Maximization of wave power extraction of a heave point absorber with a sea-state-based causal control algorithm

Liang Li, Zhen Gao

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

A causal control strategy is developed to tackle the non-causality arising in the real-time implementation of optimal wave energy control. The proposed control strategy utilizes a causal approximation transfer function to link the current wave force to the desired buoy velocity so as to eliminate the non-causality. An optimum model of the approximation transfer function is derived considering the power density distribution of the local wave spectrum. Based on the optimized approximation transfer function, the desired buoy velocity is achieved by tuning the power take-off mechanical force with the PID control. The efficiency of the proposed causal control strategy is assessed for a heaving point-absorber, in a set of random wave conditions. Generally, the heaving point-absorber could extract wave power up to 90% of the theoretical upper bound using the proposed control strategy. The sensitivity of the proposed control to viscous damping effect due to drag and wave spectrum bandwidth is investigated. Although it is less efficient in broad-banded sea state, the control efficiency is still within an acceptable level (above 70%).

Original languageEnglish
Article number117881
Number of pages11
JournalEnergy
Volume204
Early online date18 May 2020
DOIs
Publication statusPublished - 1 Aug 2020

Keywords

  • complex-conjugate control
  • non-causality
  • real-time implementation
  • transfer function
  • wave energy converter
  • wave power extraction

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  • Activities

    • 1 Visiting an external academic institution

    Norwegian University of Science and Technology (NTNU)

    Liang Li (Visiting researcher)

    1 Jul 20181 Sep 2018

    Activity: Visiting an external institution typesVisiting an external academic institution

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