Final colloquium Ayush Sharma

Constrained Single Blade Control for Wind Turbine Blade Load Reduction

Supervisor: Dr. Sebastiaan Mulders

Abstract: As wind turbines keep increasing in size, there is a growing emphasis on minimizing the fatigue-inducing dynamic loads on their rotating and non-rotating components. Individual Pitch Control (IPC)  is one such technique aimed at alleviating these loads, wherein each blade receives an additive, periodic, zero-mean pitch command to compensate for the periodic blade-root moments that, in turn, arise due to asymmetries in the wind field. Over the course of the last two decades, IPC has undergone extensive research, both from simulation-based studies to practical validations on operational wind turbines. While these studies have pointed to an increased actuator duty cycle and, consequently, a higher risk of fatigue failure of the actuator subsystem, research on constraining IPC pitch action is still nascent. Most of the constrained IPC techniques proposed in the literature are input-constrained and not output-constrained, in that they impose limiting constraints on the individual pitch inputs but not the blade moment outputs. On the other hand, the output-constrained IPC techniques proposed in the literature have employed the use of advanced control strategies, such as MPC, which still await widespread industrial adoption due to a preference for classical control strategies in the industry.

This thesis proposes a classical control-based strategy for constraining single blade control (SBC) action while compensating for the phase loss in the system. To develop this strategy, several amplitude demodulation techniques are reviewed, and an unconstrained SBC strategy with phase loss compensation is established. High-fidelity simulation studies demonstrate that the constrained SBC strategy allows for a trade-off between the actuator duty cycle and fatigue loading on the blades.