Study On Energy Capture And Motion Suppression Effect Of Hydraulic PTO System In A Floating Wind-Wave Hybrid Unit

Along with the rapid development of economy and society,the development and utilization of renewable energy,especially marine renewable energy,is considered an effective way to solve the imminent energy and environmental problems.Among the various types of marine renewable energy,offshore wind and wave energy are similar in origin and distribution,and their respective pain points are complementary,which have great potential for joint development.The floating wind-wave hybrid system combines the advantages of offshore wind and wave energy in resources and costs,in line with the future development trend,and becomes a key research object in the field of wind-wave co-development.As one of the key components of wind-wave hybrid system.the hydraulic PTO system has an important effect on the energy conversion and motion response of the unit.Therefore.to clarify the mechanism and law of the hydraulic PTO system on the operating characteristics of the wind-wave hybrid system.are of great significance for the design and operation of the hybrid system.In this paper,the hydraulic PTO system of a floating wind-wave hybrid system is taken as the research object,the influence of hydraulic PTO parameters on energy conversion and motion response is explored,several key parameters are selected and optimized,and the effect of variable-damping hydraulic PTO system is studied simultaneously.Firstly.the background of the research field is introduced.A brief review of offshore wind and wave energy is presented along with their co-development technologies,and the major progresses in the field of floating wind-wave hybrid system are summarized,leading to the origin and research content of this paper.Secondly,the kinetic equation of the floating wind-wave hybrid system are analyzed,and a fully-coupled numerical simulation framework is built in Simulink.The calculation results are then compared with authoritative commercial software to verify the accuracy of the numerical simulation framework.Thirdly,the preliminary design of the floating wind-wave hybrid system is carried out.Six hydraulic PTO parameters of piston area,accumulator pre-charged gas volume,accumulator pre-charged gas pressure,orifice size,hydraulic motor displacement and generator equivalent damping coefficient were selected as the research objects.The influence of each parameter on the wave energy capture width ratio and pitch motion amplitude response operator was analyzed qualitatively based on the principle of control variables.Subsequently,by means of experimental design and regression analysis,the influence of each hydraulic PTO parameter on the performance of the wind-wave hybrid system is clarified.Based on the above results,four key design parameters were selected and optimized by using the agent model technique and multi-objective optimization algorithm.Several sets of design schemes that can simultaneously consider wave energy conversion and motion response performance are provided as reference.In addition,the technology of variable damping PTO system is briefly reviewed.and a variable damping method for the wind-wave hybrid system is proposed.Based on different sea conditions and hybrid system,the effects of variable damping hydraulic PTO system are explored in terms of average wave energy output power,average pitch angle.maximum pitch angle and wind power,and the quantitative comparison of the gain is conducted simultaneously.Finally.the conlusions are summarized,and the research prospect is prospected.