LIDAR‐assisted feedforward individual pitch control of a 15 MW floating offshore wind turbine

Abstract

Nacelle‐mounted, forward‐facing LIDAR technology is able to deliver benefits to rotor speed regulation and loading reductions of floating offshore wind turbines when assisting with blade pitch control in above‐rated wind speed conditions. Large‐scale wind turbines may be subject to significant variations in structural loads due to differences in the wind profile across the rotor‐swept area. These loading fluctuations can be mitigated through the use of individual blade pitch control (IPC). This paper presents a novel LIDAR‐assisted feedforward IPC approach that uses each blade’s rotor azimuth position to allocate an appropriate individual pitch command from a multi‐beam LIDAR. In this computational study, the source code of OpenFAST wind turbine modelling software was modified to enable LIDAR simulation and LIDAR‐assisted control. The LIDAR simulation modifications made are present in the latest OpenFAST release, v3.5. Simulations were performed on a single 15 MW floating offshore wind turbine across the above‐rated wind spectrum and using multiple turbulent wind profiles. Under a turbulent wind field with an average wind speed of 17 ms‐1, the LIDAR‐assisted feedforward IPC delivered root mean squared error and standard deviation reductions to key turbine and substructure parameters by up to 57%. Feedforward IPC delivered enhancements of up to 15% over feedforward collective pitch control, which instead provided the same feedforward command to all blades, compared to the baseline feedback controller. The reductions to the standard deviation and range of the rotor speed may enable structural optimisation of the tower, while the reductions in the variations in the loadings present an opportunity for reduced fatigue damage on turbine components and, consequently, a reduction in maintenance expenditure.