Output power of linear generators under reactive control in regular waves

Abstract

Direct drive wave energy converters couple a linear generator directly to a reciprocating wave energy device. This way, the performances showed by hydraulic and pneumatic based systems are improved. After linear generator, full-scale back-to-back Voltage Source Converters are used to adequate the electric energy before delivering to the grid. This stage is made up of two parts: the generator side converter stage consists of rectifying the electricity generated by the linear generator; the other one turns it in alternating current with suitable voltage and frequency parameters. The first one allows control over the instantaneous power flow possible, and in turn enables both power flow directions; this capability allows implementing reactive control. This control strategy is used to maximize the energy extraction from waves by the power takeoff (PTO) based on reaction force control. This paper shows how to determine and quantify, not the power extracted from waves, but the one transferred to the electronic converter.