An external tubular linear permanent magnet generator (ETLPMG) is proposed for direct drive wave energy conversion. ETLPMG with quasi‐Halbach array is larger in the air gap magnetic flux density than the internal and radial magnetisation one. An assistant tooth and fractional slot are implemented to decrease the detent force. The power density of ETLPMG is about 7–8 times for that of the internal one and the efficiency reached 90.03% at 18 Ω condition. The characteristics of the ETLPMG are analysed with a finite element analysis. Finally, a prototype is manufactured to verify the simulation results by some experiment tests.

The conventional linear permanent magnet generator (CLPMG) for direct-drive wave energy conversion (WEC) has experienced many drawbacks that are difficult to overcome such as low power density and bulky system volume. To improve power density, this paper proposes a linear magnetic-geared interior permanent magnet generator (LMGIPMG) with tubular topology, which artfully incorporates a linear magnetic gear into a linear permanent magnet generator. The operating principle of the LMGIPMG is introduced, and a detailed analysis of air gap flux density, thrust force characteristics, and no-load and load performances are presented and discussed by using finite element method. The CLPMG, which produces the same power as the LMGIPMG, has about four times the volume of the latter. A prototype CLPMG is manufactured to verify simulation results against experimental tests. The design method and the operation conditions of LMGIPMG and CLPMG are both consistent; thus, the performance of LMGIPMG meets the operation requirements of the direct-drive WEC.

Permanent-magnet linear synchronous motors (PMLSMs) have been widely used in various industries. However, the inherent detent force of these motors limits their application range, especially in high-precision motion and low-speed systems. In this study, magnetic field similarity (MFS) method and edgy teeth-shape optimization are proposed to reduce the detent force. First, an equivalent model of the PMLSM is established wherein the end effect is initially taken into consideration, and the parameters, such as reluctance, energy, and detent force, are calculated. Second, the principle of the MFS is introduced, and the main parameters that affect the detent force are obtained. The detent force is studied and analyzed using parametric analysis, and the shape of the edgy teeth is optimized by particle swarm optimization. The simulation verifies the correctness and applicability of the proposed method. Finally, a prototype is fabricated and the experimental results verify the validity of the mathematical model and simulation results.

Permanent Magnet Linear Synchronous Generators (PMLSG) has high power density and high efficiency, which is always employed in industrial application field. However, as temperature increases, it is easy to cause demagnetization of the permanent magnet, and the applications of PMLSG is limited. In this paper, a PMLSG is optimized which is used in a low speed power generation system. Firstly, a multi-physical coupling field system is described, and introduced the main factors which affecting the design of the PMLSM. Secondly, a multi-physics optimization method based on Genetic Algorithm (GA) is to improve the power density and efficiency. At the same time reduce the material cost of the generator. The thermal model is established and analysis the losses of PMLSG. The conductive heat transfer coefficient is calculated. Then, a Finite Element Analysis (FEA) model is established, and the electromagnetic properties of PMLSG were analyzed. The results of the electromagnetic field calculation are imported into the transient thermal analysis model by FEA, and the temperature of each part for PMLSG are calculated. Finally, an experimental test platform is built for verifying the correctness of the analysis.

The development and reasonable utilisation of wave energy have great realistic significance for solving environment pollution and energy crisis. A direct‐drive system with no middle conversion devices such as gear and turbine, which has a simple structure and good stability, is widely applied to wave power systems. First, the study analysed the structure of a tubular permanent magnet linear generator. The structure of short primary and long secondary is chosen for wave power systems because of the convenience of installation and higher power density. Then, based on finite‐element analysis, the structure of the generator is optimised by parametric analysis and genetic algorithm. A prototype is manufactured according to the optimised size, and the electromagnetic parameters are measured to verify the accuracy of simulation. Finally, a double floating direct‐drive wave power system is installed in the port of Lian Yungang, China, and the system is tested by still and dynamic water; the results show that the system can effectively convert wave energy into electricity.

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.