Robust control of wave energy converters

Abstract

Abstract-Energy-maximising controllers for wave energy devices are normally based on linear hydrodynamic device models. Such models ignore nonlinear effects which typically manifest themselves for large device motion (typical in this application) and may also include other modelling errors. In this paper, we present a methodology for reducing the sensitivity to modelling errors and nonlinear effects by the use of a hierarchical robust controller, which also allows good energy maximisation to be recovered through a passivity-based control approach.

A review of wave energy technology from a research and commercial perspective

“…Since WSI is somewhat of a 'blackbox', modelling error and uncertainty are inevitable. Thus, control strategies have been designed to address the robustness to: modelling error [80,[179][180][181][182][183], external disturbance [184][185][186], and estimation/prediction error of excitation force [187]. Model sensitivity issue for different WEC control system architectures is analytically and numerically studied in [172], revealing that the AVT architecture is relatively insensitive to inertial and stiffness terms, and generally has superior robustness compared with the ACC framework [172].…”

Recent Findings on Strong Integral Input-to-State Stability for Forced Lur'e Systems

“…In terms of scope of results, there is overlap with the present work and others including the author, namely [32,33,34]. The key novelty and contribution of the present work is technical, yet is important, and is that the nonlinearities considered here may belong to an infinite sector, such as "superlinear" nonlinearities F (z) = ±z|z| d (sign depending on feedback convention used) which find relevance in a wave-energy applications perspective [29]. The works [32,33,34] all impose linear boundedness of the nonlinearity (in other words, a finite-sector condition is imposed, and this structure is essential).…”

A spectral-domain wave-to-wire model of wave energy converters

“…As a control parameter, PTO damping plays an important role in the power performance of WECs. Even though a number of real-time control algorithms have been proposed and applied for WECs in recent years (Wang and Isberg, 2015;Garcia-Rosa et al, 2017;Fusco and Ringwood, 2011;Anderlini et al, 2017). With regard to the early-stage design of WECs, it is significant to search for a constant PTO damping for maximizing the power production in each wave state since it is associated with lower complexity and could also effectively reflect the potential of the device.…”