Numerical modelling of control strategies and accumulator effect of a hydraulic power take-off system

Wave energy is a promising new player in the renewable energy field. The exploitable power within the world´s oceans is significant and many developers try to capture it by developing wave energy converter (WEC) concepts. This research focussed on the conversion of the WEC motions into usable electricity by the power take-off system (PTO). Specifically, a hydraulic PTO system with an accumulator as energy buffer was studied. The power absorption was calculated, with implementation of several control strategies to maximize the output. Here, a distinction was made between fast strategies, which alter the control on a wave-by-wave basis, and slow strategies, which apply constant control over longer time windows. Additionally, the effect of the accumulator volume on the power conversion and the system pressure was studied. Results indicated that control strategies positively influence the PTO performance and that the accumulator volume is of major importance in hydraulic PTOs.