Energy Maximisation Control for an Array of Wave Energy Converters - A Distributed Approach

Wave Energy Converters (WECs) deployed in an array can reduce investment and operational costs, such as infrastructures, operations, and maintenance. Control for WEC arrays becomes more complex due to the dynamic behaviour of individual WECs and the interactions between neighbouring devices, including their defective and radiating effects, which impact the overall system performance. This paper investigates nonlinear model predictive control (NMPC) approaches for controlling an array of wave energy converters (WECs) to extract the maximum amount of energy while respecting safety constraints. Three schemes are benchmarked, namely: (i) Centralised NMPC, where the array is considered as an augmented system; (ii) Independent NMPC, where each WEC is considered independently, neglecting all interactive effects; and (iii) Distributed NMPC (D-NMPC), where a WEC only considers the interactive effects of its nearest neighbour. The proposed approaches are demonstrated and bench-marked through comparative simulation studies based on an array of homogeneous point absorbers. Simulation results highlight the limitations of the independent and centralised approaches and reveal the potential of D-NMPC in achieving most of the performance of C-NMPC, with a computational burden similar in scale to D-NMPC.