| Wave energy in the ocean is a kind of clean energy,which has the advantages of high energy density and abundant reserves.Direct drive wave power generation system adopts linear generator as the energy conversion device,which has the characteristics of simple structure,high energy conversion efficiency and convenient maintenance.In view of the low wave energy density and small wave height in China’s coastal waters,the research of short stroke and small volume permanent magnet linear generator not only meets the needs of the domestic market and national economic development,but also conforms to the national "dual carbon" strategy,the "marine power" strategy and national energy and environmental security development,which has important scientific significance.This thesis takes a short-stroke,small volume permanent magnet linear generator for wave power generation as the research object.Through a combination of theoretical analysis,mathematical modelling,simulation calculations and experimental studies,the scheme design of the linear generator,magnetic circuit topology calculation,the numerical simulation analysis of the power generation characteristics and the experimental verification,and the multi-objective hierarchical optimization method of the generator based on sensitivity analysis have been thoroughly investigated.The main work and research results of the thesis include the following aspects:1.The research status of linear generator for wave power generation is described.The basic structure and working principle of permanent magnet linear generator are introduced;Through analytical calculation and electromagnetic analysis,combined with the technical requirements of the linear generator,the main size parameters of the generator were calculated,and the permanent magnet array and stator winding were designed with some parameters.2.Through the established finite element model of the linear generator,the distribution of the magnetic field in the steady state and the waveform variation of the no-load electric potential in the transient state of the cylindrical permanent magnet linear generator are analysed.The influence of the key structural parameters on the output electric potential of the linear generator is also investigated in depth,laying the foundation for the subsequent study of the dynamic characteristics and multi-objective optimisation design of the linear generator.Finally,a 3-factor,3-level orthogonal test analysis of the linear generator is carried out using the orthogonal design method,and the structural dimensions of the linear generator are initially determined.3.A prototype of a cylindrical permanent magnet linear generator was tested and a related test system was designed.Steady-state and dynamic experimental testing of the prototype on a test stand;The output performance of the prototype is verified by experiments under different strokes and frequencies,and the waveform variation law of the output electromotive force of the linear generator is obtained,and the experimental results have a high degree of consistency with the simulation results.4.Multi-objective optimization design of linear generator by sensitivity stratification method;The optimization objectives,design variables and constraints were determined,and a mathematical model of multi-objective optimization was established.The sensitivity stratification method is used to divide multiple design variables into sensitive layer and insensitive layer,and the design variables of the sensitive layer are optimized by the nondominated ranking genetic algorithm(NSGA-Ⅱ)to obtain the Pareto solution.The optimal solution was also obtained by decision ranking this solution set based on the entropy weight method.For the design variables of the insensitive layer,the optimal model of the linear generator was obtained by optimisation through the single parameter scanning method.Finally,the performance of the generator model before and after optimisation was compared and analysed with desired results. |
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