12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Linear and nonlinear control of a power take-of...
View graph of relations

« Back

Linear and nonlinear control of a power take-off simulation for wave energy conversion.

Research output: Contribution in Book/Report/ProceedingsConference contribution

Published

Publication date2009
Host publication8th European Wave and Tidal Energy Conference
Original languageEnglish

Conference

Conference8th European Wave and Tidal Energy Conference
CityUppsala, Sweden
Period7/09/0910/09/09

Conference

Conference8th European Wave and Tidal Energy Conference
CityUppsala, Sweden
Period7/09/0910/09/09

Abstract

This article focuses on control of the power take off (PTO) element of a point absorber wave energy converter. The research is based on a nonlinear simulation of a PTO hydraulic circuit, in which the piston velocity and generator torque act as `disturbance' and control actuator variables respectively, whilst the damping force is the controlled output variable. The piston velocity is generated by a hydrodynamic simulation model that reacts to both the damping force and sea wave profile. The damping force set point will be obtained from an associated power capture optimisation module and may be time varying. However, it is clear that such an adaptive tuning system also requires high performance `low-level' control of the device actuators, in order to fully realise the benefits of optimisation. In this regard, the present article illustrates use of the Proportional-Integral-Plus (PIP) control methodology as applied to the PTO simulation. In their simplest linear form, such PIP controllers do not account for the interconnected system variables mentioned above. For this reason, the research also considers `feed-forward' and `state-dependent' forms of PIP control, in which the piston velocity is appended to a non-minimal state space representation of the system.