Direct-drive wave energy converter (WEC) and buoy control algorithms have shown great potential for renewable wave energy extraction in ideal conditions. However the actual power take-off (PTO) impacts are barely considered in the WEC design. This paper highlights the demands of designing the WEC wave-to-wire control from a global point of view by studying the actual PTO impacts. A permanent magnet linear electrical machine (LEM) PTO unit is simulated and controlled to fulfill the WEC buoy control requirements. Several state of the art control algorithms, which include singular-arc (SA) control, shape-based (SB) control, model predictive control (MPC), and proportional-derivative (PD) control, are applied to maximize the wave energy production (mechanical energy). Multiple types of electrical PTOs, including ideal PTO, unlimited PTO and limited PTO, are all implemented to evaluate WEC wave-to-wire performances. Further, the PTO copper loss model and the PTO actual efficiency maps are introduced and studied to improve the electrical PTO operation efficiency. To further assess the control schemes in various wave conditions, one-year PacWave ground-truth data is applied as well. Numerical simulations are conducted using MATLAB/Simulink and the Simscape toolbox. The electrical PTO unit is composed of a LEM, an ideal inverter, and an ideal energy storage system. The results show that the actual PTO will impact the constrained controls (MPC and SB) less comapring to unconstrained controls (SA and PD). Although SB can produce the maximum energy with the limited PTOs, it is not robust for all wave conditions. At the end of the paper, the possible solutions for improving the WEC wave-to-wire performances are also provided.

中文翻译：

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利用波线建模评估波浪能转换器的发电量


直接驱动波浪能转换器（WEC）和浮标控制算法在理想条件下显示出可再生波浪能提取的巨大潜力。然而，WEC 设计中几乎没有考虑实际取力器 (PTO) 的影响。本文通过研究实际的 PTO 影响，强调了从全局角度设计 WEC 波线控制的需求。对永磁线性电机 (LEM) PTO 装置进行仿真和控制，以满足 WEC 浮标控制要求。应用多种最先进的控制算法，包括奇异弧 (SA) 控制、基于形状 (SB) 控制、模型预测控制 (MPC) 和比例微分 (PD) 控制，以最大限度地提高波浪能产量（机械能）。多种类型的电动取力器（包括理想取力器、无限取力器和有限取力器）均用于评估 WEC 波对线性能。进一步介绍和研究了PTO铜损模型和PTO实际效率图，以提高电力PTO运行效率。为了进一步评估各种波浪条件下的控制方案，还应用了一年的 PacWave 地面实况数据。使用 MATLAB/Simulink 和 Simscape 工具箱进行数值模拟。电气PTO单元由LEM、理想逆变器和理想储能系统组成。结果表明，与无约束控制（SA 和 PD）相比，实际 PTO 对约束控制（MPC 和 SB）的影响较小。尽管 SB 可以利用有限的 PTO 产生最大能量，但它并不适合所有波浪条件。论文最后还提供了提高WEC波线性能的可能解决方案。