Maximum power generation of a wave energy converter in a stochastic environment

This article examines the design of optimal feedback controllers for ocean wave energy converters. Typically, controllers for these systems are designed using impedance matching techniques, which are tuned to the dominant frequency of wave motion. However, for realistic sea states, which are stochastic and not particularly narrowband, such tuning techniques can result in significantly sub-optimal performance. Although this can be remedied using well-known broadband impedance matching techniques, such techniques are anticausal, thus requiring that future wave motions be known ahead of time, either through the use of deployed sensors or else through the use of prediction. In this article, we illustrate the derivation of the optimal causal controller for wave energy converter, which requires only the generator velocities to be measured for feedback, and may be found as the solution to a nonstandard LQG optimal control problem. We discuss a comparison of the spectral characteristics for optimal causal and anticausal controllers, and illustrate the manner in which these two controllers' behaviors vary with the effiiciency of the generators used.