Control of the stalling behaviour in wave power generation plants

In this paper the performance of the Wells turbine has been improved, studying its stalling behaviour when the flow coefficient (phy) reaches a specific characteristic value. For this purpose, a control scheme for the flow coefficient is derived based on the addition of external resistances in series with the rotor winding of the induction generator connected to the turbine. Due to the stalling behaviour, the generator increases its velocity as the flow coefficient of the turbine approaches the critical point at which the turbine losses power. The proposed control system does appropriately adapt the rotor resistance according to the entry pressure drop. To do so, the control implements a continuous resistance switching depending on the pressure drop and it will be demonstrated that the proposed control method used for this purpose clearly improves the performance of the system, maximizing the power generated by the turbine.