Simulation Study on the Performance of Hydraulic Power Take-off System of Wave Energy Conversion Based on the Volumetric Regulation and Energy-storage Principle
A novel hydraulic power take-off(PTO)system based on the volumetric regulation and energy-storage principle is proposed to improve the performance of the hydraulic-type wave energy converters(WECs).In the novel hydraulic PTO system,the hydraulic transformer is adopted to regulate system pressure and flowrate.A point-absorber WEC is focused on here,and the hydrodynamic model of the floater and the nonlinear model of the hydraulic PTO system are presented.Through the simulation of the interaction between the wave and the hydraulic PTO system in the frequency range of 0.3-2 rad/s,the dynamic response of the PTO system and the influence of wave frequency on the dynamic-response and energy-conversion characteristics are investigated.Results show that the cylinder chamber pressure and the hydraulic PTO force resemble an approximately square wave variation,and high frequent fluctuation is occurred.As wave frequency increases,the relative latching duration of the hydraulic cylinder decreases,while the relative energy-capture duration increases.The displacement amplitude of the hydraulic piston and the peak-to-average captured power ratio of the hydraulic cylinder decrease,while the hydraulic PTO force,the average flowrate and rotational speed of the hydraulic motor,the captured power of the hydraulic cylinder and the output power of the hydraulic motor increase first and then decrease.The energy-conversion efficiency of the hydraulic PTO system decreases first and then increases with the increasing wave frequency,and it can reach a value more than 80％,which is larger than that of a constant-pressure type hydraulic PTO system.
万方数据
维普
