Recently, tidal current turbines have gained high attention as systems extracting predictable and sustainable renewable energy, but a commercial power generation in an array form is not started yet due to technical, financial, and environmental uncertainties. In technical aspects, power efficiency and structural safety would be critical for the success in the tidal current generation. Active control is a powerful approach for achieving the high efficiency as well as the safe operation in the conditions of the variable direction and the variable speed of the tidal current even though the complexity of the turbine systems increases. This study is focused on the development of an active controller in the tidal current turbines. The new concept that we have developed is the yaw control of the turbine systems by a rudder. In order to validate our new active-control concept, we conducted the indoor experiments of a 1/15 scale turbine model including the active controller. The effect of the yaw control on the power efficiency was analyzed and minute yaw control as well as 180 degree turn by the controller was demonstrated. After the validation, the active-controller was enlarged to 1/5 scale model and was successfully demonstrated in an outdoor facility. Eventually, based on the results of this study, the full-scale model of 200kW capacity and the corresponding activecontroller will be fabricated and be validated by in-situ tests over 2 m/s at the Uldolmok strait in South Korea.

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