A Multi-Stage Design Approach for Optimizing a PMSG-Based Grid-Connected Ocean Wave Energy Conversion System

Fully harnessing the ocean wave's renewable energy resources could benefit coastal countries. However, ocean wave energy harvesting systems encounter several challenges, i.e., marine uncertainties, long-distance mainte-nance, power fluctuations, irregular wave currents, non-linear generator dynamics, turbine limitations, cost optimization, and power smoothing issues. To overcome these challenges, this paper proposes a new multi-stage con-trol design approach for performance evaluation of the os-cillating water column (OWC)-based ocean wave energy conversion (OWEC) system. The first stage optimizes the Wells turbine by implementing an efficient airflow control strategy. It achieves maximum power-harvesting ability by eliminating stalling phenomena. In the second stage, we investigate the robustness of the permanent magnet syn-chronous generator-based OWEC system by designing adaptive back-stepping controllers, taking into account the Lyapunov stability theory. It accomplishes precise speed regulation for optimal power extraction while delivering reduced delay response and percentage errors. To ensure the OWEC system's availability, the third stage incorporates fault-ride-through capabilities. It executes a fault reconfig-urable control for a parallel converter configuration, elimi-nating only the faulty leg instead of the entire power con-verter. In the fourth stage, a supercapacitors-based energy management system achieves power smoothing, even when the OWC plant output power fluctuates. We accomplish this by implementing a model predictive control strategy. Finally, the Matlab/Simulink results verify that the presented mul-ti-stage control for the OWC OWEC system is an effective design approach, offering an optimal, robust, reliable, and power-smoothing solution.