The wind turbine safety standard includes a coherent gust model with a wind speed increase and direction change of 10 s. With the increasing rotor size of modern wind turbines this model is criticized for being uniform across these large rotors. In this study we investigate measurements of coherent gusts with a ramp-like increase in wind speed. We define a new method for ramp detection and characterization and compare it with the coherent gust model from the wind turbine safety standard.

The paper studies the effects of uncertainties in aeroservoelastic wind turbine models. Uncertainties are associated with the wind inflow characteristics and the blade surface state, and they are propagated by means of two non-intrusive methods throughout the aeroservoelastic model of a large conceptual offshore wind turbine. Results are compared with a brute-force extensive Monte Carlo sampling to assess the convergence characteristics of the non-intrusive approaches.

In this study the capabilities of detecting wakes in the inflow of turbines by nacelle-mounted lidars are investigated. It is shown that higher turbulence levels can be measured within a wake by estimating the Doppler spectrum width. In an experimental setup all half- and full-wake situations have been identified. A correction method for the influence of the wake on the lidar system has also been proposed..

In this study a model of the coherence between turbine- and lidar-estimated rotor-effective wind speed (REWS) is presented. The model is compared against experimental data from two field tests using two- and four-beam nacelle-mounted lidar systems on a test turbine. The proposed model agrees better with the field data than previously used models. Also, it was shown that the advection speed can be estimated by the REWS measured by the lidar.

Multi-element ducts are investigated to further improve the aerodynamic performance of ducted wind turbines. CFD simulations are performed for a multi-element duct geometry consisting of a duct and a flap; the goal is to evaluate the effects on the aerodynamic performance of the radial gap length and the deflection angle of the flap. Increasing the radial gap length results in an augmentation of the total thrust generated by the DWT, whereas a larger deflection angle has an opposite effect.

UAS systems provide in situ measurements of turbulence and wind conditions. In the presented paper, the tip vortex generated by wind energy converters (WECs) is measured by a fixed-wing UAS and compared to an analytical model as well as a literature value. The results show good agreement. The presented method is a basis for future measurement campaigns to compare UAS measurements with numerical simulations of WEC wakes.

An important design criterion for the electric drive system of a wind turbine is the fulfilment of grid codes given by transmission system operators. The grid codes state how wind turbines/farms must behave when connected to the grid in normal and abnormal conditions. A type of testing equipment that comprises the use of fully-rated voltage source converter in back-to-back configuration for grid code testing is proposed. Test results of a 4 MW wind turbine and an 8 MW test equipment are shown.

This paper identifies the most sensitive parameters for the load response of a 5 MW wind turbine. Two sets of parameters are examined: one set relating to the wind excitation characteristics and a second related to the physical properties of the wind turbine. The two sensitivity analyses are done separately, and the top most-sensitive parameters are identified for different load outputs throughout the structure. The findings will guide future validation campaigns and measurement needs.

Wind park planning and power system design require robust wind resource information. While most assessments are restricted to the last four decades, we use centennial reanalyses to study wind energy generation variability in Germany. We find that statistically significant multi-decadal variability exists. These long-term effects must be considered when planning future highly renewable power systems. Otherwise, there is a risk of inefficient system design and ill-informed investments.

This paper presents a comparison study of the simplified model QuLAF (Quick Load Analysis of Floating wind turbines) and FAST for the planar version of various design load cases, in order to investigate how accurate results can be obtained from this simplified model. The overall analysis shows that QuLAF is generally very good at estimating the bending moment at the tower base and the floater motions, whereas the nacelle acceleration is generally underpredicted.