ON THE CONTROL OF WAVE ENERGY DEVICES IN MULTIFREQUENCY WAVES

This paper presents a method for controlling a wave energy device to ensure high performances in random seas. The method is developed theoretically and a design proposed and analysed for an oscillating water column device. A PID (proportional integral differential) circuit and a digital filter are used in the feedback to drive a DC linear motor, maintaining zero phase shift between the wave excitation force and the velocity of the moving part of the device for nonharmonic motions. A practical design is worked out for a model oscillating water column and it is shown that the energy spent in achieving control can be made considerably less than that gained through control.