In this work, the modeling of a Power Take-
Off (PTO) unit for a point absorber wave
energy converter is described. The PTO
influences the energy conversion performance
by its efficiency and by the damping force
exerted, which affects the motion of the body.
The state space model presented gives a
description of the damping force and of the
internal dynamics of the PTO. The aim of this
work is to develop a model for the PTO as a
part of a complete wave-to-wire model of a
wave energy converter as in Figure 1, used for
the design control techniques.
Figure 1: Wave-to-wire model structure
A bondgraph is employed to model the
physical system that provides transparent and
methodical means of formulating state space
equations and of visualizing energy transfer
throughout the system. Bondgraphs have
already been shown to be a very useful tool for
the modeling of PTO for wave energy
converters (2). The dynamic of the
mathematical model is then analyzed respect to
the variation of parameters; in particular, the
non-linear system obtained is linearized and its
eigenvalues are calculated as function of the
accumulator size and pre-charge pressur
