Maximum wave power absorption by a control strategy through combining hydraulic cylinders

Hydraulic power conversion system is widely used as a power take-off system in wave energy converters to realize the aim that transforms wave energy into hydraulic energy. The efficiency of transformation is an interesting research topic which attracts many researchers' attention. In this paper, a control strategy through combining hydraulic cylinders is proposed for improving the efficiency of transformation by using sets of control valves to control each chamber of the hydraulic cylinders connecting with the high or low accumulator. Thus a series of effective combinations of the areas of the hydraulic cylinders can be yielded to match with the optimum control moment, which makes the hydraulic cylinders work with higher capacity in each period. For validating the results of the proposed control strategy, a number of simulation models for the hydraulic power conversion system of wave energy converters with and without the control strategy through combining hydraulic cylinders are simulated in AMESim and MATLAB software. The results show that the hydraulic power transformed from the incident wave via the hydraulic power conversion system with the control strategy through combining hydraulic cylinders is at least 27% higher than that via the hydraulic power conversion system without the control strategy through combining hydraulic cylinders. This indicates that the control strategy through combining hydraulic cylinders proposed in this paper can be used to improve the efficiency of transformation in wave energy converters.