Study Of Energy Conversion Characteristics Of A Three-degree-of-freedom Wave Energy Generation Device

As a kind of renewable energy,wave energy has become the focus of development and research in many countries because of its wide distribution,high energy density and relatively easy to capture.Once wave energy is successfully developed and utilized on a large scale,it can not only effectively alleviate the petrochemical energy crisis,but also reduce the pollution of the earth’s environment.However,due to the randomness and harshness of the wave environment,wave energy power generation devices will encounter problems such as low energy capture efficiency and poor environmental adaptability.In order to effectively alleviate the above problems,this thesis proposes a three degree of freedom wave energy generation device with mechanical rectifier,and studies it from the aspects of working principle,structural design,prototype trial production,mathematical model,simulation model and experimental verification.The research results show that the three degree of freedom wave energy generation device has certain advantages in energy capture efficiency and environmental adaptability.Firstly,this thesis studies the working principle,wave force calculation,engineering design and prototype trial production of the three degree of freedom wave energy power generation device.The device can complete the coupling motion of three degrees of freedom under the cooperation of three modules: energy capture guidance module,heave module and pitch and roll module,so as to realize the energy collection of three degrees of freedom.Combined with the motion state of the device in the wave,through appropriate assumptions,this thesis gives the calculation method of the wave force of the floating body of the device,and transforms the wave force into the global coordinate system through the coordinate system transformation,which lays the foundation for the system modeling part later.Based on the wave force received by the device,the strength of the core parts is checked,and a laboratory prototype is successfully designed and manufactured.Secondly,the mathematical model of three degree of freedom wave energy power generation device is established,and the dynamic equation is analyzed.In this thesis,the motion of three degrees of freedom is discussed respectively,the load force of each degree of freedom is defined,the corresponding modeling method is given,and the characteristics of each degree of freedom are analyzed.Based on this,the coupling dynamic equation of the three degree of freedom wave energy power generation device is established according to the Lagrange equation,the equation is qualitatively analyzed,and its frequency characteristics are predicted.Thirdly,this thesis uses Matlab / Simulink to build the simulation model of the multi degree of freedom coupling system,and analyzes its output characteristics under different excitation periods,different degrees of freedom damping and different wave angle.The simulation results show that the system has five resonance periods,and each degree of freedom of the system will produce different output characteristics under different excitation periods;Only under the corresponding resonant excitation period,changing the corresponding degree of freedom damping will have a great impact on the system output;Under different excitation periods,the system has a unique extreme value of the angle of attack.Finally,the relevant pool experiments are designed and compared with the simulation.The correctness of the simulation model is verified from three aspects: excitation period,damping with different degrees of freedom and wave angle.