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Design and Control of a Floating Wave-Energy Converter Utilizing a Permanent Magnet Linear Generator.

机译：利用永磁线性发电机的浮动波能转换器的设计和控制。

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摘要

This thesis considers the design, optimization, and control of a coupled cylindrical floater and permanent magnet linear generator for wave-energy conversion. The investigation begins with the construction of the time-domain equation of motion for a generic floating body. The construction of a physical cylindrical floater is followed by a description of the experiments completed to verify free-motion and wave-exciting force predictions. The time-domain equation of motion was compared against experiments where it was found that corrective terms needed to be added due to the presence of viscosity. Initial low motion amplitudes lead to evaluation of the hydrodynamic performance between a floater with a flat and rounded-hemispherical bottom. Experimental results demonstrated that motion amplitudes can be over predicted by a factor of 2 when neglecting the effects of viscosity.;Second, modifications to the design, fabrication process, and material of a permanent magnet linear generator (PMLG) will be discussed with the aim of increasing both power output and mechanical-to-electrical conversion efficiency. In order to evaluate the performance of the power-take-off unit a dry-bench test was completed which consisted of driving the armature of the PMLG at various frequencies with a fixed motion amplitude. The force signature from the bench test was used to extract the spring, damping, and inertia force coefficients due to the influence of the PMLG. The force coefficients were obtained for various speeds, resistive loads, and magnet coil gap widths. The floater equation of motion was modified to accommodate the influence of the PMLG to predict the coupled system performance. As the damping coefficient was the dominant contribution to the PMLG reaction force, the optimum non time-varying damping values were presented for all frequencies, recovering the well known impedance matching at the coupled resonance frequency. Model-scale tests of the coupled floater-generator system were performed at the UC-Berkeley Model Testing Facility to verify the optimum conditions for energy extraction.;In an effort to further maximize power absorption, nonlinear model predictive control (NMPC) was applied to the model-scale point absorber. The NMPC strategy was set up as a nonlinear optimization problem utilizing the Interior Point OPTimizer (IPOPT) package to obtain the optimal time-varying generator damping from the PMLG. This was accompanied by a latching damper that was allowed to periodically slow the floater velocity in an effort to increase power absorption. The emphasis on this work has been on sub-optimal strategies that limit the power-take-off unit to behave as a generator, thereby minimizing energy return to the waves. It was found that the ideal NMPC strategy required a PTO unit that could be turned on and off instantaneously, leading to sequences where the generator would be inactive for up to 60% of the wave period. Experimental validation of the NMPC included repeating the dry bench test in order to characterize the time-varying performance of the PMLG. This was achieved through the use of mechanical relays to control when the electromagnetic conversion process would be active. After the time-varying performance of the PMLG was characterized the experimental set-up was transferred to the wave tank. The on/off sequencing of the PMLG was tested under regular and irregular wave excitation to validate NMPC simulations using the control inputs obtained from running the controller offline. Experimental results indicate that successful implementation was achieved and the absorbed power was indeed maximized.
机译：本文考虑了耦合波型浮子和永磁直线发电机用于波能转换的设计，优化和控制。研究从构造通用浮体的时域运动方程开始。物理圆柱浮子的构造后，将描述为验证自由运动和激波力预测而完成的实验。将时域运动方程与实验进行比较，发现由于粘度的存在，需要添加校正项。初始的低运动幅度导致对平底和圆形半球形底部的浮子之间的水动力性能进行评估。实验结果表明，在忽略黏度影响的情况下，运动幅度可以被高估2倍;其次，将针对永磁直线发电机（PMLG）的设计，制造工艺和材料进行修改增加功率输出和机电转换效率。为了评估取力器的性能，完成了干式试验，该试验包括以固定的运动幅度以各种频率驱动PMLG的电枢。由于PMLG的影响，台架试验中的力特征被用于提取弹簧，阻尼和惯性力系数。获得了各种速度，电阻负载和电磁线圈间隙宽度的力系数。修改了浮动的运动方程，以适应PMLG的影响，从而预测耦合系统的性能。由于阻尼系数是对PMLG反作用力的主要贡献，因此为所有频率提供了最佳的随时间变化的阻尼值，从而恢复了在耦合谐振频率下众所周知的阻抗匹配。在UC-Berkeley模型测试设施上对耦合式漂浮发电机系统进行了模型规模测试，以验证能量提取的最佳条件。为了进一步最大化功率吸收，非线性模型预测控制（NMPC）被应用于模型级点吸收器。使用内部点OPTimizer（IPOPT）软件包将NMPC策略设置为非线性优化问题，以便从PMLG获得最佳时变发电机阻尼。伴随有一个闩锁阻尼器，该阻尼器允许定期降低浮子速度，以增加功率吸收。这项工作的重点一直放在次优策略上，这些策略限制了取力器充当发电机的作用，从而最大程度地减少了回波的能量。结果发现，理想的NMPC策略需要一个可以立即打开和关闭的PTO单元，从而导致在多达60％的波浪周期内，发生器将处于非活动状态。 NMPC的实验验证包括重复进行干式试验，以表征PMLG随时间变化的性能。这是通过使用机械继电器来控制何时启动电磁转换过程来实现的。在表征了PMLG随时间变化的性能之后，将实验装置转移到波箱中。在规则和不规则波激励下测试了PMLG的开/关序列，以使用从离线运行控制器获得的控制输入来验证NMPC仿真。实验结果表明，成功实现了该技术，并且吸收功率的确得到了最大化。

著录项

  • 作者

    Tom, Nathan Michael.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Engineering Marine and Ocean.;Engineering Mechanical.;Energy.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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