WEC fault modelling and condition monitoring: A graph‐theoretic approach

Abstract

The nature of wave resources usually requires wave energy converter (WEC) components to handle peak loads (i.e., torques, forces, and powers) that are many times greater than their average loads, accelerating equipment degradation. Moreover, due to their isolated nature and harsh operating environment, WEC systems are projected to possess high operations and maintenance (O&M) cost, i.e., around 27% of their leveled cost of energy. As such, developing techniques to mitigate these costs through the application of condition monitoring and fault tolerant control will significantly impact the economic feasibility of grid connected WEC power. Toward this goal, models of faulty components are developed in the open source modeling platform, WEC-Sim, to estimate the performance and measurable states of a WEC operating with likely device and sensor failures. Two types of faulty component models are then applied to a point absorber WEC model with basic controller damping and spring forces. Resulting changes in device behavior are recorded as a benchmark, and a graph-theoretic approach is proposed for fault detection and identification utilizing multivariate time series. Simulation results demonstrate that these faults can greatly affect the WEC performance, and that the proposed method can effectively detect and classify different types of faults.

The Wave Energy Converter Control Competition (WECCCOMP): Wave Energy Control Algorithms Compared in Both Simulation and Tank Testing

“…As a benchmark problem itself, the WECCCOMP system has, to date, had some moderate success in promoting both simulation-based (Tang et al, 2020;Guerrero-Fernández et al, 2022) and experimental (García-Violini et al, 2021;Faedo et al, 2023;García-Violini et al, 2023) assessment of WEC controllers. We hope that the WECCCOMP benchmark will continue to be of service to the wave energy community: Online resources for simulation are maintained by Sandia/NREL (see WECCCOMPGithub (2018)) and the WECCCOMP organisers would be delighted to receive feedback and comments regarding WECCCOMP, and possible future benchmark competitions.…”

Review of WEC-Sim development and applications

“…Their results show more significant fatigue damage in shallow water due to higher umbilical curvature, and low fatigue damage when an umbilical is perpendicular to the incoming wave. Tang et al investigated the effect of WEC component faults using WEC-Sim [78]. The authors implemented four electrical and three mechanical fault models into WEC-Sim constraint and PTO blocks.…”

Flap-type wave energy converters: From accelerated testing to fault detection

“…This function essentially encapsulates the different sources of damping characterizing a friction torque in the hinge (Tang et al 2020). The main parameters are the friction torque T, the angular vel-_ ocity θ, for which the subscript of b, c, and st stands for breakaway, Coulomb, and Stribeck.…”

“…Faults in complex systems such as Wave Energy Converters (WEC) are inevitable, and the harsh environment in which it operates hinders the accessibility of the device for maintenance activities and increases the associated costs (Tang et al 2020). The major part of the energy cost for WECs is related to the inspection and maintenance cost (Ambuehl, Kramer, and Sørensen 2016).…”