A Simple and Effective Real-Time Controller for Wave Energy Converters

Abstract

Abstract-A novel strategy for the real-time control of oscillating wave energy converters (WECs) is proposed. The controller tunes the oscillation of the system such that it is always in phase with the wave excitation force and the amplitude of the oscillation is within given constraints. Based on a nonstationary, harmonic approximation of the wave excitation force, the controller is easily tuned in real-time for performance and constraints handling, through one single parameter of direct physical meaning. The effectiveness of the proposed solution is assessed for a heaving system in one degree of freedom, in a variety of irregular (simulated and real) wave conditions. A performance close to reactive control and to model predictive control is achieved. Additional benefits in terms of simplicity and robustness are obtained.

The Effect of Viscosity on the Maximisation of Electrical Power from a Wave Energy Converter under Predictive Control

“…Classical control methods such as reactive control, (Budal and Falnes, 1977) and latching, (Budal and Falnes, 1980) have been used to extract maximum or close to maximum average power. The effect of system constraints have been investigated, (Fusco and Ringwood, 2013) as well as the use of a realistic non-ideal Power Take Off (PTO), (Tedeschi et al, 2011). Both latching and reactive control were originally designed to operate in monochromatic seas, however, there have been attempts to extend their use for irregular sea conditions, (Fusco and Ringwood, 2011;Babarit et al, 2004).…”

Control, forecasting and optimisation for wave energy conversion

“…The simple controller, when compared with a model predictive controller (MPC) in both wide-and narrow-banded seas, has a relative capture with within about 10% of the MPC, but has superior robustness to variations in K b . Further details on this controller are given in (Fusco and Ringwood, 2013).…”

“…While some WEC control algorithms circumvent the need to predict future variations in free surface elevation or excitation force (Fusco and Ringwood, 2013;Scruggs et al, 2013), in general there is a need to provide forecast values of free surface elevation or excitation force due to the non-causality of the optimal PTO force, as articulated in Section 4. Fortunately, there is a strong positive connection between the wave forecasting requirements of energy maximising control (Fusco and Ringwood, 2012) and the forecastability of random seas , due to the close relationship between the radiation damping dynamics and the design sea state (i.e.…”

A Self-zeroing position controller for oscillating surge wave energy converters with strong asymmetry

“…As a result, peak loads are normally greater than in continuous cases (Babarit and Clément 2006;Folley and Whittaker 2009;Babarit et al 2009;Clément and Babarit 2012). Also included are controllers such as the 'Simple and Effective Controller ' Fusco and Ringwood (2013) which use similar approaches to MPC or complex-conjugate control but make assumptions or simplifications in order to implement them in real time.…”