Power Smoothing and Limitation Control of a PMSG-Based Marine Current Turbine under Swell Waves

Variations of marine current speed can lead to strong fluctuations in the power extracted by a marine current turbine (MCT). During short-time period, swell effect is the main cause for the current speed variations. Conventional tip speed ratio Maximum Power Point Tracking (MPPT) algorithm will require the MCT to accelerate or to decelerate frequently under swell effect, which can cause severe fluctuations in the generator power. This paper focuses on power smoothing control of a PMSG-Based MCT system. A modified MPPT algorithm with filter strategy is proposed in generatorside control to use the system inertia for smoothing the fluctuation of generator power. When the current speed is over rated value, the power limitation control will be applied. A robust feedback flux-weakening control algorithm is studied for a fixed pitch PMSG-based MCT; both speed loop and torque loop control strategies are simulated and compared to show the power limitation control effects at high marine current speeds.