The importance of control in wind turbine design and loading

The importance of the controller in determining the design loads of a wind turbine has been recognised for many years. This paper will discuss this topic from the following perspectives: Approaches to the design and tuning of closed loop controllers: fatigue loading can be reduced by using advanced control methods, sometimes dramatically. Classical design methods currently predominate, although there may also be a role for other approaches such as model-based methods. Network faults: The response of wind turbines to network faults such as voltage dips are of increasing concern for turbine designers and network operators, and modifications to the control system may be required in order to minimise the probability of turbine shut-down following a short-duration network fault, as well as to minimise the loading consequences of such events. Advanced simulation tools capable of dealing with these events are required so that the most appropriate strategies can be devised. Interactions between closed loop and supervisory control: supervisory control events such as shut-downs can be a source of design-driving loads, although these can often be mitigated by careful consideration of the details of the shut-down control and how it may interact with the closed loop control. Also the advanced closed-loop methods may themselves have consequences for extreme loads, sometimes requiring careful consideration of shutdown strategies. The distinction between controlled shutdowns and safety system shutdowns is very important to consider.