Thesis
Control co-design of wave energy converters
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T18144
- Person Identifier (Local)
- 202183088
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- A novel optimisation model is presented that uses a control co-design (CCD) methodology to optimise the power take-off (PTO) and floater design of wave energy converters (WECs). The model is used to investigate the importance of applying a CCD methodology to WEC design. CCD is a design philosophy that integrates the design stages of the physical device and controller to create a more effective overall design. Conventional design methodologies leave the controller design until after device design has been finalised; opening the possibility that the locked-in WEC design can cause difficulties for the subsequent controller design. If the two stages are integrated – as a part of CCD – the conflict could be corrected before the design is finalised. The PTO uses a permanent magnet synchronous generator (PMSG) that is simulated using a lumped parameter model to estimate electromechanical losses within the drive train giving the output electrical power as a function of input mechanical force and speed. By using a genetic algorithm, the design of the PMSG (number of pole pairs, depth of magnets, rotor radius, etc.) is optimised to a user-selected control strategy, floater design, and wave climate. Candidate PMSG designs are tested in a suite of monochromatic-sea-state power simulations. Sea states are selected from historical wave data with the test sample found using a k-means clustering algorithm. The number of sea states required for a well-optimised design is investigated: finding that 20 sea states is the point of negligible improvement. First the PMSG is optimised alone, to investigate differences when varying between: linear damping and impedance matching control; narrow- and broad-banded floaters; and a low-, medium-, and high-energy site. Results show that the optimal design is significantly different in each of the three investigations. Devices that can operate more effectively away from resonance tend to be larger in size and can extract more power. Devices that operate less effectively away from resonance perform better when smaller and cheaper, even at the cost of reduced electrical output: it is found that when using LD control material cost of the generator can be reduced by 60% with only a 5% reduction in electrical power output. Then the model is then expanded to allow for Froude scaling of the floater: facilitating the novel co-optimisation of PTO design and floater scale. The comparison of performance of WECs designed with: PTO optimisation only; serial optimisation of PTO and floater scale; and co-optimisation of PTO and floater scale finds improved performance with a more integrated design process, further supporting the case of utilising CCD methodologies. It is found that co-optimisation of PTO and floater can lead to an up to 90% increase in electrical power output when compared to PTO optimisation alone. Finally, the PTO designs are tested in a polychromatic-sea-state power simulation. Optimised designs outperform the non-optimised designs: showing that the monochromatic approximation is capturing an intrinsic property of the waves.
- Advisor / supervisor
- Campos-Gaona, David
- Resource Type
- DOI
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PDF of thesis T18144 | 2026-09-29 | Public | Download |