Representative models of the nonlinear behavior of floating platforms are essential for their successful design, especially in the emerging field of wave energy conversion where nonlinear dynamics can have substantially detrimental effects on the converter efficiency. The spar buoy, commonly used for deep-water drilling, oil and natural gas extraction and storage, as well as offshore wind and wave energy generation, is known to be prone to experience parametric resonance. In the vast majority of cases, parametric resonance is studied by means of simplified analytical models, considering only two degrees of freedom (DoFs) of archetypical geometries, while neglecting collateral complexity of ancillary systems. On the contrary, this paper implements a representative 7-DoF nonlinear hydrodynamic model of the full complexity of a realistic spar buoy wave energy converter, which is used to verify the likelihood of parametric instability, quantify the severity of the parametrically excited response and evaluate its consequences on power conversion efficiency. It is found that the numerical model agrees with expected conditions for parametric instability from simplified analytical models. The model is then used as a design tool to determine the best ballast configuration, limiting detrimental effects of parametric resonance while maximizing power conversion efficiency.

浮动平台非线性行为的代表性模型对于其成功的设计至关重要，尤其是在波动能量转换这一新兴领域，其中非线性动力学可能对转换器效率产生重大不利影响。众所周知，通常用于深水钻探，石油和天然气的提取和存储以及海上风能和波浪能发电的浮标容易发生参数共振。在绝大多数情况下，通过简化的分析模型研究参数共振，只考虑原型几何的两个自由度（DoF），而忽略了辅助系统的附带复杂性。反之，本文实现了一个具有代表性的7自由度非线性流体动力学模型，该模型具有现实的晶石浮标波能量转换器的全部复杂度，该模型用于验证参数不稳定的可能性，量化参数激励响应的严重性并评估其对功率转换的影响效率。从简化的分析模型中发现，数值模型与参数不稳定性的预期条件一致。然后将该模型用作确定最佳镇流器配置的设计工具，从而在最大化功率转换效率的同时，限制了参数谐振的有害影响。从简化的分析模型中发现，数值模型与参数不稳定性的预期条件一致。然后将该模型用作确定最佳镇流器配置的设计工具，从而在最大化功率转换效率的同时，限制了参数谐振的有害影响。从简化的分析模型中发现，数值模型与参数不稳定性的预期条件一致。然后将该模型用作确定最佳镇流器配置的设计工具，从而在最大程度地提高功率转换效率的同时，限制了参数共振的有害影响。