Parameter analysis and dual-objective optimization of the hydraulic power take-off system of a floating wind-wave hybrid system

The hydraulic power take-off (PTO) system of wave energy converter (WEC) is a key component of the floating wind-wave hybrid system. It has a notable influence not only on the overall power performance, but also on the motion response which represents wave stability and survivability. Its parameter analysis and optimization is essential, but is ignored in the previous studies. For this reason, this study established a fully-coupled mathematical model of the hybrid system with a complete hydraulic PTO system. Sensitive analysis of 6 hydraulic parameters on the power absorption and pitch motion of the hybrid system are conducted. A surrogate model based on elliptical basis functions neural network (EBFNN) is established to meet the computing needs. The optimization of hydraulic parameters is conducted by the NSGA-II multi-objective optimization algorithm with dual objectives: maximum power absorption and minimum pitch motion. The results show that 6 parameters has an interaction effect between each other. The throttle valve port flow area has the most significant effect on the power absorption, and the pre-charged volume of the accumulator has the most significant effect on the motion response. Four groups of optimal parameter values are recommended to provide reference for system design.