Multi-resonant feedback control of a single degree-of-freedom wave energy converter
| DWPI Title: Multi-resonant single degree-of-freedom wave energy converter, has power take-off which applies control force in heave direction to buoy and harvests energy of buoy motion |
| Abstract: A multi-resonant wide band controller decomposes the wave energy converter control problem into sub-problems; an independent single-frequency controller is used for each sub-problem. Thus, each sub-problem controller can be optimized independently. The feedback control enables actual time-domain realization of multi-frequency complex conjugate control. The feedback strategy requires only measurements of the buoy position and velocity. No knowledge of excitation force, wave measurements, nor wave prediction is needed. As an example, the feedback signal processing can be carried out using Fast Fourier Transform with Hanning windows and optimization of amplitudes and phases. Given that the output signal is decomposed into individual frequencies, the implementation of the control is very simple, yet generates energy similar to the complex conjugate control. |
| Use: Multi-resonant single degree-of-freedom wave energy converter for extracting energy from waves in an open body of water, such as an ocean, a sea, or a relatively large lake. |
| Advantage: The feedback controller can take advantage of any external force to further increase the energy absorption in the same way the controller reacts to the excitation force. The wave energy converter can efficiently extract wave energy over a full range of wave frequencies and does not require prediction of the wave excitation force. |
| Novelty: The wave energy converter (100) has a buoy (102) in a water environment having wave motion. Waves (106) impacting the buoy exert an excitation force with multiple excitation frequencies that causes a buoy motion in a heave direction relative to a reference. A sensor (116) measures a position or velocity of the buoy relative to the reference for a sample period. A power take-off (110) applies a control force in the heave direction to the buoy and harvests the energy of the buoy motion. A feedback controller (114) uses a signal processor to extract frequencies, amplitudes, and phases of the measured position or velocity of the buoy, compute a proportional-derivative control for each of the extracted frequencies, amplitudes, and phases, add up each of the proportional-derivative controls to provide a computed control force, and cause the power take-off to apply the computed control force to the buoy to put the buoy heave motion in resonance with the excitation force. |
| Filed: 12/4/2017 |
| Application Number: US15830752A |
| Tech ID: SD 13535.1 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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