Power optimisation of a point absorber wave energy converter by means of linear model predictive control

Abstract

This study presents a model predictive control (MPC) scheme for a wave energy converter (WEC); in particular, for a buoy-type point absorber. The WEC is a two-body system which is taut-moored to the sea floor with three cables. Much research has been done recently to achieve optimal operation of WECs. The goal is to maximise the power conversion without violating system limits. In practice, there are physical constraints on position, velocity and the power takeoff (PTO) force. MPC is a promising and beneficial approach to achieve this goal. It poses a control formulation including constraints in a natural way. Furthermore, MPC can exploit predictions for the sea motion a standard MPC approach always needs a reference trajectory. For one-body point absorber, an optimal velocity trajectory can be calculated. However, an optimal trajectory is not easily available for the two-body case. The proposed formulation in the presented work does not require an optimal trajectory. For this reason it is possible to apply this MPC scheme to a two-body model as well. This work demonstrates that the proposed control algorithm optimises the power extraction without violating the system constraints. Finally, the performance of MPC is compared to linear passive load control through simulation.

Electrical Power Generation from the Oceanic Wave for Sustainable Advancement in Renewable Energy Technologies

“…A damping force control technique is designed and practically verified in [72] considering the heaving motion of the float and very swift operation of the WEC. An advanced resonance control algorithm for an Archimedes wave swing based WEC is designed in [62] combining both the stiffness force and the damping force of the PTO.…”

Model Predictive Control of a Nonlinear 2-Body Point Absorber Wave Energy Converter With Estimated State Feedback

“…The details of the derivation of the state space representation can be found in [8]. Only the final model will be presented here.…”

“…Table I lists the physical parameters used in the simulations. These parameters are taken from [8] and [9], so that the same simulation environment can be used to test the estimation algorithms.…”

“…Moreover, their MPC approaches utilize an available optimal velocity trajectory which can be calculated for one-body WECs. In [8] and [9], a special formulation of the optimal MPC problem which allows the application of MPC without a reference trajectory is applied to maximize the energy extracted from ocean waves subject to machinery constraints of a two-body heaving WEC.…”

Decentralized Model Predictive Control for Wave Energy Converter Arrays

“…Moreover, their MPC approaches utilize an available optimal velocity trajectory, which can be calculated for one-body WECs. In [10] and [11], a special formulation of the optimal MPC problem, which allows the application of MPC without a reference trajectory, is applied to maximize the energy extracted from ocean waves subject to machinery constraints of a two-body heaving WEC.…”