Validation of Real-Time Nonlinear Model Predictive Control on Point Absorber Type Wave Energy Converter by Tank Test

Real-time implementation of a nonlinear model predictive control (NMPC) for a point absorber type wave energy converter (PAWEC) with a tubular air cored permanent magnet generator is experimentally validated through tank model tests. The control inputs of the NMPC were updated by the differential equation to trace the solution of an associated two-point boundary-value problem. Two conventional control strategies, the resistive load control and the approximate complex-conjugate control with considering the copper loss (ACL), and the NMPC were implemented to the PAWEC model. The floater heave motion, control force of the generator, and power generation characteristics were compared in these control strategies. The power generation performance of the NNPC was the same level of that of the ACL in regular and irregular waves. The sensitivities to the linear viscous damping estimation error and to the wave excitation force estimation error in the NMPC were experimentally evaluated by the tank model tests.