Study On The Hydraulic Power Take-off Of A Hybrid Wave Energy Converter

The long-term,continuous and multi-dimensional marine environment data is the basis of understanding,developing,utilizing and protecting the ocean.Underwater wireless sensor network is one of the important means to realize ocean data acquisition.Underwater wireless sensor network node is the basic unit of underwater sensor network,which plays many functions of data acquisition,data storage,acoustic communication and networking.In this paper,the design and sea test of the underwater sensor network nodes with battery power supply are carried out.In view of the shortcomings of the nodes in the experiment,an energy alternative scheme based on the energy supply of the hybrid wave energy generation device is proposed,to achieve long-term continuous underwater work and real-time data transmission function.Firstly,this paper introduces the sea trail and we measured the flow field in the target sea with the help of node.The sea trail results show that the design scheme and the flow field inversion method are feasible.In order to optimize the function of the node further,an energy alternative scheme based on wave energy is proposed.The energy alternative provides energy to the node through the motion of the floating body under waves,and on the other hand,the floating body can communicate with the satellite to transmit the data acquired by the underwater node to the shore base in real time.Then,under the condition of linear damping,the mechanism of power generation and the conditions to achieve the optimal energy capture are studied.The results show that the device can achieve the best energy capture state when the frequency matching and damping match are satisfied.By means of finite element analysis,the natural frequency and mode shape of the buoy body are calculated.The results show that the energy capture efficiency can be improved by changing the physical parameters of the device,but the effect is not satisfactory.The size if the device will become very large if the frequency matching is fully satisfied,that is not realistic in the engineering realization.Furthermore,the performance of the hydraulic power take-off system of the hybrid wave energy converter is studied emphatically by means of numerical calculation,and the parameters of the important component accumulator are optimized.The results show that the actual hydraulic power take-off system is a nonlinear variable,and the hydraulic power take-off system shows a good performance of stabilizing the pressure.The parameters of the accumulator like volume,preloading pressure,series-parallel connection,etc.have an important impact on the performance of hydraulic power take-off system and the output power.Finally,a variable damping control strategy based on partial cylinder bypass is proposed,and the numerical simulation is used to validate the control effect in low sea condition and period.The results show that the variable damping control strategy with partial cylinder bypass is useful to enhance the adaptability of sea conditions and improve the energy capture power.