Investigation on PTO control of a Combined Axisymmetric Buoy-WEC(CAB-WEC)

The Combined Axisymmetric Buoy (CAB), a vertical axisymmetric buoy, has the potential to deliver a high energy absorption power. Considering the CAB-Wave Energy Converters (WEC), in order to achieve higher efficiency, the Power Take Off (PTO) systems, which converts the float motion into energy outp...

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Bibliographic Details
Published in:Ocean engineering 2019-09, Vol.188, p.106245, Article 106245
Main Authors: Kong, Fankai, Su, Weiming, Liu, Hengxu, Collu, Maurizio, Lin, Zi, Chen, Hailong, Zheng, Xiongbo
Format: Article
Language:English
Subjects:
CAB-WEC
Experimental method
Numerical analysis
PTO control
Semi-analytical
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Summary:The Combined Axisymmetric Buoy (CAB), a vertical axisymmetric buoy, has the potential to deliver a high energy absorption power. Considering the CAB-Wave Energy Converters (WEC), in order to achieve higher efficiency, the Power Take Off (PTO) systems, which converts the float motion into energy output, needs to be properly controlled. In this paper, a PTO control method for a CAB-WEC under irregular wave conditions is proposed. Based on the semi-analytical solution obtained in the time domain, a numerical optimization is carried out. The optimal PTO damping coefficients under different wave conditions are obtained, by considering the parameter defined as “capture width ratio”. The expression of the optimal PTO damping coefficient in the frequency domain is derived by an analytical method. Based on the semi-analytical solution of time domain dynamic characteristics and analytical method, a comparison between frequency domain optimization and time domain optimization is presented. In general, the two approaches arrive to very similar conclusions, even if with the time domain methodology a slightly higher capture width ratio is achieved. The experimental results have been used to validate the time domain optimization method and the variation in optimal average capture width ratio results. •A PTO control method for a CAB-WEC under irregular wave conditions is proposed.•The relationship between frequency domain optimization and time domain optimization is obtained.•The optimum time domain PTO damping coefficient of irregular waves are discussed and verified by experiments.
ISSN:0029-8018
1873-5258
DOI:10.1016/j.oceaneng.2019.106245