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550813 
Journal Article 
Declutching control of a wave energy converter 
Babarit, A; Guglielmi, M; Clement, AH 
2009 
1 
Ocean Engineering
ISSN: 0029-8018
EISSN: 1873-5258 
36 
12-13 
1015-1024 
WOS:000270162500012 
When hydraulic power take off (PTO) is used to convert the mechanical energy of a wave energy converter (WEC) into a more useful form of energy, the PTO force needs to be controlled. Continuous controlled variation of the PTO force can be approximated by a set of discrete values. This can be implemented using either variable displacement pumps or several hydraulic cylinders or several high pressure accumulators with different pressure levels. This pseudo-continuous control could lead to a complex PTO with a lot of components. A simpler way for controlling this hydraulic PTO is declutching control, which consists in switching on and off alternatively the wave energy converter's PTO. This can be achieved practically using a simple by-pass valve. In this paper, the control law of the valve is determined by using the optimal command theory. It is shown that, theoretically when considering a wave activated body type of WEC, declutching control can lead to energy absorption performance at least equivalent to that of pseudo-continuous control. The method is then applied to the case of the SEAREV wave energy converter, and it is shown than declutching control can even lead to a higher energy absorption, both in regular and irregular waves. 
Wave energy converter; Declutching control; Hydraulic power take off; Optimal command