A Sensitivity Analysis of Wave Energy Converter Model Predictive Control Systems With Wave Excitation Force Estimation and Prediction

Abstract

Understanding the sensitivity of energy-maximizing control for wave energy converters (WECs), to various model errors, is crucial for application. Many advanced WEC controllers, especially model predictive control (MPC)-like controllers, require estimation and prediction of wave excitation force (WEF). However, previous studies only focus on the controller in isolation, without considering the error coupling effects when a complete estimation-prediction loop is involved. In this study, it is revealed through numerical analysis that the complete MPC system has sensitivity behavior completely different from the isolated MPC; under certain model errors, the system can become particularly unpredictable, exhibiting potential instability and self-locking phenomena, which cannot be observed from the examination of control sensitivity alone. Meanwhile, different tuning options for the WEF estimator and predictor are examined, where the accuracy-robustness tradeoff is shown to be critical for performance amelioration under errors. Based on the analysis, this study challenges the widely assumed “separation principle” of WEF estimation/prediction and WEC control, highlights the importance of incorporating a complete estimation-prediction loop in sensitivity examination, and draws practical guidelines for WEC control application.