Abstract:As a kind of energy, wave energy in ocean is a renewable energy with the characteristics of widespread, abundant and highly energy flux density. But it’s hard to extract energy from incident wave which is random, unstable with big variance of power input. Wave energy converter (WEC) is a device designed to capture the wave power. Recently much more attention is paid to oscillate WEC (point absorber wave energy capture device) for its flexible, low cost and easy deployment. In particular, the efficiency of oscillating WEC can be significantly increased by motion control. Some investigations show that an optimal control strategy can be designed to alter the oscillator dynamics. As a result, the efficient energy conversion will occur over a wide range of wave conditions. This point of view is also verified by some practical application such as latching control. Study also shows that short term wave prediction is essential for reactive control. However, the fact of prediction time horizon is still unclear. In this paper, the prediction effect is described mathematically based on hydrodynamic theory. Furthermore, a simulation study is also performed to show the increasing of energy capture by the effect of wave prediction, and the problem of this study is analyzed. Finally, an economical prediction time horizon is proposed considering costs and benefits and a more insightful understanding of WEC optimal control is obtained by this paper.