Structure Optimization And Magnetic Circuit Analysis Of Point Absorption Direct-Drive Wave Energy Conversion Device

The fossil energy crisis is getting more and more serious,and it also brings serious pollution problems,and all countries in the world have put forward new requirements for " strategy of sustainable development".During the 75 th session of the United Nations General Assembly,China made an official proposal to take responsibility and make efforts to reach the carbon peak by 2030 and achieve carbon neutrality by 2060.Clean energy is undoubtedly an important means to achieve these goals,and the development and utilization of clean energy has become a common research topic for all countries in the world.Ocean wave energy,as a member of clean energy,is a kind of renewable energy with abundant reserves.The substance offers benefits such as a high concentration of energy and a powerful regularity,and it is mainly found in coastal regions such as the South China Sea and the East Taiwan Sea.Out of the many different types of devices that can convert wave energy,the direct-drive wave energy conversion device that utilizes point absorption stands out due to its simple structure,high efficiency in converting energy,ease of installation,and fewer instances of energy conversion.Because of these advantages,it can potentially satisfy the energy needs of small offshore buoy systems and has significant potential for commercial research.In this paper,the point absorption direct-drive wave energy conversion device will be used as an optimization model,and its overall structure will be divided into functional components according to the energy conversion path.Through finite element simulation and magnetic circuit analysis of the point absorption direct-drive wave energy conversion device,and using orthogonal test method and polar difference analysis,the float capture width ratio and float resonance frequency are combined to study.Based on the frequency domain conditions,the float capture energy characteristics under the joint action of multiple factors are studied to explore the optimization direction of detent force,while two sets of optimization models are designed to maximize the linear generator output power and minimize the detent force.In the analysis of the energy capture characteristics of floats,the float shape,the maximum radius of the float and the float draft depth are clearly considered as the influencing factors of the float capture width ratio through the establishment of the float wave liquid surface hydrodynamic model.To construct the orthogonal level table,four fundamental float shapes were used: conical,dome-shaped,spherical,and cylindrical.These shapes were analyzed using ANSYS-AQWA finite element simulation software to determine radiation diffraction.The results of the orthogonal test were then analyzed to calculate the polar differences,and the degree to which different factors affected the float capture width ratio was determined.In this paper,the float shape has the greatest influence on the float capture width ratio and resonance frequency,followed by the float draught depth,and the float maximum radius has the least influence on the float capture width ratio.The float capture width ratio has a large correlation with the float resonance frequency,but the maximum float capture width ratio is not necessarily at the float resonance frequency point;the more "lean and tall" float shape has a larger capture width ratio and amplitude response operator and lower resonance frequency under higher draught conditions.In the investigation of the optimization direction of the detent force of the linear generator,the stator side tooth height,tooth width and air gap height are clearly considered as the influencing factors of the detent force and output power through the magnetic circuit analysis.Through the combination of ANSYS-MAXWELL electromagnetic simulation and orthogonal test,this paper obtains the degree of influence of different factors on the detent force and output power,among which the edge tooth height has the greatest influence,the air gap height is the second,and the edge tooth width has the least influence.In the two sets of optimization models designed with output power maximization and detent force minimization,if power maximization is taken as the optimization objective,the average value of generator power increases by about 102.9% and the average value of detent force increases by about 46.3%;if detent force minimization is taken as the optimization objective,the average value of generator detent force decreases by about 66.5% and the average value of power decreases by about 70.6%,i.e.,power and detent force are roughly positively correlated.Therefore a set of structural parameters with smaller detent force should be found for a better output power of the linear generator.Lastly,tests are performed on the initial version of the linear generator to enhance the dependability of the finite element simulation outcomes and the validity of the corresponding conclusions.The conclusions drawn in this paper offer a useful reference for future optimization studies of point absorption direct-drive wave energy conversion devices,and also contribute towards their commercialization strategy.