Health-aware control augmentation for wave energy converters using a reliability metric

Wave energy is free, but conversion to electricity comes at a price; control technology is often viewed as an effective way to reduce the conversion cost. Nevertheless, traditional energy-maximising controllers for wave energy converters (WECs) often exaggerate device motion, which can shorten device longevity and increase operational expenses (OpEx), by increasing the number of maintenance intervals. This paper proposes a novel health-aware WEC control structure to achieve a suitable trade-off between energy maximisation and power take-off (PTO) lifetime enhancement, ultimately leading to a lower levelised cost of energy (LCoE). The proposed control structure, in contrast to conventional energy-maximising WEC control structures, utilises previous control input information to achieve a trade-off between energy maximisation and PTO lifetime enhancement objectives. Due to the learning strategy from past control information, the need to redesign the nominal (energy-maximising WEC) controller can be avoided when designing a health-aware control law (i.e., the method is nominal controller-independent), resulting in a simple and effective control algorithm, thereby saving computational resources. Simulation results demonstrate the effectiveness of the proposed controller in achieving a trade-off between captured energy and PTO lifetime.