Applied Mechanics and Materials Vols. 448-453

Abstract: Load tracking and output forecast error are less researched in wind and photovoltaic (PV) systems synthetic of output coupling power in present time. This paper using the technology of data mining of according to the wind and PV output characteristics with different scenario data partitioning method to the Wind and PV resource rich region of the actual wind power and PV output data divides the scene under the typical scenario data of division of Wind and PV complementary output coupling characteristics are analyzed and studied the mechanism of synthesis of output tracking system load characteristics and improve the output prediction error problem. Studies have shown that Wind and PV complementary synthetic efforts to a certain extent, reduced the coupling characteristics of output volatility, the system load tracking degree reached 14.1%.

Abstract: The prediction accuracy of wind power is important to the power system operation. Based on BP neural network used to forecast directly and time-series method used to forecast indirectly, the output wind power prediction of 4 hours in advance was studied in this paper. Simulation results showed that the performance of direct prediction is better, and the reason for that was analyzed in the paper. Finally, error analysis of prediction was researched. Comprehensive evaluation of prediction error which contains horizontal and longitudinal error evaluation was proposed.

Abstract: The operational performances of coastal wind farms, located at the east coast of Jiangsu Province of China, are reported in this paper. The result shows that although a rich wind resources predicted in this area, a strong variation of wind resources characteristics are observed between wind farms. Annual averaged wind speeds of five wind farms at hub height range from 4.8 to 6.6 m/s. In addition, the wind shear coefficient shows largely different although they appear to agree with coastal region characteristics. Ru Dong not only has the highest wind shear coefficient but also a largest range of wind shear coefficient variation amplitude. The Capacity Factors of the selected wind farms range from 16% to 27%. Ru Dong shows a lowest Capacity Factor of 16% which may due to the low average wind speed and high wind shear coefficient. On the contrary, Da Feng has a lower Capacity Factor with sensible wind resources indicating either an improved wind turbine technology or an optimized wind farm operational maintenance is needed to increase wind farm efficiency. The result obtained in this paper provides valuable information for future offshore wind farm development in China.

Abstract: With an increasing amount of wind energy installed, the behavior of wind turbines during grid disturbances becomes more and more important. This paper introduces the basic structures of doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines and analyses the capability of low voltage ride through (LVRT) of the wind turbines. Finally this paper elaborates the principle and the procedures of the LVRT tests. The results of the tests show that: Doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines are equipped with LVRT capability. The turbines are able to operate normally without disconnection and provide reactive power to support grid restoration during the dip. The direct-drive permanent magnet synchronous wind turbines are superior to the doubly-fed wind turbines on LVRT since a full-power converter is used.

Abstract: China has great potential in offshore wind energy and makes an ambitious target for offshore wind power development. Operation and Maintenance (O&M) of offshore wind turbines become more and more important for China wind industry. This study introduces the current offshore wind power projects in China. Donghai Bridge Offshore Demonstration Wind Farm (Donghai Bridge Project) is the first commercial offshore wind power project in China, which was connected to grid in June 2010. O&M of Donghai Bridge Project represent the state-of-the-art of China offshore O&M. During the past two and half years, O&M of Donghai Bridge Project has gone through three phases and stepped into a steady stage. Its believed that analysis of O&M of Donghai Bridge Project is very helpful for Chinas offshore wind power in the future.

Abstract: At present, the difficulty of wind power integration has resulted in a large number of wind curtailment phenomena and wasted a lot of renewable energy. Due to the significant instability, anti-peak-regulation and intermittency of wind power, wind power integration needs an accurate prediction technique to be a basis. ARMA model has the advantage of high prediction accuracy in predicting short-term wind power. This paper puts forward the method for short-term wind power prediction using ARMA model and carries out empirical analysis using the data from a wind farm of Jilin province, which shows the science and operability of the proposed model. It provides a new research method for the wind power prediction.

Abstract: As the capacity of wind turbine increases, unsteady blade loads and performance caused by asymmetrical effects like turbulence, wind shear and tower shadow lead to fatigue loads which seriously affect wind turbine life cycle. This paper focused on wind turbine fatigue load response characteristics, built the multiple input multiple output linearized matrix model, introduced individual pitch control algorithm for optimized disturbance control based on norm theory. Modeling, simulation and verification of the control algorithm are conducted in Matlab. The investigation is conducted based on a 2MW doubly-fed wind turbine. By comparing the results of wind turbine deflection rate and angle deflection rate to collective pitch control method, it shows the individual pitch control algorithm can significantly reduce wind turbine fatigue load, and the control effect is superior to traditional control algorithm.

Abstract: Nowadays actual scientific problem of renewable energy is the problem of developing control systems, that ensure the generation of stable voltage in a changing environment. This paper presents a structure and methods of synthesis of control system development, which allow to decide the indicated problem. An electric subsystem of wind power plant is a well-known structure with well-known advantages, consisting mainly of double-fed induction generator (DFIG) and power converter in the circuit of rotor. Operation of the control system based on the original nonlinear mathematical model of DFIG in rotational "dq" coordinates, taking into account the nonlinear external and internal DFIG disturbances, such as inductances of coil winding, changes of coil winding resistances from temperature, etc. The study received adaptive control algorithms of the wind turbine output voltage parameters.

Abstract: With the variation of the unsteady incoming flow and impeller rotation, when attack angles of the incoming flow is bigger than the critical angle of attack, there are unsteady separation and dynamic stall on the pressure surface of the impeller. Dynamic stalls are of common occurrence during wind turbines operation. And the aerodynamic characteristics and efficiency of wind turbine are largely affected by the dynamic stall.Therefore,the study of dynamic stall has a great significance over the optimization design of the wind turbine. The paper performs numerical simulation in the dynamic stalls of the 1.2MW horizontal-axis wind turbine, comparing the stalling difference between two-dimensional static and rotating condition. Besides, it also contrasts the stalling condition surface pressure coefficient along the different blade spanwise sections in rotating condition of the same attack angle. And the finding is that the attack angles in rotating condition is bigger than that in the two-dimensional static condition; the surface pressure coefficient is almost equivalent in static and rotating condition when attack angle is smaller than stalling angle; the peak of negative pressure at the leading edge of blade in rotating condition is far bigger than the peak of negative pressure in static condition when attack angle is smaller than static stalling angle. Airflow stall delay occurs when near the blade root. Stall delay phenomenon gradually weakened along the direction of blade radius.

Abstract: Specifically address the design of a 5KW H-type vertical-axis wind turbine (H-VAWT) with NACA 0018 airfoil considering the factors that affect wind turbine power. The double-multiple streamtube (DMS) theoretical model is analyzed and summarized and calculated by Matlab. The 5KW H-type vertical axis wind turbines aerodynamic performance is calculated by the model written in Matlab. The curve of the power coefficient as a function of the tip-speed ratio and the curve of the normal force coefficient and the tangential farce as a function of the blade position is given by Matlab. From the curves we can see that upwind rotor aerodynamic load is larger, downwind rotor aerodynamic load is smaller and there is a serious flow retarding effect in the rotor downwind area.