The effect of actuator dynamics on active structural control of offshore wind turbines

When implementing active structural control in large scale wind turbines, care must be taken to accurately model the dynamics of the actuator in order to develop a robust control system. In this paper, a limited degree of freedom model is constructed, and the effects of both actuator dynamics and control-structure interaction are investigated for an electric motor. The model is analyzed in the frequency domain in order to highlight these effects. The performance of the active control model considering actuator dynamics is compared to previous work in which an ideal actuator was used. It is demonstrated that while loading is reduced for cases that include a more realistic actuator model, greatly increased actuator power consumption makes neglecting control-structure interaction in controller design undesirable. Finally, the impact of the mechanical design of the actuator on control-structure interaction is analyzed. It is shown that by changing the gear ratio of the actuator, the effects of control-structure interaction can be reduced.