Case Study 7: CFD Torque Controlled Tidal Turbine

The development of a whole system, fully-coupled model of a laboratory-scale hydrokinetic tidal turbine, along with its interactions with the ocean environment and its electrical control system is described. The model was developed using Computational Fluid Dynamics, Large Eddy Simulation and Actuator Line Method coupled with an external torque control system. The control system is developed from the optimal torque speed curve based Maximum Power Point Tracking algorithm.

The hydrokinetic tidal turbine and the control system models were implemented independently. They were coupled in order to reach an energy balance between the surrounding flow, the tidal turbine, and the control system. Flow stream velocities were imposed in the inlet of the model domain, starting the rotor from zero rotational speed. After the optimal rotational speed is attained, the electrical power generated and the loads experienced by the turbine rotor were studied. In the simulations, the tidal device is controlled to keep the optimal power production for any flow stream velocity.

The Fully-coupled whole system model.

Velocity magnitude and turbulence intensity at rotor cross-section.

Time-series of rotor thrust and torque.

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