Chunyuan Liu

Research on a Tubular Primary Permanent-Magnet Linear Generator for Wave Energy Conversions

A tubular primary-permanent magnet linear generator (TPPMLG), where both the magnets and armature windings are placed in the primary, is proposed for the sea-wave energy conversion. There is a simple structure on the secondary of the generator. Based on the model of proposed TPPMLG, the operation principle is analyzed. To investigate the electromagnetic characteristics and the unique advantages of the proposed generator, an optimized tubular secondary permanent-magnet linear generator (TSPMLG) is compared with the TPPMLG. Axisymmetrical dimensional finite-element method (FEM) is implemented to calculate the magnetic fields of the two generators and obtain the nonload and load performance. The results of finite-element analysis (FEA) indicate that the proposed generator has the advantages of sinusoidal voltage, minor detent force, high generating efficiency, and good performance at lower speed. Two prototypes are used to validate the results of FEA.

Detent Force Reduction in Permanent Magnet Tubular Linear Generator for Direct-Driver Wave Energy Conversion

In this paper, a quasi-Halbach magnetization structure of permanent magnet tubular linear generator (PMTLG) with bulged stators and auxiliary slots is proposed to reduce the detent force. In the meantime, the detent force for the structure of 9 PM poles 10 winding slots and the conventional one of 8 PM poles 12 winding slots is compared by using Fourier analysis and finite element analysis (FEA). The theoretical and FEA show that 87.18% detent force can be removed through changing the length of the bulged stator. Finally, a prototype is manufactured to verify that the detent force can be reduced efficiently by applying this method.

Cogging Force Reduction of Double-Sided Linear Flux-Switching Permanent Magnet Machine for Direct Drives

This study proposes a double-sided linear flux-switching permanent magnet machine for direct drives in precision servo applications. The method of asymmetry distribution of stator teeth (ADST) is introduced to reduce the cogging force. Moreover, cogging force, back-EMFs, and thrust force are calculated by using finite element analysis. In addition, the performance comparison is carried out to verify the accuracy and effectiveness of the method of cogging force reduction. Finally, the experiment confirms the reasonability and feasibility of the ADST method.

A permanent magnet tubular linear generator for wave energy conversion

A novel three-phase permanent magnet tubular linear generator (PMTLG) with Halbach array is proposed for the sea wave energy conversion. Non-linear axi-symmetrical finite element method (FEM) is implemented to calculate the magnetic fields along air-gap for different Halbach arrays of PMTLGs. The PMTLG characteristics are analyzed and the simulation results are validated by the experiment. An assistant tooth is implemented to greatly minimize the end and cogging effects which cause the oscillatory detent force.

Research on a direct-drive wave energy converter using an Outer-PM linear tubular generator

An Outer-PM tubular linear generator has been designed to increase the power density and distance of relative movement. The design of the two buoys has been completed. Detailed design process of the proposed generator is described. Considering the cogging force and voltage, the linear generator has been optimized and final parameters have been determined. The integrated wave converter system has been manufactured and put into Chinas Yellow Sea based on the design results. The measured voltage is highly consistent with the simulation data. All the results show that the proposed generator is well suitable for wave energy conversion.

Design and Analysis of a Linear Hybrid Excitation Flux-Switching Generator for Direct Drive Wave Energy Converters

Linear generators have the advantage of a simple structure of the secondary, which is suitable for the application of wave energy conversion. Based on the vernier hybrid machines (VHMs), widely used for direct drive wave energy converters, this paper proposes a novel hybrid excitation flux-switching generator (LHEFSG), which can effectively improve the performance of this kind of generators. DC hybrid excitation windings and multitooth structure were used in the proposed generator to increase the magnetic energy and overcome the disadvantages of easily irreversible demagnetization of VHMs. Firstly, the operation principle and structure of the proposed generator are introduced. Secondly, by using the finite element method, the no-load performance of the proposed generator is analyzed and composed with ones of conventional VHM. In addition, the on-load performance of the proposed generator is obtained by finite element analysis (FEA). A dislocation of pole alignments method is implemented to reduce the cogging force. Lastly, a prototype of the linear flux-switching generator is used to verify the correctness of FEA results. All the results validate that the proposed generator has better performance than its counterparts.

Design and optimization of a field-modulating permanent magnet tubular linear generator for direct-drive wave energy conversion

A double buoy power generation system using the field-modulating tubular linear permanent magnet generator (FMTLPMG) is proposed for wave energy conversion in this paper. Ocean wave theory is adopted to analyze the double buoys hydrodynamic problems and calculate the relative velocity. The traditional linear generator has disadvantages of big weight and low power density caused by the slow ocean wave speed. The FMTLPMG proposed in this paper can overcome these disadvantages in some extent by accelerating the speed of the traveling magnetic field. The key characteristics of the FMTLPMG are analyzed with a finite element analysis. Finally, the comparative experiments verify the simulation results.