Development of an Onshore BenchTest System for a Wave Energy Converter and Verification of a Real-Time OptimalControl

Abstract

The onshore bench test system consisting of two linear shaft motors is produced to emulate the wave energy converter (WEC) motion in waves, control force, and power generation under different control strategies. Two conventional control strategies, the resistive load control (RL)and the approximate complex-conjugate control with considering the copper loss (ACL), and an optimal control strategy, that is, the nonlinear model predictive control (NMPC), were implemented to the onshore bench test system. The measured motion of the test system, control force, and power generation are good agreement with the calculated ones in the simulated regular waves conditions. In the simulated irregular waves conditions, the measured motion of the system and control force are reasonably consistent with the calculated ones. The NMPC is able to finish the optimal calculations less than 50 ms in the tested cases in this paper. It is confirmed from the onshore bench tests that the calculation iteration number of the NMPC increased as the control input was approaching to the input constraints.