Fault-Tolerant Control for a Wave Energy Converter by Damping Injection

This work presents an active fault-tolerant control (FTC) scheme by damping injection for a wave energy converter (WEC). The case study is an Archimedes wave swing-based WEC, where two braking subsystems for the floater play a critical role in protecting the physical structure from extreme sea conditions. In order to obtain fault-tolerant behavior in the presence of faults in the brakes, the deviation of the damping force is compensated through the force produced by the linear generator, which is controlled to maximize the energy conversion in nominal conditions. For this purpose, the force deviation is estimated from a fault detection and isolation (FDI) module by using an Utkin-based unknown input observer, which is then used for the compensation that completes the FTC. The proposed system is tested by numerical simulation under different scenarios, including faults in the damping system and others. The results demonstrate the capabilities and limitations of the proposal, which achieves the established objective. The performances of the nominal control and the proposed FTC are compared.