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Abstract
A causal control strategy is developed to tackle the noncausality arising in the realtime 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 noncausality. 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 takeoff mechanical force with the PID control. The efficiency of the proposed causal control strategy is assessed for a heaving pointabsorber, in a set of random wave conditions. Generally, the heaving pointabsorber 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 broadbanded sea state, the control efficiency is still within an acceptable level (above 70%).
Original language  English 

Article number  117881 
Number of pages  11 
Journal  Energy 
Volume  204 
Early online date  18 May 2020 
DOIs  
Publication status  Published  1 Aug 2020 
Keywords
 complexconjugate control
 noncausality
 realtime 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 2018 → 1 Sep 2018Activity: Visiting an external institution types › Visiting an external academic institution