NREL, Stuttgart University and DNV GL have completed tests with the control of an operational wind turbine with a ZephIR wind lidar. The usage of the ZephIR lidar system for feed-forward pitch control delivers a reduction of structural turbine loads enabling OEMs with the opportunities to achieve a lower cost of energy for the industry through more optimal turbine design.
The field testing was conducted on the US DOE/NREL CART3 test turbine, which is part of the comprehensive test facilities at the National Wind Technology Center (NWTC) in Boulder, Colorado. The ZephIR DM wind lidar is a circularly-scanned, continuous-wave coherent Doppler sensor. The ZephIR DM wind lidar offers benefits in turbine-mounted applications from power curve measurements to full turbine control as demonstrated in this project. Optimised for installation on a nacelle roof, ZephIR DM generates high-resolution line-of-sight Doppler measurements every 20 ms through a period of a continuous circular scan of 1 second. The measurements taken by ZephIR calculate various wind field quantities, such as rotor equivalent and hub height horizontal wind speeds, vertical wind shear, wind veer and wind yaw misalignment relative to the turbine axis at ranges from 10 m to over 300 m out in front of the turbine. The ZephIR DM lidar recorded valid signals throughout the 8 month measurement period, operating reliably, without intervention, in a wide range of atmospheric conditions, including heavy blizzards, low cloud and temperatures down to -22°C. Collectively the success of these pitch turbine control experiments have paved the way for subsequent trials on larger, 2MW class, onshore turbines and ZephIR Lidar confirms it is already working with OEMs in this area.