Advanced Materials Research Vols. 608-609

Abstract: The WRF model is employed to simulate the low-level wind field of a wind farm that located in the arid regions in northwest of China for February and October 2008. We presented some difficult issues using mosescale numerical model in low-level wind predicting, meanwhile, corresponding solutions are proposed. Some conclusions and achievements in wind forecasting are summarized; the planning and prospects of next phase also are illustrated.

Abstract: The relevant data sequences provided by numerical weather prediction are decomposed into different frequency bands by using the wavelet decomposition for wind power forecasting. The Elman neural network models are established at different frequency bands respectively, then the output of different networks are combined to get the eventual prediction result. For comparison, Elman neutral network and BP neutral network are used to predict wind power directly. Several error indicators are given to evaluate prediction results of the three methods. The simulation results show that the Elman neural network can achieve good results and that prediction accuracy can be further improved by using the wavelet decomposition simultaneously.

Abstract: The fault ride through capability of wind turbine is becoming more important with the rapid growth of wind power installed capacity. Among several grid faults the voltage swell is a critical event. Thus, to enhance the high voltage ride through capability of popular PMSG-based wind turbine, the behavior of the PMSG wind turbine when subjected to a voltage swell was analyzed and a strategy was proposed. The overvoltage results in an increasing converter DC bus voltage. By analyzing the vector diagram of line-side converter, the paper recommends increasing inductive current assisted with chopper resistors to ride through the overvoltage safely, and the reactive current reference calculation method is given. The analysis of the performance and the strategy is presented and verified by simulations with a 1.5MW PMSG wind turbine simulation model.

Abstract: Wind energy conversion is the fastest-growing source of new electric generation in the world. The unforeseen damages of a component in a wind turbine have significant impact on the wind turbines, especially offshore ones. There has been a trend towards adoption of various forms of condition monitoring and fault diagnosis to know the deteriorating condition for both mechanical and electrial components, well in advance of a breakdown. This paper review the most recent advances in these areas with a special focus on offshore wind turbines. Different type of faults on offshore wind turbines are reviewed, including gearbox and bearing failures, generators failures, rotor failures and electrical failures. And then two widely-used methods(vibration analysis and oil monitoring) for predictive condition monitoring and fault diagnosis in offshore wind turbines are reviewed.

Abstract: Cost-effectiveness analysis model is established in this paper to examine the influence of the incorporation of wind power to the whole power supply system. Thermal power plants are used as the backup for wind power due to its intermittence, which will increase the coal consumption so that lower the profit of the thermal power plants. A further optimization model is also established to work out the profit of both the power plants and the grid after the incorporation of wind power, and the influence on the CO₂ emission as well. It came to the conclusion that although the cost of coal-fired power plants increases because of offering back up to the wind power, CO₂ emission from the generation side will decline which has the environmental benefit.

Abstract: A numerical code, known as COUPLE, which has been developed to perform hydrodynamic analysis of floating body with a mooring system, is extended to collaborate with FAST to evaluate the interactions between wind turbine and its floating base. FAST is developed by National Renewable Energy Lab (NREL) for aeroelastic simulation of wind turbines. A dynamic response analysis of a spar type floating wind turbine system is carried out by the method. Two types of simulation of wind load are used in the analysis. One type is a constant steady force and the other is a six-component dynamic load from a turbulent wind model. Numerical results of related platform motions under random sea conditions are presented in time and frequency domain. Comparison of results is performed to explain the difference of two analyses. The conclusions derived in this study may provide reference for the design of offshore floating wind turbines.

Abstract: Static var compensator (SVC) is used to improve transient voltage stability of the asynchronous wind farm. The issue of voltage stability and transient stability of wind power system are also addressed. A novel control strategy of SVC is proposed instead of the types of traditional feedforward and uniline feedback to control SVC. The proposed method makes control performance better and the compensation efficiency higher. At the same time, balanced compensation strategy of orientation vector conversion is applied instead of traditional model of steady-state phasor to calculate the compensation electrical susceptance. Using this method can overcome the shortcoming of dynamic characteristics and adaptability. At last, the simulation results indicate this control strategy could improve the stability of wind farm effectively and quickly.

Abstract: A design approach of ice detection system for wind turbine is presented in this paper. Basic steps for design are proposed. Numerical arithmetic used for design configuration and shape of the icing prober is given. The arithmetic is composed of the Multiple Reference Frame (MRF) method to calculate flowfield of air, a Lagrangian method to compute droplet trajectories and a technique for fast computing ice accretion. Icing prober configuration for a 1.5 MW horizontal axis wind turbine is then obtained with the approach. The state of wind turbine icing can be reflected by the prober in real time. All these achievements build a good base for future research.

Abstract: In order to make wind power generation system be free from outside interference, and make doubly-fed induction generator (DFIG) easily operate at maximum power point under variable wind speed, simultaneous perturbation stochastic approximation (SPSA) algorithm for tracking maximum power of wind power generation system is proposed in this paper. SPSA algorithm indirectly controls DFIG speed through adjusting duty cycle of power converter, makes system operate at maximum power point under any wind speed, thus the maximum power output is transmitted to the load. SPSA algorithm not only does not need to set up PID three parameter values, but also does not anemometer and tachometer in practical applications. Simulation results show no matter how wind speed changes, SPSA algorithm can effectively improve power output of wind power generation system, and make tip speed ratio and power coefficient be near optimum value, reduce system cost.

Abstract: In order to promote the development of wind power and accelerate the efficient use of new energy sources, countries have brought energy storage systems into grid-connected wind farms to achieve efficient and stable operation of the wind power plant. This paper recounts the latest development status and trend of wind power at home and abroad, and introduces the principle of power conversion between energy storage system and wind farm. Based on the existing research results, it analyses power system stability related to wind power, low voltage ride-through ability of wind turbine, wind power penetration limit, as well as power quality issues. It also describes the new ideas about how to use energy storage technologies to solve the problems faced by the wind power.