Short-term Prediction of Output Power and Constrained Optimal Control for Point-Absorber Type Wave-Energy Converters with Linear Generators

Abstract

This paper addresses the issue of a control subject to physical constraints, involving an energy maximization for wave energy converters with a linear generator. Previous approaches to this problem including model predictive control (MPC) have currently some challenges. The conventional control methods, on the other hand, to be able to estimate the performance of wave energy converters are required in practice. In this study, casual constrained optimal control based on the short-term prediction method is proposed. A novel short-term prediction method of both satisfying with maximum output-power and limited heave amplitudes using the energy spectrum method is shown in this paper. Maximizing estimated output power subject to making the estimated amplitude smaller than motion limitation realizes maximizing output power under the heave-motion limitation. To confirm the accuracy of the short-term prediction method and the performance of the proposed control method, the output power is compared with the output power obtained from other control methods through the frequency and time domain simulations in irregular waves. The results show that the short-term prediction method is useful, and the proposed method can maximize output power under the heave-motion limitation.