Adaptive Fuzzy Controller for Point Absorber Wave Energy Converter in Irregular Waves

In this work, the energy conversion from waves into electrical energy using a Point Absorber Wave Energy (PAWE) converter is modelled and controlled. The PAWE converter comprises of a hydraulic pump connected to a motor and a buoy with a generator and controller. To obtain the effect of natural irregular waves, two sinusoidal regular waves of different wavelengths and amplitudes are super-positioned. The spherical shape buoy floats on the surface of the irregular ocean waves. The buoy is connected to a Hydraulic Piston Pump (HPP) where seawater is allowed to flow into the piston pump. Due to the up and down motion of the piston pump, seawater from the piston pump drives the hydraulic motor. The generator coupled to the hydraulic motor yields electrical energy. The output of the point absorber wave energy converter can be varied by controlling the seawater flow into the hydraulic motor. In this paper, conventional PI controllers and Fuzzy gain scheduled PI controllers are developed. By varying the wavelength and amplitude of the irregular wave and the demand torque, the performances of the controllers are evaluated. On comparing the performance of the controllers, it is identified that the fuzzy gain PI controller is adaptive and provides effective control for the point absorber wave energy converter under an irregular wave environment.