Optimum wave energy conversion of a point absorber with direct electrical power take-off

This paper refers to the passive and reactive control of power-take-off (PTO) systems involved in wave energy conversion. A point-absorber device (buoy) is considered. After a brief introduction of the principles of marine wave-buoy interaction, the passive and reactive controls of the PTO systems are recalled. For each control strategy, the analytical relations for maximizing the power extracted by the wave and the electrical power provided by an active-controlled electrical PTO are defined and verified by simulation. Then, an experimental set-up of a small-scale laboratory simulator of the wave energy conversion system is also implemented. Two vector-controlled PM synchronous machines joined without mechanical backlash are used, one to simulate the wave excitation force and the other the PTO engine. The experimental tests confirm the possibility to extract maximum power by proper setting of the control parameters.