Rotational speed prediction for rated power operation of a horizontal axis tidal turbine under surging motion conditions

Under actual sea conditions, a floating horizontal-axis tidal power device (FHATPD) will experience a six-degree-of-freedom (6-DOF) wave-induced motion response, resulting in a change in the relative inflow velocity to the horizontal-axis tidal turbine (HATT). If the HATT maintains a constant rotational velocity, its hydrodynamic loads will fluctuate with the 6-DOF motion of the supporting structure. Consequently, to ensure the stable and safe operation of the FHATPD, the rotational speed of the HATT can be controlled. The purpose of rotational speed control is to enable the HATT to operate at its stated power rating. First, the power coefficient is calculated for different tip speed ratios using the established computational fluid dynamics (CFD) method for the surging motion and variable-speed rotation of the HATT. Subsequently, a rotational speed prediction model is established based on a multilayer perceptron (MLP), and the prediction results are verified by a CFD-based method. The training of the MLP model is improved by adjusting the feature parameters, supplementing the training data, and smoothing the mutation curves. Finally, the rotational speed prediction model of the HATT operating at rated power is obtained. These results can be a valuable reference for the FHATPD's operational stability and efficiency.