Research On Key Technologies Of Horizontal Pendulum Wave Energy Converter

Energy is the cornerstone of economic growth and development.With China's economic rise,there have been a boost in demand for traditional fossil energy,having caused many serious environmental pollution problems.Wave energy is a kind of renewable energy in the ocean with characteristics of environmental friendly,abundant reserves and high energy density.It is currently attracting more and more countries around the world.However,the fluctuation of energy input and tough living environment also bring difficulties to the development and application of wave energy converters(WECs).The floating pendulum wave energy device is a basic type of WECs,which has the characteristics of high reliability,simple installation and maintenance.By adapting a hydraulic drive system,the mechanical energy of the floating pendulum are further converted into electrical energy.Multiple such sets of floating pendulum WEC can be arrayed to build a large wave energy power generation field.As a result,the construction cost can be reduced effectively through the sharing of key equipment.In this paper,a mathematical model based on dynamic equation of the floating pendulum is constructed firstly in terms of potential flow theory.Then,combined with the physical model of the hydraulic transmission system,the simulation model of arrayed floating pendulum WEC are built,which can simulate the intact energy flow from the wave input to final electric power output.The key parameters in the simulation model are validated by the wave tank experiment,making the calculated results consistent with the laboratory findings.With the aid of the simulation model,a three-floating pendulum WEC array with a rated power output of 15 kW is designed.In this paper,three factors that affects the overall energy capture efficiency are discussed in detail,which include the outline of floating buoy,water level change leading by tides,and the load of the power take off(PTO).In addition,in this paper the author also discusses the application prospect of the arrayed floating pendulum WEC in the off-grid hybrid energy system through an open sea trial and a simulation model,and finally gives out the suggestions from the economical point of view.The main research content of the paper is summarized as follows:In the first chapter,based on a large number of research literatures,the state-of-art of the research on WEC are discussed.Both the domestic and abroad research progress and achievements of WEC are introduced.Some key technical issues that need to be solved urgently are also given out.In the second chapter,the basic theory of ocean wave is introduced.Based on these theories,the wave-float interaction mechanism and calculation methods under different waves are given out.Finally,the dynamic equations of the floating pendulum are constructed based on the motion equations of the floating pendulum.In the third chapter,a set of Simulink-AMESim co-simulation model is built based on the mathematical model of the floating pendulum and the physical model of hydraulic transmission system,which can realize the complete simulation from wave input to power output.A wave tank experiment was conducted in order to validate key parameters in the simulation model.With the help of this simulation system,a set of three-floating pendulum array WEC with a rated output power of 15 kW was successfully designed.In the fourth chapter,the shape of the floating pendulum is optimized in terms of wave conditions.Then,the effects on energy capture efficiency taking by water level changes are discussed.A novel design of rotating machinery is designed in order to mitigate the negative effects.The comparison simulation results show that,the floating pendulum with the new rotating machinery has higher energy capture efficiency and smaller variation than the traditional floating pendulum in various water levels.In the fifth chapter,based on the Perturbation Observation(P&O)Maximum Power Point Tracking(MPPT)algorithm,an input prediction algorithm is added to compensate for the calculation error caused by the fluctuation of the energy input in irregular wave.The feasibility of adopting horizontal pendulum WEC in a hybrid energy system is discussed in chapter 6.A floating Wind/PV/Wave hybrid energy system was designed and tested in the open sea for 7 days.As the contribution of WEC in the floating platform is small,another off-grid hybrid energy model is built based on the background data of Dongfushan Island,Zhoushan City,Zhejiang Province.The simulation results show that the wave energy device array has a very high application value in off-grid island hybrid energy systems.The seventh chapter summarizes the research work and achievements of this article,and points out the further work content and research direction of this topic in the future.