Impact of turbine operation modes on energy conversion in oscillating water column wave energy converter

The oscillating water column (OWC) wave energy conversion technology has been widely adopted in ocean energy applications, yet its energy capture efficiency requires further improvement. Previous studies have not fully elucidated the transient interactions between the turbine and OWC or their impact on system efficiency. This study innovatively introduces a maximum power point tracking (MPPT)-based dynamic control strategy into a coupled wave–air chamber–turbine numerical model, revealing the transient coupling mechanism between variable-speed impulse turbines and the OWC chamber. A viscous computational fluid dynamics (CFD) numerical model was developed to investigate the performance of three turbine operation modes—free-speed, fixed-speed, and dynamic-speed—focusing on their effects on turbine aerodynamics and internal air dynamics in the OWC chamber. Simulations were carried out under regular waves with a fixed height of 0.1 m and periods from 1.8 to 3.4 s. Results indicate that while the free-speed mode simplifies system structure, it yields the lowest overall efficiency. The peak efficiency of the fixed-speed mode is constrained by specific operating conditions. In contrast, the MPPT-based dynamic-speed mode enhances energy capture efficiency by 4.97% and 24.07% compared to fixed-speed and free-speed modes. However, turbulent inertia effects during turbine transient operation reduced secondary efficiency by 15% relative to steady-state theoretical values. This study demonstrates that dynamic control with real-time flow coefficient feedback can effectively synchronize air chamber energy capture with turbine power output, providing both a theoretical foundation and an optimization framework for developing intelligent control systems in wave energy plants.