Control Framework Design for WECs with Direct Drive Linear Generator-Based Power Take Off Systems

Ocean wave energy conversion has attained significant research interest due to its vast untapped potential, offering promising solutions for powering Blue Economy (PBE) applications in remote maritime locations where traditional grid connections are impractical or cost prohibitive. However, the efficient and reliable conversion of ocean wave energy remains challenging due to the variability of ocean conditions, the complexities of energy conversion processes, and the need for robust control to ensure stable and consistent power output. The complex and nonlinear behavior of ocean waves further necessitates the use of nonlinear control strategies to maximize energy capture, reduce cost and maintain reliable system performance. This study introduces a comprehensive control framework for Wave Energy Converter (WEC) and Permanent magnet linear synchronous generator (PMLSG) based Power Take-Off (PTO) system, consisting of three main stages: wave energy capture, mechanical-to-electrical conversion, and electrical power conditioning. The focus is on the first-stage controller, designed to synchronize the WEC's motion with ocean waves to maximize energy extraction using Sliding Mode Control (SMC), benchmarked against Proportional-Integral (PI) control. Also, comparison has been performed with and without Control Force Limit (CFL). The energy absorbed using SMC was 9.7% higher than that achieved with PI control. The proposed SMC ensures robust performance under system nonlinearities and environmental uncertainties, enhancing the overall efficiency and reliability of WECs for PBE applications.