Fuzzy logic control of OWC wave energy plant for preventing wells turbine stalling

This paper proposes a fuzzy logic controller (FLC) for oscillating water column (OWC) wave energy plant in order to prevent the Wells turbine stalling. The stalling phenomenon decreases turbine efficiency when subjected to high airflow rate inside the OWC. Thus, the turbine needs to be operated within the permissible flow coefficient range so as to obtain maximum energy from the plant. The turbine is coupled to a wound rotor induction generator (WRIG) in series with externally connected rotor resistances. An adequate control scheme is required for choosing rotor resistance values which in turn will change the rotor slip. The FLC scheme with mean airflow velocity as input and resistance values as output has been designed. The fuzzy rules have been defined based on input-output data. The input-output data of the controller is obtained by numerical analysis of the plant for a predefined range of turbine flow coefficient and regular waves. The performance of proposed controller is demonstrated under regular and irregular sea wave conditions.