Multiple Freedom Interacted Influence on the Power Conversion for Mushroom Wave Energy Converter

Nowadays, the design of wave energy converter (WEC) has become a research hotspot of new energy development and utilization. The motion form of traditional WEC is usually in the single degree of freedom model. In order to efficiently utilize wave energy, a multi-degree-of-freedom interactive wave energy converter, namely Mushroom WEC, is proposed in this paper. The device is mainly composed of a spar hinged to the bottom of the sea for pitch motion and a buoy tied to the spar for heave motion along the direction of the spar, which can absorb the potential energy and kinetic energy of the wave at the same time. In this paper, a mathematical motion model is established according to the motion characteristics of the device, and an analytical method based on linear wave theory is used to solve the wave excitation force and hydrodynamic coefficient. Moreover, by introducing two independent PTO systems and using numerical methods to solve the coupled nonlinear equations of motion, the coupled motion effect and power generation performance of Mushroom WEC spar and buoy were analyzed. The result showed that the power generation efficiency of Mushroom WEC is better than that of the traditional single-degree-of-freedom wave energy converter, and the frequency response range of the device can be improved. The research in this paper is of referential significance to the research of wave energy converter moving with multiple degrees of freedom.