Fault modelling and analysis of permanent magnet machines for offshore wind power application

Wind energy, as one of the most promising renewable energy sources, has been well developed in the past 30 years. However, the improvement in reliability and availability of wind turbine systems is still an important topic to both academia and industry due to the high operation and maintenance cost. As two of the key components of a wind turbine system, the wind generator and gearbox, have the longest downtime although they are less prone to failure than the power converters and their associated control units. Therefore, it is necessary to study the faults of wind generators and try to reduce their downtime by detecting their faults at an early stage and then implementing effective maintenance. Among all the faults of these wind generators, the winding fault, as the second most frequent fault, has attracted significant interest. It has been reported by the Electrical Apparatus Service Association (EASA) that there are five major winding faults, namely (1) inter-turn (turn-to-turn) short circuit (ITSC), (2) coil-to-coil short circuit, (3) open circuit of one phase, (4) phase-to-phase short circuit, and (5) coil-to-ground short circuit. Amongst all the faults, the ITSC fault, often regarded as one of the root causes of other winding faults, has attracted increasing attention from researchers over the last few years. This thesis will mainly focus on modelling and analysis of permanent magnet machines under ITSC fault for wind power application.