Optimization and Performance Evaluation of Non-Overlap Wound-Field Converter-Fed and Direct-Grid Wind Generators

Abstract

Non-overlap winding technology continues to remain relevant in the design of wound-field machines as an alternative for high torque density permanent magnet machines. In this paper, the finite element analyses-optimisation of two variants of the non-overlap wound-field machines viz., wound-field flux switching machine (WF-FSM) and phase shifting wound rotor synchronous machine (WRSM), are compared, first in terms of their performance for large-scale converter-fed wind generator drives, then experimentally as sub-scaled converter-fed versus direct grid-connected wind generators, respectively. This study is unique because there are no prior attempts to design, optimize and analyse on these machines for medium-speed wind power generation, as well as experiment on sub-scale prototypes for direct-grid and converter-fed operation. All investigations are contemplated in the medium-speed wind generator drivetrain which provides a tradeoff for generator efficiency and size. From the global optimisation of both machines at large-scale power levels, the torque per mass of the WF-FSM is found to be 50 % lesser compared to the WRSM. This is due to approximate volume, with closely matched optimal split and aspect ratios. In terms of the sub-scaled experimentation, both generators can easily vary their generated output power to match with varying wind resource, but direct grid-connected WRSM generator yields better efficiency performance compared to the WF-FSM converter-fed operating mode, given that the generator terminal voltage of the former is highly regulated.INDEX TERMS converter-fed, direct grid-connected, finite element analyses, non-overlap winding, optimisation, medium-speed wind generators, wound-field flux switching machine (WF-FSM), wound rotor synchronous machine (WRSM).

Advancements in Flux Switching Machine Optimization: Applications and Future Prospects

“…In [60], a combination of finite element analysis-based optimization and experimental testing was employed to evaluate two unique nonconventional, nonoverlapping FSM designs for medium-speed wind generator drivetrains. This study focuses on large-scale applications and sub-scaled power levels.…”

“…Similarly, studies have shown that the power factor of an FSM can be enhanced by reducing the leakage flux and modifying the phase-phase axial separation [83]. Other techniques for enhancing the power factor in FSM were investigated in [3], [60], [84], and [85].…”

Non-Conventional, Non-Permanent Magnet Wind Generator Candidates

“…The WRSM with a nonclassical non-overlap winding is designed, optimised and compared to the WF-FSM at 3 MW geared medium-speed wind power generation. In reference [109], a comparative study on the WF-FSM with another non-conventional wound-rotor synchronous machine (WRSM) for wind generator application was undertaken. The WRSM with a nonclassical non-overlap winding is designed, optimised and compared to the WF-FSM at 3 MW geared medium-speed wind power generation.…”

Investigation of LVRT capability of wind driven dual excited synchronous generator

“…The DESG can operate in low-speed wind applications with a low gearbox ratio because of its capacity to be designed with a high number of poles (D’Arco et al, 2011). In Garner et al (2022) the finite element analyses-optimization of two variants of the non-overlap wound-field machines; wound-field flux switching machine (WF-FSM) and DESG; for wind generator drives, are compared. From the overall optimization of both machines, the torque per mass of the DESG is found to be double of the WF-FSM and direct grid-connected DESG generator gives better efficiency performance compared to the WF-FSM.…”