Analysis of high-efficiency field modulated multi-phase linear generator for wave power generation

Abstract

With the increasing severity of energy shortages and environmental concerns, wave energy, as a clean and renewable resource, has become a global research focus. However, offshore wave energy is characterized by low operating speed and frequency, which brings significant challenges to wave energy generators, including large volume, low power density, low conversion efficiency, and pronounced detent force fluctuations. To overcome these limitations, this paper proposes a novel high-efficiency field-modulated multiphase double-sided linear generator (HFMMDLG), which achieves both high power density and reduced detent force ripple. Unlike traditional three-phase field-modulated permanent magnet linear generator (TTFMLG), the HFMMDLG employs a bilateral five-phase configuration and incorporates a salient permanent magnet flux-linkage structure in the secondary. Furthermore, the integration of a magnetically assisted rotor with the secondary armature not only reduces the generator volume and detent force ripple but also enhances magnetic field modulation, conversion efficiency, and fault tolerance. Based on the principle of magnetic field modulation, the topology of the proposed generator was designed, and its operating mechanism was analyzed. Finite element models of both the HFMMDLG and the TTFMLG were established to comparatively evaluate their electromagnetic performance, power density, conversion efficiency, and detent force characteristics. The results demonstrate that the no-load induced electromotive force (EMF) of the HFMMDLG increases from 61.23 V in the conventional TTFMLG to 108.43 V, representing a 77% improvement. The output power density is enhanced by a factor of 5.3, and the conversion efficiency is improved from 88% to 96.31%, corresponding to an 8.4% increase. Meanwhile, detent force ripple is significantly reduced, resulting in smoother generator operation. Therefore, the proposed generator effectively enhances power density and conversion efficiency, mitigates detent force fluctuations, and improves operational stability, offering a promising solution for the development of next-generation wave energy linear generators.