Fault diagnosis and fault-tolerant control in wave energy: A perspective

In the decarbonisation path, wave energy systems are gaining attention as a key technology in the renewable energy mix. An essential step towards their effective development is constituted by energy -maximising, optimal control algorithms, which in wave energy systems can maximise energy extraction while respecting system physical constraints. Current strategies rely on mathematical models describing, in a parsimonious yet sufficiently exhaustive fashion, the device dynamics. Notwithstanding, wave energy converters operate in severe environments where extreme wave events and sea corrosion can lead to malfunctions, compromising their reliability. As a damage consequence, the system dynamics can change, entailing structural ambiguity in the nominal model. This uncertainty significantly degrades optimal control performance, potentially compromising the system's health and leading to expensive maintenance costs. Fault diagnosis and faulttolerant control algorithms are designed to identify and accommodate eventual faults in dynamic systems. As such, they are powerful tools for implementing wave energy resilience features, thus minimising idle device time and extra maintenance operations. This work presents a critical analysis of the status of fault diagnosis and fault -tolerant control in wave energy, starting from parallelism with the sister wind energy field, for which they are substantially more mature. Such tools are put in the wave energy -maximising context, presenting a study of the weak and strong points in the current literature, while proposing potential solutions for the identified pitfalls, and highlighting what is missing to pin fault diagnosis and fault -tolerant control as a silver bullet for improved reliability within the wave energy control field.