| The research and use of energy has been accompanied by human progress and development, with the increase of energy demand of human society, all countries in the world began to actively research for new energy development and utilization. The ocean contains thousands and thousands of new energy, so has been hailed as "blue fields", how to good development and utilize of ocean energy for power generation is one of the most important aspects of the research in the field of new energy around the world. Among ocean generation, wave energy power generation is much more mature. Wave energy is captured by wave turbine, and then drag the generator to produce electric energy. Between the turbine and generator there is a intermediate link such as gear box, in order to improve and steady speed. This device increase the complexity of the system, the investment and maintenance costs, and also has an negative effect on the efficiency of the whole system. Because there is no specialized high efficiency low speed generator for wave energy conversion, so the system exist intermediate link.This paper based on "State oceanic administration renewable energy special funds projects- The research and experiment of flexible direct-drive wheel type wave power generation device".This project adopt direct-drive method, which can reduce the mechanical loss of the system, it can improve the operation efficiency of the whole system, reduce the investment and maintenance costs. But with the method of direct driving, the speed of generator is low, and accompanied by large rotation fluctuation,the design output rotational speed of wave turbine is 100 rpm, in the actual test, get the range of speed from 70 rpm to 120 rpm. At the same time, the energy capture device receives volatile wave energy, so the output mechanical energy of wave turbine also has a large fluctuation. So put forward special requirements when design generator for wave energy conversion system.Base on the project requirements, this paper designed a new type of low speed high efficiency permanent magnet generator, the main characteristics of the generator is it can work at low speed, which rated speed is 100 rpm, and can obtain higher efficiency. When design the new type low speed high efficiency permanent magnet generator, in view of its special working environment and work condition, put forward following design requirements: 1) generator pole pairs should as much as possible, in order to achieve high electrical angular velocity when input mechanical speed is low,for improve the output voltage and achieve the purpose of improve the ability of the generator output. 2) the stator core and rotor core are made silicon steel, in order to reduce iron loss and improve the utilization of stator winding groove area, this design can obtain high current output capacity and reduce the copper loss. 3)optimal design the stator and rotor tooth profile, eliminate the influence of magnetic circuit and reduce the loss caused by harmonic, further improve the efficiency of the generator.4)The new type high efficiency low speed permanent magnet generators will work underwater, so the generator structure should have higher strength, and in this kind of work environment require low heat dissipation.After determine the overall structure, on the basis of given parameter, the basic parameters of permanent magnet synchronous generator is calculated. At the beginning of motor design, researchers usually use equivalent magnetic circuit method to calculate motor basic field, to verify if the design meets the requirements. But as the structure of permanent magnet motor getting complicated, the calculation accuracy of equivalent magnetic circuit method is not enough, and the calculation process is getting complicated. Through numerical calculations can get precise amount of field,the most commonly used method is the finite element method. With the development of numerical calculation and simulation technology, the finite element method for its high standardization calculation process, this calculate method was turned into standardized procedure to solve the problem of engineering field. Ansoft Maxwell is a powerful, accurate calculation, with high degree of modularity electromagnetic field finite element simulation software. Software on the basis of Maxwell differential equations, discretization the solution domain in the form of finite element, finally transform equations into a matrix. According to chapter 2 build motor structuremapping model, and use Maxwell software for finite element analysis.The optimization of permanent magnet synchronous motor has two main objectives, one is maximize the output voltage without changing overall structure size of motor, the second is reduce overall consumption by shape optimization of rotor core or permanent magnet. In order to achieve these two goals, we optimize the structure of motor from two aspects, one is by adjusting the size of permanent magnet then observe the change of output voltage value, find the maximum output voltage and take the size of permanent magnet as the best. Second, through the optimization of shape of the rotor iron core and permanent magnet, observe the relationship between the motor loss and its shape to find the optimal shape. We optimized the permanent magnet size, rotor iron core and permanent magnet shape, by using the parametric design function of Maxwell. After comparative analysis of multiple sets of data we can get the optimal size. On the other hand, rare earth permanent magnet is expensive,the utilization of permanent magnets should take into account when optimize the motor. When the motor is under the condition of rated its efficiency can reach 86.4%.Finally set the model of flexible direct-drive wave energy power generation system in MATLAB, this article only design the hardware parts of system and analyzes its feasibility. Three series of motors will be put on a rotating shaft, according to the size of input wave energy regulate the number of motor access to power converter, make the working condition of system with the changes of input wave energy, improve the efficiency of whole power system. |
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