Neungsoo Yoo

Development of a Time-Domain Simulation Tool for Offshore Wind Farms

A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie’s eddy viscosity wake model to construct the simulation tool. The wind turbine model also includes an aerodynamic model that is a look up table of power and thrust coefficients with respect to the tip speed ratio and pitch angle of the wind turbine obtained by a commercial multi-body dynamics simulation tool. The wake model includes algorithms of superposition of multiple wakes and propagation based on Taylor’s frozen turbulence assumption. Torque and pitch control algorithms were implemented in the simulation tool to perform max-Cp and power regulation control of the wind turbines. The simulation tool calculates wind speeds in the two-dimensional domain of the wind farm at the hub height of the wind turbines and yields power outputs from individual wind turbines. The NREL 5MW reference wind turbine was targeted as a wind turbine to obtain parameters for the simulation. To validate the simulation tool, a Danish offshore wind farm with 80 wind turbines was modelled and used to predict the power from the wind farm. A comparison of the prediction with the measured values available in literature showed that the results from the simulation program were fairly close to the measured results in literature except when the wind turbines are congruent with the wind direction.

Monitoring of small wind turbine blade using FBG sensors

Dynamic behavior of a small wind turbine blade has been analyzed experimentally. Arrays of Fiber Bragg Grating (FBG) sensors and strain gauges were used to extract mode shapes of a small wind turbine blade made of fiber reinforced plastic (FRP). The root of the blade was fixed by a cantilever system developed for this study and dynamic strains from the sensors attached from the top and bottom surfaces of the blade were measured. The fundamental frequencies and higher modes of the blade cantilever system obtained from both sensors were almost identical. The mode shapes were also close but slightly different from each other. The differences are considered due to the fact that the top and bottom sections are non-symmetric.

Site calibration for the wind turbine performance evaluation

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine’s hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the TaeKwanRyung test site are presented using three-month wind data from a reference meteorological mast and the other mast temporarily installed at the site of wind turbine. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.