An Oscillating Wave Energy Converter with Nonlinear Snap-Through Power-Take-Off Systems in Regular Waves

• Published in: China ocean engineering Vol. 30; no. 4; pp. 565 - 580
• Main Author: 张显涛 杨建民 肖龙飞
• Format: Journal Article
• Language: English
• Published: Nanjing Chinese Ocean Engineering Society 01.07.2016; State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
• Subjects: Coastal Sciences; Engineering; Fluid- and Aerodynamics; Marine & Freshwater Sciences; Numerical and Computational Physics; Oceanography; Offshore Engineering; Simulation; 单元; 振动波; 状态空间模型; 能量变换器; 能量转换器; 规则波; 非线性动力系统; 非线性参数; power-take-off; snap-through; state space; wave energy; dynamic response; time domain equation; power-take-off,snap-through
• ISSN: 0890-5487; 2191-8945
• DOI: 10.1007/s13344-016-0035-5

Floating oscillating bodies constitute a large class of wave energy converters, especially for offshore deployment. Usually the Power-Take-Off（PTO） system is a directly linear electric generator or a hydraulic motor that drives an electric generator. The PTO system is simplified as a linear spring and a linear damper. However the conversion is less powerful with wave periods off resonance. Thus, a nonlinear snap-through mechanism with two symmetrically oblique springs and a linear damper is applied in the PTO system. The nonlinear snap-through mechanism is characteristics of negative stiffness and double-well potential. An important nonlinear parameter γ is defined as the ratio of half of the horizontal distance between the two springs to the original length of both springs. Time domain method is applied to the dynamics of wave energy converter in regular waves. And the state space model is used to replace the convolution terms in the time domain equation. The results show that the energy harvested by the nonlinear PTO system is larger than that by linear system for low frequency input. While the power captured by nonlinear converters is slightly smaller than that by linear converters for high frequency input. The wave amplitude, damping coefficient of PTO systems and the nonlinear parameter γ affect power capture performance of nonlinear converters. The oscillation of nonlinear wave energy converters may be local or periodically inter well for certain values of the incident wave frequency and the nonlinear parameter γ, which is different from linear converters characteristics of sinusoidal response in regular waves.