, this feature is not obvious for the left measuring point. Meanwhile, the power spectra of the vertical velocity fluctuation show the slope of-1, and those of lateral and axial velocity fluctuations show slopes of-1 and-5/3, respectively.However, the inertial subranges of axial velocity fluctuation at the left, middle, and right measuring points occur at 4, 7, and7 Hz, respectively. The above conclusion fully illustrates the asymmetry of the left and right measuring points. The experimental data and numerical simulation results collectively indicate that the wake is deflected to the right under the influence of lateral force. Therefore, wake asymmetry can be mainly attributed to the lateral force exerted by the wind turbine on the fluid.

Optimal Operation of Turbo Blowers Serially Connected Using Inlet Vanes

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers' operating performance.To analyze three-dimensional flow field in the turbo blowers serially connected,general analysis code,CFX,is introduced in the present work.SST turbulence model is employed to estimate the eddy viscosity.Throughout the numerical analysis,it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively,because pressure loss rapidly increases below 60 degree of a vane angle.Efficiency also has almost the same values from 90 degrees to 60 degrees of a vane angle.It is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.