Sensitivity Analysis and Optimal Design of a Linear Magnetic Gear for Direct-Drive Wave Energy Conversion

An optimized method for the linear magnetic gear (LMG) is proposed in the present study and the designed LMG is employed in the direct-drive wave power generation system. Conventional methods, such as analytical methods, may be inapplicable. Unlike the conventional motor structures, the proposed LMG has the double air-gap structure, which makes it more difficult for the design optimization. Therefore, a practical and effective method that combines the finite element analysis (FEA) and particle swarm optimization (PSO) is proposed to optimize the LMG. In order to decrease the computational expense of the optimization, main factors are categorized, based the influence on the motor performance. They are categorized into sensitive and non-sensitive parameters in this regard. Then, the FEA–PSO method is used to optimize sensitive parameters. The lower-speed and higher-speed parts of the optimized LMG are connected to the buoy and the secondary parts of the permanent magnet linear generator (PMLG), respectively, so that the wave energy converter is employed in the direct-drive wave power generator system. The present study shows that the proposed LMG method can be applied to adjust the frequency of the secondary motor, equal to or close to the natural frequency of the seawater. Therefore, the proposed method can be employed to obtain the maximum wave power. In order to validate the performance of the optimal design, a prototype is produced and tests are carried out.