An Improved Variable-Speed Control Strategy for Air Turbine of Floating Oscillating Water Column Wave Energy Converter

This study proposes an improved variable-speed control strategy for Wells turbines in floating oscillating water column (OWC) wave energy converters (WECs) to address efficiency loss caused by turbine stalling. By optimizing the ϕ from the conventional critical value from 0.3 to 0.11, the system achieves maximum mechanical power output while avoiding stall effects. A dynamic rotor-speed controller is designed to modulate turbine rotation behavior in response to real-time airflow velocity. This approach is validated using numerical simulations and MATLAB/Simulink R2021b models under both regular and irregular wave conditions. Results show a 124% increase in turbine power compared to uncontrolled operation, with stable DC-link voltage (+0.2%) and reduce torque ripple. The strategy enhances energy conversion efficiency by 51.2% and ensures safe operation under mechanical speed limits (3000 rpm), thus offering a practical solution for offshore WEC systems.