Structural modelling and optimisation of direct-driven electrical generators for offshore renewable energy converters
Year: 2025
Type: dissertation
Abstract: In the current phase of offshore wind energy development, reliability is a principal focus. Direct-Drive (DD) systems have a reputation for increased reliability over geared systems, as eliminating the gearbox means fewer moving parts. To produce the same output at low-speed operation however, vast electromagnetic forces are required, necessitating large supporting structures to resist closure of the airgap. This results in a costlier generator and cascading supporting structure costs. Optimisation of generator structures has therefore become an essential area of research for large-scale DD machines. As turbine sizes increase, the extent of influence that forces within and outwith DD generators have on their integrity becomes less certain. A thorough understanding of the loads at play is the key to safely unlocking mass savings from its structure. Accordingly, this thesis furthers the understanding of the loads that large-scale Permanent Magnet DD (PMDD) generators are subject to in operation, firstly by establishing the impact of operating temperature on the integrity of the PMDD generator and exploring methods of alleviating stresses and deformation arising from thermal forces. To that end, several steady-state computational simulations are developed. Secondly, this thesis aims to establish the influence of aerodynamic blade loading on large-scale DD generator structures by its transmission from the rotor to the generator. A transient full-turbine simulation is developed to model behaviour under realistic operating conditions, so that blade loading data can be obtained and applied to a corresponding simplified drivetrain structure model, likewise developed expressly for this purpose. Several PMDD generator structural optimisations incorporating aerodynamic and thermal loads are presented in this thesis, with the resulting geometries analysed for their environmental and financial impacts. This thesis provides new insights into the impact of both direct and indirect loads on the integrity of direct-drive generator structures, enhancing our understanding of how these loads manifest and the potential to mitigate their effects. The methods and tools this thesis present, provide effective and efficient means to conduct further research, paving the way for future studies.
Author: Bichan, Magnus Ross
Institution: Edinburgh Napier University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7104382933
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