A novel double-sided linear generator for wave energy conversion

Abstract

The direct drive point absorber is a robust and efficient system for wave energy harvesting, where the linear generator represents the most complex part of the system. Therefore, its design and optimization are crucial tasks. The tubular shape of a linear generator's magnetic circuit offers better permanent magnet flux encapsulation and reduction in radial forces on the translator due to its symmetry.A double stator topology can improve the power density of the linear tubular machine. Common designs employ a set of aligned stators on each side of a translator with radially magnetized permanent magnets. Such designs require doubling the amount of permanent magnet material and lead to an increase in the cogging force. The design presented in this thesis utilizes a translator with buried axially magnetized magnets and axially shifted positioning of the two stators such that no additional magnetic material, compared to single side machine, is required.In addition to the conservation of magnetic material, a significant improvement in the cogging force occurs in the two phase topology, while the double sided three phase system produces more power at the cost of a small increase in the cogging force.The analytical and the FEM models of the generator are described and their results compared to the experimental results. In general, the experimental results compare favourably with theoretical predictions. However, the experimentally observed permanent magnet flux leakage in the double sided machine is larger than predicted theoretically, which can be justified by the limitations in the prototype fabrication and resulting deviations from the theoretical analysis.ii ACKNOWLEDGEMENTS

Linear electrical generator topologies for direct‐drive marine wave energy conversion‐ an overview

“…The advantages of this type of generator include reduced [18] manufacturing cost, simplicity of installation and maintenance of bearings. To balance the attraction force between the stator and translator, double-sided and multiple-sided structures are preferred [21,22]; however, manufacturing tolerances result in an unbalanced air-gap on either side. Hence, the attraction forces are not totally eliminated and the support structure and bearing system must be designed precisely [20,23].…”

A 10 kW ZVS Integrated Boost Dual Three-Phase Bridge DC–DC Resonant Converter for a Linear Generator-Based Wave-Energy System: Design and Simulation

“…Among these technologies, one of the point-absorber type of devices, called Archimedes wave swing (AWS), is currently the most attractive device [8][9][10]. AWS uses a direct-drive linear generator (LG) to convert its reciprocating motion into electricity [11][12][13][14][15]. The structure and typical waveform of the output voltage of an LG is shown in Figure 1.…”