A Study of Dynamic Coupling and Composite Load Control for Wind Turbines

*† ‡ Wind turbine components are sized according to their expected fatigue loads and any reduction in these would decrease costs and prolong working life. Wind turbine control is a multivariable problem with large interaction across multiple control channels (inputs to objectives). This article studies coupling and investigates a composite load controller for a wind turbine, consisting of a linear quadratic regulator for the loads and a baseline power controller for speed and torque regulation. The load objectives were to reduce tower foreaft, low speed shaft (LSS) tilt, and LSS yaw bending fatigue. Simulations in above rated wind conditions evaluated the composite design against the baseline controller alone, as well as a classical architecture with multiple single-input single-output (MSISO) loops. In this way, it is important to compare to a control design that is not aware of any coupling. Results showed significant mitigation of damage equivalent loads in the tower fore-aft, and LSS tilt and yaw directions across both designs when compared to baseline. The composite controller achieves better load reduction without the need for filtering out the effects of other channels, as would be required in the MSISO design.